Ultrasonic Imaging Inspection of Projection Welds

A high frequency ultrasound imaging technique was applied for quality control of several kinds of projection welds originating from automotive production. The projection welds were formed between V-shaped surfaces of solid components and zinc-coated steel sheets. Acoustic images were obtained both in high resolution and in express regime. Detailed three-dimensional data cubes were acquired using a Tessonics AM 1103 pulse-echo scanning acoustic microscope with a 50 Mhz spherically focused lens. The rapid 2D array technique's potential was demonstrated with a Tessonics RSWA (Resistance Spot Weld Analyzer). The data obtained were processed to determine the joint's basic parameters and to estimate its overall quality. The signal processing procedures were optimized for spatial resolution in conditions of multiple re-reflections. Images of C-scans represent the welds nugget's geometry. The nugget's dimensions and crossection area were measured. Several defects (lack of fusion) were detected and classified. The results presented will be used for development of specialized instrumentation for in-line inspection of automotive body parts in an industrial environment.