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  1. mathlete7

    Fastener Single Shear Allowable Knockdowns

    Hi, I've always been under the impression that for single shear details that aren't stabilized by some other feature (loading causes rotation of the joint) the shear allowable of the fastener is reduced from the standard, "1/2 of the double-shear strength value". For instance, this is reflected...
  2. mathlete7

    Panel Flutter

    I've been told that there are some standard charts that exist to size simply supported panels so you don't run into panel flutter problems. The airflow for the particular problem I'm looking at is only on one side of this panel (OML panel). Has anyone seen something like this? I'm looking for...
  3. mathlete7

    Allowable for Orbital Nitronic Weld

    Hi, I'm trying to track down an allowable for a Nitronic (21-6-9) orbital weld. I've been told that 32% is the appropriate knockdown to apply but I'd like to find a reference that supports this. Does anyone know of anything? Thanks much...
  4. mathlete7

    Acoustic FEA Analysis

    Just a random "rain on the roof" forcing... Any suggestions (tutorials, textbooks, webpages, etc)? Thanks...
  5. mathlete7

    Acoustic FEA Analysis

    Hi, I'm looking for a good tutorial on performing low frequency acoustic response analysis via Nastran (structural vibroacoustic response of panels to acoustic loading, etc). Does anyone know of any good tutorials or textbooks that go over this topic? I'm looking for something that will have...
  6. mathlete7

    Crack Growth reference

    Thanks Gbor. The references you gave me are adequate for my purposes. I'm not looking to get too deep into the analytical side right now, more just basic overview level so free and generalized is perfect! Thanks again...
  7. mathlete7

    Crack Growth reference

    Hi, I'm looking to purchase a textbook on the topic of crack growth. Sort of a Bruhn or Niu equivalent in the crack growth field. Does anyone have any recommendations? thanks much
  8. mathlete7

    Biaxial Yielding Failure Criteria

    Hi, I have a problem in which I have a metallic liner (AL6061-T4) in a pressure vessel which is designed to yield biaxially during pressurization. My question is, what would be the ultimate failure criteria for this condition? That is, what combined stress state would be the most appropriate...
  9. mathlete7

    Composites Failure Question

    Hello, I have a question about interlaminar shear failure of composites, specifically pertaining to finding an appropriate interlaminar shear stress using Nastran. I'm analyzing a carbon fiber overwrapped pressure vessel (COPV). In the region I'm looking at I have modeled two plies; one 17 deg...
  10. mathlete7

    Carbon Steel Bearing Allowables

    hi, so I'm looking at some steels that I can't find published bearing allowables for (Fbru for A500, A36, etc). does anyone know any rules of thumb for establishing a bearing allowable as a function of Ftu, Fsu, etc? For instance, I know that for steels Fsu ~ 0.6Ftu. Does such a rule of thumb...
  11. mathlete7

    Web Stability and Point Loads

    agreed. i would definitely classify my company as a "fly-by-night" organization. we're a case study in why having designers do their own analysis is a bad idea.
  12. mathlete7

    Web Stability and Point Loads

    i wish. i'm looking at some hardware that was designed by someone else and the analysis was done very poorly (essentially wasn't analyzed). so now i'm stuck with a poor design that "we don't have time to modify" and i need to figure out a way to show it good. or at least that nothing...
  13. mathlete7

    Web Stability and Point Loads

    Correct, the lower cap of the upper beam is pressing into the upper cap of the I-beam. That's a good idea using the effective "tee-section" and checking for bending. That would certainly demonstrate capability at ultimate loads. I was trying to think through whether the I-beam web would buckle...
  14. mathlete7

    Web Stability and Point Loads

    well, this is a static test fixture and its essentially a box section sitting on top of an i-beam. So in this application the upper beam will press into the web of the lower I-beam. i've never actually known what the failure mode would look like with an unstiffened web in a configuration like...
  15. mathlete7

    Web Stability and Point Loads

    Hello folks, So, we all know about the basic design practice of using stiffeners at all locations where point loads are introduced into beams, right? For instance, if you have an I-beam that is loaded in the middle you'd put a stiffener where the point load is introduced to stabilize the web...
  16. mathlete7

    Bruhn Crippling Equation

    yeah, i kind of was thinking that perhaps "g" is already wrapped into the equation for the z, j, and channel sections since that factor is so high (3.2). I was leery to run with this however cause, while it seems like both a "z" and a channel section would have the same "g" (g=5 per the method...
  17. mathlete7

    Bruhn Crippling Equation

    thanks for the reply rb. right, i saw figure 7.6 which shows you how to calculate g. however I was actually asking why the "g" term isn't shown at all in equation C7.6 (for z, j, and channel sections). however it IS in equations C7.4 and C7.5. I was wondering if this was an error in the...
  18. mathlete7

    Bruhn Crippling Equation

    Hi, I'm looking at my copy of Bruhn, pg. C7.2, equation C7.6. This equation is missing the "g" term (which are present in C7.4 and C7.6) and I'm guessing that this must be an error. Is anyone familiar with this? Thanks much.
  19. mathlete7

    Fatigue limit rules of thumb

    Does anyone know of any rules of thumb for estimating fatigue limits for various metallics (steel/aluminum) as a function of Ftu or Fty? Just looking for something for quick and dirty checks. Seems like I've heard of rules of thumb in the past (infinite fatigue life at Ftu/3 or something of...
  20. mathlete7

    Element Forces

    Well, that could involve a pretty length response but here's a shortened synopsis: Loads models are generally pretty coarse (1-element deep floor beams and frames, etc). They exist only for pulling loads. Loads in FEMs exist in the form of gridpoint forces and element forces. For plate...

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