Maziar,
You have raised some good points. Let me start off by saying that I had some limited experience with PREP7 and I remember that it had very extensive selection tools, which were not dependent on geometry.
1. Many times I have made the mesh in Hypermesh and imported it into CAE. Then I finish rest of modelling (loads, bcs etc.) inside CAE, because I find it easier. However I agree with you , once a mesh is imported into CAE (or an orphan mesh is created), not many changes can be made in the mesh inside CAE. The only change that I remember is you can change a linear mesh to quadratic or visa versa.
2. CAE does have a tool called 'selection by angle', which would let one pick the nodes/elements on a surface/face (you can define a small enough angle that only the nodes on the surface are picked). You can also pick nodes by window which is a laborious method of picking nodes. However I imagine the selections in PREP7 are better. The idea in CAE is that one decides about the node sets required in advance before the orphan mesh is created. Then one would create suitable partitions in geometry before meshing the part. Once the partitions are created, meshing process takes into account the partitioning surfaces and makes sure that no elements cross the partition boundary. For meshing purposes partition is almost like a separate part, except that the nodes on the boundary are connected to nodes on both sides of the boundary.
3. For picking nodes surfaces in CAE please refer to my comments in point 2. I can not answer your question about python scripting as I do not have any experience in python scripting. I am going for a scripting class next week and I may be able to answer your question after that.
4. In a modeler based on CAE geometry there is no need to identify a node based on co-ordinates. Nodes are identified based on geometric features (vertex, center of a line, distance from a vertex etc.). This is also the paradigm for modern CAD systems and makes picking a lot easier and faster.
I guess I understand your earlier statements better now. I need to restate my position slightly. If one wants to work with only FEA mesh for subsequent modelling (applying lods, bcs, picking node sets etc.) using the the geometry only for creating the mesh, PREP7 may work out to be better. However if one wants to use geometry for not only meshing but also for subsequent modelling (loads, bcs , node sets etc.) CAE is faster and better. For new users CAE is a lot easie to learn than PREP7. Workbench is not an alternative to CAE. Workbench is only a shadow of CAE.
Gurmeet S. Cheema
Ohio USA
Maziar Mahzari <***@yahoo.com> wrote:
Let me ask you some questions,
1-How do you make an orphan mesh (from another mesh generator? or another CAE session? That's not a good idea if you want to have all your model with MODEL and HISTORY data in a single script text file. That's a luxuray you have while you work with ANSYS/APDL, even parametrically)
2-Let say you have an orphan mesh in CAE. How do your define node sets based on some geometry rules (e.g. located on a flat surface, or using different arbitrary coordinate system) or attached to a Face (orphan meshes don't know about the geometry objects) in the python script?
3-How do you define a surface (which is the most important concept in ABAQUS) based on the node sets, element sets, location or a Face of the model in an orphan mesh inside a python script?
4-Assume you want to load a node of the model based on its location (x,y,z), how do you find its number and put it in your python script (ANSYS/APDL has a function node(x,y,z) which gets the node number)?
Note that I use a script to generate the model and frequently import it just to check. No feedback from CAE/GUI, just python programming.
M. Mahzari
----- Original Message ----
From: Gurmeet Cheema
To: ***@yahoogroups.com
Sent: Sunday, 14 January, 2007 9:25:19 PM
Subject: Re: [ABAQUS] Re: Number of nodes/elements in assembly?
Maziar Mahzari wrote;"Regarding to your comments on geometry concept, you should know that ANSYS/prep7/ solution/ post1/post26 ... (not talking about workbench) has control on both geometry (keypoint, line, area and volume) and finite element model (nodes and elements) where /CAE Python does not give you control on FE model. Having control on entities (geometric or FE) based on their number, location etc. is definitely stronger than .findAt() function in /CAE.Still depending on the problem (and the accessibility) you have to choose between them."
ABAQUS/CAE gives one the option of working with the geometry or mesh alone. If one wants to work with mesh only (elements or nodes only) one can create orphan mesh parts. These are parts that are without any geometry. Therefore above statement about ABAQUS/CAE is not correct.
