Local Monte Carlo Method for Fatigue Analysis of Coarse-Grained Metals with a Nanograined Surface Layer

Abstract

The fatigue resistance of coarse-grained (CG) metals can be greatly improved by introducing a nanograined surface layer. In this study, the Weibull distribution is used to characterize the spatially-random fracture properties of specimens under axial fatigue. For the cylindrical solid specimen, the heterogeneity of element sizes may lead to unfavorable size effects in fatigue damage initiation and evolution process. To alleviate the size effects, a three-dimensional cohesive finite element method combined with a local Monte Carlo simulation is proposed to analyze fatigue damage evolution of solid metallic specimens. The numerical results for the fatigue life and end displacement of CG specimens are consistent with the experimental data. It is shown that for the specimens after surface mechanical attrition treatment, damage initiates from the subsurface and then extends to the exterior surface, yielding an improvement in the fatigue life. Good agreement is found between the numerical results for the fatigue life of the specimens with the nanograined layer and experimental data, demonstrating the efficacy and accuracy of the proposed method.

Keywords

• local Monte Carlo method
• fatigue life
• damage evolution
• cohesive finite element
• Weibull distribution
• surface mechanical attrition treatment
• nanograined surface layer