햄머피닝처리에 의한 면외 거셋 부재의 피로수명 향상

Abstract

There are several cracks near welded joint of steel structure that occurred because of repeated load which is defined as fatigue failure. Fatigue strength of welded joint affects durability of welding structure and fatigue strength is extremely low in comparison to steel plate without a sound welded joint. Fatigue strength is lower near welded area because tensile regidual stress and stress concentration can’t be removed completely or displaced. Stress concentration of gusset welded joint and regidual stress problem will not be solved unless the use of welded joint post-process. There are three ways to improve fatigue strength; Improving weld toe shape to reduce stress concentration near welded joint of steel members, mitigating tensile regidual stress near welding zone, and adopting regidual compressive stress. In this paper, we have been using a hammer penning process for fatigue testing to see improvement of fatigue life. To apprehend the geometric shape chage of welded toe according to the hammer peening treatment, the flank angle and the curvature radius were measured along with the change of residual stress. As the measurement result of geometric shape, the curvature radius increased by 43% when compared with the as-welded specimen. As the measurement result of residual stress, it was found that the tensile residual stress was reduced and the residual compressive stress was introduced near the toe by the hammer peening treatment.