a modern parameterized process for brake-squeal · pdf filea modern parameterized process for...

A Modern Parameterized Process for Brake-Squeal Simulation

Eurobrake 2012 Dresden

1Weiland, Stefan, 2Moosrainer, Marold1TRW Automotive, Germany, 2CADFEM GmbH, Germany

Eurobrake 2012: Parameterized Simulation Process

Agenda

§ Introduction

§ NVH Simulation History @ TRW

§ Requirements on Process and Simulation Tools

§ ANSYS Features and Developments

§ ANSYS Simulation Driven Product Development (SDPD)

§ Summary / Outlook

1


Origin of Brake Squeal

§ physical: energy exchangemechanism triggered by twocoupled modes due to friction§ numerical: unsymmetric stiffness

matrix due to friction (red) proneto instability à complex eig.values

2

Energy DeflectionDynamic System

Triggerµ

v


NVH Simulation History @ TRW

3

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Methodology development

with NASTRAN

TRW collaboration with ABAQUS for CEA

1st pilot projects

complex eigenvalue analyses in all projects

Benchmark with ANSYS

Complex Eigenvalue Analyses = CEA

Projects withANSYS


Main Keypoints in Daily Project Work

§ Efficiency

§ Result Quality

§ Sensitivity / Robustness Analyses

4


1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

2 3 5 6 7 9 14 19 1827

35

56 5360 62Brakes w CEA support

Efficiency: Modeling

5

Model PreparationTime perBrake

1997 2011 1997 2011

Model Complexity /Number of Axle Variationsper Brake

TOTAL modeling time is increasing significantly

1997 2011

Total time for Model Preparation

Time per Brakex

Complexity x

Number of Brakes=

Total time for Model Preparation


Result Quality: Analysis Solution Sequences

6

FE modeling

Model tuning (couplings and

springs)

Linear complex modal

analyses

pure linear complex eigenvalue analyses

FE modeling

Model tuning (contacts,hydraulic

pressure, rotor rotation)

Transfer ofstatic results to linear coupling and stiffness conditions

Solution(quasi static)

Linear complex modal

analyses

non-linear static load case plus linear complex eigenvalue analyses

Both approaches are necessary.


Result Quality: Pros / Cons of Solution Sequences

7

Pure linear CEA

§ Disadvantages§ High modeling effort§ Detailed manual coupling

necessary to adjust modeling

§ Advantages§ Fast analyses (CPU)§ Easy model parameter

manipulation

Full Non-linear (static load case plus linear CEA)

§ Disadvantages§ Upfront non-linear analyses is

required à additional load case§ Limited possibilities for model

manipulation§ Convergence issues

§ Advantages§ Non-conformal meshes § Pre-stressed CEA

Easy switch between both approaches is required.


Sensitivity / Robustness Analyses

§ Load variation due to different braking situations § Pressure variation§ Component interaction variation§ Friction value variation§ Material property variation due to temperature

§ Geometry and material variation due to manufacturing process§ Geometrical tolerances due to casting process§ Material variation due to casting process§ Lining material variation§ Shim material variation

8


Required Features to Improve NVH Simulation Process

§ Efficiency§ Speed-up of Model Preparation§ Speed-up of Solution Time§ Easy Setup of Multiple Runs§ Geometry Based Model Manipulation

§ Result Quality§ Combination of Linear and Non-Linear Approach§ Different Restart Techniques

§ Sensitivity / Robustness Analyses§ Easy to use Variation Studies § Sensitivity Studies (incl. Post-Processing)

9


ANSYS Features / Process

§ Solver§ robust and efficient element

technology, non-lin. Contact, etc.

10

SDPD: SDPD: SSimulation imulation DDrivenriven PProductroduct DDevelopmentevelopment

§ Simulation Process

Para-meters

CAD

Mesh

Set up

Solver

Post

Opti-mize


Efficiency – Modeling: CAD – Meshing – Setup

§ Initial Model Preparation time: 5 days§ New Approach:§ Parameterized CAD to mesh connection

(Bi-Directional CAD Interface)§ Robust TET elements with midside nodes

ready for nonlinear material & contact § Intuitive defeaturing & model preparation § Automatic Mesh, joints, model setup

total 2 days

11

277000 nodes, 156000 elem


ANSYS Brake Squeal Solution Sequences

• Include pre-stress and rotational velocity• Most accurate & most expensive method!• Nonlinear equilibrium iterations• à CPU ressources see chart on next slides

• Include pre-stress and rotational velocity• Most accurate & most expensive method!• Nonlinear equilibrium iterations• à CPU ressources see chart on next slides

Full Nonlinear Analysis

• Includes the pre-stress effects (contact pressure, ..)• Does not need equilibrium iterations for the

rotational velocity• Less expensive than full nonlinear analysis

• Includes the pre-stress effects (contact pressure, ..)• Does not need equilibrium iterations for the

rotational velocity• Less expensive than full nonlinear analysis

Partial Nonlinear Analysis

• Assumes stress stiffening effects are not significant• Convergence questions are irrelevant• Contact stiffness based on initial contact status• Fast run times allow for large DOE studies

• Assumes stress stiffening effects are not significant• Convergence questions are irrelevant• Contact stiffness based on initial contact status• Fast run times allow for large DOE studies

Linear Analysis

Sequence 12


Classical Approach§ Discrete 2 node (springs) elements are used to

provide friction stiffness § Drawbacks of classical approach (node to node)→Requires matching nodes at the sliding interface→Time consuming→Impractical for geometrical parametric studies

Solver: Linear Approach – Direct modeling

13

Conformal mesh:à node-to-node

springs

Non-conformal mesh: à contact

elements

ANSYS opportunities


1. Pre-stressed static analysis à to establish contact between the pads and disc

2. Forced frictional sliding between pads and disc à to generate non symmetric stiffness matrix

3. Pre-stressed modal analysis à to calculate the modal subspaceà to generate complex eigen frequencies

à Restart Points between allow almost any combination!

