Evaluation of fatigue damage at welded tube joint under cyclic pressure using surface hardness measurement

In this paper, fatigue tests were conducted on 1Cr18Ni9Ti stainless steel and its welded joints were subjected to cyclic inner pressure. During the fatigue tests, the HL hardness of base metal (BM), weld metal (WM) and heat affected zone (HAZ) were measured. The results showed that 1Cr18Ni9Ti was a cyclic hardening material and the WM was a cyclic softening material. Moreover, the fatigue damage evolution of BM was a power relationship and the fatigue damage evolution of WM and HAZ were a linear relationship. Applying Chaboche's nonlinear continuum fatigue damage model and studying on evolution of HL hardness, a damage parameter based on HL hardness and a fatigue damage accumulation model was proposed.