# Clinching of High-Strength Steel Sheets with Local Preheating
## 1 Introduction  
Steel sheets of various grades and thicknesses are widely employed in the automotive industry to produce lightweight car bodies. Joining various body parts is essential, and commonly used methods for steel parts include resistance spot welding, laser welding, brazing, soldering etc. [1, 2]. The oldest and most widespread method of joining steel sheets in the automotive industry is resistance spot welding. Resistance spot welding (RSW) is a joining technique that eliminates the need for additional material during the process. It involves applying high-intensity current and pressure with welding electrodes. The process utilizes the heat generated by the current to achieve the necessary welding temperature for joining two or more materials. However, in welding processes, thermal after-effects and distortion are obtained [3, 4, 5]. RSW, as the predominant technique for metal joining, is commonly employed for similar metal materials. However, when dissimilar metals are welded together, there is a risk of welding defects due to substantial variations in their physical and chemical properties. This can compromise the overall quality of the joints [6, 7]. The process of RSW depends on the types of used materials and the specific welding parameters. The parameters typical for RSW are the welding current, welding time, and electrode pressing force. It is important to note that welding parameters significantly affectthe quality of the joint [8; 9]. [PERSON] et al. [10] conducted research on the resistance spot welding of high-strength (HSS) steel sheets. They investigated the formation process of the nugget under different welding conditions using experimental measurements and FEM simulation. The FEM simulation accurately predicted the nugget sizes and formation process. The effect of the welding parameters on the quality of spot welds of a combination of various high-strength steels was investigated by [PERSON] et al. [11]. Increasing the welding current values led to higher carrying capacities in a linear dependence. [PERSON] et al. [12] described in their paper that the suitable welding current range of HSS sheets during resistance spot welding shifted to the lower current side compared to that of mild steel sheets, and it was affected by the electrode force. [PERSON] et al. [13] studied the impact of the microstructures and mechanical properties of resistance spot welds in advanced high-strength steels (AHSS) on the overall failure response of structural assemblies in crash events. Strain localization occurred in regions with lower hardness, such as the subcritical heat-affected zone (HAZ), while limited deformation was observed in harder regions, like the upper-critical HAZ and fusion zone. [PERSON] et al. [14] presented a study on the effects of single- and double-pulse resistance spot welding on the microstructures of an advanced high-strength steel (AHSS). The focus was on how the double-pulse welding schemes affected the primary weld nugget, particularly by partially remelting it and annealing the fusion boundary area. The double-pulse welds demonstrated a favorable failure mode. [PERSON] et al. [15] analyzed the failure of resistance spot-welded AHSS. The authors concluded that in the examined welds, there was a significant decrease in the ductility at the weld nugget such that it resulted in interfacial failure. [PERSON] et al. [16] showed in their article that the current welding parameter influenced the mechanical properties of resistance spot-welded dual-phase steel welds. [PERSON] and [PERSON] [17] declared, as part of their research, that the current welding parameter had a significant impact on nugget formation compared to the welding time, using finite element analysis. [PERSON] et al. [18], in their article, concluded that the welding current was the most influential and important factor of the weld properties, using SYSWELD simulation software. [PERSON] et al. [19] investigated the shear tension strength of resistance spot-welded ultra-high-strength steels.