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Any known limitation on amount of flexible bodies in a model with multiple fixed connections in between?

javier.gutierrez
Hello,
 
I would like to know if anyone has already encountered limitations as the complexity of the flexible bodies increase as well as the number of fixed/bushing connections between them.
While working in a non conventional project, we are trying to do a load cascading with multiple complex flexible bodies with more than 10 connection points between some of them. There is not any rigid part in between them.
 
Is there any general known limitation or rule in order not to fail into wrong loads?
 
We have experience with these activities before with successfull results, but we are wondering in the increase of connection points could be an issue for the load cascading.
 
Thanks,
 
Javier
  • 0
    Hi Javier,
     
    If you have those many fixed joints between two flexible bodies, you need to make sure you have enough number for normal modes requested. In this way, you can make sure that higher order bending and torsion modes can represent the flexibility of the material between these fixed joints.
     
    Thanks,
    Maziar
  • 0
    Hello,
     
    Thanks for the answer. The situation now is that the model is so complex with so many connections between several flexbodies that the simulation time even for static loadcase simulaiton is pretty high and very difficult to manage and handle.
     
    Is there any workaround apart from combining some of these flexbodies to have less number output nodes and so less number of modes per flexbody? The problem with this approach is that we lose the forces in between these parts and we need all of them.
     
    Any idea?
     
    Thanks in advanced!!
     
    Javi
  • 0
    Javier,
     
    1. Have you performed a proper sensitivity analysis on the Solver settings for equilibrium?
     
    2. The number of modes in the flexible body does not depend on the number of nodes.
     
    3. The number of nodes can affect the geometry rendering that can add to simulation time. For this, you need to perform a couple of tasks:
     
    • You need to perform a Mesh Refinement Study on the FEA side and see if you can use coarser mesh but still maintain the frequencies of interest.
     
    • You can make use of the method explain in the article below that shows how you can reduce the amount of mesh, which could help reduce run times, especially for DOE's where the mesh visual representation is not of high importance: simcompanion.mscsoftware.com/.../index
     
    Thanks,
    Maziar Rostamian
    MSC Technical Support
     
     
  • 0
    My first thougth is to split the global simulation into two subproblems where the flexbodies and connections are divided into two smaller equivalent simulations that are easier to be calculated separately and in each of them different cascaded loads are extracted.
  • 0
    Dear Maziar,
     
    I already applied the techniques you explain but this doe snot apply to the calculation time but the viasualization performance.
     
    The number of output nodes in the flexbody where to connect it with other parts increase the number of modes as 6*output nodes.
    Any other idea?
  • 0
    The method explained in the article has been tested in a few models and by some customers where we have seen shorter run times,
     
    Those nodes (where you connect to other parts) are called interface or attachment nodes. Do you constrain all 6 DOF's on all of those nodes on the Adams side?
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