The Determination of Lagrangian Sound Velocities for 93W Alloy under Shock Loading and Its Application

It is believed that material always has a finite strength before reaching its shock melting point. In other words, shear strength will not equal to zero at the initial shock compression states before shock melting occurs. In the classical shock pressure experimental measurements, however, we often take it for granted that the normal stress along the direction of shock wave propagation equals the mean stress, or the pressure. This will introduce definitely some uncertainty in the fine equation of state construction. In this paper, we measured the shock loading-reloading and unloading particle velocity history of 93W alloy at the sample/window (Al2O3) interface by using a time resolved velocity measurement technique (VISAR). The longitudinal and bulk Lagrangian sound velocities were deduced from the measured particle velocity history. From the relation of sound velocity vs the strain, we obtained the initial shear stress 0 (ranged from 0.11 to 2.02 GPa), critical shear stress c (ranged from 0.63 to 2.40 GPa), shear modulus G, at three initial shock pressure points of 16, 32 and 95 GPa. And a revised shock Hugoniot curve of 93W alloy taking into account of its material strength effects at shock pressures up to 100 GPa is also presented.