Papers - UEMORI Takeshi

Crystal plastic homogenization finite element analysis of Ti-6242 alloy subjected to in-plane reverse loading

Takeshi UEMORI, Naoya TADA, Junji SAKAMOTO

Mechanical Engineering Journal   12 ( 2 )   24 - 00340   2025

　More details

Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/mej.24-00340

researchmap

Effect of artificial defect on tensile properties of thin titanium alloy wire Reviewed

Junji SAKAMOTO, Naoya TADA, Takeshi UEMORI, Koyo OISHI

11 ( 6 )   24-00129   2024.12

　More details

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Fracture Morphology of Ti-6Al-4V Thin Wire Under Load-Controlled Fatigue Test

72 ( 3 )   39 - 43   2024.12

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Crystal Grain Rotation during Tensile Test of Polycrystalline Pure Titanium Thin Sheet Based on Surface Height and Crystal Orientation Reviewed

Naoya Tada, Hiroaki Ohashi, Takeshi Uemori, Junji Sakamoto

Journal of Physics: Conference Series   2892   012002   2024.11

　More details

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1742-6596/2892/1/012002

researchmap

Crystal plasticity analysis of fatigue crack initiation site considering crystallographic orientation in Ti–22V–4Al alloy

Jinta Arakawa, Koki Hirazumi, Takeshi Uemori, Yoshito Takemoto

23   2024.9

　More details

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.rineng.2024.102405

researchmap

Method for Predicting Crack Size Using Amplitude Change in Titanium Alloy under Bending Vibration Reviewed

J. Sakamoto, N. Tada, T. Uemori

472   2024.9

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Elucidation of small fatigue crack initiation and propagation behavior on polycrystal Ti-22V-4Al Reviewed

Jinta Arakawa, Koki Hirazumi, Takeshi Uemori, Yoshito Takemoto

Procedia Structural Integrity   66   38 - 48   2024.9

　More details

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.prostr.2024.11.053.

researchmap

Vibration change and crack propagation under bending vibration of aluminum alloy

SAKAMOTO Junji, TADA Naoya, UEMORI Takeshi

Transactions of the JSME (in Japanese)   90 ( 930 )   23-00246 - 23-00246   2024

　More details

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this study, aluminum alloy specimens were subjected to bending vibrations at different vibration frequencies near the first resonance frequency in order to investigate the vibration changes associated with crack propagation. Bending displacement, crack length, and strains at several parts of the specimen were measured during the bending vibration tests. As a result, it was confirmed that when the vibration frequency was lower than the initial first resonance frequency, the vibration amplitude increased with the crack length, and when the vibration frequency was higher than the initial first resonance frequency, the vibration amplitude decreased with an increase in the crack length. This is due to the decrease in the first resonance frequency due to the material damage. The relationship between the change of bending displacement amplitude and the crack length during vibration of the specimens can be organized using the slope (dΔε_x2/df_v) of the relationship between the strain range and the vibration frequency for the undamaged specimen. This might be due to the strong correlation between the decrease in the first resonance frequency and the crack size when the crack initiation location is limited in the material. Moreover, based on the relationship between the change of bending displacement amplitude and the crack length, the stress intensity factor range (ΔK) was estimated by incorporating the load change into the crack length. By using the modified ΔK, the crack growth rate during bending vibration could be predicted.

DOI： 10.1299/transjsme.23-00246

researchmap

Relationship between cyclic tensile properties of cellulose nanofiber reinforced natural rubber and volume fraction of bound rubber obtained from swelling tests

OKUI Kento, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, SAKAKIBARA Keita

Transactions of the JSME (in Japanese)   90 ( 932 )   24-00008 - 24-00008   2024

　More details

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In recent years, environmental concerns have led to a demand for sustainable materials, and natural rubber (NR) reinforced with cellulose nanofibers (CNFs) has been attracting attention as one such material. When CNFs are added to NR, the elastic modulus is greatly improved. This is considered to be caused by deformation constraint of NR by reinforcing CNFs. On the other hand, it is known that there exists a region around reinforcing fibers where the rubber is tightly connected to the surface of fibers, which is called bound rubber. The volume fraction of the bound rubber is usually measured by swelling tests using organic solvent. In this paper, we focused on the relationship between the tensile properties of NR reinforced with CNFs and the volume fraction of bound rubber. Firstly, cyclic tensile tests were performed using plate specimens of CNF-reinforced NR and the effect of reinforcing CNFs on the tensile properties of CNF-reinforced NR and their change with loading cycles were investigated. Then, the swelling tests were conducted for similar specimens and the volume fraction of the bound rubber was evaluated. It was found from a series of experimental results that tensile deformation resistance of NR increased largely by adding 5 phr (4.8 mass%, 3.2 vol.%) of CNFs but that this increase decreased from the second loading cycle. Moreover, a clear relationship was found between the tensile deformation resistance of CNF-reinforced NR and the volume fraction of bound rubber. These results suggest that the tensile deformation resistance of CNF-reinforced NR can be evaluated by swelling tests.

DOI： 10.1299/transjsme.24-00008

researchmap

Prediction of active slip system for commercially pure titanium sheet by crystal plasticity finite element analysis Reviewed

Extended abstract of The Advanced Technology in Experimental Mechanics and International DIC Society Joint Conference 2023 (ATEM-iDICs '23)   19-G05   2023.10

　More details

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Prediction of slip activity of crystal grains around semi-circular and semi-elliptical notches in thin-sheet specimens of pure titanium using formulated macroscopic stress distribution and crystal orientation

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Engineering Failure Analysis   107623 - 107623   2023.9

　More details

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.engfailanal.2023.107623

researchmap

Effect of Surface Roughness and Oxidation Treatment on Joint Strength between Aluminum Alloy and High-Density Polyethylene Reviewed

2023.8

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Tensile properties and slip deformation behavior of pure titanium thin wire with a small diameter-to-grain-size ratio

Junji Sakamoto, Naoya Tada, Takeshi Uemori

Materials Science and Engineering A   863   2023.1

　More details

Publishing type：Research paper (scientific journal)  

To investigate the tensile properties and slip deformation behavior of pure titanium thin wires with a small ratio of the diameter to the grain size, tensile tests and a stepwise tensile test were performed using specimens with a diameter of approximately 170 μm and grain sizes of 17 and 87 μm, corresponding to diameter-to-grain-size ratios of 10 and ∼2, respectively. The specimen with a diameter-to-grain-size ratio of 10 fractured through the growth of voids. The fracture morphology was similar to that of the bulk specimens. On the other hand, for specimens with a diameter-to-grain-size ratio of 2, fracture occurs owing to the local deformation, in which primary slip systems are activated in each grain. The stepwise tensile test of the specimen with a diameter-to-grain-size ratio of 2 indicated that the slip deformation tended to occur from the large grains. Moreover, the activities of the slip systems of grains were evaluated using the Schmid factor (SF) and critical resolved shear stress (CRSS) of each slip system. It was noted that slip systems with the highest SF∙CRSS−1 were activated for 30 out of 33 grains.

DOI： 10.1016/j.msea.2022.144532

Scopus

researchmap

Slip Activity of Crystal Grains around Notch in Thin Sheet Specimen of Pure Titanium

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Books of abstracts, 17th Asia-Pacific Conference on Fracture and Strength and 13th Conference on Structural Integrity and Failure   19 - 19   2022.12

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

複素数階微分法の純チタン板材の結晶塑性解析への適用 Reviewed

上森武, 多田直哉, 坂本惇司

チタン   70 ( 2 )   158 - 163   2022.4

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Effect of resin lamination on tensile strength characteristics of SUS304 stainless steel thin film Reviewed

Junji Sakamoto, Naoya Tada, Takeshi Uemori

International Journal of Advanced Manufacturing Technology   116 ( 3-4 )   1081 - 1088   2021.10

　More details

Language：English   Publishing type：Research paper (scientific journal)  

The objective of this study is to clarify the effect of resin lamination on the tensile strength characteristics of SUS304 stainless steel thin films. We conducted tensile and stepwise tensile tests using several types of specimens prepared with 20-μm- and 40-μm-thick SUS304 films, 25-μm-thick polypropylene (PP) film, and 6-μm-thick polyethylene terephthalate (PET) film. Their macroscopic and microscopic tensile deformation behaviors were observed using an optical microscope and a reflection-configured digital holographic microscope, respectively. As a result, laminating the PP or PET films onto the SUS film did not significantly change the macroscopic and microscopic strain changes against the tensile load or microscopic surface changes in the low-strain region. Laminating the PET film onto the SUS film did not reduce the fracture strain, whereas laminating the PP film onto the SUS film did reduce it. One of the reasons may be that burrs formed on the side surface of the PP/SUS laminate. Polishing the side surface of the PP/SUS laminate may suppress the reduction in its fracture strain. The reduction of the fracture strain due to the PP lamination in the 20 μm thick SUS film was larger than that of the 40-μm-thick SUS film. In thin SUS films, small stress concentrators that have almost no effect on macroscopic and microscopic deformation might significantly reduce the fracture strain.

DOI： 10.1007/s00170-021-07510-8

Scopus

researchmap

Prediction of the fracture location by tensile tests of gray cast iron based on the dimensional changes of graphite flakes Reviewed

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Journal of Pressure Vessel Technology, Transactions of the ASME   143 ( 2 )   2021.4

　More details

Publishing type：Research paper (scientific journal)  

© 2021 American Society of Mechanical Engineers (ASME). All rights reserved. Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high performance-To-cost ratio. On the other hand, weak graphite flakes present in gray cast iron serve as stress concentrators and adversely affect the material strength. Therefore, it is crucial to examine the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, tensile tests on gray cast iron were carried out using a plate specimen and observed by scanning electron microscopy, and the microscopic deformation was observed on the specimen surface. Particularly, the change in the size of graphite flakes during the tensile tests was examined, and the observed trend was discussed. The experimental results reveal that the dimensional changes in the graphite flakes vary in the observed area and that the final fracture occurs in an area where a large dimensional change is observed, suggesting that the fracture location or critical parts of gray cast iron can be predicted from the dimensional changes of the graphite flakes at an early stage of deformation.

DOI： 10.1115/1.4048063

Scopus

researchmap

Effect of Mechanical Surface Treatment and Post-treatment Polishing on Tensile Strength and Fatigue Life of High-speed Tool Steel Reviewed

N.Karunathilaka, N.Tada, T.Uemori, J.Sakamoto, R.Hanamitsu, M.Fujii, Y.Omiya, M.Kawano

2 ( 1 )   35 - 60   2021

　More details

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Finite Element Study of the Effect of Internal Cracks on Surface Profile Change due to Low Loading of Turbine Blade Reviewed

Junji Sakamoto, Naoya Tada, Takeshi Uemori, Hayato Kuniyasu

Applied Sciences   10 ( 14 )   4883 - 4883   2020.7

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Turbine blades for thermal power plants are exposed to severe environments, making it necessary to ensure safety against damage, such as crack formation. A previous method detected internal cracks by applying a small load to a target member. Changes in the surface properties of the material were detected before and after the load using a digital holographic microscope and a digital height correlation method. In this study, this technique was applied in combination with finite element analysis using a 2D and 3D model simulating the turbine blades. Analysis clarified that the change in the surface properties under a small load varied according to the presence or absence of a crack, and elucidated the strain distribution that caused the difference in the change. In addition, analyses of the 2D model considering the material anisotropy and thermal barrier coating were conducted. The difference in the change in the surface properties and strain distribution according to the presence or absence of cracks was elucidated. The difference in the change in the top surface height distribution of the materials with and without a crack was directly proportional to the crack length. As the value was large with respect to the vertical resolution of 0.2 nm of the digital holographic microscope, the change could be detected by the microscope.

