Calibrating Gruneisen-Gamma(V) in the Framework of the Adiabatic-Gamma(V) EOS for Detonation Products

Abstract

In a previous article a new equation of state (EOS) for detonation products called adiabatic-gamma(V) was presented [1]. Briefly, adiabatic-gamma(V) is a Gruneisen EOS referred to a principal isentrope, which is specified in terms of the adiabatic gamma γ(V). The γ(V) function is piecewise linear with an arbitrary number of nodes n ≥ 3. The nodes of γ(V) are calibrated from Chapman-Jouguet (CJ) conditions and from expanding cylinder test data. In an expanding cylinder test the products release along the principal isentrope. It is therefore possible to calibrate the Gruneisen parameter Γ from such a test only at the CJ point and at large V, and in between we assume a linear variation. Here we show that in a plate push test with a gap between the explosive and the plate the products release along a higher isentrope (in the PV plane), which makes it possible to calibrate Γ(V). We define Γ(V) as a piecewise linear curve with nodes at the same values of V as γ(V). We demonstrate a procedure for calibrating Γ(V) by matching a target velocity history u(t), to be obtained from a plate push test with a gap. Like the procedure for calibrating γ(V) demonstrated in [1], this, too, is a recursive procedure.