Shock Compression and Rebound Damping

[gpommeranz]

I'm attempting a study of a Macpherson strut and struggling to figure out how to input the damping characteristics.  I have the Creo Mechanism dynamics option but as far as I can tell the damping coefficient would be the same in both compression and rebound.  I'm wondering if there is a better way to represent the damper.  Anyone have experience with this?  

[skunks]

... little info about it, unfortunately in german ...

[gpommeranz]

Any chance you have a link so I could Google translate?

[skunks]

Friction damping in MDO
Main problem: The velocity proportional damper introduces
a high shock force because of the high shock velocity!
Idea for solution: Friction damping, since it is practically only slightly
speed-dependent (ideally not at all!), delivers relatively low
damping forces at high speed (during the shock), but
relatively high at lower speed and this always!
Ideal friction damper
with FR=50 N
Real friction damper
with FR "50 N in the
interesting
speed range
(as a force motor in MDO)

Translated with www.DeepL.com/Translator (free version)

[VR_9713318]

This is a good example.

The main point for your application is using the Domain to give two different damping coefficients for compression (negative forces?) and traction (positive forces).

[gpommeranz]

That part makes sense.  I'm struggling with applying the force motor as a function of something other than time.  

[VR_9713318 · Accepted solution]

Hello.

Of course. I had this struggle too. Mr. @SweetPeasHub, helped me in another thread.

Check it out: Solved: Change velocity of servo motor according to force ... - PTC Community

You will need to create the measure of your interest. Trying to remember something about my time of Baja SAE, I would say that you will need create a Measure of Velocity of you Damper.

Then, while creating the Force Motor, use this measure as Primary Variable.

Now you will be able to use the Velocity as Domain of your motor.

I'm not 100% sure about this path, but this is the logic. I believe you will be able to solve your problem.

[SweetPeasHub]

Here is a reference that seems authoritative.

https://www.diva-portal.org/smash/get/diva2:1547559/FULLTEXT01.pdf

You can put in a custom Force vs Velocity function in Creo if the built-in linear-vs-velocity damper is insufficient. I think the level of details depend on whether you are designing/improving the strut. You might also be able to contact the strut manufacturer for engineering details on strut performance and modeling.