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[Mehdi Pouragha <question675377@xxxxxxxxxxxxxxxxxxxxx>]

Question #675377 on Yade changed:
https://answers.launchpad.net/yade/+question/675377

Mehdi Pouragha posted a new comment:
The objective was to 1) apply constant normal and shear strain rates,
and 2) measure the strains-- both within small strain ranges.

As you mentioned, the first one conveniently is done through
maxStrainRate.

The second point, measurement of strain, can be done for normal strains
through triax.strain, as you indicated.  The difficulty  was with shear
terms. For the shear strains, my rookie mistake was to think that;
regardless of the current value of cell.trsf, if the applied "increment"
of the  strain is small, we can still measure the shear strain by
finding the change in cell.getSmallStrain(). This appears not to be
true. But I can imagine it might be a plausible mistake to make.

Yes, we can say there is no need to consider small strain increments at
all, and all the ambiguities are resolved if we use finite strain
calculation. But still, in many cases, people like me are interested in
small strains and may resort to convenient small strain calculations and
functions, without noticing the pitfalls. All I was suggesting is that
it would be helpful to mention that  functions such as
cell.getSmallStrain() will contain non-negligible errors, even for small
increments of strain, if the cell.trsf is far from identity.

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