Heat Flux Determination of Friction Stir Welding Procedure Using Conjugate Gradient Method

This study implements an inverse method for obtaining heat input during the friction welding process in terms of time, with specified sequences. Using limited experimental data leads to precise evaluation of heat generation during the process. Solution accuracy was improved by integration of analytical formulation, consideration of temperature-dependent thermophysical properties and slip definition in three-dimensional finite element model. Specifically, conjugate gradient method was used as inverse method to calculate the unknown parameters. Heat generation within sliding, sticking state was obtained using friction and slip dependence of time and deducted from exponential approximation of angular velocity of matrix. Favorable situation for friction stir welding is the case that workpiece does not experience the melting temperature. Online CO2 gas cooling flow was used to obligate the desired span of temperature. Numerical calculation of heat flux during friction stir welding of Al5052-O accompanied by cooling stage was considered and inverse method was integrated to evaluate governing parameters. Effect of cooling stage in temperature distribution of workpiece was simulated numerically. Calculated unknown parameters indicate good prediction of heat flux, which satisfy the measured temperature, and characteristic parameters of the process.