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  1. spacecase

    Nonlinear Column Buckling

    A compressive load that causes the structure to bend about the weak axis. In a seperate analysis, I've applied a lateral load in the strong axis direction to look at lateral-torsional buckling.
  2. spacecase

    Nonlinear Column Buckling

    Corus, The fixed Pcr I stated was from a linear buckling run, which would be Eulers. You are correct, the nonlinear run provides only load and displacement data. I agree that Eulers will not be conservative in this case. That is why I turned to the Secant formula and am trying to get some...
  3. spacecase

    Nonlinear Column Buckling

    It is a rectangular cross section: 10mm x 1mm. The length is a little over a 1.25" With the the fixed-free end conditions, the slenderness ratio is 224, should be well into the Euler buckling range. The material is Invar. The nonlinear elements are given large displacement effects which...
  4. spacecase

    Nonlinear Column Buckling

    Corus, I do have large displacement included. I am thinking pertubing the structure is will do the trick. However, from the sounds of things, this may be something of an art.
  5. spacecase

    Nonlinear Column Buckling

    rb1957, If this situation had to take in account yielding of the material, the elastic modulus used in the secant formula should be replaced with a tangent modulus. Fortunately, I can avoid this because everything should still be in the elastic range. The NASTRAN 54lb load ignores the...
  6. spacecase

    Nonlinear Column Buckling

    crisb, The model is made up of a fine mesh of tets w/ midside nodes. It is a flexure that has some bulk added to the base for stress control. rb1957, Fixed-Free boundary conditions refers to fixing the base of the column and leaving the top of the column unconstrained. This is the most...
  7. spacecase

    Nonlinear Column Buckling

    Greetings all, I need to tighten up my buckling analysis and would like to head into the nonlinear realm. I am basically dealing with an eccentrically loaded column. The compressive loads applied to the column are not enough to yield the material, so I should be in the elastic range. Running...
  8. spacecase

    Fastener Proof Testing

    Thank you all for your insight. Several of us here question this testing method as well. But of course before discrediting it completely, we have to figure out where it came from and why it was initially considered acceptable for these purposes.
  9. spacecase

    Fastener Proof Testing

    Greetings all, One of our project teams has expressed interest in performing proof testing on single point failure fasteners to verify structural integrity rather than choosing other nondestructive evaluation methods. Our written standards for this testing specify that fasteners be proof...
  10. spacecase

    Hex vs Tets

    Greg, I am primarly performing stress and normal modes analysis. When working with a situation where the stresses are mainly from bending, is there a rule of thumb for the number of tets a long the thickness? For hex elements I've heard at least four should be used. Thanks again!
  11. spacecase

    Hex vs Tets

    I am a newbie analyst looking to gather the opinion of this great forum. When using solid elements I have been mainly sticking with hex elements, but with some added complexities to my current project’s design I have been leaning towards using tets with midside nodes. What is everyone’s take...

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