Determination of residual stress using critically refracted longitudinal waves and immersion mode

Residual stress plays a very important role with respect to the different material properties (fatigue, fracture, corrosion, wear, friction, etc.). Evaluating and taking into account these residual stresses in the modern resistance of materials seem to be necessary for a better prediction of the behaviour of mechanical parts. In this paper, of particular interest is the method of measurements based on ultrasonic waves. The ultrasonic technique is a non-destructive method of determination of the residual stresses. Its principle is based on variation in the wave speed according to the stress state. The technique requires therefore knowledge of the acousto-elastic constants which are given in our case by a tensile testing machine with representative samples. The experimental procedure associated with this ultrasonic method is also presented, i.e. measurement of travel times, calibration of the acousto-elastic effect and determination of residual stress. The experimental results are successfully compared with the hole-drilling method which is a semi-destructive testing procedure.