Abstract
The beneficial effect of a fine grain size on crack initiation and low-cycle fatigue (LCF) life is well known. Previous studies have shown that the cycle to failure in many alloys is increased with decreasing grain or microstructural unit size. Despite this qualitative understanding, a quantitative description of the dependence of LCF life on microstructural unit size does not appear available in the literature. Because of this, how crack initiation or LCF life scales with microstructural unit size remains an open question. The objective of this article is to propose a scaling law for treating fatigue crack initiation and LCF failure in metals or alloys. In particular, the dependence of crack initiation or LCF life on microstructural unit size scale is quantified. Evaluation of the scaling law against experimental LCF data for a number of steels is presented. While most of the experimental data were obtained from the literature, LCF data for a Cu-bearing HSLA steel, whose fatigue crack growth behavior is controlled by [epsilon]-Cu precipitates in the nanometer size range, was also generated for the purpose of verifying the proposed model. Finally the different roles of microstructural unit size on fatigue crack initiation an growth are elucidated and discussed.
Published Version
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