Minimisation of the damage in the extrusion process of titanium alloy blades using the response surface method and finite element analysis

Abstract

Extrusion operation is used in the making process of titanium alloy turbine engine blades. In this study, extrusion process of forging preform for a compressor blade has been investigated using the response surface method and finite element analysis. Effects of the initial temperature of die and work-piece, friction factor and velocity of ram on the surface damage and the force needed for the process have been studied. First, the process was simulated by the finite element method. Then, the required experiments for the RSM were designed using the central composite design (CCD) method and each test was simulated according to the relevant conditions by the FEM software. Values of surface damage factor and process force as response functions were extracted. In the next step, response surface model of the response functions was extracted and effects of the process parameters were evaluated by the analysis of variance; finally, the process was optimised using the desirability function method for minimising the damage factor and process force. Results show that by increasing the coefficient of friction, damage factor is decreased and extrusion force is increased. Increasing the ram velocity cause to increase the damage factor and decrease the ram force. Optimisation results show that the damage factor and extrusion force are reduced and simulation according to the optimal conditions confirms the validity of the proposed model.