radioss : sub-modeling (cut...

Innovation Intelligence®

RADIOSS : Sub-modeling (cut approach)

V05 - July, 2012

Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

2


• Method :

The target of this approach is to study one area of the model with taking into account the deformation

of the full model through a section force.

In the defined section, displacement will be imposed in order to represent the "sub" part of the model.

Model Submodel Cut section


3


• Method

• Scheme

• From the full model, a section force is

created on the boundary of the selected

area.

• This section force, with specific

parameters, is added in the full model.

• The sub-model is created with all entities

which are inside the boundary and the

section force.

Full model

A files

T files

L files

SC files

Sub-model

RADIOSS

RADIOSS

HyperCrash

Section force

A files

T files

L files

Full model


4


• Method

• Scheme

• The full model is computed in order to get

the information on the section force.

• The information are stored in

<rootname>SC01 output file.

Full model

A files

T files

L files

SC files

Sub-model

RADIOSS

RADIOSS

HyperCrash

Section force

A files

T files

L files

Full model


5


• Method

• Scheme

• The sub-model can be computed using the

information of the <rootname>SC01 file.

• In the time history files (<rootname> T01 file),

forces balances are computed with the force

imported force the <rootname>SC01 file and

the force computed in the sub-model.

• The force differences are usually very small. In

the other case, it means the section force is not

correctly defined and do not take into account

all crash evens.

Full model

A files

T files

L files

SC files

Sub-model

RADIOSS

RADIOSS

HyperCrash

Section force

A files

T files

L files

Full model


6


• Industrial Applications

• Dummy analysis :

• Keep only the dummy and its direct environment

• 90% CPU cost of the full car model save

• Low speed impact :

• Keep only the deformed area


• Beginning of impact with high speed

• Keep only the deformed area



7


• Example 1

• The target of this simple sample is to show that

we can used this method for any type of element.

• Three plates are modeled with beam, shell and

solid elements. Imposed displacement is set on 1

side of the plate and the other one is clamped.

• The section is created like shown is the picture

(red line).

section Imposed

displacement

Boundary

conditions


8


• Example 1

• The deformation of the both models are the same.

• The full model is displayed with red color and the sub-model with blue color.

• The deformation of the both model is the same even if the section force is strongly deformed.

1 2

3 4


9


• Example 1

• The force in the section force and in the rigid body which model the clamping are the same

between the both models.


10


• Example 2

• The NEON full car crash model is cut on the middle of the front door in order to study the front

part of the car.

• This task is done using HyperCrash. The user defined the area he ants to keep and Hypercrash

defines automatically the section force, proposes to save the full model with the section and the

sub-model with the same section and the right parameters.


11


• Example 2

• Full model section

• The section defined for the full model contains all the entities cut defined by group of nodes,

bricks, shells, trusses, beams, springs and Interface ID.

• The time frequency (around10 times the minimum time step of model) and the data to store in the

<rootname>SC01 file is also set in the section.

• Isave = 1 : save only displacement

• Isave = 2 : save displacement and force

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/SECT/1

SECTION_SUBMODELING

# N1 N2 N3 GrNod Isave time-step filter

39927 113302 113306 2978 2 1E-4 0

# File name

# GrBrick GrShell GrTruss GrBeam GrSprg GrSh3N N-inter Iframe

0 2979 0 0 0 2980 0 12

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|


12


• Example 2

• Sub-model section

• The same section is defined for the cut model with the name of the <rootname>SC01 file and the

data to read :

• Isave = 100 : read only displacement

• Isave = 101 : read displacement and force

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/SECT/1

SECTION_SUBMODELING

# N1 N2 N3 GrNod Isave time-step filter

39927 113302 113306 2978 101 1E-4 0

# File name

NEON_000

# GrBrick GrShell GrTruss GrBeam GrSprg GrSh3N N-inter Iframe

0 2979 0 0 0 2980 0 12

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|


13


• Example 2

• Results

• The sub-model contains only less than 50% of the

elements of the full model and the CPU time is

also divided by 2.

• The force on the frontal rigid wall, the

displacement and the velocity of the nodes are

almost the same between the both models.

Full model Sub-model diff.

Node 294411 127049 -57%

Springs 4074 1664 -59%

Shells 269245 114500 -57%

CPU time 9.02E+05 3.97E+05 -56%

Nb cycles 301500 301500 0%


14


• Example 2

• Global deformation

1 2

3 4


15


• Example 2


• Section Z=500


16


• Example 2


• Section Y=0


17


• Example 2

• Displacement and velocity of the engine


18


• Example 2

• Displacement and velocity of dashboard upper


19


• Conclusion

• The sub-modeling method allows to study one area of the full model with taking into account the

displacement and forces on the boundary of the selected area.

• This method give good results. The deformation of the cut model is almost the same as the full

model.

• The CPU saved is proportional to the ratio of number of node kept in the sub-model and the

number of node of the full model.

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