02.02: FE welding residual stress simulation: Influence of boundary conditions and material models

Abstract

A series of finite element weld simulations was carried out for single-pass welds. Two multi-phase ferritic steel grades with yield strength of 355 MPa were investigated. Methods for selecting efficiently the boundary conditions of unrestrained and clamped-down plates were simulated with satisfying results. Furthermore, the influence of the tangent modulus, the coefficient for thermal expansion and the applied model of hardening behaviour on the final field of calculated welding residual stresses (WRS) was analysed. Values, which provide better agreement with experimental results, along with those that lie on the safe side were highlighted.

Reviewing the Influence of Welding Setup on FE-Simulated Welding Residual Stresses

“…welding simulation, TRIP stands for transformed induced plasticity [2] Regarding the modelling of the microstructural changes that take place, different models have been proposed in the past. A straightforward engineering approach, which was proposed by the authors of the present study [2], provided results with sufficient preciseness and can be applied for the simulation of various materials [8], [9], [10]. Main feature of the approach lies on the assignment of material models to the finite elements inside the fusion zone (FZ) and the heataffected zone (HAZ) during cooling down based on predominant parameters of the thermal cycle, in order to simulate the modified mechanical behavior of the transformed microstructure.…”

“…Finally, during modelling of the mechanical field, the nodal temperature history from the transient thermal analysis is applied as external thermal strains. Solution takes place in a static structural analysis, whereby temperature dependent material parameters and the restraints applied to the real welded component are modelled [10]. Usually, components are clamped down during welding.…”

“…Fixing of the respective nodes in the FE models is a common approach of modelling but deviates from physical restraining reality. An alternative approach applied elsewhere [10] is the use of linear spring elements, restraining the respective nodes (see Fig. 4).…”

“…• Modelling of mechanical boundary conditions (BC): A single-pass weld component of Swedish steel HT36 (equivalent to S355) with dimensions of 2000 mm x 1000 mm x 15 mm was simulated in [10] (component A in the present study). Geometry of the weld section is presented in Fig.…”

Mass Variation With Dissipative Steel Structures Under Seismic Loads

“…Isotropic hardening was chosen in order to get symmetrical response amplitudes, although this does not seem to be a proper choice for structural steels or aluminium [10], [22].…”