In general, internal cells are required to solve thermo-elastoplastic problems using a conventional boundary element method (BEM). However, in this case, the merit of BEM, which is the easy preparation of data, is lost. The conventional multiple-reciprocity boundary element method (MRBEM) cannot be used to solve the thermo-elastoplastic problems, because the distribution of initial strain or initial stress cannot be determined analytically. In this paper, it is shown that three-dimensional thermo-elastoplastic problems can be solved without the use of internal cells, by using the triple-reciprocity boundary element method. Initial strain formulations are adopted and the initial strain distribution is interpolated using boundary integral equations. A new computer program was developed and applied to several problems.

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In this paper, theoretical analysis for a cantilever beam subjected to shear and compression under large scale of plastic deformation (=plastica) is pressented, and applied to the estimation of energy absorption capacity for micro-lattice structure (BCC). The precision for estimating the compressive behaviour of BCC structure depends on the stress and strain relationship just after plastic yielding. Also, based on the theoretical result, approximate equation for the average stress σ_<ave> at densification is proposed, and checked the effectiveness of the approximation by comparing with FEM numerical results.

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The present study addresses the constitutive model of cloth using anisotropic hyperelastic materials and its implementation into a nonlinear finite shell element in order to simulate large deformation behavior of cloth. Present work focuses on a macroscopic continuum constitutive model able to capture the appropriate mechanical behavior of cloth, which is characterized by two families of yarns, i.e., warp and weft. Hyperelasticity allows the formulation of large deformation including the anisotropic effect by using a structural tensor which consists of fiber-directional unit vectors. In order to avoid non-physical behavior, the related strain-energy function must be polyconvex. The polyconvexity of a strain-energy function insures the existence of the global minimizers for the total elastic energy. In this paper, interaction effect of each fiber is accounted for using weight factors of the principal material directions in order for the accurate and robust modeling of clothing behavior. The present material model is implemented into a four-node shell element in Abaqus/Standard (S4R Type) via user-subroutine UMAT, and it is used to predict the outcome of uniaxial tensile tests and compute the clothing pressure applied to human body to design a form of cloth which better fits the human body.

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Neutron stress measurement method is useful for determining, in a non-destructive inspection, the internal stress of engineering parts. However, there is a limitation such as the measurement is difficult if the path length of neutrons in the material exceeds 40〜50mm. As Webster et al. have stated adopted, cutting a sample is unavoidable in order to decrease attenuation in neutron intensity. The problem is, however, how the stress release should be considered. In this analysis, the finite element method (FEM) was applied to estimate the initial stress state using stresses released after cutting a sample obtained by the neutron method. Railway wheels were studied in this experiment. In the early 1990s, on several railroads in the northeast of the U.S.A. the wheels of the commuter trains experienced extensive cracking. Residual hoop stresses play an important role in the mechanism of fatigue damage. This paper will discuss residual stress in manufactured wheels. The results of FEM analysis were used to evaluate the residual stress. The validity of the results of the FEM analysis was evaluated by X-ray and neutron diffractions.

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In order to investigate the elastic behavior of TiNi shape memory alloy (SMA), Young's modulus (E) and Poisson's ratio (ν) of TiNi SMA during a martensitic transformation process were measured by two methods using mechanical strain gauge and electromagnetic acoustic transducer (EMAT). In particular, EMAT is able to measure the E and ν of materials under static loading condition. As the results, E and ν measured by two different methods were almost the same values. The correlation of E obtained by EMAT and by the stress-strain diagram under a martensitic transformation process was become clear.

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In this paper, we describe a method for three-dimensional high accurate analysis of a crack included in a large-scale structure. The Enriched Free Mesh Method (EFMM) is a method for improving the accuracy of the Free Mesh Method (FMM), which is a kind of meshless method. First, we developed an algorithm of the three-dimensional EFMM. The elastic problem was analyzed using the EFMM and we find that its accuracy compares advantageously with the FMM, and the number of CG iterations is smaller. Next, we developed a method for calculating the stress intensity factor by employing the EFMM. The structure with a crack was analyzed using the EFMM, and the stress intensity factor was calculated by the developed method. The analysis results were very well in agreement with reference solution. It was shown that the proposed method is very effective in the analysis of the crack included in a large-scale structure.

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This paper describes the application of a hierarchical neural network to the positioning of crack arrester with the crack propagation analysis. The present method has three steps. Firstly, crack propagation analyses are performed to assemble the data for neural network learning. Secondly, the neural network is learned using the back-propagation method and the assembled data above. Finally, the positioning of crack arrester is done using the learned neural network. The result shows that the proposed method can predict the exact position of crack arrester more than 97% cases.

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Plane bending fatigue test was performed using magnesium alloy AZ31 rolled plate whose mean grain size was 106μm. A small hole was introduced in the centre of a specimen as a crack starter notch and a fatigue crack initiated from the notch was monitored by optical and atomic force microscopes. The crystallographic orientations of grains on fatigue crack growth path were measured by an Electron Backscatter Diffraction (EBSD)method in advance, and the effect of grain orientation on small fatigue crack growth behaviour was discussed. The fatigue crack growth behaviour was strongly affected by grain orientations. Transgranular fatigue crack tended to grow due to slip deformation along the basal slip plane whose Schmid factor was relatively large. When the Schmid factors of the basal slip system were very small, the crack grew with the activation of the cylindrical slip systems. Twining deformation exerted a little influence on the crack growth behaviour. The crack growth rates were slower when the crack growth was due to slip deformation along the cylindrical slip planes.

