Characterization method of the layer thickness of surface residual stress based on instrumented indentation testing

Based on dimensional analysis and finite element analysis (FEA), a test method was developed to determine the layer thickness of the surface residual stress using instrumented indentation testing. The relative loading curvatures of the stressed and stress-free P-h curves were obtained from the FEA results. The platform region of the curve of the relative loading curvature versus the indentation depth was used to estimate the residual stress, and the residual stress layer thickness was obtained by considering the turning point of the curve. According to the error analysis results, the proposed method is valid for estimating the residual stress layer thickness by carefully considering the material properties. The proposed method was reduced to the instrumented indentation testing method to determine the uniform residual stress when the indentation depth was far smaller than the layer thickness.