About HM, Flexible bodies

LOKESH KATARI

In hypermesh, while creating the flexible bodies 

i wanted to use CMSMETH card CBN and CB Method

Now i wanted to know, will there be any difference in stiffness matrix in CBN and CB method?

Awaiting reply

Thank you

Altair Forum User

Hi,

the CB and CC methods are used for generating flexible bodies for use with some Multibody dynamics solvers, like MotionSolve. The CBN method can be used to generate CMS superelement information for some third-party solvers

LOKESH KATARI

ok sir, but i am using third party solver after converting into the flex body in which it used CB method

so some stiffness difference is coming..!

i want to know the difference so that i can use the sacling factor in that third party solver and get accurate results

help me with this

Awaiting reply

thank you

Altair Forum User

@LOKESH KATARI

 

Here is some theory about CBN from OptiStruct. You can search for generalized Craig Bampton method for CB

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LOKESH KATARI

Sir can u help in creating flexible body in hypermesh ??

what inputs and outputs cards should use

Thank You

Altair Forum User

Is it for MBD?

 

If yes, Please check this tutorial OS-T: 1930 Generating Flexible Body for use in MotionSolve

LOKESH KATARI

Sir i didnt get you where to check that OS-T:1930

LOKESH KATARI

i can see only MV-

Altair Forum User

Which version of HyperWorks are you using?

LOKESH KATARI

13 sir

LOKESH KATARI

Sir after using these model reduction methods 

how do we know this model is DOF decreased or not?

Altair Forum User

Hi,

 

I think CB comes with free free and constrained but CBN is not. 

 

13.0 is very old. You can search for the tutorial with same title

LOKESH KATARI

while creating flexible bodies in optistruct for simpack

i activated CBN and gave UB_FREQ 20 but i am getting 127modes and fbi file around 12GB 

i need only 40 modes. how to decrease those modes?

Altair Forum User

Please provide NMODES and try again. 

LOKESH KATARI

yes sir  i tried still its showing more number 

i am doing it for chassis sir

LOKESH KATARI

When i gave 12 NMODES after analysing its showing 114 modes created

LOKESH KATARI

Altair Forum User said:

When i gave 12 NMODES after analysing its showing 114 modes created

please help me with this

thank you

Altair Forum User

@LOKESH KATARI

 

Can you share the model file, please?

LOKESH KATARI

sir actually i am working in a company i cant share anyway it is 80Mb file commercial vehicle chassis

 

Altair Forum User

@LOKESH KATARI

 

if you remove the ASET you should get the same number of modes as specified in NMODES.

 

The extra modes are the number of FEM DOF that are in the interface. 

LOKESH KATARI

Sir with the help of ASET only i can generate markers in simpack!

Altair Forum User

OK, If you are using other than CBN and GYUAN, the number of modes without ASET is equal to what you get. 

Altair Forum User

I think the same applies to CBN also. 

LOKESH KATARI

ok sir

Nirbhay_22070

Hello,

 

I need help!

I am working in optistruct and have used CBN method to make flexbody. I need to use the file in SIMPACK for MBS. Can anyone tell me, how to generate fbi format in hypermesh.

 

Thanks in advance