Mean Time to Achieve a Failure-Free Requirement under Provisions of Spare and Repair
This paper obtains an expression for the mean test-time to achieve a failure-free requirement under the provisions of spare and repair.
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).
Failure-Free Period Life Tests
A failure-free period life test (FFPLT) is defined by a pair of real numbers (t, T), 0 < t ≤ T, such that the test is passed if, and only if, a failure-free period of t consecutive time units is achieved in the T time units allowed. Failed items are replaced, and replacement time is not counted. Such tests have been introduced in Mil. Std. 781D (US. Department of Defense 1980). This test is studied in terms of a renewal process under the assumption of exponential interarrival times with constant failure rate λ. Test plans are developed for commonly used producer's and consumer's risks and discrimination ratios. The tests are compared to the well-known time-truncated and sequential-replacement life tests. Also presented are methods for point and interval estimation of λ based on test results. Unbiasedness and consistency are proved and other asymptotic properties are given.