yade-dev team mailing list archive

[François <francois.kneib@xxxxxxxxx>]

Hi Anton,

I checked the Pournin's implementation you made, and I may have found a
little error. According to the formula (10) in the paper, the four formulas
(22) are the resulting stiffness/viscosity_coefs of a contact, and you
rightly transcript them. But in your algorithm, you set
kn1 = kn2 = *formula_in_(22)*
and then :
*kn = contactParameterCalculation(kn1,kn2)  *which is the same as :*
kn = **contactParameterCalculation(kn1,kn1)
= (kn1) / 2*
Which finally gives :
*kn = *
*formula_in_(22) / 2*
Do you agree with this ?

François


2014-04-03 15:11 GMT+02:00 François <francois.kneib@xxxxxxxxx>:

> Hi,
>
> One last thing : in the 3rd case (young modulus
> case
> ), it would be useful to determine
> cn from E1,E2,massR and en. I know the formula for normal cn, but not for
> cs. Do you have an idea ?
>
> Thanks,
>
> François.
>
>
> 2014-04-03 10:15 GMT+02:00 François <francois.kneib@xxxxxxxxx>:
>
> 2014-04-03 10:00 GMT+02:00 Anton Gladky <gladky.anton@xxxxxxxxx>:
>>
>> 2014-04-03 9:51 GMT+02:00 François <francois.kneib@xxxxxxxxx>:
>>> > It will for sure break my scripts, as I used massMultiply=0. But your
>>> > implementation is part of my "todo list", which I can remove now :-)
>>> > You have made huge changes at once, so I need a little bit of time to
>>> check
>>> > everything. What I can see now is that you use "isnormal(r)" function
>>> into
>>> > the Ip2, which returns false if r==0. It will be a problem, for
>>> example if
>>> > we want to set cn, but cs=0 (same matter for en and et).
>>>
>>> I just wanted to check, that it is not(isnan). Thank for notice,  will
>>> change to
>>> not(isnan).
>>>
>> Yes that's what I supposed.
>>
>>
>>>
>>> I think you can  just remove massmultiply from your scripts and it
>>> should work
>>> fine.
>>>
>> I will re-check everything and see whether I am consistent with the
>> current implementation. You can delete the "massmultiply" argument in the
>> "contactParameterCalculation" function, as it's not used any more.
>>
>>> Anton
>>>
>>
>> François
>>
>>
>