DOI： 10.3390/app10144883

Scopus

researchmap

Evaluation of strength of stainless steel bolt without heat treatment considering Bauschinger effect during manufacturing process Reviewed

S. Narita, K. Hayakawa, T. Uemori, Y. Kubota

Journal of Materials Processing Technology   278   116481 - 116481   2020.4

　More details

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmatprotec.2019.116481

Scopus

researchmap

Analysis of the change of direct current potential difference and diameter distribution of thin pure titanium wire subjected to tensile and fatigue loads for fracture prediction Reviewed

Junji SAKAMOTO, Yusuke TAKAGI, Takeshi UEMORI, Naoya TADA

Transactions of the JSME (in Japanese)   86 ( 882 )   19 - 00351   2020.2

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

<p>Pure titanium thin wires have been used for medical fields. It is important to investigate the possibility of non-destructive inspection of pure titanium thin wires for the safety utilization of them. In order to investigate a fracture prediction method for a pure titanium thin wire, we performed tensile and fatigue tests and a finite element analysis to analyze the changes of direct current potential difference and diameter distribution of the pure titanium thin wire during tensile and fatigue tests. It was found that a direct current potential difference method may be available for evaluating the tensile and fatigue damages of the pure titanium thin wire. In the tensile and fatigue tests, the normalized direct current potential difference increased almost linearly with an increase in the nominal strain, and a sign of an increase of the normalized direct current potential difference was observed when the fatigue crack propagated. Therefore, the nondestructive inspection could be conducted by setting a tolerance value of the normalized direct current potential difference, or detecting a sign of an increase in the normalized direct current potential difference. In addition, a method of predicting the fracture location from the diameter distribution change of the pure titanium thin wire was studied. The method could be applied to tensile and fatigue fractures.</p>

DOI： 10.1299/transjsme.19-00351

CiNii Article

researchmap

Microscopic deformation of thin sheet of polycrystalline pure titanium under tension Reviewed

Naoya Tada, Kentaro Kishimoto, Takeshi Uemori, Junji Sakamoto

American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   3   2020

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

Copyright © 2020 ASME. Commercial pure titanium has been widely used in aerospace, chemical, and biomedical industries for its lightweight, high corrosion resistance, high strength, high heat resistance and good biocompatible properties. The market of pure titanium thin sheets is expected to increase in medical, dental, civil engineering, and acoustical engineering fields. On the other hand, pure titanium takes hexagonal closed-pack structure with anisotropic elasticity and plasticity. Inhomogeneous microscopic deformation always occurs by mechanical loading from the elastic condition. The inhomogeneity brings about various damages such as localized plastic deformation, microcracking, necking, and so on. Since the inhomogeneity is significant in thin sheets, it is important to investigate its deformation behavior. In this study, a tensile test was carried out using a thin sheet specimen of polycrystalline pure titanium, and the microscopic deformation of grains was measured by the digital holographic microscope. During the test, the height distribution of grains was measured in a fixed area on the front and back surfaces of the specimen at each tensile load step and the results at different load steps were compared. It was found from the measurement results that inhomogeneous deformation began at the small load due to anisotropic elasticity of crystal grains and expanded with the load by their anisotropic plasticity. Grain heights at grain center and those along grain boundaries were related with each other, and the grain heights on the front surface were inversely correlated with those on the back surface.

DOI： 10.1115/PVP2020-21715

Scopus

researchmap

Slip Deformation of Crystal Grains in Semi-Circular Notched Thin Sheet Specimen of Pure Titanium during Tensile Test Reviewed

Takashi Ishida, Naoya Tada, Takeshi Uemori, Junji Sakamoto

2019.10

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Prediction of Fracture Location in Tensile Test of Short-Fiber-Self-Reinforced Polyethylene Composite Plates Reviewed

Naoya Tada, Ming Jin, Takeshi Uemori, Junji Sakamoto

Volume 3: Design and Analysis   3   2019.7

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Mechanical Engineers  

<title>Abstract</title>
Composite materials such as carbon-fiber-reinforced plastics (CFRP) and glass-fiber-reinforced plastics (GFRP) have been attracting much attention from the viewpoint of lightweight solution of automobiles and airplanes. However, the recyclability of these composite materials is not sufficient and the environmental load is large. Recently, self-reinforced polymer (SRP), in which similar polymer is used for reinforcing fibers and matrix, has been proposed. High-density polyethylene (HDPE) reinforced with ultra-high-molecular-weight polyethylene (UHMWPE) fibers, so-called self-reinforced PE (SRPE), is one of the promising thermoplastic composites. In this study, SRPE plates were made and the tensile tests were carried out. After the effect of reinforcement of UHMWPE fibers was evaluated on the basis of the tensile strength, the relationship between the distribution of UHMWPE fibers and the location of the final fracture line was examined. It was found from these experimental results that the fracture tends to occur along the regions with low area fraction of fibers or along those with low area fraction of fiber/matrix boundaries. This fact suggests that the fracture location of SRPs is predictable from the distribution of reinforcing fibers.

DOI： 10.1115/pvp2019-93546

Scopus

researchmap

Effect of Lubrication and Forging Load on Surface Roughness, Residual Stress, and Deformation of Cold Forging Tools Reviewed

Karunathilaka, Tada, Uemori, Hanamitsu, Fujii, Omiya, Kawano

Metals   9 ( 7 )   783 - 783   2019.7

　More details

Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Cold forging is a metal forming that which uses localized compressive force at room temperature. During the cold forging process, the tool is subjected to extremely high loads and abrasive wear. Lubrication plays an important role in cold forging to improve product quality and tool life by preventing direct metallic contact. Surface roughness and residual stress also greatly affects the service life of a tool. In this study, variations in surface roughness, residual stress, and specimen deformation with the number of cold forging cycles were investigated under different forging conditions. Specimens that were made of heat-treated SKH51 (59–61 HRC), a high-speed tool steel with a polished working surface, were used. The specimens were subjected to an upsetting process. Compressive residual stress, surface roughness, and specimen deformation showed a positive relationship with the number of forging cycles up to a certain limit and became almost constant in most of the forging conditions. A larger change in residual stress and surface roughness was observed at the center of the specimens in all the forging conditions. The effect of the magnitude of the forging load on the above discussed parameters is large when compared to the effect of the lubrication conditions.

DOI： 10.3390/met9070783

Web of Science

researchmap

Crystal Plasticity Finite Element Analysis of Effects of Microscopic Non-Uniform Deformation on Surface Roughness of Pure Titanium Sheet Reviewed

Takeshi UEMORI, Hiroki KAKIHARA, Naoya TADA

Journal of the Society of Materials Science, Japan   68 ( 6 )   478 - 484   2019.6

　More details

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science, Japan  

DOI： 10.2472/jsms.68.478

researchmap

Springback Suppression of AZ31 Magnesium Alloy Sheet in Draw Bending at Elevated Temperature Reviewed

Takashi Katahira, Takeshi Uemori, Tetsuya Yoshida, Michihiro Takiguchi, Tetsuo Naka, Komgrit Lawanwong, Fusahito Yoshida

Key Engineering Materials   Vol.794   127 - 132   2019.2

　More details

researchmap

Microscopic Elastic and Plastic Inhomogeneous Deformations and Height Changes on the Surface of a Polycrystalline Pure-Titanium Plate Specimen under Cyclic Tension Reviewed

Naoya Tada, Takeshi Uemori

Applied Sciences   8 ( 10 )   1907 - 1907   2018.10

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

A cyclic tensile test was carried out using a plate specimen of commercial pure titanium on a digital holographic microscope stage. Microscopic deformation of the grains was observed, and their height distribution was measured on the specimen surface. Each grain showed nanoscopic movement up and down, as well as reverse movement corresponding to specimen loading and unloading. We suggest that the different grain-specific changes in height were caused by microscopic inhomogeneities in the material, such as differences in the crystal orientation and geometries of both the surface and subsurface grains. Changes in grain height increased with tensile load, and a strong relationship was found between the height changes that occurred under elastic and plastic conditions. This suggests that microscopic plastic deformation is predictable from microscopic elastic deformation. In order to investigate the plastic deformation of grains in more detail, slip-line angles were measured after the tensile test. We found slip lines with similar angles in neighboring grains, suggesting that the plastic deformation of grains was not independent, but rather was related to that of surrounding grains and influenced by the deformation of subsurface grains.

DOI： 10.3390/app8101907

researchmap

Cyclic stress and strain responses of AZ31 magnesium alloy sheet metal at elevated temperatures Reviewed

Takeshi Uemori, Takashi Katahira, Tetsuo Naka, Naoya Tada, Fusahito Yoshida

Procedia Manufacturing   15   1792 - 1799   2018

　More details

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Effect of Contact Pressure Applied on Tool Surface during Cold Forging on Fatigue Life of Tool Steel Reviewed

UEMORI Takeshi

Procedia Manufacturing   15   488 - 495   2018

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Dimensional Changes of Graphite Flakes and Fracture in Tensile Tests of Gray Cast Iron Reviewed

Naoya Tada, Takeshi Uemori

Conference papers, ASME 2018 Pressure Vessels & Piping Conference   PVP2018-85214   2018

　More details

researchmap

Elastic and Plastic Microscopic Undulation on the Surface of Polycrystalline Pure Titanium Under Tension Reviewed

Naoya Tada, Takeshi Uemori, Toshiya Nakata

JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME   139 ( 6 )   1180 - 189   2017.12

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME  

Commercial pure titanium has been widely used in the aerospace, chemical, and biomedical industries because of its light weight, high corrosion resistance, high strength, high heat resistance, and good biocompatibility. Pure titanium takes the form of a hexagonal closed-pack structure with anisotropic elasticity and plasticity, with most of its components being polycrystalline aggregates having different crystal orientations. Small mechanical loading under elastic conditions therefore always induces inhomogeneous microscopic deformation, and the resulting inhomogeneity brings about various defects such as inhomogeneous plastic deformation, microcracking, and necking. It is therefore important to investigate the microscopic inhomogeneous deformation under elastic and plastic conditions. In this study, a plate specimen of commercial pure titanium was subjected to a tensile test on the stage of a digital holographic microscope (DHM), and the microscopic deformation of grains in the specimen under elastic and plastic conditions were observed and measured. During the test, the grains' height distribution was measured in a fixed area on the specimen's surface at each tensile loading step, and the correlation between height distributions at different loads was examined. We found from the measurements that each grain shows a different height change even under elastic conditions with a small load. This inhomogeneous height change was enhanced as the load was increased to plastic conditions. A strong correlation between the height changes under elastic and plastic conditions was also found. This result suggests that the microscopic deformation experienced under plastic conditions is predictable from that observed under elastic conditions.

DOI： 10.1115/1.4038012

Web of Science

researchmap

Evaluation of Thin Copper Wire and Lead-Free Solder Joint Strength by Pullout Tests and Wire Surface Observation Reviewed

Naoya Tada, Takuhiro Tanaka, Takeshi Uemori, Toshiya Nakata

Crystals   7 ( 8 )   255 - 255   2017.8

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Copper wires have been attracting much attention for Large Scale Integration (LSI) bonding because of their excellent mechanical and electrical properties, in addition to their low material cost. The ends of these wires are usually joined to pads or through-holes on a printed circuit board, and lead-free soldering is one of the popular bonding methods. Since the deformation resistance of solder is lower than that of copper, especially in slow deformation due to creep, the strain tends to be increased in the solder and concentrated near the copper/solder joint interface. Thus, fracture frequently occurs at this interface and may influence the quality of the product. It is therefore important to evaluate the bonding strength of thin copper wire and lead-free solder. In this paper, pullout tests of thin copper wire from lead-free solder were carried out, and the pullout behavior of the wires was observed. The bonding strength was evaluated based on the actual bonded area on the copper wire surface. Finally, the strength of the thin copper wire/solder joint was summarized using the shear and tensile strengths of the copper/solder interface as well as the tensile strength of the copper wire.

DOI： 10.3390/cryst7080255

Scopus

researchmap

Time-Dependent Fracture of Copper-Cored Lead-Free Solder Ball and Nickel Rod Joints in Air, Distilled Water, and NaCl Solution Reviewed

Naoya Tada, Takeshi Uemori

Proceedings of Technical Papers - International Microsystems, Packaging, Assembly, and Circuits Technology Conference, IMPACT   2017-   319 - 322   2017

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE Computer Society  

Solder joints have been used for electric connections in many electronic devices, and the joints are subjected to mechanical loadings such as static or cyclic tension/compression and shearing under various environments. Since the melting point of solder is very low comparing with the other normal metals, the time-dependent damage accumulation and fracture are often found in the solders even at the room temperature. In this paper, tensile tests of copper-cored lead-free solder ball and nickel rod joints were carried out in air, distilled water, and salt water environments using a unique testing device with permanent magnet. The time-dependent fracture of the joints was investigated from the viewpoint of damage accumulation.

