Reducing degradation and age of items in imperfect repair modeling

Maxim Finkelstein, Ji Hwan Cha

Research output: Contribution to journalArticlepeer-review


We develop new models for imperfect repair and the corresponding generalized renewal processes for stochastic description of repairable items that fail when their degradation reaches the specified deterministic or random threshold. The discussion is based on the recently suggested notion of a random virtual age and is applied to monotone processes of degradation with independent increments. Imperfect repair reduces degradation of an item on failure to some intermediate level. However, for the nonhomogeneous processes, the corresponding age reduction, which sets back the ‘clock’ of the process, is also performed. Some relevant stochastic comparisons are obtained. It is shown that the cycles of the corresponding generalized imperfect renewal process are stochastically decreasing/increasing depending on the monotonicity properties of the failure rate that describes the random failure threshold of an item.

Original languageEnglish
Pages (from-to)1058-1081
Number of pages24
Issue number4
StatePublished - Dec 2022

Bibliographical note

Funding Information:
The authors thank the reviewers for helpful comments and advices. The work of the second author was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant Number: 2019R1A6A1A11051177).

Publisher Copyright:
© 2022, The Author(s) under exclusive licence to Sociedad de Estadística e Investigación Operativa.


  • Gamma process
  • Imperfect repair
  • Remaining lifetime
  • Renewal processes
  • Stochastic comparisons
  • Virtual age


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