Three-dimensional deformation dynamics of porous titanium under uniaxial compression

In situ, synchrotron-based micro computerized tomography is used to investigate three-dimensional (3D) deformation dynamics of open-cell porous titanium under uniaxial compression. The 3D pore structures are captured, segmented, and transformed into separated pores (spheres) connected by throats (bars) according to the pore network model (PNM). Pore and throat size distributions are quantified via the PNM, while pore shape and orientation distributions, via gyration tensor analysis. After yield, the mean values of equivalent diameter, sphericity and aspect ratios of the pores decrease as deformation progresses, indicating increased pore anisotropy. However, the number and equivalent diameter of the throats decrease even at the elastic stage, and the average diameter decreases approximately linearly with increasing bulk strain. The collapse of individual pores is tracked, and the pores with their longest axes aligned perpendicular to the loading direction are prone to compaction compared to those aligned parallel to the loading direction, because of different stress concentrations. Microstructure-based finite element (FE) analysis reproduces the overall deformation characteristics observed in the experiments. The deformation mechanisms and FE model may be useful for guiding material assessment and design related to porous Ti.