FEA in Unigraphics NX7.5 - doubt regarding solver type 1

[Rhyder88]

Hello all

I am familiar in doing FEA in I-deas SDRC. Now need to do FEA in NX 7.5 and i started with an overview.
Here i have some doubts to clarify .. I am starting with few questions. Let me ask some other questions along the thread.

1.When i try to create a new FE model , (.fem file) , the software provoked to choose the type of solver.
I chose solver type as Ideas unv and i am able to proceed with meshing and i cannot proceed further , like giving loads,creating BC sets, solution sets etc.
All the icons corresponding to load sets are disabled when i go in this direction.

Now i tried again with new FE model with NX nastran as solver type and now i am able to proceed till the last step, creating solution set and
solve the set.

My doubt is , whether we can solve the FE model of I-deas unv type in NX7.5 or we can solve only FE model of NX nastran type.

 

[missil3]

.fem is only for meshing . To give loads, bc sets and solutions sets you have to create a .sim file. File >> new simulation >> choose the right file .

If you did do this I think you might not have checked out the right license.

 

[Rhyder88]

missil.. yes i created sim file.. when i created sim file with nastran as solver , the load ,bc icons are enabled but when i tried i-deas unv as solver type, those icons still remained disabled

 

[missil3]

Check if you have checked out the right license. You can do this by going to nx license tool from start menu. Check if you have the right license bundles.

 

[Helrezer]

THe issue is that Ideas Universal file has no solver associated with it.

In NX, the GUI is built around the solver choosen. So NX Nastran (or MSC Nastran) is a solver, and ANSYS or ABAQUS has associated solvers. A universal file doesn't have an associated solver.

Siemens is developing only the NX Nastran solver now, and Model Solution will ride with Ideas into the sunset.

When moving from Ideas to NX, Siemens recommends that the nastran bulk data file be used to move data. This does lose the assoitivity with the geometry.

I hope this explains why you could not create boundary conditions in the SIM file.

Good luck with NX.

Marilyn Tomlin
Siemens PLM Software

 

[Rhyder88]

Thanks Tomlin. you really clarified me..

Now , as i am moving from I-deas to NX , so.. Model solution to NX nastran obviously, i am in search of main differences between these two solvers.

1.It will be very easy to grasp about the new Solver.

I made a simple simulation (cantiliver beam static and mode shape analysis) in Nastran as a beginner exerceise. But i think i need to know more about the solver to carry on with some advanced simulation like frequency response simulation.

2.And i am having another doubt that why there are these many solvers.. Nastran, Abacus,LS dyna, Model Solution ,ansys ..bla bla bla..
What are the variations they provide..Do they all provide same outputs? Do they differ in their algorithms?

 

[Helrezer]

There are a lot of solvers, less then there used to be.

Each solver has a speciality. Nastran is the strongest in dynamics.

If you have used Model Solution and you use NX as your pre/post, you will find that there are some differences but most will be transparent to you, with the exception of the nonlinear capability. NX Nastran has a large strain nonlinear solver in Sol601 and an explicit solver with Sol701. So that will be additional capability that was not in Model Solution.

The algorithms for solving may vary slightly between solvers. The more common difference is in the element formulation. For instance, Model Solution's shell element has 6 DOF, while the shell element in NX Nastran has only 5 DOF. Also, solvers vary in the way boundary conditions are applied to the elements. For instance, NX Nastran creates contact as a boundary condition, and uses the Modified Lagrangian method. Some other solvers use the Lagrangian method and/or penalty functions, but create the contact as contact elements.

I hope this helps. Please let me know if I can provide you more information.

Marilyn Tomlin
Siemens PLM Software

 

[Rhyder88]

Tomlin.. The information is really valuable.. Thanks a lot

While i am going through various options in meshing as well as solution sets , i noticed a small thing.

1..All the element names start with a letter C . Instances are CQUAD4,CTRIA3,CBAR.

Does this C indicates anything?

2..The solution types end with a code like 101,102 etc.. Instances are
SESTATIC101-SINGLE CONSTRAINT
SESTATIC101-MULTICONSTRAINT
SEMODES103 etc..

Does this codes wish to say anything to me ?

3..Most of the option names seems to follow cryptonym. (code forms) . But in model solution , i used to found simple words like thin shell parabolic element, Linear static analysis etc..

Is Cryptonym - A salient feature of NASTRAN NX??

 

[Helrezer]

Dear Rhyder

The C in front of all elements stands for Connectivity. Nastran names elements C+shape. And Model solution was easier in terms of understanding the element types. This language is left over from the early Nastran days.

The Solution ### is the solution sequence that is called. This is again Nastran speak, when the solution file is written you will see SOL 101 in the case control. There is a list of the solution sequence numbers in the front of the nastran manual. The single constraint or multiconstraint refers to the location of constraints. When the constraints are changed, the stiffness matrix must be recreated and solved. So for a single constraint, the constrants (restraints) are written above the subcase (load case) level. For the multiconstraint option, the constraints are written at the subcase (load case) level. This causes the solver to create and invert the stiffness matrix.

The SE means Superelement, then Static is linear statics, and Modes is modal analysis, so there is some information you can gain from the names.

The cryptonym is very much a "feature" of Nastran (both MSC and NX). It is buried in the long history. I remember seeing a cusomter option that would change the defaults for the solutions, but not much else. I will try to find it on Monday.

I hope this helps. The move from Model Solution to NX Nastran is a journey.

Marilyn Tomlin
Siemens PLM Software

 

[Rhyder88]

Tomlin.. Thank you again for sharing your precious knowledge.
And yes.. it is a journey really and kind people like you are direction guiders..

 

[Helrezer]

Thanks, I am glad to help!