NUMERICAL SIMULATION AND VALIDATION OF WELDING AS A MOVING BOUNDARY PROBLEM FOR HYBRID ROCKET MOTOR CHAMBER SYSTEMS

A three-dimensional finite element model is used to simulate thermal environments during the gas tungsten arc welding (GTAW) process of an aluminum alloy hybrid motor case. The numerical simulation was performed using a nonlinear transient thermal analysis with a moving boundary to simulate the weld torch movement along the circumference of the motor case. The heat flux due to welding is modeled as a circular disk on the weld surface with a Gaussian distribution. All major physical phenomena associated with welding, such as thermal conduction, convection, and radiation heat losses, are considered in the model development. The welding parameters, which are sensitive to thermal simulation results, are derived from experimental results on a flat plate of the same thickness. A reasonably good match is obtained with experimental data, and the same weld parameters are used to simulate the welding of the aluminium alloy motor case. The present problem involves identifying the weld location in a motor chamber lined with silica phenolic, ensuring that its interface is kept below 100°C. Three-dimensional transient thermal analysis is performed, simulating the circumferential welding process of motor chamber. The objective of the simulation is to obtain the temperature at different axial distances for the weld location so that a safe one can be chosen. The obtained weld distance is then recommended for the welding process to be carried out on the motor chamber.