Visualizing isostatic pressing of ceramic powders using finite element analysis

Cold isostatic pressing, where a rubber bag is filled with ceramic powder, sealed and subjected to hydrostatic pressure, is a method of forming ceramic components with near-net shape. Cracking of the ceramic compact after pressing is one problem associated with the pressing of complex shapes. One mechanism responsible for the cracking of components is the interaction of the rubber bag with the component during the final stages of decompression where the elastomer can deform significantly and impose non-uniform loadings on the compact. Visualization of the detachment process and the stresses induced in the ceramic compact offer the opportunity for the design of press tooling which minimizes the potential for cracking of the components. In this paper, both 2D and 3D finite element models are developed to investigate this problem. The effect of different contact conditions between the compact and the rubber bag is discussed, and the distribution of stresses resulting from the interaction of the compact and the rubber tooling presented. These indicate methods for alleviating the stresses within the compact through suitable tool design.