Thermal analysis of the girth weld of an elastomeric diaphragm tank

The finite-element thermal analysis of the welding process of a titanium-alloy tank with an elastomeric diaphragm is described. The analysis takes into account the latent heat due to phase changes, the dependence of the material properties with temperature and the effects of the convection in the weld pool. The model is calibrated and validated by comparing its predictions with experimental results from the welding of AISI 304 specimens. The comparison between the model and the experimental results is made in terms of the temperature fields and the dimensions of the weld molten pool. The time evolution of the temperature in the experiments is monitored using thermocouples and a thermographic camera. The molten pool dimensions are measured via macro etching. The girth weld of the tank is analyzed for various hypotheses for the efficiency of the contact heat conduction between the hemispheres and the diaphragm-retaining ring. The results show the convenience to include a heat sink to the welding setup in order to guarantee the thermal integrity of the elastomeric diaphragm.