http://forum.theriac.org/ This is a Reliability discussion forum maintained by http://www.theRIAC.org en Thu, 17 May 2012 23:27:51 GMT vBulletin 60 http://www.theriac.org/forum/images/misc/rss.jpg http://forum.theriac.org/ http://forum.theriac.org/showthread.php?t=14486&goto=newpost Mon, 14 May 2012 17:49:08 GMT On April 25th I submitted a ticket to RIAC regarding a technical flaw in the Automated Databook with NPRD2011. I purchased this as a replacement of... On April 25th I submitted a ticket to RIAC regarding a technical flaw in the Automated Databook with NPRD2011. I purchased this as a replacement of my old NPRD1995 which I have used for a very long time. I noticed that the print function now truncates the operating experience from 0.000000 to 0.00. The loss of significant level of detail inhibits the use of the NPRD2011 to derive composite prior based on similar systems.

I submitted my ticket on April 25th. I finally received a response on May 12th. The response was inadaquate and unsatisfactory. Pointing fingers at standard applications to rationalise the technical flaw is not right. The response "We will have to look into that error." shows a level "caveat emptor" that I've not previously experienced from RIAC.

If I had to complete the purchase survey for the NPRD2011 over, the response would be negative. If I had to respond to a survey on the customer service response it would be negative. And If I had to recommend the use of the RIAC Products, I would have to consider the implications of the NPRD2011 and response received.

As a follow-on, I attempted to respond to the customer service reply. Your customer service ticket system failed to accept or post my comments to the thread. Again, all I can say is "caveat emptor" ]]> Non-Electrical Component Reliability RogerKleinhammer http://forum.theriac.org/showthread.php?t=14486 http://forum.theriac.org/showthread.php?t=14482&goto=newpost Thu, 10 May 2012 19:00:18 GMT Could someone please provide a link where I can find a list of current MIL-STDs? Could someone please provide a link where I can find a list of current MIL-STDs? ]]> Handbooks and Standards jimgues http://forum.theriac.org/showthread.php?t=14482 http://forum.theriac.org/showthread.php?t=14479&goto=newpost Tue, 08 May 2012 16:14:51 GMT My company doesn't have a copy of NPRD 2011 but our reliability prediction software includes it and the components listed have MANY similar failure rates. Upon contacting the software company, they claim accuracy referencing NPRD 2011.

Question is, does NPRD 2011 really have identical failure rates for many dissimilar components?

Anti-Collision Light, General/Arm, Motor/Battery, General/Windshield Panel, General…… ]]> Non-Electrical Component Reliability leifesk http://forum.theriac.org/showthread.php?t=14479 http://forum.theriac.org/showthread.php?t=14476&goto=newpost Tue, 01 May 2012 23:52:27 GMT I am trying to use FIT (failures in time) data for electronic parts. The majority of the data I have found is from accelerated life testing data,... I am trying to use FIT (failures in time) data for electronic parts. The majority of the data I have found is from accelerated life testing data, which includes a temperature adjustment, but no information about the test voltage is typically listed. Does anyone know why the voltage stress/acceleration is typically neglected for FIT data?


More information about what I am doing:

The FIT data that I have received from manufacturers is calculated from accelerated life test data using the following formula:

Failure rate (FIT) = X / [2*N*h*Aft] * 10^9
(units of failures per billion hours)
X = Chi square value for given confidence level and (2n+2) degrees of freedom
n = number of failures
N = number of devices tested
h = number of test hours
Aft = temperature adjustment factor
= exp( (Ea/k)*((1/Toperating)-(1/Ttest)) )
Ea = activation energy (eV)
k = Boltzmann constant
Toperating = operating temperature (K)
Ttest = test temperature (K)

I have also seen a voltage adjustment factor included:
Failure rate = X / [2*N*h*Aft*Afv]
but it is typically left off. Additionally, the test voltage is typically not listed. Since (judging by the MIL217 model) the voltage stress can be significant even for smaller variations in voltage (e.g. for low frequency diodes, the voltage stress factor roughly doubles going from 40% to 60% of the rated voltage), I would like to account for the voltage stress. ]]> Electrical Component Reliability mvogl http://forum.theriac.org/showthread.php?t=14476 http://forum.theriac.org/showthread.php?t=14474&goto=newpost Thu, 19 Apr 2012 19:37:31 GMT I am supporting the evaluation of a continuous use system that collects data for a fixed time period then does an analysis and submits a report of... I am supporting the evaluation of a continuous use system that collects data for a fixed time period then does an analysis and submits a report of the results. The developer has proposed a definition of down time for the system that forces us to retropsectively treat time when the system was up and functioning as down time if the analysis is interrupted and a result is not reported. For example, if the collection takes three hours, the analysis normally takes three hours, a downing event occurs one hour into the analysis that erases the data and it takes three hours to repair the system and bring back online, the definition being proposed would consider the down time to be seven hours rather than the three hours the system was actually down. I'm wondering if anyone has ever run into something like this and if so how did you deal with it? Thanks. ]]> Maintainability/Supportability krivenbk http://forum.theriac.org/showthread.php?t=14474