a modern parameterized process for brake-squeal · pdf filea modern parameterized process for...
TRANSCRIPT
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
Main Keypoints in Daily Project Work
§ Efficiency
§ Result Quality
§ Sensitivity / Robustness Analyses
4
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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.
Eurobrake 2012: Parameterized Simulation Process
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.
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
Solver: Complex Modal Analysis Result
17
Check for positive real parts of the complex eigenvalues. Those modes are prone to squealing.
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
§ 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, ...
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
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
Eurobrake 2012: Parameterized Simulation Process
• 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
Eurobrake 2012: Parameterized Simulation 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
Eurobrake 2012: Parameterized Simulation Process
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