Prediction of grain orientation in dissimilar metal weld using ultrasonic response of numerical simulation from deliberated scatterers

摘要

Ultrasonic nondestructive testing plays an important role in structural integrity monitoring of dissimilar metal weld (DMW) structures in pressure vessels and piping of nuclear power plants. Inspection of DMW components is too complicated due to its anisotropic behavior to ultrasonic beam propagation. Many researchers are working rigorously to model the grain orientation and ultrasonic beam skewing in DMW structures but still not completely resolved yet. This paper is intended to estimate the grain orientation with the help of numerical simulation for a given asymmetric DMW component with specified scatterers. The DMW is fabricated from austenite stainless steel and carbon steel base metals with austenite stainless steel filler metal using Gas Tungsten-Arc Welding. To study this research a finite element method (FEM) based numerical simulation has been used to exactly evaluate the grain structure. This model mainly depends on the elasticity matrix which is a function of the grain orientation and attenuation of ultrasonic energy of the weld. Iterative measurement of grain orientation using macrograph of the etched weldment with 5 x 5mm mesh size was carried out then the attenuated elasticity matrix was fed into the FEM COMSOL software model as input parameter. Result obtained from numerical simulation (time of flight and amplitude) are validated with the experimental result and good agreement (above 0.8 correlation coefficient) have been observed at higher iterations. This macro-graphic information based numerical model shows the potential to predict the grain orientation of DMW.