Dynamic Mechanics Characteristic Study Of Surface Cracks In Solid Propellant Grain

The safety of a solid rocket motor, which serves as the propulsion system and the key component of a tactical missile or a field rocket, was extraordinary important. Known from the View of solid missile fault, solid rocket engine failure led to the catastrophic failure was the main reason, and the failure was mainly due to the structural integrity of the grain damage. As a result, study on analysis of structural integrity of the engine should be energetically developped on solid rocket design stage, the structural integrity of grain was one of the key technologies. In the analysis of the structural integrity of grain, study on deformation and fracture characteristics was always a very active research subject.In this paper, the solid propellant grain finite element model charactered by three-dimensional nonlinear viscoelastic constitutive relationship was established, the dynamic field characteristics of solid propellant surface crack was simulated from numerical methods, the distribution of crack tip stress-strain field and the response characteristics of dynamic field on loading rate were studied. The main contents were as follows:1. By studying applicability of generalized viscoelastic constitutive relation in solid propellant material, uniaxial and multi-axial viscoelastic constitutive relation were analyzed by using currency resolving method in nonlinear finite element analysis, and UMAT was programmed by recursion-iterative arithmetic.2. Finite element model charactered by three-dimensional viscoelastic constitutive relation was established and analyzed ,the validity of three-dimensional viscoelastic constitutive relation was validated by comparing numerical result with test result.3. Crack-tip fields of representative grains structure contained precrack was conputed by numerical mothed in three loaded type.VUMAT was programmed by changing the three-dimensional viscoelastic constitutive numerical equation into dynamic constitutive numerical model, the different length crack applied three type load was computed by finite element method, the reponse of crack in dynamic applied load was calculated and the law of crack-tip fields was analyzed.4.The effect loading rate on open stress fields in crack-tip ahead was analyzed by numerical competed result of the crack-tip fields in representative grains structure, and fracture roughness in dynamic applied load was predicted.Through research of this paper, the response to the mechanical properties, the law of Field changes and the start features of crack of solid propellant surface crack with dynamic load conditions were obtained. laid a solid foundation to the analysis of structural integrity of rocket engine, especially to the structural integrity of grain.