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Comprehensive Considerationin Planning an EffectiveReliability Demonstration Test (更有效的设计可靠性验证试验)Dr. Wendai Wang (汪文岱博士)
©...
http://reliabilitycalendar.org/Webinars/Chinese.htmlASQ Reliability DivisionChinese Webinar SeriesOne of the monthly webin...
设计更有效的可靠性验证试验Wendai Wangwendaiw@gmail.comMay 19, 2013
ReliabilityReliability is the probability that an item willperform its intended functions withoutfailure for a specified t...
Reliability EngineeringReliability Engineering provides the theoreticaland practical tools whereby product’sreliability (c...
“Reliability Must Be Verified”Prior to acceptance into production / service, aproduct should be evaluated to checkwhether ...
Reliability Demonstration Test• Reliability Demonstration Test (RDT) isdesigned for claiming a specific reliabilityrequire...
Classic Reliability Demonstration Test• Reliability Requirement:• Outcome of n UUT tested under usecondition s(t) to time ...
Practically, Zero Failure Test• Success Run• Test: n units all tested under use condition totime t0 without any failures, ...
Statistical InferenceTest Outcome:no failures aftert0 for all n testunits@ CLGRtstR )(, 00
Practical Issues• Besides a long test duration, a large sampleis usually required.ReliabilityGoalConfidenceLevelSampleSize...
Improved Techniques• Tested under use condition• With/without failures• Classic statistical theory• Non-parametricAccelera...
Stress-Strength InferenceStress StrengthFailures
Min Reliability = Min StrengthUse StressA higherStrength meansa higherReliability.GRRequiredStrength
Strength DemonstrationUse/TestStress Demonstrated“MinimumStrength”GRRequiredReliabilityTestPlanTestOutcomeMinimumStrengthSSI
Better Strength, Better ReliabilityUse/TestStressA betterStrength means ahigher Reliability(at test condition).GR
Be Caution: There May Be a Gap …TestStressRequiredStrengthUseStressActuallyDemonstratedminimumStrengthSame reliability (re...
This Happy Test Result May BiteYou Later …
Test StressDemonstratedminimumStrengthReliability Demonstration“Demonstrated”minimumReliability undertest stress
UseStressDemonstrated thesame minimumStrength at the same CLOverload Success RunTestStressRequiredReliabilityTestTarget• D...
Stress-Strength Reliabilityt00TimeReliabilityunder usestress
Another Look at Overload Success Runt00TimeReliabilityunder teststressReliabilityunder usestresst1Demonstrate thesame reli...
Composite Overload Success Run• Stress-strength relationship – reduce samplesize• Life-stress relationship – reduce test d...
Composite Overload Success Runt00TimeReliabilityunder teststressTestTargett2Demonstratedthe test target ina short duration...
Example – Fatigue TestLog SLog NLog nuseLog ntestLog stestTestTargetActualTargetLog suse
Example –
Summary• SSI concept may help you to plan and execute the ReliabilityTesting correctly.– Pay attention to and understand t...
THANKSANDANY QUESTIONS?
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Plan a more effective rdt

