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© VIRTUAL VEHICLE
VIRTUAL VEHICLE Research Center is funded within the COMET – Competence Centers for Excellent Technologies – programme by the Austrian Federal Ministry for Transport, Innovation and
Technology (BMVIT), the Federal Ministry for Digital and Economic Affairs (BMDW), the Austrian Research Promotion Agency (FFG), the province of Styria and the Styrian Business Promotion
Agency (SFG). The COMET programme is administrated by FFG.
A patch transfer function approach for vibro-acoustic
analysis with poroelastic materials
PBNv2 – First Public Technical Course
INSA Lyon, November 28-29, 2018
Jan Rejlek, Eugène Nijman, Markus Polanz, Nicola Contartese
© VIRTUAL VEHICLE
Agenda
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 2
▪ Motivation for automotive NVH
▪ NVH complexity & challenges
▪ Automotive poroelastic materials (PEM)
▪ State-of-the-art in numerical modelling of PEM
▪ Patch transfer function (PTF) approach
▪ PTF trim characterisation
▪ Application examples
▪ Conclusions and outlook
© VIRTUAL VEHICLE
Noise is a societal challenge
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 3
…noise
▪ fastest growing pollutant in Europe
▪ traffic-related noise accounts for over 1 million healthy years of life lost in EU annually1
▪ European Parliament has approved a law to reduce the limit pass-by noise levels via a
three-phase plan, which will apply from 20162
1 WHO-JRC, 2011; Report on “Burden of disease from environmental noise”, ISBN: 978 92 890 0229 5; http://www.who.int/quantifying_ehimpacts/publications/e94888/en/2 EU Press Release IP/14/363, http://europa.eu/rapid/press-release_IP-14-363_en.htm, April 2nd, 2014
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Motivation for automotive NVH
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 4
“noise policies”
▪ tightening of legal noise regulations
“competitive nature of market”
▪ growing customers` expectations
▪ short “development-product to market” phase
▪ NVH is becomes a brand differentiator
“novel challenges”
▪ conflicting design criteria
• lightweight design
• alternative propulsion
• downsizing/ downspeeding
▪ NVH complexity
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The NVH complexity
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 5
▪ common platforms/modules
▪ vehicle derivates
▪ “strong backbone”
Image courtesy of Renault/Nissan
Image courtesy of Volkswagen AG
PhD track of
Nicola Contartese
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Current trends in automotive industry
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 6
https://en.wikipedia.org/wiki/List_of_BMW_vehicles
→ increased number of car series and/or derivates
→ shortening of product development phase
→ new propulsion architectures (BEV, HEV, PHEV)
“1996”
7 product lines
~6 yrs development time
“2016”
26 product lines
excl. Mini marque (9)
~3 yrs development time
Images courtesy wikipedia.org
BMW AG
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Role of NVH in vehicle development process
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 7
▪ inherent parallel nature
▪ multitude of functional attributes for different components
▪ highly competitive environment (cost, weight, package constraints)
▪ outsourcing/ sub-contracting
▪ target setting/achieving procedure
▪ iterative process (mule, prototype, pre-series)
▪ NVH driven by details
▪ application of (reliable) NVH CAE tolls still limited
▪ key role of NVH testing
→ hybrid methods could enhance
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Automotive sound packages
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 8
▪ Sound packages: are made up from a combination of materials, notably
▪ porous materials (foams, fibers, felts, carpets, porous films, fabrics)
▪ damping materials
▪ limp and elastic (solid) layers
▪ The goal: to control noise (interior/exterior)
▪ Drawback
▪ added mass (sound package on average passenger car ~80 kg)
▪ packaging problems
▪ costs
sound insulation
absorption
structural damping (baseline drawing courtesy of BMW AG)
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Physics behind
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 9
image courtesy of BWF Envirotec
image courtesy of Université de Sherbrooke
▪ Porous materials
▪ Two phases: solid and fluid
▪ Elastic coupling
▪ Visco-inertial coupling
▪ What do they do ?
→ Transform acoustic energy into heat
▪ How do they dissipate energy?
