Ablation of Cu and Al targets has been performed with 170 fs laser pulses in the intensity range of 10^12-10^14 W/cm^2. We compare the measured removal depth with 1D hydrodynamic simulations. The electron-ion temperature decoupling is taken into account using the standard "two-temperature model". The influence of the early heat transfer by electronic thermal conduction on hydrodynamic material expansion and mechanical behavior is investigated. A good agreement between experimental and numerical matter ablation rates shows the importance of including solid-to-vapor evolution of the metal in the current modeling of the laser matter interaction.

Hydrodynamic simulations of metal ablation by femtosecond laser irradiation

Recent Developments and Novel Applications of Laser Shock Peening: A Review

Optimization of the laser shock peening (LSP) and LASer Adhesion Test (LASAT) processes requires control of the laser-induced target's loading. Improvements to optical and laser technologies allow plasma characterization to be performed with greater precision than 20 years ago. Consequently, the processes involved during laser-matter interactions can be better understood. For the purposes of this paper, a self-consistent model of plasma pressure versus time is required. The current approach is called the inverse method, since it is adjusted until the simulated free surface velocity (FSV) corresponds to the experimental velocity. Thus, it is not possible to predict the behavior of the target under shock without having done the experiments. For the first time, experimental data collected in different labs with the most up-to-date laser parameters are used to validate a self-consistent model for temporal pressure-profile calculation. In addition, the parameters characterizing the plasma (temperature, thickness and duration) are obtained from the ESTHER numerical code, together with the amount of ablated matter. Finally, analytic fits are presented that can reproduce any pressure-temporal profiles in the following domains of validity: Intensities, I, ranging from 10 to 500 GW cm-2 and pulse durations, T pul, between 5 and 40 ns for the direct-illumination regime at 1053 nm, I ranging from 1 to 6 GW cm-2 and T pul between 10 to 40 ns in the water-confined regime at 1053 nm, and I from 1 to 10 GW cm-2 and T pul between 7 and 20 ns in the water-confined regime at 532 nm. These temporal pressure profiles can then be used to predict the aluminum target's behavior under laser shock using mechanical simulation software.

https://iopscience.iop.org/article/10.1088/1361-6463/abc040/pdf

Laser induced plasma characterization in direct and water confined regimes: new advances in experimental studies and numerical modelling

Laser stripping is a process which typically includes different forms of ablation phenomena. The presented work investigates a mechanical stripping process using high pressure laser-induced shock waves in a water confined regime. Power density is studied as a parameter for selective laser stripping on painted specimens and for adhesion relations with single layer epoxy targets. A flashlamp-pumped Nd:YAG laser with fixed spot size (4 mm) is shot on single layer epoxy and several layers of polymeric paint applied on a AA 2024-T3 (Aluminium) substrate. After laser treatment, samples are investigated with optical microscopy, profilometer and chemical analysis (FTIR & TGA). The results show that selective laser stripping is possible between different layers of external aircraft coatings and without any visual damage on the substrate material. In parallel to the experimental work, a numerical model has been developed to explain the background of the physical mechanisms and to qualitatively evaluate the detailed stress analysis and interfacial failure simulation for a single layer of epoxy on an aluminium substrate. The predicted failure patterns agree with the surfaces of the tested specimens observed by a microscope.

https://hal.archives-ouvertes.fr/hal-03219555/document

Towards selective laser paint stripping using shock waves produced by laser-plasma interaction for aeronautical applications on AA 2024 based substrates

Integration of vortex tubes in a trigenerative compressed air energy storage system

This paper presents the first extensive study of the performances of solid polymers used as confinement materials for laser shock applications such as laser shock peening (LSP) as opposed to the exclusively used water-confined regime up to now The use of this new confinement approach allows the treatment of metal pieces needing fatigue behavior enhancement but located in areas which are sensitive to water Accurate pressure determination in the polymer confinement regime was performed by coupling finite element simulation and experimental measurements of rear free-surface velocity using the velocity interferometer system for any reflector (VISAR) Pressure could reach 76 and 46 GPa for acrylate-based polymer and cross-linked polydimethylsiloxane (PDMS), respectively At 7 and 47 GW/cm 2 , respectively, detrimental laser breakdown limited pressure for acrylate and PDMS These results show that the pressures produced were also as high as in water confinement, attaining values allowing the treatment of all types of metals with LSP and laying the groundwork for future determination of the fatigue behavior exhibited by this type of treated materials

https://hal.archives-ouvertes.fr/hal-02457512/document

Laser shock peening: toward the tse of pliable polid polymers for confinement

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.

https://aip.scitation.org/doi/pdf/10.1063/5.0080326

Marine Scius-Bertrand

Papers

Laser induced plasma characterization in direct and water confined regimes: new advances in experimental studies and numerical modelling

Laser shock peening: toward the tse of pliable polid polymers for confinement

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

Dynamical modeling of bi-layer Aluminium adhesive tape for laser shock applications