研究者詳細 - 多田　直哉

EBSD法による多結晶銅の引張塑性変形における活動すべり面に関する検討

その他リンク： https://jlc.jst.go.jp/DN/JALC/00229769016?from=CiNii

近藤了嗣, 阿部武治, 多田直哉, 清水一郎

日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A 69 ( 681 ) 924 - 931 2003年5月

記述言語：日本語出版者・発行元：一般社団法人日本機械学会

Relationship between the slip line and the orientation of grains in polycrystalline copper during tensile plastic deformation is studied. Slip plane of each grain is calculated from the orientation obtained using EBSD technique, and the slip line of specimen surface is observed by SEM image. A method of estimation of active slip plane in each grain of polycrystalline copper during tensile plastic deformation is proposed based on the experimental results. Direction of slip line is calculated from the geometrical relationship between the specimen surface and the slip plane whose orientation is obtained using EBSD method. The estimated results and the observed results are compared by use of their correlation factor. The constraint between grains in the normal direction to the specimen surface is expected to be smaller than that between grains in the surface plane. Namely, the active slip plane is decided from the condition that the component of the specimen inward direction or the direction on the specimen surface of the shearing stress on the slip plane is maximum. It is also shown that the small size grain deforms on the slip plane whose orientation is close to the active slip plane of the neighboring grain with the maximum size. The estimated results are in good agreement with the experimental results.

DOI： 10.1299/kikaia.69.924

直流電位差法による半楕円表面き裂の寸法, 形状および位置の推定査読

その他リンク： https://jlc.jst.go.jp/DN/JALC/00208632522?from=CiNii

Numerical Simulation of the Microscopic Damage progress in Type IV Creep Failure of Low Alloy Steel Welds 査読

T.Igari, F.Kawashima, T.Tokiyoshi, N.Nishimura, N. Tada

Proc. Seventh Workshop on the Ultra-Steel, "Ultra Steel: Requirements from New Design of Constructions", National Institute for Materials Science 2003年

Orientation change measured by the EBSD method and the plastic deformation of grains in polycrystalline copper 査読

T Abe, R Kondou, N Tada, Shimizu, I

ENGINEERING PLASTICITY FROM MACROSCALE TO NANOSCALE PTS 1 AND 2 233-2 535 - 540 2003年

Observation of the tensile deformation behavior of polycrystalline titanium with the scanning probe microscope 査読

T Abe, Y Li, N Tada

ENGINEERING PLASTICITY FROM MACROSCALE TO NANOSCALE PTS 1 AND 2 233-2 529 - 534 2003年

Advanced Creep Damage Analysis of Low-Alloy Steel Welds Considering the Microscopic Damage Progress 査読

Fumiko Kawashima, Takumi Tokiyoshi, Toshihide Igari, Akira Shibashi, Naoya Tada

Proc. International Conference on Advanced Technology in Experimental Mechanics 2003, The Japan Society of Mechanical Engineers 2003年

Observation of creep cavity growth in smooth and notched specimens of low alloy steel in the heat-affected zone 査読

N Tada, H Maruyama, T Igari, F Kawashima

STRUCTURAL INTEGRITY AND MATERIALS AGING 113 - 118 2003年

Fatigue Fracture of Third Generation Nickel-Base Single Crystal Superalloy CMSX-10 at High Temperature -Acceleration of Cracking by Stress Hold- 査読

Naoya TADA, Ryuichi OHTANI, Masanori SHIBATA, Shigeaki TANIYAMA

Proc. Fourth Japan-China Bilateral Symposium on High Temperature Strength of Materials, The Society of Materials Science, Japan 2001年

Prediction of Inner Cracking Behavior in Heat-Resistant Steel under Creep-Fatigue Condition by Means of Three-Dimensional Numerical Simulation 査読

TADA N.

IUTAM Symposium on Creep in Structures, (2001) 2001年

Mesurement of cavities and evaluation of creep damage parameters 査読

N Tada, R Ohtani

PROCEEDINGS OF THE SEM IX INTERNATIONAL CONGRESS ON EXPERIMENTAL MECHANICS 409 - 412 2000年

多田直哉, 中山英介

非破壊検査 48 ( 10 ) 697 - 704 1999年10月

AS4/PEEKの横方向引張における微小き裂の発生と停留

江嶋恒行, 小泉匡永, 多田直哉, 北村隆行, 大谷隆一

材料 48 ( 9 ) 1022 - 1028 1999年9月

記述言語：日本語出版者・発行元：社団法人日本材料学会

In order to investigate the fracture process of CFRP with high toughness, a plate specimen of a uni-directionally reinforced AS4/PEEK is subjected to transverse tension at room temperature. The results obtained are summarized as follows ; (1)At 83% of fracture stress, small cracks are initiated along the interfaces of fiber and matrix in a group on or near the edge of specimen. (2)The cracks are semi-circular and they are arrested just after the initiation. (3)Although the number of the cracking regions increases as the applied stress increases, the area of each cracking region does not grow due to the crack arrest. (4)The boundary element analysis and the finite element analysis reveal that the arrest is caused by the cylindrical shape of the interface. (5)The cracks restart to grow and make coalescence when the stress field near the crack tip satisfies the condition of crack kinking. (6)The main crack formed brings about the specimen breaks down when the stress intensity factor reaches the macroscopic toughness, which is evaluated by DCB specimen.

