The impact welding was performed for several kinds of metal plate couples. The joint interface exhibited a sinusoidal wave form when two metal plates with the same or similar density (e.g.Al/Al, Cu/Cu and Cu/Ni) were impact-welded by high-speed oblique collision. In contrast, as for dissimilar metal plate couples with large density difference such as Al/Cu, an asymmetric wavy interface was obtained. In order to make clear the reason for morphological difference, a computer simulation of the collision behavior was performed using SPH (Smooth Particle Hydrostatic) method. The simulation results revealed that the wave form was controlled by the interaction between the emitted metal jet and metal plate surfaces ahead of the collision point. For Al/Al and Cu/Ni, the emitted metal jet hit each surface alternatively and this resulted in symmetrical wavy interface formation. While, for Al/Cu, the metal jet was emitted to the direction parallel to the Cu plate, and the interaction took place between the metal jet and the Cu plate surface. The metal jet emission and wavy interface formation mechanism were also investigated.

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Recent studies predict that Nankai-Trough earthquake to be a huge one. As a mitigating measure, passive dampers are widely adopted to control structural vibrations of buildings. These devices work effectively against the inter-story shear deformation of the building frame. In contract, they are less effective when building deformation is mainly characterized as flexural or bending deformation. It is, therefore, important to study the effective damper deformation in order to evaluate vibration control performance. This paper aims to clarify the relationship between the effective damper deformation and damper ductility demand when the damper works effectively.

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