General Mechanical

Add force until a displacement is achieved.

• rdk9000
Subscriber

Hello I would like to add a force to the bottom right corner of the model in the y direction. I would like the force to stop once the horizontal displacement of the top of the cylinder reaches a threshold in the -x direction.

• peteroznewman
Subscriber

There may be other ways to achieve what you want. Here is how I would achieve your goal.

Analysis Settings

Auto Time Stepping, On

Initial Substeps 10

Minimum Substeps 10

Large Deflection, On

In the Solution Branch, insert a directional deformation plot using the horizontal coordinate direction and scope it to the top of the cylinder.

After you solve, you will have tabular data for Time, Applied Force and Horizontal Deformation.  Pick the value of force when the horizontal deformation reaches the threshold.

This assumes that the applied force is large enough.  If the horizontal deformation didn't reach the threshold, make it larger. If you want more resolution in the tabular output, use more substeps.

• rdk9000
Subscriber

Great I will try this!

• rdk9000
Subscriber

I gave it a shot but hitting the deflection at the correct threshold proves to be very time consuming. I have samples of various geometry I have to try this with. I would ideally like to design this in APDL entirely.  Is there a way to incorporate APDL commands to say when the x displacement reaches 50 microns deactivate force?

• peteroznewman
Subscriber

In Workbench, you can add a Direct Optimization component to the Static Structural analysis and let the optimizer adjust the force until the displacement is exactly 50 microns.

I hope an expert in APDL can answer the question for how to use APDL code to do the same.

How linear is the force-deflection data?  If it is basically linear, then just apply the same force to all designs and use the deformation of the top as the response. Even better, divide the force by the deformation to put the response in terms of stiffness K in N/micron.

• rdk9000
Subscriber

Hello Sir,

So I changed the model a bit to more accurately reflect my device. The moment on the right side will eventually cause the two pillars to touch. This is what I'm looking for. However I have not had much luck with enforcing contact (thus why I'm trying to use displacement). I have read a bit about parameterizing but cannot find a solid source. Ideally I would like to optimize the gap between the pillars for a given strain. But for now I would just like to increase the moment until contact is made (or the difference of displacement in the X is 0). I'm not exactly sure how to add a direct optimization component as you mentioned above. Thank you again for your time.

• peteroznewman
Subscriber