双剪连接件及双耳连接耳片疲劳寿命估算的逐次累计求和算法

This paper aims to investigate the failure mechanics of complex joints and evaluate the crack initiate and growth lifetimes of complex joints. Fatigue tests were respectively carried out on double-lap and double-lug joints, failure modes and mechanisms were investigated through scanning electron microscope (SEM) analysis, and fatigue lifetime for crack initiation and growth was determined from fractographic quantitatively interpreted data by using reverse inference method. From the stress severity factor method, fatigue S-N-L (stress-life-stress severity factor) surface model was developed to characterize fatigue characteristics of complex joints for predicting fatigue crack initiation life. Based on fracture mechanics, the formulations were crafted to predict the length and angle of crack growth, and the cycle-by-cycle accumulation algorithm was presented to assess the lifetime of crack growth of joint. Finally, the proposed model and algorithm were used to respectively simulate the lifetime of fatigue crack initiation and propagation for double-lap and double-lug joints, which demonstrates the good agreement between the prediction results and the fracture interpretation results. The proposed model and algorithm provide theoretical basis for determining fatigue lifetime of complex joints.