Quality Assessment of Friction Stir Welded Joints – Using the Fundamental Anti-Symmetric Lamb Wave Mode

Abstract

Having a robust non-destructive evaluation (NDE) technique for friction stir welded (FSWed) joints is of interest to the processing community. Such a technique has to be sensitive to the different types and shapes of internal weld defects and has to be applicable for both similar and dissimilar material FSW joints. Investigated was the ability of ultrasonic guided waves to detect and assess the quality of FSW joints. The fundamental anti-symmetric (A0) mode was selected to detect the flaws in FSW joints. Guided waves were excited (using PZT wafers) and received (using a laser Doppler vibrometer, LDV). Implemented was the frequency-wavenumber filtering technique to separate forward propagating wave from any back propagating reflected wave due to the welded joint. Identified was the reflection of the A0 mode caused by the presence of the interface and/or defects within the joint. The findings indicate little sensitivity to the presence of material interface suggesting this technique to have a promising potential among guided-wave-based techniques in the qualitative and quantitative assessment of FSW joints.