Plane residual stress measurement using ultrasonic considering weak anisotropy of metallic material

Ultrasonic velocity variation (UVV) along different directions induced by material weak anisotropy will lead to residual stress measurement error using ultrasonic inevitably. In this research, the influence of weak anisotropy on residual stress measurement is analyzed theoretically and experimentally. Firstly, the in-plane acoustoelastic wave equation is modified by considering material anisotropy, which can be characterized by two in-plane anisotropic parameters. Further, an analysis model is also established to express the linear superposition of weak anisotropy and acoustoelastic effect on UVV. Based on this, a plane residual stress measurement method has been developed, which was verified using the rolling aluminum alloy plate after friction stir welding. From the comparison with hole-drilling method, it was adequate and capable to measure the plane residual stress by the relative UVV along three particular directions.