New question #291781 on Yade:
https://answers.launchpad.net/yade/+question/291781
Dear all,
Thank you for noticing my question. I'm a new Yade user and I'm trying a
triaxial test with it. But I encounter some problems in the testing process.
When I test the particles which young modulus are MPa, the result of the test
is regular. But when I change the young modulus to GPa, there are some troubles.
I conduct the test using triaxial tutorial script-session1.py and modify
it a little:
1) After generating the particles, I add 10KPa to the three directions
to make the particles touch.
2)When the particles have touched each other, they are compacted by
decreasing the friction angle gradually with 10KPa confining pressure. After
this procedure, a sample with specific porosity is got.
3) Adding the required confining pressure 0.8MPa till the unbalanced
force<0.01.
4) Loading the deviatoric stress by controlling the axial strain, its
rate is -0.02.
When I change the particles' young modulus to GPa, there are some
problems:
1)When the confining pressure 10KPa is added, the particles in the
packing decrease. Maybe the packing has exploded?
2) I increase the stress from 0.5KPa to 10KPa gradually, decrease the
time step as:
timestepSafetyCoefficient=0.1(before, it is 0.8)
triax.goal1=triax.goal2=triax.goal3=-500
while 1:
O.run(3000, True)
unb=unbalancedForce()
print 'unbalanced force:',unb,' mean stress:
',triax.meanStress
if unb<stabilityThreshold and
abs(-500-triax.meanStress)/500<0.1:
break
....... .......
triax.goal1=triax.goal2=triax.goal3=-10000
while 1:
O.run(3000, True)
unb=unbalancedForce()
print 'unbalanced force:',unb,' mean stress:
',triax.meanStress
if unb<stabilityThreshold and
abs(-10000-triax.meanStress)/10000<0.1:
break
The specimen is compacted and the particles doesn't disappear. It is defective
that the unbalanced force can't <0.01, increasing the damping is no use. I
increase the max unbalanced force to 0.03, the script can just continue. But
when I load the deviatoric stress by controlling strain rate=-0.02, the axial
stress is decreasing gradually from 0.8MPa even to 0.4MPa.(The confining
pressure is 0.8MPa.) And when deviatoric loading, I can see the obviously
moving of the particles.
Thanks again!
Sincerely Geo
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