Re: Strain compution in Triaxialstresscontroller

```Ah... I should have read Luc's post before sending my own reply...

Thanks.

Bruno

Luc Sibille a écrit :
> Hi,
>
>   There is several definitions of strain, see for instance the page
> about strain computation in Wikipedia:
>
> http://en.wikipedia.org/wiki/Deformation_(mechanics)
>
>
> If I'am right (but please verify to be sure):
>
> ** Log means ln (natural logarithm),
>
> ** The way to compute strains in Yade is valid for large strains (or
> large transformations), whereas the definition
> epsilon=(length-length0)/length0 is valid under the hypothesis of small
> strains.
>
> ** compare the results given by ln(length/length0) and
> (length-length0)/length0, it is quasi the same for strains lower than
> 20% to 30%, when strains become too much important
> (length-length0)/length0 is no longer valid.
>
>   Best
>
>   Luc
>
>
>
> 张林 a écrit :
>
>> Hi everyone
>> These days I'm a little puzzled with the strain compution in
>> TriaxialstressController.cpp ,just as follows:
>>
>> strain[0] = Mathr::Log(width0/width);//Eq(1)
>> strain[1] = Mathr::Log(height0/height);//Eq(2)
>> strain[2] = Mathr::Log(depth0/depth);//Eq(3)
>> volumetricStrain=strain[0]+strain[1]+strain[2];//Eq(4)
>>
>> IIRC,Log means not log10 but ln as usual .Is it right?
>> Eq(1 to 3) is different from the common compution of strain like:
>> epsilon=(length-length0)/length0
>> and, in PFC3D manuals(V3.0)->users' guide->problem solving with pfc3d
>> Page 47, I found another Eq for strain compution:
>> epsilon=(L-L0)/((L0+L)/2)
>> Are the 3 methods all right? They're designed for different fields?
>>
>> Thanks for any suggestion.
>> Regards.
>> Zhang Lin
>> 　　　　　　　　xtss_0002@xxxxxxxxxxxx
>> 　　　　　　　　　　2008-11-25
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>>
>
>

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