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Re: About the moment calculation in cohesion-friction model


Hello Bruno,

Thank you for your so warm help. According to your reply, I think I can understand this law totally. Thank you again.
I think you said is reasonable. But, now I am confused at which law is suitable for my model, instead I haven't confused at the law itself. I just want to simulate the almost perfect elastic-plastic material. Compared to CohesiveFrictionalPM, wether this law is better? The different moment threshold criteria should play the varied effect. However, how much effect on the model? Maybe the one law is suitable to the one kind of material, and the other laws are suitable to the others. If you have no idea, I will try. According to the deformed shape and the stress-strain curve, the suitable law will be chosen. If you have any comment, please don't hesitate to let me know. Thank you.
if necessary, I will make the change in source, then I will discuss it in here. Thank you. :)


At 2010-09-18 01:29:03,"Bruno Chareyre" <bruno.chareyre@xxxxxxxxxxx> wrote:
Hello Liqing,

You are right on the fact that there is no plastic limit for moment in current law. The calculation of moment itself however (say, elastic rotation-moment law) should be the same as in Plassiard et al., only the threshold is missing.
Moment will not exactly act all the time, it will act as long as shear or tensile strength are not exceeded, then the contact is broken and there is no moment anymore.
It would be nice to implement the plastic limit on moment. Feel free to do that (maybe usingCohesiveFrictionalPM as an exemple, or maybe you will use this one straight away?) and ping us for integrating the change in the sources.
Making the default threshold "infinite" will not change the default behaviour and cannot hurt anybody.



On 16/09/10 12:40, 焦利青 wrote:Hello,

I found the moment calculation in cohesion-friction model is different from the traditional algorithm which is listed in the paper(Jean-Patrick Plassiard etl, A spherical discrete element model:calibration procedure and incremental response, 209; N. Belheine etl, Numerial simulation of drained triaxial test using 3d discrete element modeling; Rolling resistance at contacts in simulation of shear band development by DEM). In the traditional algorithms, the slider for rolling starts working if the moment exceeds a value of "eta* Normal force". However, I cannot find the related code described it. If no any condition to relax the moment. then the moment will act all the time.  I think it should be wrong. Maybe I haven't found the right file. May I have your help? Thank you.


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Bruno Chareyre
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ENSE³ - Grenoble INP
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