▪ viscous effect
▪ thermal effect
▪ structural damping
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State-of-the-art in modelling of poroelastic
materials
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 10
1. Equivalent mechanical models
2. Empirical models (Delaney-Bazley)
3. Transfer-Matrix-Method (semi-analytical, locally-reacting)
4. Microstructural models (homogenisation, Biot theory)
▪ State-of-the-art in vibro-acoustic modelling of poroelastic materials
→ full FE Biot-based approach
▪ detailed description, but
▪ computationally expensive
▪ need for Biot parameters
→ state-of-the-use (?)
Accuracy
Assumptions
Monet-Descombey Julien, Zhang Charles, Hamdi Mohamed-Ali, A Partition Finite Element Method Allowing
the Calculation of the Vibro-Acoustic Response of Fully Trimmed Vehicles in Medium Frequency Range, In
proceedings of INTERNOISE 2008, 26-29 October, Shanghai, China.
image courtesy of BASF
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Novel approach to PEM characterisation
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 11
Development of a novel methodology to describe vibro-
acoustic behaviour of sound insulation materials
▪ dynamics described in terms of surface impedance rather than material micro-
models
▪ non-contact measurement of surface impedance
▪ methodology implemented in a sub-structuring coupling scheme to account
for interaction with structure and fluid
Objective
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Patch Transfer Function (PTF) approach
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 12
▪ sub-structuring into separate physical domains
▪ determination of surface impedance
▪ coupling at common interfaces
Key advantage: the trim is characterised on a macroscopic level
image courtesy of AUDI AG
image courtesy of BASF and Autoneum
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Patch Transfer Function (PTF) approach
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 13
Limitation: wavelength > double the patch dimension
Poroelastic
domain
Acoustic cavity
StructurePTF
PTF
Ouisse M., Maxit L., Cacciolati C., and Guyader J., “Patch transfer functions as a tool to couple linear acoustic problems”.
Journal of Vibration and Acoustics, 127:458-466, October 2005, doi:10.1115/1.2013302.
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Spatial averaging of field variables
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 14
▪ Fields variables (p,v) phase averaged over each patch
▪ Blocked impedance (for low-impedance “soft” materials (air or foam))
is the pressure on patch i when patch j is excited by uniform velocity and all
other patches k are blocked (v=0).
▪ Free mobility (for high-impedance “hard” materials (plate))
is the velocity on patch i when patch j is excited by uniform pressure and all
other patches k are free (p=0).
0=
=
jkpj
iij
p
vY
0=
=
jkvj
iij
v
pZ
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Validation example
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 15
Cavity-backed plate with liner
Practical implementation
▪ 1.7 x 0.8 x 1 m
▪ rigid cavity (5 faces)
▪ 2 mm steel plate (clamped)
▪ Basotect® TG melamine foam t = 42 mm
Melamine foam sample
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Validation example
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 16
cavity SPL prediction
▪ Interfaces discretisation: 40cm patches → N=8
▪ Assessment of the impedance/mobility matrices:
▪ Structure characterisation → experimental / numerical
▪ TRIM characterisation → experimental / numerical
▪ Cavity charcterisation → analytical
F
TZ12
TZ2
CZ2
𝑧𝐶
Cp
TZ1SY𝑦𝐹
Cavity
TrimPlate
22 ,vp
11,vp
=
+−
−
−
0
0
0
0
2
1
1
2212
121
Fy
v
v
p
ZZZ
IY
ZZIF
CTT
S
TT
2)( vzp TCC =
2
1
Goal
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Sub-domain characterisation
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 17
• Steel plate characterisation:
− Uniform pressure patch excitation approximated by superposition of point forces
− Fluid loading negligible
• Cavity characterisation:
− Rectangular volume with rigid walls → analytical model (modal summation)
[Air-borne Sound Source Characterisation by Patch Impedance Approach, G. Pavic, Journal of Sound and Vibration, 2010]
• Trim characterisation?
