Quality monitoring framework for friction element welding

The automotive industry faces challenges in reducing vehicle mass to enhance fuel efficiency and reduce gas emissions. A common strategy is to replace conventional steel body parts with thinner ultra-high-strength steels and lower-density aluminum alloys. Friction Element Welding (FEW) is a relatively recent technique developed to join these dissimilar metals in car body manufacturing. This study presents a dedicated monitoring approach for the FEW process, designed to detect typical defects occurring in production lines. To simulate the most critical defect in automotive FEW applications, controlled initial gaps were introduced during the welding of 2000 MPa boron steel and 6xxx series aluminum alloy sheets. This approach enables the assessment of the influence of initial sheet gaps on joint quality. The results provide the basis for developing practical tools for process monitoring and quality assurance, such as control charts, validated through an experimental campaign. The findings demonstrate that the proposed method offers the potential to reduce defects and improve manufacturing efficiency.