How to calculate the Amplitude of the vibrating Motor?

Member Posts: 21

I want to apply harmonic load (i.e. vibrating of motor) in harmonic response analysis.

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• Posts: 12,000Member

If you have a rotor of mass m and the center of mass is a distance e from the axis of rotation and the rotor is turning with an angular velocity Omega, the amplitude of the rotating force is F = m*e*Omega^2

Machines with high speed rotors are usually balanced to get e = 0 or something very close to zero.

https://www.irdproducts.com/unbalance---cause-of-vibration.html#dynamic_unbalance

• Posts: 12,000Member

Every force applied in a Harmonic analysis is the amplitude of a harmonic force.

• Posts: 51Member

How to calculate the value/Amplitude of the harmonic force ( i.e. in my case Vibration of the mounted motor) ?

• Posts: 1Member

Dear Peter,

First my sincere appreciations to your contribution here at the forum.

I am pretty much new to simulations and have been lately working with harmonic analysis to simulate stress and deformation responses of a dewatering screen excited with a set of vibro motors. I am attaching a zip file containing the image of the screen and the forces applied, in a zip file.

We have performed the below steps.

1. Four springs have been added with corresponding stiffness as body to ground connections.
2. Modal analysis performed and modal shaped noted.
3. Centrifugal force provided by the manufacturer is applied at a specific frequency with directions shown in the images with the same force applied twice with a phase angle of 90 degrees. We are unsure about how we model this force or how we force excite the screen.
4. We then resorted to a simple model of a single shaft loaded with a rotating force with unbalance mass to understand the application of force. But was stopped with two issues of remote point and bearing radial stiffness. We just gave the dynamic load capacity of the bearings in the stiffness assuming deflection of 1mm. None of the manufacturers seem to have it. Then we made the coordinates of the remote point same as the coordinates of the rotating force and solved the model. But unsure if the results are correct.

1. How to excite the screen ? Some literature have used point mass to excite the same. But unclear of the process.
2. A vibromotor mounted on a flat surface as shown will transmit centrifugal force in all directions, but we went with the crowd by applying the force with a phase angle of 90 degrees.
3. Is there a chance of applying rotating force by directly entering the force value ? If yes, then where should the remote point be created. What is the real purpose of the remote point.

Thanks.