yade-dev team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 18 May 2010 16:55, Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx> wrote:

>
>  2) Why do we need to continue if fn==0?
>>>
>>>
>> IIRC Bruno told me that was to avoid contacts that transmit no force,
>> even if they have non-zero nominal stiffness. Exact zero will be there
>> for interactions that really had no force at all.
>>
>> I am not completely persuaded on that, since most likely contacts with
>> exactly zero force will be already erased. Perhaps now it has only
>> historical interest now?
>>
>>
>>
> Interactions without contact (un<0 && fn==0) are not always erased. Think
> capillary law : you can have a capillary force (an interaction) between
> distant spheres, in this case the normal force is 0 (the capillary force is
> not added to fn), and there is really no stiffness to consider in GSTS, even
> if this interaction has kn!=0 and is real.
>

In fact, this will be a problem for me. Capillary law is one specific case
and has been computed, if I get it right, as a separate constitutive
relationship. However, there are laws where fn can be zero and a stiffness
has to be consider since the contact still remains as the contact area is
finite. Could we find a way to make this line specific to capillary law
then? I do not need it "exactly" now but soon.

Chiara

>
> Bruno
>
>
>
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