Development of experimental equipment for hydrostatic compression of porous materials

In this work we consider the equipment for hydrostatic compression of porous materials and powders, the distinctive feature of which is the use of non-contact seal with the use as a working agent of viscous mineral oil. Such hydrostat design can be used to identify the determinative correlations of heterogeneous materials, in particular for finding the yield stress on the hydrostatic compression. Using the geometric interpretation of the stress state, considered various terms of flow of plastically compressible materials. For the mathematical modeling of the deformation of a porous workpiece Gurson plasticity model has been used. With the software system Abaqus the deformation of plunger and cylinder under the influence of fluid pressure and the change in the size of the gap and the configuration of the split have been defined. Fluid flow through the labyrinth seals have been defined with consideration of the deformation of the plunger assembly, as well as the change in viscosity of the working agent depending on the pressure. The influence of concentric arrangement of the plunger in the barrel on the fluid flow through the seal has been investigated. It has been shown that the deformation of the plunger assembly at high pressure drops has a significant impact on the flow of fluids, especially in the case of concentric arrangement of plunger barrel. The numerical simulation of hydrostatic pressure caused the investigation of the stress-strain state of a porous workpiece in a thick-walled elastic shell, and the heterogeneity of distribution of average normal stresses on the cross section of the workpiece was shown. The results of experimental studies of hydrostatic compression of porous workpieces from previously compacted and sintered copper powder show a slight variation of porosity on the cross section of the workpiece, which correlates well with the data obtained in the course of mathematical modeling.