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In order to improve the capability of frontal or rear automotive members to absorb impact energy, a basic study was performed to evaluate the effect of strength, micro-structure, and plate thickness on dynamic deformation phenomena using tensile specimens and hat square columns. Tensile strengths of the materials were selected from 340 to 1180 MPa class steels. Five kinds of micro-structure, Ferrite, Ferrite + Bainite, Ferrite + Martensite, Ferrite + Pearlite, Ferrite + Bainite + γ, and Martensite, were investigated. Tensile tests were carried out under strain rates from 10-1 to 103 /sec. and crash tests of hat square columns were conducted under test speeds from 0.1 to 14.0 m/sec.

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.

The Effects of microstructures on stretch flangeability and stretchability in hot rolled high strength steel was investigated. Stretch flangeability of multi-phase steels was inferior to that of single phase steels at a given tensile strength, although stretchability of the former was superior to that of the latter. In multi-phase steel, the main factor affecting stretch flangeability is the hardness ratio of ferrite to hard phase, on the other hand, that which most affects stretchability is the volume fraction of ferrite. According to these results, several types of high strength hot rolled steel sheets with excellent formability were developed.