Finite element simulation of the welding process and structural behavior of welded components

This paper presents an experimentally checked finite element simulation with the general nonlinear program PAM NEP-D, of the electron beam welding of two thick hemispherical shells, and the behavior of the welded sphere under various additional thermomechanical sollicitations. This complex three-dimensional problem is approached in view of further industrial applications; therefore minimizing the amount of input physical data and the cost of numerical simulations. The thermal and mechanical problems are decoupled. The thermal problem is first solved, and its solution is improved until good agreement is reached with experimental results. The mechanical problem is then solved, and a close comparison with experimental results, together with a parametric study of the input data and model characteristics show the capabilities and limitations of this fast numerical solution (about 10 mn CDC 7600). A transient thermal analysis is carried out, starting from an equivalent axisymmetric heat input near the equator. The computed transient temperatures are checked experimentally on the faces. The calculated melted area is checked by metallographic analysis. Using the calculated temperature patterns and the temperature dependent material characteristics, a thermo-elasto-plastic incremental analysis simulated the transient mechanical states, and the build up of the residual welding stresses and strains. The deflections and surface strains are checked experimentally. Close agreement between the experimental and calculated transient thermal distributions across a meridional section of the welded sphere is achieved with realistic assumptions on the equivalent axisymmetric initial heat input distribution. Further development is suggested to find general links between the equivalent bidimensional heat input and the characteristics of the welding apparatus