2014 European Altair Technology Conference June 24-26, 2014 | Munich, Germany Join, Contribute, Exchange Brake Noise Simulation using Multi-Body Simulation Analysis Dr. Armin Veitl Benjamin Leblanc See full agenda: www.altairhtc.com/europe
Sep 13, 2014
2014 European Altair Technology Conference
June 24-26, 2014 | Munich, Germany
Join, Contribute, Exchange Brake Noise Simulation
using Multi-Body Simulation Analysis
Dr. Armin Veitl
Benjamin Leblanc
See full agenda: www.altairhtc.com/europe
Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Agenda
• Motivation
• Self excited system
• Tribology effects
• Contact modeling
• Model build-up
• Simulation setting with a driving rotation
• Results & discussion
• Planed enhancements
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Motivation
• The level of noise heard within a vehicle’s interior can drastically impact
a passenger’s comfort. Brake noises can give the customer a poor
impression of product quality. Within the C.A.E. industry, the study of
mode coupling instability by the use of F.E.M. and modal complex
analysis, is widespread to reduce those phenomenon.
• An complementary method is presented in this paper where brake noise
issues are predicted by the use of a time transient integration using
multi-body system analysis
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Brake - Vibration and Noise
Judder
Moan
Groan
Low Frequency
Squealing
High Frequency
Squealing
10 100 500 1k 3-4k 10k
Type o
f oscill
ation
forc
ed
s
elf-e
xcited
Frequency [Hz]
Low frequency Effects
High frequency
Effects
Usual application
field for MBD
Domain that we
intend to cover
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Brake - Vibration and Noise
Brake Squeal Issue
CAE model – CAE Labor
Differential Equation of motion
Linearization and Instability
Analysis
Frequency Domain
Results:
Frequency of instability
complex mode shape
Integration of the differential
equation system
Time Domain
Results:
Analyze by Fourier in frequency
domain
time shape animation
Problem Identification /
Engineering a solution
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Self excited system
• Phenomena that leads from
a steady state to an
oscillatory state without
external oscillatory excitation
• Comparison to aero-elasticity
“Limit Cycle Oscillations (LCO)” Excitation system pad ↔ disc (stick-slip effect)
Resonant system suspension
Input: - vehicle speed - brake pressure - friction law
Output: - resonance phenomena - brake noise
Feedback loop: - suspension vibration
self-excited system
LCO pictures source: Wind tunnel analysis of separated aerodynamcis leading to different types of torsional flutter in bluff-bodies,
T. Andrianne – Université of Liège
Animation Gif source: AcuSolve Example – Altair Engineering
constant flow
section from a beam
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Tribology effects
• Tribology is the science of interacting surfaces in relative motion
pictures source: Thèse: Apport des analyses numériques temporelle et fréquentuelle dans l´étude des instabilités de contact, A.Meziane
Animation Gif source: Arnol'd tongues arising from a grazing-sliding bifurcation of a piecewise-smooth system, Szalai, R; Osinga, HM, University of Bristol
self-oscillations that appears due to contact can be
classified in 2 categories:
• stick-slip vibration
• quasi-harmonic vibration
stick-slip vibration
quasi-harmonic vibration
Normal force on pad
Friction force on pad
friction law example
Ft = µ(v).Fn
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Contact modeling
• Friction Law
• Flexibility of the disk
• Flexible surface:
• a marker can slide along the whole
surface
• surface deformation is interpolated
between reference points
• A modal basis provides the stiffness of
the surface. Static correction modes
are not required for the surface
• Static correction modes only used for
the connection to the strut
…
mode 7
mode 8
mode 9
mode 10
mode 11
mode 12
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Contact modeling
• Friction Law
• Flexibility of the disk
• User-Subroutine
• Compute normal force at contact point
• Compute friction force at this point
Python Script: no compilation required
Call of the User-Subroutine in MotionSolve
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Model build-up
Mac-pherson axle system
Strut idealized as one flexible body
control arm
as one flexible body
…
… toe link modeled with a poly-beam
connected with a ball and a constant
velocity joints
All bushings parameterized with
a dataset
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Model build-up
floating brake caliper system
Brake caliper as flexible body
Brake bracket as flexible body
…
…
Brake piston as a rigid body
Brake pads as flexible too
Disk and hub as one flexible body
and
modeled with deformable surface
as shown on a previous slide
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Simulation setting with a driving rotation
• Virtual actuator
• 2 degree of freedom
• Impose rotation
• Constant velocity
• 2 [km/h]
• brake disk free to move
in other directions
• Brake pressure
• Constant 20 [bar]
• Simulation settings
• Transient : 2 [sec]
• Integrator : DSTIFF
constant velocity joint
constant velocity joint
revolute joint attached to GROUND
motion boundary condition
translational joint attached to DISK
Body 1
Body 2
Body 3
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The model in HyperWorks
model database structured with a browser
All contact instance included in is own system
Dataset to manage input parameter
Axle and Brake separated into 2 systems to enable easy model update
Virtual system to rotate wheel
GUI entry to manage simulation variants
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Results & discussion
• Relative speed at contact
point between pad and
disk surface
• Stick-slip characteristic
• increasing area until
constant amplitude
• Stick area
• Slip area
• “quasi-harmonique”
ST
ICK
ST
ICK
ST
ICK
SL
IP
SL
IP
SL
IP
SL
IP
transition
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Results & discussion
Results animation : friction directions are changing when system start vibrating
the displayed forces are applied on pad
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Results & discussion
Results animation : friction directions are changing over time, but system behaves quasi-harmonic
the displayed forces are applied on pad
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Results & discussion
• Acceleration time history can be filtered by Fourier and displayed in water fall
diagram in a frequency range from [0 – 4000 Hz]
• Critical frequencies appear in the diagram and can be compared to component
normal frequency or complex modes 1 3 2
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Results & discussion
Results animation : scale 500 in deformation, deformation shapes can be compared to normal modes
or to complex modes analysis
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Results & discussion
• Brake Noise Simulation: Resume of the CAE-Knowledge
• Finite element modal complex
• Multi-body
FFT‘s
1
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Results & discussion
• Brake Noise Simulation: Resume of the CAE-Knowledge
• Finite element modal complex
• Multi-body
Instable mode animation with FE modal
complex (Frequency domain)
Time animation with Multi-body Simulation
1
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Process Implementation
pictures source: http://www.ganttproject.biz
GanttProject is a cross-platform desktop tool for project scheduling and management.
• Implementation in vehicle development
• build on existing CAE information: no double effort to invest
• win twice more information on the same project
• CAE tasks can be performed in parallel and validate each other
• increase CAE predictivity / reporting value from CAE Labor
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Results & discussion
• Summary
• multi-body simulation method enable self excited system simulation
• “Stick-Slip” characteristics clearly shown
• frequency responses appear in the expected range [0Hz – 4000 Hz]
• the method matured for vehicle development
• enable comparison with modal complex analyze / reciprocal validation of CAE
• Planed enhancements
• Post-processing tools to more easily identify the critical peak
• Automation to enable better model build-up