Ameliorated longitudinal critically refracted—Attenuation velocity method for welding residual stress measurement

This work aims at quantitative analysing the effect of different microstructures on the velocity at stress-free and stress coefficient (K) of longitudinal critical refraction (LCR) wave in measuring welding residual stress process, ameliorating the traditional LCR wave method for improving its’ effectiveness and accuracy. The longitudinal critically refracted wave attenuation velocity (LCR-AV) method was proposed in the evaluation of residual stresses in A7N01 welded joints. The same initial status base materials samples are used to produce different levels of grain size and precipitation by heat treatment technology, obtained the velocity at stress-free and attenuation of LCR wave. As expected, the voltage amplitude changes linearly with velocity and stress coefficient, and the precipitation effect can be ignored. The LCR-AV method based on the liner relationship between velocity, attenuation and grain size are efficient to decrease the errors resulting from the different microstructure (base metals, heat-affected zones, and welded zones). Differ with the traditional LCR waves method, the LCR-AV method also measures the voltage amplitude, and the measured results of LCR-AV method compared with those obtained by the hole-drilling reference method shows more sufficient measurement reliability and precision. It shows that LCR-AV method is a valuable quantitative technology to estimate the residual stress of welded joints.