sharp penetration of a soft solid (contact & stress singularity)
sharp penetration of a soft solid (contact & stress singularity)
(OP)
Hi all,
I am trying to model a sharp knife penetrating skin. I have some ideas about how to do this but I would invite any comments from all you experts on my method at this early stage.
I am using explicit. The knife is modelled as rigid body and is driven via boundary conditions. The skin is modelled as a hyperelastic material.
1. What is the best type of interaction to use? currently I am using general contact explicit and it seems to work ok. but perhaps surface-to-surface contact would be better? The abaqus example of a projectile penetrating a plate uses surface-to-surface contact but I found general contact solves quicker and appears to do the job better too.
2. I do not intend to model the actual damage. What I plan to do is to use a failure criterion (such as Von mises) along with element deletion. I am using the submodelling technique to get a higher mesh density in the region of interest, without sacrificing efficiency. Currently the geometry of the blade tip is modelled as a point (no tip radius). Will this lead to stress singularity and if so, will that matter since I am using element deletion anyway? The alternative is to introduce a small tip radius (around 1micron), but in this case I will need a very fine mesh about the blade tip to capture this geometry. And since it's a rigid body anyway, it seems like a waste of time and effort!
Please feel free to comment on any aspects of this, I would love to hear the opinion of the community.
Thanks,
Aisling
I am trying to model a sharp knife penetrating skin. I have some ideas about how to do this but I would invite any comments from all you experts on my method at this early stage.
I am using explicit. The knife is modelled as rigid body and is driven via boundary conditions. The skin is modelled as a hyperelastic material.
1. What is the best type of interaction to use? currently I am using general contact explicit and it seems to work ok. but perhaps surface-to-surface contact would be better? The abaqus example of a projectile penetrating a plate uses surface-to-surface contact but I found general contact solves quicker and appears to do the job better too.
2. I do not intend to model the actual damage. What I plan to do is to use a failure criterion (such as Von mises) along with element deletion. I am using the submodelling technique to get a higher mesh density in the region of interest, without sacrificing efficiency. Currently the geometry of the blade tip is modelled as a point (no tip radius). Will this lead to stress singularity and if so, will that matter since I am using element deletion anyway? The alternative is to introduce a small tip radius (around 1micron), but in this case I will need a very fine mesh about the blade tip to capture this geometry. And since it's a rigid body anyway, it seems like a waste of time and effort!
Please feel free to comment on any aspects of this, I would love to hear the opinion of the community.
Thanks,
Aisling





RE: sharp penetration of a soft solid (contact & stress singularity)
Rob Stupplebeen
https://sites.google.com/site/robertkstupplebeen/
RE: sharp penetration of a soft solid (contact & stress singularity)
I understood that I would be simpler to implement element deletion instead of crack prop. What would be the benefit of using the crack propagation approach?
I am starting off with quasi-static speeds but I want to increase the rate of displacement of the blade up to 10m/s. Also I was under the impression that explicit can model contact better.
RE: sharp penetration of a soft solid (contact & stress singularity)
RE: sharp penetration of a soft solid (contact & stress singularity)
Using a crack propagation approach would help with the mesh dependence problem e.g. (XFEM) but would require use of the implicit solver (which can also be used to solve 'dynamic' problems to some degree)and may not be so straightforward to implement in your case.
For contact I think the explicit solver is better for your application (at least for the Abaqus version you are using which doesn't handle edge to surface contact well in Standard, its improved in later versions). I'd say stick with the general contact approach unless you have specific reasons to work with contact pairs, which I don't think you should for you application.
RE: sharp penetration of a soft solid (contact & stress singularity)
My next challenge is to get the element deletion working effectively. Can I still that using the general contact approach?
RE: sharp penetration of a soft solid (contact & stress singularity)