DOI： 10.1109/IMPACT.2017.8255911

Scopus

researchmap

Description of closure of cyclic stress-strain loop and ratcheting based on Y-U model Reviewed

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

Key Engineering Materials   725   351 - 356   2017

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

This paper proposes a cyclic plasticity model to describe the closure of a cyclic stress-strain hysteresis loop based on the Y-U model. In this model, the backstress moves in a cyclic memory surface following a newly proposed kinematic hardening law. For this model just the same Y-U parameters can be used, and no additional material parameters are needed. By using a supplementary rule, this model is also able to describe ratcheting.

DOI： 10.4028/www.scientific.net/KEM.725.351

Scopus

researchmap

Effect of Hardening Rule for Spring Back Behavior of Forging Reviewed

Shinobu Narita, Kunio Hayakawa, Yoshihiro Kubota, Takafumi Harada, Takeshi Uemori

Procedia Engineering   207   167 - 172   2017

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier Ltd  

Geometrical discrepancy between formed part and designed one is one of the major problems for metal forming processes. Spring back behavior is one of the most important factors on the discrepancy, in not only sheet metal forming but also cold forging process. For cold forging process, it is difficult to observe the change in geometry of forgings before and after release of tools/dies, since the workpiece during forging is covered by tools/dies in most cases. Uncertainty remains for the precision on geometrical prediction after spring back of the cold forged part. In the present research, the diameters of extruded shaft at the bottom dead center and after the release of tools/dies were measured to investigate the spring back behavior in the cold forging process. As a result of experiment, the diameter of extruded shaft was increased at the bottom dead center by spring back and decreased after the release by re-extrusion. For these series of change in diameter, FE analyses using isotropic and kinematic hardening models were performed in order to evaluate influence of spring back on the material hardening models in forging process. For kinematic hardening model, Yoshida-Uemori model modified for large strain region was employed. As a result of calculation, both the isotropic and kinematic hardening models showed the similar tendency on the change in diameter with the experimental one.

DOI： 10.1016/j.proeng.2017.10.756

Scopus

researchmap

Theoretical predictions of fracture and springback for high tensile strength steel sheets under stretch bending Reviewed

Takeshi Uemori, Tetsuo Naka, Naoya Tada, Hidenori Yoshimura, Takashi Katahira, Fusahito Yoshida

Procedia Engineering   207   1594 - 1598   2017

　More details

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.proeng.2017.10.1054

Scopus

researchmap

Asymmetric-shaped bending of adhesively bonded sheet metals Reviewed

Taro Tokuda, Takeshi Uemori, Tetsuya Yoshida, Michihiro Takiguchi, Fusahito Yoshida

Key Engineering Materials   725   630 - 635   2017

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

In sheet metal industries, press-formed sheet elements are usually adhesively bonded together at the final stage of assembly. Instead of such a conventional process, the present authors proposed a new technique that first flat sheets are adhesively bonded together and then press-formed into the final products [1]. In previous study, the problem of the die-bending (V-bending and hat-shaped bending) with symmetrical shape has studied. In this study, asymmetric-shaped bending of adhesively bonded sheet metals was investigated by experiments and FEM analysis method. In the case of asymmetric-shaped bending, it was found that the timing of contact from the die corner to the die hypotenuse is early in the press-forming process compared with symmetrical bending (V-bending and hat-shaped bending). For the FEM analysis results, the maximum shear strain in asymmetric-shaped bending was smaller than that in symmetric-shaped bending at the hat-shaped side. Thus, the shape of the die has a large influence on the die-bending of adhesively bonded sheet metals.

DOI： 10.4028/www.scientific.net/KEM.725.630

Scopus

researchmap

Influence of Bauschinger Effect and Anisotropy on Springback of Aluminum Alloy Sheets Reviewed

Takeshi Uemori, Satoshi Sumikawa, Tetsuo Naka, Ninshu Ma, Fusahito Yoshida

MATERIALS TRANSACTIONS   58 ( 6 )   921 - 926   2017

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

For accurate springback calculations, the development of accurate constitutive equation Yoshida-Uemori model must always be taken into account. However, several springback calculations of other sheet metals by Yoshida-Uemori model have shown wrong agreements with the corresponding experimental data. The reason is why most of them have been calculated from the view point of the accuracy of Bauschinger effect without the strong anisotropy of sheet metal. In the present paper, we have investigated how the initial anisotropy affects the amount of springback for aluminum sheet metals with Bauschinger effect. Specifically, hat bending experiments in R.D. and T.D. were compared with the corresponding calculations. From the above mentioned comparisons, we found that the optimum combination of an anisotropic yield functions and Yoshida-Uemori model is very important for accurate springback analysis.

DOI： 10.2320/matertrans.L-M2017812

Web of Science

researchmap

Cracking behavior of thin gold strip deposited on polycarbonate plate under Cyclic and stepwisely-increased tension Reviewed

Naoya Tada, Yafei Hu, Takeshi Uemori, Toshiya Nakata

MATEC Web of Conferences   108   01004 - 01004   2017

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：EDP Sciences  

Thin metal films deposited on polymers have been attracting much attention in flexible electronics. Various combinations of film and polymer substrate are expected to be developed. In this paper, deformation and fracture of thin metal film on polymer substrate was briefly analysed and the influencing factors were summarized. After that, focusing on the shape and thickness of thin metal film on polymer substrate, cracking behavior of small rounded-rectangular thin gold films called "strips" with a thickness less than one micrometer was observed under cyclic and stepwisely-increased trapezoidal tensions. The strips were deposited on a polycarbonate plate specimen, and wide and narrow strips with different thickness were prepared for the tests. The cracking behaviour was successfully observed and the increasing rate of crack number with the load or strain was examined. Since most cracks were initiated from the small defects, the crack initiation behavior was correlated with the distribution of defects.

DOI： 10.1051/matecconf/201710801004

Web of Science

researchmap

Tensile Test of Copper-Cored Lead-Free Solder Joints Using Non-Contact Type Testing Device with Permanent Magnets Reviewed

Naoya Tada, Takeshi Uemori, Toshiya Nakata

SEM Annual 2017 Proceedings   478 - 478   2017

　More details

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Springback analysis of aluminum alloy sheet metals by yoshida-uemori model Reviewed

Takeshi Uemori, Kento Fujii, Toshiya Nakata, Shinobu Narita, Naoya Tada, Tetsuo Naka, Fusahito Yoshida

Key Engineering Materials   725   566 - 571   2017

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

During the last few decades, the enhancement of prediction capability of the sheet metal forming have been increasing dramatically. High accurate yield criteria and wokhardening model (especially, non-linear kinematic hardening model) have a great importance for the prediction of the final shapes of sheet metal. However, the predicted springback accuracy of aluminum alloy sheet metal is not still good due to their complicated plastic deformation behaviors. In the present research, the springback deformation of aluminum alloy sheet metals were investigated by finite element calculation with consideration of initial anisotropy and the Bauschinger effect. In order to examine the effect of the initial and deformation induced anisotropy on the springback deformation, several types of high accurate yield function and hardening rules are utilized in the present research. The calculated springback by Yoshida 6th yield function [1] and Yoshida-Uemori model [2] shows an excellent agreement with the corresponding experimental data, while the other models underestimate the springback.

DOI： 10.4028/www.scientific.net/KEM.725.566

Scopus

researchmap

Evaluation of bonding strength of thin copper wire and lead-free solder by pullout tests Reviewed

Naoya Tada, Takuhiro Tanaka, Hirotsugu Tabata, Takeshi Uemori, Toshiya Nakata

2016 11th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT)   164 - 167   2016.10

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Recently, copper wires have been attracting much attention for LSI (Large Scale Integration) bonding because of its excellent mechanical and electrical properties, and low material cost. On the other hand, the end of these wires are usually joined to the pads or through-holes on the printed circuit board, and lead-free soldering is one of the popular bonding methods. Since the solders are weaker than copper wires, the stress and strain tend to be concentrated on the interface of solder/wire interface. The fracture frequently occurred there and may influence the quality of product. It is therefore important to evaluate the bonding strength of thin copper wire and lead-free solder. In this paper, pullout tests of thin copper wires from lead-free solder were carried out and the pullout behavior of the wires were observed. A method of bonding strength evaluation was proposed and the results were examined.

DOI： 10.1109/impact.2016.7799989

Web of Science

researchmap

Effect of Hardening Rule on Analysis of Forming and Strength of Multistage Cold Forged Bolt without Heat Treatment Reviewed

Shinobu NARITA, Takeshi UEMORI, Kunio HAYAKAWA, Yoshihiro KUBOTA

Journal of the Japan Society for Technology of Plasticity   57 ( 670 )   1070 - 1076   2016

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Technology and Plasticity  

<p>The isotropic hardening model for an elastic-plastic material have often been used for simulation of cold forging processes, by which, however, it is difficult to represent the Bauschinger effect properly. On the other hand, considering the Bauschinger effect is essential for more precise simulation of the forming process as well as the strength of the forged part without heat treatment. One example is a cold-forged bolt of stainless steel. In the present paper, for two multistage cold forming processes of non-heat-treated stainless steel bolts, the simulations of the forming process and the strength were performed by FE analysis using the YU model that is one of the kinematic hardening models being able to express the Bauschinger effect. As a result, the Bauschinger effect during the forming process can be expressed properly. Moreover, by carrying out the analysis on the tensile test of the forged bolt, the difference in strength by between the isotropic and the kinematic hardening models can be estimated clearly. Furthermore, the effect of the forming process on the strength of the forged bolt can also be evaluated appropriately.</p>

DOI： 10.9773/sosei.57.1070

CiNii Article

CiNii Books

researchmap

Influence of Bauschinger Effect on Forming Simulation Result and Its Solution

UEMORI Takeshi

Journal of the Japan Society for Technology of Plasticity   57 ( 662 )   194 - 198   2016

　More details

Language：Japanese   Publisher：The Japan Society for Technology of Plasticity  

DOI： 10.9773/sosei.57.194

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JLC/20021776654?from=CiNii

Modeling of anisotropic hardening of sheet metals including description of the Bauschinger effect Reviewed

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

INTERNATIONAL JOURNAL OF PLASTICITY   75   170 - 188   2015.12

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The present paper proposes a framework for constitutive modeling of plasticity to describe the evolution of anisotropy and the Bauschinger effect in sheet metals. An anisotropic yield function, which varies continuously with increasing plastic strain, is defined as an interpolation between two yield functions at two discrete levels of plastic strain. Several types of nonlinear functions of the effective plastic strain are proposed for the interpolation. A framework for a combined anisotropic-kinematic hardening model of large-strain cyclic plasticity with small elastic strain is presented, and the details of modeling which is based on the Yoshida-Uemori, model (Yoshida et al., 2002, Yoshida and Uemori, 2002, 2003) are described. The shape of the yield surface and that of the bounding surface are assumed in the model to change simultaneously. The model was validated by comparing the calculated results of stress strain responses with experimental data on r-value and stress-directionality changes in an aluminum sheet (Hu, 2007) and a stainless steel sheet (Stoughton and Yoon, 2009), as well as the variation of the yield surface of an aluminum sheet (Yanaga et al., 2014). Furthermore, anisotropic cyclic behavior was examined by performing experiments of uniaxial tension and cyclic straining in three sheet directions on a 780-MPa advanced high-strength steel sheet. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijplas.2015.02.004

Web of Science

researchmap

Microscopic deformation of polycrystalline pure copper wire during tension Reviewed

Naoya Tada, Yoshitaka Matsukawa, Takeshi Uemori, Toshiya Nakata

2015 10th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT)   229 - 232   2015.10

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In order to clarify the inhomogeneous deformation of thin copper wire, an interrupted tensile test was carried out on the stage of the digital holographic microscope (DHM). The inhomogeneity was evaluated based on the non-uniform change in height distribution on the surface of thin wire specimen during the test. Microscopic plastic deformation by a unit of crystal grain and large gradient in height distribution along grain boundaries were observed. The increase in average height of grain between two earlier loading steps corresponded to that between two later loading steps. This result suggests that the microscopic deformation at the latter stage of tension is predictable from that at the early stage of the tension.

