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Recent content by franck

  1. franck

    Allen variance (oscillator stability) measurement/estimation errors

    Dear all, Once again I would need some of your lights on the following problem. Really, I have to assess the stability of an oscillator. To do this, I have used a very stable oscillator (MASER) and I have compared its frequency to my oscillator through a frequency counter (sampling performed...
  2. franck

    Modeling bolts

    Hi Aerodesign, Please could you point to an article or a book, which describes the "Hush or Harts Smith methods". I have tried on the web for some reference with no success. Best regards, Franck
  3. franck

    Aluminium Peel Shim

    Hi guys, I am wondering if some of you have the approximate value of the compression modulus of an aluminium peel shim. Really, I am going to fill in some gaps with these shims and I am going to take into account their deformation under preload since they seem quite flexible. Best regards, Franck
  4. franck

    Book dealing with polarization mismatch loss

    Hi all, I am wondering if someone could point me to a book or an article, which demonstrates the general equation dealing with the polarization mismatch loss between two ellipses. I have the equation but I would like to understand how it is derived. Best regards, Franck
  5. franck

    CFRP Damping Ratio?

    Hi Sdpe, I have used CFRP tubes for a space structure. For my analysis, I used (with fear since did not know what to expect) a Q of 25 (damping of 0.02) and this led me to conversative accelerations when I compared with the results from a sine test. Best regards, Franck
  6. franck

    maximum frequency suggestion

    Hi EricZhao and Filippo, Actually, for a rocking mode acting on a rotating wheel, the gyroscopic theory predicts that the original mode (static) will split into two speed dependent branches. I have seen this effect on satellite reaction wheels as from wheel speed of 300 rpm but obviously this...
  7. franck

    Basic radiation problem

    Thanks Chicopee for trying to find an analytical solution to this problem! Unfortunately, your equation does not work. First, you forgot (s*As*e/k*Ax) before T#^4 but this is not a big deal. The most important issue is when integration two times T(X)^4 you are finding X^6. Basically, if you are...
  8. franck

    modal analysis and modal participation factor

    Hi Uriel78, I am not sure if I am going to answer properly your post but yes a participation factor can be lower than 1. Really, if you take the example of the cantilever beam, the effective mass of the first mode represents 61% of the overall mass of the beam. Now, if in your modal analysis...
  9. franck

    Basic radiation problem

    Hi Chicopee, Fortunately this is for a space application so no convection. I am ended up solving this simple problem with MathCad since the solution is not really trivial. Best regards, Franck
  10. franck

    Question on Hard Brass

    Thanks all to your valuable posts! Best regards, Franck
  11. franck

    Question on Hard Brass

    Hi all, Once again I would need your light. Really, I received an antenna drawing (which will go to space) made of Hard Brass. I have to perform some mechanical and thermal analysis and I had a look in my book to get the mechanical properties but I have data for the following: Red Brass (85%...
  12. franck

    Basic radiation problem

    I am not a student but unfortunately I am working 6000 kms from my home place where all my technical documents are located. I am just checking if someone would have this info handy before doing the calculation myself. Thanks for your response. Best regards, Franck
  13. franck

    Basic radiation problem

    Hi all, I am wondering if someone has the analytical solution (or point me to a reference book) of the following thermal problem: I have a beam of cross section (Ac), conductivity (lambda), length (L), exposed area to space (As) and finally with an emissivity of 0.8. One end of the beam is...
  14. franck

    Water Meter Vibration Issue

    Just a simple suggestion, why not trying to lower a little bit the frequency by mounting your water meter on a soft interface, which is I think the easiest fix. Franck
  15. franck

    Realist waveform to simulate shock

    Hi Tunalover, For your information in the satellite industry, very usually we use a half sine pulse of 500g with a pulse duration of 0.5 ms (yes 0.5 ms!). Really, we want to simulate a shock coming from a pyrotechnic source, which usually exhibits its main excitation in the 2000 Hz region (a...
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