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Plan a more effective rdt

  1. 1. Comprehensive Considerationin Planning an EffectiveReliability Demonstration Test (更有效的设计可靠性验证试验)Dr. Wendai Wang (汪文岱博士)
©2013 ASQ & Presentation Wanghttp://reliabilitycalendar.org/Webinars/Chinese.html
  2. 2. http://reliabilitycalendar.org/Webinars/Chinese.htmlASQ Reliability DivisionChinese Webinar SeriesOne of the monthly webinarson topics of interest toreliability engineers.To view recorded webinar (available to ASQ ReliabilityDivision members only) visit asq.org/reliabilityTo sign up for the free and available to anyone livewebinars visit reliabilitycalendar.org and select ChineseWebinars to find links to register for upcoming events
  3. 3. 设计更有效的可靠性验证试验Wendai Wangwendaiw@gmail.comMay 19, 2013
  4. 4. ReliabilityReliability is the probability that an item willperform its intended functions withoutfailure for a specified time interval underdefined conditions.)(, tstRyReliabilit
  5. 5. Reliability EngineeringReliability Engineering provides the theoreticaland practical tools whereby product’sreliability (capability) can be specified,designed in, assessed, tested out,demonstrated (verified), and monitored witha desired confidence.
  6. 6. “Reliability Must Be Verified”Prior to acceptance into production / service, aproduct should be evaluated to checkwhether the RELIABILITY exhibited under useconditions exceeds the minimum acceptablerequirement.
  7. 7. Reliability Demonstration Test• Reliability Demonstration Test (RDT) isdesigned for claiming a specific reliabilityrequirement with a statistical confidence;e.g.,• The outcome of a RTD is a decision to acceptor reject it (the claim).CL@)(,0 GRtstR
  8. 8. Classic Reliability Demonstration Test• Reliability Requirement:• Outcome of n UUT tested under usecondition s(t) to time t0 has a BinomialDistribution,riinitRtR000 )()(1GRtstR )(,0
  9. 9. Practically, Zero Failure Test• Success Run• Test: n units all tested under use condition totime t0 without any failures, where• Classic statistical theory• Non-parametric)ln()1ln(GRCLn
  10. 10. Statistical InferenceTest Outcome:no failures aftert0 for all n testunits@ CLGRtstR )(, 00
  11. 11. Practical Issues• Besides a long test duration, a large sampleis usually required.ReliabilityGoalConfidenceLevelSampleSize0.90 90% 220.95 90% 450.95 95% 580.99 95% 298
  12. 12. Improved Techniques• Tested under use condition• With/without failures• Classic statistical theory• Non-parametricAcceleratedLife TestingBayesianDegradationTestingParametric(Distribution)
  13. 13. Stress-Strength InferenceStress StrengthFailures
  14. 14. Min Reliability = Min StrengthUse StressA higherStrength meansa higherReliability.GRRequiredStrength
  15. 15. Strength DemonstrationUse/TestStress Demonstrated“MinimumStrength”GRRequiredReliabilityTestPlanTestOutcomeMinimumStrengthSSI
  16. 16. Better Strength, Better ReliabilityUse/TestStressA betterStrength means ahigher Reliability(at test condition).GR
  17. 17. Be Caution: There May Be a Gap …TestStressRequiredStrengthUseStressActuallyDemonstratedminimumStrengthSame reliability (required and demonstrated by test)Lower reliability may be seen in the field.
  18. 18. This Happy Test Result May BiteYou Later …
  19. 19. Test StressDemonstratedminimumStrengthReliability Demonstration“Demonstrated”minimumReliability undertest stress
  20. 20. UseStressDemonstrated thesame minimumStrength at the same CLOverload Success RunTestStressRequiredReliabilityTestTarget• Demonstrated the same reliability with a small sample• Same test duration• Require / apply the stress & strength knowledge)ln()1ln(TGTRCLn)ln()1ln(GRCLnGTG RRnnT
  21. 21. Stress-Strength Reliabilityt00TimeReliabilityunder usestress
  22. 22. Another Look at Overload Success Runt00TimeReliabilityunder teststressReliabilityunder usestresst1Demonstrate thesame reliability ina short duration.The same samplesize.Life-stress relation.
  23. 23. Composite Overload Success Run• Stress-strength relationship – reduce samplesize• Life-stress relationship – reduce test duration• Lifetime information (parametric) – furthertrading off between duration and sample size
  24. 24. Composite Overload Success Runt00TimeReliabilityunder teststressTestTargett2Demonstratedthe test target ina short durationwith a smallersample.
  25. 25. Example – Fatigue TestLog SLog NLog nuseLog ntestLog stestTestTargetActualTargetLog suse
  26. 26. Example –
  27. 27. Summary• SSI concept may help you to plan and execute the ReliabilityTesting correctly.– Pay attention to and understand the effect of different between teststress and use stress.• SSI concept may help you to plan and design a more efficientReliability Testing .– Combining with life-stress relation and lifetime distribution, applyingSSI may further shorten test duration with a smaller sample.• More study is needed to incorporate the SSI into RDT planning.– Theoretical methodologies– Practical tools
  28. 28. THANKSANDANY QUESTIONS?

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