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

With the objective to envisage short pulses for laser-shock hardening of ma terials, this paper reports experiments where laser-shock amplitudes P gene rated with 0.6-3 ns laser pulses at lambda = 1.06 mu m 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 l onger duration pulses (10 GPa versus 5 GPa) because of an increase of the p ressure 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 mu m alumini um coatings on 316L steel targets impacted at 40 GW cm(-2) irradiance was s hown to provoke a 25% maximum increase of the peak pressures by type mismat ch 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).