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Transient Liquid Phase bonding under Temperature Gradient (TG-TLP bonding) is a relatively new process of TLP diffusion bonding family for joining difficult-to-weld aerospace materials. Earlier studies have suggested that in contrast to the conventional TLP bonding process, liquid state diffusion drives joint solidification in TG-TLP bonding process. In the present work, a mass conservative numerical model that considers asymmetry in joint solidification is developed using finite element method to properly study the TG-TLP bonding process. The numerical results, which are experimentally verified, show that unlike what has been previously reported, solid state diffusion plays a major role in controlling the solidification behavior during TG-TLP bonding process. The newly developed model provides a vital tool for further elucidation of the TG-TLP bonding process.

This research has investigated the influence of gait cycle, malalignment and overweight on total knee replacements using a finite element method. Dynamic and finite element models of fixed- and mobile-bearing implants have been created and solved; the fixed- and mobile-bearing implants demonstrated different performance on movement and contact pressure distribution in the tibio-femoral contact surfaces. More contact areas were found in the mobilebearing implant than in the fixed-bearing implant, but the maximum contact pressures were almost the same in both. The thickness of the tibial bearing component influenced the fixed- and mobile-bearing implants differently. A dynamic model of an implanted knee joint has been developed using MSC/ADAMS and MSC/MARC software. Stress shielding was found in the distal femur in the implanted knee joint. The stresses and strains in the distal femur were found to increase with body weight, especially during the stance phase. Serious stress shielding and more bone loss appear in condition of overweight. The increase of bone loss rate and stress in the distal femur with increase of body weight will result in a higher risk of migration of femoral component after total knee replacement. The peg size effect has been studied using this dynamic model; a longer peg with smaller diameter was found to be the best. Varus/valgus malalignment redistributed the tibio-femoral contact force and stress/strain distribution in the distal femur. The difference between contact forces on the medial and lateral condyle decreased in the valgus malalignment condition. Contact pressure increased in the varus/valgus malalignment condition in the dynamic models of both the fixed- and mobile-bearing implant. However, the mobile-bearing implant performed better in conditions of malalignment, especially malrotation. Body weight had less influence on the maximum contact pressure in the mobile-bearing implant.