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[Aníbal Sánchez Numa <question670047@xxxxxxxxxxxxxxxxxxxxx>]

Question #670047 on Yade changed:
https://answers.launchpad.net/yade/+question/670047

Aníbal Sánchez Numa posted a new comment:
Hello again, Jan:

I modified the script to save the plot data into a file. I thought I
should calculate the first derivative of the curve which seems to be in
corresponding to the concept of Young modulus but the data don't allow
me that since the first points extracted have 0 stress... I show here
the first part of the file.

-2.48824398585e-17;0.0
-1.78952486733e-06;0.0
-3.57904973463e-06;0.0
-5.36857460193e-06;0.0
-7.15809946924e-06;0.0
-8.94762433654e-06;-186659.792761
-1.07371492038e-05;-186659.792761
-1.25266740711e-05;-186659.792761
-1.43161989384e-05;-186659.792761
-1.61057238057e-05;-186659.792761
-1.78952486731e-05;-398472.332577
-1.96847735404e-05;-398472.332577
-2.14742984077e-05;-398472.332577
-2.3263823275e-05;-398472.332577
-2.50533481423e-05;-398472.332577
-2.68428730096e-05;-586864.566007
-2.86323978769e-05;-586864.566007
-3.04219227442e-05;-586864.566007
-3.22114476115e-05;-586864.566007
-3.40009724788e-05;-586864.566007
-3.57904973461e-05;-784964.591216
-3.75800222134e-05;-784964.591216
-3.93695470807e-05;-784964.591216
-4.1159071948e-05;-784964.591216

Actually, the strain turns out to be negative (could this be correct?)
although I thought may be it has to be with the sense of the axe..
Anyway, I was told to use the first derivative of a point formulas for a
set of points but which points should I use if I use the first two then
I get a 0 stress, I could use some in the middle but which ones are the
correct??? You told me to calculate the "initial slope" but what does it
mean exactly in this case???

Thanks in advance

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