Investigation of fatigue properties of joints of sheet metal materials used in automotive industry with different joining techniques

In this research, Erdemir 1314 quality galvanized steel sheet and Al 5052 H32 alloy sheet metal sheet, which are used in vehicle components in the automotive industry and are metallurgically incompatible with each other, were combined from one point using three different methods, one of the preferred sheet metal joining methods in the automotive industry, and their fatigue behavior was investigated. Three different joining methods determined for this research are respectively; Clinching, Resistance Spot Welding (RSW) and Self-Pierce Riveting (SPR) are methods. In this research, before the fatigue tests, sheet metal materials consisting of Erdemir 1314 quality galvanized steel and Al 5052 H32 alloy were subjected to tensile test according to TSE EN ISO 6892-1 standard in order to determine their mechanical properties. Before the tensile tests, the presence of elements in the internal structure of the materials consisting of sheet metal samples consisting of aluminum and steel was analyzed with OES (Optical Emission Spectroscopy) in order to determine whether they are in the properties offered to us by the companies. The distributions in the source region and the proportional structure of this distribution were determined by Energy Dispersive Spectrometer (EDX) on the samples combined with RSW. Steel and aluminum alloy sheet metal samples were combined with three different sheet metal joining methods determined in this research, according to the TS EN ISO 14273 shear test standard, and the separation forces were determined. For fatigue tests, steel and aluminum sheet metal samples were combined with three different sheet metal joining methods determined in this study according to TSE EN ISO 14324 standard and fatigue tests were performed. Fatigue life graphs were created as a result of the experimental data obtained. The values corresponding to N=106 cycles were taken as the fatigue cycle limit. In addition, the crosssectional views of the samples, which were joined by sheet metal connection methods, prepared using metallographic devices, were photographed with the help of optical microscopes, and the structure of clinching and SPR joint forms in cross-sectional views were examined. It has been determined that the joints made with the RSW method have higher strength compared to the other connection methods in the evaluation of the shearseparation strengths required to start the fatigue tests. The lowest shear separation force values were observed in the clinching method. It has been determined that the fatigue life of the clinching technique, which has a more flexible joining structure, has superior values compared to other joining methods. Keywords: Resistance Spot Welding, Clinching, Self Pierce Riveting, Sheet Metal Joining Method, Fatigue