Modelling of temperature profiles for the plunge stage of friction stir welding process

Khan, Imran (2016) Modelling of temperature profiles for the plunge stage of friction stir welding process. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

The present work focuses on thermal modelling for the plunge stage of Friction Stir Welding (FSW) process. Numerical simulations are performed for the plunge stage by considering tool as a rigid and workpiece as a deformable body. The process is optimized by finding out Pearson product moment correlation coefficient between a set of simulated and experimental values taken at a same point of time to find a good correlation and least squared error between the two set of values. Courant Friedrich-Lewy (CFL) condition is used to calculate the time step required to perform the simulations and is found out for different Courant numbers. It was observed that with minimum mesh size (Δx), the R² (Coefficient of Determination) value approaches more towards unity which shows that with mesh refinement the solution converges and is close with the experiments and shows the mesh independency. On the other hand the present work throws a light on the benefits of Courant numbers and its application with different mesh sizes to arrive at an optimal solution. The importance of time step (Δt) which is specified while performing numerical analysis on transient problems has been shown by the application of CFL condition. A two dimensional parabolic heat transfer equation is solved and temperature displacement analysis is performed in transient state. The thermal diffusivity of the material which is one of the most dominant factor considered while solving any two dimensional problem is taken into account while applying CFL condition. This suggests that for different materials, the range of Courant numbers may be different due to the difference in their conductivities. Hence this property of the material is used in the current analysis.

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