Forum: Reliability & Maintainability Questions and Answers

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Posted by: Prasad (hariprasad@telco.co.in )
Date posted: Wed Jun 18 5:04:47 US/Eastern 2003
Subject: Sample size
Message:
Hi,
I am working in an automobile company. Can you please help me out, what is the minimum sample size required for Reliability testing? Since there is time and cost factors are involved, How many samples should i take for testing? Is there any standard for deciding sample size?

Replies:
Sample Size
J.L.Romeu Thu Jun 19 16:04:29 US/Eastern 2003

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Posted by: Laurens
Date posted: Tue Jun 10 11:26:50 US/Eastern 2003
Subject: Modern MTBF calculations
Message:
Hi,
I have recently been assigned to develop a new product. Client's require 25 year MTBF, but do not specify the calc method. Looking through our copy of MIL HDBK 217F and performing calculations shows that the product wouldn't meet this (or even come close). What is considered a more up-to-date method of reliability prediction (esp. for items like ceramic chip caps)?

Replies: (list all replies)
Prediction Models
bwd Wed Jun 11 14:12:32 US/Eastern 2003
Credible Reliability Prediction
Larry George Tue Jun 17 19:35:37 US/Eastern 2003

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Posted by: Ken
Date posted: Mon Jun 9 10:07:12 US/Eastern 2003
Subject: FDSC
Message:
Just want to clarify Failure Definition and Scoring Criteria is based on the causes of failure or on the end result. For instance if it a system fails due to an operator fault which results in a Mission Abort failure during Reliability Demonstration (RD). Do we consider this failure chargeable?
I just want to sentence these kind of failures fairly because the supplier argue that despite the end result is Mission Abort or Mission Affecting, the root cause is due to human error and not because of design or quality deficiency. Please advise. Thanks

Replies:
Failure Definition
BWD Mon Jun 9 11:14:55 US/Eastern 2003

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Posted by: Shanta
Date posted: Thu Jun 5 16:12:04 US/Eastern 2003
Subject: Default temperature rise for diodes in PRISM model
Message:
In the PRISM model, the default temperature rise for diodes is 60C. If the system is operating at 40C (average room temperature), the diodes in the system operate at 100C (40+60). Why is the default temperature rise so high? Seems hard to believe that standard, off the shelf diodes, can operate/withstand 100C temperatures.
Since the overall system temperature is 40C, won't the diodes operate at a temperature slightly higher than that? Is the temperature rise only due to internal heating (thermal resistance*power)?

Replies:
PRISM Default Parameters
B.W.Dudley Tue Jul 22 13:06:53 US/Eastern 2003

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Posted by: Gale Powers (g.powers@ericsson.com )
Date posted: Wed Jun 4 13:38:30 US/Eastern 2003
Subject: Vicor Power Module Reliability Data
Message:
Can anyone out there help me obtain demonstrated reliability
data on Vicor 2nd generation Micro modules used in Military ground fixed applications?

Replies:
Vicor Reliability Assessment
BWD Thu Jun 19 15:18:42 US/Eastern 2003

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