Fatigue Strength of Hot-Rolled High Strength Steel Sheet with Shearing Edge (Part 2 Improvement of Fatigue Strength by Shaving Process)

Abstract

For the application of high-strength steel plate to an automobile chassis, prevention of fatigue failure is one of critical issues in terms of its reliability. In the manufacturing, the shear cutting process with a die is commonly used because of the economic efficiency. However, it has a drawback that the shearing edge provides cracking sites in fatigue. Although the shaving process, which removes the highly-deformed layer on the surface of shearing edge, is promising candidate to improve the fatigue strength, it has not been investigated systematically. Then, the fatigue experiments is conducted on a high-strength steel sheet with the shearing edge focusing on the effect of shaving. The results elucidate that the decrease in the tensile residual stress on the edge by the shaving improves the fatigue strength. In detail, the stress re-distribution during the fatigue contributes the reduction of residual stress as well. On the other hand, the surface roughness enhanced by an inappropriate shaving process degrades the fatigue strength.