Mechanical Characterization and Fatigue Performance of Laser and Resistance Spot Welds

Abstract

Mechanical characterization, fatigue performance and failure analysis of laser spot welds and resistance spot welds under tensile-shear loading have been investigated. Similar and dissimilar joints of dual phase advanced high-strength steel (DP780) and deep-drawing steel (DC04) of 2.0 mm thickness for application in the automotive industry were performed. The structural stress concept was used to explain fatigue lives of laser and resistance spot welded joints. The results revealed different failure types with different fatigue behaviour for laser and resistance spot welds under applied cyclic loads at “high load” and “low load” levels. Similar joints of the DP780 show the longest fatigue life at high load levels when compared with similar joints of DC04 and dissimilar joints. However, this difference disappeared when the fatigue test results were considered in terms of the structural stress, which also enabled correlation of the results for RSW and LSW spot welds with different sizes.