Learning Forum

[abhi.mrt22]

Dear all,

here I attach my geometry pic... there is a pistion cylinder arrangement... cylinder is of mild steel and piston is of nylon... friction cofficient between them is 0.4... piston is constrained to move in longitudenal direction without rotation.. in this i want to find how much vibrations are induced at the red mark due to frictional sliding of piston in cylinder... in a nutshell how i model this to find friction induced instabilities.... as i know this is due to stick slip phenomenon... but unable to model this in ansys... modal and harmonic analysis is linear in nature and not consider this non linearity... how i convert this non linearity to linearity for modal and harmonic analysis... plz help...

 

 

 

 

[peteroznewman]

Do you have a physical sample of this mechanism?  If so you could instrument it to measure the vibration at the red mark or the piston.

What is the significance of the red mark? Why does it matter if there is some vibration at that location?

Why is the red mark at the end of a short offset beam?  That short beam seems like it could amplify the vibrations of the piston. Can the beam cross-section be larger?

What causes the piston to move, fluid pressure? What is the fluid? How is the fluid pressure controlled?

If the stick-slip motion is a problem, why not use an actuator that has no stick-slip behavior such as a bellows arrangement.

What are the requirements for the motion of the red mark? Does the actuator have to use a fluid at all, could it be a done with an electro-mechanical actuator?

[abhi.mrt22]

actually this is only for an example.. my actual motive is to know.. how friction induced vibration is modeled and analysed in ansys.. 

[peteroznewman]

You would use Transient Structural to model friction induced vibration.

My reply was intended to teach the idea that when a problem is identified with a specific technical solution, it is often better to step back and look at other solutions that don't have that problem, rather than to lean into the problem and figure out how to model it.