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  1. aerohead56

    Modeling Composite in NX NASTRAN as solid with Mat9 card

    I think I figured it out after some research. Forget using MAT9. Am going to use MAT12 instead and calculate equivalent laminate properties using the matrix equations found in NASA Reference Publication 1351 "Basic Mechanics of Laminated Composite Plates". This gives a way of calculating Ex...
  2. aerohead56

    Modeling Composite in NX NASTRAN as solid with Mat9 card

    I am trying to perform a NX Solution 601 analysis of a composite laminate so that I can use the nonlinear contact features in Sol 601. I am however backed into a corner. If I model the laminate layer by layer the model is absolutely enormous to get a decent element aspect ratio (>10M DOF). I...
  3. aerohead56

    Checking ANSYS MISO Models

    I have created a model of a dent using Multi-linear Isotropic Hardening in ANSYS. The model is being loaded and unloaded in multiple time steps using an impactor with an enforced displacement. We are trying to check this model to determine if we have accurate results, and my DER has suggested...
  4. aerohead56

    1960's Sikorsky Structures Manual

    Nice try. That brings up some Structural Repair Manuals. I am actually looking for their Stress Manual from back then. I doubt it was ever published into the public domain like the SRMs would have been. This is a long shot at best.
  5. aerohead56

    1960's Sikorsky Structures Manual

    I am looking for a 1960's vintage Sikorsky Structures Manual. Does anyone happen to have one??
  6. aerohead56

    Buckling of Flat Plate with Step Change in Thickness

    The panel in question is ramped up into a pad-up over a spar, so I assume that there is plenty of moment capability in the spar. I have a copy of SOR51 handy, so I'll take a look at that. If you can remember the ESDU number that would be greatly appreciated.
  7. aerohead56

    Buckling of Flat Plate with Step Change in Thickness

    Are there any referencable methods for determining how much step change in thickness needs to occur in a plate to provide at least simple support for buckling? We are assuming a 50% change in thickness forms a support. I've heard of an old BDM method that said 20%, but we can't use that...
  8. aerohead56

    Reference Material

    Okay, I was off a little bit, but that is definately the reference we are looking for. We've searched most of places we can think of already.
  9. aerohead56

    Reference Material

    I am looking for a copy of Lockheed Report 2072. Does anyone happen to have a copy? It is referenced in the interaction equation section in Bruhn (C4.22).
  10. aerohead56

    Short ED in Graphite Composite

    Not a bad idea. We are assuming that full bearing strength is developed at 3D, so I will start at that and calculate 0 strength at .5D like you suggested.
  11. aerohead56

    Short ED in Graphite Composite

    Does anyone know how to analyze short ED conditions in Graphite Composites? Any guidance would be greatly appreciated.
  12. aerohead56

    Plastic Tension Failure

    We are having an interesting debate here at our company. The debate stems from using linear FEM model stresses to predict failure of a material at Ftu. One side is arguing that the linear stress can be used to predict failure based on Ftu due to the example of an axially loaded bar. Obviously...
  13. aerohead56

    Bathtub FItting Analysis Question

    The fitting in question has an A/B ratio of less than 2, so the analysis should be acceptable to use per the limitations specified in LM 88. You are correct in pointing out that the negative d value results in a value for K1 of greater than what is on the chart, which in turn makes the bending...
  14. aerohead56

    Bathtub FItting Analysis Question

    I have come across some tension fitting analysis that seems to misuse the assumptions of Lockheed Stress Memo No 88a. The analysis uses an angle type fitting and arrives at a value for the variable d that is negative. Since this means that the hole actually lies outside the theoretically...
  15. aerohead56

    Hoffman Failure Criteria

    I can access www.aero.iitb.ac.in. I cannot access anything past this in your URL. I tried it with :8081 and :8081/~awarman and cannot access either of these. Do you have another link to this information? Thanks!
  16. aerohead56

    Hoffman Failure Criteria

    I cannot access your link.
  17. aerohead56

    Hoffman Failure Criteria

    We have encountered a composites analysis that uses a Hoffman Failure Index criteria to calculate failure. We have been unable to find any reference information on this. Does anyone know about this criteria or can anyone provide a reference that we can look at?
  18. aerohead56

    Simple cantilever beam

    I STRONGLY disagree that solid models use less assumptions and are more accurate. We have run studies on model convergance in solid models using stress convergence as a criteria in localized locations on a complex part. Using Hex8 elements we show virtually NO convergance. The numbers are all...
  19. aerohead56

    Simple cantilever beam

    We have come to a solution. Be very careful with your boundary conditions. In the fixed end restraint it is important to note that the Euler equation assumes that there is full fixity (all 6 degrees of freedom) at all of the nodes at the interface. When we ran this it produced deflections in...
  20. aerohead56

    Simple cantilever beam

    Can you point me to some literature on this subject? I would greatly appreciate it!! All the engineering textbooks I have just cover the Euler theory. I didn't know that there even was anything else.

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