Effect of shear-wave polarization on defect detection in stainless steel weld metal

Ultrasonic inspections of austenitic stainless steel weld metal are particularly difficult because of the dendritic structure and anisotropy of the material. The acoustic properties of stainless steel weld metal are discussed. Data on frequency spectra and variations in longitudinal and shear velocities with wave propagation direction are presented. Differences in shear velocities as great as 25% have been observed as the polarization direction is changed. The difference in detectability of artificial reflectors using shear waves of varying polarization is presented, and it is demonstrated in some cases that horizontally polarized shear waves can ‘detect’ a reflector in the weld metal where the traditional vertically polarized shear waves cannot.