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Natural Frequency in Solidworks and ABAQUS

Question asked by Satya Sri Mummidivarapu on Feb 22, 2016
Latest reply on Feb 24, 2016 by Shaun Densberger

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Hello Everybody,

All your suggestions are golden. I have started venturing into Solidworks simulation and have created a Simulation study to determine natural frequency of an assembly. The first five modes from solidworks are 7.3, 11.5, 20.59, 26.58, 55.11. A similar study was done in ABAQUS and the results are 10.59, 41.71, 57.57, 67.3, 330.76. The mesh elements, constraints, material properties and COM are similar in both studies. What are the other details to be considered to evaluate both the studies? ( I have no idea which results are correct)

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Prasad Bhonsule Feb 22, 2016 4:59 PM
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Can you view the modal shapes of each of the modes in ABAQUS as well? I haven't used Simulation for a few months, but I believe that you can animate the modal shape. That might give you a bit of an idea of how you expect the model to resonate.

Kind regards,

Prasad
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- Satya Sri Mummidivarapu @ Prasad Bhonsule on Feb 23, 2016 8:11 AM
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  Thanks for the reply Prasad. The results for modal shapes from ABAQUS are in different directions. However, I see all my modes from solidworks in same direction since I have excited my base with Uniform base Excitation property (seen from animate icon for each mode). What am I missing here?
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  - Shaun Densberger @ Satya Sri Mummidivarapu on Feb 23, 2016 12:39 PM
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    Can you post pictures of the mode shapes? Can you post pictures of the mesh?
    
    "However, I see all my modes from solidworks in same direction since I have excited my base with Uniform base Excitation property..."
    
    This doesn't make sense. A modal analysis (aka solving for the eigenvectors/values) doesn't use any type of excitation. The frequency and shape of each mode is solely a characteristic of the geometry, material, and constraints (and potentially an initial strain field). Can you clarify?
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    - Satya Sri Mummidivarapu @ Shaun Densberger on Feb 23, 2016 12:51 PM
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      Sorry, I haven't given any excitation for Modal analysis. I mistook it for the Random vibration analysis I have done later.
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    - Satya Sri Mummidivarapu @ Shaun Densberger on Feb 23, 2016 12:57 PM
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      Sorry, I cannot post any pictures (NDA), But here are the details of meshing,
      Mesh elements: Shell elements
      Mesher used: Curvature based
      Jacobian points: 4 points
      Mesh quality: high
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      - Shaun Densberger @ Satya Sri Mummidivarapu on Feb 24, 2016 12:55 PM
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        Without looking at the model and its results it's very hard to say why they differ. One potential cause could be the element formulation used in ABAQUS; I'm not sure if by default they use linear elements. Another could be how you handle connects between components (shard nodes, MPC, etc.). It's all a stab in the dark with the little information given.
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Natural Frequency in Solidworks and ABAQUS

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