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# Unit System

Experimenter

Hello all. I am a new user to FEMAP.
I am doing FEA Analysis and get results from von mises stress. But the problem is that I can see only numbers without units. There is not unit legend in the graph.

Do you how can I show up the units or change the unit system to SI ??

9 REPLIES

# Re: Unit System

Valued Contributor

If the dimensions in  centimeter and the load in kg in the result obtain kilograms per centimeter squared.

# Re: Unit System

Experimenter
ok but how could i see what dimensions does it use?

Panagiotis Rokanis

# Re: Unit System

Solution Partner Phenom

Dear Rokanys,

FEMAP do not manage any unit system, is the only user responsibility to have a coherent system of units between length, area, force, stress, etc..

The first task to do is to set the units when importing geometry, this is the only case that FEMAP set units: if you want geometry in meters, set scale factor = 1.0

Later is only you the responsible to set a coherent system of units: if you define geometry in meters, and enter loads in N or pressure in N/m2, and define Young Module in Pascals, then stresses will be in Pascals (ie, N/m2) as well and displacement results in meters, OK?.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

# Re: Unit System

Pioneer

Here is a link to a usefull PDF (courtesy of CADimage PLM).

http://c2201042.cdn.cloudfiles.rackspacecloud.com/TechTip-Engineering-Units.pdf

Go to page 5 in this PDF, there you have most of the units in all major unit systems (including mm) and how to convert between them.

# Re: Unit System

Experimenter

Thank you! It seams to be working!
But I think it's not user friendly. It must be able to define units or unit system. It's complicated

# Re: Unit System

Solution Partner Phenom

Dear Panrok90,

In fact, this is a problem in FEMAP, specially for beginners. But I agree with you that this should be improved urgently, not excuses, any modern FEA software like FEMAP should include native support of units management to avoid user errors. Please developers ....

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

# Re: Unit System

Experimenter
And another thing to consider. I am using the optimisation module.
In the results I can get only output vector for von mises stress
(E_CTRL_INPUT) and material density (MAT_PROP_NORMALISED)
Do you know how to show an output vector with deformation (total
translation)?
Otherwise, how can I run an normal FEM analysis with the optimised shape as
input, and not the initial one.

______________

Panagiotis Rokanis

# Re: Unit System

Solution Partner Phenom

Dear Panagiotis,

I guess you are referring to TOPOLOGY Optimization??. This is TOSCA, not NX NASTRAN, then here not too much to do, this is a third party software, take a look here:

http://iberisa.wordpress.com/2011/08/28/optimizacion-topologica-con-femap-y-nx-nastran/

Regarding to use the optimized shape as input for a FE model, well, the focus behind Topology Optimization is to get the "design idea", then based in the idea you modify the geometry base and perform all the FEA analysis required.

Take a look to this post for "ideas" to take advanced of the optimized shape written in STL. The workflow is to create geometry and the to mesh with solid elements. But from the practical point of view the most efficient way, in my opinion, is create new geometry (in FEMAP or using SolidEdge ST6) based in the optimized shape:

http://community.plm.automation.siemens.com/t5/Femap-Discussion-Forum/Is-it-possible-to-export-defor...

http://community.plm.automation.siemens.com/t5/Femap-Discussion-Forum/How-to-create-geometry-in-FEMA...

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

# Re: Unit System

Experimenter
This is what I was thinking to do.
Actually, I use Solidworks. So, I am going to create new geometries
depending on the Topology results, and then new FEM analysis
Thank you for your help. I really appreciate it.

______________

Panagiotis Rokanis