Defining a non yearly mission profiles

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Defining a non yearly mission profiles


Fides programm enables to define mission profiles. It seems to be based EXCLUSIVELY on a yearly basis. When the total of hours drifts from 8760, FIT calculation reacts very strangely :

when the period is much smaller (about 2000 H) and temperature quite high (85°C), results are the same as for 8760 hours.

when the period is much bigger (about 160000H) and temperature (high 85°C), results are almost the same as for 1 year and hence 2000 hours !

There are lots of other examples, where it looks as if time is not the major factor but only temperature.

I am quite confused about this issue and would greatly appreciate your support,

Renaud fontenay

Edited by: tourtelier_d on 13/05/2014 - 14:35
Re: Defining a non yearly mission profiles

Dear Renaud,

All models in the FIDES Guide are described with a yearly life profile of 8760 calendar hours. But this is only a default value, and any longer or shorter duration may be used.

If the repartition of phase′s duration remains the same, the calendar failure rate is not a function of the total life profile duration. The total duration of the life profile is not a factor at all, because the result of the prediction is not a probability but a failure rate.

This is true for low or high temperatures, for benign or harsh life profiles.

On an other hand, temperature has a direct influence on failure rate. But temperature is not the sole contributing factor : thermal cycling, mechanical vibration, humidity are the other major physical factor taken into account in a FIDES calculation.

I hope this will help you,