The aim of the present paper is to investigate and to compare the fatigue characteristics of butt welded joints made of high strength steel with tensile strength 700MPa. The influence of different back plate materials and the groove shapes of copper backing are investigated. Various backing methods have been used in the steel construction industries, but steel backing, which is the most frequently used, sometimes is not capable of providing sufficient fatigue strengths for welded joint, particularly for high strength steel. Therefore, alternative backing methods have been investigated in order to improve the fatigue strength by employing ceramic backing, CMT (Cold Metal Transfer) [1] and copper backing. The main objective of the work is to estimate the fatigue test results for improving fatigue strength by comparing different backing materials and groove shapes. A series of fatigue tests with different types of backings has been carried out to obtain the fatigue life of butt welded joints. It was observed that the fatigue behavior of welded joints can be substantially improved by changing back bead shapes. The result has shown that the back bead shape of copper backing is better than others except for that of CMT, accompanied by improved fatigue strength.
Influence of High Frequency Impact Treatment (HiFIT) on fatigue strength of welded joints of high-strength steel S700MC for bridges applications
