When I use the XFEM method in Abaqus to predict fracture of my materials, Abaqus gives good results about crack initiate and maximum load, but it can't predict crack grows. In Abaqus, after maximum load, unstable fracture happened but in experimental tests stable fracture continues. I have attached my result in a photo that shows experimental and numerical results.
Hi dear Asgar,
There are two different sources for this mismatch;
1) You have to change your cohesive criterion in the "Property" modulus.
I am sure that you have choose the "Linear" for your "Softening" behavior!
Maybe it's better to use "Exponential" or "Tabular" for "Softening" behavior of your material (In the Damage Evolution part).
2) The second reason might be the non linearity of your material that you have to turn "NLGEOM" on in the "Step" modulus.
I hope that your problem will be solved!
Best of Luck ;)
my crack is grows but that grows is fast i use MAXPS stress at failer of final stress of tensile test .and i define damage evelotion with fracture energy = my calculated fracture toughness.
Have you checked whether your fracture criterion is appropriate to your problem?
Well somewhere within the XFEM formulation you are using will be a fracture criterion, which should be described in the documentation. You need to check if this criterion corresponds to the physics of your problem.
For example, you say you calculate a fracture toughness. How do you calculate the fracture toughness? Is the value you find maybe only applicable to the transition from stable to unstable growth, and should you be using a lower value for stable crack propagation?
yes i obtain it only for stable crack propogate
how can i use it for all dominate? more explain
Check your element size, because the crack initiation and crack position varies with element size...Hence, choose appropriate element size by comparing obtained results with other related works. Once you fixed element size properly, the crack will propagate continuously, because crack propagation is a material parameter. However, there is some mesh dependency in XFEM, it will affect your result slightly.
Dear Asgar,
The fundamental step during the implementation of the XFEM is the definition of the nodes to be enriched, by keeping in mind the crack and mesh geometries. I think you need to look in to the paper authored by E. Giner et al, Engineering Fracture Mechanics 76 (2009) 347–368. The paper focused on the implementation aspects for two-dimensional Linear Elastic Fracture Mechanics applications containing single or multiple cracks.
Hi dear Asgar,
There are two different sources for this mismatch;
1) You have to change your cohesive criterion in the "Property" modulus.
I am sure that you have choose the "Linear" for your "Softening" behavior!
Maybe it's better to use "Exponential" or "Tabular" for "Softening" behavior of your material (In the Damage Evolution part).
2) The second reason might be the non linearity of your material that you have to turn "NLGEOM" on in the "Step" modulus.
I hope that your problem will be solved!
Best of Luck ;)
Salam
Don't forget to define PHILSM & PSILSM in field output request. Moreover, you must select "allow crack growth" in:
Interaction module/special/crack
These two hints may solve your problem.
Good luck
A.A
hi
this videos can help
1/ https://www.youtube.com/watch?v=hleGKlOAeK0
2/ https://youtu.be/eEtVxAhExJA
Hi, can anyone help me with this. Instead of using Direct Cycle step definition, can I use Static step definition for fatigue crack propagation? is it possible to define fracture criterion type=fatigue in static step?
I tried using static step, with maximum principal stress to initiate the crack. And define the fatigue fracture criterion including c1,c2,c3,c4,r1,r2 etc for fatigue crack growth. The crack is initiated, but it doesn't grow. can anyone explain me why and how to solve this problem.
Thank you very much.
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