Resistance Welding

The investigations of spot weldability and of the joining parameter influence on the strength of spot welded components made from super high strength steel grades (e.g. advanced high strength steels – AHSS) have major economic significance in lightweight steel body shell construction. Also in this project, the results are immediately applied in cooperation with industry as well as in national and international standardization committees.

Spot weldability, spot welding process reliability as well as spot weld quality and strength are also of high relevance to safety in lightweight body shell construction. Application of the economical and process-reliable spot welding technique helps to economise on costs and resources at consistent or enhanced passenger compartment safety (crash optimization).

Aims and research topics

• Process reliability of spot welding
  • Welding ranges of advanced high strength steels (AHSS)
  • Two- and three-dimensional weldability lobes
  • Optimum selection of welding parameter combinations
• Metallurgical weldability of advanced high strength steels (AHSS)
  • Welding ranges of advanced high strength steels (AHSS)
  • Electrode wear during spot welding of AHSS
  • Electrode life determination
  • Fuzzy-classification of electrode wear
• Quality assurance of spot welds
  • Quality analysis by fuzzy-classification
  • Quality analysis using dynamic characteristic welding current-electrode voltage lines
  • Quality analysis using correlation methods
  • Influence of the dynamic electrical and mechanical machine properties on the quality
• Fracture analysis of spot welds
  • Test type-dependent fracture analysis for the torsion, tensile-shear, peel, chisel and cross-tension test
  • Analysis of fracture type and fracture surface
  • Fracture mechanics of spot welds
• Hardening of the spot weld location
  • Hardness distribution in the spot weld and the heat-affected zone
  • Relative hardness distribution and hardness tests
• Fatigue behaviour of spot welds
  • Fatigue strength of spot welds and spot welded structures
  • Fatigue crack growth
  • Modelling of fatigue tests
  • Global failure criteria
  • Calculation of the specimen stiffness
  • Comparison of the fatigue behaviour of different joining techniques

Equipment

• Alternating current and medium-frequency inverter spot welding equipment with pneumatic and electromotive force generation (2 kN – 9.5 kN)

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