Combination of the optical analyzer technique and multiply photon doppler velocimetry to measure the sound velocities in shock-compressed metals

Abstract

It is proposed to combine the optical analyzer technique (OAT) and multiply photon Doppler velocimetry (MPDV) in every explosive experiment in order to overcome the reported discrepancies in the sound velocities measured in shock-compressed metals using different techniques. Such a combination is demonstrated to be efficient in explosive experiments with stepped samples of 12Kh18N10Т austenitic stainless steel and high-purity Mg95 magnesium under their shock-wave loading in ranges of 60–120 and 20–30 GPa, respectively. The OAT ensures classical recording of the longitudinal and bulk sound velocities. Depending on the loading intensity, the MPDV technique recorded temporal changes in the velocity of the “sample–indicator” interface or temporal changes in the shock-front velocity in the indicator. These data were used to monitor the parameters of the shock-compressed sample and to determine the instant when the first characteristic of the rarefaction-wave fan overtakes the shock-wave front in the indicator. Within the range of relatively low loads where the indicating fluid remains transparent and acts as a window material, the MPDV registers temporal variations in the velocity of the “sample–indicator material” interface. The OAT ensures reliable registration in the range of high-intensity loads, while the MPDV ensures time-resolved registration of the steady-shock-wave front velocity in the indicator up to the instant of its overtaking by a rarefaction wave. Both techniques are observed to work well in the intermediate range of loads. Combining these techniques enhanced the reliability of the obtained consistent data on the sound velocities in shock-compressed structural materials and also allowed a decreased number of explosive experiments with samples of toxic materials.