Effect of Laser Peening on Improving Fatigue Strength of Welded Rib of High-Strength Steel

Abstract

Laser peening can introduce compressive residual stress to the surface and, therefore, is effective in enhancing the fatigue strength. This study targets 780 MPa grade high-strength steel (HT780) in order to clarify whether laser peening generates compressive residual stress on the surface of HT780, and whether such stress would account for prolonged fatigue life in the welded zones of HT780. As a result, large and deep compressive residual stress was generated on the base metal surface and at the boxing toe of HT780 under the peening conditions employed for 490 MPa grade steel. The smaller the applied stress range, the greater was the improvement of the fatigue life of the high-strength steel boxing toe by laser peening.