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

A three-dimensional thermo-mechanical finite element model (FEM) was developed and solved to study the feasibility of hybrid friction diffusion bonding (HFDB) technique for welding tube-tubesheet joints using Abaqus/explicit enviroment. Considering the process thermo-mechanical nature, temperature-dependent material properties and Johnson-Cook model were adopted. Two tube configurations were considered in the numerical study; zero projection (flush) and 3 mm projection (extended). For validation purposes, HFDB of tube-tubesheet was experimentally performed on a 19mm (3/4 in.) ASTM 179 cold-drawn carbon steel tube into ASTM A516-70 tubesheet, considering a flush tube configuration. The tool-workpiece temperature was measured using infrared camera, and produced joints were sectioned and examined under optical microscope. A good agreement was found between numericaly estimated temperatures and material deformation with experimentaly measured ones. According to the estimated results, spring back of tube was found to negatively affect the joint integrity. Also, contact stresses during processing phase were found less in the projected tube (extended) as compared to the flush one.