DOI： 10.1109/impact.2015.7365226

Web of Science

researchmap

Shear Deformation Behavior of Adhesive Layer in Stretch-bending/unbendingof Adhesively Bonded Dissimilar Sheet Metals Reviewed

TOKUDA Taro, YOSHIDA Tetsuya, UEMORI Takeshi, TAKIGUCHI Michihiro, YOSHIDA Fusahito

Journal of The Adhesion Society of Japan   51 ( 7 )   347 - 354   2015.7

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Adhesion Society of Japan  

<p>In this study, the shear deformation behavior of adhesive layer in stretch-bending/unbending foradhesively bonded dissimilar sheet metals was investigated by two types of experiments and finiteelement analysis. Major results obtained are summarized as follows:（1）The shear deformation behaviorof adhesive layer was observed in bending/unbending tests with two experimental apparatus.（2）The shear deformation of adhesive layer was influenced by the die corner radius and the tensilespeed.（3）The tensile strength of adherend has a large influence on the shear deformation behavior ofadhesive layer. It is possible to suppress the shear deformation of adhesive layer by using a materialwith small tensile strength as one of the two adherends.（4）The delamination of adhesive layer wasoccurred when the shear strain of adhesive layer in stretch-bending/unbending exceeded a certainvalue（approximately 1.7）.（5）FEM analysis was carried out with using constitutive equations possibleto express the visco-plastic behavior obtained in previous research. However the new yield functionwas proposed in this study for improving the precision of FEM analysis, an expected result was notobtained.</p>

DOI： 10.11618/adhesion.51.347

CiNii Article

CiNii Books

researchmap

Modeling of large-strain cyclic plasticity including description of anisotropy evolution for sheet metals Reviewed

Fusahito Yoshida, Takeshi Uemori, Hiroshi Hamasaki

Advanced Structured Materials   64   571 - 585   2015.6

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Verlag  

The present paper describes a framework for the constitutive modeling of a large-strain cyclic plasticity to describe the evolution of anisotropy and the Bauschinger effect of sheet metals that is based on the Yoshida-Uemori kinematic hardening model. In the model, the shapes of the yield and the bounding surfaces are assumed to change simultaneously with increasing plastic strain. An anisotropic yield function that varies continuously with the plastic strain is defined by a nonlinear interpolation function of the effective plastic strain using a limited number of yield functions determined at a few discrete points of plastic strain. With this modeling framework, any type of yield function can be used and the convexity of the yield surface is always guaranteed. A set of kinematic parameters can be identified experimentally independent of the anisotropic parameters.

DOI： 10.1007/978-3-319-19440-0_26

Scopus

researchmap

Cyclic plasticity model for accurate simulation of springback of sheet metals Reviewed

Fusahito Yoshida, Takeshi Uemori

60 Excellent Inventions in Metal Forming   61 - 66   2015.1

　More details

Language：English   Publishing type：Part of collection (book)   Publisher：Springer Berlin Heidelberg  

The use of a plasticity model that properly describes material behavior is of vital importance for accurate numerical simulation of sheet metal forming, especially for the prediction of springback. For that purpose a large-strain cyclic plasticity model, so-called Yoshida-Uemori model, was proposed in the kinematic hardening modeling framework. It is able to describe properly material behavior, such as the Bauschinger effect, the workhardening stagnation, strain-range dependent cyclic workhardening, as well as the degradation of unloading stress-strain slope with increasing plastic strain. The model has been implemented into several FE commercial codes, and it is widely used in sheet metal forming industry. By using it, the accurate springback prediction, especially for high strength steel sheets, is made possible.

DOI： 10.1007/978-3-662-46312-3_10

Scopus

researchmap

Implicit stress integration and consistent tangent matrix for Yoshida's 6th order polynomial yield function combined with yoshida-uemori kinematic hardening rule Reviewed

Hiroshi Hamasaki, Fusahito Yoshida, Takeshi Uemori

Key Engineering Materials   651-653   558 - 563   2015

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

This paper describes fully implicit stress integration scheme for Yoshida's 6th order yield function combined with Yoshida-Uemori kinematic hardening model and its consistent tangent matrix. Cutting plane method was employed for accurate integrations of stress and state variables appeared in Yoshida-Uemori model. In the present scheme, equivalent plastic strain, stress tensor and all the state variables are treated as independent variables in order to handle the 6th order yield function which is not the J2 yield function, and the equilibriums for each variables are solved for the stress integration. Subsequently, exact consistent tangent matrix which is necessary for implicit static finite element simulation was obtained. The proposed scheme was implemented into finite element code LS-DYNA and deep drawing process for aluminum alloy sheet was calculated. The earing appearance after drawing was compared with the experiment.

DOI： 10.4028/www.scientific.net/KEM.651-653.558

Scopus

researchmap

Die-dending of adhesively bonded sheet metals Reviewed

Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Takeshi Uemori, Fusahito Yoshida

Key Engineering Materials   626   103 - 108   2015

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

In this paper, the deformation behavior of adhesive layer in die-Bending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the bending/unbending shear deformation of the adhesive layer during the die-Bending of adhesively bonded sheet metals by using highly ductile acrylic adhesive. Major results obtained are summarized as follows: (1) The bending/unbending shear deformation of the adhesive layer was observed during the die-Bending. (2) The punch radius has a large influence on the die-Bending in the adhesively bonded sheet metals. (3) It is desirable to perform die-Bending at high speed as well as air-Bending. © (2015) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/KEM.626.103

Scopus

researchmap

Evaluation of forming limit by principal shear strain energies Reviewed

Hidenori Yoshimura, Hiroya Horita, Takeshi Uemori, Tetsuo Naka, Yutaka Mihara

Keikinzoku/Journal of Japan Institute of Light Metals   65 ( 5 )   190 - 195   2015

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Light Metals  

In sheet metal forming, crack in the formed sheets is one of the serious defects, and it is tried to avoid the crack by use of numerical simulation. In the simulation, period and location of the occurrence should be quantitatively evaluated by the formulated criteria. For prediction of crack occurrence, various ductile fracture criteria have been proposed. These criteria are based on the void damage theory and include effect of void growth and coalescence at the late stage of the fracture. In sheet forming, however, not only crack but also necking is problems, and it is important to obtain forming limit of the uniform deformation. Although the forming limit has been examined by M-K theory etc., the criteria does not reach the sufficient level. We consider that the plastic deformation depend on the shear deformation and the criterion by three principal shear strain energies is proposed. In order to verify applicability of the criterion, flat-die drawing tests of aluminum sheets with proportional and non-proportional strain passes were carried out and the forming limit curves predicted by the proposed criterion comparatively agrees with the test results.

DOI： 10.2464/jilm.65.190

Scopus

researchmap

Influence of Bauschinger effect and anisotropy on springback of aluminum alloy sheets Reviewed

Uemori Takeshi, Sumikawa Satoshi, Naka Tetsuo, Ma Ninshu, Yoshida Fusahito

Journal of Japan Institute of Light Metals   65 ( 11 )   582 - 587   2015

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

For accurate springback calculations, the development of accurate constitutive equation “Yoshida–Uemori model” must always be taken into account. However, several springback calculations of other sheet metals by Yoshida–Uemori model have shown wrong agreements with the corresponding experimental data. The reason is why most of them have been calculated from the view point of the accuracy of Bauschinger effect without the strong anisotropy of sheet metal. In the present paper, we have investigated how the initial anisotropy affects the amount of springback for aluminum sheet metals with Bauschinger effect. Specifically, hat bending experiments in R.D. and T.D. were compared with the corresponding calculations. From the above mentioned comparisons, we found that the optimum combination of an anisotropic yield functions and Yoshida–Uemori model is very important for accurate springback analysis.

DOI： 10.2464/jilm.65.582

CiNii Article

CiNii Books

researchmap

Finite element analysis of high tensile strength steel sheet by using complex step derivative approximations Reviewed

Takeshi Uemori, Hiroshi Miyake, Tetsuo Naka, Michihiro Takiguchi, Fusahito Yoshida

Key Engineering Materials   626   187 - 192   2015

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

The framework for the complex step derivative approximations (hereafter CDSA) to calculate the consistent tangent moduli is studied. The present methods is one of the most effective methods to implement any material constitutive equations to the commercial finite element codes and does not suffer from calculation conditions and errors. In order to confirm the efficiency of CDSA, we developed the user subroutine code based on the CDSA using associative J2 flow rules with general nonlinear isotropic hardening rules that is commonly and widely utilized in commercial finite element codes. In this study, the user material subroutine 'Hypela2' of MSC.Marc (ver.2013.0.0) was utilized. The finite element calculation result by the proposal method shows a good agreement with the corresponding result by the MSC.Marc default setting. Also we apply the Yoshida-Uemori back stress model to the CDSA and evaluate this new technique to predict the deformation behavior of high tensile strength steel sheet. © (2015) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/KEM.626.187

Scopus

researchmap

Report of Strain Gauge Seminar under the Auspices of Chugoku-Sikoku Branch

UEMORI Takeshi

Journal of the JSTP   55 ( 636 )   14 - 14   2014

　More details

Language：Japanese   Publisher：The Japan Society for Technology of Plasticity  

DOI： 10.9773/sosei.55.14

CiNii Article

researchmap

Observations of cyclic deformation behaviors of aluminum sheet and constitutive modeling Reviewed

Takeshi Uemori, Satoshi Sumikawa, Tetsuo Naka, Fusahito Yoshida

11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014   81   933 - 938   2014

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Aluminum sheet metals have been widely utilized for a light weight construction of automobile. However, these metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical features such as plastic anisotropy of yield stress and small Lankford value. In order to solve the problems, the present author has developed a new constitutive model. The model can describe accurate non-proportional hardening behaviors of aluminum sheet metals. In the present research, some experimental procedures were carried out to reveal the mechanical properties of an aluminum sheet under proportional and non-proportional deformations. The comparisons between experimental data and the corresponding calculated results by the proposed constitutive model confirm the advantages of our model. (C) 2014 Published by Elsevier Ltd.

DOI： 10.1016/j.proeng.2014.10.120

Web of Science

researchmap

A model of anisotropy evolution of sheet metals Reviewed

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014   81   1216 - 1221   2014

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Conventional plasticity models assume that shapes of yield surfaces are remain fixed throughout plastic deformation. However, some experiments show that anisotropy is changing with increasing plastic strain. This paper proposes a constitutive model that describes the evolution of anisotropy, both for the stress directionality and r-values, of sheet metals. The evolution of anisotropy is expressed by the change of the yield function as a function of the effective plastic strain. The anisotropy model is validated by comparing the experimental data on AA6022-T43 aluminium sheet (after Stoughton, T. B. and Yoon, J. W., Int J Plasticity 25 (2009) 1777-1817). This model is incorporated into the Yoshida-Uemori kinematic hardening model to describe both the Bauschinger effect and the anisotropy evolution. (C) 2014 Published by Elsevier Ltd.

DOI： 10.1016/j.proeng.2014.10.100

Web of Science

researchmap

Springback of Aluminum alloy sheet metal and its modeling Reviewed

Takeshi Uemori, Satoshi Sumikawa, Syohei Tamura, Tetsuo Naka, Fusahito Yoshida

ADVANCES IN MATERIALS AND PROCESSING TECHNOLOGIES XVI   939   361 - +   2014

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Aluminum alloy sheet metals have been widely utilized for a light weight construction of automobile. However, Aluminum sheet metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical weak features such as lower Young's modulus, strong plastic anisotropy of yield stress, Lankford values, and so on. In order to solve the problems, the present author has developed a new constitutive model called "Modified Yoshida-Uemori model". The present model can describe accurate non-proportional hardening behaviors of Aluminum alloy sheet metals.
In the present research, several experimental procedures were carried out to reveal the mechanical properties of Aluminum alloy sheet metals. From the comparison between experimental data and the corresponding calculated results by our constitutive model, the performance of our model was evaluated. In addition to the above mentioned research, the evaluation of some springback analyses were also carried out. The calculated results show good agreements with the corresponding experimental data.

