Basic Investigations of Non-Pre-Punched Joining by Forming of Aluminium Alloy and High Strength Steel with Shear-Clinching Technology

Abstract

Facing a decreasing amount of resources on the one hand and an increasing demand for comfort on the other, more and more attention is being paid to sustainability and care for the environment. Particularly in the automotive sector, lightweight design principles continue to prosper rapidly. As a result, adjusted materials for different applications were developed. Due to the formation of intermetallic phases, most multi-material mixes cannot be welded and require adapted joining technologies. Mechanical joining technologies such as self-piercing riveting and mechanical clinching have proven effective methods of joining lightweight materials like aluminium and ductile steels. New high-strength steels are increasingly used in crash-sections, where limited deformation under impact load is required. These hot stamped steels have a very low elongation at break and therefore a low formability. Currently there is no joining by forming technology without pre-punching available using these grades of steels on die-side. The newly developed shear-clinching process is one possible method of joining this kind of material without additional elements. The fundamental idea of shear-clinching is a single-stage process in which pre-punching of the die-side material is performed by indirect shear-cutting and subsequent forming of the upper layer into this hole. This would immensely enlarge the application segment of mechanical clinching even if hot stamped steels are positioned on die-side. Fundamental studies are required to ensure process reliability and it is necessary to break down the joining process into fragments, like pre-punching and clinching with pre-punched sheet, and superpose them to form the combined procedure shear-clinching. This paper presents a detailed investigation of the sub-process clinching with pre-hole.

An Overview of Resistance Element Welding with Focus on Mechanical and Microstructure Joint and Optimization in Automotive Metal Joints

“…In 3) , a short-time(≤20ms) welding process is investigated, while the shear tensile-properties are analysed 18) . The join-ability of magnesium to stainless steel and the join-ability of aluminium to ultra-high-strength steel are reported in 21,22) , respectively.…”

“…The application of light metals such as aluminum has been expanding since the metals are advantageous in terms of weight reduction of a car body. However, the joining of a dissimilar metal pair such as aluminum and steel is problematic due to their vastly different solidus temperature and thermal expansion coefficient when conven-tional fusion-based welding technologies hae been attempted 3,4) . Arc welding, the universally accepted method of permanently joining all metals might generally be considered a mature industry but it is still a growing industries 5) .…”

The State of the Art of Finite Element Analysis in Mechanical Clinching

“…With the development of clinching technology, the concept of clinching connection technology is constantly expanding. Based on this technology, hole-clinching [7][8][9], shear-clinching [10][11][12][13][14][15][16], friction-stir clinching [17][18][19][20][21], clinching-welding technology [22][23][24], and clinch-bond composite technology [25,26] have been developed and applied. The materials have been extended from carbon steel and aluminum alloy to new types of refractory materials such as high-strength steel [27][28][29][30][31][32][33], titanium alloy, and magnesium alloy, which present special advantages in the connection between a metal and a non-metal (carbon fiber and polymer [34][35][36][37][38][39][40][41][42][43][44][45][46]).…”

“…15 A schematic illustration of the die-less clinching process with the application of ERH [112] Fig. 16 Working principle of flat-clinching [113] possible to optimize the interlocking parameters. Consequently, the shear strength and the tensile strength of the composite materials were optimized.…”

Clinching for sheet materials

“…However, it is difficult to join ductile materials such as aluminum alloy to high-strength/low-ductility materials, such as carbon fiber reinforced plastic, hot-pressed steel and advanced high-strength steel, by conventional clinching. A new process called hole-clinching may find use in joining these materials without additional elements such as rivets [ 225 ]. In this single-stage process the die-side material is pre-punched by indirect hole-cutting and then the upper layer is formed into this hole.…”