# Clinching of High-Strength Steel Sheets with Local Preheating
## 1 Introduction
The authors concluded that the softening in the sub-critical heat-affected zone was found to be greater with a longer welding time. Due to factors such as high thermal conductivity, the presence of a natural surface oxide layer, a zinc layer, and other challenges, connecting lightweight materials through welding techniques poses difficulties. Furthermore, the emission of sparks and smoke during the welding process raises environmental concerns. Hence, other assembly process methods can be utilized in joining high-strength steel sheets, such as adhesive bonding, fastening, riveting, clinching, clinching, clinch-riveting, or self-piercing riveting [20; 21]. Over the past three decades, clinching has emerged as a fast-growing mechanical joining method in the automotive and aerospace sectors. Clinching joining technology has emerged as a promising solution for lightweight constructions that require high production rates, especially when joining hybrid metal-composite parts [22; 23]. Clinching is a fast and localized mechanical fastening technique that involves deforming two or more sheet components through plastic deformation. The process utilizes a punch, a blank holder, and a specialized die assembly. By pressing the forming sheets, which are initially clamped between the blank holder and the die assembly, a friction-based interlocking connection is created between the sheet components [24; 25; 26; 27]. The clinching process of materials with various thicknesses and mechanical property arrangements was investigated by [PERSON] et al. [28]. The sheet thickness arrangement in relation to the die is an important parameter influencing the load-bearing capacity. [PERSON] et al. [29] studied mechanical clinching, using modified dies, and the resistance spot welding that is used to join ultra-high strength steel sheets with low ductility. The static joint loads for resistance spot welding were larger than those of clinching in the tension-shearing and cross-tension tests. In the automotive industry, clinched joints are taken as an alternative to resistance spot welding. The main disadvantage of clinched joints is their lower load-bearing capacity compared to resistance spot welds [29; 30; 31]. This results in efforts to increase the load-bearing capacity of clinched joints. Efforts to increase the load-bearing capacity of clinching joints have led to research on the heat treatment of clinched joints and its combination with adhesive bonding. [PERSON] et al. [32] studied the application and evaluation of clinch-bonded hybrid joining technology in various manufacturing disciplines. The study focused on specimens made of similar and dissimilar sheets of H62 copper alloy, aluminum alloy, and galvanized steel. The shear strength of the specimens, primarily influenced by the adhesive, outperformed their peeling strength, which was closely associated with the clinched structures. [PERSON] et al. [33] investigated the dynamic flow behavior of adhesive during the clinch-bonding process and its impact on joint formation. A lower clamping force should be employed in clinch-bonding to ensure the sufficient handling strength of the joint before the adhesive is cured. [PERSON] [34] dealt with two different manufacturing procedures: adhesive curing before clinching and clinching before adhesive curing. They found that clinching before adhesive curing was a more effective technology for achieving stronger joints. [PERSON] et al. [35] studied the behavior and durability of clinch joints at room temperature, 100 \({}^{\circ}\)C, and 250 \({}^{\circ}\)C. The ultimate tensile-shear strength remained relatively unchanged with a temperature increase, but the stiffness and energy absorption decreased at higher temperatures. [PERSON] et al. [36] investigated the effect of heat treatment on the forming process and the mechanical properties of clinch joints made from a highly formable sheet material.