QUANTIFYING WELDING RESIDUAL STRESSES AND THEIR EVOLUTIONS UNDER CYCLIC LOADING IN WELDED CONNECTIONS

Abstract

Welding residual stresses are the nonhomogeneous trapped stresses in the welded joints which have detrimental effects on fatigue life, structural integrity, and premature failure of the structure. The primary objective of this study is to quantify welding residual stresses and their evolutions under cyclic loading in welded connections. Therefore, the scope of the thesis includes experimental and numerical studies of the as-welded residual stress and the evolved residual stress during cyclic loading tests in butt-welded plates, cruciform plate joints, pipe-to-plate joints, and CHS X-joints. Embracing the objective, the thesis covers the following aspects: 1) the experimental program of different welded joints; 2) welding residual stresses in welded S550 steel plates; 3) the effects of pre-tension and fatigue loading on the evolution of residual stress and 4) a novel optimization-improved thermal-mechanical simulation approach assisted with XRD measurements to the real complicated joints.