Cancel
Showing results for 
Search instead for 
Did you mean: 

Unit of rotation (output)

Pioneer
Pioneer

Hello,

 

Femap Nastran NX analysis is unitless. But we should be consisitant with the units. Can anyone tell me if I apply a moment at a node about one axis what will be the unit of rotation obtained as the out put?

 

I am keeping the solid geometry scale factor in meters ( in File--Preferences--Geometry/model), which means am following a N-m-s unit system (then moment will be in Nm). Is the rotation will be in radians?

 

Regards,

Muhammed sadique

19 REPLIES

Re: Unit of rotation (output)

Gears Phenom Gears Phenom
Gears Phenom

You can create simple 1 element beam apply moment and compare rotations from Femap with theory. But I`m 95% sure that your assumption is right and output units are radians.

Re: Unit of rotation (output)

Pioneer
Pioneer
Okay. Thank you

Re: Unit of rotation (output)

Genius
Genius

There is an option in preferences to show "Angles as 0 -> 360". 

 

I know this affects the measurment of angles. 

 

I don't know if if affects output. 

 

Test models, like   says, are always a great check.

 

FEMAP - Angles.png

 

 

Highlighted

Re: Unit of rotation (output)

Siemens Phenom Siemens Phenom
Siemens Phenom

Nastran output for displacement rotations is always in radians.

 

However, on the input side:

1) defining node locations in a cylindrical system, then the angle is in degrees.

2) enforced displacements when using rotation dof's, then Nastran expects radians.

 

Regards,

 

Joe

Re: Unit of rotation (output)

Pioneer
Pioneer

Hello every one,

 

I think it is in angles. I did a manual calculations by considering the distance between nodes. First I took coordinates of the point and node as shown the attahced file (see the white circles). The coordintes were the same. the pink colored model is the deflected version of the transparant model (tansparant blue). As it gives the same coordinates I understood that the femap doesn't give the coordinates for the defelcted model. 

 

Then i checked the distance between the points in undeflected model (shown in the green circle) and used that to calculate the angle manually. The angle was 18.772 and then I used the femap to check the angle between the points in femap. I got 18.77282. From that I concluded that femap is showing the angles in degrees.

 

 

Hello Fembrackin,

 

I imported the solid model to the femap and did the meshing. When I am supposed to define the coordinte system ? I do have a independent node on which the moment is applied. The indepentend node is defined in rectangular coordinte system. Also on the independent node the constraint were applied to restrict 5 DOFs except the rotation about x axis(the moment was applied about this axis).

 

Regards,

Sadique

 

 

 

 

Re: Unit of rotation (output)

Gears Phenom Gears Phenom
Gears Phenom

Emm... I think that we are talking about different angles.

Re: Unit of rotation (output)

Pioneer
Pioneer

Thank you for your reply
My question is this.
In postprocessing, in countour when I select rotation R1 (about x axis-about this axis I gave the moment 1 unit value (Nm) I am getting a countour plot as shown below. Please find the image for your references. The moment was applied on an independent node which is connected to the solid using rigid elements (see the images).What is the unit of the output am getting in the countours?

1.JPG2.JPG3.JPG

Re: Unit of rotation (output)

Gears Phenom Gears Phenom
Gears Phenom

I have different example (in attached archive).

Try to check rotation at center node of spider using data table.

Re: Unit of rotation (output)

Pioneer
Pioneer
Thank you.

Could you please give the equations (or some reference) for the theoretical calculation for the rotation.
Is there any way in Femap to apply a torque (in Nm/revolution) about some axis instead of moment?

Regards,
Sadique