Somayeh Mireh, Ahmad Khodadadi and Firoozeh Haghighi
The purpose of this paper is the reliability analysis for systems with dependent gamma degradation process and Weibull failure time.
Abstract
Purpose
The purpose of this paper is the reliability analysis for systems with dependent gamma degradation process and Weibull failure time.
Design/methodology/approach
Consider a life testing experiment in which a sample of n devices starts to operate at t=0 and the data are available on failure time and failure-evolving process on each individual, called in some contents wear or degradation. Ignoring the between performance characteristics dependency structure may lead us to different reliability estimations, while the dependency justly exists. In previous research, dependency between the degradation process and hard failure time has been studied in limited detail (special closed form expression). Thereafter, the dependency between two degradation processes with the same structure (gamma process) in a system is considered using the copula function.
Findings
The results indicate that ignoring the dependency structure may lead us to different reliability estimations while the dependency justly exists.
Originality/value
This study gives some contributions that evaluate reliability metrics with more than one failure mechanism that may not be independent and possibly follow a different distribution function. The authors have used the copula function as a basis to develop a proposal model and analysis methods. In addition, the authors discussed the identifiability of the copula. Finally, simulation data were used to review the suggested approach.
Details
Keywords
– The purpose of this paper is to design a simple step-stress model under type-I censoring when the failure time has an extension of the exponential distribution.
Abstract
Purpose
The purpose of this paper is to design a simple step-stress model under type-I censoring when the failure time has an extension of the exponential distribution.
Design/methodology/approach
The scale parameter of the distribution is assumed to be a log-linear function of the stress and a cumulative exposure model is hold. The maximum likelihood estimates of the parameters, as well as the corresponding Fisher information matrix are derived. Two real examples are given to show the application of an extension of the exponential distribution in reliability studies and a numerical example is presented to illustrate the method discussed here.
Findings
A simple step-stress test under cumulative exposure model and type-I censoring for an extension of the exponential distribution is presented.
Originality/value
The work is original.