Assessment of Ultrasonic Welds Using Pulsed Infrared Thermography

Ultrasonic metal welding is used in the automotive industry for a wide variety of joining applications, including batteries and automotive wire harnessing. During electric vehicle battery pack assembly, the battery cell tab and busbar are ultrasonically welded. Quality inspection of these welds is important to ensure durable packs. A method for inspection of ultrasonic welds is proposed using pulsed infrared (IR) thermography in conjunction with electrical resistance measurements to assess the structural and electrical weld integrity. The heat source distribution (HSD) was calculated to obtain thermal images with high temporal and spatial resolution. All defective welds were readily identifiable using three postprocess analyses: pixel counting, gradient image, and knurl pattern assessment. A positive relationship between pixel count and mechanical strength was observed. The results demonstrate the potential of pulsed thermography for inline inspection to assess weld integrity.