A Uniaxial Nonlinear Thermoviscoelastic Constitutive Model with Damage for M30 Gun Propellant

The nonlinear thermoviscoelastic constitutive behavior of a conventional tank gun propellant, M30, is modeled using a modified superposition integral that incorporates the effects of microstructural fracture damage. This work represents a thermoviscoelastic extension of previous work Gazonas 1992, 1993 that modeled the loading rate behavior of the propellant over nearly five decades in strain rate. In this work, uniaxial compression tests are conducted on the propellant at constant strain rates of .01 and 210 1s and temperatures of -30 and 60 degrees Celsius. A master relaxation modulus is determined from the data in the form of a modified power law MPL in reduced time. The coefficients of the MPL are found through nonlinear inversion of the data using a Marquardt-Levenberg algorithm. Time-temperature superposition is employed and the horizontal shift function for each strain level is given by an Arrhenius expression. The propellant is nonlinearly viscoelastic since the logarithm of the vertical shift function is a quadratic function of the logarithmic strain. Theoretical predictions of time-dependent stress versus time, failure stress versus failure time and failure stress versus strain rate quantitatively agree with the experimental behavior of the propellant determined at various strain rates and temperatures. Constitutive modeling, M30 Gun propellant, Nonlinear thermoviscoelasticity, Continuum damage mechanics, Continuum mechanics, Gun propellants.