The effect of temperature on the elastic precursor decay in shock loaded FCC aluminium and BCC iron

Abstract

This article offers a comprehensive experimental and theoretical study of the causes of thermal hardening in FCC Al and BCC Fe at high strain rates, with the aim to shed light on important mechanisms governing deformation and failures in materials subjected to shocks and impacts at very high strain rates. Experimental evidence regarding the temperature dependence of the dynamic yield point of FCC Al and BCC Fe shock loaded at 107 s−1 is provided. The dynamic yield point of Al increases with temperature in the range 125K–795K; for the same loading and temperate range, the dynamic yield point of BCC Fe remains largely insensitive. A Multiscale Discrete Dislocation Plasticity (MDDP) model of both Fe and Al is developed, leading to good agreement with experiments. The importance of the Peierls barrier in Fe is highlighted, showing it is largely responsible for the temperature insensitivity in BCC metals. The relevance of the mobility of edge components in determining the plastic response of both FCC Al and BCC Fe at different temperatures is discussed, which leads to developing a mechanistic explanation of the underlying mechanisms leading to the experimental behaviour using Dynamic Discrete Dislocation Plasticity (D3P). It is shown that the main contributing factor to temperature evolution of the dynamic yield point is not the mobility of dislocations, but the temperature variation of the shear modulus, the decrease of which is correlated to the experimental behaviour observed for both FCC Al and BCC Fe

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

“…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.…”

“…Despite the widespread use of the uniaxial stress geometry for model parametrisation, exemplified in data collation by Liang and Khan (1999), Jordan et al (2013) and Hansen et al (2013) measurements at elevated temperatures and rates above 10 4 s −1 are sparse. The majority of measurements in that temperature and rate regime exist under conditions of shear strain Grunschel and Clifton, 2007) or the uni-axial strain conditions present in shock wave propagation (Chen et al, 2017;Gurrutxaga-Lerma et al, 2017;Kanel, 2014). Furthermore, in both cases measurements typically begin an order of magnitude above the transition rate.…”

Dislocation spreading and ductile–to-brittle transition in post-irradiated ferritic grains: Investigation of grain size and grain orientation effect by means of 3D dislocation dynamics simulations

“…where v k 5 v edge 5 s*b/B [62,63]. The stress-and temperature-dependent constitutive rules, together with the material-dependent parameters of Table II, enable a gradual transition of the stress-velocity response with increasing straining temperature.…”

Высокоскоростная Деформация И Разрушение Стали 15Х2НМФА Под Действием Ударной Нагрузки При Нормальной И Повышенной Температурах

“…На расстояниях до 0.5−1 mm регистрируется затухание упругого предвестника, затем в диапазоне 1−4 mm амплитуда предвестника сохраняется практически неизменной. Регистрируемая ширина пластической ударной волны увеличивается по мере распространения; отчасти это связано с переотражениями предвестника между свободной поверхностью и пластической ударной волной [4].…”

“…Исследованиями последних лет установлено, что предел текучести ряда металлов со структурой ГЦК и ГПУ в условиях высокоскоростной деформации может возрастать с увеличением температуры [1][2][3][4][5]. Этот эффект аномального термического упрочнения объясняется большим вкладом фононной вязкости в сопротивление движению дислокаций при высоких скоростях деформации [6].…”