[in Japanese]

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[in Japanese]

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[in Japanese]

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We propose the simulation method using damage model in order to predict the discontinuities caused by the ductile fracture. Estimating the accurate shape and dimensions in metal working are required in many fields of engineering. Therefore, simulation is focus on to deal with the ductile fracture phenomena. In this study, we apply the Lemaitre damage model to simulations because this model can describe the strain softening. Moreover, we use the finite cover method since the finite element method, which is used generally needs some special technics to describe the discontinuities. We compare the calculated results by using present approach and using ANSYS APDL with use Gurson model .

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[in Japanese]

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In this report, a methodology to analyze magnetostatic field around an inner defect using a framework of the extended finite element method is presented. In this method, Joukowski mapping is used to obtain the enrich function which represents the flux distribution around an inner defect. The effectiveness of this method is verified using a numerical example.

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[in Japanese]

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Crack growth under the elastic-plastic fracture is an important issue of the structural integrity, because seismic wave causes low cycle fatigue in the engineering structure. We developed automated FEM analysis framework for elastic-plastic crack growth simulation. The framework consists of 4 major modules. In this work, we employ crack opening angle (COA) and displacement (COD) which are the angle between crack surfaces and the displacement vector to be defined near the crack tip. The present work is applied to the cyclic loading analysis of a pipe with a single notch. The work shows automated mesh generation capability and fracture mechanics parameters to evaluate crack growth criterion.

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This paper describes the crystal grain size effect of an aluminum alloy analyzed by a polycrystal plasticity FEM code the present authors have been developing. In order to analyze the crystal grain size effect, the code was modified to implement a crystal grain size effect in the initial critical resolved shear stress. The results showed that the smaller the crystal grain size, the higher the 0.2% proof stress. The relationship of calculated 0.2% proof stress to inverse square root of crystal grain size was represented by a single straight line, known as the Hall-Petch relation. The results revealed that the 0.2% proof stress was remarkably affected by grain size but that the work hardening behavior was not. It was conclude that the work hardening behavior was affected more by crystal orientation difference which can enhance the generation of dislocations.

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This paper describes the polycrystal plasticity analyses of an aluminum alloy plate by using an FEM code the present authors have been developing. Isotropic elastic moduli were assumed in ordinary polycrystal plasticity analyses so far made. In this study, however, general anisotropic elastic moduli are used in order to examine the interaction between normal stresses and shear strains and/or that between shear stresses on normal strains. The results obtained for a plate model having general anisotropic elastic moduli were compared with those for a plate model having the orthogonal anisotropic elastic moduli. It was shown that the higher the shear modulus C_<12>, the lower the macroscopic uniaxial stresses, and thus, the lower the macroscopic Young's moduli in the two types of plate models. The bending deformation of the general anisotropic plate model was observed due to the interaction between normal stresses and shear strains, although the unidirectional tensile load was applied to the plate model via an isotropic elastic chuck which can reduce the bending deformation of the plate model.

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Modified 9Cr-1Mo steel is used in the high temperature environment such as water supplying pipes in steam power plant because of its low thermal activation to maintain steady rate deformation during long-term creep. In reality, however, in a long term region of, say, 100,000 h or longer, creep rupture lives become much shorter than predicted because of the material degradation which may occur due to constraint among anisotropic crystal grains around a welded joint. This paper describes a polycrystal elasto-viscoplastic finite element code considering the damage mechanics which the present authors have developed in order to analyze long-term creep behavior of a welded joint in modified 9Cr-1Mo steel at 823K in air. The results of the analyses done by the present FE code showed that creep damage preferentially occurred in fine HAZ, which implies internal crack initiation known as Type IV cracking. The developed code reproduced abrupt decrease in the creep rupture lives at lower applied stress levels.

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H_2O adsorption on cubic ZrO_2(110) surface is analyzed by ab initio molecular dynamic simulation to discuss the hydration process and proton migration on oxide surface. Proton migration is observed on the surface, because protons are released by adsorbed H_2O molecules which work as bronsted acid and attracted by monodentate hydroxyl species as it is bronsted base.

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[in Japanese]

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