Investigation Of The Safety For Solid Rocket Motor Under Mechanical Impact

During its storage, transportation, maintenance and service, the solid rocket motor (SRM) may encounter many incidents such as being dropped onto the ground while being hoisted up, crashing when vehicle turns over during transportation, being struck heavily in takeoff or landing accident while being carried by airplane, impacting with launch platform or buildings when there is abnormality during launch of multiple-stage rocket. Impact of great intensity takes place in such accidents, which will lead to SRM ignition or explosion. The Research work of this dissertation aims at the study of SRM safety under mechanical impact. Based on mechanism analysis of hotspots and by use of dynamic finite element method, efforts are focused on the establishment of a general theory applied for SRM safety analysis under mechanical impact.According to the meso-scale structural characteristics of composite solid propellants (CSP), the damage modes in CSP induced by mechanical impacts, and the conclusions of former research, crack friction is considered to be the key factor for CSP hot-spots. Based on analysis of physical and chemical phenomena related with hot-spots formation of crack friction, the meso-scale hotspot model is put forward, control equations for hot-spot formation and development are derived. In the model, many processes or phenomena such as crack friction and growth, heat conduction, phase transformation of oxidant particulates, heat generation by viscous liquid layer, chemical reactions of gases in cracks, heat and mass exchange between phases of gas and solid, are described. The processes of hot-spots formations of cracks friction in solid propellants under normal pressure and shear stress, are analyzed numerically. It is demonstrated that friction of closed crack can lead to hotspot formation, and crack growth is a necessary condition for hotspot.According to the visco-elastical behavior of CSP and relative experiment phenomena, the meso-scale process of viscous heating in matrix of CSP under mechanical impact is studied. On the fundamental of thermo-viscoelasticity, the rate of viscous heat generation in CSP matrix in relation with stress and strain status, is obtained. The meso-scale model is put forward, in which processes or phenomena such as viscous heat in CSP matrix, heat conduction between CSP matrix and oxidant particulates, decomposition of oxidant and its interfacial reactions with CSP matrix, are described. The control equations are derived. By means of dynamic finite element method, impact deformation of CSP samples, the processes of matrix heat, decomposition and interfacial reactions of oxidant particulates, are studied. It is concluded that increase of temperature in CSP matrix is of great extent, and is in dependence with impact velocity, rate of deformation and thermorheologic...