1 Topic by ChrisB

(1 replies, posted in General Help)

hi Borek-

Is there a way to relate the mode 1 fracture energy to the parameters of the nonlocal isotropic damage model?  It seems like it might be related to the ductility parameter, but I don't see any documentation on this. 

thanks,

Chris

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2 Reply by ChrisB

(3 replies, posted in General Help)

Thank you very much Borek, that clarifies things a lot.

I have a follow-up question regarding the Loadlevel record.  Upon the first unloading step, the Loadlevel changes to 1.0 and stays the same upon the second unloading step.  The nodal reactions reduce in step to (near) zero, as expected.  Why does the Loadlevel change to 1.0?  Is it related to using direct displacement control?  I find that the load level remains 1.0 for all load steps if I use direct control for both the loading and unloading steps, and I don't understand why.

thanks,

Chris

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3 Reply by ChrisB

(3 replies, posted in General Help)

Here's a test file indicating what I'm attempting.  I'm trying to modify the test010 file to load for several steps (in just the x direction) and then unload completely.  Upon the first unloading step, the load level drops to 1, the displacement unloads by 1 step, but then the system remains the same in the subsequent step.  Can you let me know where I'm going wrong?

loadUnloadTest.out
attempted modification of test010.in
# 
# rectangular specimen
#
# 4------------------3
# |                  |
# 1------------------2
#
# time 0 - loaded in x direction under indirect controll, controlled displacements of nodes 2,3 
# time 1 - unloaded in x direction under direct displacement controll
# result - the return to original unloaded state
#
NonLinearStatic nsteps 2 nmsteps 2 
nsteps 2 controllmode 0 stepLength 2.5 rtolv 0.0001 MaxIter 2000 Psi 0. reqIterations 80 HPC 2 2 1 refloadmode 0 
nsteps 2 controllmode 1 rtolv 0.0001 MaxIter 2000 stiffmode 1 ddm 4 2 1 3 1 ddv 2 -2.5 -2.5 ddltf 3 refloadmode 0
domain 2dPlaneStress
OutputManager tstep_all dofman_all element_all
ndofman 4 nelem 1 ncrosssect  1 nmat 1 nbc 2 nic 0 nltf 3
Node 1 coords 3  0.0   0.0   0.0  bc 2 1 1
Node 2 coords 3  4.0   0.0   0.0  bc 2 0 1 load 1 2
Node 3 coords 3  4.0   3.0   0.0  bc 2 0 0 load 1 2
Node 4 coords 3  0.0   3.0   0.0  bc 2 1 0
PlaneStress2d 1 nodes 4 1 2 3 4  mat 1 NIP 4 crossSect 1
SimpleCS 1 thick 0.15 width 10.0
IsoLE 1  tAlpha 0.000012  d 1.0  E 15.0  n 0.25  
BoundaryCondition  1 loadTimeFunction 1 prescribedvalue 0.0 
NodalLoad 2 loadTimeFunction 2 Components 2 2.0 0.0
#NodalLoad 3 loadTimeFunction 4 Components 2 0.0 1.0
#NodalLoad 4 loadTimeFunction 5 Components 2 0.0 -1.0
ConstantFunction 1 f(t) 1.0
PeakFunction 2 t 0.0 f(t) 1.0
PeakFunction 3 t 1.0 f(t) -1.0
#
#
#%BEGIN_CHECK% tolerance 2.e-6
## check load level
#LOADLEVEL tstep 1
## check reactions 
#REACTION tStep 1 number 1 dof 1 value 0.0
#REACTION tStep 1 number 4 dof 1 value 0.0
## check dof 1 for nodes 2 and 3
#NODE tStep 1 number 2 dof 1 unknown d value 0.0
#NODE tStep 1 number 3 dof 1 unknown d value 0.0
##
#%END_CHECK%

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4 Topic by ChrisB

(3 replies, posted in General Help)

Hi Borek,

I'm interested in unloading to the origin following the onset of tensile damage.  I see the examples test010 and test011, which load and unload in single load steps.  However, I am applying many load steps before the onset of damage (around 20), in which case I can't seem to figure out how to remove the applied displacement to return back to the origin.  Does it matter if I use direct or indirect displacement control, should I define separate loading and unloading metasteps or use a load time function that changes sign?

thanks,

Chris

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5 Reply by ChrisB

(2 replies, posted in General Help)

Thanks Borek!  That's clear now.

Chris

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6 Reply by ChrisB

(6 replies, posted in Developers Discussion)

Hi Borek,

I'm also interested in the use of interface elements.  Could you provide an example of the use of interface1d and interface2dquad elements, or send me the report you mentioned in the previous post about modeling of brick walls?

Thanks!

Chris

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7 Topic by ChrisB

(2 replies, posted in General Help)

Hi Borek,

If I want a gravitational force to act in the negative y-direction, does that mean that the acceleration component in the DeadWeight declaration should be positive (as in other codes) or negative?  I'm a little confused given the DeadWeight class definition that says the acceleration components are expected to be downwards vertical.

Can you clarify the sign convention for me?  In searching through other posts I've seen what looks like gravitational loading values specified both positive and negative.

Thanks in advance.

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