DOI： 10.4028/www.scientific.net/AMR.939.361

Web of Science

researchmap

Deformation behavior of adhesive layer in stretch-bending/unbending for adhesively bonded sheet metals

Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Takeshi Uemori, Fusahito Yoshida

ADVANCES IN MATERIALS AND PROCESSING TECHNOLOGIES XVI   939   19 - +   2014

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

In this paper, the deformation behavior of adhesive layer in stretch-bending/unbending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the cyclic shear deformation of the adhesive layers during the plastic working. Major results obtained are summarized as follows: (1) When the adhesively bonded sheet metals is bent and pulled out at a 90 degrees angle, shear deformation due to bending of the adhesive layer starts shortly before reaching the die corner and unbending starts at the middle of the corner. (2) The die radius has a large influence on the bending behavior. (3) It is possible to suppress shear deformation of the adhesive layer by using a material with small tensile strength as one of the two adherends.

DOI： 10.4028/www.scientific.net/AMR.939.19

Web of Science

researchmap

Modeling of Bauschinger Effect During Stress Reversal Reviewed

Takeshi Uemori, Satoshi Sumikawa, Fusahito Yoshida

STEEL RESEARCH INTERNATIONAL   84 ( 12 )   1267 - 1272   2013.12

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

It is widely known that the constitutive model of Bauschinger effect is one of key points to conduct the accurate sheet metal stamping. In the present research, the elasto-plasticity behaviors of thin sheet metals were investigated by conducting in-plane cyclic tension-compression tests in the different angle from the pre-strained direction. In order to evaluate the accuracy of constitutive models for describing the above mentioned elasto-plasticity behaviors, including the Bauschinger effect, some numerical experiments were conducted for the corresponding stress paths calculations by using three kinds of constitutive models: the isotropic hardening model (hereafter IH model), Yoshida-Uemori model (hereafter Y-U model), and the modified Yoshida-Uemori kinematic hardening model (hereafter modified Y-U model). From the comparisons, it is found that the author's present constitutive model shows a good agreement with the experimental stress-strain responses.

DOI： 10.1002/srin.201300048

Web of Science

researchmap

A user-friendly 3D yield function to describe anisotropy of steel sheets

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

INTERNATIONAL JOURNAL OF PLASTICITY   45   119 - 139   2013.6

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A sixth-order polynomial type 3D yield function, which has a high flexibility of describing anisotropic behavior of steel sheet, is proposed. The yield function is constructed as a sum of several components of the Cazacu and Barlat, 2001 which was derived as an extension of the J2-J3 Drucker yield criterion (Drucker, 1949) to orthotropy using the linear transformation of the stress deviator, so that the convexity of the yield locus is perfectly guaranteed. The model was validated by comparing the numerical predictions of planar anisotropy of r-values and flow stress directionality, as well as the shape of yield loci, with the corresponding experimental data on several types of steel sheets (high r-valued IF steel and SPCE, and high strength steel sheets of 440-980 MPa TS grades). For most of steel sheets, the model using the sum of two J(2) components, which involve eight anisotropic coefficients, is sufficient for the description of their anisotropies. Further it was found that the consideration of J(3) effect improves the description of anisotropy for some steel sheets (e.g., high r-valued IF steel and 980 MPa grade dual phase HSS). (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijplas.2013.01.010

Web of Science

researchmap

Description of Anisotropy and the Bauschinger Effect on Various Types of Steel Sheets Reviewed

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

11TH INTERNATIONAL CONFERENCE ON NUMERICAL METHODS IN INDUSTRIAL FORMING PROCESSES (NUMIFORM 2013)   1532   158 - 165   2013

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

To describe the anisotropy of sheets a sixth-order polynomial type 3D yield function is proposed. The yield function is constructed as a sum of several components of the Cazacu-Barlat function (2001) which was derived as an extension of the J2-J3 Drucker yield criterion (1949) to orthotropy using the linear transformation of the stress deviator. In this framework of modeling, the convexity of the yield locus is perfectly guaranteed. The model was validated by comparing the numerical predictions of planar anisotropy of r-values and flow stress directionality, as well as the shape of yield loci, with the corresponding experimental data on several types of steel sheets (high r-valued IF steel and SPCE, and high strength steel sheets of 440-980MPa TS grades). For most of steel sheets, the model of the sum of two J2 components, which involve eight anisotropic coefficients, is sufficient for the description of their anisotropies. For the description of the Bauchinger effect and cyclic workhardening characteristic, Yoshida-Uemori kinematic hardening model (2002a, 2002b, 2003) was employed, which includes a new proposal to describe non-saturation type workhardening.

DOI： 10.1063/1.4806820

Web of Science

researchmap

Influence of Anisotropic Yield Functions on Parameters of Yoshida-Uemori Model Reviewed

Hirotaka Kano, Jiro Hiramoto, Toru Inazumi, Takeshi Uemori, Fusahito Yoshida

CURRENT STATE-OF-THE-ART ON MATERIAL FORMING: NUMERICAL AND EXPERIMENTAL APPROACHES AT DIFFERENT LENGTH-SCALES, PTS 1-3   554-557   2440 - 2452   2013

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The Yoshida-Uemori model (Y-U model) can be used with any types of yield functions. The calculated stress strain response will be, however, different depending on the function chosen and on the effective plastic strain definition. Thus several modifications to the Y-U model were proposed in the 10th International Conference on Technology of Plasticity [1]. It was ascertained that in the modified Y-U model, the same set of material parameters can be used with von Mises, Hill's 1948, and Hill's 1990 yield function. In this study, Yld2000-2d and Yoshida's 6th-order polynomial type 3D yield function were examined and it was clarified that the same set of Y-U parameters can be used with these yield functions.

DOI： 10.4028/www.scientific.net/KEM.554-557.2440

Web of Science

researchmap

Temperature and Processability of Magnesium Alloy AZ31 on Rectangular Cup Deep Drawing Reviewed

Yasuhide Nakayama, Tetsuo Naka, Takeshi Uemori, Ichiro Shimizu

ADVANCES IN ENGINEERING PLASTICITY XI   535-536   326 - +   2013

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The magnesium alloys, that have high specific strength, are often applied to the industrial products. However, the magnesium alloys exhibit low ductility at the room temperature on account of its hexagonal close-packed structure. It is difficult to give large deformation to the magnesium alloys at room temperature. Therefore, the plastic forming of a magnesium alloy sheet needs the process at warm temperature. In the present work, the procedure of thermal-mechanical coupled analyses are employed. The numerical simulations of warm deep drawings have been performed in order to evaluate the dependence of the temperature on the plastic forming of a magnesium alloy AZ31 sheet. The mechanical properties of the magnesium alloy AZ31 shall be described as the functions depending on temperature. The shapes of punches and die holes are rectangle whose aspect ratios are 1.5 or 2.0. The corners of punches and dies are heated locally at 473K. The influence of local heating on the formability have been investigated. The relation between the blank size and the formability has been also estimated. As the results of numerical simulations, it was shown that the formability of deep drawing was improved by local heating to the punch and the die. When the blanks of various sizes were tried, the distributions of the plastic strain rate around the die corner were changed. Therefore, the deviation of the plastic flow and the temperature distribution arose in a sheet. Consequently, it is necessary to optimize the blank sizes according to the shape of die holes in addition to the forming temperature.

DOI： 10.4028/www.scientific.net/KEM.535-536.326

Web of Science

researchmap

Constitutive equations of stress-strain responses of aluminum sheet under stress path changes

2012.12

　More details

researchmap

Description of Planer Anisotropy and Cyclic Plasticity Behavior of Aluminum Sheet Based on Crystal Plasticity Theory Reviewed

Takumi Kobayashi, Kohshiroh Kitayama, Takeshi Uemori, Fusahito Yoshida

MATERIALS AND COMPUTATIONAL MECHANICS, PTS 1-3   117-119   1397 - +   2012

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

In sheet metal forming, the anisotropy and the Bauschinger effect of sheets affect greatly their formability. This paper discusses how the planar anisotropy and cyclic plastic behavior (the Bauschnger effect and cyclic workhardening characteristics) correlate with the crystallographic texture based on the crystal plasticity analysis on A5052-O sheet. The analytical predictions of r-values and the cyclic stress-strain responses are compared with the experimental observations (S. Tamura et al., Materials Trans, 52-5 (2011), pp.868-875).

DOI： 10.4028/www.scientific.net/AMM.117-119.1397

Web of Science

researchmap

Direct selective laser sintering of WC-CO cemented carbide by premixing of additives Reviewed

Hideki Kyogoku, Takeshi Uemori, Akihiko Ikuta, Kenichi Yoshikawa, Hitoshi Ohmori

ASME/ISCIE 2012 International Symposium on Flexible Automation, ISFA 2012   465 - 468   2012

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Mechanical Engineers (ASME)  

In this study, the fabrication conditions of WC cemented carbides by direct selective laser melting were investigated. The effects of additives, such as Co, Cu-20%Sn and Cu powders, and laser scanning conditions on laser sintering process were examined to fabricate a sound laser-scanned body of WC cemented carbides. The optimum laser power, scan speed and scan pitch were found out by experiments. It was found that the continuously smooth single-scan track can be obtained at a lower laser power and a higher scan speed by the addition of 30% Cu powder. The smooth surface of the laser-scanned body could be fabricated at a laser power of 9 W, a scan speed of 20 mm/s and a scan pitch of 0.05 mm. Copyright © 2012 by ASME.

DOI： 10.1115/ISFA2012-7182

Scopus

researchmap

Elasto-plasticity Behavior of IF Steel Sheet with Planar Anisotropy and Its Macro-meso Modeling

Kohshiroh Kitayama, Takumi Kobayashi, Takeshi Uemori, Fusahito Yoshida

ISIJ INTERNATIONAL   52 ( 4 )   735 - 742   2012

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Elasto-plasticity behavior of an IF steel sheet was investigated by performing uniaxial tension tests in three directions (0 degrees, 45 degrees and 90 degrees to the rolling direction of the sheet), in-plane cyclic tension compression test and bi-axial tension test. The sheet has strong planar anisotropy (r(0) = 2.15, r(45) = 2.12 and r(90) = 2.89) but very weak flow stress directionality. Equi-biaxial flow stress is as large as 1.23 times of the uniaxial flow stress. These elasto-plasticity deformation characteristics, as well as the Bauschinger effect and cyclic hardening behavior, are well described by a macro-plasticity model (Yoshida-Uemori model incorporating with the 4th-order anisotropic yield function). Further, the simulation of elasto-plasticity stress strain responses of the sheet were conducted by two types of crystal plasticity models, i.e., Taylor hypothesis based model and CPFEM, using the crystallographic orientation distribution data measured by neutron diffraction method. The models capture most of the above-mentioned deformation characteristics qualitatively, but the predicted anisotropy and the Bauschinger effect are weaker than those of the real material. The CPFEM gives more realistic results than the Taylor model.

DOI： 10.2355/isijinternational.52.735

Web of Science

researchmap

OS0303 Experimental Observations of In-Plane Cyclic Tension-Compression Test for Magnesium Alloy Sheet and Its Modelling

UEMORI Takeshi, KATAHIRA Takuji, YOSHIDA Fusahito, KOHTSU Masahide, ADACHI Daiki

The Proceedings of the Materials and Mechanics Conference   2012 ( 0 )   _OS0303 - 1_-_OS0303-2_   2012

　More details

Language：Japanese   Publisher：一般社団法人 日本機械学会  

To investigate the deformation behavior of a magnesium sheet, the finite element calculation was carried out under tension and in-plane cyclic tension-compression test. From the experimental data, the twin deformation was observed during the tensile deformation after uniaxial compression. For the accurate description of the above mentioned twin deformation, we have developed the constitutive equation of twining behavior. From the comparison, it is found that the developed constitutive equations can calculate stress-strain response accurately.

