General Mechanical

General Mechanical

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normal stress issue of random vibration

    • zengmin
      Subscriber

      Hello guys. I built a space frame structure model with beam 188 element and run random vibration analysis on it. But the normal stress distribution seems to be wrong. Can u help me find the possible reason ? 

      I choose 9 bottom point as fixed support and apply displacement psd on Zdirection. 

    • dlooman
      Ansys Employee

      Beam postprocessing, especially after a psd analysis, can be difficult.  As a sanity check, could you try displaying the axial stress with the user defined result below?: 

    • zengmin
      Subscriber

      Thanks for your reply. The result is below:

    • zengmin
      Subscriber

      I also added distributed mass and made prestress for modal analysis.But it doesnt effect the normal stress distribution. Here is all my keyopt. They are all default.

    • zengmin
      Subscriber

      My beam sections are several kinds of I section with different parameters and tubular section with different parameters.

    • zengmin
      Subscriber

      I form a part with all line body in designmodeler and chose edge joints as shared topology method

    • dlooman
      Ansys Employee

      Prestress doesn't always change beam results.  There is a nicer capability for displaying beam results on the cross-section in APDL:

      /post1 

      set,last

      /graph,power

      /esha,1 

      /show,png 

      plnsol,s,x        ! beam axial stress will be displayed over a 3D image of the beam

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