Title: Modelling failure rates according to time and influencing factors

Authors: Florent Brissaud, Brice Lanternier, Dominique Charpentier

Addresses: French National Institute for Industrial Environment and Risk (INERIS), Parc Technologique Alata, BP 2, 60550 Verneuil-en-Halatte, France. ' French National Institute for Industrial Environment and Risk (INERIS), Parc Technologique Alata, BP 2, 60550 Verneuil-en-Halatte, France. ' French National Institute for Industrial Environment and Risk (INERIS), Parc Technologique Alata, BP 2, 60550 Verneuil-en-Halatte, France

Abstract: Reliability of systems often depends on their age (aging or burn-in period), on intrinsic factors (dimensioning, quality of components, material, etc.) and on conditions of use (environment, load rate, stress, etc.). Modelling of failure rates as a function of time and influencing factors is therefore proposed. The latter combines a Weibull distribution and a Cox proportional hazards model. A rather flexible representation of the system life phases is then possible, as well as consideration of a large variety of qualitative or quantitative, precise or approximate, influencing factors. The approach which is presented uses feedback data to define the model parameters by maximum likelihood estimations. An application on safety valves provides an illustration of this approach and an evaluation of the model performances.

Keywords: failure rates; influencing factors; Cox model; proportional hazards model; Weibull distribution; maximum likelihood estimation; reliability; safety; modelling.

DOI: 10.1504/IJRS.2011.039299

International Journal of Reliability and Safety, 2011 Vol.5 No.2, pp.95 - 109

Received: 06 Jul 2009
Accepted: 07 Apr 2010

Published online: 31 Mar 2011 *

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