Finite element modeling of hybrid friction diffusion welding of tube-tubesheet joints

Hybrid Friction Diffusion Bonding (HFDB) is a solid-state welding process that proved its capability of producing sound tube-tubesheet joints, but with limitations on tube thickness (up to 1mm) and tube-tubesheet materials. In the petrochemical industry, there is a great demand for the use of carbon steel shell and tube heat exchangers. To investigate the feasibility of HFDB techniques in joining thicker tube (i.e 2.1 mm) on tubesheet joint, a three-dimensional thermo-mechanical finite element model (FEM) was developed and solved using ABAQUS (commercial finite element analysis (FEA) software). The model was used to predict the temperature distribution and developed stresses during and after welding. The model considered temperature dependent material properties while Johnson-cook model was used to govern material plastic flow behavior. In this paper,19 mm (¾ in) ASTM 179 cold-drawn carbon steel tube into an ASTM A516 Grade 70 tubesheet joints was simulated. Results are validated based on temperature measurements, which was found in good agreement with experimental results. The developed model can be used to optimize processing parameters (i.e. tool rotational speed, dwell time “holding time”, and forging force.. etc) and study their effect on material flow and developed stresses.