Stress results

[admaiora]

Hi,

I need your ideas, I don't understand this behavior.

The case is very simple:

A 200x60x10 steel plate (or whatever)

Linear Static with Inventor, detect remove Rigid mode activated and frictionless constraint to both edges (if shell analysis) faces (if solid analysis)

This is the result (for sheel and solid analysis)

I don't like the stress distribution (or I don't understand it..)

I would expect more something like that (done in Nastran with INERTIALRELIEF=AUTO)

better , more uniform.

Can you help me to understand this?

And what the heck is this tension?

Thanks!!

(File atatched)

[admaiora]

Hi,

I need your ideas, I don't understand this behavior.

The case is very simple:

A 200x60x10 steel plate (or whatever)

Linear Static with Inventor, detect remove Rigid mode activated and frictionless constraint to both edges (if shell analysis) faces (if solid analysis)

This is the result (for sheel and solid analysis)

I don't like the stress distribution (or I don't understand it..)

I would expect more something like that (done in Nastran with INERTIALRELIEF=AUTO)

better , more uniform.

Can you help me to understand this?

And what the heck is this tension?

Thanks!!

(File atatched)

[imajar]

Hi @admaiora,

Firstly, Let me say that this case should have uniform stress across the entire thing (this is a textbook problem of uniform tension and should have uniform stress of 100 MPa everywhere), not a changing stress from 0 to 100 like the Inventor Nastran plot shows

The Nastran result is incorrect.  The inertial relief option is intended for structures that are floating in space, such as airplanes, boat, and spacecraft.  It is not meant to be used to fully constrain a structure that would normally be constrained.  You need to fully constrain the object yourself, so for example, on the short side constrain Tx, Ty, Ry, and Rz.  And on the long side constrain Ty, Tz, Rx, and Ry.  Set the Inertial Relief back to the default setting and rerun, and you will get the correct result of 100 MPa.

As for the inventor analysis, I did see the same weird behavior as you.  Two comments:

Firstly, my the scale on my plot was from 99.953 to 100.074 MPa, if I reset the plot to go from 0 to 100 MPa, the result looked correct.  Is this the same for you?

Secondly:  Personally, I would avoid the automatically remove rigid body motion option whenever possible.  

[imajar]

Hi @admaiora,

Firstly, Let me say that this case should have uniform stress across the entire thing (this is a textbook problem of uniform tension and should have uniform stress of 100 MPa everywhere), not a changing stress from 0 to 100 like the Inventor Nastran plot shows

The Nastran result is incorrect.  The inertial relief option is intended for structures that are floating in space, such as airplanes, boat, and spacecraft.  It is not meant to be used to fully constrain a structure that would normally be constrained.  You need to fully constrain the object yourself, so for example, on the short side constrain Tx, Ty, Ry, and Rz.  And on the long side constrain Ty, Tz, Rx, and Ry.  Set the Inertial Relief back to the default setting and rerun, and you will get the correct result of 100 MPa.

As for the inventor analysis, I did see the same weird behavior as you.  Two comments:

Firstly, my the scale on my plot was from 99.953 to 100.074 MPa, if I reset the plot to go from 0 to 100 MPa, the result looked correct.  Is this the same for you?

Secondly:  Personally, I would avoid the automatically remove rigid body motion option whenever possible.