Hi
I am trying to simulate scratching of DP steel by a rigid indenter:
1- Due to excessive distortion i need to use adaptive meshing. I have used ALE method but it seems that due to having general contact on the sheet surface, nodes on the sheet surface are not adaptive. I think that might be the reason why ALE doesn't improve mesh quality at all. Do you have any idea how can i prevent mesh distortion during severe scratching?
2- I need to consider damage in the model. I am using ductile damage but i don;t have reliable generic damage data for steel for negative stress traxiality values. Also does any body know which damage model best describes this scenario; shear damage or ductile damage? And how can i get some damage data for steel?
Thanks
Good morning
Probably the strait foreword approach is to use a FEA program, like Ansys, Comsol or Abaqus.
To a more precise simulation, BEM or even DBEM, should deliver a more detailed and accurate answer.
Dear Akbar Mostanni,
If you are using LS-DYNA, try the SPH solver instead of the ALE one. The SPH solver permits infinite deformation, and mimic damage naturally. Regards, Ji.
You can use continuum damage model (Lemaitre 1992).
For generic data, try defauts material constants (see MAT_DAMAGE_3 in LS-DYNA user's manual).
Regards
Thanks Ji Ryong Cho. I am using Abaqus which has SPH functionality. I am not familiar with that but it seems that SPH is not accurate in simulating contact. Also how can i mimic continuum damage models with SPH? Do you have any idea?
I have been working on this problem for a while and here is what i have found:
I searched for damage model data in literature and it seems that there are limited data available. I selected aluminium alloy 2024-T351 as case study and simulated scratch test with a rigid conical indenter with apex angel of 120 degree. I have incorporated ductile damage model in this simulation. Defining proper contact between indenter and sheet is the first challenge. When surface elements fail, they are deleted from the calculations and therefore no contact is detected. By defining an element based surface as the contact domain that includes internal surface of elements, once an element is deleted the internal surface become active in the contact domain (See Figure 1). This feature which is called element erosion (available in general contact algorithm) allows contact between newly born surfaces with the indenter as well as contact between themselves i.e. debris can interact with sheet surface and indenter (see Figure 2). However this type of contact has one big limitation, it does not support ALE, meaning surfaces involved in general contact are non-adaptive and ALE adaptive meshing can not be used to enhance mesh quality.
Figure 1, Figure 36.4.1-2 of Abaqus analysis user’s guide showing element erosion
To overcome the excessive mesh distortion adaptive meshing is usually recommended. In Explicit the only available method is ALE adaptive meshing technique which is compatible only with contact pair algorithm (in contract to general contact algorithm). Contact pair algorithm can not consider element erosion using an element based surface. To simulate contact between new surface born after deletion of surface elements, node based surface can be used as slave surface. It means those nodes that are likely to engage in contact during simulation should be used to define a node based surface which will be used in contact definition. Good thing about this method is that it supports ALE adaptive meshing so better mesh quality can be achieved to avoid poor quality elements seen in Figure 2 and Figure 3. Bad thing, though, is that interaction between debris and sheet can not be simulated. Therefore debris after being removed from the sheet surface penetrate into the sheet without any resistance as seen in Figure 3.
So the question is that how can I avoid mesh distortion and penetration of debris into sheet surface while contact between newly generated surfaces are always active
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