On correlation between the hardness-to-strength ratio and the plastic Poisson's ratio of nanoporous gold

We report that hardness-to-strength ratio is not correlated with plastic Poisson's ratio in nanoporous gold, arguing against the Shaw–Sata relation. Instead, the hardness-to-strength ratio of nanoporous gold increases consistently with increasing rate of strain hardening. Furthermore, in samples with near-zero hardening in compression, the hardness-to-strength ratio does not deviate much from 1.0 when the plastic Poisson's ratio increases up to 0.27, echoing Miller's simulation. Current study suggests that the hardness-to-strength ratio is not a restraint factor, but an indicator of the strain hardening rate for nanoporous gold, which might apply to other porous materials with low-to-medium relative densities.