Forum: Reliability & Maintainability Questions and Answers
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?
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)?
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
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)?
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?
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