作者: Kwang Hwa Chung, J.S. Kim, J.S. Kim, Young Jin Kim

摘要: Based on detailed two-dimensional (2-D) and three-dimensional (3-D) finite element (FE)analyses, this paper attempts to quantify in-plane and out-of-plane constraint effects on elastic-plastic J and cracked tip stresses for biaxially loaded plate with a through-thickness crack and semi-elliptical surface crack. It is found that the reference stress based approach for uniaxial loading can be applied to estimate J under biaxial loading, provided that the limit load specific to biaxial loading is used, implying that quantification of the biaxiality effect on the limit load is important.
Investigation on the effect of biaxiality on the limit load suggests that for relatively thin plates with small cracks, in particular with semi-elliptical surface cracks, the effect of biaxiality on the limit load can be neglected, and thus elastic-plastic J for a biaxially loaded plate could be estimated, assuming that such plate is subject to uniaxial load. Regarding the effect of biaxiality on crack tip stress triaxiality, it is found that such effect is more pronounced for a thicker plate. For plates with semi-elliptical surface cracks, the crack aspect ratio is found to be more important than the relative crack depth, and the effect of biaxiality on crack tip stress triaxiality is found to be more
pronounced near the surface points along the crack front.

699

作者: N. Matsumoto, S. Ohtaki, M. Ohira, H. Kasayama

摘要: An application of the elastic-plastic problem by the photoelastic coating method is presented in this paper. A general procedure of this experiment, such as image processing and separation of the difference of principal strain to obtaine stresses from isochromatic fringes is referred. The methodology to extract centre lines of coloured isochromatic fringes is explained. Experiments are conducted with cross-shaped aluminum specimens with a circular hole subjected to uniaxial tension and equi-biaxial tension. Results of image processing are shown, and the distribution of difference of principal strains and separated principal strain are shown in the case of equi-biaxial tension.

27

作者: Chang Su Woo, Hyun Sung Park, Wae Gi Shin

摘要: The material modeling of hyper-elastic properties in rubber is generally characterized by the strain energy function. The strain energy functions have been represented either in term of the strain in variants that are functions of the stretch ratios, or directly in terms of the principal stretch. Successful modeling and design of rubber components relies on both the selection of an appropriate strain energy function and an accurate determination of material constants in the function. Material constants in the strain energy functions can be determined from the curve fitting of experimental stress-strain data. The uniaxial tension, equi-biaxial tension and pure shear test were performed to acquire the constants of the strain energy functions which were Mooney-Rivlin and Ogden model. Nonlinear finite element analysis was executed to evaluate the behavior of deformation and strain distribute by using the commercial finite element code. Also, the fatigue tests were carried out to obtain the fatigue failure. Fatigue failure was initiated at the critical location was observed during the fatigue test of rubber component, which was the same result predicted by the finite element analysis.

190

作者: Jian Wen Chen, Hong Qing Hou, Wu Jun Chen

摘要: This article presents the mechanical properties of PVC coated fabrics under biaxial cyclic tensile loads. Tests of PVC at five load ratios in the warp and weft directions, which are 0:1, 1:2, 1:1, 2:1 and 1:0 respectively, were carried out, and tensile performances of the samples under biaxial tensile loads were analyzed. The test results show that the PVC membrane is highly nonlinear and orthotropic under biaxial tensile loads. With the increase of loading cycles, the total residual strain is nearly unchangeable and the hysteresis curve becomes stable. Slope of warp curve is larger than weft curves, and the weft loop area is greater than the warp one with the same load ratio. The generalized poisson ratio changes due to variations of the load ratio (R). when R<1, the experimental values and theoretical values of the generalized poisson's ratio are negative. When R≥1, generalized poisson's ratios tend to be constant, When the load ratio are 0:1 and 1:0, the curves become straight lines.

36

作者: Huai Liang Zhu, Li Feng Yu, Jing Ni, Xue Wang, Ren An Luo

摘要: This paper is aimed at investigating the influence of load-bearing style on the mechanical behavior of anisotropic engineering materials. The study on elastic constants and failure forms of materials will be presented under different loading condition. Firstly, the mechanical properties of unidirectional holey laminated materials are discussed based on the uniaxial tensile tests. The equivalent elastic modulus, Poisson’s ratio and shear modulus are obtained, and the pattern and mechanism of failure are analyzed. Then, the biaxial tensile tests are carried out for PVC orthotropic membrane materials with different stress ratio between the warp and weft direction. A comparison of limit strengths under biaxial loadings is given with that in uniaxial loading case. Finally, the dynamical behaviors of shape memory alloy (SMA), iron wire, and rubber composite as well as compound rubber are studied respectively by impact-tension tests. The failure forms, energy dissipation ratio and impact-tension toughness of materials are analyzed. It is shown that the mechanical properties and failure pattern of anisotropic materials have much to do with the load-bearing styles. It agrees well with actual properties of anisotropic material used in engineering structures.

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