Sorry, Bruno, I was a little too fast on the reverts... > If it causes trouble, just tell me and I'll see how to fix it. It was > not supposed to change anything for you (especially if you work in small > strains, you should not see any difference). So why do you need to > revert this? > > This is not geomechanics, just "correct" mechanics. It makes things > consistent. > - Take real a steel bar and make a tensile test on it. Plot force vs. > dL/L, it is not linear (even if it looks linear for small strains). Plot > force vs. log((L+dL)/L) , it is always linear (provided you didn't enter > plasticity ofc). The same happen in DEM simulations. > - volume change : with your definition ev!=(e11+e22+e33), with Log, they > are always equal. > - apply a strain rate of -10e-2/sec for 50 seconds. Result with your > strain 0.393 (not equal to strainRate*time!), result with log : -0.5.
OK, it makes sense with velocity gradient, probably. (In small strains, the 1e-2/sec rate is against the reference size, so it would work, I think..) > - with log, there is no upper limit to strain (except the grain > size/period size condition), you can compress 100, 200, 300%. With your > definition, e=100% has no meaning. e=-100% ;-) > - most users won't notice any difference if they are in small strain, > you don't need to adapt anything or "think" about it. When "your" strain > is 0.01, log(1.01)/1 gives 0.0995 (log is just slightly more > accurate). And if you don't remove the exponential, target will be > reached exactly. That's true, ok. > I'm not removing refSize at all, and I agree on the clear meaning of it > (size is different, see #1). > Did it change something for you? I see now... You removed refSize at few places, but didn't change the formulas in commentary, so I wan't really sure what you did and didn't patiently try to understand it first. It it actually quite clear now: instead of Δl=(σ₁-σ)l₀(A/K) you compute Δl/l₀=(σ₁-σ)(A/K). In that case, cellGrow should not be called cellGrow but something like cellRelGrow. > The current (reverted) code is doing approximately this : > > maxGrow = dt*maxRate*refSize;(in meters) > Grow = targetStrain*refSize;(in meters) > compare(Grow,maxGrow); > velGrad = Grow/refSize; > > Does it make sense to multiply THEN divide by refSize?! > I suggested this, simpler and generalised more easily : > > maxGrow = dt*maxRate;(in [-]) > Grow = targetStrain*refSize;( in [-]) > compare(Grow,maxGrow); > velGrad = Grow/dt; > > would have been even better : > > Grow = targetStrain*refSize;( in [-]) > velGrad = Grow/dt; > compare(velGrad,maxRate); I get your point, sorry again. For reverting my reverts, I think it is easier to so it by hand; it is about 4 lines for refSize and 4 for log strain... Try bzr diff -r1935..1936 (or qdiff instead of diff, if you have the great qbzr package installed) or bzr qdiff -r1935..1936 pkg/dem/Engine/GlobalEngine/PeriIsoCompressor.cpp to get just that file. > #1. I'm currently working with the polar decomposition of F to define > proper stretches and rotations. It is the only way to define a "size" > without rotational artifacts for e.g. simple-shear (note that simple > shear is the most interesting non-axis-aligned loading, pure shear makes > no sense since it is just a classical triaxial test performed on rotated > box). > > It almost work, and it allows shearing the cell forever without reaching > the "2*halfsize>size" limit. It simplifies many parts in the code > (collider using period of lengths refSize instead of getSize...). Should > I commit this to trunk without copy/paste? You will not revert it the > day after? :) I am quite sure the collider doesn't like that. How does it work? Currently Cell::_size is (to my knowledge) computed without rotation artifacts, I checked that with rotating the cell completely around and it didn't deviate a bit from the original size. > I'm, looking forward for Anton's guidelines in order to set kdevelop > indent mode. There should be a way to commit this setting in > trunk/yade.kdevelop. I am afraid he will write different things than how I write code and I will have to quit yade development ;-) v _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