Gurmeet S. Cheema
Maziar Mahzari wrote:
As an old fashioned person I don't like beautiful and fancy graphical interfaces. I prefer to interact through a text file and just check the model in the graphical interface. I wonder if you have taken advantage of APDL (programming language of ANSYS) but it is very powerful. I always enjoy mixing the power of programming with FE analysis. Ive developed some macros which have saved me lots of time and in some cases I just changed some parameters and reused the macro.
I tried to do the same tricks with Python in /CAE but at this stage its not that powerful. Although I think /CAE has a firm foundation for development and its concepts are properly devised, but still not comparable to APDL.
Regarding to your comments on geometry concept, you should know that ANSYS/prep7/ solution/ post1/post26 ... (not talking about workbench) has control on both geometry (keypoint, line, area and volume) and finite element model (nodes and elements) where /CAE Python does not give you control on FE model. Having control on entities (geometric or FE) based on their number, location etc. is definitely stronger than .findAt() function in /CAE.
Still depending on the problem (and the accessibility) you have to choose between them.
M. Mahzari
----- Original Message ----
From: Gurmeet Cheema
To: ***@yahoogroups. com
Sent: Saturday, 13 January, 2007 9:00:39 PM
Subject: Re: [ABAQUS] Re: Number of nodes/elements in assembly?
Jarry wrote:,"The question is, what is more important for us? Perfect geometry
handling, modern interface and better geometry core of abaqus,
or robust mesher, extensive element library and fast solvers
of ansys? It depends "
I used to work with ANSYS (mostly using the workbench interface) before I switched to ABAQUS. At the time I did a comparison of two softwares and also talked to some users. I did not come across any user who said ANSYS is a better software than ABAQUS. I did find some who went the other way.
I do not believe one can make a statement that ANSYS solvers are faster. I think ABAQUS has a more extensive element library. I stand behind my earlier statements on ABAQUS/CAE vs. Workbench. Work bench can access only limited numbers of features of ANSYS. On the other hand ABAQUS/CAE can access lot more features of ABAQUS.
In terms of usefulness of using geomtry for FEA model building, it is a matter of choice and experience. For those who have already invested 10 years of their life learning intricate features of the software, it is probably better to continue the old way. However for new enterants into the field, using geometry to apply loads, boundary conditions etc. is so much faster. Also if you change the mesh, you can still preserve these loads and boundary conditions.
I have not heard of the software called PREP7. Is this software still marketed by ANSYS?
In general having worked with both ANSYS and ABAQUS, I am happier in my experience with ABAQUS. I spent some trying to learn the so called classical interface of ANSYS and found it to be mess. Also ANSYS practice of having their distributors do the tech. support did not work for me. I found the distributors were a lot more busier doing consulting work and did not have sufficient time to support the product.
Gurmeet S. Cheema
Post by Gurmeet CheemaI have used both the ANSYS Workbench and ABAQUS CAE. Both work with the
geometry. But comparing the two is like comparing apples and oranges.
Workbench was designed to be a linear tool. And later changes have come
as an after thought. ABAQUS CAE was originally designed to be the front
end for full ABAQUS power. Therefore ABAQUS CAE is much much more
powerful than Workbench. I think it is very unlikely that Workbench will
catch up in the near future.
Workbench is something like next-gen "cad-like" pre-processor
for Ansys, but apart from that, there is still old good Prep7.
And frankly, abaqus/cae can not be compared to Prep7 concerning
meshing capabilities (I could name a lot of meshing-features
abaqus/cae can not handle, but why? those who worked with both
of them know it)...
On the other side, in geometry processing/importin g and modelling
abaqus/cae is much-much better than old-fashioned bottom-up
"point-line- area-volume" prep7.
The question is, what is more important for us? Perfect geometry
handling, modern interface and better geometry core of abaqus,
or robust mesher, extensive element library and fast solvers
of ansys? It depends...
BTW, Workbench is neither linear, nor nonlinear tool. It is
simply new pre/post-processor (something like abaqus/cae).
Behind it, there is still ansys/solver.
Jarry
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