Tools › Reliability › Growth and Testing

Growth and Testing

2 tools in the Reliability area.

Reliability Growth

Reliability growth tracking of a development test from the cumulative failure times, from interval counts or from several systems on their own clocks: the Duane plot (least squares of the cumulative MTBF on the cumulative test time on log-log axes, growth rate, instantaneous MTBF) and the Crow-AMSAA power-law NHPP fitted by maximum likelihood for time- and failure-terminated tests with the unbiased shape, the cumulative and instantaneous failure intensity and MTBF at the end of test, the Cramér-von Mises goodness-of-fit statistic against the MIL-HDBK-189 critical-value table (χ² for grouped data), the handbook's χ² test for growth, Fisher-matrix and Crow (χ² and MTBF coefficient) confidence bounds, and projections of the test time needed to reach a target MTBF and of the MTBF and failures at a future test time, with three figures. The default case is the MIL-HDBK-189 Appendix C two-prototype example (27 failures in 300 hours), whose printed shape, intensity, MTBF, bounds and goodness-of-fit values the page reproduces.

5 worked examples reproduced, listed on the tool page.

HALT and HASS Planning

Two planning tools for environmental stress screening of electronic hardware. The HALT part takes the operating and destruct limits found in a highly accelerated life test (cold, hot, random vibration) and the product specification, tabulates the margins, places the HASS precipitation and detection screens between the limits at the planner's fractions, draws the step-stress and combined profiles and gives the binomial sample-size relations of a small-sample test. The ESS/HASS part computes the screening strength of MIL-HDBK-344A Procedure C, SS = PE x DE, with the handbook's precipitation-efficiency equations for temperature cycling, constant temperature, random, swept-sine and fixed-sine vibration (Tables 5.14 to 5.17) and its three detection-efficiency factors, then runs the Procedure A defect flow (incoming latent defects split into vibration- and thermally-sensitive populations, remaining and removed defects, yield, probability of shipping a defective unit), the allowable remaining defects from an MTBF requirement, the defect density from a part list and Table 5.1, a cost trade-off, the Procedure A4 safety-of-screen damage index with the MIL-HDBK-2164A equivalent-time rule, and a seeded-defect proof-of-screen plan. The default is the handbook's own screening-strength example (4 thermal cycles at 5 C/min over 100 C, 5 minutes at 5 Grms, detection efficiency 0.855), which the page reproduces.

1 worked example reproduced, listed on the tool page.

Other Reliability sections

Life Data · System Models · Physics of Failure · Maintainability and Availability · Safety Analysis