The Influence Factors of Grain Integrity under the Internal Pressure Condition in SRM

Abstract

To investigate the influence factors of propellant grain integrity under the internal pressure, the cylindrical grain was equivalent to a thick-wall cylinder and its three-dimension stress-strain problem was solved. Under the internal and external pressure, the strain and displacement equations of the inside thick-wall cylinder were expressed, and then, the stress and strain expressions of grain were obtained. On this basis, the hoop strain equations on the inside surface of the cylindrical grain and case were developed. The hoop strain on the inner surface of the grain can be predicted by the hoop strain of the case cylinder via the strain equations, and therefore, the hoop strain in the inner surface can be indirectly monitored in real time during the working process of the motor. The hoop strain in the inner surface of grain can be effectively reduced by increasing the case stiffness or decreasing the m number of the grain.

Strain Prediction of Grain in Solid Rocket Motor under the Pressure Curing Molding Technology

“…Accurately predicting the strain in the grain under pressure curing conditions is crucial for the design of the SRM [18]. Figure 14 shows that under pressure curing molding technology, for a specific SRM size, a curing pressure of 2 MPa can significantly reduce the residual strain in the hoop direction due to the temperature decrease during the manufacturing process of the grain, which can reduce the total strain of the grain during storage and working processes, and improve the safety and stability of the SRM.…”

“…Moreover, the elastic modulus of the case also affects the efficiency of pressure curing molding technology. The hoop elastic modulus of the case has a significant impact on pressure curing for orthotropic materials [18]. Therefore, the relationship between optimal curing pressure and hoop elastic modulus of the case was studied, as shown in Figure 16.…”