10 December 2019
- Last edited 10 December 2019
Rmaur29, Parker correctly said "so the displacement that is displayed it not a real value" yet you have said "but the problem is that to reduce the displacement...". If the displacement you are talking about is from the Modal analysis, you have not understood Parker's point.
The displacements in a Modal analysis are arbitrarily scaled and have no relation to measured displacements in a real experiment because there are no loads in a Modal analysis. One way to simulate real displacements is to add a Harmonic Response analysis to the Solution cell of the Modal analysis. In the Harmonic Response, you can insert a load. For example, a force that represents a periodic force from an unbalanced mass on a spinning shaft will induce some vibration into the machine, depending on the shaft speed. The amplitude of the machine vibration will depend on the magnitude and frequency of the unbalanced force and the modal frequencies in the structure.
If you want more specific suggestions on how to revise your model to reduce the first natural frequency, reply with images inserted into your post of the structure. The more detail you provide, the better will be the suggestions. Show how the machine is connected to ground. If you used a Fixed Support, that may be too stiff compared with the real machine. You could replace a Fixed Support with a Pinned joint to ground to add some flexibility to the model, lowering the first natural frequency. Parker may have other suggestions.