Download - Adams-to-Nastran - MSC Softwarepages.mscsoftware.com/rs/mscsoftware/images/AdamsUser...Overview • There is a need for model translation from Adams to FEA 5/26/2011 4 Multibody Dynamics

Adams-to-Nastran

Jose L Ortiz, PhD.Adams User MeetingMunich - May 19, 2011

Agenda

• Overview

• Manual and Scripted Translation

• Theoretical Background

• Implementation Details

• Example

• Q&A

5/26/2011 2

• Overview– Introducing Adams-to-Nastran




• Example

• Q&A

Agenda

5/26/2011 3

Overview

• There is a need for model translation from Adams to FEA

5/26/2011 4

Multibody Dynamics System modelAdams

Finite Element Analysis modelFEA

Overview

• Introducing Adams-to-Nastran

– Performs an automatic model translation (export) from Adams to FEA

– Available for the past 2 releases

– As of today, an MD license and a LINEAR license are required

– Available only in the Adams/Solver C++

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Overview

• Introducing Adams-to-Nastran (cont.)

– The export process creates a set of fully editable *.bdf files

– Old “black box” option still available

– Minor limitations in the type or complexity of the Adams model• Models with non holonomic constraints

– Tool can be used from shell and from Adams/View

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Overview


– There is no need to modify the Adams model

– There is no need to change your processes

– Export job can be triggered at any operating point

– Export job is a high fidelity translation• Accurate kinematics• Matching eigenvalues (static cases only)

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Overview


– Users can use an optional configuration file to fine tune translation

– Current release exports to linear FEA codes

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Overview

• Example CAE process

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Motion analysis

FEA

translation

Create Adams model

Adams

NVH Optimization

• Overview

• Manual and Scripted Translation– Problems– Limitations



• Example

• Q&A

Agenda

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Manual and Scripted Translation

• Manual translation – Error prone– Time consuming (300 man hours for chassis prototype)– Inaccurate

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• Manual translation – Error prone– Time consuming (300 man hours for chassis prototype)– Inaccurate

• Scripted (user-written script)– Limitations. Cumbersome– Inaccurate

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• Why inaccurate?– Kinematic configuration is hard to reproduce

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– Eigenvalues computed by FEA code do not matcheigenvalues computed by Adams

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3.78

MBD FEA

7.23



– Eigenvalues computed by FEA code do not matcheigenvalues computed by Adams

– Structural coupling can be compromised

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• Why inaccurate?– A thorough theoretical study showed that

(1) High fidelity translations require mathematical informationnot available to users

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Example:

MOTION/1, JOINT=2, FU=DX(7,8)-DZ(11,23)

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(2) Linear FEA codes use linear constraint equations

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• Overview


• Theoretical Background– Overview– Governing equations in Adams– Governing equations in Nastran– Example


• Example

• Q&A

Agenda

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Theoretical Background

• Overview

– Automatic. The translation is another simulation job

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• Overview


Command:

SIMULATE/DYN, END=1.0, STEP=10LINEAR/EXPORT, TYPE=WHITEBOX, FILE=abc.nas

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• Overview


Adams/View:

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• Overview


Adams/View:

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• Overview


– Accurate. Exact kinematics

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• Overview



– Overcomes FEA limitations

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• Overview



– Overcomes FEA limitations

– Matching eigenvalues guaranteed for static cases

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• Basic idea

– Linearize the Adams model at the operating point

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• Basic idea


– Linearize the Adams model using Nastran coordinates

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• Basic idea



– Identify inertia elements, constraint equations and forces

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• Basic idea




– Will the equations assembled by Nastran match?

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• Basic idea




– Will the equations assembled by Nastran match?

– Need to examine the equations of motion in more detail

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• Governing equations in Adams– Simplified version

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Nastran coordinates

used!

Non linear equations!


• Governing equations in Adams (cont.)– Simplified version

– Partitioning

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• Governing equations in Adams (cont.)– Simplified version

– Partitioning

– Defining P

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This P is non linear!


