spinning off centre mass

[mstols]

I want to simulate a shaft with an off centre weight attached to it. It spins at a certain rpm. How would I apply this loading condition in mechanica, and what type of analysis should I run

 

[jabbadeus]

This is one of those open-ended questions that are hard (almost impossible) to answer without knowing more.


The first question is, what results are you looking for? If you're looking for reaction forces, that's more of Mechanism Dynamics. If you're looking for stresses, then it's Mechanica... but my guess is, you would run it in Mechanism Dynamics to generate loads, and import the loads into Mechanica as a load case.


And depending on what you are studying, you may have to physically model the mass and it's connection to the shaft, as opposed to using a mass element.


So what are you looking to study?

 

[mstols]

I want to run the analysis as described above. It needs to be mechanica run(Im guessing some sort of dynamic run) as we are looking at the stresses in the shaft as the motor is running for X amount of time.

So in the end, I want to do a fatigue analysis as well.

The problem that I see with this, is the fact that the load direction is changing as the mass is rotating. It is easy to change the direction of a load on its own axis. That can be done with a simple sin function. But this load changes direction from one axis to another axis. The image shows what the design looks like.

View attachment 2678

 

[jabbadeus]

Connect a mass element ata pointto the structure via a beam element. Define a gravity vector in the appropriate direction. Use a centrifugal load to define the angular velocity of the shaft.