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Recent content by Stezza

  1. Stezza

    Analysis Physics Question

    If it was me I'd do the SOL106 analysis assuming the model is not huge, i.e. the SOL101 analysis solves in a minute or so. Changing a SOL101 to SOL106 to account for non-linear displacement is pretty easy by directly editing the .bdf add LGDISP and NLPARM cards and you are ready to run. If...
  2. Stezza

    Panel Buckling by Enforced Displacement

    I am assuming that you are leaving the rotational enforced displacements blank (as opposed to entering 0.0) on the SPCD card. From my reading of the quick reference guide I think that this means that the edges are free to rotate and thus you have pinned boundary conditions. This is conservative...
  3. Stezza

    Hole fits in hybrid joints

    For our hybrid composite Aluminum structure we use a close tolerance fit for both parts. As you mention installing bolts in interference fit holes in the composite can lead to delaminations in the composite part and reduce the strength of the joint. For the metallic part if you did not have an...
  4. Stezza

    Ultimate abuse load - is a check at limit required?

    Don't forget that there is also a yield plastic bending allowable (this accounts for the fact that some thickness of materials from the outer fiber has to yield before a part permanently deforms). So for materials that have Ftu and Fty close together such as 7075 this means that the ultimate...
  5. Stezza

    Using drawing tolerances as part of justification

    For our stress analysis if the thickness of a part is below about 0.050" we have to analyze the part with a reduced thickness that considers a number of factors but is essentially about half the machining tolerance. So a part that is 0.040" +/-0.010 is stressed for 0.035". Above 0.050" the...
  6. Stezza

    Plate Buckling coefficients

    Sorry, I missed that you were asking for a composite plate, if you are able to get a copy (though as far as I can tell it's not publically available via the NASA website) you should have a look at: DoD/NASA Advanced Composites Design Guide Table 2.2.2.I
  7. Stezza

    Plate Buckling coefficients

    See NACA TN 3781 Equation 48 kc = ((a/mb ) + (mb/a))^2
  8. Stezza

    Aircraft Structures Analysis

    If you are referring to the Practical Stress Analysis by Jean Claude Flabel, then I have done it and it was worthwhile for engineers with up to about 5 years experience as a stress analyst. I would recommend you get his book first or at least have a look at the contents page. The course is...
  9. Stezza

    Joint Analysis

    Thanks for the feedback Rb, I can see now that as would need to do the VQ/I for the complete wing section, then separate the vertical shear between the front and back spars. I was initially thinking that given I knew the front spar vertical shear I could treat the front spar in isolation and...
  10. Stezza

    Joint Analysis

    Hi All, I need to sharpen the pencil regarding a spar to skin joint analysis. I have a global fem with CQUAD elms for the spar webs and skins and rod elms for the spar caps and stringers. There is one skin element between stringers. I already have a freebody force extraction in Patran for the...
  11. Stezza

    why no Kt at fastener hole for limit load?

    For Static strength analysis you use either the A or B basis allowables - the page 3-71 allowables in your case. For a definition of A and B basis see Section 9.1.6 in the MMPDS. If in doubt use A basis allowables - it can only be conservative. While I am not 100% sure my guess is the TYS on...
  12. Stezza

    why no Kt at fastener hole for limit load?

    FAR 25.305 states that "The structure must be able to support limit loads without detrimental permanent deformation" Generally any plastic region around a fastener hole is small and the stiffness of the surrounding material that has not been yielded forces the plastic material back into its...
  13. Stezza

    Fuselage Expansion due to Pressurization

    Oh also thanks for the NACA TN 2612, STRESS PROBLEMS IN PRESSURIZED CABINS pointer Andries.
  14. Stezza

    Fuselage Expansion due to Pressurization

    Thanks for the replies. The FEM gave me a differential deflection between the crown and the passenger floor of 0.17 inches. There was some deflection of the passenger floor downwards (appears to be due to the post being pulled downwards due to the lower fuselage expansion and the SOB...
  15. Stezza

    Fuselage Expansion due to Pressurization

    I am about to set up a model the fuselage cross section of a 767 to determine the expansion between the passenger floor and the crown of the aircraft under a 9.1 psi pressure. Does anyone know roughly what sort of magnitude of expansion I should get so I can be confident that my model is...
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