• Governing equations in Adams (cont.)– Eliminating Lagrange multipliers

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– Differentiating constraints

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– Differentiating constraints

– Dependent accelerations

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• Governing equations in Adams (cont.)– Reduced ODE

• First and second derivatives of dependent states can be found from constraint equations

• Linearization done in terms of Nastran coordinates

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• Governing equations in Adams (cont.)– Reduced ODE

• First and second derivatives of dependent states can be found from constraint equations

• Linearization done in terms of Nastran coordinates

– Exact linearization of ODE. In variational form

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Linearized equations!


• Governing equations in Nastran– Partitioned equations of motion (linear)

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• Governing equations in Nastran (cont.) – Partitioned equations of motion (linear)

– Constraints (linear)

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• Governing equations in Nastran (cont.)– Partitioned equations of motion (linear)

– Constraints (linear)

– Defining P (this P is a constant)

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This P is a constant!


• Governing equations in Nastran (cont.)– Dependent accelerations

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– Reduced ODE

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– Reduced ODE

– Final form

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• Adams and Nastran equations

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Adams

Nastran

This P is a constant!

This P is non linear!


• Linearized Adams and Nastran equations

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Adams

Nastran

uuv

TTTT

fffMMvMMMMvMMMM

PPPPPPPPPPP

δδδδδδ

++=Ψ+++++++++

))(()()(

13

24132413

uvTT ffvMMMM δδδ PPPPP +=+++ )( 2413

P is now a constant!


• Linearized Adams and Nastran equations (cont.)

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Adams

Nastran

uvTT ffvMMMM δδδ PPPPP +=+++ )( 2413

uuv

TTTT

fffMMvMMMMvMMMM

PPPPPPPPPPP

δδδδδδ

++=Ψ+++++++++

))(()()(

13

24132413


• Eigensolutions will match only in static cases

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Adams

uuv

TTTT

fffMMvMMMMvMMMM

PPPPPPPPPPP

δδδδδδ

++=Ψ+++++++++

))(()()(

13

24132413

Zero in static configuration

Exported as DMIG


• Example Windmill– Model provided by NREL– Blades 63.5 m radius

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• Example Windmill (cont.)– Model provided by NREL– Blades 63.5 m radius

– Static simulation followed byeigensolution

– Model exported to Nastran

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• Example Windmill (cont.)– Exported model imported into

Patran

– Run SOL 107

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• Eigenvalue comparison

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• Eigenvalue comparison (cont.)

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• Overview



• Implementation Details– Inertial elements– Force elements– Constraints– Configuration file

• Example

• Q&A

Agenda

5/26/2011 55

Implementation Details

• Miscellaneous issues– By default, exports model for SOL 107

$ Force = N (newton)$ Time = s (second)$ UCF = 1000$ Export type: Whitebox$ Configuration file used: a2n_config.txt $$......1.......2.......3.......4.......5.......6.......7.......8.......SOL 107CENDTITLE = ADAMS2NASTRAN Export UtilitySUBTITLE = Adams operating point at time t=2.000000e+000ECHO = NONECMETHOD = 101

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• Miscellaneous issues (cont.)– Files are organized using three optional styles and included in main

exported file

$$-------------------------------------------------------------------------------$ Model$-------------------------------------------------------------------------------INCLUDE 'results/a2n_01_w.bdf.nas’INCLUDE 'results/a2n_01_w.bdf_DMIGS.bdf’INCLUDE 'results/a2n_01_w.bdf_GRAPHICS.bdf’$ENDDATA

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• Miscellaneous issues (cont.)– Every MARKER is exported as a GRID and a CORD2R:

PART/2MARKER/3

$ PART_2.MARKER_3CORD2R* 107 1.970978041D-11-3.519613300D+02* -3.938151830D-14 1.971010203D-11-3.519613300D+02 1.000000000D+00* 1.970903015D-11-3.529613300D+02-3.938151830D-14$ PART_2.MARKER_3GRID* 11 107 0.000000000E+00 0.000000000E+00* 0.000000000E+00 107