DOI： 10.2472/jsms.48.1022

その他リンク： https://jlc.jst.go.jp/DN/JALC/00063348118?from=CiNii

多数球形欠陥まわりの直流電位場解析

多田直哉, 中山英介, 北村隆行, 大谷隆一

日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A 65 ( 632 ) 693 - 700 1999年4月

記述言語：日本語出版者・発行元：一般社団法人日本機械学会

A method for evaluating the distribution of electrical potential around multiple spherical defects was proposed. As the method is based on the known solution for a single defect, the electric field can be efficienly analyzed in comparison with the other methods, such as the finite element method. The electric field in a conductive material with multiple spherical defects at random locations is estimated by the method. The analysis shows that the increase in the potential difference normalized by the potential difference without defects, ΔV/V₀, is in proportion to the product of the volumetric density of defects and the mean of cubed defect radius, n_v [r³]_m. The universal relationship is independent of the location of defects and the distribution of defect radius. Thus, the damage due to the multiple defects can be evaluated by the increase in potential difference.

DOI： 10.1299/kikaia.65.693

横方向引張を受ける複合材料の端部微小き裂に関する応力解析

その他リンク： https://jlc.jst.go.jp/DN/JALC/00059919001?from=CiNii

江嶋恒行, 多田直哉, 北村隆行, 大谷隆一

日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A 65 ( 631 ) 538 - 544 1999年3月

記述言語：日本語出版者・発行元：一般社団法人日本機械学会

Stress analysis was conducted for a transversely reinforced composite laminate with an edge crack in the matrix or along an interface by the boundary element method (BEM). The laminate is submitted to the tensile stress perpendicular to the laminate in plane strain condition. The results obtained are summarized as follows ; (1) When the laminate is composed of such two materials as don't show the free edge effect, the stress intensity factor (SIF) for a small edge crack coincides with that for a small inner crack. (2) In the case that the free edge effect is remarkable, when a crack is very small (or thort), the change in normalized SIFs, K₁ (K₁=K₁/K_lh, K_lh is SIF for a crack in a homogeneous orthotropic body) for a matrix crack and K₁, K₂ and K₁ for an interface crack depend on the magnitude of stress singularity by free edge effect. (3) As a crack becomes larger (or longer), K₁ for a matrix crack and K_i for an interface crack tends to converge on the constant values. The convergent values are calculated by the energy release rate for a crack in the homogeneous orthotropic body which has the same elastic constants as those of the composite macroscopically. (4) The magnitude of SIF for a small edge crack can be calculated by the stress distribution near the edge without a crack.

DOI： 10.1299/kikaia.65.538

常圧焼結窒化けい素の高温における引張, クリープ, 疲労, クリープ疲労破壊(<特集>高度強度)

その他リンク： https://jlc.jst.go.jp/DN/JALC/00059805069?from=CiNii

多田直哉, 北村隆行, 大谷隆一, 木倉真, 田中豊延

材料 48 ( 2 ) 173 - 180 1999年2月

記述言語：日本語出版者・発行元：社団法人日本材料学会

In order to investigate the fracture process of a sintered silicon nitride at high temperatures, tensile, static creep, and fatigue tests were carried out at temperatures from room temperature up to 1573K, and the fracture surface of each specimen was carefully observed by means of optical and scanning electron microscopes. Fracture of the silicon nitride can be classified into two types from the viewpoint of cracking morphology. One is"single cracking type"where only a single crack brings about the fracture. As the crack is initiated at the largest pre-existing defect, distribution and size of the defects greatly affect the fracture strength. The other is"multiple cracking type"where several cracks were observed on the fracture surface as well as on the specimen surface. As the cracks are initiated by viscous sliding of grassy phase along grain boundaries, pre-existing defects affest little the fracture strength. The latter type is apt to appear in the tests with lower tensile stress or lower stress rate at higher temperature.

DOI： 10.2472/jsms.48.173

複合材料における微視き裂から巨視き裂への遷移 (界面き裂を有する横方向積層板のBEM解析)

その他リンク： https://jlc.jst.go.jp/DN/JALC/00059446088?from=CiNii

Evolution of creep-fatigue damage in type 304 stainless steel and its detection by electrical potential method

N. Tada, T. Kitamura, R. Ohtani, E. Nakayama

Acta Metallurgica Sinica (English Letters) 11 ( 6 ) 463 - 469 1998年

江嶋恒行, 坂口昌平, 多田直哉, 北村隆行, 大谷隆一

日本機械学会論文集. A編 63 ( 615 ) 2338 - 2344 1997年11月

記述言語：日本語出版者・発行元：一般社団法人日本機械学会

Stress analysis was conducted for a traversely reinforced composite plate with an interface crack at the center under tension in plane strain condition by the boundary element method (BEM). The results obtained are summarized as follows ; (1) When the normalized crack length, a=a/d, (a : crack length, d : thickness of matrix layer) is much smaller than unity, the magnitude of stress intensity factors (SIFs), K₁, K₂, and K_i=(K²₁+K²₂)^1/2, are close to the SIFs for an interface crack in a dissimilar infinite body. The crack is termed as the small crack for composite materials. (2) As a becomes larger, the normalized SIF, K_i decreases and shows the minimum near a=1, where K_i is the SIF, K_i, divided by the SIF for a homogeneous orthotropic body composed of a Mode I crack, K₁h. It increases and converges on a constant value as a increases. (3) The energy release rate calculated from the convergent K_i coincides with that of the crack in a homogeneous orthotropic body where the elastic constants are determined by a mixture of those in the matrix and fibers. The crack is termed as the large crack for composite materials. (4) Since the region of oscillated stress distribution is confined in the vicinity of the crack tip, the stress intensity is represented by K_i, of which values are nearly equal to the SIF of the large crack in a homogeneous orthotropic body.

DOI： 10.1299/kikaia.63.2338