Early Detection of Volumetric Defects Using e-NDE during Friction Stir Welding

摘要

Friction stir welding (FSW) joint quality has been successfully monitored and evaluated with a new electronic Non-Destructive Evaluation (e-NDE) technique. In the e-NDE approach, the dynamic resultant forces acting on the weld tool are monitored and analyzed for consistency. The feedback forces from the loading on the weld tool are measures of material flow resistance that is induced by the rotational and translational motions of the weld tool. Therefore, measuring these forces during the process provides important information about the stability of the plasticized material flow around the weld tool. In an industry-based round-robin program previously conducted, the probability of detection (POD) capability of the e-NDE approach was found to exceed that of a conventional NDE technique based on radiography (X-ray). The emergence of voids was detected with e-NDE at an earlier stage of formation than was detectable by either standard NDE X-Ray techniques or destructive testing techniques. A systematic study was then undertaken to document the capability of e-NDE in detecting volumetric defects caused by the presence of preexisting gaps (simulating production anomalies) in the joint line. Coupons with both triangular and rectangular gaps were prepared from AA2024-T3 plate stock. The e-NDE technique was successfully used to determine the onset of void formation when present.