Hi,
I'm trying to model crack propagation using ANSYS software in my thesis.
I've got a question concerning crack tip mesh. I'm modeling eliptic surface crack in a plate using CTMOPT macro and KSCON commant but I face some issues.
First of all CTMOPT is ok but I don't have any control on cube sourronding crack so in fact I can't propagate my crack really deep. The cube like sructure lines and areas intersect with base plate areas. What is more i have no clue how to use this macro to create through crack but with crack tip nodes laying on spline.
This problem is solved when I do mesh manually.
I sweept mesch along eliptic line (or any other line) from 2D mesh but I can't guess how to increase number of layers above 2. So KSCON gives me two rows of mapped elements in radial direction but I'd like to have at least 4.
I saw codes using elements generated on nodes, but it's not comfortable solution as I don't know how to create area from elements.
Please give me a tip how to increase number of layers in radial direction.
Hi Saimonah,
ANSYS Workbench (version 14.5 and later) offers an automated tool to introduce semi-elliptical crack profiles. It actually introduces the semi-elliptical crack and defines the mesh properties around the crack tip in a structured manner. By adjusting the ellipse size based on a crack propagation Law (e.g. Paris) and a correlation of the SIF with respect to da/dN, you can simulate the crack propagation until you reach to the formation of a through thickness crack. At this point you should change your approach and use the "pre-meshed crack profile" option. Then continue in the same manner until you reach the limit of the analysis (brittle fracture). Instructions on how to use the Workbench "crack" tool can be easily found online.
Hope that helps.
Regards,
George
Thanks george,
i have seen workbench capabilities. If I want to model through crack or corner crack in a plate (3D), i cant use that automatic tool. pre meshed crack can be used only when i have crack and mesh. Can you please tell me how to create crack and crack mesh in case of corner crack or through crack in ansys workbench?? (i want to insert crack in already existing model)
Hi Saimonah,
In this case you have to introduce the crack as part of the geometry beforehand. Lately I have done this by introducing the desired through thickness crack profile as a separate geometrical feature and by positioning appropriately and subtracting this feature from the original geometry of the plate in Design modeler. Other CAD software can be equally used. Then you follow the "pre-meshed crack" approach.
Regards,
George
Thanks again,
In design modeler, i am unable to create crack surfaces of through crack in the middle of plate. I didnt understand the part that you said about creation of through crack. If possible, can you please share the wbpj file of plate with through crack in it (to see how it can be done). Then. I can do analysis with premeshed crack.
regards,
Saimohan
Hi Saimonah,
I am not allowed to share the file because of industrial confidentiality reasons. I will try to explain the steps I followed. In DM you create a very thin plate with an "elliptic" profile but sharp edges, width equal to the total length of the crack you want to model and very small thickness. The other dimensions of the plate can be arbitrary. Then you position this plate to intersect your original thick plate/component. By a "Boolean" operation you remove the volume of intersection between the two plates in DM and you end up with a new geometry that contains a gap (your crack). Then mesh it and continue using the pre-meshed crack approach.
Regards,
George
Thanks George,
I am doing like that only. It is leaving gap in the crack position to represent the crack. that gap should not be present to get accurate values of j,k. i want two crack faces at the crack location with out any gap. So that, when i mesh it, nodes should be different on two faces in crack location, then crack can open during deformation. How to do that without any gap to represent crack. If possible, just create one plate with crack in it in workbench, and send wbpj file to my mail address. If you wish to send it to me i will give my mail address.
Thanks
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