Dear All,
I am working on micro mechanical modeling of metals (X65 grade steel). I just have some questions that I am wondering if anyone can help me by answering them.
1. How can I find the the parameters in traction-separation: Knn, Kss, Ktt ( should I consider module of shear and elasticity for them?)
- In damage initiation: normal, shear 1, shear 2
- In damage evolution: fracture energy. mix-mode ratio 1 and 2
2. I know that for cohesive element , it is important to have the match meshes in boundaries of the surfaces but my question is that is it also important to have match meshes in boundaries when we define surface base cohesive?
I'm looking forward to hearing from you soon.
Thank you,
Hi.. in my opinion:
1) you have to simulate an experiment, for example a fracture toughness one. You set parameters by comparing Fem and experimental COD vs Force curves... depending on the TSL you are using, you should set an initial guess. Mixed mode ratio depends on what you are simulating.... for a simple KIC test you should consider only mode I.
2) matching is always recommended.
You can find some help here :
Technical Report Computational fracture mechanics
Hi rasoul,
About your first question, we have recently published a paper which shows how to determine microscopic parameters of cohesive cracks based on macroscopic properties in brittle materials. you can find it in my researchgate home page. The stiffness of cohesive crack is not the same as material macroscopic stiffness. knn, kss, ktt relate the tractions to the separation which means that their dimension is N/m3 while the bulk stiffness dimension is N/m2. As an estimate you can simply divide the bulk stiffness by the thickness of cohesive interface.
hi ahmad
thanks for your response
do you mean this article?
'' microcracks relationship with engineering properties ''
how can I access that?
Following with great interest.... Thank you so much for sharing this article. Regards, Emad
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