CiNii Article

CiNii Books

researchmap

Porous titanium dental implants fabricated using metal injection molding

Hideki Kyogoku, Makiko Yonehara, Takeshi Uemori, Hideki Nakayama

Proceedings of the International Euro Powder Metallurgy Congress and Exhibition, Euro PM 2012   3   2012

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：European Powder Metallurgy Association (EPMA)  

The porous titanium implants were tried to fabricate by metal injection molding process. Gas-atomized Ti powder and PMMA powders of various mean particle diameters between 20 and 185 μm were used. The pore size was approximately proportional to the diameter of PMMA powder. The relative density and tensile strength of the sintered compact decreased with increasing the mean particle diameter of PMMA powder. The tension and compression tests were performed to examine the mechanical properties of the porous sintered compacts. The tensile strength of the porous sintered compact added 30 vol.%PMMA of diameter of 185 μm was around 300 MPa. It was found that the strength of the porous compact decreases with increasing the amount of addition of PMMA powder. The design of dental implants was investigated by using a FEM analysis. As a result, the porous dental titanium implants were successfully fabricated by metal injection molding process.

Scopus

researchmap

Influence of Yield Functions on Parameters of the Yoshida-Uemori Model

Steel Research International   830 - 835   2011.10

　More details

researchmap

Constitutive Equations of Bauschinger Effect under Stress Path Change

Steel Research International   819 - 823   2011.10

　More details

researchmap

Experimental Observation of Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets Reviewed

Shohei Tamura, Satoshi Sumikawa, Takeshi Uemori, Hiroshi Hamasaki, Fusahito Yoshida

MATERIALS TRANSACTIONS   52 ( 5 )   868 - 875   2011.5

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Elasto-plasticity behavior of type A5052-O and AA6016-T4 aluminum alloy sheets was examined by performing several experiments of uniaxial tension, biaxial stretching and in-plane cyclic tension-compression. Both sheets exhibit apparent r-value planar anisotropy, especially for AA6016-T4 it is extremely strong. while their flow stress directionality under uniaxial tension is not so significant. Both the sheets show strong cyclic hardening with weak Bauschinger effect. Such material behavior is well described by Yoshida-Uemori kinematic hardening model combined with an appropriate choice of anisotropic yield function. [doi:10.2320/matertrans.L-MZ201101]

DOI： 10.2320/matertrans.L-MZ201101

Web of Science

researchmap

Elasto-plasticity Behavior of IF Steel Sheet with Planar Anisotropy and Its Macro-Meso Modeling Reviewed

Koushirou Kitayama, Takumi Kobayashi, Takeshi Uemori, Fusahito Yoshida

TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN   97 ( 4 )   221 - 229   2011.4

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Elasto-plasticity behavior of a IF steel sheet was investigated by performing uniaxial tension tests in three directions (0 degrees, 45 degrees and 90, to the rolling direction of the sheet), in-plane cyclic tension compression test and bi-axial tension test. The sheet has strong planar r-value anisotropy (r(0) = 2.15, r(45) = 2.12 and r(90) = 2.89) but very weak flow stress directionality. Equi-biaxial flow stress is as large as 1.23 times of the uniaxial flow stress These elasto-plasticity deformation characteristics, as well as the Bauschinger effect and cyclic hardening behavior, are well described by a macro plasticity model (Yoshida-Uemori model incorpolating with the 4th-order anisotropic yield function). Further, the simulation of elasto-plasticity stress-strain responses of the sheet were conducted by two types of crystal plasticity models, i.e., Taylor hypothesis based model and CPFEM, using the crystallographic orientation distribution data measured by neutron diffraction method. The models capture most of the above-mentioned deformation characteristics qualitatively, but the predicted anisotropy and the Bauschinger effect are weaker than those of the real material. The CPFEM gives more realistic results than the Taylor model.

Web of Science

researchmap

A User-friendly 3D Yield Function for Steel Sheets and Its Application Reviewed

Fusahito Yoshida, Shohei Tamura, Takeshi Uemori, Hiroshi Hamasaki

8TH INTERNATIONAL CONFERENCE AND WORKSHOP ON NUMERICAL SIMULATION OF 3D SHEET METAL FORMING PROCESSES (NUMISHEET 2011), PTS A AND B   1383   807 - +   2011

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

A 6th-order polynomial type 3D yield function, which has a high flexibility of describing anisotropic behavior of steel sheets is proposed. A user-friendly scheme of material parameter identification for the model, where only limited experimental data of r-values and yield stresses in three directions (r(0),r(45),r(90) and alp sigma(0),sigma(45),sigma(90)) plus equi-biaxial yield stress (sigma(x) = sigma(y) = sigma(b)) are needed, is presented. The accuracy of this yield function is verified by comparing the numerical predictions with the corresponding experimental data on planar anisotropy of r-values and flow stress directionality, as well as the shape of yield loci, on several types of steel sheets (high r-value IF steel and high strength steel sheets of 440-980MPa TS levels). The advantage of this model is demonstrated by showing a numerical simulation of hole-expansion test.

DOI： 10.1063/1.3623689

Web of Science

researchmap

Experimental observation of elasto-plasticity behavior of type 5000 and 6000 aluminum alloy sheets Reviewed

Shohei Tamura, Satoshi Sumikawa, Takeshi Uemori, Hiroshi Hamasaki, Fusahito Yoshida

Keikinzoku/Journal of Japan Institute of Light Metals   61 ( 6 )   255 - 261   2011

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)  

Elasto-plasticity behavior of type A5052-O and AA6016-T4 aluminum alloy sheets was examined by performing several experiments of uniaxial tension, biaxial stretching and in-plane cyclic tension-compression. Both sheets exhibit apparent r-value planar anisotropy, especially for AA6016-T4 it is extremely strong, while their flow stress directionality under uniaxial tension is not so significant. Both the sheets show strong cyclic hardening with weak Bauschinger effect. Such material behavior is well described by Yoshida-Uemori kinematic hardening model combined with an appropriate choice of anisotropic yield function.

DOI： 10.2464/jilm.61.255

Scopus

researchmap

Elasto-plasticity behavior of if steel sheet with planar anisotropy and its macro-meso modeling

Koushirou Kitayama, Takumi Kobayashi, Takeshi Uemori, Fusahito Yoshida

Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan   97 ( 4 )   221 - 229   2011

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)  

Elasto-plasticity behavior of a IF steel sheet was investigated by performing uniaxial tension tests in three directions (0°, 45° and 90, to the rolling direction of the sheet), in-plane cyclic tension-compression test and bi-axial tension test. The sheet has strong planar r-value anisotropy (r0=2.15, r45=2.12 and r90=2.89) but very weak flow stress directionality. Equi-biaxial flow stress is as large as 1.23 times of the uniaxial flow stress. These elasto-plasticity deformation characteristics, as well as the Bauschinger effect and cyclic hardening behavior, are well described by a macro-plasticity model (Yoshida-Uemori model incorpolating with the 4th-order anisotropic yield function). Further, the simulation of elasto-plasticity stress-strain responses of the sheet were conducted by two types of crystal plasticity models, i.e., Taylor hypothesis based model and CPFEM, using the crystallographic orientation distribution data measured by neutron diffraction method. The models capture most of the above-mentioned deformation characteristics qualitatively, but the predicted anisotropy and the Bauschinger effect are weaker than those of the real material. The CPFEM gives more realistic results than the Taylor model.

DOI： 10.2355/tetsutohagane.97.221

Scopus

researchmap

Elasto-Plasticity Behavior of High Strength Steel Sheet in Biaxial Stress Path Change

Takeshi Uemori, Tohru Kuramitsu, Yuji Mito, Ryutaro Hino, Tetsuo Naka, Fusahito Yoshida

MATERIALS TRANSACTIONS   51 ( 10 )   1814 - 1818   2010.10

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

The elasto plasticity behavior of a high strength steel sheet of 980 MPa TS was investigated by performing biaxial tension experiments In order to evaluate the accuracy of constitutive models of plasticity in describing such elasto plasticity behavior numerical simulations of stress strain responses were conducted for the same stress paths as those in the experiments using two types of constitutive models the isotropic hardening model (IH model) and the kinematic hardening model proposed by the present authors (Yoshida Uemori model) In this work special emphasis is placed in the cases of stress path change In experiments on radial loadings after equi balanced tension preloading It was found that flow stresses are considerably lower than uniaxial tension flow stress The IH model can hardly describe this phenomenon although it is sufficient for stress strain analysis of proportional loading cases In contrast to this the Yoshida Uemori model can well predict every stress strain response in biaxial stress path changes [doi 10 2320/matertrans P M2010817].

DOI： 10.2320/matertrans.P.M2010817

Web of Science

researchmap

Prediction of Fracture for High Strength Steel Sheets under Stretch Bending Reviewed

Tetsuo Naka, Takanori Kurose, Takeshi Uemori, Ryutaro Hino, Fusahito Yoshida

STEEL RESEARCH INTERNATIONAL   81 ( 9 )   841 - 844   2010.9

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Since high strength steel sheets have low ductility, fracture sometimes occurs in their press forming, especially at a die corner under stretch bending. In the present work, the fracture limits of high strength steel sheets under stretch bending were investigated by performing three-points stretch bending experiments with various punch-radii on six types of high strength steel sheets (590-1180MPa). From the experiment, it was found that stronger the sheet lower the fracture limit measured by limit wall stretch, L-max/L-0(L-max: limit wall length of a sheet, L-0: initial wall length). It comes from a fact that the workhardening exponent (n-value) decreases with increasing the strength of the sheet. To predict the fracture limits, a fracture criterion proposed by Yoshida et al., in which limit wall stretch is explicitly given as a function of non dimensional bending radius, t(0)/R (t(0): sheet thickness, R: bending radius) and materials' n-value, was employed. The predicted limit wall stretch, as well as the limit forming height, was in good agreement with the corresponding experimental results.

Web of Science

researchmap

Springback Simulation of High Strength Steel Sheets Calculated by Yoshida-Uemori Model Reviewed

Takeshi Uemori, Satoshi Sumikawa, Shohei Tamura, Hiroyuki Akagi, Tetsuo Naka, Fusahito Yoshida

STEEL RESEARCH INTERNATIONAL   81 ( 9 )   825 - 828   2010.9

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

For the accurate simulation of springback on high strength steel sheets, the use of an appropriate material model is of vital importance. In general, major aspects of material modelling are on the yield function and the hardening law. In the present work, using the framework of Yoshida-Uemori model (F. Yoshida and T. Uemori, Int J Plasticity, 18, 2002, 661-686), which is an advanced kinematic hardening model incorporating with a selected anisotropic yield function, FE simulations of springback in draw bending and S-rail forming (Numisheet'96 model) of 590 and 980MPa levels high strength steel sheets were performed, and the results were compared with the corresponding experimental observations. From the results, it is concluded that the modelling of the Bauschinger effect, including the plastic-strain dependent Young's modulus, is essential for accurate simulation of springback of high strength steel sheets, but the selection of an anisotropic yield function would be of minor effect since most of HSSs have weak anisotropies.

Web of Science

researchmap

Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling Reviewed

Shohei Tamura, Satoshi Sumikawa, Hiroshi Hamasaki, Takeshi Uemori, Fusahito Yoshida

NUMIFORM 2010, VOLS 1 AND 2   1252   630 - +   2010

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r(0), r(45) and r(90)), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh's biquadratic yield function and Barlat's Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model).

Web of Science

researchmap

Constitutive modeling for Sheet Metal Forming Simulation

2010

　More details

researchmap

G0300-5-1 Numerical simulation of cyclic stress-strain responses for sheet metals by homogenaization method

KAGEYAMA Takahiro, UEMORI Takeshi, YOSHIDA Fusahito

The proceedings of the JSME annual meeting   2010   215 - 216   2010

　More details

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

With the great development of computer hard technologies, there is a great demand for the accurate finite element analysis which can deal with the morphology of materials. There were so many reports that the complicated plastic deformation behaviors such as "Work hardening", "Bauschinger effect" and "Permanent softening" is related to morphology. We have introduced the Homogenization theory into the commercial finite element code "Marc" in order to research how different stress-strain responses were obtained.

