14. Technique of Determination of SRM Operational Life Taking into Account Materials and Elements Strength Margins

Annotation: Service life (resource) of the device (system, structure, material) is one of the major factors, which defines the reliable performance of the device or necessity of its replacement. The purpose of this paper is to develop the engineering methodology to estimate the service life of the device to support the well-founded design decision-making. The methodology of estimation of the service life of material or structure is based on the generalization of great amount of Yuzhnoye SDO experimental data and theoretical research on the impact of various factors (properties of materials, loads, storage and operation conditions) on their service life on the ground of strength analysis. At the same time, service life definition is based on the results of stress and deformation analyses and their comparison with strength properties of the applied material (tensile strength and deformation properties). Strength properties of the material should be reduced to test conditions in terms of temperature, pressure, rate of loading, degrees of material aging etc. Methodology provides the estimation of safety margins in all phases of storage and operation of the device, consideration of the impact of the active factors (mass, temperature, loading, process of material aging), performance of calculations for the chosen specific zones of the device. It is shown that the service life estimation is in general case a probabilistic observation because of the random combination of the influencing factors (strength properties, storage and operation conditions, loads). Analysis of experimental and computation data as applied to solid-propellant rocket engine shows that the most dangerous zones, which define the service life, are the fuel charge channel (deformations at launch), a fuel-body coupling zone (breakaway coupling stress) and a “lock” zone of the release collar (concentration of shear and breakaway stresses and deformations). Developed methodological guidelines of the engineering estimate of the service life can be used as the computational basis for the service life of materials and structures in the phase of system design and updating of the assumed design solutions.