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Incorrect Section properties from Mesh?

Pioneer
Pioneer

Hello,

I have a L-Angle made of Al 2024-T3 Extrusion 0.0625in thickness. The legs are almost equal length 0.625 in.

 

The flange is represented in Femap using 2D quad elements. I wanted to calculate Section Properties of the flange, but it seems like Femap may be giving incorrect output or my methodology is incorrect. I am hoping for some guidance on the same.

 

Element Selection. Arrow Indicates Section Y AxisElement Selection. Arrow Indicates Section Y AxisShell PropertiesShell Properties

Section Properties:
Area                          A=   0.156827    
Centroid (from Origin):       Cy=  0.313655      Cz=  -0.125      
Moment of Inertia:            Iyy= 0.000816805   Izz= 0.00514286    Iyz=  0.          
Principal Moment of Inertia:  I1=  0.00514286    I2=  0.000816805 
Radius of Gyration:           Ry=  0.0721686     Rz=  0.181089    
Angle to Principal Axes:      Ang= 0.          

I know for sure the area is incorrect. It should be around 0.078 in^2 or half of what Femap is calculating.

 

What could be going wrong? AFAIK, there are no thickness offsets specified in the model.

3 REPLIES

Re: Incorrect Section properties from Mesh?

Siemens Phenom Siemens Phenom
Siemens Phenom

FEMAP does not calculate the edge-on section property, but the one in the same plane as the elements you pick. 

 

Mark.

Re: Incorrect Section properties from Mesh?

Pioneer
Pioneer

Hi Mark,

So are you saying that if I pick elements which are not edge ones, I should get a more accurate calculation from Femap?

Re: Incorrect Section properties from Mesh?

Siemens Phenom Siemens Phenom
Siemens Phenom

The cross-section calculator expects a planar mesh of the cross section for which you want properties.  In the case of the L section, you would need to send in this mesh in order to get the cross-section properties -

 

XSection.jpg

 

Mark.