Modeling of multi-edge effects in the case of laser shock loadings applied on thin foils: Application for material characterization of aluminum alloys

Abstract

This article presents the study of the shock wave propagation through aluminum alloys (pure aluminum and aluminum 2024-T3) produced by laser plasma using experimental and numerical tests. Water confinement regime interaction, pulse duration (7.2 ns), and power density (1–5 [Formula: see text]) range correspond to laser shock peening process configuration and parameters. To that scope, we simulate the shock wave propagation using non-linear explicit code LS-DYNA, which we validate with experimental results. Thereupon, we present a descriptive analysis that links separately the material model and loading conditions to the dynamic response of aluminum alloys under high strain rate laser shock by coupling the Johnson-Cook (J-C) material model with the Grüneisen equation of state (MAT_015 and EOS_GRUNEISEN accordingly). In addition, we make use of stress propagation into target thickness to analyze the origin of different points on the Back Face Velocity (BFV) profile during shock propagation. Finally, we provide evidence that 2D compressive effects do not depend only on the focal spot size or target thickness such as the edge effects but also on power density and material initial yield strength.

Transition of elastomers from a rubber to glassy state under laser shock conditions

“…From the simulation of the backface velocity profile, the maximum plasma pressure of each shot is extracted, as is the maximum strain rate. Here the methodology consists of an inverse method; the material parameters from the Johnson-Cook and Mie-Grüneisen models are blocked and taken from a validated model 27 using tabulated parameters for the aluminium behaviour. The pressure profile used is normalized, and only the mechanical load in Abaqus is modified to reproduce the back face velocity profile.…”

“…In this FEM, the Johnson-Cook model was coupled with the Mie-Gru ¨neisen equation of state while also using standard elasto-plastic material parameters for aluminium. 27 The parameters used are given in Table 1.…”

Exact expressions of the uniaxial perfectly elasto-plastic stress wave and induced mechanical fields in the case of a finite impact: application to laser shock peening

“…e 1 being a unit vector in the direction of the propagation. Experimentally, such a situation may be reached when the diameter of the laser spot is much greater than the specimen thickness [13,24].…”

“…In this paper, we consider a LSP-type situation, where L is very large (a few cm, as opposed to the thickness of specimens used for backface velocity VISAR measurements which are thin [24,25]). We also make the (standard) hypothesis of incompressible plasticity, so that we have…”

“…In this case, an axisymetric model is used with an standard/explicit procedure, and with the pressure applied over a very large spot (radius 1 cm) so as to mimic a uniaxial case. In 3D, stress wave edge effects originate from the edges of the laser spot and propagate inward, eventually introducing a perturbation at the center of the impact [24,29]. However the larger the spot size, the longer this perturbation takes to arrive at the center, which is where the analytical expressions are valid.…”