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Clinching is a mechanical joint for fastening sheet metal components, and it is widely used in automotive industry. In this paper, the application of mechanical clinching to a built-up aluminum beam is studied. At first, tensile-shear tests and fatigue tests are carried out on clinched joints of 6063-T5 aluminum alloy sheet to investigate the tensile-shear strength and fatigue strength. Then, based on the joint strength results of clinched joint, the joint pitch of the built-up beam is designed under the specified bending load. Lastly, static bending test and cyclic bending test are carried out on the built-up beam to investigate the deformation behavior and the flexural rigidity. It is found that load-deflection relation and load-bending stress relation of the built-up beam are equal to those of one type beam calculated from Euler-Bernoulli beam theory. The built-up beam is proved to have the same flexural rigidity as that of one type beam. Cyclic bending test results show that cyclic loading gives no influence to clinched joints and the flexural rigidity of the built-up beam. All results demonstrate that mechanical clinching is an effective connection method in a built-up beam.

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For guaranty of quality of the non-based adhesive sheet such as adhesive used in flat panel display (FPD), damage of adhesive in a laminate process should be clarified. Standard peel tests are not suitable for evaluating the interfacial strength because measured peel force includes other influences of peeling. In this paper, the peel strength is measured in the range from 30 to 180 degrees of the peel angle and 20 to 1000mm/s of peel rate by using two-axes-driven peel method developed. Unstable peeling occurred in the case of small peel angle while the failure of adhesive layer occurred in case of high peel rate. Peeling behavior map is constructed from the results of two-axes-driven peel test. It is shown that the results obtained by the Y-type peel test coincide with the classifications of the peeling behavior map.

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Nanoindentation tests were conducted for polyimide (PI) coating/Si substrate specimens and the energy release rates were evaluated as the interfacial strength. The energy release rate due to a coating delamination was obtained from the load-displacement curve by the method proposed by Omiya et al. The correcting method was proposed for the case that the energy dissipation due to the viscosity of materials occurs. Three specimens that have different thickness were prepared. The dependencies on the coating thickness and delamination propagation rate were investigated. The interfacial strength of the thinnest coating case is underestimated, since small scale yielding conditions were not satisfied. The value of the interfacial strength between PI coating and Si substrate increases with increasing of the delamination propagation rate. The value becomes constant when the delamination propagation rate exceeds around 7.0×10^<-3>mm/s. On the other hand, the critical strain intensity factor is constant irrespective of the delamination propagation rate. This result suggests that the opening displacement at the delamination edge is constant for the range of the propagation rate investigated.

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Using a time-domain spectroscopic technique based on the generation and detection of a collimated beam of subpicosecond broadband terahertz pulses, we measured frequency-dependent electrical properties of doped silicon in the terahertz wave range of 0.1-1.2THz. These results are well fit by Drude theory. It is shown that carrier density can be evaluated well by the suggested method.

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When jointed portions of structures and machines are subjected to thermal loads, various problems and troubles occur due to the difference in thermal expansion between mating parts. In order to accurately analyze thermal and mechanical behaviors of the joints, the effect of thermal contact resistance must be taken into account. In this paper, thermal contact coefficient, which is the reciprocal of thermal contact resistance, at the interface composed of dissimilar materials is quantitatively measured by infrared thermography. The target materials are common engineering materials such as carbon steel, stainless steel and aluminum alloy. It has been shown that there exits a significant direction effect in thermal contact coefficients when the mating surface is composed of different materials. That is, the magnitude of the coefficient gives larger value when the heat flows from the material with lower thermal conductivity to the one with higher thermal conductivity. Also, the effects of contact pressure and surface roughness are evaluated. An empirical equation to estimate thermal contact coefficient is proposed, which can approximate the experimental values with sufficient accuracy from the engineering point of view.

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An Analytical model for describing the mechanical behavior of a bolted joint subjected to a transverse load has been theoretically formulated. This paper focuses on the load-displacement relation. The transverse displacement is separated into five factors: (a) bolt bending due to a transverse force acting on the thread surface, (b) bolt bending due to the thread-surface reaction moment, (c) inclination of the bolt head, (d) thread surface slip, and (e) bearing surface slip. Contact force and slip displacement are newly modeled in order to describe (d) and (e). Contact surfaces are discretized into meshes. The contact force acting on each mesh is formulated by taking into account the helical profile of the thread. The slip criterion is judged according to the Coulomb friction law. In order to maintain a mechanical equilibrium, the contact force and contact state are calculated in a self-consistent manner. As for the interaction between the thread and bearing surfaces, torque induced on the thread surface is transmitted to the bearing surface in a model of bolt torsion, relevant to the loosening rotation. The mechanism by which the reaction moment, which affects (b) to (e), is induced on the thread and bearing surfaces is also investigated. We found that the inclination of the bolt affects the reaction moment during localized thread-surface slip, while the transverse displacement of the bolt affects that during the complete thread-surface slip. The reaction moment is formulated to be proportional to the stiffness of the thread and bearing surfaces. Finally, our analytical model is applied to an M16 bolted joint and confirmed that our model agree well with the FEM result.

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