An experimental method to measure W-J parameters

The W-J equation of state proposed by Wu qiang and Jing fu-qian is a volume equation with pressure and temperature as the independent variables, which is mutually complementary to the Grneisen equation of state, and is extending and perfecting in theory of the equation of state. It is significant to determine the W-J parameters for the study and application of the equation. The W-J parameters can be educed from the Grneisen parameters and adiabatic bulk modulus, but it is difficult to take into account the uncertainty of these parameters. In this paper we explore a method of direct measurement of the W-J parameters. Temperature and pressure were recorded in situ during the rapid compression process, in which the rate of change in temperature was obtained, with pressure at midpoint pressure during the isentropic compression process, through correcting temperature and increasing substantially pressure combined with mean value theorem, and finally the W-J parameters were obtained according to equation R=(P/T) ( T/ P)S. No additional parameter was introduced in the whole process. In addition, as a comparison, the W-J parameters and their relationship with the pressure of sodium chloride were also calculated by using the equation of state, the empirical formula and known parameters. The results showed that the experimentally measured W-J parameters are increased with increasing pressure, and all the W-J parameters obtained by experiments are in good agreement with those by calculation. This suggests that the experimental method in rapid compression process is feasible and reliable for the direct measurement of the W-J parameters.