Friction to rolling ball

[roolf]

Good evening,

I have some problem with using msc Adams. I am trying to add friction between sphere rolling on box, but the problem is when I add friction in contact it doesn't work us I expected. It doesn't stop the ball after initial velocity is supplied. It is just decreasing initial velocity. However when I am using friction for a joint it works way better. But the problem is I don't want to make any joints because it removes degrees of freedom of my sphere. Is it possible to left the ball with 6 degrees of freedom and add friction between sphere and box? Thank you very much in advance for help.

 

[GregLocock]

If your sphere and box are rigid friction alone won't slow it down if it is rolling. Think about it.

Cheers

Greg Locock


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[roolf]

Well I am trying but I can't understand it. If friction force is the only Force applied to the body it should stop, shouldn't it? Lets say I want to measure the travelled distance of the ball which has 10m/s initial velocity and friction coefficient 0.05. I know it is task for primary school but I want it in Adams without decreasing degrees of freedom of the ball to let it rotate and translate freely on the surface. The friction of joint works properly (it stops after some time)but like I said I want the movement in any direction on the surface. I will be grateful for any help. Thank you in advance.

 

[GregLocock]

"If friction force is the only Force applied to the body it should stop, shouldn't it?"

Yes. But in your case, once the ball is rolling properly, ie v = r*omega, there is no frictional force. No slip, hence no friction.

Think about it some more, draw a free body diagram or two.

This is, frankly, high school mechanics.







Cheers

Greg Locock


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[roolf]

Okay, now it is clearer for me. I've made test and cube does stop and ball like you said is just slower because of friction when there is no slip. But in real life rolling resistance stops the ball after some distance and this the clue how can I achieve it in ADAMS? I've looked for rolling resistance function in GCN but I didn't find. Can you help? Thanks

 

[GregLocock]

Well, yes, if I had more time I probably could, but I don't actually have the time at the moment, as I'd need to research it. My tire models already account for rolling resistance via a user sub, and I've never examined how that detail works. You could contact MSC at

https://simcompanion.mscsoftware.com/infocenter/index?page=home

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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