Risk Methodology for Failed Hardware

Abstract

This paper deals with the development of a risk methodology of failed hardware components. This is important because it is not prudent to use hardware (that did not perform per specification) without failure analysis or corrective action. The subject of this article arose from the need to provide a detailed probabilistic analysis to calculate the change in probability of failures with respect to the base or non-failed hardware. The risk methodology used for the analysis is primarily based on principles of Monte Carlo simulation. The random variables in the analysis are: maximum time of operation (MTO) and operation time of each unit (OTU). The failure of a unit is considered to happen if OTU is less than MTO for the normal operational period (NOP) in which this unit is used. NOP as a whole uses a total of four units. Two cases are considered. In the first specialized scenario, any operation or system failure is considered to fail if any of the units used during the NOP fails. In the second specialized scenario, any operation or system failure is considered to fail only if any two of the units used during the NOP fail together. The reason for using the second scenario is that it is critical for both units to function for the redundant system. The probability of failure of the units and the system as a whole is determined for three kinds of systems: perfect system, imperfect system 1, and imperfect system 2. In a perfect system, the operation time of the failed unit is the same as that of the MTO. In an imperfect system 1, the operation time of the failed unit is assumed as 1% of MTO. In an imperfect system 2, the operation time of the failed unit is assumed as zero. In addition, simulated operation time of failed units is assumed as 10% of the corresponding units before zero value. Monte Carlo simulation analysis is used for this study. The necessary software has been developed as part of this study to perform the reliability calculations. The results of the analysis showed that the predicted change in failure probability (P_F) for the previously failed units is as high as 49% above the baseline (perfect system) for the worst case. The predicted change in system P_F for the previously failed units is as high as 36% for single-unit failure without any redundancy. For redundant systems, with dual unit failure, the predicted change in P_F for the previously units is as high as 16%. These results will help management to make decisions regarding the consequences of using previously failed units without adequate failure analysis or corrective action.

Additional information

Notes on contributors

C.S. Putcha

C.S. Putcha is Professor of Civil Engineering in the Department of Civil and and Environmental Engineering at California State University, Fullerton, USA. He has been there since 1981. Dr. Putcha also served as Chairman of the Civil Engg. dept. at California State University, Fullerton during the period of 1995-2001. His areas of research interest are Reliability, Risk Analysis, Failure Modes and Effects Analysis (FMEA) and Fault-tree Analysis. He has published over 80 papers in national and International journals and conferences. He is the recepient of several awards from various organizations including the Distinguished Engineering Educator award from Orange County Engineering Council in February 2001.

D.F. Kip Mikula

D.F. Kip Mikula has a B.Sc. in Mechanical Engineering from the University of Michigan-Dearborn and a Master in Business Administration degree from National University, USA. He has over 10 years of experience in military aircraft reliability on such programs as the F-15, F-18, and B-2. He has been in System Safety for the past 15 years, primarily as Manager for Mechanical, Propulsion System Safety on the Space Shuttle Program (10 years) and is currently the Lead System Safety Engineer for New Business and Advanced Programs for such programs as the as the Boeing Phantom Works Orbital Space Plane (OSP) Program.

R.A. Dueease

Biography for R.A. Dueease was unavailable at time of publishing.

T. Jensen

Biography for T. Jensen was unavailable at time of publishing.

R.L. Peercy

R.L. Peercy obtained his B.A. in Physics from Berea College in 1956 and completed graduate studies in Physics at the University of Missouri-Rolla from 1956-1958. As a Rockwell Project Manager for several NASA contracts, he has authored or coauthored over 20 publications and over 500 significant writings related to manned space flight safety. Apollo Space missions, the Space shuttle program, the Shuttle-Mir space station, present-day international space station. He led the reliability and crew safety effort for mans first flight to the moon on Apollo 11. He developed most of the space shuttle systems integration system safety tools used by NASA since the mid-1970s. He directed the space shuttle safety project and led Rockwell-Boeings safety efforts for 92 flights of the space shuttle.

L. Dang

Biography for L. Dang was unavailable at time of publishing.