General Mechanical

General Mechanical

Lumped mass method in MDOF

    • oguzhankose96
      Subscriber

      Hello guys,


       I would like to make a modal analysis of a model that has contacts with other substances from many regions. In order to improve CPU, I intend to keep the item I want to analyze and connect it with springs and point masses from the connection points. However, I do not know how to show the 6-DOF reaction of the material I want to simplify with the springs. For example, when I find the stiffness in the x-direction and connect the spring and point mass to the model I want to analyze, what should I do to show the effect of the stiffnesses in the y,z,rotx,roty,rotz? Do you have any suggestions about how to connect springs or another method for a faster analysis? Thank you very much for your help.


      PS: Perhaps there is a method directly adding the stiffness matrix of matter to point mass. I'd appreciate it if you could brief me on this.

    • peteroznewman
      Subscriber

      Please insert an image of the geometry of the model and the springs you want to use.

    • oguzhankose96
      Subscriber
      Unfortunately, I can't upload the model at this time. If possible, I would like to know how to use lumped mass method in ansys.
    • peteroznewman
      Subscriber

      Do you mean you can't upload because of difficulty with the website, or do you mean you can't show what you are working on because it is secret?


      If the latter, then make up a generic model and insert an image of that and we can talk about how you would make a lumped mass version of the generic model.

    • oguzhankose96
      Subscriber
      The following model may be think of a similar model. All contacs are frictional contact. The selected body in the photo is the area we want to analyze. The rear surface of the overhang is the fixed support.
    • peteroznewman
      Subscriber

      I don't see an obvious candidate to convert a piece of this geometry into a lumped mass and connect it with a spring to the main body.



      I do see a possibility of converting this uniform, thin-walled geometry into a midsurface and using shell elements to greatly improve the solution time.


      Here is a good example of a lumped mass model...


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