Weld Defect Inspection of Cylindrical Secondary Batteries Based on Active Thermographic Measurement with Thermal Magnification

This paper presents an active thermographic measurement based inspection technique for detecting weld defects in the battery cap region of cylindrical secondary batteries. As the proliferation of electric vehicles continues, safety issues related to secondary batteries have become prominent. In this study, a defect detection algorithm was developed by aligning visual images and active thermographic images of the cylindrical secondary battery cap region. Lock-in amplitude images during the heating, cooling process using a laser were extracted to measure the difference in temperature patterns arising from internal structural variations. Additionally, to minimize the influence of surface conditions and temperature variations other than laser induced, a 10Hz periodic heating was employed, and thermal magnification in the heating frequency was achieved through data processing. This approach allowed the measurement of temperature changes induced by laser heating and cooling while minimizing the impact of surface conditions and temperature variations unrelated to the laser. A dataset of 1000 specimens was constructed by aligning thermographic data with vision images acquired through this method. defective samples. Using this thermographic vision alignment dataset, a defect detection algorithm was trained to achieve a more accurate and faster inspection performance compared to existing non-destructive testing technologies. © 2024, NDT. net GmbH and Co. KG. All rights reserved.