Modeling of the shape evolution of the rodbillet and optimization of the processing parameters in spray forming

A mathematical model is developed to predict the shape evolution of a growing rod-billet during spray forming and a timesaving method for the calculation of the shadowing efficiency is provided. The results show that the spray-density parameters, the withdrawal rate of the substrate, and the initial eccentric distance play important roles in the shape evolution of the billet. The spray angle affects mainly the shape of the upper transition region of the billet. The angular velocity of the substrate has little influence on the buildup of the billet unless it is excessively fast or slow. The growth rate of the billet's vertex will equal to the withdrawal rate of the substrate after a period of time of the spray forming. The time required to reach the steady growth state of the billet can be reduced by using an appropriate initial eccentric distance if other processing parameters keep constant. The numerical result agrees well with the experimental result. A route for the optimization of the spray forming parameters is presented.