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Concerning Load

Builder
Builder

Hello Everybody,

 

I want to apply 5N of force on the top of the model, do I need to divide the selected node with 5N as shown in figure or I can just apply directly 5N.

 

If I will divide then the amount of force would become so high.

Could somebody direct me? which one is correct

 

Thank you in advance.

9 REPLIES

Re: Concerning Load

Siemens Phenom Siemens Phenom
Siemens Phenom

If you input 5 as the value of the force, you would be applying 5N to every node selected, so just divide 5 by the number of nodes selected for the value of the force.

 

If you have surfaces where that force is applied, you can input 5 as the value of the load and select the option for Total Load in the Create Loads dialog box.

Best Regards,
Chip Fricke
Principal Applications Engineer - Femap Product Development

Re: Concerning Load

Builder
Builder

Sir,

 

Total Force -  5N

Force applied on node – Node Selected /Total force – 23639/5N

-      4727.8N

If I divide then the force become two high. Do I need to set the value somewhere or have to do something additional.

 

Re: Concerning Load

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Hello!,

Another option is to use a rigid element RBE3 to distribute the load. The RBE3 element is a powerful tool for distributing applied loads and mass in a model. Unlike the RBAR and RBE2 elements, the RBE3 doesn’t add additional stiffness to your structure. Forces and moments applied to reference points are distributed to a set of non-collinear independent degrees of freedom nodes based on the RBE3 geometry and local weight factors.

 

rbe3-example.png

 

rbe3.png

 

 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: Concerning Load

Builder
Builder

Sir, could you please tell me how can I set Rigid element RBE3 to distribute 5N load

Re: Concerning Load

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Hello!,

  • Use command MODEL >ELEMENT and in the TYPE choose RIGID.
  • Next make sure to select the RBE3 (Interpolation) "tab".
  • In the DEPENDENT section do not select any node, simply click NEW NODE AT CENTER, this way FEMAP will create a new node at the center of gravity: this is the node where you will apply your 5N load.
  • In the INDEPENDENT section click in NODES and select all the nodes where you want to receive the 5N distributed load. And you are done!.
  • To learn more about rigid RBE2 & RBE3 elements visit my blog in the following address: https://iberisa.wordpress.com/2015/10/13/rbe2-vs-rbe3-on-femap-with-nx-nastran/

rbe3-dof.png

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: Concerning Load

Builder
Builder

Sir,

 

I appreciated for the help and I do understand what you mentioned above. And I also read in your blog.  I followed the same procedure but I want to ask you do I need to select all the DOF in RBE3 independent interpolation.

And after that do I need to go to load section and apply the node, because there is no any option prompted in RBE3 Section afterwards where I need to apply 5 N load or was it selected automatically.

Re: Concerning Load

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Hello!,

Selecting only TX,TY,TZ in INDEPENDENT node is correct. The most common user error in RBE3 element specification results from placing 4, 5, or 6 in the Ci (independent DOF) field in addition to the translation components. The rotations of the dependent point are fully defined by the translational motion of the independent points. The ability to input 4, 5, or 6 in the Ci field is only for special applications, such as when all of the connected points are collinear.

YOU apply the load, not FEMAP. The load should be appplied in the DEPENDENT node just created by FEMAP because the action choosed "NEW NODE AT CENTER", simply use that new created node to apply your 5N load.

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: Concerning Load

Phenom
Phenom
I see you have used an RBE, but if you were applying the loads to all the nodes you needed to apply 5N/23639 to each node, not 23639/5N to each node.

The RBE method is easiest, but just keep in mind that "big" RBE's (ie. connected to thousands of nodes) will slow certain types of analysis down, because the RBE makes the matrices "denser" than they would otherwise be.

Re: Concerning Load

Builder
Builder

Yes, You are right RBE is taking thrice times in comparison to selected node.