Geometric Distribution VS Total per object. 1

[bebopsan]

Hello, this is my first post and first of all I want to tell you that I've found this place to be very usefull when looking for info on Siemens NX, specially on topics reltaed to NXOpen, and am willing to participate on your forums.

I am trying to model deformations on a wing shell structure when applying moments do to drag of rotor pylons, and found that I get very different results when defining the load distribution as either "Total per object" or "Geometric Distribution". I don't know the difference between these two parameters and have not found a definition on the documentation.

It would be great if someone could give me a brief description of these two configurations, and how they relate to the preprocessing of loads.

 

[BlasMolero]

Hello!,
It´s easy and simply, in the Distribution group, select the method for distributing the force or moment over the geometry or FE entities:

• Select "Total Per Object" to apply the SAME magnitude to every EACH selected item, or

• Select "Geometric Distribution" to distribute the total force or moment over all the selected items based on the area. All the nodes on the selected items then get a fraction of the force or moment based on the area of the associated elements.

• Select "Spatial" to use a unitless field to map the force or moment to the nodes.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[bebopsan]

Thank you for your help, it is indeed simple. Now, If I were to add a unitless field would it have to be associated to each node in a three dimentional coordinate system, or could I use a simpler planar distribution? And how would the table for the field look like? I actually have 2D model of the Mx moments over the wing and would like to apply such a distribution, do you perhaps have an example of a field you have used that I can use as a reference?

Best regards.

 

[BlasMolero]

Hello!,
If you know the resultant of the moment in a point in the space the best approach is to use a Spider RBE3 element to distribute the moment load over the wing surface meshed with shell elements. These elements are well-suited for distributing mass and loads in a model without adding stiffness. A spider element is defined as a single core node that is connected to multiple leg nodes with rigid or constraint elements. To define a spider element, use the Point to Face 1D connection.

Regarding fields in NX Advanced Simulation, you can use the fields capability to define a function for one or more dependent domains/variables based on their relationships to one or more independent domains/variables.

In Advanced Simulation, you can use fields to:

• Define how boundary conditions vary with time, temperature, or frequency. For example, you can use a field to define how the magnitude of a force varies with time.
• Define how the magnitude of a boundary condition is distributed spatially. For example, you can use a field to vary the magnitude of a force depending on its location on a surface.
• Define material properties. For example, to define a hyperelastic material, you can use a table field to define stress/strain data.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/