6. Conclusion
Based on the research it can be stated that: • Resistance spot welding can be used to produce an acceptable quality of welded joints of steel sheet and closed profile. • Ultrasonic method allows for non-destructive quality evaluation of welded joints of steel sheet of low thickness with closed profile. • Studied joints of steel sheet with closed profile presented defects in the form of sticking (no remelting), despite the fact that connected elements did not have coating that protects them from corrosion. • Cost analysis showed that the high costs of acquisition and possession of ultrasonic equipment are balanced by its applicability, which in turn leads to cost savings in the production stage. The study demonstrated the possibility of using an ultrasonic method for the evaluation of the specific type of joints of spot welded steel sheet of low thickness and closed profile. During the research unclear results of ultrasonic testing were obtained occasionally. In that case, the tested connection were destroyed and analysis of the causes of failure was performed. The testing method presented in this article can be used in factories producing contemporary automotive vehicle equipment.
