This paper is concerned with stability of the uniaxial, biaxial and flower-like buckling modes of honeycombs subject to in-plane biaxial compression. One of the three buckling modes is forced to exclusively develop at multiple bifurcation points by imposing appropriate constraints on the field of microscopic velocity. Then, the internal energies generated are compared for discussing which mode is stable. Either macroscopic strain or macroscopic stress is controlled to induce microscopic buckling in computation. The followings are thus found: Under the biaxial compression in which double bifurcation occurs, the biaxial mode is stable under the two controlling conditions. Under the equi-biaxial compression in which triple bifurcation occurs, the flower-like mode is stable under macroscopic strain control, whereas the uniaxial and biaxial modes are stable under macroscopic stress control.

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The present study has attempted to simulate the distribution of α'martensite and vertical magnetic flux density B_z around the plastic wake of a growing crack in an austenitic stainless steel SUS304 in which stress-induced martensitic phase transformation is to occur at room temperature. FEM calculations of martensitic phase transformation have been made on a center-cracked plate specimen of SUS 304 stainless steel subjected to monotonically increasing tension load at room temperature. The resultant contour maps of α'martensite around fatigue cracks agree well with those measured by ferrite scope, showing that the distribution of α'martensite changes according to the applied maximum stress intensity factor K_<max> value. FEM calculations also have been made on the vertical component of leakage magnetic flux density above fatigue cracks by using a composite permanent magnet model. The α'transformation region around a fatigue crack is modeled as a composite of permanent magnets having different B-H properties varying with to α'content. The resultant distributions of leakage magnetic flux density above fatigue cracks obtained by FEM agree well with those obtained experimentally.

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The perforated plate has strain concentration near the holes, and failure initiates from this point after fatigue and creep damages. Thus, the accurate estimation procedure is required to obtain strain amplitude under repeated loading histogram at elevated temperature. The stress locus method proposed by Kasahara and Shimakawa is based on elastic creep analysis. where the almost same stress-strain locus was obtained for typical nuclear plants. The present paper describes the mechanical feature of plate with holes to obtain this stress-strain locus from elastic plastic analysis. This locus depends on the geometry and loading condition of the problem leading to the introduction of inelastic analysis in design procedure.

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A spring - link model is presented to cope with the own - weight buckling of a long column under various boundary conditions such as clamp-clamp, simply supported-clamp and so forth. In doing so, an equality constraint condition should be incorporated in order to satisfy the condition that the both ends are located on a same vertical line. This paper deals with the formulation of the eigenvalue problem under the equality constraint condition. The numerical examples are concerned with the critical length of aluminum columns under several boundary conditions, which agree well with the result of the closed-form solution.

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Stress estimation method using the dynamic hardness testing was analytically investigated. The FEM stress analysis was performed by the ABAQUS code in two-dimensional plain-strain condition taking into account of the material non-linearity with surface element. The Vickers indentor made of diamond was modeled as a rigid body in the analysis. The indentor was pressed on the body with several kinds of pre-stressed conditions in tension and compression to clarify the detectability of the stress (strain) condition by the dynamic hardness testing. The obtained dynamic hardness was compared with experimental data as a function of pre-stressed condition. From this study, it was found that the dynamic hardness increases with increasing compressive pre-stressed condition and decreases with increasing tensile pre-stressed condition. Therefore, it is concluded that the dynamic hardness testing aiming at the stress measurement is applicable to the measurement of complex stress profile with tensile and compressive stresses.

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