## General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

#### Forced vibrations

• Evgenii_K
Subscriber

Hello everyone! Again I solve the test problem, but this time for forced fluctuations. There is a single-span beam on which the engine is fixed as a load, the engine has a mass and a shaft rotation speed.

• HesamK
Subscriber
Hi. what do you exactly want? you'd like to calculate unbalance force due to rotation of the beam? or due to a harmonic force that assert on the beam as a result of engine vibration?
• Evgenii_K
Subscriber
HesamK, Hello.
I want to test various tasks including harmonic response and vibration, starting small. In this task, I want to determine the amplitude of forced oscillations.
• HesamK
Subscriber
Hi, for this purspose you must implement harmonic response module, not modal. in modal you get mode shapes not amplitudes. to know how to perform harmonic analysis, please watch examples on YouTube, if there are any question after that, I can help you.
• Evgenii_K
Subscriber
HesamK, thanks, but your help is not needed. The question still remains open.
• Evgenii_K
Subscriber
Found the CMOMEGA command - can this command be used for angular velocity?
• peteroznewman
Subscriber
You want to simulate the force generated by an eccentric mass m that rotates with an angular velocity omega. The eccentricity is e.
Force F = e m omega^2 If there is no eccentricity, there is no force.
If you have a Harmonic Response analysis system, you can insert a Rotating Force load and that allows you to insert the mass and the eccentricity directly.
Then you can compute the response over a range of omega values. 400 RPM = 6.66 Hz.
You could plot the response from 1 Hz to 60 Hz. The eccentricity is called Rotating Radius in the Details window.
• Evgenii_K
Subscriber