A direct particle-based computational framework for electrically enhanced thermo-mechanical sintering of powdered materials

As a method for bonding powdered materials, sintering has distinct advantages, such as the production of a near final-shape of the desired product, without the need for significant post-processing. However, sintering has certain deficiencies, such as incomplete or weak bonding. Research is ongoing to improve the process. One approach to improve sintering processes of powdered materials is via electrically enhanced bonding, whereby electricity is pumped through the material, while it is compressed in a press, in order to induce Joule-heating. This paper develops a computationally based model for the direct simulation of electrically enhanced sintering of powdered materials using particle-based methods. The overall approach is to construct three coupled sub-models which primarily involve: (a) particle-to-particle mechanical contact, (b) particle-to-particle thermal exchange and (c) particle-to-particle electrical current flow. These physical processes are strongly coupled, since the dynamics dictates which particles are in contact and the contacts determine the electrical flow. The flow of electricity controls the Joule-heating and the induced thermal fields, which soften the material, leading to enhanced particle binding. The strong multiphysics-coupled sub-models are solved iteratively within each time-step using a recursive staggering scheme, which employs temporal adaptivity to control the error. If the process does not converge (to within an error tolerance) within a preset number of iterations, the time-step is adapted (reduced) by utilizing an estimate of the spectral radius of the coupled system. The modular approach allows for easy replacement of submodels, if needed. Numerical examples are provided to illustrate the model and numerical solution scheme.