| Because double-base propellant has advantages such as low combustion temperature, low burning rate, cleanly fuel gas and high strength, so it has been one of major fuels for all kinds of medium-small caliber rockets, cannon launched rocket extend-range motor and missile gas generator. With the rocket weapon technology unceasing development, the performance of the propellant grain will require more and more high, but the propellants grains also often have happened unexpected problems during test and emission process. So propellant grain structure integrity problem has been paied more and more attention to by many scholars, set up suitable for application and relatively accurate yield criterion, constitutive relation and numerical simulation method has become one of the hot topics in the study for rocket weapon.The common mechanical problem for solid rocket motor in the design, storage and use process are considered as the research background for the double-base propellant materials. The static and dynamic mechanical properties, yield criterion, visco-elastoplastic constitutive model and model parameter acquisition method and subroutine secondary development of double-base class propellant have been carried out to study. The main contents include the following sections:(1) The quasi-static and dynamic mechanical properties of double-base solid propellant are launched a series of research.Because the mechanical properties of double-base propellant and mechanical properties of other polymer materials have certain differences, the poisson’s ratio, surface strain measurement method, mechanical property and temperature and rate correlation of propellant material are launched research, and the yield point judgment method of double-base propellant material is proposed.(2) The yield criterion and mechanical properties under hydraulic pressure of double-base propellant material are carried out to study. First of all, according to the structure of the universal material testing machine, the corresponding confining pressure test device is designed, and then the relationship between mechanical property of propellant material and confining pressure is stuied by uniaxial compression test under the different confining pressure level. The cohesion and internal friction angle of double-base propellant by Mohr-Coulomp theory have been obtained the first, and then a variety of yield criteria are compared to analysis. And the yield criterion which is suitable for propellant material under different conditions is selected.(3) According to the characteristics of visco-elastoplastic constitutive model, the constitutive model parameters are determine by creep recovery test and cyclic creep recovery test under different stress level, and the constitutive model is verified by the corresponding test. The results prove that the established constitutive model has certain accuracy in this paper.(4) The nonlinear visco-elastoplastic constitutive model is established which is based on Schapery’s nonlinear viscoelastic constitutive model and viscoplastic constitutive model. The three-dimensional incremental form of visco-elastoplastic constitutive equation is extended using incremental method. The concept of yield factor is proposed to judge the yield degree of propellant material. And a user subroutine is programmed with FORTRAN, which is integrated into ABAQUS for numerical simulation, namely the corresponding UMAT subroutine is programmed.The mechanical response characteristics, the change rule and the influence factors of mechanical performance of double-base class solid propellant materials are obtained under static and dynamic loading conditions. For double-base propellant material, establishing constitutive theory, using the finite element method and conclusion will effectively guide the solid rocket motor grain design. Especially these will provide theoretical foundation for solid propellant free loading grain structural integrity analysis. |
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