In the several engineering fields, the collision between structures and foreign objects involve some difficulties in the numerical treatment because intensity, contact area and the time history of the impact load are not known. Some experimental techniques have been suggested to measure the distributed load by a piezo-electric sensor. However, such a direct measurement often meet with difficulty, because the geometry or rigidity of the contact surface may be altered by attaching the sensors on the surface. In order to overcome the difficulty, this paper deals with estimation of pressure distribution applied to the elastic body using inverse analysis. In the present study, the coefficient matrix is introduced which gives linear relation between distributed load and internal strain. The coefficient matrix can be determined by experimentally measured data of strain produced by concentrated loading. In order to increase the accuracy of the identified pressure, regularization technique suggested by Kubo is employed to stabilize the solutions. A numerical simulation on the circular plate subjected to transverse distributed loading is conducted to demonstrate the effectiveness of the present method.

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[in Japanese]

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There is a knee point on the stress-strain curve of tensile test on woven fabric composite. It is said that initial fracture occurred at the knee point. In order to know the initial fracture behavior, evaluation of knee point by using least squares method was performed and knee point stress and strain could be evaluated quantitatively. By observation through optical microscope, fracture process was as follows; transverse crack initiated at the 1st knee point, then propagate through the weft fiber bundle at the 2nd knee point. Moreover, effect of weaving structure on initial fracture behavior was considered. It needs more energy to propagate the crack in satin woven fabric composites than in plain woven fabric due to different weaving structure.

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In these days, many bridges and offshore structures near ship's waterways are constructed. Accordingly the number of collision accidents between vessel and these structures is increasing. To prevent direct collisions various protective devices are installed around bridge piers, thereby minimizing the damage to both bridge and ship. We employed thermoplastic polyester elastomer (TPEE) in the research on putting into practical use for a more rational protective device. As a part of our basic research, we will report our tests and finite element method that used flexible soft polyurethane foam, a homogeneous elastic material. We modeled this material, which has a fine cell structure, based on the constitutive law using a strain energy function. We also tried to apply this foam model to our new TPEE protective device.

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This study is concerned with the analysis of relationship between the interfacial energy of polymer and the micro voids that are formed by stretching the composite polymer sheet having incompatible particles in the matrix. We tried to simulate the void formation, considering the interfacial delamination between Poly (ethylene terephthalate) (PET) and dispersed incompatible polymers, and to compare the numerical results by finite element method (FEM) with experimental ones. Decreasing the critical stress of delamination coincided with increasing the surface energy theoretically. Interfacial tension obtained from this experiment was related to critical stress calculated from the numerical analysis in void formation qualitatively.

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