Fatigue and fracture mechanics assessment of weld joints

© Fraunhofer IWM

Welding residual stresses in a longitudinal stiffener and their degradation due to cyclic loading

© Fraunhofer IWM

Fracture mechanics-based estimation of the fracture-Wöhler-curve on basis of the crack-initiation-Wöhler-curve

By combining cyclic plasticity models, numerical welding process simulation, fatigue and fracture mechanics models the lifetime of a welded component can be described realistically. In the following example welding residual stresses and their stabilized state were determined by fatigue tests. In corresponding experiments (Fraunhofer LBF) a significant difference between the crack-initiation- and fracture-Wöhler-curves was found which can be very well described by means of fracture mechanics calculations. The calculations were based on crack propagation curves of the investigated material S460NL, an initial crack with a depth of 0.2 mm and a suitable fracture mechanics model implemented in IWM VERB.