Automatic Inspection of Spot Welds by Thermography
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The interest for thermography as a method for spot weld inspection has increased during the last years since it is a full-field method suitable for automatic inspection. Thermography systems can be developed in different ways, with different physical setups, excitation sources, and image analysis algorithms. In this paper we suggest a single-sided setup of a thermography system using a flash lamp as excitation source. The analysis algorithm aims to find the spatial region in the acquired images corresponding to the successfully welded area, i.e., the nugget size. Experiments show that the system is able to detect spot welds, measure the nugget diameter, and based on the information also separate a spot weld from a stick weld. The system is capable to inspect more than four spot welds per minute, and has potential for an automatic non-destructive system for spot weld inspection. The development opportunities are significant, since the algorithm used in the initial analysis is rather simplified. Moreover, further evaluation of alternative excitation sources can potentially improve the performance.
KeywordsSpot welds Inspection Non-destructive testing Thermography
The work originated from the research project SpotLight, funded by Vinnova (the FFI program). SpotLight was carried out in cooperation with Saab Automobile AB, Scania, Gestamp Hardtech, SSAB, SAPA, SWEREA IVF, Swerea KIMAB, Volvo Cars, and Volvo Trucks.
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