In-process control of Friction Welding Processes using Nonlinear Ultrasonic Test Techniques

摘要

Kissing bond defects can occur in solid state joined metals, like friction stir welded aluminium and its non-destructive detection is crucial for many critical structural applications that involves the use of Friction Welding processes. Due to the dimension of kissing bond defects, conventional linear ultrasonic techniques have difficulties detecting the defects as the dimension is many orders of magnitude smaller than the linear ultrasonic wavelength. In January 2013 a UK funded project on the development of a system that integrates a non-destructive testing (NDT) technique with weld quality tracking system to provide an in-process control capability of friction weld defects started. The NDT technique to be developed will be based on the non-linear ultrasound (NLU) technology and will provide feedback of rectification of weld defects to the friction stir welding machine during welding. The project will focus on investigating defects in linear friction welding (LFW) and friction stir welding (FSW). In this paper the NLU effect from defects in FSW has been examined. Initial experimental trials have been conducted to examine the suitability of the technique for weld inspections. Results with nonlinear properties related to mechanical sectioning of welds are presented.