Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. jimkinney

    Campbell diagrams are over rated ?

    For a shaft or a system with a single load (disk, blade, etc.) they're not useful. If you have a gas turbine engine with lots of disks, each with a different number of blades they're very useful. Trying to navigate shaft speed through multiple blade passing frequencies can be a pain. Jim Jim...
  2. jimkinney

    Bruhn, The source of Fig.C11.46

    The 119p supplement to Bruhn is available on Archive.org https://archive.org/details/BruhnSupplement/mode/2up McCombs was also one of the authors of AFFDL-TR-67-184 Analytical Design Methods for Aircraft Structural Joints while at Vought. Jim Jim Kinney Kennedy Space Center, FL
  3. jimkinney

    Sine Environment

    Usually you want the response of the structure to be outside of your vibration frequency of interest. Then you don't usually have to worry about the structure responding the vibration. This only works if you know exactly what you frequency of interest is. For space applications, random...
  4. jimkinney

    No of cycles in a sine test

    Typically we test 20-2000Hz at 1-4 octaves per minute. So 100 to 400 sec * 2000 Hz = 200000 to 800000 cycles at peak stress. Usually our loads are low enough that we don't worry about fatigue, but we have to check the box that we looked at it. If it were critical, then you are correct about...
  5. jimkinney

    Automotive Steel Design Manual

    I have so many copies of parts of textbooks, manuals, analyses from coworkers, etc. from over the years, that I wish I had the originals for. Some aren't complete, some are illegible, and some may have had other useful stuff that I didn't copy. Live and learn. That may be an SAE manual, you...
  6. jimkinney

    No of cycles in a sine test

    You could calculate the actual number of cycles at each frequency fairly easily from the sweep time, but for fatigue calculations we conservatively use the highest frequency and assume the entire test was at this frequency. It's quicker too. Jim Jim Kinney Kennedy Space Center, FL
  7. jimkinney

    damping determination at 20kHz

    Method suggested by Greg at much lower frequency. https://www.youtube.com/watch?v=PnsFFhKqXXo Jim Jim Kinney Kennedy Space Center, FL
  8. jimkinney

    shock response as random vibration

    You can't readily go from SRS to PSD. You can reverse Miles' equation, but there are limitations on the shape of the PSD. The easiest method might be to synthesize a PSD, convert it to a Vibration Response Spectra (VRS) and compare it to your SRS. This would be an iterative process, and steps...
  9. jimkinney

    Python code

    Tom Irvine has a Python Blog and a wiki on his Vibration Data website that might be helpful. http://vibrationdata.wordpress.com/category/python/ http://vibrationdata.com/python-wiki/index.php?title=Main_Page Good Luck, Jim Jim Kinney Kennedy Space Center, FL
  10. jimkinney

    poured concrete wall house

    Didn't design it, but live in one. Based on other housed built after mine, it has re-bar not WWF. Single pour, so no cold joints, but there are no control joints. Settling cracks pop up all around so have to keep after it with caulk to keep sealed. Being in hurricane country this is a...
  11. jimkinney

    Relating Random Vibration Cycles to Failure to Time

    I don't have it handy, but Steinberg covers random vibration fatigue in "Vibration Analysis for Electronic Equipment" Jim Jim Kinney Kennedy Space Center, FL
  12. jimkinney

    Likelihood of SRS overtest/undertest?

    If you don't have the data from the control accels mounted to the shaker head (or test fixture), or response accels mounted to the DUT, it doesn't count. Inputs to the shaker rarely matches what the DUT actually sees. Jim Jim Kinney Kennedy Space Center, FL
  13. jimkinney

    'Focussing' scattered light

    What about a Panoramic Annular Lens? Not quite scattered to prismatic, but closer. Jim Jim Kinney Kennedy Space Center, FLhttp://files.engineering.com/getfile.aspx?folder=d5918002-b83b-41e6-9d84-7b122339ae56&file=sem.org-2007-s29p03.pdf
  14. jimkinney

    How to convert g^2/HZ to g ?

    ...acceleration of the whole spectrum. If you are only interested in a specific frequency, then you need to use Miles' Equation: Grms = sqrt( pi/2 * f * Q * ASD ). ASD is the PSD value at the specific frequency, and Q is typically (but not always) 10, it's based on the damping ratio if you...
  15. jimkinney

    Accelerometer Calibrators

    I recently acquired a pair of accelerometer calibrators. An APS Dynamics Model 129 low frequency, and a Bouche Laboratories Model 1000 high frequency. Both were filthy, but appear to be nearly unused once cleaned up. There are no electronics for either. My question, is there somebody that...
  16. jimkinney

    Can you re-use a Keensert?

    If they are locking inserts, there is even less re-usable life. The deformable thread type are usually good for 6-12 uses then they won't lock anymore. The threads are ok, but they won't stay locked. Locking life is even less if they are over-torqued. Jim Kinney Kennedy Space Center, FL
  17. jimkinney

    Resonance dwell nomenclature

    Dwelling at a fixed frequency. Some tests will step from resonance to resonance dwelling at each for some period of time. We did this a lot during gas turbine testing to gauge the life of the engine structure as the turbine sped up to operating speed passing through each components...
  18. jimkinney

    Buckling Composite Curved Panel

    Part VI is NACA TN-3786 and is here: http://ntrs.nasa.gov/search.jsp?R=209038&id=9&as=false&or=false&qs=Ntt%3DHandbook%2Bof%2BStructural%2BStability%26Ntk%3Dall%26Ntx%3Dmode%2Bmatchall%26Ns%3DHarvestDate%257c1%26N%3D0 Jim Jim Kinney Kennedy Space Center, FL
  19. jimkinney

    FLITCH BEAMS - STEEL ON OUTSIDE OF LUMBER

    Can you add additional timber outside the steel plates? That would control buckling. Jim Jim Kinney Kennedy Space Center, FL
  20. jimkinney

    Shock Testing Requirement Reasoning

    That's a good question, and so far the only answer that I can come up with is that we have always done it that way, which isn't always a good answer. It's in MIL-1540C as you mentioned, but it's also in NASA-STD-7003, IEST-RP-DTE032.2 and even ESA standards. I haven't confirmed it yet, but I...

Part and Inventory Search

Back
Top