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General Mechanical

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Question about units of frequency response

    • Shian Li
      Subscriber

      I am currently measuring the frequency response of some points. I found that the unit of the Y axis in ansys is mm, but the unit I actually want is mm/N. I want to know what further processing I need to do for this unit ? Thanks

    • peteroznewman
      Subscriber

      What kind of support was used?

      Was the displacement result relative to a Base Excitation or was it an absolute displacement?

      What kind of excitation was used to cause harmonic vibration in the structure?

    • Shian Li
      Subscriber

       

      I applied a 0-700Hz force to one end of the shaft, which has equal components in all three directions. The axis is in a static state, only the displacement along the axis is limited to 0, and the frequency response of the points on the axis perpendicular to the axis is measured. 

      I got a piece of experimental data from Siemens Simcenter. The experimental conditions are the same as the simulation. Some sensors will record the displacement of points on the axis, and some sensors will record the magnitude of the external force. The unit of the obtained frequency response is mm/N. So my question is whether the frequency response results of the displacement obtained in the ansys simulation can be considered as consistent with the experimental results. Or do I need to perform additional calculations, such as: displacement/external force=mm/N (if this is the case, should it be the resultant force of the external force or a component force in a certain direction?), or I need to measure the stress at the same point and Calculate 1/(displacement*stress)=1/[mm*(N/mm^2)]=mm/N.

       

    • peteroznewman
      Subscriber

      The Displacement Frequency Response will change with the Force magnitude.  Apply a force of 1 N in the X direction and measure the Displacement Frequency Response in the X direction. That will correspond to the Siemens Simcenter output for the X direction. If you increase the force magnitude to 10 N in Ansys, the displacement will be 10 times larger.

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