Mean Time to Achieve a Failure-Free Requirement with Imperfect Repair

This paper obtains expressions for the mean test time to achieve a failure-free requirement with imperfect repair, under two plans. First do complete repair (good as new) at an even number of failures and partial repair (bad as old) otherwise. Next do complete repair at every k-th failure and partial repair otherwise. Plan 1 is a special case of plan 2 (with k = 2).