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Weldable vibration damping steel sheet consists of two skin steel sheets and viscoelastic resin film that contains filler metal powder to get electric conductivity. In this study, it is investigated the effect of filler powder (type; size and content) on weld defects. The defects are observed when the resin layer is thick comparing with the powder diameter or the content of metal powder is insufficient. The defect with bare skin sheets which is spherical hole is caused by joule overheating. Another defect is observed when Zn-Fe coated skin sheets are used. According to the observation of welding current and voltage wave forms. It is formed by an arc electric discharge between metal powder and skin sheet, which is caused by cutting off current paths due to the evaporation of Zn-Fe coated layer. Based on these results, it is determined the suitable filler powder to produce VDSS with good weldability.

Vibration Damping Steel Sheet (VDS), which is composed of two steel-sheet skin layers and a middle layer of viscoelastic polymer resin, has been applied to automotive parts. For application to body panels, VDS needs several superior characteristics, such as, high damping capacity at room temperature and spot weldability as well as press formability. VDS developed by sandwiching a thermosetting resin has the loss factor of 0.2 at room temperature, and can be press formed and spotwelded under the same conditions as for an conventional steel sheet.

A new vibration-damping sheet (viscoelastic material sandwich type) for automobiles has been developed jointly by NKK and Japanese plastic maker. This product has high damping capacity and good press formability eqaul to normal steel sheets, because this product uses the hard viscoelastic material which has good adhesion to steel sheets. The sound level shall be reduced by order of 2∼3 dB, if this product is applied to oil pans. Fatigue limit is improved as compared with early vibration-damping sheet for which the soft viscoelastic material was used. Spot welding can be done in case that an electric short circuit is used.