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Shock Compression and Rebound Damping

gpommeranz
6-Contributor

Shock Compression and Rebound Damping

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?  

 

 

 

1 ACCEPTED SOLUTION

Accepted Solutions

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.

VR_9713318_3-1688118912570.png

VR_9713318_2-1688118876801.png

 

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

VR_9713318_0-1688118647357.png

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

VR_9713318_1-1688118770357.png

 

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

 

View solution in original post

7 REPLIES 7

2023-06-02_mdo.png

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

 

gpommeranz
6-Contributor
(To:skunks)

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

 

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)

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
6-Contributor
(To:VR_9713318)

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

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.

VR_9713318_3-1688118912570.png

VR_9713318_2-1688118876801.png

 

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

VR_9713318_0-1688118647357.png

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

VR_9713318_1-1688118770357.png

 

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

 

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.

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