Fatigue Strength Improvement of Lap Joints of Thin Steel Plates for Automobile Use by Using Low Transformation Temperature Welding Material
Akihiko OHTA, Kazuyoshi MATSUOKA, Ninh T. NGUYEN, Yoshio MAEDA and Naoyuki SUZUKI
Abstract:The fatigue strength of lap welded joints of thin steel plate for automobile use was improved by using low transformation temperature welding material which induced the compressive residual stress around welded part. The transformation of welding material from austenite to martensite begins around 200 and finishes around room temperature. The expansion of weld metal due to the transformation was constrained by the surrounding base metal, and the compressive residual stress is induced in the as welded condition. The mean stress effect due to this compressive residual stress improved the fatigue strength. Key Words:Fatigue strength, Welded joint, Thin steel plate, Transformation, Residual stress, Improvement