Pore-scale numerical modelling of large deformation behaviour of sintered porous metals under compression using computed microtomography

Abstract

This work concerns the numerical modelling of the deformation process of porous sintered metals, considering the shape of pores on the mesoscopic scale based on microtomography. Sintered 316L steel with various porosity values was used. Limited microtomography device accuracy for porous metals studies results in a lack of fissure mapping and pores with smaller dimensions than the pixel size of the tomographic image. For this reason, two methods were used in this work to compensate for the influence of not mapping the geometric details of porous mesostructures onto the results of numerical calculations. Based on the microtomographic cross-sections obtained, three-dimensional geometric models mapping the shape of the porous structure of the studied materials were created. The models were used for numerical calculations of sintered steel compression behaviour using the finite element method. The modelling also considers self-contact of the porous structure and the effect of closing the pores during compression. As a result, macroscopic stress-strain curves for the studied porous structures and distributions of stress and strain in the deformed material were obtained. Based on the analysis of the numerical calculation results, the deformation process for porous sinters in the range of large plastic strain was described and the influence of porous structure deformation on the mesoscopic scale on the material behaviour in the macroscale was determined. The work also compares the results of tests obtained by three calculation models and points out the advantages and disadvantages of their application to numerical modelling of the deformation process of porous metals.