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Several numbering conventions


• Miscellaneous issues (cont.)– GRIDs are RBE2’d to the CM of the corresponding PART:

$ PART_2RBE2 7 3 123456 16 17 18 19 20

21 22 23 24 25 26 27 2829 30 31 32 33 34 35 36

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• Inertial elements– Adams model is linearized without constraint equations. This makes easier

to identify the inertia properties of all elements

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3

2

1

MM

M


• Inertial elements (cont.)– PART and POINT_MASS are translated as CONM2

$PART_1GRID* 1 5.563508327E-01 1.690524981E-01* -1.224646799E-16$$PART_1CONM2* 1 1 0 3.000000000E+00** 4.000000000E+00 2.220446049E-16 4.000000000E+00-3.790727274E-32* -1.702149213E-32 4.000000000E+00

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• Inertial elements (cont.)– FLEX_BODY are translated as SPOINT and three DMIG (M, K, and B)

$ FLEXIBLE_BEAMSPOINT 9999 THRU 10006$$ FLEXIBLE_BEAMDMIG MGMYFLX 0 6 2 0DMIG* MGMYFLX 9999 0* 9999 0 2.950000000D+00DMIG* MGMYFLX 10000 0* 10000 0 2.950000000D+00DMIG* MGMYFLX 10001 0* 10001 0 2.950000000D+00

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• Force elements– All forcing elements (GFORCE, VFORCE, SPRING, etc.) are translated as

CBUSH, PBUSH cards plus a residual DMIG

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VFORCE CBUSH

+ DMIG

uuv fff PP δδδ ++

• Force elements (cont.)– PBUSH properties and residual DMIG computation

Matrix is full and not symmetric !


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UKF u=

uK

Adams linearization

(damping not shown for clarity)

• Force elements (cont.)– PBUSH properties and residual DMIG


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?URKRUK pT

u =


Desired PBUSH propertymust be diagonal

Standard FEA transformation

• Force elements (cont.)– PBUSH properties and residual DMIG


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rpT

u DKRKR +=


Exported PBUSH property.Diagonal matrix

Residual DMIG.Residual DMIG could be zero!


• Force elements (cont.)– Typical output (residual DMIG not shown)

$ I: PART_1.MARKER_4, J: PART_9.MARKER_8$ Grid coincident with marker I but located on PART_9GRID* 10 1000004 0.000000000E+00 0.000000000E+00* 0.000000000E+00 1000004RBE2 11 9 123456 10$$SPRING_1PBUSH* 1000000 K 5.500000000E+01 1.424819004E-14** 1.221245327E-14 0.000000000E+00 0.000000000E+00 0.000000000E+00** B 0.000000000E+00 0.000000000E+00** 0.000000000E+00 0.000000000E+00 0.000000000E+00 0.000000000E+00$CORD2R* 10 1.112701665D+00-6.618950039D-01* -2.449293598D-16 1.112701665D+00-6.618950039D-01 1.000000000D+01* 1.054919334D+01 2.647580015D+00-2.449293598D-16$ I: PART_1.MARKER_4CBUSH 6000000 1000000 1000004 10 10

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• Force elements (cont.)– Residual DMIG can be split into a symmetric and a non symmetric parts

– Without splitting

SET 1 = KGt00001K2GG = 1

– With splitting

SET 1 = KGt00001SET 2 = KPt00001K2GG = 1K2PP = 2

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Symmetric residual

Non symmetric residual


• Force elements (cont.)– Residual non symmetric DMIG can be manually removed

from exported files

– Removal of non symmetric DMIG allows running SOL 103 and other solutions requiring symmetric matrices only

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• Constraint elements– Whenever possible, JOINT and JPRIM are exported using RJOINT

