Chassis analysis with Altair Hyperworks

[peat_785]

Hi all!!

I'm following this tutorial:

http://training.altairuniversi...-a-student-race-car/ (http://training.altairuniversity.com/e-learning/by-altair-_2/simulation-driven-design-of-a-student-race-car/)

Unfortunately I get a number of error when running my model.
The chassis was created in Hypermesh. The procedure was as follow: temporary nodes were created and then lines were build with respect to the previously defined temporary nodes. From there the procedure was as explained in the above link but this is the result:



*** INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 391
independent grid id = 56
a dependent grid id = 2
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.

*** INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 392
independent grid id = 60
a dependent grid id = 48
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.

*** INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 393
independent grid id = 61
a dependent grid id = 49
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.

*** ERROR # 723 ***
An invalid rigid element.
This RBE2 is not connected with any structural element.
RBE2 element id = 395
independent grid id = 59
Note: If this rigid element is also connected with other rigid elements,
then this error means that there is rigid body mode or mechanism remained
in this rigid element chain due to lack of connected structural elements.

*** ERROR # 723 ***
An invalid rigid element.
This RBE2 is not connected with any structural element.
RBE2 element id = 396
independent grid id = 58
Note: If this rigid element is also connected with other rigid elements,
then this error means that there is rigid body mode or mechanism remained
in this rigid element chain due to lack of connected structural elements.

*** INFORMATION # 741
No need to constrain the rotational d.o.f. of this dependent grid.
RBE2 element id = 397
independent grid id = 62
dependent grid id = 50
This is because there isn't any stiffness and load on the rotational
d.o.f. of the dependent grid.

*** INFORMATION # 741
No need to constrain the rotational d.o.f. of this dependent grid.
RBE2 element id = 397
independent grid id = 62
dependent grid id = 55
This is because there isn't any stiffness and load on the rotational
d.o.f. of the dependent grid.

*** INFORMATION # 741
No need to constrain the rotational d.o.f. of this dependent grid.
RBE2 element id = 398
independent grid id = 63
dependent grid id = 51
This is because there isn't any stiffness and load on the rotational
d.o.f. of the dependent grid.

*** INFORMATION # 743
The total number of rigid elements, whose rotational dependent d.o.f.
are removed because there is no need to constrain those d.o.f., is 4
The total number of grids whose rotational d.o.f.s need not be
constrained in RBE2 elements is 4
Note: These rotational d.o.f. are not automatically constrained because
some of the dependent grids in the same RBE2 require their
rotational d.o.f. to be constrained.

Anyone knows how can i fix these Error? As you can see all the errors are due to the 1D rigid elements (RBE2 elements).

Cheers

[billywight]

Your information issues are because you likely have RBE2's with all 6 DOF attached to solid elements that only have 3 DOF's. This won't cause any issues, but you could fix it by removing the DOF's 4,5,6 on your RBE2's.

As for your Errors, try doing a node equivalence to see if you have two nodes on top of one another. It's in Tools - Edges. Select the elements that should have equivalenced nodes, enter a tolerance, then preview equivalence. If a brown dot shows up at the nodes, then go ahead and hit equivalence. Then try re-running it.

[peat_785]

Thank you very much billywight. Unfortunatelly the changes lead me to another error

*** ERROR # 2110 ***
The dependent d.o.f. is constrained by grid or spc data.
RBE2 element id = 397
grid id = 61
component = 1

*** ERROR # 2110 ***
The dependent d.o.f. is constrained by grid or spc data.
RBE2 element id = 398
grid id = 60
component = 1

One more time I have try everything to fix it without luck. Any suggestion for this ones!!??

cheers

[billywight]

You have constraints applied to the end(s) of your rigid spider(s). Since those nodes have movement defined by both the movement of the independent node in the rigid spider and the SPC constraint, they are over defined. You either need to remove the constraints from those nodes or you need to remove the connectivity of the rigid from those nodes.

[peat_785]

Originally posted by billywight:
You have constraints applied to the end(s) of your rigid spider(s). Since those nodes have movement defined by both the movement of the independent node in the rigid spider and the SPC constraint, they are over defined. You either need to remove the constraints from those nodes or you need to remove the connectivity of the rigid from those nodes.

Thank you very much billywight. Now at least the simulation is running http://fsae.com/groupee_common/emoticons/icon_biggrin.gif Something is happening though, the result is given in 2D (x-z plane) rather than in 3D :S

[billywight]

Well, I'm not sure how you get results in only one plane (or if I'm understanding your problem correctly). Are you using HyperView for results? You shouyld be able to open up the session file (.wmv) in HyperMesh Desktop and that will load the model. Apply a contour plot of stresses or displacements and you should be good to go. Since it's 1D beams, you'll have to apply the correct stress result that you're looking for.

[peat_785]

Originally posted by billywight:
Well, I'm not sure how you get results in only one plane (or if I'm understanding your problem correctly). Are you using HyperView for results? You shouyld be able to open up the session file (.wmv) in HyperMesh Desktop and that will load the model. Apply a contour plot of stresses or displacements and you should be good to go. Since it's 1D beams, you'll have to apply the correct stress result that you're looking for.

Thank you very much billywight, finally everything is working!!

cheers