Faculty Profiles - UEMORI Takeshi

Papers - UEMORI Takeshi

Division display 1 - 20 of about 118 ／ All the affair displays >>

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

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

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

72 ( 3 ) 39 - 43 2024.12

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

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

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

J. Sakamoto, N. Tada, T. Uemori

472 2024.9

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

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

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

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

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

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

2023.8

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

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

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

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

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

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

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

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

　 PREV - NEXT 　

< UEMORI Takeshi >

Papers - UEMORI Takeshi