Elastic dynamic problems including vibration problems have been fully investigated by many researchers. Although, on a static analysis of structure, the limit design is well known as a plastic analysis, elasto-plastic analysis of vibration is relatively small. A certain kind of structure may be allowable to have a small amount of plastic deformation for saving the cost, unless the plastic deformation causes a fatal damage such as collapse to the structure. Then, the study of elasto-plastic oscillatory response is useful for an actual structural design. The elasto-plastic oscillatory behavior of bar structure, which is subjected to the bending and twisting moment simultaneously, is discussed in this study.

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The tensile strength of arc fusion spliced optical fiber was reduced. This was studied from micro hardness distribution The micro hardness was declined by the arc fusion. Therefore, a new annealing device was developed. The heat treatment improved the micro hardness of the spliced area.

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The mechanical properties of copper thin films formed by cold-rolling and electroplating were compared using tensile test and nano-indentation. Both the Young's modulus and tensile strength of the films varied drastically depending on the microstructure of the films. The Young's modulus of the electroplated thin film is about a fourth of that of bulk material. The micro structure of the electroplated film was a columnar structure of a few hundred-μm wide and polycrystalline.

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The reliability evaluation for the electronic devices mainly depends on FEM analysis. But the measurement of material property spends enormous time and cost. Therefore, the technique of simplicity measuring is strongly requested. In this study, the authors used a digital image correlation method to measure displacement of solder joint and the surrounding materials. By comparing between experimental and analytical displacement results, the material properties of lead-free solder is examined.

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It is reported that there is a possibility of hydrogen embrittlement caused by the reaction between H_2O in air and aluminum alloy deformed at a slow strain rate(10^<-7>s^<-1>). In this paper, hydrogen accumulation during tensile and bending deformation of Al-Mg-Si base alloys was examined by means of Hydrogen Microprint Technique(HMT) in order to visualize hydrogen. The result of tensile test showed that both 0.2% proof stress and tensile strength decreased as the cooling rate during quenching in solution treatment decreased. As the grain size becomes small, both 0.2% proof stress and tensile strength also increased. Observation of microstructure showed that an A8 specimen where the cooling rate is 20℃/s fractured preferentially at the grain boundary, while an A8 specimen quenched in water indicated ductile fracture. The same tendency was observed between the tensile test and the bending test. Hydrogen was accumulated at slip lines near the fracture area.

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