louis DEQUIDT asked 8 years ago
hank you for the answer.
So, There is no method known for uses MIL-HDBK-217F N2 negative temperature.
1-Is it possible to use the temperature converstion method as proposed in the following documents:
• Research notes “Limitations and extended applications of Arrhenius equation in reliability engineering. “Document January 3, 1978
• Reliability Prediction For Military Avionics – RSFN Reliability Prediction Method No. 250 Issue 1 (Royal Signals and Radar Establishment)
2-Is the new draft version of the MIL-HDBK-217G standard allows calculating with negative value?
3-I see in the literature increasingly refers to the “MIL-HDBK-217G draft 4”.
I try to provide the “MIL-HDBK-217G draft 4”.
Can you tell me how I can get the the “MIL-HDBK-217G draft 4” standard?
rwisniewski Staff answered 8 years ago
As was previously stated, MIL-HDBK-217F states that extrapolation of the models beyond the tabulated values is invalid. The underlying equations that are used to calculate the PI T factors are mathematically valid in the sense that a specific input value of T would result in a unique output of PI T. However, it is the application of this resulting PI T to the base failure rate models that is invalid.
If your application requires negative temperatures, you might consider 217PlusTM:2015. 217PlusTM is a reliability prediction methodology that was developed as a potential replacement for MIL-HDBK-217FN2. Base failure rates contained in 217PlusTM are calculated from field data obtained from temperatures over the military temperature range. As a result these models would be valid at negative temperatures, as long as the components do not exceed their maximum ratings. A complete description of the 217PlusTM methodology, including failure rate models, is presented in the Quanterion Solutions publication: “Handbook of 217PlusTM Reliability Prediction Models 2015”. This publication and a corresponding software tool are available on the rmqsi.org website.
I have not seen the proposed MIL-HDBK-217G document, so I am unable to comment on its methodology. It is my understanding that this proposed revision to MIL-HDBK-217 has not yet received final approval.