Prediction of Fatigue Crack Initiation under Variable Amplitude Loading: Literature Review

Metallic materials are widely employed in engineering constructions, and one of the most common failure mechanisms in metals is fatigue failure. Even though metal fatigue has been studied for almost 160 years, many problems remain unsolved. Fatigue in metal occurs when the metallic material is subjected to varying loads, resulting in failure due to damage accumulation. The fatigue process consists of a buildup of damage that leads to crack initiation, followed by a period of crack growth until the critical flaw size is reached. The sum of a start phase and a propagation phase represents the total life. To better understand the fatigue phenomenon at its different stages and predict the fatigue life, various types of prediction models have been developed and reported in the literature. This paper reviewed the different models that include microstructure scale parameters that can be used to predict how fatigue cracks start under variable amplitude loading, including the Modified Tanaka-Mura Model, Acoustic Second Harmonic Generation, and the Probability of Crack Initiation on Defects. For perfect life prediction under variable amplitude loading, a stress-based approach, a strain-based approach, and a continuum damage mechanics approach are reviewed. The purpose of this paper is to get overview of the current state of approaches to the life prediction of fatigue crack initiation with variable amplitude. Finally, gaps in knowledge about the prediction of fatigue crack initiation under variable loading at high temperatures are pointed out.

Automated summary

Metallic materials are widely used in engineering constructions, and fatigue failure is a common failure mechanism in metals. Despite being studied for almost 160 years, many problems in metal fatigue remain unsolved. Fatigue occurs in metals when they are subjected to varying loads, leading to failure due to accumulation of damage. The fatigue process involves damage buildup, crack initiation, and crack growth until reaching the critical flaw size. Various prediction models have been developed to understand and predict the fatigue phenomenon, including microstructure scale parameters and different approaches for life prediction. This paper reviews these models and identifies gaps in knowledge about predicting fatigue crack initiation under variable loading at high temperatures.