ERROR # 330
Altair EmployeeAnswers
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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
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Thank you!
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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.
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Please tell me where the mistake happens
http://www.youtube.com/embed/zhyGzVoxa9A?vq=hd1080&autoplay=1
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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
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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.
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>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
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Altair Forum User said:
>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)
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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.
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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?
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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?
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Altair Forum User said:
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
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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.
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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"?>
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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!
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I used RBE3..
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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
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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
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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
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The weight factors of RBE3 are zero. Please update the RBE3 with a weight factor and try again.
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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
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/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.
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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
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Altair Forum User said:
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.
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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
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Thank you very much for your help, I really appreciate!
best regards
Florian
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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!
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Dear all,
Is there a particular property to apply to CONM2 to solve this problem?
Thanks a lot
Florian
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Hi,
Please assign PMASS property and try again,
Also, please define a design and non-design space for better results.
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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
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