Numerical Simulation Of Temperature Field During The Repair Welding Process Of Titanium Alloy

As the aerospace technology develops rapidly, the conditions of key components ofaircrafts such as turbine blades, compressor casing get more and more complex, so therequirements of performance of selected material are also higher. Due to the high specificstrength, temperature resistance and corrosion resistance, titanium alloy is widely used.However, during the production and service process titanium alloy structures will havemany defects by the crafts and environment impacts, such as cracks and pores. Usuallythose defective parts can be restored by the repair welding. Repair welding is generallyprocessing in a vacuum environment by TIG, this will involve complex welding thermalprocess. Traditional researches use experimental methods that require repeatedexperimental verification and so time-consuming. This thesis will adapt the numericalsimulation method to study the weld filling process and the distribution of temperaturefield of titanium alloy, meanwhile, in order to improve the computational efficiency, usingoctree grid technology to accelerate the temperature field calculation speed. The majorworks and achievements are as follows:Firstly, A titanium alloy repair welding temperature mathematical model is developedto describe exactly the heat transfer process. Considering a variety of mechanisms, such asheat conduction and radiation heat transfer that exist in the welding pool, giving thereasonable boundary conditions. Meanwhile for the welding process that those defects arefilled with materials, using the element birth and death to simulate the growth process ofweld.Secondly, establishing the octree mesh model for the numerical simulation oftemperature field. The model involves the structure and local mesh refinement rules, at thesame time the specific processes and rules of adapting the octree mesh technology tobreakdown the zone are also presented.Thirdly, by developing the numerical simulation of titanium alloy weldingtemperature field, temperature field distribution and thermal cycle curves in different timeare obtained. The results show that during the numerical simulation of repair weldingprocess, when the weld has not been filled, the initial temperature of the weld metal remain unchanged, as the heat source reaches the temperature of weld metal rises to thehighest temperature rapidly and then declines slowly. This process is coincided with theactual changes of repair welding temperature.Finally, adapting the octree grid to carry out two-dimensional numerical simulation oftemperature field and compared to the uniform grid temperature field. The results showthat the computing temperature field of octree grid agrees well with the uniform grid. Inthe case of the same calculating area, the number of octree grid and the results file size aresmaller than the uniform grid, while the simulation speed is improved, proving that octreemesh model can effectively improve computational efficiency of welding temperaturefield.