DOI： 10.1299/jsmemecjo.2010.1.0_215

CiNii Article

CiNii Books

researchmap

G0300-5-2 Springback analysis of high tensile strength steel sheet

AKAGI Hiroyuki, TAMURA Syohei, SUMIKAWA Satoshi, UEMORI Takeshi, YOSHIDA Fusahiro

The proceedings of the JSME annual meeting   2010   217 - 218   2010

　More details

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

High tensile strength steel sheets have been widely used in the automobile industries to produce the light weight constructions. However the large springback deformation due to the high flow stress makes it difficult to the final shapes of car parts. In order to solve the problem, we propose the most accurate constitutive equation "Yoshida-Uemori model". In the present report, we evaluated usefulness of the constitutive equation.

DOI： 10.1299/jsmemecjo.2010.1.0_217

CiNii Article

CiNii Books

researchmap

FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION Reviewed

Tetsuo Naka, Yasuhide Nakayama, Takeshi Uemori, Ryutaro Hino, Fusahito Yoshida

ENGINEERING PLASTICITY AND ITS APPLICATIONS: FROM NANOSCALE TO MACROSCALE   638 - 643   2009

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Forming Limit Diagrams (FLDs) of a magnesium alloy (AZ31) sheet at various forming speeds (3 to 300 mm.mm(-1)) at several temperatures of 100-250 degrees C were investigated by performing a punch stretch-forming test. The forming limit strains increased with temperature rise and with decreasing forming speed, where the effect of forming speed was stronger at higher temperatures. To describe such a characteristic of FLD of AZ31, the Marciniak-Kucznski type forming limit analysis was conducted using the Backofen-type constitutive equation (sigma = C epsilon(n) (epsilon) over dot(m)). In this analysis, the damage evolution in the necking zone was taken into account based on Oyane&apos;s ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.

Web of Science

researchmap

PLASTIC DEFORMATION BEHAVIOR OF HIGH STRENGTH STEEL SHEET UNDER NON-PROPORTIONAL LOADING AND ITS MODELING Reviewed

Takeshi Uemori, Yuji Mito, Satoshi Sumikawa, Ryutaro Hino, Fusahito Yoshida, Tetsuo Naka

ENGINEERING PLASTICITY AND ITS APPLICATIONS: FROM NANOSCALE TO MACROSCALE   22 - +   2009

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

This paper deals with plastic deformations of a high tensile strength steel sheet (HTSS sheet) under biaxial stress condition including strain path. Using a cruciform specimen of a HTSS sheet of 780MPa-TS, experiments under proportional and non-proportional loadings were investigated. Numerical simulations of stress-strain responses for several strain paths after biaxial stretching were conducted using a large-strain cyclic plasticity model (Yoshida-Uemori model). The results of numerical simulation agrees well the corresponding experimental results, which is attributed to the accurate modeling of the backstress evolution of the anisotropic yield function.

Web of Science

researchmap

Elasto-plastic defomation behavior of high tensile strength steel sheet under the strain path changes

UEMORI Takeshi, KURAMITSU Tohru, MITO Yuji, HINO Ryutaro, NAKA Testuo, YOSHIDA Fusahito

Journal of the JSTP   50 ( 576 )   39 - 43   2009

　More details

Language：Japanese   Publisher：The Japan Society for Technology of Plasticity  

The elastopasticity behavior of a high-strength steel sheet was investigated by performing biaxial tension experiments. To evaluate the accuracy of constitutive models in describing such elastoplasticity behavior, numerical simulations of stress-strain responses were conducted for the same stress paths as those in the experiments using two types of models: the isotropic hardening model (IH model) and the kinematic hardening model proposed by the present authors (Yoshida-Uemori model). In this work, special emphasise is placed in the cases of stress-path change. In experiments on radial loadings after equibalanced tension preloading, it was found that flow stresses are considerably lower than uniaxial tension flow stress. The IH model hardly describes this phenomenon, although it is sufficient for stress-strain analysis of proportional loading cases. In contrast, the Yoshida-Uemori model can well predict every stress-strain response in biaxial stress-path changes.

DOI： 10.9773/sosei.50.39

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00324822128?from=CiNii

Material testing (tension test and evaluation for deformation behavior and formability)

2009

　More details

researchmap

Cold Butt Joining Steel Sheet by Shot Peening

2009

　More details

researchmap

Butt Joining of Hight Strength Steel Sheet and Dissimilar Metal Sheet by Shot Peening

2009

　More details

researchmap

PLASTIC DEFORMATION BEHAVIOR OF HIGH STRENGTH STEEL SHEET UNDER NON-PROPORTIONAL LOADING AND ITS MODELING

Takeshi Uemori, Yuji Mito, Satoshi Sumikawa, Ryutaro Hino, Fusahito Yoshida, Tetsuo Naka

INTERNATIONAL JOURNAL OF MODERN PHYSICS B   22 ( 31-32 )   5394 - 5399   2008.12

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

This paper deals with plastic deformations of a high tensile strength steel sheet (HTSS sheet) under biaxial stress condition including strain path. Using a cruciform specimen of a HTSS sheet of 780MPa-TS, experiments under proportional and non-proportional loadings were investigated. Numerical simulations of stress-strain responses for several strain paths after biaxial stretching were conducted using a large-strain cyclic plasticity model (Yoshida-Uemori model). The results of numerical simulation agrees well the corresponding experimental results, which is attributed to the accurate modeling of the backstress evolution of the anisotropic yield function.

Web of Science

researchmap

FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION

Tetsuo Naka, Yasuhide Nakayama, Takeshi Uemori, Ryutaro Hino, Fusahito Yoshida, Masahide Kohzu, Kenji Higashi

INTERNATIONAL JOURNAL OF MODERN PHYSICS B   22 ( 31-32 )   6010 - 6015   2008.12

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Forming Limit Diagrams (FLDs) of a magnesium alloy (AZ31) sheet at various forming speeds (3 to 300 mm.mm(-1)) at several temperatures of 100-250 degrees C were investigated by performing a punch stretch-forming test. The forming limit strains increased with temperature rise and with decreasing forming speed, where the effect of forming speed was stronger at higher temperatures. To describe such a characteristic of FLD of AZ31, the Marciniak-Kucznski type forming limit analysis was conducted using the Backofen-type constitutive equation (c = C epsilon(n)epsilon(m)). In this analysis, the damage evolution in the necking zone was taken into account based on Oyane&apos;s ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.

Web of Science

researchmap

FE Simulation of Non-uniform Plastic Deformation of Steel Sheet and Elimination of Yield Point in Temper Rolling(<Special Issue>Progress of Analysis on Micro-plasticity and Practical Technology in Temper Rolling)

YOSHIDA Fusahito, UEMORI Takeshi, KANEDA Yuya, YAMAMOTO Shigeo, GOTO Yoshitaka, SAKAI Gakuto

Tetsu- to- Hagane   94 ( 10 )   384 - 390   2008.10

　More details

Language：Japanese   Publisher：The Iron and Steel Institute of Japan (ISIJ)  

Finite element simulations of temper rolling of a steel sheet were performed using a model of elasto-viscoplasticity that describes the yield-point phenomena such as a high upper yield point, the rate-dependent Luders strain at the yield plateau and the subsequent workhardening. From the simulations of uniaxial tension of temper-rolled sheets, the mechanism of elimination of the yield point by rolling has been clarified. For the purpose of the elimination of the yield point, the roughness of the roll plays an important role. During the temper rolling with rough surface rolls, a number of plastic zones are non-uniformly formed on the surfaces of the sheet, and from these numerous Luders bands will start to propagate simultaneously. Consequently, macroscopic plastic deformation more likely to occur in the temper-rolled sheet under a comparatively low load without showing the yield point.

DOI： 10.2355/tetsutohagane.94.384

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00319515370?from=CiNii

FE Simulation of Non-uniform Plastic Deformation of Steel Sheet and Elimination of Yield Point in Temper Rolling Reviewed

Fusahito Yoshida, Takeshi Uemori, Yuya Kaneda, Shigeo Yamamoto, Yoshitaka Goto, Gakuto Sakai

TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN   94 ( 10 )   A384 - A390   2008.10

　More details

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Finite element simulations of temper rolling of a steel sheet were performed using a model of elasto-viscoplasticity that describes the yield-point phenomena such as a high upper yield point, the rate-dependent Luders strain at the yield plateau and the subsequent workhardening. From the simulations of uniaxial tension of temper-rolled sheets, the mechanism of elimination of the yield point by rolling has been clarified. For the purpose of the elimination of the yield point, the roughness of the roll plays an important role. During the temper rolling with rough surface rolls, a number of plastic zones are non-uniformly formed on the surfaces of the sheet, and from these numerous Luders bands will start to propagate simultaneously. Consequently, macroscopic plastic deformation more likely to occur in the temper-rolled sheet under a comparatively low load without showing the yield point.

Web of Science

researchmap

Effects of strain rate, temperature and sheet thickness on yield locus of AZ31 magnesium alloy sheet

Tetsuo Naka, Takeshi Uemori, Ryutaro Hino, Masahide Kohzu, Kenji Higashi, Fusahito Yoshida

JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   201 ( 1-3 )   395 - 400   2008.5

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Magnesium alloys usually exhibit low ductility at the room temperature due to its hexagonal close-packed structure, but it will be improved at elevated temperature. Therefore, warm press-forming of magnesium alloy sheets is quite attractive. In order to determine the optimum condition of press-forming for magnesium alloy sheets, in the present work, the effects of strain rate, temperature and sheet thickness on the yield locus were experimentally investigated. The yield loci of magnesium alloy (AZ31) sheets with different sheet thickness (0.5 and 0.8 mm) were obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 100, 150, 200, 250 and 300 degrees C at strain rates of 10(-2), 10(-3) and 10(-4) s(-1). Based on the experimental results, the effects of strain rate, temperature and sheet thickness on the yield locus were discussed. The size of yield locus drastically decreases with increasing temperature and decreases with decreasing strain rate. in contrast with the temperature and strain-rate dependence of the yield locus, sheet thickness has no influence on the yield locus. The shape of the yield locus of magnesium sheet is far from the predictions calculated by the yield functions of von Mises, Hill and Cazacu. Instead of these, the yield functions of Logan-Hosford or Barlat is a better choice for the accurate description of biaxial tension stress-strain responses at high temperature. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2007.11.189

Web of Science

researchmap

Finite element simulation

2008

　More details

DOI： 10.2355/tetsutohagane.94.384

researchmap

Effects of strain rate and temperature on yield locus for AZ31 magnesium alloy sheet

Tetsuo Naka, Masanori Hayakashi, Yasu Hide Nakayama, Takeshi Uemori, Masahide Kohzu, Kenji Higashi, Fusahito Yoshida

ENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2   340-341   119 - +   2007

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The yield locus of type AZ31 magnesium alloy sheet was obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 100, 150, 200, 250 and 300 degrees C at strain rates of 10(-2), 10(-3) and 10(-4) s(-1). Based on the experimental results, the effects of strain-rate and temperature on the yield locus was discussed. The size of yield locus drastically decreased with increasing temperature and decreased with decreasing strain-rate. Neither von Mises's criterion or Hill's can well predict the shape of the yield locus of this sheet metal. Instead of these quadratic yield functions, the yield criterion of Logan-Hosford or Barlat is a better choice for the accurate description of biaxial stress-strain responses at high temperature.

Web of Science

researchmap

Plastic deformation behavior of high strength steel sheet under non-proportional loading and its modeling

T. Uemori, T. Kuramitsu, R. Hino, T. Naka, F. Yoshida

ENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2   340-341   895 - +   2007

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

This paper deals with experimental observations and modeling of plastic deformations of a high strength steel sheet (HSS sheet) under biaxial stress conditions. Using a cruciform specimen of a HSS sheet of 980MPa-TS, experiments of proportional and non-proportional loadings were performed. Numerical simulations for the biaxial stress-strain responses were conducted using a constitutive model of large-strain cyclic plasticity (Yoshida-Uemori model), and the results were compared to the experimental data. The results of numerical simulation show a good agreement with the experimental results, which is attributed to accurate modeling of the backstress evolution of the anisotropic yield surface.

