Finite element simulation of densification and shape deformation during sintering

Considering sintering as a viscous process, a stress equilibrium problem is stated in the ANSYS software based on the Finite Element Analysis. In order to take into account the dependence of the constitutive properties on density and temperature, the Scherer Cell Model is implemented into the ANSYS code. The initial finite element model is developed in the initial green body geometry. The thermal program is divided into several steps and, for each one, deformation rates and densification are calculated. For each element, the next step density value is calculated from the densification rate. In order to move from one step to the next one the node displacements are calculated. This way, deformations during sintering modify the shape of the finite element model. As these deformations are the result of the sintering viscous problem, they are a consequence of the stress distribution across the sintering body. This stress distribution is a function of density and temperature gradients as they affect the constitutive properties. In the sintering viscous problem, it is possible to import the load stress resulting from other processes. In the present work, we consider the mismatch of the thermal dilations due to temperature distribution by means of the shear thermal stresses. The thermal hydrostatic stress is not supposed to alter the body shape. A significant expected result is that for lower reference viscosity values, densification and deformation reach higher values. Comparing the thermal stress profile evolution with the shape evolution of the Finite Element Model, it cannot be stated that the sintering body shape totally follows the thermal evolution profile. We believe that this is due to the viscous stress gradient resulting from the temperature and density dependence of sintering constitutive properties.