Yade

constitutive law for inelastic (elasto-pastic) contacts

Asked by Alexander Eulitz [Eugen]

Hi there,
is somebody dealing with inelastic contacts using Yade?
I found pkg/dem/NormalInelasticityLaw.cpp which is quite good. But it makes use of the Cundall & Strack formulation whereas I need HertzMindlin.

Some infos about the problem I try to solve:
A steel ball is dropped from a given height onto a horizontal plate which is made of steel, too.
I simulated this scenario using Cundall and Strack and observed way higher contact forces than in my experiments.
I.e. about 30N (experiment) to 250N (C&S simulation) for maximum force of the first contact.
Changing to contact law of Hertz Mindlin which seems appropriate because Cundall & Stracks law was originally tested on disks rather then spheres, gives simulated maximum contact forces of 40N.
A indentation test on the steel ball and the steel plate showed that there is a slight difference in the hardness of the two materials. So the softer one (the plate) can be plastically deformed by the harder steel ball. I think that this could explain the deviation of contact forces. That's the reason I am looking for a Hertz Mindlin based constitutive law for elasto-plastic contacts.

Thanks for your help,
Alex

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Alexander Eulitz [Eugen]
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Chiara Modenese (chiara-modenese) said : 		#1

Hi Alex,

For inelastic collisions based on the Hertz-Mindlin model I suggest you
look into this paper:
http://www.sciencedirect.com/science/article/pii/S0032591012005670
 An investigation of the comparative behaviour of alternative contact force
models during inelastic collisions
Once you have identified the model that you think is most appropriate
to model your case then you can try to implement in Yade - contact models
are relatively easy to implement and test in Yade.

Best,
Chiara

On 19 October 2013 10:56, Alexander Eulitz [Eugen] <
<email address hidden>> wrote:

> New question #237624 on Yade:
> https://answers.launchpad.net/yade/+question/237624
>
> Hi there,
> is somebody dealing with inelastic contacts using Yade?
> I found pkg/dem/NormalInelasticityLaw.cpp which is quite good. But it
> makes use of the Cundall & Strack formulation whereas I need HertzMindlin.
>
> Some infos about the problem I try to solve:
> A steel ball is dropped from a given height onto a horizontal plate which
> is made of steel, too.
> I simulated this scenario using Cundall and Strack and observed way higher
> contact forces than in my experiments.
> I.e. about 30N (experiment) to 250N (C&S simulation) for maximum force of
> the first contact.
> Changing to contact law of Hertz Mindlin which seems appropriate because
> Cundall & Stracks law was originally tested on disks rather then spheres,
> gives simulated maximum contact forces of 40N.
> A indentation test on the steel ball and the steel plate showed that there
> is a slight difference in the hardness of the two materials. So the softer
> one (the plate) can be plastically deformed by the harder steel ball. I
> think that this could explain the deviation of contact forces. That's the
> reason I am looking for a Hertz Mindlin based constitutive law for
> elasto-plastic contacts.
>
> Thanks for your help,
> Alex
>
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Revision history for this message
Alexander Eulitz [Eugen] (kubeu) said : 		#2

Hi Chiara,
thank you a lot for the link.
I'll have a look at it.