ANSYS problem

[Didier Beaudoin]

Hello,

I am new to ANSYS and I am trying to make a frame analysys. I have followed every step of a procedure to do so, but when I try to solve the analysys, I get this error all the time, no matter how I constrain my model:

"The value of UZ at node 20 (the node changes depending on where I put forces and constraints) i2 2.849378589E+11. It is greater than the current limit of 1000000. This generally indicates rigid body motion as a result of an unconstrained model. Verify that your model is properly constrained."

I don't know if it's a common error message or if it's something difficult to solve... Can someone help me and point me in the right direction?

Thanks a lot.

[Didier Beaudoin]

Hello,

I am new to ANSYS and I am trying to make a frame analysys. I have followed every step of a procedure to do so, but when I try to solve the analysys, I get this error all the time, no matter how I constrain my model:

"The value of UZ at node 20 (the node changes depending on where I put forces and constraints) i2 2.849378589E+11. It is greater than the current limit of 1000000. This generally indicates rigid body motion as a result of an unconstrained model. Verify that your model is properly constrained."

I don't know if it's a common error message or if it's something difficult to solve... Can someone help me and point me in the right direction?

Thanks a lot.

[Schumi_Jr]

Didier, I'm not familiar with ANSYS, but I might be able to help. It sounds like a connectivity/constraint problem. Are all your elements connected? You mentioned that this node changes depending on your loads and BCs. Is there any significance to this node (is it a BC or a load application node)?

If you email your model I can look at it in HyperMesh and see if there's any problems.

Also, have you posted this problem on a ANSYS-specific forum? You might get better help from someone there...

Good luck

[GTmule]

e-mail me your ansys file for the project (I'll need the mesh, nodes, and al the loads/constraints) and I'll have a look at it monday.

-Chuck

[Rob Davies]

I too am having trouble on ANSYS. I am trying to model the suspension with a LINK 8 and the chassis with PIPE 16 but the link 8 needs to be an element between nodes and the pipe 16 needs to be a line between keypoints. So i input all the node co-ordinates and then convert the ones I need to keypoints so I can use the PIPE 16 on them. But when I come to the solution it doesnt work

Any help?

[GTmule]

I'm not an expert, but why not just model the chassis ("frame" to us yanks) as beam elements? You just input the Moment of interia, and all that jazz, and let it go for it. That has the advantage of not dealing with all the node/keypoint garbage, you just use all nodes, just like w/ your links. (easy for me to say, I'm currently NOT screwing with it http://fsae.com/groupee_common/emoticons/icon_smile.gif )

-Chuck

[Rob Davies]

What type of beam? 3D eleastic 4?

[Lyn Labahn UW-Madison]

Rob. Try using Beam4 elements for the entire chassis, if you are using a space frame. You will have to enter in the moments of inertia, width, etc for the tubes.

[GTmule]

can't remember off the top of my head, it'l be in the help, it's whatever the 3D equivelant of Beam 3 is (beam 3 is only 2D).

[Jason Hickman]

Don't use a Beam4 for a tube approximation. Even though you input moments of inertia... for a tube, it still calculates it with rectangular x-section. Read up on Beam44's, they will better approximate a tubes behaivior. The hardest part of using Beam44's is setting up the real constants. You have to do it using the section tool.. you dont actually have to type all the moments....

I would even use them for your suspension members, and just couple the nodes at suspension points in appropriate directions, allowing for the right degrees of freedom.

[reetu]

Hi,

could you get a solution your problem stated below. I am encountering a similar problem while doing a multifield analysis.

Thanks


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Didier Beaudoin:
Hello,

I am new to ANSYS and I am trying to make a frame analysys. I have followed every step of a procedure to do so, but when I try to solve the analysys, I get this error all the time, no matter how I constrain my model:

"The value of UZ at node 20 (the node changes depending on where I put forces and constraints) i2 2.849378589E+11. It is greater than the current limit of 1000000. This generally indicates rigid body motion as a result of an unconstrained model. Verify that your model is properly constrained."

I don't know if it's a common error message or if it's something difficult to solve... Can someone help me and point me in the right direction?

Thanks a lot. </div></BLOCKQUOTE>

[Fred]

What about Pipe16 for tube elements ?