A CDM‐Based Fatigue Model Incorporating the Effects of Scratches and Stress Gradients for ZM6 Magnesium Alloy Specimens

ABSTRACT Engineering structures subjected to cyclic loading often face the risk of fatigue failure. The scratches formed on the structure surface by accident may significantly reduce fatigue life. This study explores the influence of scratches on the fatigue performance of ZM6 magnesium alloy through fatigue tests and theoretical models. First, specimens with scratch depths of 0.15 mm, 0.25 mm, and 0.35 mm are fabricated to investigate the effects of scratch. Additionally, nine scratched structural component specimens are prepared to examine the collective influence of stress gradients and scratches. Second, based on experimental results and continuum damage mechanics (CDM), three equivalent factors are introduced to characterize the individual and collective influence of scratches and stress gradients. The generalized stress amplitude in the damage evolution equation is modified accordingly, eliminating the need for geometric modeling of real scratches. Through the integration method, the models are finally applied to predict the fatigue lives of scratched smooth specimens, notched specimens, and scratched structural component specimens, respectively. All predictions fall within a twice‐error band of the experimental data, demonstrating good accuracy of the proposed models.