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

Chunguang Wang,Weiping Tian,Marco Pizzarelli

doi:10.1155/2021/5521455

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.

Highlights

The load conditions that the grain in solid rocket motor (SRM) experiences during the stages from production to flight are temperature load in the stage of propellant solidify, gravity load in storage stage, inner pressure when a motor is in working process, and the inertia load in the flight stage [1, 2]
On the one hand, people believe that this is related to the decrease of the overall mechanical properties of the propellant at low temperatures
On the other hand, when mechanical properties of the propellant at low temperatures are enhanced, the influence of the grain m number, internal pressure, boost rate, and case stiffness on the structural strength of the propellant grain should be considered in the motor design [9,10,11,12]

Summary

Introduction

The load conditions that the grain in solid rocket motor (SRM) experiences during the stages from production to flight are temperature load in the stage of propellant solidify, gravity load in storage stage, inner pressure when a motor is in working process, and the inertia load in the flight stage [1, 2]. On the other hand, when mechanical properties of the propellant at low temperatures are enhanced, the influence of the grain m number, internal pressure, boost rate, and case stiffness on the structural strength of the propellant grain should be considered in the motor design [9,10,11,12]. The elastic mechanical method was employed in this paper to obtain the analytical solutions for quantitative and qualitative analysis, which was to analyze and discuss the mechanical properties of circular tube grains under internal pressure considering the case stiffness of materials [15,16,17]. The conclusion drawn in this paper can be applied to the analysis and design of SRMs

The Strain of the Grain

Numerical Validation

Ground Test

Discussion

Conclusion