Multiaxial fatigue behavior and life prediction of forged Ti-6Al-4V under complex paths with mean stress

Abstract

Engineering components are often subjected to complex loading paths and high stress ratios. However, most existing multiaxial fatigue life prediction models are based on symmetrical loading tests. Their research is relatively limited on multiaxial fatigue under high stress ratios and complex loading paths. This study investigates the multiaxial fatigue behavior of forged Ti-6Al-4V alloy through a series of tension–torsion fatigue tests under high-stress ratios and complex paths. Digital Image Correlation (DIC) was employed to measure strain fields during the testing process. The results indicate that both tensile and shear mean stresses reduce fatigue life significantly. The fracture analysis showed obvious fatigue stripes on the fracture surface using Field Emission Scanning Electron Microscope (FESEM). Furthermore, this paper proposes a novel multiaxial fatigue life model that considers the different contributions of tensile and shear strain energy densities to fatigue damage. The comparison between the proposed model and commonly used models (SWT, FS, and CCB) shows that the accuracy and superiority of the new model in life prediction have been improved.