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Using cohesive elements in Abaqus
I have used Traction Sepration law for modelling a crack by using pore pressure cohesive elements-I have observed both damage initiation and damage evolution law and I checked by QUADSCRT output that my damage initiation criteria has been satisfied I also have used PFOPEN output(Pore fracture opening at integration outputs) observed that my fracture opening increased from 2 mm to around 8 mm during a 2o min step time that means that crack initiates and propogates but I dont see any crack forming in my model when I see the model in Abaqus Viewer -Does anybody have experience what's wrong with the model ?Is crack really happens? why pfopen shows that the pore fracture changes but I dont see any crack forming in my model output. I have copied and the paste the inp lines:
*COHESIVE SECTION,ELSET=cohesive,MATERIAL=cohesive,RESPONSE=TRACTION SEPARATION,
THICKNESS=SPECIFIED, CONTROLS=VISCO_upper
0.002
*SECTION CONTROLS,NAME=VISCO_upper,VISCOSITY=0.01
*MATERIAL, NAME=cohesive
*ELASTIC,TYPE=TRACTION
50E9,50E9,50E9
*DAMAGE INITIATION,CRITERION=QUADS
1e5,1e5, 1e5
*DAMAGE EVOLUTION,TYPE=ENERGY, SOFTENING=LINEAR, MIXED MODE BEHAVIOR=BK,POWER=2.284
117,117,117
*GAP FLOW
1.e-3
*FLUID LEAKOFF
5.879E-11,5.879E-11
I can also share the full inp file if somebody can help.
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Comments
SECTION CONTROLS
If I well understood your problem, I think you have to use the command
element deletion=YES
in the section controls.
I also have used the
I also have used the element deletion=YES ,but I did not see any change!!
Check the variable SDEG
I think the element deletion=yes by default. The QUADSCRT variable tells you if the initiation criteria is satisfied or not. If the variable is 1.0 in an element then the initiation criteria is satisfied. The variable SDEG tells you the state of damage in an element. Even if the initiation criteria is satisfied the element might not be completely damaged. From my understanding you can say that a crack has propagated if an element is completely damaged i.e SDEG=1.0. You can use the probe tool to get accurate values of SDEG in an element.
probe tool
Thanks for your help- I can see the SDEG have a profile from 0 to 1 for different elements.By the way where can I find this probe tool?
Cohesive elemet propeties
Hi Diana W.Smith
I am working on crack propagation problem using cohesive elements but I really do not know how to choose the properties of cohesive element. As you post part on inp. file in blog that apears the properties of cohesive elements. Can you tell me how to choose it??
Vikas
The query tool
You can get the query tool from the tools, then query, then choose probe values. you can get the SDEG data that you want.
I am still working on this part. If you do not mind, can I have a look at your input file, maybe it is the better way to know where ie your problem. wwang19@lsu.edu
SDEG updating?
I am using cohesive elements coupled with USDFLD subroutine. I have a damage variable in my subroutine, which according to the calculations is updating in a correct way. But my problem is that SDEG is not updating, hence the elements are not being deleted. I have called the STATUS variable and that is also not updating. Can anybody provide some help?