SMA fitting of viscoelastic constitutive model and its implementation in structural integrity of solid propellant

To investigate the structural integrity of solid propellant under low temperature ignition impulsion conditions, this paper employs the generalized nonlinear Zhu-Wang-Tang (ZWT) constitutive model with four Maxwell elements, where the parameters of the constitutive model are obtained combining the tensile test data and slime mold algorithm (SMA). Based on the secondary development function of UMAT of the ABAQUS finite element analysis software, this constitutive model is then adopted to numerically simulate the propellant uniaxial tensile test under constant strain. The simulation results were compared with experimental data to validate the reliability of the numerical simulation method. Finally, this numerical simulation method is used to study the structural integrity of 5-pointed star HTPB solid propellant under curing cooling and ignition impulsion conditions at −30°C. The results show that the SMA has faster convergence and higher accuracy than commonly used ant colony optimization. The uniaxial tensile simulation results of the propellant under constant strain are consistent with the experimental results, which verifies the dependability of the constitutive model and the numerical simulation method. The HTPB solid propellant under the conditions of curing cooling and ignition impact at different ignition pressures (10, 12, 15, and 20 MPa) is also applicable to the HTPB solid propellant under different ignition pressures. The maximum equivalent stress and equivalent strain values of HTPB solid propellant under curing cooling and different ignition impulsion pressures (10, 12, 15, and 20 MPa) all appeared at the transition arc of the grain. The structural integrity of the grain is not damaged within 20 MPa ignition pressure at a low temperature of −30°C.