Indentation Method for Solid Rocket Motor Grain Material Mechanical Properties Testing

ABSTRACT To address the issue that existing testing methods cannot achieve precise in situ characterization of the mechanical parameters of solid rocket motor grain materials, this work, based on the elastic contact theory, combines the generalized Maxwell model for viscoelastic materials to derive and establish the theoretical indentation model for the relaxation characteristics of propellant. Through a coordinated analysis of indentation relaxation testing and finite element simulations at different constant indentation depths, the applicability of the theoretical indentation model was studied. The results indicate that the relaxation modulus is highly consistent at different indentation depths, but there is a certain deviation between the indentation load–time simulation curve and the testing curve. This deviation increases as the constant indentation depth increases. Based on this, the causes of the theoretical indentation model error were analyzed, a correction method for the theoretical indentation model was proposed, and the modified theoretical indentation model was validated through a comparison of simulation and testing data. The theoretical indentation model provides a new method for the mechanical property testing and evaluation of solid rocket motor grain materials.