PSI - Issue 77

2

Andreas Fezer et al. / Procedia Structural Integrity 77 (2026) 229–236 Andreas Fezer / Structural Integrity Procedia 00 (2026) 000–000

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1. Introduction Resistance spot welding (RSW) is a very commonly used joining process in body-in-white. Today's car bodies contain 3,000 to 6,000 spot welds (Nadimi et al. 2023; Lv et al. 2022; Söderberg et al. 2012). In RSW, two or more flat workpieces are placed overlapping between two electrodes. A short, high current pulse partially melts the workpieces and forms a connection between them if the parameters are set correctly. In addition to high efficiency, the welding process is easily automated. Further advantages of RSW are the short welding times and the frequent elimination of rework (Dilthey 2006). In general, aluminum alloys are increasingly being used in sustainable lightweight construction applications in mechanical engineering, aerospace, and the automotive industries to significantly reduce CO₂ emissions (Emadi et al. 2022). Aluminum alloys are increasingly being used instead of steel, partly due to their low density and high strength to-modulus ratio (Ostermann 2014). Lightweight materials, such as aluminum alloys, are increasingly being used in body-in-white (Friedrich 2017; Hirsch 2011; Tisza and Czinege 2018). The 5xxx and 6xxx alloys are mainly used for this purpose (Ostermann 2014; Friedrich 2017; Gould 2012). The additional use of cast alloys further increases the proportion of different material alloys. Due to the diverse and varied use of materials and components, structural integrity is becoming a central component in automotive industry. RSW of steel has been significantly better researched than that of aluminum. Therefore, this study investigated the influence of various parameters on spot diameter during the RSW of aluminum. The material chosen was the structural alloy with increased ductility requirements EN AW-6014 (AL6-HDI), which is widely used in body-in-white. 2. Materials and Methods This chapter describes two experimental setups to characterize aluminum alloy sheets. One setup can be used to determine the total resistance, the other the bulk resistance. The sheet material investigated were the alloy EN AW 6014-T4, which are typically used in body-in-white (see Table 1 for the chemical composition of the alloys). All aluminum sheets used in this work have an EDT surface (Electron Discharge Texturing), a TiZr passivation layer and the dry lubricant “Multidraw Drylube E1”. Finally, the comparability of the measured values is discussed.

Table 1. Alloy composition in wt.% of EN AW-6014 according to DIN EN 573-3 (DIN – Deutsches Institut für Normung e. V. 2024) and VDA 239-300 (Verband der Automobilindustrie e. V. 2017)

*EN AW-6014 *(AlMg0.6Si0.6V) **(AL6-HDI) *Chemical Composition (DIN – Deutsches Institut für Normung e. V. 2024)

Si

Fe

Cu

Mn

Mg

Cr

Zn

Ti

V

0.30-0.60

≤ 0.35

≤ 0.25

0.05-0.20

0.40-0.80

≤ 0.20

≤ 0.10

≤ 0.10

0.05-0.20

**Chemical Composition (Verband der Automobilindustrie e. V. 2017)

≤ 1.50

≤ 0.35

≤ 0.25

≤ 0.30

≤ 0.90

≤ 0.15

≤ 0.25

≤ 0.15

≤ 0.10