A Nonlinear Ultrasonic Method for Detection and Characterization of Dewetting Damage in Solid Propellant

Abstract

AbstractThe dewetting damage of solid propellant under loading is a key factor affecting the constitutive properties of solid propellant, and it will weaken structural integrity of solid rocket motor charge. The quantitative characterization of its evolution process has always been a very active research field. In this study, a nonlinear ultrasonic (NLU) method is proposed to investigate and monitor in real‐time the nonlinear dynamic response of solid propellant. The NLU parameter, which can evolve dewetting damage, is expressed by some physical quantities such as the frequency peak, the propagation distance and so on, and is recorded at different strain in the tensile tests of the round rod solid propellant specimens. Then, the initial dewetting point, characteristic dewetting point and characteristic dewetting rate are defined to characterize the dewetting performance. The results show that NLU parameter changes continuously with the evolution of tensile process and increases sharply at the initial dewetting damage point. By analyzing the data, an empirical formula characterizing the variation law of NLU parameter with strain is proposed, which is well fitted to the experimental data under different strain rates. In addition, relevant numerical simulation is carried out, and the simulation results verify the feasibility of the NLU method.