Fatigue life prediction of spot-welded joints using a novel indentation technique for precise elastoplastic characterization of weld zones

Abstract

Accurately predicting the fatigue behavior of spot welds remains challenging due to varying material properties across weld zones. This study investigates the fatigue behavior of spot welds in DC04 steel through experimental testing and finite element modeling (FEM). Four modeling approaches—Solid Element (SE), MPC Beam Element (MBE), Quad RBE3, and Triangular RBE3 Elements (T-RE)—were used to simulate the weld nugget, with material properties of the base metal (BM), heat-affected zone (HAZ), and fusion zone (FZ) characterized using a novel indentation method. Fatigue life predictions were conducted using multiaxial criteria, including Morrow, Brown-Miller-Morrow (BMM), and Smith-Watson-Topper (SWT). Microhardness and microstructural analyses identified a decarburized ''pale halo line'' at the FZ/HAZ interface, resulting in a notable reduction in hardness. Experimental fatigue tests validated the numerical models, with simulations using SE providing the most accurate predictions of fatigue life and fracture behavior. Among the fatigue criteria, BMM predictions were the most conservative, while Morrow and SWT showed closer agreement at higher stress levels. This research highlights the effectiveness of advanced modeling and material characterization techniques in improving the accuracy of fatigue life predictions for spot welds in the automotive industry.

Keywords

• Resistance spot welding (RSW)
• Heat-affected zone (HAZ)
• Microindentation
• Fatigue life estimation
• Finite element simulation