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  1. LiftDivergence

    Moment of inertia using Coordinate system

    I don't think you want to look at Niu, Megson, or Bruhn for this. Instead look in any Strengths of Materials / Mechanics of Materials Textbook, look in the index, and find where they cover topics like "moment of area for composite shapes", "parallel axis theorem" etc. These methods generally...
  2. LiftDivergence

    Learning how to calculate secondary moment using Bruhn's

    Just to clarify, are you only interested in the secondary bending moment specifically? Not to be pedantic, but what Bruhn works down to is the location and magnitude of the maximum moment, or the formula for the moment at and point along the span. But these would be for the total moment due to...
  3. LiftDivergence

    Inter rivet buckling using Tangent modulus

    This is true, crippling is a failure stress, although to be crippling critical you need an L'/rho usually <20 and this is really only a term used for failure of thin-walled members of stiffened shell structures. That is one form of post-buckled strength but not the only one. Flat plates in...
  4. LiftDivergence

    Inter rivet buckling using Tangent modulus

    Alteon was a company that did structural analysis training for engineers and was acquired by Boeing. So it's a Boeing company but they have a lot of training slides/notes out there that are not proprietary material. In this case I just did it graphically. Use the stress-strain curve, draw a...
  5. LiftDivergence

    Aircraft - Fatigue Load Spectrum

    In that case the reference data I mentioned is not going to help you. It sounds like this is not really a question of how to do fatigue analysis, but rather what you're asking is effectively: "How do I develop an operational loads envelope and spectrum for this UAV?" Usually this would be...
  6. LiftDivergence

    Aircraft - Fatigue Load Spectrum

    Well there is quite a bit of data out there regarding gust and maneuver exceedance curves for commercial aircraft. Just try searching: "dot/faa statistical loads data for commercial aircraft" For example: https://apps.dtic.mil/sti/tr/pdf/ADA378308.pdf Theoretically if you have a CFD that...
  7. LiftDivergence

    Inter rivet buckling using Tangent modulus

    I went through and calculated critical interfastener buckling strengths based on the references I outlined above and the info you provided. Here are the results: 1. Peery using the Secant Modulus corresponding to Sigma_0.7 (MMPDS-2023 Figure 3.2.4.1.6(i)) on a tensile stress-strain curve to get...
  8. LiftDivergence

    Inter rivet buckling using Tangent modulus

    So there are a few things that can be a bit confusing about general interfastener buckling methods. What you'll find is that they typically rely on indexing column buckling curves from Euler-Engesser relations rather than starting from derived plate buckling formulas from Gerard or Kuhn, etc...
  9. LiftDivergence

    Backdrilling, or "match-drilling"

    In my experience, match drilling and it's counterpart match-forming are generally not specified in much detail on a repair plan / repair instruction or installation instructions. As a stress liaison / repair engineer you learn to tow a balance between being specific enough in your instructions...
  10. LiftDivergence

    aircraft passenger cabin stub beam

    I understand the caution with this data and I also would not necessarily recommend posting the SB in a thread like this. Having said that, the SB is mandatorily incorporated by FAA final rule via AD and it is standard practice for the FAA to provide all data necessary for compliance with the AD...
  11. LiftDivergence

    Steel Sleeve Around Bearing

    Respectfully, I think I understand the problem. OP said: He's saying the O/D of the bearing is set into an aluminum housing and he wants to know if there should be a steel sleeve press fit into the housing to act as a wear layer between the OML of the bearing outer race and the inner face of...
  12. LiftDivergence

    Steel Sleeve Around Bearing

    RB, the source of this graph is originally from Rabinowicz who "wrote the book" on wear, so to speak. The source of the figure from Norton is actually from the Wear Control Handbook by MB Peterson and Wo Winer. I have done some checking to make sure it is correct. I think the thing to keep in...
  13. LiftDivergence

    Steel Sleeve Around Bearing

    What makes you say none of us understand the configuration?
  14. LiftDivergence

    Steel Sleeve Around Bearing

    There are some models that cover fretting fatigue and abrasive or adhesive wear. I'd have a look through some of the classics. I have done these type of calculations to inform inspection requirements/schedules for pin/bushing interfaces before. A good reference is Robert Norton's "Machine...
  15. LiftDivergence

    Wing Skin Loading

    The premise of the question is also confusing. Aerodynamic pressure would certainly contribute to the stress in the skin. However, I would expect a skin panel to primarily be sized by it's ability to take tension and shear loads as part of a box beam structure reacting wing bending loads (yes...
  16. LiftDivergence

    SpaceX Starship missions

    To be clear, I wasn't implying that they will try to "catch" anything on the moon. I'm just talking about their reusable boosters. I wasn't stating anything about their off-earth infrastructure at all. What I'm saying is that their "stage 0" on earth, their launchpad, is the same infrastructure...
  17. LiftDivergence

    Please Explain the "Reaction Score" System

    I know staff is probably inundated at the moment, but I'm still hoping for some clarification on this.
  18. LiftDivergence

    Please Explain the "Reaction Score" System

    Try going to the bottom of the page and clicking on "style chooser". Then switch to "default style" and see if you prefer that.
  19. LiftDivergence

    Please Explain the "Reaction Score" System

    I see in the forums that each post now keeps track of a "reaction score" (the thumbs up). Based on how this is accumulated (the up/down arrows on the right of each post), it seems like this is intended to be a direct replacement to the "little purple star" system. However, on the members...
  20. LiftDivergence

    Glass Analysis

    Well, it really depends on what you are doing. As others have mentioned, it's a sensitive material to work with and I imagine most of the time critical loads are going to be dictated by boundary conditions and contact mechanics. But in general, like all materials, pure tension or pure...

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