$----------------------------------- TrnJnt ------------------------------------$$JOINT_3000$ I: PART_3000.MARKER_3001, J:PART_9000.MARKER_9003GRID* 9010 1003001 0.000000000E+00 0.000000000E+00* 0.000000000E+00 1003001 $JOINT_3000RJOINT* 9010 1003001 9010 12456$$----------------------------------- FxdJnt ------------------------------------$$JOINT_1000$ I: PART_1000.MK_REF1, J:PART_9000.MARKER_9001RJOINT* 9011 1001001 1009001 123456

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• Constraint elements (cont.)– Whenever possible, JOINT and JPRIM are exported using RJOINT

– UNIVERSAL and HOOKE are exported as combination of RJOINT

– Other constraints (GCON, MOTION, etc.) are exported as MPC cards

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• Constraint elements (cont.)– Constraint MPC are obtained by computing

– Matrix is exported as MPC

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• Differential elements– DIFF, LSE, GSE, and TFSISO are exported as SPOINT and DMIG

– Given

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),,(0)(

),(

tqzhzq

zqfqM Tq

==Φ

=Φ+

λDIFF, LSE, GSETFSISO


• Differential elements (cont.)– Linearization finds

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Exported as DMIG

=

zqq

AAAAQP

I

zqq

432

1

00


• Graphic elements– Alpha version

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CONM2, DMIG, GRID, SPOINT


• Graphic elements (cont.)– Current version

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• Graphic elements (cont.)– All GRAPHIC elements are exported as constrained CQUAD4 or CTRIA3

elements with zero mass

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• Graphic elements (cont.)– All GRAPHIC elements are exported as constrained CQUAD4 or CTRIA3

elements with zero mass

– FLEX_BODY graphics are exported fixed in space (to be enhanced)

– All exported graphics can be removed before starting Nastran solutions

– Debugging tool. Does not affect results.

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• Configuration file (cont.)– An optional configuration file can be supplied

LINEAR/EXPORT, TYPE=WHITEBOX, FILE=abc.nas, CONFIG=myconfig.txt

– Configuration file is a plain text file with directives

– Allow fine tuning the export process

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• Configuration file (cont.)– Users may:

Modify numbering schemes, choose solution number, modify defaults, create channels for FRF solution in Nastran, remove damping, etc.

– Easy to add new directives

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• Configuration file (cont.)– Example configuration

$ Setting FRF analysis for SOL 108

actuator_swept_sine {phase_angle = 90 magnitude = 77name = test01

}

force_input_channel {name = f1marker_id = 3001dof = ryactuator_name = test01

}

displacement_output_channel {name = d1marker_name = model.PART_1000.MK_REF1

}

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Comments


• Configuration file (cont.)– Example configuration (cont.)

frequency_response_subcase {number = 101input_channel_names = f1output_channel_names = d1

}

export_all_markers = nompc_set = 77grid_offset = 1spoint_offset = 9999solution_number = 108forces_dmig_name = ADMS1differentials_dmig_name = ZZ3matrix_entry_zero_tolerance = 1.e-8

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• Overview




• Example– Full chassis model

• Q&A

Agenda

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Example

• Chassis model prototype (courtesy of BMW Group)

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Example

• Exported model loaded in SimXpert

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Example

• Eigenvalues comparison

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Chassis - Frequency error vs. Mode number

-0.2000

0.0000

0.2000

0.4000

0.6000

0.8000

1.0000

1.2000

1.4000

1.6000

0 50 100 150 200 250 300Mode number

% E

rror

Example

• Observations– Matching eigenvalues for static cases only

– FEA model has exactly the same kinematic configuration as in Adams

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• Overview




• Examples

• Q&A– Acknowledgments– Q&A

Agenda

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Q&A

• Acknowledgments

– MSC.Software Italy

– Dr. Daniel Heiserer (BMW Group)

– MSC.Software Germany

5/26/2011 89

Download - Adams-to-Nastran - MSC Softwarepages.mscsoftware.com/rs/mscsoftware/images/AdamsUser...Overview • There is a need for model translation from Adams to FEA 5/26/2011 4 Multibody Dynamics

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