A method of testing residual stress by ultrasonic shear and longitudinal waves

Acoustoelasticity provides a significant method for testing the residual stress on the mechanical components. This leads to use the ultrasonic methods to detect residual stress. However, the influence on the detection precision resulted from the uneven thickness of tested components and the inaccurate stress coefficient obtained by the tensile experiment because of the tensile deformation. To address the difficulty in testing the residual stress distribution in the depth direction or the bolt axial direction, this study proposes a new method by combining ultrasonic shear and longitudinal waves based on acoustoelasticity theory. Meanwhile, the formulas also been provided. In addition, by the bolts which are made of austenitic stainless steel (A2-70), low-carbon steel (4.8) and carbon steel (8.8), a comparison of ultrasonic testing methods and tensile testing also has been given. In the end, the results show that the absolute error limit is 20MPa and the relative error of the testing method is less than 25%. Therefore, the new methods can be widely applied in the detection of the residual stress in the depth direction.