Shearing resistance of aluminum at high strain rates and at temperatures approaching melt

Characterisation of high rate plasticity in the uniaxial deformation of high purity copper at elevated temperatures

“…The transition is shown in Figure 2, that shows a sketch of the flow stress as a function of rate for two different temperatures as specimens enter a phonon limited regime. Such an inversion has been observed both in Hugoniot elastic limit measurements (Chen et al, 2017;Gurrutxaga-Lerma et al, 2017;Kanel, 2014;Zaretsky and Kanel, 2013) across a wide range of temperatures, and in shear-pressure experiments (Grunschel et al, 2012) close to melt. These experiments have provided some confidence in phonon drag mechanisms being active at high rates, with some quantitative discrepancies, proposed by Grunschel et al (2012) to be due to interactions between moving dislocations.…”

“…Such an inversion has been observed both in Hugoniot elastic limit measurements (Chen et al, 2017;Gurrutxaga-Lerma et al, 2017;Kanel, 2014;Zaretsky and Kanel, 2013) across a wide range of temperatures, and in shear-pressure experiments (Grunschel et al, 2012) close to melt. These experiments have provided some confidence in phonon drag mechanisms being active at high rates, with some quantitative discrepancies, proposed by Grunschel et al (2012) to be due to interactions between moving dislocations. Many constitutive models which use drag do not address the temperature dependence of the viscosity coefficient (Salvado et al, 2017), largely due to the lack of parametrisation data.…”

“…We find a significant difference in the temperature responses of the thermally activated and phonon drag regimes. Whilst the pinning regime thermally softens, in a purely viscous regime the specimen strength is predicted to increase approximately in proportion to the absolute temperature (Grunschel et al, 2012;Gurrutxaga-Lerma et al, 2017;Kanel, 2014;Kanel et al, 2001;Kuksin and Yanilkin, 2013;Zaretsky and Kanel, 2015). The transition is shown in Figure 2, that shows a sketch of the flow stress as a function of rate for two different temperatures as specimens enter a phonon limited regime.…”

“…Nemat-Nasser and Li (1998) extended measurements to 8000 s −1 for temperatures between 77 and 1100 K on OFHC Copper, remaining below the 10 4 s −1 ambient temperature transition rate. The next available measurements in strain rate space are pressure-shear Grunschel et al, 2012), which require models to simultaneously account for changes in geometry and potential new phenomena. Recently, similar rates have been achieved in extremely small SHPB apparatus, showing substantially lower flow stresses than in pressure-shear at ambient temperatures (Casem et al, 2018).…”

Time limited self-organised criticality in the high rate deformation of face centred cubic metals

“…2) show the mechanical threshold, at a fixed post-transition rate, decreases with increasing temperature, thus excluding phonon drag as a potential origin of increased work hardening in the studied regime 7,30 . At higher rates (>10 6 s −1 ) or temperatures close to melt [30][31][32] , drag will likely become a dominant factor, further disrupting any remaining SOC 23,33 .…”