Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

ERROR # 330

Altair Forum User

*** ERROR # 330 ***

RBE3 element 715535 cannot support a y-moment - check element data

*** ERROR # 332 ***

RBE3 element 715536 has singularities - check element data

*** ERROR # 330 ***

RBE3 element 715537 cannot support a y-moment - check element data

*** ERROR # 332 ***

RBE3 element 715538 has singularities - check element data

Number of bad RBE3 elements = 4

What should I do to solve this problem? Thank you very much!

Find more posts tagged with

English

OptiStruct

Accepted answers

All comments

Altair Forum User

Hi,

Can you please run the element quality check from tools>> Check elems or Tools menu>> model checker>> OptiStruct and on the left you will see a entity browser. Use this model checker option to auto eliminate modelling issues.

Update the dependency of the rbe3. There are few scripts available to update multiple RBE3 elements on our script exchange @ http://www.altairhyperworks.com/Script-Exchange.aspx

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Thank you!

Merula_20758

Hi,

I get the same error: #330!

Sadly I dont know whats the reason behind it and can not resolve it. Element checks are ok on this rbe3 element.

Merula_20758

Please tell me where the mistake happens

http://www.youtube.com/embed/zhyGzVoxa9A?vq=hd1080&autoplay=1

Altair Forum User

Hello,

there are some reasons why Optistruct gives this error. (my suggestion, the connected element hasn't rotational dofs (e.g. solid))

But i want to ask, why you are using dof 4,5 or 6 (moments) at a RBE3 element ??????

Here a hint from a Nastran FAQ:

'The most common user error in RBE3 element specification results from placing 4, 5, or 6 in the Ci (independent DOF) field when also including some translation components.

The action of the element is somewhat irrational for this specification.'

Best regards,

Mario

Altair Forum User

Hi Merula,

An rbe3 should have at least more than 2 legs, or it will have singularity issues, also at the dependent make it to all 6 dof and at the independent make to 123 dof.

Merula_20758

>Tried it all, but it wont help....

The thing is, that there should be no moment as the video suggests...

It is a 3 point bending beam with a force introduced on the top on one dependant node... 5 legs which transfer the DOFs on the part.

@ mario: no moments (456) are used. see on video: 5:00

tinh

>Tried it all, but it wont help....

The thing is, that there should be no moment as the video suggests...

It is a 3 point bending beam with a force introduced on the top on one dependant node... 5 legs which transfer the DOFs on the part.

@ mario: no moments (456) are used. see on video: 5:00

Hi,

in your case independent nodes move to right and a y moment generated, but RBE3 not support this moment, so it seems to be collapsed

You should not make RBE3 for a colinear nodes, add some more nodes beside and set weight of them is 0

or if right support is 123 same as the left then ok (no y moment)

Altair Forum User

Hi Merula,

From help:

It is recommended that for most applications only the translation components 123 be used for Ci. An exception is the case where the Gij are collinear. A rotation component may then be added to one grid point, to stabilize its associated rigid body mode for the element.

Since you are using solid element which doesn't have any rotational DoF, the above may not be valid.

Merula_20758

Thanks for your answers. If I add more points like tinh suggested, the model does not collapse and the model works just fine. So no colinear nodes for RBE3 connected to solids?

Altair Forum User

Hi Merula,

I sent the modified model by adding more nodes to the RBE3 as Tinh suggested.

But, why not use RBE2s when you want to load on col-linear nodes?

tinh

Hi Merula,

I sent the modified model by adding more nodes to the RBE3 as Tinh suggested.

But, why not use RBE2s when you want to load on col-linear nodes?

I think so. because in his case there is no deformation between loaded nodes. so RBE2 is ok

Altair Forum User

Yes,

with RBE3s more nodes are taking load (unless it doesn't matter) and may not work on collinear nodes.

RBE2s should be fine in such case.

Merula_20758

Thanks for your answers. Indeed RBE2 elements are an option but as mentioned RBE2 elements prevent any movement between the loaded nodes which is not the case in real life scenario.

Consider the free ends over the thickness of the specimen. As the free end is not tied into position from 'both' sides, it will deform with higher amount as shown in the following picture.

