Fatigue Life Prediction Based on Crack Closure and Equivalent Initial Flaw Size

Materials

Qiang Wang¹  Wei Zhang²  Shan Jiang¹ 

[1] Science and Technology on Reliability and Environmental Engineering Laboratory, School of Reliability and Systems Engineering, Beihang University, Beijing100191, China

关键词: life prediction;    crack closure;    equivalent initial flaw size;    small crack theory;   

DOI  :  10.3390/ma8105367

来源: mdpi

【 摘 要 】

Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent initial flaw size (EIFS) concept are employed. Different effects of crack closure on small crack growth region and long crack growth region are considered in the proposed method. The EIFS is determined by the fatigue limit and fatigue threshold stress intensity factor △K_th. Fatigue limit is directly obtained from experimental data, and △K_th is calculated by using a back-extrapolation method. Experimental data for smooth and circular-hole specimens in three different alloys (Al2024-T3, Al7075-T6 and Ti-6Al-4V) under multiple stress ratios are used to validate the method. In the validation section, Semi-circular surface crack and quarter-circular corner crack are assumed to be the initial crack shapes for the smooth and circular-hole specimens, respectively. A good agreement is observed between model predictions and experimental data. The detailed analysis and discussion are performed on the proposed model. Some conclusions and future work are given.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.