Investigation of Residual Stress in U-shaped Block by Using Ultrasonic and Finite Element Method

Formation of residual stress, as results of machining process, is a familiar fact. One question that needs to be raised is how to know the actual value of residual stress and its distribution in work. In this paper, we explore a detecting-system based on ultrasonic and Wi-Fi to measure residual stress in materials expediently. By using different frequencies and normal transducers, residual stresses in different depths and surface of a U-shaped block, designed with the states of opening and closing, are measured by cross-correlation algorithm about difference of times LCR wave spreading. The Finite Element method analyzing the U-shaped block provides an object contrast to verify the correctness of results detected by the detecting system. We evaluate significantly the actual value of residual stress by comparing a position existing residual stress with another position without residual stress. The second contribution of the paper is to build a system about calibrating the results of residual stress measured by ultrasonic.