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  1. jean15paul

    Eigenvalue buckling due to horizontal load

    Thanks NRP99. Regarding the OP's question about trying to recreate the horizontal buckling solution with a hand calculation. I don't think there is any traditional hand calculation to arrive at a similar solution. This was implied by a few replies here, but I don't think it's be said directly...
  2. jean15paul

    Eigenvalue buckling due to horizontal load

    It would be interesting to use the eigenvalue for the buckling under horizontal load and determine your critical buckling load. (Just multiply the eigenvalue by the applied load.) Then use that load to calculate stress values. My suspicion is that those stresses will exceed the material...
  3. jean15paul

    FEA - Theory vs Practice

    Let me start off by saying that I have a lot of experience with linear static FEA, but none with CFD, so my comments will reflect my experience. There is some good advice in this post, but not a lot of specifics. So I will provide a few specific resources. First I'd say that most CAE engineers...
  4. jean15paul

    Bolt analysis, applying preload

    In my experience we always use spring elements, rigid elements, bar elements, or some other type of connector (depending on the specifics of the application and what the software supports). Then we recover forces from the elements representing the bolts and use those forces in a non-FEA bolt...
  5. jean15paul

    How to force a Buckling / Eigenvalue analysis to ignore beam offsets?

    Thanks for the reply stresscalcs. I'm using Patran 2012 and MSC Nastran 2012. In the time since I posted this I found some information on the new capability in MSC Nastran to correctly consider offsets in buckling and nonlinear analysis. It's done through the use of the MDLPRM card...
  6. jean15paul

    How to force a Buckling / Eigenvalue analysis to ignore beam offsets?

    Hi everyone. I'm trying to run a buckling analysis on a model that has a lot of stiffened plates, where the plates are modeled with CQUAD4's and the stiffeners are CBEAM's with offsets. When I try to run the linear buckling solution (SOL 105), I get a fatal error for each offset element that...
  7. jean15paul

    Reading Axial loads from a FEM Model with gravity load

    Creating a FEM model and applying the gravity load seems like a good approach, but make sure you correctly account for the stiffness. If they stiffness aren't correct it will change how the load get distributed through the structure. You said "sandwich honeycomb panel structures". Do they...
  8. jean15paul

    Solve problem with *inital conditions command

    What software package are you using? This stie has forum for all the popular programs. Since this is a question about a specific error, it may be better to post this question in the forum for that specific software.
  9. jean15paul

    Local Stress / Hot Spot / Stress Concentration??? problem

    I 100% agree with the advice to do some hand calcs to validate your results. Assuming you hand calcs don't reveal a problem with your model, then I'd say you probably do have a real problem that you need to solve. If you're asking HOW to solve your problem, then I don't think anyone hear can...
  10. jean15paul

    How Small is Small deformation

    Are you looking for the theoretical answer or a rule of thumb? For a rule of thumb I've heard the "grey-beards" at my work say that you want your deflection to less than 10% of your thickness, in addition to making sure you're in the linear stress range for the material. For example if you're...
  11. jean15paul

    Can see MPC's / RBE's

    Thanks ZeroExperience. Can you tell me how to run PCL commands? I understand how to create the p3epilog.pcl file to make this happens at the time I convert a database, but I don't know how to excute the commands on an existing database that has already been converted. Thanks again.
  12. jean15paul

    Need an intro to Bode plots & Campbell diagrams w/ theory behind them

    Thanks IRstuff. Yeah, the Nastran forum will probably be more help in how to actually create these plots, but before I get into that, I'm trying to understand what they are. I thought this was a better forum to ask. I'm really looking for background theory. "IF you imagine a spot in your...
  13. jean15paul

    Need an intro to Bode plots & Campbell diagrams w/ theory behind them

    A little background: I have about 8 years of experience, but all of my experience has been with static analysis of structures. I recently started a new job where I'm responsible for both static and dynamic analysis including analysis of drive trains. I've been doing a lot of normal modes...
  14. jean15paul

    Can see MPC's / RBE's

    Has anyone ever had a problem with not being able to see MPC's in Patran? I'm working with a model that I'm been using for some time. I just upgraded to 2012 and now I can't see the RBE2's that are there. I can highlight and select them with the mouse, so I know they are there, but they won't...
  15. jean15paul

    Is it possible to Mirror MPC's in Patran

    Thank you SO much Onda! I haven't tried this yet, but I definitely will. This will save me SO much time.
  16. jean15paul

    How to determine exhaust gas induced vibrations?

    Wow. Thanks for all the insightful responses everyone. Being new to eng-tips.com, I'm very impressed how helpful everyone is. This is an propulsion system for a new ship. It hasn't been built yet. I was recently asked for a time estimate to do this analysis whenever the project get started...
  17. jean15paul

    How to determine exhaust gas induced vibrations?

    Thanks for the help ajamnia. That makes sense. Unfortunately I don't have the aero-fluids background to figure out the aerodynamic effects. One thing I'm struggling with at this new job is that they don't have any old timers that I can ask questions. My last job was full of them, and they...
  18. jean15paul

    How to determine exhaust gas induced vibrations?

    Hi all, This is my first post in this forum. I have a problem that I'm not sure how to approach. I'm going to be doing an structural and thermal analysis of an engine exhaust system. The scope of work specifies that I need to consider "exhaust gas induced vibrations." Does anyone have any...
  19. jean15paul

    Is it possible to Mirror MPC's in Patran

    Hi all, I'm trying to mirror RBE2's in Patran 2011, and I can't find a way to do it. Finite Elements > Transform > Element > Mirror won't let me select MPC's. Neither will Utilities > FEM Transform... I just spent a lot of time modeling half of a symmetric structure with the assumption that...
  20. jean15paul

    Symmetry contraint with dymanic/modal analysis

    Thanks. I appreciate the feedback. @henki, Question: What is "Cook's book"? Sounds like it's potentially a good reference.

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