Abstract
Crack closure model has been used in several applications on the prediction of fatigue crack growth life, with expression of crack opening stress often serving as milestones. A typical difficulty in calculating the crack opening stress is the phenomenon of crack closure caused by the compressive load effect. Compressive load effect, resulting in the change of residual stress status at the unloading stage and the decrease of crack opening stress, is a long‐term challenge for predicting fatigue crack growth life. We propose the expression of crack opening stress to predict fatigue crack growth life based on the analysis of compact tensile specimen with elastoplastic element method. It combines the characteristics of material and load to deal with the phenomenon of crack closure and uses stress ratio and normalized maximum applied load variable to construct the expression of crack opening stress. In the study of tensile‐compression fatigue crack growth experiments, the proposed expression is proved to improve, by comparative analysis, the predictive ability on the whole range of experiment data. The novel expression is accurate and simple. Consequently, it is conducive to calculate the crack opening stress under tension‐compression load.
Highlights
Crack closure model has been used in several applications on the prediction of fatigue crack growth life, with expression of crack opening stress often serving as milestones
We propose the expression of crack opening stress to predict fatigue crack growth life based on the analysis of compact tensile specimen with elastoplastic element method
Due to the large stress gradient near the crack tip, the analytical solution of the crack opening stress cannot be obtained by Advances in Materials Science and Engineering fracture mechanics, and the experiment method needs a large number of samples for statistical analysis [19]
Summary
A Novel Methodology for Calculating Crack Opening Stress under Tension-Compression Cyclic Load. We propose the expression of crack opening stress to predict fatigue crack growth life based on the analysis of compact tensile specimen with elastoplastic element method. It combines the characteristics of material and load to deal with the phenomenon of crack closure and uses stress ratio and normalized maximum applied load variable to construct the expression of crack opening stress. Another reason is that the plastic-induced crack closure is related to the load characteristics and the material characteristics [29] For these reasons, many efforts have been made to establish an effective expression to predict the crack opening stress under tension-compression cyclic load. A novel methodology is proposed to calculate crack opening stress based on the mechanism of plastic-induced crack closure, considering the effect of compressive load. Compared with the result of experiment and literature, it is shown that the crack opening stress model can be applied to predict the fatigue crack life under cyclic loading [30]. erefore, we succeed in predicting fatigue crack life with the proposed crack opening stress model and improving the accuracy of predicting effective stress amplitude
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