Citation

Rajagopalan S, Sundaresan M. Reliab. Eng. 1985; 12(4): 193-203.

Copyright

(Copyright © 1985, Elsevier Publishing)

DOI

10.1016/0143-8174(85)90042-3

PMID

unavailable

Abstract

The classical design of mechanical hardware is based on the safety factor (sometimes referred to as the 'index of ignorance'); this does not consider the statistical nature of the design variables and leads to overdesign, which is usually reflected in excess weight. The problem is tackled by using the Stress Strength Interference theory, wherein we take into account the statistical distributions of the environmental stress acting on the component and the component's ability to withstand that stress.

In a rocket motor, the structural reliability is given by R = P[(S − s) > 0] where P, S and s stand for the probability, strength and stress, respectively. Equations were developed for expressing S and s in terms of basic design parameters such as shell thickness, weld efficiency, uniaxial ultimate strength, biaxial gain, radius of motor case, weld mismatch, etc., and the reliability at a specified confidence level is obtained using a Monte Carlo simulation technique.