Web of Science

researchmap

Modeling of large-strain cyclic plasticity for accurate springback simulation

F. Yoshida, T. Uemori, S. Abe

ENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2   340-341   811 - +   2007

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

This paper describes a model of large-strain cyclic plasticity and its verification by some experiments of cyclic plasticity and biaxial stretching. The performance of this model in springback simulation is discussed by comparing the calculated results for S-rail forming with the experimental data on high strength steel sheet (HSS) of 980MPa-TS. The results of numerical simulations of the springback agree well with the corresponding experimental data, including the torsion-type springback appearing in S-rail forming.

Web of Science

researchmap

Effect of strain-rate and temperature on yield locus for 5083 aluminum alloy sheet Reviewed

T Naka, Y Nakayama, T Uemori, R Hino, F Yoshida

ADVANCES IN ENGINEERING PLASTICITY AND ITS APPLICATIONS, PTS 1 AND 2   274-276   937 - 942   2004

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

To determine yield locus of type, 5083 aluminum-magnesium sheet at elevated temperature, biaxial tensile experiments were performed, using cruciform specimens, at various temperatures (25 - 300 degreesC) at strain rates raging from 10(-5) to 10(-2) s(-1). From the experimental results, the effects of strain rate and temperature on the yield locus are discussed. The size of yield locus drastically decreased with increasing temperature and with decreasing strain rate. Neither von Mises' yield criterion or Hill's can well predict the shape of yield locus of this type of sheet metal. In contrast, the yield criterion of Logan-Hosford or Barlat well simulate the yield locus at elevated temperatures.

Web of Science

researchmap

A model of large-strain cyclic plasticity and its application to springback simulation

F Yoshida, T Uemori

INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES   45 ( 10 )   1687 - 1702   2003.10

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

This paper presents a framework of constitutive modeling of large-strain cyclic plasticity which describes both the deformation- and texture-induced anisotropies of materials. In this model, the transient Bauschinger effect is described accurately by a new equation of the backstress evolution, and the strain-range and mean-strain dependencies of cyclic strain hardening are expressed by a model of workhardening stagnation. For the description of texture-induced anisotropy, any of widely accepted yield criteria of orthotropic anisotropy is easily incorporated into this model. This paper demonstrates the advantage of the present model in the springback analysis over other classical models by comparing the FE simulations of draw bending with the corresponding experimental results. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijmecsci.2003.10.013

Web of Science

researchmap

Effects of temperature on yield locus for 5083 aluminum alloy sheet

T Naka, Y Nakayama, T Uemori, R Hino, F Yoshida

JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   140   494 - 499   2003.9

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Warm press forming of aluminum alloy sheets is quite attractive, since undesirable stretcher strain marks, which often appear on the surface of the sheets during cold press forming, will disappear at high temperature, and furthermore, some aluminum alloys exhibit high-temperature superplasticity at a certain forming speed. In order to determine the optimum condition of press forming for an aluminum alloy sheet, the effect of forming temperature on the yield locus was experimentally investigated. The yield locus for a fine-grain Al-Mg alloy (5083-O) sheet was obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 30, 100, 170, 250 and 300 degreesC at strain rate of 10 s(-1). The size of yield locus drastically decreased with increasing temperature. Neither von Mises' criterion or Hill's can well predict the shape of the yield locus of this sheet metal. Instead of these quadratic yield functions, the yield criterion of Logan-Hosford or Barlat is a better choice for the accurate description of biaxial stress-strain responses at a high temperature. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0924-0136(03)00780-5

Web of Science

researchmap

Effects of temperature on yield locus for 5083 aluminum alloy sheet

T Naka, Y Nakayama, T Uemori, R Hino, F Yoshida

JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   140   494 - 499   2003.9

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Warm press forming of aluminum alloy sheets is quite attractive, since undesirable stretcher strain marks, which often appear on the surface of the sheets during cold press forming, will disappear at high temperature, and furthermore, some aluminum alloys exhibit high-temperature superplasticity at a certain forming speed. In order to determine the optimum condition of press forming for an aluminum alloy sheet, the effect of forming temperature on the yield locus was experimentally investigated. The yield locus for a fine-grain Al-Mg alloy (5083-O) sheet was obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 30, 100, 170, 250 and 300 degreesC at strain rate of 10 s(-1). The size of yield locus drastically decreased with increasing temperature. Neither von Mises' criterion or Hill's can well predict the shape of the yield locus of this sheet metal. Instead of these quadratic yield functions, the yield criterion of Logan-Hosford or Barlat is a better choice for the accurate description of biaxial stress-strain responses at a high temperature. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0924-0136(03)00780-5

Web of Science

researchmap

A model of large-strain cyclic plasticity and its application to springback simulation Reviewed

F Yoshida, T Uemori

ENGINEERING PLASTICITY FROM MACROSCALE TO NANOSCALE PTS 1 AND 2   233-2   47 - 58   2003

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

This paper presents a framework of constitutive modeling of large-strain cyclic plasticity which describes both the deformation- and texture-induced anisotropies of materials. In this model, the transient Bauschinger effect is described accurately by a new equation of the backstress evolution, and the strain-range and mean-strain dependencies of cyclic strain-hardening are expressed by a model of workhardening stagnation. For the description of texture-induced anisotropy, any of widely accepted yield criteria of orthotropic anisotropy is easily incorporated into this model. This paper demonstrates the advantage of the present model in the springback analysis over other classical models by comparing the FE simulations of draw-bending with the corresponding experimental results.

Web of Science

researchmap

A Constitutive Equation for Description of Large-Strain Cyclic Plasticity

YOSHIDA Fusahito, UEMORI Takeshi

Transactions of the Japan Society of Mechanical Engineers   68 ( 667 )   415 - 421   2002

　More details

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper presents a constitutive model of plasticity that describes the cyclic stress-strain responses at large strain. A new equation of backstress evolution is proposed for an accurate simulation of the transient Bauschinger effect. An original idea of a non-isotropic-hardening surface defined in the stress space is presented for the description of the workhardening stagnation appearing under reverse deformation, as well as the strain-range and mean-strain dependencies of cyclic hardening characteristics. The validity of this model is confirmed by comparing the cyclic stress-strain responses calculated by the model with the experimental observations on two types of steel sheets (an aluminum-killed steel and a dual-phase high strength steel of 590 MPa tensile strength).

DOI： 10.1299/kikaia.68.415

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00155932935?from=CiNii

Importance of Appropriate Modeling of the Bauschinger Effect in Springback Analysis

Journal of the Japan Society for Technology of Plasticity   43 ( 498 )   65 - 69   2002

　More details

researchmap

Investigation of Cyclic Elasto-Plastic Behavior of Coppeer Sheet

Key Engineering Materials   2002

　More details

researchmap

Elastic-plastic behavior of steel sheets under in-plane cyclic tension-compression at large strain

F Yoshida, T Uemori, K Fujiwara

INTERNATIONAL JOURNAL OF PLASTICITY   18 ( 5-6 )   633 - 659   2002

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Elastic-plastic behavior of two types of steel sheets for press-forming (an aluminum-killed mild steel and a dual-phase high strength steel of 590 MPa ultimate tensile strength) under inplane cyclic tension-compression at large strain (up to 25% strain for mild steel and 13% for high strength steel) have been investigated. From the experiments, it was found that the cyclic hardening is strongly influenced by cyclic strain range and mean strain. Transient softening and workhardening stagnation due to the Bauschinger effect, as well as the decrease in Young's moduli with increasing prestrain, were also observed during stress reversals. Some important points in constitutive modeling for such large-strain cyclic elasto-plasticity are discussed by comparing the stress-strain responses calculated by typical constitutive models of mixed isotropic-kinematic hardening with the corresponding experimental observations. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0749-6419(01)00049-3

Web of Science

CiNii Article

researchmap

スプリングバック解析におけるバウシンガー効果の適切なモデル化の重要性

塑性と加工   43 ( 498 )   65 - 69   2002

　More details

researchmap

高張力鋼板の面内応力反転時の弾塑性挙動とそのモデル化

塑性と加工   43 ( 494 )   59 - 63   2002

　More details

researchmap

A model of large-strain cyclic plasticity describing the Bauschinger effect and workhardening stagnation

F Yoshida, T Uemori

INTERNATIONAL JOURNAL OF PLASTICITY   18 ( 5-6 )   661 - 686   2002

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

This paper presents a constitutive model that has a high capability of describing the deformation behavior of large-strain cyclic plasticity and also the stress-strain responses at small-scale re-yielding after large prestrain. A new equation of backstress evolution is proposed for an accurate simulation of the transient Bauschinger effect. Furthermore, an original idea of a non-isotropic-hardening surface defined in the stress space is presented for the description of the workhardening stagnation appearing under reverse deformation, as well as the strain-range and mean-strain dependencies of cyclic hardening characteristics. The validity of this model is confirmed by comparing the cyclic stress-strain responses calculated by the model with the experimental observations on some steel sheets and an aluminum sheet. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0749-6419(01)00050-X

Web of Science

CiNii Article

researchmap

Investigation of cyclic elasto-plastic behavior of copper sheet

Takeshi Uemori, Fusahito Yoshida

Key Engineering Materials   233-236 ( I )   287 - 292   2002

　More details

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

The cyclic plasticity behavior of an anisotropic copper sheet metal was investigated by performing in-plane tension-compression experiments. In this copper sheet, the cyclic stress amplitude of a specimen of rolling direction is apparently larger than that of the transverse direction. In order to describe such anisotropic workhardening characteristics in cyclic plasticity, as well as the Bauschinger effect, the new version of Yoshida-Uemori model, which incorporates Gotoh's quadratic yield function of the orthotropic anisotropy, was employed. The cyclic stress-strain responses calculated by this model shows in good agreement with the experimental observations.

Scopus

researchmap

軟鋼板の大ひずみ繰返し塑性変形挙動とその構成モデル

塑性と加工   30 ( 338 )   358 - 364   2001

　More details

researchmap

Plasticity Models Describing the Bauschinger Effect and Yield-Point Phenomena

INZYNIERIA MATERIALOWA   974?980   2001

　More details

researchmap

FE analysis of springback in hat-bending with consideration of initial anisotropy and the Bauschinger effect

T Uemori, T Okada, F Yoshida

ADVANCES IN ENGINEERING PLASTICITY, PTS 1-2   177-1   497 - 502   2000

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

This paper demonstrates how strongly the analytical prediction of springback is influenced by the description of material's stress-strain responses appearing during stress reversal. For the finite element analysis of hat-bending and the subsequent springback, three different types of constitutive models, i.e., (a) isotropic hardening (IH) model, (b) linearly kinematic hardening (LKH) model, and (c) combined hardening (IH+LKH+non-linearly kinematic hardening [NLKH]) model, were employed. When using the combined hardening model, the calculated sheet geometries showed the excellent agreement with the experimental results, while the predictions by both the IH and LKH models underestimate the springback.

Web of Science

researchmap

Simulation of springback in V-bending process by elasto-plastic finite element method with consideration of Bauschinger effect

T Uemori, T Okada, F Yoshida

METALS AND MATERIALS-KOREA   4 ( 3 )   311 - 314   1998

　More details

Language：English   Publishing type：Research paper (scientific journal)   Publisher：KOREAN INST METALS MATERIALS  

This paper presents the prediction of springback in sheet metal forming in terms of the description of the Bauschinger effect. It addresses three different types of constitutive models: an iso-tropic hardening model (IH model), a linearly kinematic hardening model (LK model), and a model of combined linearly-nonlinearly kinematic and isotropic hardening (L-NK+IH model). The springback predicted by the L-NK+IH model is found to be more pronounced than that by the III and the LK model. It is caused by the stress-strain response characterized by the gradual transition from fully elastic to plastic behavior during stress-reversal, which is essential to the L-NK+IH model.

Web of Science

researchmap

Prediction of active slip system for commercially pure titanium sheet by crystal plasticity finite element analysis

Takeshi UEMORI, Naoya TADA, Junji SAKAMOTO, Masatoshi DOI

Extended abstract of The Advanced Technology in Experimental Mechanics and International DIC Society Joint Conference 2023 (ATEM-iDICs '23)   19-G05   1900

　More details

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap