Effect of relative density on dynamic mechanical behavior and deformation mechanisms of porous titanium under coupled high-temperature and high-strain-rate conditions.

The influence of relative density on the dynamic mechanical behavior of porous titanium under combined high-temperature and high-strain-rate conditions is investigated. Using validated finite element models based on three-dimensional Voronoi tessellations, simulations of Split Hopkinson Pressure Bar (SHPB) tests were conducted across a range of relative densities (0.3-0.6), strain rates (3000-8000 s-1), and temperatures (25-550 °C). Results demonstrate that increasing relative density from 0.3 to 0.6 increases the yield stress by 511.8%, attributed to enhanced cell-wall interactions and a concomitant shift in deformation mechanisms. Strain rate strengthening and thermal softening compete, with high relative density amplifying both effects. The stress-strain curves exhibit three characteristic regimes: linear elasticity, plateau, and densification, where higher relative density shortens the plateau stage and advances densification onset. Low-density specimens (ρ r  < 0.5) undergo layer-by-layer collapse dominated by cell-wall bending, while high-density specimens (ρ r  > 0.5) exhibit matrix-dominated triaxial compression with reduced localized deformation. Quantitative analysis of regionally partitioned displacement confirms that strain rate intensifies the magnitude of localized deformation, whereas temperature primarily induces global softening. These insights provide a predictive framework for designing porous titanium architectures with tailored dynamic performance in extreme environments.