Forum: Reliability & Maintainability Questions and Answers

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Posted by: T. Thompson (thomas.a.thompson@kodak.com )
Organization:Kodak
Date posted: Thu Jun 7 11:13:41 US/Eastern 2001
Subject: Mechanical Wear-in
Message:
I have a fractional horsepower actuator motor gear and am looking for resources on how to determine acceptance test levels and ESS type (wear-in) test(s) on the actuator. Guidance on applicable Mil Handbooks, books, etc would be most helpful.

Replies:
ESS Wear-in Testing
Bruce Dudley Thu Jun 7 15:29:00 US/Eastern 2001

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Posted by: Diane Gordon (info@reliability.com )
Organization:Reliability Center, Inc.
Date posted: Thu Jun 7 9:51:32 US/Eastern 2001
Subject: Resonance
Message:
Does anyone know who discovered "Resonance?"

Replies:
Origin of Resonance
Bruce Dudley Thu Jun 7 13:57:03 US/Eastern 2001

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Posted by: John
Date posted: Thu May 31 23:40:56 US/Eastern 2001
Subject: Field Data
Message:
When analyzing field data for specific part failures (like an electric motor)in a large population - Do you use time to first failure for unique units and then do Weibull plots? Do you ignore any follow up failures of this part in these units? The sample size would be several hundred units.
I would like to use this information in determining base failure rates for future reliability predictions. Thank you

Replies: (list all replies)
Field Data Analysis
Patrick Hetherington Fri Jun 1 7:15:38 US/Eastern 2001
Estimate renewal process
Larry George Tue Jun 5 13:44:11 US/Eastern 2001

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Posted by: Bob Valerius (robert_m_valerius@md.northgrum.com )
Organization:Northrop-Grumman Oceanic & Naval Systems
Date posted: Thu May 31 12:58:25 US/Eastern 2001
Subject: Modeling failure data
Message:
Hi
I have been asked to look at different methods for modeling failure data. On one of our programs, we model the reliability by using predictions from various sources. This program has been in test (sample size = 1) since 9/99. The approach we are taking is that when a component or subassembly fails, we replace its predicted failure rate with the actual. This of course almost always results in a lower reliability estimation. When the FRACAS procedure results in a corrective action being implemented, we then replace the actual failure rate with the predicted failure rate. This is how we report monthly on our reliability metric. Does know of a reputable alternative approach? It has been suggested that since predicted failure rates are an average, to replace the predicted one with the actual, which is only 1 data point, is way too conservative. Any ideas or suggestions would be appreciated. Thank you very much. Bob Valerius 410-260-5247

Replies:
Combining failure data
Bruce Dudley Thu May 31 15:02:51 US/Eastern 2001

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Posted by: C
Date posted: Mon May 28 11:01:41 US/Eastern 2001
Subject: Confidence Levels
Message:
Could somebody explain confidence levels for me. What does it mean when it states a 90% or 60% confidence level and how do determine the confidence level to use? How do the results change for these confidence levels?
Thanks for any help given.

Replies: (list all replies)
Confidence Levels
Richard Smith Tue May 29 10:44:00 US/Eastern 2001
Confidence Levels (again)
Richard Smith Tue May 29 10:53:15 US/Eastern 2001
Confidence Limits
Anthony Coppola Thu Jun 7 8:42:05 US/Eastern 2001

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