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To clarify the effect of steel strength on the frictional behavior during press forming, frictional coefficient and galling property were studied with cold rolled steel sheet. Frictional coefficient was measured by single sliding test. Critical contact pressure above which the frictional coefficient decreased sharply was observed to increase with the strength of steel. A repetitive sliding test under the same compressive force was introduced to evaluate galling property. It is shown that the galling property is controlled by the ratio of contact pressure to yield strength of steel, and the galling property of high strength steel is better than that of mild steel if the initial contact pressure is the same. It is also notable that galling property becomes better as the increase of frictional coefficient with the number of slide becomes smaller.

The effects of strain rate on the deformation behavior of steels were investigated to find the most appropriate micro structure of steel for anti-crash parts of automobiles, such as front-side-members. The dual phase steel absorbed a higher amount of energy during dynamic deformation than other steel with the same static yield strength. The increase of volumetric fraction of the austenite phase in the dual phase steel deteriorates the dynamic deformation behavior. The FEM analysis for crash test of member also showed the superior performance of the dual phase steel.

The effects of strain rate on the deformation behavior of several steels were investigated to find the most appropriate material for anti-crash parts of automobiles, such as front-side-members. Dual phase steel, TRIP steel, and work hardened steel showed higher dynamic to static yield strength ratios than solid-solution hardened steel. The dual phase steel absorbed a higher amount of energy during dynamic deformation than other steels with the same static yield strength due to its high strain rate sensitivity and high work hardening coefficient during dynamic deformation.