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Mass inclusion

Hello there, I am new to femap and I was hoping I could get some help from the community.

I'm in the process of loading a model and I want to include the mass of the whole mode. Is that possible? if yes, how can i do it in FEMAP?

Attached is a pic of the model

Thank you very much in advance.

 

16 REPLIES

Re: Mass inclusion

Dear lahmstanley,

 

Your question is not clear enough. Could you gives us more informations about what you would to do ? You want to include the mass of the hole aircraft and perform analysis on this portion? 

Regards,

SN

Seif Eddine Naffoussi, Stress Engineer

Re: Mass inclusion

Yes, instead of calculating the loads from mass of the vertical tail and manually applying them on the nodes where the tail connects with the fuselage, I'd like FEMAP to some how automatically calculate the loads caused by mass of the whole structure.

Regards,
STANLEY NDUNG'U.

Re: Mass inclusion

You can use the freebody tool in Femap, it is a powerful tool for this kind of operation. 

First, under postprocessinf toolbox / freebody / freebody properties, create a freebody. Then uncheck all freebody contributions parameters except MultiPoint reaction. 
Hit ok and add the depedent nodes and you are done. you can also sum the total force on the four nodes. 
This force should be equal to Mass of the vertical part*Accel. 
For more details, go to femap help you will find a more detaild explanation. 

Regards,

SN

 

Seif Eddine Naffoussi, Stress Engineer

Re: Mass inclusion

Hello, Thanks for the reply. I tried but to no avail. Plus, the vertical tail is fixed on the 16 nodes on the fuselage.

What about the mass of the fuselage? shouldn't I include the loads created by it to get more accurate results ?

please help me out, i need to get these results going.

 

Re: Mass inclusion

Hello!,

To account for the mass of the FE model as dead load simply create a new LOAD CASE and activate the BODY LOAD using "Model > Load > Body":

 

 

Of course, make sure to define the DENSITY in the material properties!!.

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: Mass inclusion

OK, So i should edit the material properties and include the density of the materials.

In the dead load dialog, what's the 9810 ? What about the functions ? I'm I supposed to deifine the functions ?

Re: Mass inclusion

Hello!,

This is the acceleration of gravity, 1G = 9810 mm/s2, as you know Force = Mass x Acceleration. Please note to have a coherent system of units then Lenght should be in milimeters, Young modules in MPa, loads in Newtons and DENSITY in Tons/mm3.

 

You know that in FEMAP you can "play" in any system of units you like, the important is to be coherent, 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: Mass inclusion

Thank you Blas. Your help was much appreciated.

I have one more question though, I hope you would be in a position to help.

I'd like FEMAP to automatically create a sort of spider, with the dependent node on a certain distance towards the nose of the fuselage, and the independent nodes being the ones constrained at the moment(please have a look at the attachments). I suppose if I create the spider, it will give a better simulation of how the fuselage works.

 

Re: Mass inclusion

Hello!,

Simply create the RBE3 element with command "Model > Element > TYPE => Rigid > RBE3":

 

 

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/