Defect characteristics-based low-cycle fatigue life prediction model for additive manufactured Ti-6Al-4 V alloys

Volumetric defect is a significant factor that influences the fatigue life assessment accuracy in additive manufactured (AM) metals. In order to accurately assess the effects of volumetric defects on fatigue property of AM alloys, this study investigates the influence of geometric characteristics such as size, location, and shape of volumetric defects on low-cycle fatigue (LCF) properties. The results indicate that these factors have a significant influence on the fatigue life of material, and the volumetric defect location is found to be the most critical factor. In order to identify the critical volumetric defects on the fatigue fracture, a defect characteristic parameter “P” is proposed to characterize the influence of volumetric defect characteristics on the fatigue performance of material. Subsequently, a low-cycle fatigue life prediction model for AM metals that considers the geometrical characteristics of volumetric defects is established based on the relationship between P-parameter and low-cycle fatigue life. The accuracy of the prediction model is within 1.5x error band, which is significantly improved compared to the Manson-Coffin (M−C) model and Smith-Watson-Topper (SWT) model.