Fatigue failure transition evaluation of load carrying cruciform welded joints by effective notch energy model

Abstract

This paper investigates fatigue failure transition boundary of Load-carrying Cruciform Weld Joint (LCWJ) with different yield strength mismatch ratios and geometrical sizes of welded joints under cyclic loading conditions using a semi-empirical analytical method, which is based on the obtained fatigue test data and finite element analysis. To examine the fatigue failure mode transition relationship in CLWJs, different mismatch ratios and local geometries (plate thickness, weld size, and penetration ratio) were designed and fabricated to evaluate potential fatigue initiations (weld toe or weld root). The numerical simulations of cyclic responses at weld toe and weld root were conducted by material cyclic plastic properties from fatigue data of standard coupon specimens. A uniform effective notch energy indicator in the previous investigation was utilized to characterize the low and high cycle fatigue life by extending the SED method on the combination of generalized Neuber concept of Fictitious Notch Rounding (FNR). The related analytical formulations for potential failure points were used to predict the fatigue assessment indicator of LCWJ, considering the effects of plasticity and mechanical heterogeneity and geometry configurations. The effective notch energy relationship between the weld toe and weld root in LCWJ was determined by the established analytical solutions, verified by the fatigue data. The strategy is expected to provide some insights into assessing fatigue life for various types of weld joints for different potential failure locations.