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  1. inertia4u

    Is an AMOC needed for a double drilled hole?

    I recommend you call the ACO or the engineer listed on the AD to get your answer. Everything posted here is speculation. PK ----- Nert
  2. inertia4u

    Citation Request for "St. Mech. Note 15. Short wave Buckling of Stiffened Sheet"

    Hi FJCV - I spent last weekend looking for alternate references - namely because I know I've seen that "Figure 4" plot before from another reference. NO luck. That being said, my guess is that "St. Mech. Note 15" is may be an internal Grumman technical note. Out of curiosity, have you tried...
  3. inertia4u

    aircraft loads and load path question

    nolovenodie: Another option is for you to try finding an experience engineer and make him/her your mentor. Keep pestering your mentor until you get a grasp of it. If you still don't get it, ask around. One thing I've found over the years is that if the engineer knows "it" and "understands...
  4. inertia4u

    Plasticity correction

    I'm sorry, but I disagree with rb1957. You can not cripple sections which are flat. You need corner in order to get a "crippling stress." Wingsmith, I recommend you take a look at the Handbook for Stability (do a search in the NACA Technical Report Server for that title). I've done some...
  5. inertia4u

    Need connection forces

    Hi tg, AC stress guys don't do any welding analysis, unless it is on secondary structure (like scuff plates near door openings), and then if necessary, the analysis is very simplistic. Good Luck, Nert ----- Nert
  6. inertia4u

    From Airline Structure Eng. to Stress Eng.

    Oh, and don't feel like it is to late. A good buddy of mine 2 years ago did practically the same thing, and he is older. ----- Nert
  7. inertia4u

    From Airline Structure Eng. to Stress Eng.

    Come on over, youngin' :) Brush up on your classical analysis techniques, and you'll be set. ----- Nert
  8. inertia4u

    1.15 Fitting Factor

    I think mcclain hit the nail on the head. ----- Nert
  9. inertia4u

    Bulkhead Cut Outs

    Fatigue will be your main problem. My first stab at reinforcement would be as follows: I would up the gauge to 0.032". Install minimum of 3 1/2 rivet rows around the cutout. Allow for generous radius for the cutouts. ----- Nert
  10. inertia4u

    what is "the skin is pocketed above lap joint"?

    For those still wondering, "pocketing" is indeed the chem milled pocket of skin (reduced thickness). ----- Nert
  11. inertia4u

    Inelastic Plate Buckling

    mathlete7, Yes you can set the division between elastic to inelastic at the yield point - which is a slight over estimation. This is because what you are interested in the proportional limit of the material, which can range between 70-80% of Fy or aluminum materials (See MMPDS regarding how to...
  12. inertia4u

    Column Buckling Analysis

    Richard, Per your first paragraph, yes, the McComb chart essentially comes up with an effective length column based off of the rotational stiffness at the ends of the column. I am not aware of how ESDU actually does this, however. Regarding your second paragraph, yes, you are correct. The...
  13. inertia4u

    Column Buckling Analysis

    stresscalcs, A very hand reference I found for columns, beam columns etc is William McCombs Engineering Column Analysis The Analysis of Compression Members I ended up picking it up from thattechnicalbookstore for around $40US I double checked and he does have long column with elastic...
  14. inertia4u

    Johnson-Euler Buckling

    One more thing, It may be that you are assuming that J-E follows along the Euler curve (which is typically shown in structures manuals like Bruhn, etc). But this really isn't the case. The J-E equation and the Euler Eqn are 2 different equations which intersect at 1 point. The J-E curves...
  15. inertia4u

    Johnson-Euler Buckling

    mathlete7, No, you should not just do J-E as default. In fact, if you were to use J-E on a long column, it is possible to get a negative value (tension) as a result, which of course doesn't make sense. As an exercise, just plot the J-E equation as a function of L'/rho and then Euler as a...
  16. inertia4u

    Johnson-Euler Buckling

    Let me clarify something. The very first check for column stability is if the structure resides in the long column (Euler) or short column range (Johnson-Euler). This seems to be missed by a lot of engineers. ----- Nert The most important step in column buckling checks is to determine if...
  17. inertia4u

    Johnson-Euler Buckling

    mathlete7, You are right about the biggies not really talking about it. And I really don't know why it isn't mentioned. I spent some time investigating compression failures of structure because I find it extremely interesting. Unfortunately, I've only looked into torsional instability in a...
  18. inertia4u

    Johnson-Euler Buckling

    mathlete7, I think I know what you are referring to. Correct me if I'm wrong, buy you are asking about the interaction of the local buckling on column stability. I've seen this topic mentioned both in the BDMs when I used to work for Boeing, and I've also seen it in the old Grumman Structures...
  19. inertia4u

    FtuX1.5

    I've seen the 1.5 factor applied to both Ftu or Fty. It depends on how lofty of a goal you are trying to obtain. Against Fty, you are calculating moment with yielding of the extreme fiber. Against Ftu, are you calculating "Ultimate" moment that can be carried by the structure. You *must*...
  20. inertia4u

    FtuX1.5

    One last thing, I wouldn't expect to see stress notes completed with just the 1.5Ftu without some sort of engineering justification. ----- Nert

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