Papers by Author: Kuniharu Ushijima

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Authors: Kuniharu Ushijima, Hironobu Nisitani
Abstract: Finite element method (FEM) is used widely for various structural problems. However, in general, it is difficult to guarantee the accuracy of results obtained by commercial software of FEM. In this paper, a practical finite element technique for calculating the stress concentration factors with high accuracy is proposed in consideration of physical meaning of stress concentration, and applied to a 2-dimentional stress problem.
797
Authors: T. Teranishi, Hironobu Nisitani, Kuniharu Ushijima
Abstract: In this study, it was made clear that the non-linear notch mechanics is useful not only in the case of uniaxial tension but also in the case of biaxial tension. The difference of both cases is as follows. In the former the plastic strain field near a notch root is determined by εp y0,FEM (plastic strain at a notch root) and ρ (notch root radius) alone, but in the latter case it is determined by εp y0,FEM, ρ and stress ratio k=σxn/σyn.
1131
Authors: Hironobu Nisitani, Kuniharu Ushijima, D.H. Chen, Akihide Saimoto
Abstract: Finite element method (FEM) is used widely for various structural problems. However, in general, it is difficult to guarantee the accuracy of results obtained by commercial software of FEM. In this paper, a practical finite element technique for calculating the stress intensity factors with high accuracy is proposed. This technique is based on the characteristics of stress field due to a crack. In this study, the proposed method is applied to 2-dimentional crack problems.
103
Authors: Dai Heng Chen, Kuniharu Ushijima
95
Authors: Kuniharu Ushijima, Dai Heng Chen, Wesley J. Cantwell
Abstract: In this study, a theoretical analysis for predicting the mechanical properties of three dimensional lattice structures under compressive loading is proposed, and verified by comparing the analytical predictions with FEM results. This theory for estimating the initial stiffness E* is based on the classical beam theory, and the one for estimating the plastic collapse strength reflects the stress state for each lattice structure. In particular, effects of inner geometry (strand’s diameter-to-length ratio and micro-architecture) on the mechanical behaviour are discussed.
1302
Authors: Kuniharu Ushijima, Wesley J. Cantwell, Dai Heng Chen
Abstract: In this paper, the shear response of three-dimensional micro-lattice structures was investigated based on numerical stress analysis, FEM. The mechanical properties strongly depend on the number of unit cell in three directions x,y,z, and for a flat structure (number of cells in y-direction Ny=1), the deformation pattern observed in the structure can be classified into two types. The shear modulus G*for a flat structure obtained by FEM can be estimated by the elementary beam theory with a good accuracy. Also, for a flat structure with slender struts, the collapse is occurred by elastic buckling, and that with relatively thicker struts, the collapse strength agrees well with the theoretical result. Moreover, for the case of the cubic structure, if the structure has the same number of unit cell in x- and z- directions (numbers of cells in two directions Nx=Nz=M), the shear modulus G* shows a unit curve regardless of the number M, so that the modulus can be estimated by using the curve for various cubic structures.
713
Authors: Kuniharu Ushijima, Dai Heng Chen, Naoto Kitte
303
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