General Mechanical

General Mechanical

Euler–Bernoulli beam theory

    • Abdulelah
      Subscriber

      Hey, I'm new to Ansys and from what I read on the web I figured that Ansys is using Timoshenko beam theory. I have analytical solution using Euler–Bernoulli beam theory and I would like to compare it with my result from Ansys. So my question is: Does Ansys support Euler–Bernoulli beam theory? If yes how to do it? 

    • peteroznewman
      Subscriber
    • Abdulelah
      Subscriber

      Thanks for the reply. I have been trying to change the element type to beam4 but without success and I'm still confused with using command snippet. Here is what I'm doing: 



      When I run it I got this error: Real constant set 2 undefined but referenced by element 2049.


      and when I add r,2,1 and run it I got zero frequencies. 

    • peteroznewman
      Subscriber

      Did the Solution Output show that Beam4 was the element type being used?


      You can get zero frequencies in a modal if you have not constrained the model adequately.  As a check, suppress the Solid body and apply a fixed support at one vertex of the line body.

    • Abdulelah
      Subscriber

      Yeah it did. I think my problem is with assigning real constants properly. does Ansys take the data from the geometry when I change the element type or should I assign them? 

    • peteroznewman
      Subscriber

      BEAM188, which is the current technology, uses SECCONTROL  instead of real constants, so you should assign real constants 1-8 for BEAM4.


    • Abdulelah
      Subscriber

      It worked. Thank you very much!

    • peteroznewman
      Subscriber

      Please reply with the text you put in the Command Object to help others who might want to do this.

    • Abdulelah
      Subscriber

      sure, below "et,matid,beam4" I wrote the following: 


      r,2,0.0016,2.1333e-7,2.1333e-7,0.04,0.04,0,0,0 


      Where 0.0016 is the area, 2.1333e-7 is IZZ, etc. 

    • ciema
      Subscriber
      Dear Peter, maybe you know if there is possibility to display stresses in beam4 when user-defined cross section was used via Command Object (as in the example above)? I have searched, but cant find clear information if stresses are not available. I found only on one of the forum:nIt is about numerical integration and some finite element method basics.nWhen you define cross section by moment of intertia etc., you don'tndefine integration points in your section, you don't define the shape ofnyour cross-section at all. That's why you don't have stressess.nIn this case your will get always approximate results (for examplendeflection).nn[...] it is impossible to improve this thing. That'snthe way it is calculated in case of sections defined by moment ofnintertia etc. and it is ok.nnI activated Beam Section Results option in Solution, but it does not help.nnMaybe there is another - current technology element which can help to use Timoshenko Theorem and can help display the values of stresses? Or its totally impossible?nThanks in advance for the reply..n
    • peteroznewman
      Subscriber
      nhttps://forum.ansys.com/discussion/25701/cannot-plot-stress-results-for-beam4-element#latestn
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