Abstract
The modern concept of lightweight design (LW) requires the application of different materials in one structure (multi-material structures). The structure of different materials has a good perspective for application in the automotive and aerospace industries but only if it is possible to achieve a quality joint between different materials. The most used technology for joining different materials in the automotive industry is Resistance spot welding (RSW). Due to different mechanical, physical, and chemical properties, the joining of different materials by RSW technology does not provide a quality joint, and accordingly, alternative technologies for joining different materials have emerged. Resistance element welding (REW) was developed to enable joint of different materials. This paper presents the welding of AW 5754 H22 Al alloy (1.0 mm-thick) and DP500 steel (1.5 mm-thick) using novel REW. The peak load, absorption energy, microstructure, microhardness and fatigue strength of the REW joint has been investigated. The joint of the same materials has been done also using conventional RSW to compare some results. The results that will be presented in this paper show that that REW can achieve reliable joining of the two materials at relatively low welding currents compared to RSW. Using REW process with a significantly lower welding current, satisfactory mechanical characteristics of the weld joint can be achieved, so peak load is between 2300–2500 N, displacement is between 2.5–3 mm and the absorption energy is between 3.3–5.7 J. REW joints showed fatigue strength with the fatigue limit of 882 N.
Highlights
This paper presents the investigation of microstructure and mechanical properties of Resistance element welding (REW) of DP500 steel and aluminum alloy AW-5754 H22 sheets
Heidrich D et al [28] compared the fatigue strength of joints obtained by Resistance rivet spot welding (RRSW), which is very similar to REW and self-piercing riveting (SPR)
The initial crack was formed below the element in an aluminum alloy, which grew with an increasing number of cycles, and eventually caused the specimens to break
Summary
Heidrich D et al [28] compared the fatigue strength of joints obtained by Resistance rivet spot welding (RRSW), which is very similar to REW and self-piercing riveting (SPR) For this purpose, steel material of CR340 with 0.8 mm-thick and aluminum alloy with Al 6016 with 1.0 mm-thick were selected, as well as a combination of the same materials but with 1.5 mm-thick steel. Sizhe Niu et al [29] presented that the maximum lap shear strength of the RRSW joints of aluminum alloy 6061 and press hardened steel could get up to 481.4 MPa at the parameters: welding current 8 kA and welding time 200 ms This joining technology is suitable for joining thermoplastic materials and metals, primarily steel [30]. Of REW joints are superior to traditional RSW joints and that the failure mode of REW joints changes from IF to PF mode with the increasing of the welding current
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