A modified normal strain ratio fatigue life model based on the hybrid approach of critical plane and crystallographic slip theory

• Published in: Fatigue & fracture of engineering materials & structures 2018-05, Vol.41 (5), p.1032-1043
• Main Authors: Mu, L.J., Dong, X.Z., Gao, Q., Tan, C.Q.
• Format: Article
• Language: English
• Subjects: anisotropic life prediction; Crack propagation; critical plane method; crystallographic slip theory; Crystallography; Fatigue failure; Fatigue life; Low cycle fatigue; Model accuracy; Nickel base alloys; Normal strain; normal strain ratio; Regression models; Single crystals; Slip; Superalloys
• ISSN: 8756-758X; 1460-2695
• DOI: 10.1111/ffe.12749

Based on the method combining the critical plane with crystallographic slip theory, an anisotropic low cycle fatigue life model is proposed to reflect the effects of orientation dependence and damage factors on fatigue life. According to this method, the crystallographic slip plane is adopted as the critical plane by searching for 30 potential slip systems. In addition, considering the effects of normal strain and strain ratio on fatigue failure, the normal strain ratio is introduced into model and regression model is obtained by fitting method. The proposed model is verified by estimating the low cycle fatigue lives of single crystal nickel–based superalloys PWA1480, CMSX‐2 and DD3 for different loading conditions. The results show that the proposed model is applicable for more complicated loading situations and give a higher prediction accuracy compared to Sun's model.