INFLUENCE OF STEEL STATIC STRENGTH ON FATIGUE STRENGTH OF WEB-GUSSET WELDED JOINTS WITH UIT

Abstract

 Experimental researches have confirmed that UIT (Ultrasonic Impact Treatment) gives excellent fatigue strength enhancement in welded joints. The main factor in increasing the fatigue strength by UIT is the introduction of compressive residual stress rather than the improvement of weld toe shape. Further improvement of fatigue strength is expected by introducing high compressive residual stress which can be realized by increasing the static strength of steel.
 The purpose of the present study is to clarify the influence of static strength of steel on the fatigue strength of web-gusset welded joints with UIT. For this purpose, fatigue tests on the joint specimens made of SBHS400, SBHS500 and SBHS700 steel and treated by UIT have been performed, and fatigue crack initiation and propagation behavior and crack opening-closing behavior due to the compressive residual stresses have been examined.