Copula based constant-stress PALT using tampered failure rate model with dependent competing risks

摘要

Purpose - Accelerated life tests (ALTs) are used to make timely assessments of the lifetime distribution ofhighly reliable materials and components. Life test under accelerated environmental conditions may be fullyaccelerated or partially accelerated. In fully accelerated life testing, all the test units are run at acceleratedcondition, while in partially accelerated life testing, they are both run at normal and accelerated conditions.The products can fail due to one of the several possible causes of failure which need not be independent.The purpose of this paper is to design constant-stress PALT with dependent competing causes of failureusing the tampered failure rate model.Design/methodology/approach - Gumbel-Hougaard copula is used to model and measure thedependence between the life times of competing causes of failure. The use of the copula simplifies the modelspecification and gives a general class of distributions with the same dependent structure and arbitrarymarginal distributions.Findings - The optimal plan consists in finding optimum allocation of test units in different chambers byminimizing the reciprocal of the determinant of Fisher Information Matrix. The confidence interval for theestimated values of the design parameters has been obtained and sensitivity analysis carried out. Theresults of sensitivity analysis show that the plan is robust to small deviations from the true values ofbaseline parameters.Originality/value - The model formulated can help reliability engineers obtain reliability estimates quicklyof high reliability products that are likely to last for several years.