Some properties of confidence bounds on reliability estimation for parts under varying stresses

Wenbiao Zhao, Rong Pan, Alexander Aron, Adamantios Mettas

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Reliability estimation is usually performed on a part under a constant stress level. However, a part could experience several different stress levels, or profiled stress, during its lifetime. One such example is when the part is subject to step-stress accelerated life testing. Studying the reliability estimation & its confidence bounds for a part under varying stresses will generalize the existing estimation methods for accelerated life testing. In this paper, we derive the reliability function of a part under varying stresses based on a Weibull failure time distribution, and cumulative damage model. The reliability confidence bounds, based on a s-normal approximation, are given explicitly, and their limiting properties are discussed. A step-stress accelerated life testing example is used to illustrate these interesting properties, which provides the insights of the limitation of the current test plan, and how to design a better one.

Original languageEnglish (US)
Pages (from-to)7-17
Number of pages11
JournalIEEE Transactions on Reliability
Issue number1
StatePublished - Mar 2006
Externally publishedYes


  • Accelerated life test
  • Confidence interval
  • Cumulative damage model
  • Maximum likelihood estimation

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Electrical and Electronic Engineering


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