About servo process of triaxialStressController engine

Asked by littleFish

Dear all,
When I want to use triaxialstresscontroller to implement a triaxial test with wall boundaries, I cannot find some controll parameters like relStressTol or absStressTol for periStressController engine to controll the servo process to keep a constant confining pressure during shearing. And indeed I find some relatively large fluctuation of the confining pressure when the axial strain is more than 20% or 30%(the confining pressure fluctuates between 100kPa and 110kPa when I set the confining pressure to 100kPa). I wonder if there is some way to control the confining pressure to a smaller range during a triaxial test for this engine.
Thanks.
Zhijie

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Bruno Chareyre (bruno-chareyre) said :
#1

Hi, when there is no tolerance it is usually because the tolerance is zero.
And in this case indeed the servo-control will do its best unless the difference is exactly zero.
Large fluctuations can have different origins (I would blindly blame strain rate as a first guess), please provide a MWE for more answer.
Bruno

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