Experimental determination by PVDF and EMV techniques of shock amplitudes induced by 0.6-3 ns laser pulses in a confined regime with water

Abstract

With the objective to envisage short pulses for laser-shock hardening of materials, this paper reports experiments where laser-shock amplitudes P generated with 0.6-3 ns laser pulses at λ = 1.06 µm in a confined regime with water have been compared with those achieved with the usual 10-30 ns configuration. First, the experimental characterization of shock waves with polyvinylidene fluoride (PVDF) and electromagnetic (EMV) gauges shows that the short durations allow the generation of higher shock amplitudes than longer duration pulses (10 GPa versus 5 GPa) because of an increase of the pressure saturation intensity threshold I th with short pulses (up to 100 GW cm −1 at 0.6 ns). Above I th , a pressure pulse shortening accompanies the saturation. The P = f (I ) curves have been confirmed by surface deformation measurements induced on a Al12Si alloy. Second, the use of 10 µm aluminium coatings on 316L steel targets impacted at 40 GW cm −2 irradiance was shown to provoke a 25% maximum increase of the peak pressures by type mismatch acoustic impedance effects. Lastly, the PVDF technique is shown to be an accurate method to measure laser shock wave profiles in the 0-200 GW cm −2 regime, whereas the EMV technique is limited to intensity values of less than 20 GW cm −2 .

Finite element analysis of laser shock peening of 2050-T8 aluminum alloy

“…Due to the confining effect of the transparent layer, the plasma pressure is amplified (up to several GPa), and the resulting pressure discontinuity propagates into the material as a shock wave [1,2]. This plasma confined regime, allows obtaining maximum impact pressures of up to 5-6 GPa in the 8-10 GW/cm² intensity regime for 10-20 ns pulse duration, as experimentally shown in [3].…”

“…On Fig.5, a 170 m/s velocity level is evidenced at the elastic-plastic transition, which corresponds to a 1.38 GPa yield stress under planar laser-shock loading (or Hugoniot limit) P H (see equation 1). With C el = Elastic wave velocity = 6000 m/s, ρ= 2750 kg/m 3 The determination of P H allows us to determine the strain rate sensitivity as an 4 input data for constitutive Johnson-Cook's equation (3) using the following formula:…”

Analysis of KrF excimer laser beam modification resulting from ablation under closed thick film flowing filtered water

“…Thermodynamically, the increase in pressure will be coupled to an increase in temperature of the plasma, causing the laser induced plasma under the confinement of the surrounding liquid to have a higher temperature, pressure and density than that of a plasma generated in a gaseous or vacuum environment. The plasma induced pressure is dependant upon the wavelength and fluence of the beam involved [22], with the maximum pressure achievable decreasing with increasing pulse length [23].…”

“…Fabbro has been involved in a wide range of research to understand the nature of the plasma induced in a solid-liquid system [21,23,24]. Fabbro and colleagues have produced an analytical model to predict the maximum pressure, p max , measured in GPa, generated by the laser induced plasma in water:…”

A Study of Polycrystalline Silicon Damage Features Based on Nanosecond Pulse Laser Irradiation with Different Wavelength Effects

“…PVDF piezoelectric film, with measuring range from 0 to 20 Gpa, nanosecond as its frequency response, and dynamic calibration being simple and fast, is an ideal sensor of super-high pressure measurement [20] . At t time, PVDF measured voltage signal V (t) and the shock pressure that on the surface of PVDF thin film P (t) within the scope of…”