Solver: Full Nonlinear Approach

14


Solver: Efficiency Driver – Restart Technique

§ Static Restart:§ Reuse of converged non-linear static results (e.g. pressure variation study)

§ Modal Restart§ Reuse of modal subspace for modified complex mode analysis (e.g. friction

sensitivity study)

§ Linear Perturbation§ Stiffness matrix manipulation before complex mode analysis (e.g. material

parameter variation)

15


0%

20%

40%

60%

80%

100%

120%

Full nonlinear Partial nonlinear Linear

Elapsed Time: Brake Squeal Analysis Sequences

Complex Modes + Expansion [%]Normal Modes [%]

Statics Contact [%]

Solver: ANSYS Solution Sequences – Solution Time

16


Solver: Complex Modal Analysis Result

17

Check for positive real parts of the complex eigenvalues. Those modes are prone to squealing.


ANSYS Workflow for Parameterized Brake Squeal Simulation

SDPD: Project Schematic – Parameter Variation

1. Material library2. Parameterized geometry import via bidirektional interface3. Nonlinear prestress (large deformation + nonlinear contact)4. Complex modal analysis 5. Parameters close the loop for SDPD:

design variants, sensitivity, optimization, robust design with optiSLang

2

3 4

5

1

18

Full Nonlinear,Partial Nonlinear,Linear Analysis


SDPD: Parameter Definition

The following parameters have been investigated in this case§ Geometry parameters:

Ribs position and height

§ Material Parameter: Brake Pad Modulus Ez in the thickness direction

§ Coefficient of friction between brake pad and disc

19

Gif Animation


§ Parameter Variation Study§ many design points: do it yourself in the ANSYS spreadsheet

SDPD: Parameter Variation / Robustness Study

20

§ Sensitivity and Robustness Study§ Dig deeper with embedded optiSLang: Sensitivity studies, optimization,

robust design, ...


SDPD – Parameter Variation: Geometry Parameters

21

Influence of parameter ribs_height with ribs_position=-2

Gif Animation

0

0.5

1

1.5

2

2.5

1 2 3 4 5 6 7 8

Neg

ativ

e D

ampi

ng [%

]

Frequency [kHz]

Instability ChartParameter: Ribs Height in Inner Position

ribs_height=+0mmribs_height=+1mmribs_height=+2mm

Significant improvement of low frequency noise by rib height


1st squeal frequency shows a maximum for a large rib (height) and small friction coefficient (~3500 Hz)

Rib (height) and friction coefficient have the strongest impact on the 1st squeal frequency

SDPD – Sensitivity Study: optiSLang

22


• Complex Eigen solve• Animate: Complex Mode Shape

• Contact Status at Pads

• Provides for sliding contact with friction

• No match mesh needed

CAD Mesh & Connection

Setup & solver

Post Processing

Load variation studye.g. Friction sensitivity studye.g. Pressure variation study

Material property variation studye.g. Lining sensitivity study

Geometry variation study e.g. Disc design study23

Bi-Directional CAD Connectivity

• Automated Contact Detection

• Automated Meshing

• Root locus plots• Correlation of modes

• List Strain Energy per component per mode• Can Include Squeal

and Contact damping

• Sliding velocity dependent Friction

• Flexibility to use Linear & Non-linear solver capabilities

Summary: ANSYS WB Baseline Process


Summary: Required Features

§ Efficiency§ Speed-up of Model Preparation: 5 days à 2 days§ Speed-up of Solution Time: QRDAMP / CEA Solver (down to 30%)§ Easy Setup of Multiple Runs: Parameter Loops in GUI§ Geometry Based Model Manipulation: Bi-Directional CAD Interface

§ Result Quality§ Combination of Linear and Non-Linear Approach:

Linear Approach w Non-Coincident Nodes§ Different Restart Techniques:

Static- / Modal-Restart and Linear Perturbation

§ Sensitivity / Robustness Analyses§ Easy to use Variation Studies: ANSYS Parameter Spreadsheet § Sensitivity Studies (incl. Post-Processing): Embedded optiSLang

24


Thank you for your attention!

Don‘t hesitate to contact :

Dr.-Ing. Stefan WeilandTRW [email protected]

Dr.-Ing. Marold MoosrainerCADFEM [email protected]

25

Also refer toANSYS @ EKSBrake Squeal SimulationReference ProblemsMarold Moosrainer, CADFEM GmbH18.05.2011, Park Hotel Stuttgart

mailto:[email protected]

mailto:[email protected]

a modern parameterized process for brake-squeal · pdf filea modern parameterized process for...

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