Session: DTM 08-01: Theory Development in Design Research

Paper Number: 186618

186618 - Defining Reliability 

Despite the fact that it is difficult even to define, reliability is a key concern for many products, systems and endeavors. This
paper attempts to provide an all-inclusive definition of reliability together with a mathematically rigorous measure that would
enable reliability evaluation and optimization. Recognizing that failures result in uncertain outcomes, the proposed theory
relies on the mathematics of decision theory. However, while this mathematic fails to enable a clear definition and measurement of reliability, it does provide a clear definition and measure of unreliability, namely the decrease in expected utility resulting from the plausibility of failures, that enables evaluation and optimization of system design, operation and maintenance.  The approach taken here leads to an analysis that accounts for reliability as of a function of time and events occurring during the operation of a system, potential failure recovery modes, a system risk preference, and the cost of achieving greater reliability.  It also enables the determination of a cost of unreliability, which limits the amount of money that would rationally be spent to increase reliability.  The theory is demonstrated by an unreliability analysis of the Orbit Adjust Propulsion System of the Atmospheric Explorer-C satellite showing that a measure of unreliability enables all of the functions one might require to evaluate and optimize the design and operation of a complex system.

Presenting Author: Srihith Mudakala Rock Ridge High School

Presenting Author Biography: Srihith Mudakala will be a senior at Rock Ridge High School pursuing Aerospace Engineering in his future career. As a researcher at George Mason University, he has worked with Dr. Hazelrigg on research involving decision theory and system design optimization, alongside individual work in robotics and control theory. He has been recognized for multiple design awards in national engineering competitions and is a member of multiple STEM honor societies.