1 Reply Latest reply on Jun 22, 2012 6:55 AM by Alin Vargatu

    Question frequency value

    Ropanzer Ropanzer

      Hello!

       

       

      I have a question, if I do a simulation of the frequency and the frequency shift is set to 8 Hz, Displacement of the first result is the value of 383.7 Hz, and the value at the last Displacement result is 6380 Hz. Is not to much the difference from 8Hz to 6380Hz or 6380 must be divided by 1000?

       

       

      Thank you anticipate!

        • Re: Question frequency value
          Alin Vargatu

          As far as I know, in frequency analysis, the displacement plots of vibration modes are scaled using a factor which is generated internally by the solver. This factor is determined by the actual system of equations to be solved by the solver. In any case, the user doesn't have access to this number.

           

          The displacement plots in frequency analysis have to be understood as relative. Meaning that if on a plot a node has a displacement value of 100m and another one has a displacement of 200m, then all you can conclude is that in the considered mode, the second node will have a magnitude of displacement twice as large as the first node.

           

          On the same principle, one should never compare displacement results of frequency analysis from different studies, nor from different mode shapes.

           

          That being said, SolidWorks Simulation Premium would allow you to run a response spectrum analysis. In such a study the results of a modal analysis are used in terms of a known spectrum to calculate displacements and stresses in the model. For each mode, a response is read from a design spectrum based on the modal frequency and a given damping ratio. All modal responses are then combined to provide an estimate of the total response of the structure.

           

          You can use a response spectrum analysis rather than a time history analysis to estimate the response of structures to random or time-dependent loading environments such as earthquakes, wind loads, ocean wave loads, jet engine thrust or rocket motor vibrations.