Design for Reliability

Chapter 4

Reliability Models

Louis J. Gullo

Introduction

Models are developed to simulate actual behavior or performance and to reflect or predict reality. A modeling methodology is needed to fully understand what models are and how they are useful. Maier and Rechtin [1, p. 11] state: “Modeling is the creation of abstractions or representations of the system to predict and analyze performance, costs, schedules, and risks, and to provide guidelines for systems research, development, design, manufacture, and management. Modeling is the centerpiece of systems architecting—a mechanism of communication to clients and builders, of design management with engineers and designers, of maintaining system integrity with project management, and of learning for the architect, personally.”

The goal of a reliability model is to set expectations on performance and reliability, and to represent reality accurately as closely as possible for the purpose of predicting or assessing future performance and reliability. A key focus in developing models is to ensure that no mission-aborting (mission-critical) component will fail during a required mission time. This focus could be extrapolated into no mission failures during the expected lifetime (over a number of missions). This goal is accomplished by identifying design weaknesses using experimental design modeling, analysis, and testing, to improve design for reliability such that mission interruptions are minimized or reduced over the anticipated life, ...