An investigation of the effect of microstructure on determination of acoustoelastic constants in austenitic stainless steel welding

Residual stress measurement of in-service parts of a system is practically impossible by means of destructive methods. Therefore, the use of ultrasonic method as a non-destructive method has an important role. One of the problems in non-destructive measurement of residual stresses by means of ultrasonic waves is determination of acoustoelastic constants. In fact, for conversion of ultrasonic method data to stress state, it is needed to determine these coefficients very precisely. But for reasons like HAZ inclination and small width of this zone, determination of coefficient of this zone does not perform accurately. In this study, the practical simulation is performed for determination of acoustoelastic coefficient of HAZ. For this simulation, the heat affected zone divided to four separate zones and then the microstructure of those four zones has been simulated on standard tensile test specimen by different heat treatment cycles. This coefficient has been used in evaluation of welding residual stresses of austenitic stainless steel by LCR Ultrasonic waves and the results has been compared with the hole-drilling strain-gage method. By comparison of stress values achieved by HAZ simulation method, the conventional method and hole-drilling strain-gage method, it is seen that the HAZ simulation method cause an improvement in welding residual stress measurement accuracy.