Fatigue and Fracture Reliability and Maintainability Process

Abstract

Structures dominated by dynamic tensile loads are vulnerable to failure by fatigue and/or fracture. Failure in one member of a redundant structure produces transient dynamic loads in the remaining intact members, with the possibility of progressive collapse. Design factors are subject to large variability, and reliability methods are relevant for analysis. Reliability, however, can also be improved by a maintenance program of periodic inspection and repair. The fatigue/fracture reliability and maintainability (FRM) process is defined. Analysis of the process focuses on estimating the statistical distribution of the time to system failure. Simulation methods are employed to construct this distribution. Examples of solutions of the FRM process are presented. The illustrations demonstrate: (1) Improvement in reliability with additional redundancy; (2) degradation in reliability by adding series elements; (3) impact of an inspection program on reliability; and (4) the “aging” process in a structure.