Coupling object movements - Jacking type movement

[Austin hoyle]

Hello all,

I’m having a tough time trying to find a solution for my problem. I’m hoping to model a jacking component of a larger system. I can simplify the system into two parts

1. A larger cylindrical shaft, which needs to be modeled with no defined motions, just fixing displacement in all directions except for the z direction, and allowing gravity and the mass of the object dictate its path downward
2. A smaller tip of the device which moves back and forth relative to the larger shaft. The motion of oscillation is in the direction the shaft movement (the z direction).

What I am looking to model is how the whole system can penetrate soil when only the weight of the system is applying a downward force, and the tip is oscillation back and forth relative to the shaft, acting as a jack hammer type device.

My original thought was to create a datum CSYS and assign its origin to a reference point created on the larger shaft, and then assign that coordinate system to the oscillation boundary condition to the tip. But when I run the simulation, the larger shaft moves according to how I defined it, but the smaller tip oscillates back and forth in the same location in the world frame. Indicating to me maybe the coordinate system defined on the larger shaft's reference point is not actually tied to the objects position, but rather "borrowed" the coordinate positions of the RP when I selected it.

Anyone have any recommendations? I attached a video of the results of a simplified model I set up to show what I mean. My intention is that the smaller object would move with larger object, but still oscillate back and forth at the brim of the larger object. Also, in this simplified model, I do not induce movement through gravity, but rather simply define a velocity BC on the larger shaft.

 

[FEA way]

You should try using connector elements. Connector actuation/motion will let you achieve this oscillation.

 

[Austin hoyle]

You should try using connector elements. Connector actuation/motion will let you achieve this oscillation.

Thanks for the response! I’ve implemented a translator connector between the two objects. I think this is close but not sure how to get it to the finish line. The motion of the smaller tip needs to be defined relative to the larger object.

It’s almost as if I want the center of the rim of the shaft to be the tip’s origin in a coordinate system. Then define an oscillating positive and negative velocity of the tip relative to that point so its motion is consistent. Then regardless of what motions are applied to the larger shaft, the tip will always oscillate this local frame origin.

Right now using a translator connector with defined stops, I define an oscillation velocity on the tip, and I apply a pressure to the back end of the larger shaft. The result is the two actions fight each other. Instead what I envision is the system as a whole is propelled by the pressure, and the tip continues to oscillate over the same origin described before.

Honestly not even sure if I’m describing my goal clearly. It’s a bit tricky to even formulate in my head.

 

[FEA way]

Isn’t connector motion (e.g. connector displacement boundary condition) with a proper amplitude for time variation sufficient to achieve the desired oscillatory movement in your case ?