Measurements of laser driven spallation in tin and zinc using an optical recording velocity interferometer system

Abstract

Measurements of the dynamic strength, in tin and zinc, shocked by a high power pulsed laser to tens of kilobars pressures are reported. The strain rates in these experiments are of the order of 107 s−1, higher by two-to-three orders of magnitude than those reached with conventional shock generators like plane impacts or explosives. The free surface velocity time history, which is related to the spallation process, was measured with an optical recording velocity interferometer system. This diagnostic technique is noninterfering and provides a highly accurate continuous measurement in time. The spall strength estimated from the free surface velocity profile was compared with the theoretical upper limit for the spall strength, calculated from a wide range equation of state for metals.

Dynamic fragmentation of laser shock-melted tin: experiment and modelling

“…Within the acoustic approximation, a simple relationship can be used : σ R = 1/2ρ 0 C 0 u where ρ 0 is the mass density and C 0 is the bulk sound speed (Antoun et al 2002). For laser shocks below 45 GPa, corresponding to shock breakout of about 10 GPa at the free surface, σ R is about 1.5-1.7 GPa, that is about twice the values determined for solid tin under explosive loading (Grady 1988) or plate impacts (Kanel et al 1996), but close to the 1.4 GPa value measured under laser shocks of lower intensity (Moshe et al 1999). This confirms the known increase of the spall strength with increasing strain rate and decreasing load duration (Antoun et al 2002;Moshe et al 1999).…”

“…For laser shocks below 45 GPa, corresponding to shock breakout of about 10 GPa at the free surface, σ R is about 1.5-1.7 GPa, that is about twice the values determined for solid tin under explosive loading (Grady 1988) or plate impacts (Kanel et al 1996), but close to the 1.4 GPa value measured under laser shocks of lower intensity (Moshe et al 1999). This confirms the known increase of the spall strength with increasing strain rate and decreasing load duration (Antoun et al 2002;Moshe et al 1999). For increasing shock pressures, when clear signs of (partial) melting can be inferred from microscopic observations of the recovered samples, faster oscillations appear and the velocity pullback is shown to decrease (see double arrows in Fig.…”

Effects of theα−εphase transition on wave propagation and spallation in laser shock-loaded iron

“…17,18,22,36 This confirms the well-known increase in dynamic tensile strength with increasing strain rate and decreasing load duration. 35,[37][38][39] The computed thickness of the spalled layer is 16 m in the thinnest sample, 90 m in the 250-m-thick target, and 100 m in the other two. The rise time of the spall pulse, which is related to the gradual evolution of damage, is too steep in the computed profiles because rupture is assumed to be instantaneous in the model.…”

Atomic-Scale Study of Plastic-Yield Criterion in Nanocrystalline Cu at High Strain Rates

“…The choice of strain rates is based on those generated during shock loading using picosecond and femtosecond laser pulses. [17,28,29] Based on Eqs. [3] and [4], for the conditions of uniaxial stress loading, the effective von Mises stress (r e ) reduces to the stress in the loading direction (r x ), and the effective strain (e e ) reduces to the strain in the loading direction (e x ).…”

“…[17] Shock loading using short (nanosecond) laser pulses leads to peak strain rates exceeding 10 7 s À1 , [25][26][27] whereas the use of ultrashort (femtosecond) laser pulses results in strain rates exceeding 10 8 s À1 . [28,29] As a result, MD simulations are carried out to understand the macroscopic deformation behavior of nanocrystalline Cu with an average grain size of 6 nm at ultrahigh strain rates ( ‡10 8 s À1 ). Three aspects of deformation behavior are studied: the tension-compression strength asymmetry, the biaxial yield surface, and the three-dimensional (3-D) yield surface.…”