It is not much of a difference and could be ignored, i am aware of that but to show the principles of RBE 2 and 3 it is the reason for choosing rbe3.

Best Regards,

Merula

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

I had the same problem..

I solved by creating the independent nodes not alligned one to each other on a line, but letting them lie on a plane.

I hope this would work also for you!

Altair Forum User

I used RBE3..

Altair Forum User

Dear All,

I face quite the same problem, but I can't manage to solve it.

I work on the optimization of a support to hold a kind of rigid pipe.

We just want to model the impact of the weight of the pipe, so the pipe is modeled by an RBE3, with the weight of the dependent node (located at the Center of Gravity of the pipe) equal to the weight of the pipe.

All the independent nodes only have translation DOFS.

Cam you please help me?

Thanks a lot

Florian

Altair Forum User

I should have precised that I get the message :

*** ERROR # 326 ***
RBE3 element 56155 cannot support a x-force - check element data.

Thanks a lot

Florian

tinh

Hi,

What are you doing with the RBE3? I don't see any load applied on its dependent node

And, I see you set up a DTPL optimization, but there is no non-design property

Altair Forum User

Hi @Florian Kimmerlin

The weight factors of RBE3 are zero. Please update the RBE3 with a weight factor and try again.

Altair Forum User

Hi both!

Thank you very much for your answers!

The idea is to simulate the interaction between the pipe and the support. That's why there are no loads applied on the dependent node.

I just need to implement how the natural weight of the pipe will interact with the support through the gravity and the g-loads. The pipe is an inert body.

I hope this is clear...

I don't need any non-design property (except if the software does), because I would like to get a kind of 'spider shape' to later cover with plastic, so I don't really care. Should I change it?

As for the weight, the pipe is 2 kg. I have set the dependent node at 2kg and the independent ones at 0kg. But if I set the independent nodes to 2 kg too, I fear that the weight won't be concentrated on the center of gravity anymore (which is my dependent node)? and how to know that the total weight will still be 2kg?

Thanks a lot for your appreciated help

Regards

Florian

tinh

/emoticons/default_rolleyes.gif' title=':rolleyes:' /> Does the 'weight' you said mean 'weight factor' of RBE3?

Are you sure the weight factor is 'Kg weight'? I think a review is needed.

Altair Forum User

Thanks a lot for your answer.

I just changed the weight factors and it now works!

Thus I have one final question for you: Are the weight factors representative of the weight of the RBE?

I mean: the pipe is 2kg in practice. When I change the weight factors of the RBES, does it affect these 2 kg, or does it just tell the software how to spread those 2kg among the different nodes?

Thanks a lot

Florian

Altair Forum User

Thus I have one final question for you: Are the weight factors representative of the weight of the RBE?

No, what RBE3 has is weight factor and not weight. Weight factor determines how much load should be transferred to the rbe3 legs.

tinh

To distribute 2kg from dependent node to indep nodes,

you can create a CONM2 = 2kg and apply GRAV

or create a force = 2*9.81N at the dependent node

Altair Forum User

Thank you very much for your help, I really appreciate!

best regards

Florian

Altair Forum User

Dear Tinh,

I tried to apply your method (CONM2 + GRAV) but I face a new error:

*** ERROR # 2148 ***
Invalid design problem.
All the sensitivities of response 1 (objective) are zero.

The thing is that without the CONM2, it works...

The only difference between the 2 runs is CONM2...

Any idea?

Thanks!

Unable to find an attachment - read this blog

Altair Forum User

Dear all,

Is there a particular property to apply to CONM2 to solve this problem?

Thanks a lot

Florian

Altair Forum User

Hi,

Please assign PMASS property and try again,

Also, please define a design and non-design space for better results.

Altair Forum User

Dear Prakash,

Thank you very much for your answer.

Once again, I really appreciate.

Sadly, I have added the PMASS property and the NDS space but nothing changed... I still face the same error saying all the sensitivities of the objective (minimizing the mass) are zero.

I have had a look at tutorials and on the internet, but I can't find any solution. Do you have any other idea?

Thanks a lot

Florian

Unable to find an attachment - read this blog