Numerical and analytical investigation of an ultrasonic assisted ECAP process

One of the great challenges in the processing of materials using Equal Channel Angular Pressing (ECAP) is the high forming forces required to produce large shear deformation in the material. Researchers show that thefriction forces between the die and the sample constitute a great part of the total forming forces. Recently, ultrasonic vibrations are successfully implemented into the ECAP process with the aim of reducing the frictionforces. However, there is still need to optimize the parameters of ultrasonic vibrations in the ECAP process using numerical methods. FE simulation of the ultrasonic assisted ECAP process is very time-consuming and duringsimulation, the constant ram speed has interaction with the vibration speed. A virtual increase in the ram speed for simulation of ultrasonic assisted ECAP process will affect the results. By using Coulomb and Dahl frictionmodels, it is analytically shown how vibration speed and constant ram speed interact with each other during FE simulation. The results clearly suggestagainst using virtually higher speeds in numerical modelling of the vibrated ECAP process. The conclusion is reached through comparing several simulations, as well as an analytical formulation, with experimental datafrom literature. The required friction coefficient values to be used in FE simulation at high contact forces are measured experimentally. An alternative strategy is then offered to speed up FE simulation of the vibratedECAP process without the need for a virtual increase in the ram speed. The proposed strategy can increase the simulation speed of the ultrasonic assistedECAP process up to ten times.

Keywords:

ECAP process , Ultrasonic vibrations , Forming forces , Friction