Accuracy Improvement of Through-Thickness Residual Stress Measurement by Deep Hole Drilling Technique for Welds

In this study, the effect of diameters of drilled hole and trepanned cylindrical sample on the through-thickness residual stress measurement at welds was experimentally investigated. The measured through-thickness residual stresses were compared with those calculated using the welding thermo-mechanical analysis with the finite element methods. Also, the distribution of residual stress on the welded surface was measured by X-ray diffraction method to verify the accuracy of the calculated results. Based on the comparison among them, the effect of diameters of drilled hole and trepanned cylindrical sample on the accuracy of through-thickness residual stress measurement at welds by deep hole drilling technique was evaluated. The results showed that diameter ratio of trepanned cylindrical sample to drilled hole was an important factor for more accurately measuring the residual stress at welds. The accuracy of residual stress measurement was improved with increasing the diameter ratio. From the other perspective, meanwhile, the diameter of trepanned cylindrical sample was required to be smaller than the range of residual stress to be measured. Thus, two requirements for more accurately measuring the residual stress at welds were clarified. It is then expected that the deep hole drilling technique becomes to be more broadly applicable for the welds.