Fatigue life estimation of in-service welded patch using several multiaxial fatigue criteria

The present research has investigated the fatigue life of in-service steel patch welded joints by experimental/numerical approaches. To this end, three types of welded panels with similar WPS but different cooling conditions were constructed. Subsequently, test samples cut from the main panels were subjected to fatigue tests. A novel approach involving continuous hardness measurement at the welding section was employed to predict the mechanical and fatigue properties of different zones in welded specimens. Firstly, the mechanical properties and fatigue parameters of various weld regions and HAZ were calculated by microhardness measurement and metallography images. Then, stress analysis was conducted in the Abaqus. The fatigue life was predicted using the stress and strain values obtained from the FE analysis, the UVARM subroutine, and multiaxial fatigue modeling codes. The life estimations obtained from the numerical models were ultimately compared by experimental fatigue test results. The experimental tests showed that the samples cooled with water at a speed of 0.5 m/s had an increase in life, and the samples cooled with water at a speed of 1.5 m/s had a decrease in life compared to the samples cooled in air. Moreover, to predict the fatigue life, Brown-Miller-Marrow and Glinka criteria were used, respectively, and the results showed that these two criteria are able to predict the fatigue life with the maximum average error of 20.16% and 34.68%, respectively.