Modal Analysis - FEA

grabcad

This is an example of Modal Analysis applied on a part by using FEA module in Autodesk Inventor 2014. The Modal Analysis is useful when we want to find out what are the resonant frequencies of a rigid body when a certain vibration occurs. For instance, if you disconnect an electric motor (being in rotation) from the power source and you wait till it stops by keeping your hand on the motor stator, you will feel how the motor get some maximum vibrations during this process. Any of the peaks appears when a certain resonant frequency of the assembly of motor is reached. They are more evident when the rotating part is more unequilibrated. Here, the rigid part is the „Part 034.ipt” from my Album of 100 parts (see: Parts 031...040 - The CAD Album of 100 CAD Parts). Attached you have its model and drawing (IPT, IDW and PDF format). Looking to Video below, you can see the deformation of part on its 5th resonant frequency (2065.09 Hz). Attached is the file „Avis.zip” which contains 8 clips corresponding to the first 8 resonant frequencies of the rigid part. The 5th one is that in the Video section below. If you work with Inventor 2014, 2015... and want to reproduce for yourself the whole situation, you have to apply the four steps procedure illustrated in the attached four pictures. Before this you have to create a directory in which you will download all the files attached to this project (named „Temp” here). Step 1: Make default the attached „Part 034.ipj” project and open the „Part 034.ipt” Step 2: Activate the tab „Environment” and select the „Stress Analysis” tool Step 3: Activate the „Simulate” tool and click on „Run” Step 4: Select the „F5” Modal frequency in the browser and then activate the „Animate” tool from the panel „Result” and click on the „Play” button; now you will see the part deforming like in the Video section. If you work with Inventor and want to apply the same procedure to another part (like that ones in my mentioned Album of 100 parts), you have to apply a simple procedure, as follows. Look to the picture „Separate Modal Analysis.jpg”. Open your different part, then activate the tab „Environment” and select the „Stress Analysis” as before. Now you must have the screen presented in the picture. Activate the tool „Create Simulation” and choose the option „Modal Analysis”, accepting that 8 Modes by default. Activate the „Assign” tool in „Material” panel and select the material („Steel”, or „Steel, Carbon” for example). Activate the „Fixed” tool in „Constraints” panel and select the fixed face of the part (cylindrical interior face for the Part 034) Activate the „Simulate” like in the Step 3 from above, and continue with Step 4. If you do not use Inventor, you have to apply similar procedure - if your CAD software includes a FEA module. Enjoy!