adams-to-nastran - msc • there is a need for model translation from adams to fea 5/26/2011 4...

Download Adams-to-Nastran - MSC   • There is a need for model translation from Adams to FEA 5/26/2011 4 Multibody Dynamics System model Adams Finite Element Analysis model FEA ... • Introducing Adams -to-Nastran – Performs an automatic model

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  • 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

    Manual and Scripted Translation

    Theoretical Background

    Implementation Details

    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++

    5/26/2011 5

  • 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

    5/26/2011 6

  • Overview

    Introducing Adams-to-Nastran (cont.)

    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)

    5/26/2011 7

  • Overview

    Introducing Adams-to-Nastran (cont.)

    Users can use an optional configuration file to fine tune translation

    Current release exports to linear FEA codes

    5/26/2011 8

  • Overview

    Example CAE process

    5/26/2011 9

    Motion analysis

    FEA

    translation

    Create Adams model

    Adams

    NVH Optimization

  • Overview

    Manual and Scripted Translation Problems Limitations

    Theoretical Background

    Implementation Details

    Example

    Q&A

    Agenda

    5/26/2011 10

  • Manual and Scripted Translation

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

    5/26/2011 11

  • Manual and Scripted Translation

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

    Scripted (user-written script) Limitations. Cumbersome Inaccurate

    5/26/2011 12

  • Manual and Scripted Translation

    Why inaccurate? Kinematic configuration is hard to reproduce

    5/26/2011 13

  • Manual and Scripted Translation

    Why inaccurate? Kinematic configuration is hard to reproduce

    Eigenvalues computed by FEA code do not matcheigenvalues computed by Adams

    5/26/2011 14

    3.78

    MBD FEA

    7.23

  • Manual and Scripted Translation

    Why inaccurate? Kinematic configuration is hard to reproduce

    Eigenvalues computed by FEA code do not matcheigenvalues computed by Adams

    Structural coupling can be compromised

    5/26/2011 15

  • Manual and Scripted Translation

    Why inaccurate? A thorough theoretical study showed that

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

    5/26/2011 16

  • Manual and Scripted Translation

    Why inaccurate? A thorough theoretical study showed that

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

    Example:

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

    5/26/2011 17

  • Manual and Scripted Translation

    Why inaccurate? A thorough theoretical study showed that

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

    (2) Linear FEA codes use linear constraint equations

    5/26/2011 18

  • Overview

    Manual and Scripted Translation

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

    Implementation Details

    Example

    Q&A

    Agenda

    5/26/2011 19

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    5/26/2011 20

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    Command:

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

    5/26/2011 21

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    Adams/View:

    5/26/2011 22

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    Adams/View:

    5/26/2011 23

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    Accurate. Exact kinematics

    5/26/2011 24

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    Accurate. Exact kinematics

    Overcomes FEA limitations

    5/26/2011 25

  • Theoretical Background

    Overview

    Automatic. The translation is another simulation job

    Accurate. Exact kinematics

    Overcomes FEA limitations

    Matching eigenvalues guaranteed for static cases

    5/26/2011 26

  • Theoretical Background

    Basic idea

    Linearize the Adams model at the operating point

    5/26/2011 27

  • Theoretical Background

    Basic idea

    Linearize the Adams model at the operating point

    Linearize the Adams model using Nastran coordinates

    5/26/2011 28

  • Theoretical Background

    Basic idea

    Linearize the Adams model at the operating point

    Linearize the Adams model using Nastran coordinates

    Identify inertia elements, constraint equations and forces

    5/26/2011 29

  • Theoretical Background

    Basic idea

    Linearize the Adams model at the operating point

    Linearize the Adams model using Nastran coordinates

    Identify inertia elements, constraint equations and forces

    Will the equations assembled by Nastran match?

    5/26/2011 30

  • Theoretical Background

    Basic idea

    Linearize the Adams model at the operating point

    Linearize the Adams model using Nastran coordinates

    Identify inertia elements, constraint equations and forces

    Will the equations assembled by Nastran match?

    Need to examine the equations of motion in more detail

    5/26/2011 31

  • Theoretical Background

    Governing equations in Adams Simplified version

    5/26/2011 32

    Nastran coordinates

    used!

    Non linear equations!

  • Theoretical Background

    Governing equations in Adams (cont.) Simplified version

    Partitioning

    5/26/2011 33

  • Theoretical Background

    Governing equations in Adams (cont.) Simplified version

    Partitioning

    Defining P

    5/26/2011 34

    This P is non linear!

  • Theoretical Background

    Governing equations in Adams (cont.) Eliminating Lagrange multipliers

    5/26/2011 35

    Non linear equations!

  • Theoretical Background

    Governing equations in Adams (cont.) Eliminating Lagrange multipliers

    Differentiating constraints

    5/26/2011 36

    Non linear equations!

  • Theoretical Background

    Governing equations in Adams (cont.) Eliminating Lagrange multipliers

    Differentiating constraints

    Dependent accelerations

    5/26/2011 37

  • Theoretical Background

    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

    5/26/2011 38

  • Theoretical Background

    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

    5/26/2011 39

    Linearized equations!

  • Theoretical Background

    Governing equations in Nastran Partitioned equations of motion (linear)

    5/26/2011 40

  • Theoretical Background

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

    Constraints (linear)

    5/26/2011 41

  • Theoretical Background

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

    Constraints (linear)

    Defining P (this P is a constant)

    5/26/2011 42

    This P is a constant!

  • Theoretical Background

    Governing equations in Nastran (cont.) Dependent accelerations

    5/26/2011 43

  • Theoretical Background

    Governing equations in Nastran (cont.) Dependent accelerations

    Reduced ODE

    5/26/2011 44

  • Theoretical Background

    Governing equations in Nastran (cont.) Dependent accelerations

    Reduced ODE

    Final form

    5/26/2011 45

  • Theoretical Background

    Adams and Nastran equations

    5/26/2011 46

    Adams

    Nastran

    This P is a constant!

    This P is non linear!

  • Theoretical Background

    Linearized Adams and Nastran equations

    5/26/2011 47

    Adams

    Nastran

    uuv

    TTTT

    fffMMvMMMMvMMMM

    PPPPPPPPPPP

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