Influence of viscoplasticity, hardening, and annealing effects during the welding of a three-pass slot weld (NET-TG4 round robin)

In this paper, numerical simulations of a three-pass bead-in-slot weld in an AISI 316LN austenitic stainless steel plate are performed for different material constitutive behaviors, including viscoplasticity. This work has been undertaken as a part of the Task Group 4 (TG4) measurement and simulation round robin of the NeT European network. Finite Element (FE) Welding simulations are performed assuming a moving 3D heat source, accurately calibrated against thermocouple measurements and metallographic analysis. Different constitutive equations, calibrated from cyclic mechanical tests and creep data at different temperatures, are considered for the mechanical computations of residual stresses. The respective influence of cyclic hardening, annealing effects, and viscoplasticity is discussed, considering simple 1D models (fixed end bar analogy, subjected to thermal cycles identical to those experienced during welding) or the more complex 3D 3-pass slot weld FE model, representative of the NET-TG4 mock-up. Simulations results are also compared with residual stresses measurements provided within the NET-TG4 measurement round robin. The simulations emphasize the strong influence of hardening and annealing modelling, and the rather weak effect of creep on residual stresses for this special test case.