− direct measurement of p at interfaces provided that v=0
− measurement of both p,u and assessment of Z by
inverse technique (no blocked conditions required)
0=
=
jkpj
iij
p
vY
x
0=
=
jkvj
iij
v
pZ
0=
=
jkvj
iij
v
pZ
0=
=
jkvj
iij
v
pZ
© VIRTUAL VEHICLE
PTF trim - direct approach
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 18
▪ Skeleton and fluid motion blocked at the interface
▪ Imposed v, direct measurement of p
▪ Pressure microphones → fluid pressure, skeleton motion neglected
▪ Similar setup as Dynamic stiffness (ISO9052-1)
surface input Z - surface transfer Z
22 ,vp11,vp
patch 1 patch 2
0=
=
jkvj
iij
v
pZ
Assessment of the blocked impedance of a melamine sample
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PTF trim - direct approach
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 19
Practical implementation
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PTF trim - indirect approach
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 20
▪ Skeleton and fluid motion blocked at the bottom interface
▪ Skeleton and fluid motion free at the top interface
▪ Imposed v, direct measurement of both p,v → p-u probes
▪ Assessment of blocked impedance by inversion
▪ Efficient fluid excitation, weak skeleton excitation
A B
1 2
TRIM specimenspeaker positionarray position
rigid ground (v=0)
=
2
1
2
1
2221
1211
p
p
v
v
ZZ
ZZ
surface input Z
surface transfer Z
22 ,vp11,vp
patch 1 patch 2
0=
=
jkvj
iij
v
pZ
Assessment of the blocked impedance of a melamine sample
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PTF trim - indirect approach
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 21
Practical implementation
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▪ Continuity conditions at interfaces
▪ Eliminate v2, determination of Zm
▪ Applicable to any surface impedance measurement
1
3
2
Airgap correction
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 22
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Correction for the impedance of the air layer between the specimen surface and the
actual measurement plane
Low freq. → mass governed side walls radiation
High freq. → stiffness of the airgap
• Assumption: p does not change along the air layer
thickness
• Air slit impedance
1−= vpZa
d
0 100 200 300 400 500 600 700 800 900 100040
50
60
70
80
90
L [
dB
]
0 100 200 300 400 500 600 700 800 900 1000-180
-90
0
90
180
f [Hz]
[
o]
PBNv2 – First Public Technical Course 23
Airgap calibration
rigid dummy specimen
November 29, 2018 | Rejlek et al.
- input Z
- transfer Z
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Test case: rigid cavity-backed plate
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 24
SPL [dB] @ receiver
Experimental plate and analytical cavity characterisation – NO Trim
• 40cm patch → 30Hz structure – 430Hz fluid
• Adequate prediction at freq. higher than theoretical limit
• Analytical cavity model updating → equivalent damping coefficient
100 200 300 400 500 600 700 800 900
60
80
100
120L [dB
]
100 200 300 400 500 600 700 800 900-180
-90
0
90
180
f [Hz]
[
o]
Reference - PTF prediction
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Test case: sub-systems mobility analysis
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 25
Input mobility Y
Experimental plate and trim, analytical cavity characterisation
• Strong interaction trim-cavity
• Weak interaction trim-structure (added structural damping negligible)
• Trim mainly increases cavity absorption
Structure – Trim - Cavity
0 100 200 300 400 500 600 700 800 900
-100
-80
-60
-40
-20L [dB
]
0 100 200 300 400 500 600 700 800 900
-100
0
100
[dB
]
f [Hz]
© VIRTUAL VEHICLE
100 200 300 400 500 600 700 800 900
60
80
100
120L [dB
]
100 200 300 400 500 600 700 800 900-180
-90
0
90
180
f [Hz]
[
o]
Test case: cavity-backed plate with liner
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 26
SPL [dB] @ receiver
Experimental plate and trim, analytical cavity characterisation
• 40cm patch → 30Hz structure – 430Hz fluid
• Adequate prediction up to half fluid wavelength
• Trend is captured at higher freq.
Reference- PTF prediction
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Conclusions
pros
▪ fast material characterisation
▪ (quasi) non-local effects included
▪ no need for material microscopic parameters
▪ high degree of versatility (test/simulation) and scalability
▪ suitable for target setting procedure (OEM-trim supplier)
▪ might become a new standard for material description
cons
▪ sampling criterion
▪ flat trim specimens
▪ Equivalent mechanical models
▪ Empirical models
▪ Transfer-Matrix-Method
▪ PTF
▪ Microstructural models
Accuracy
Assumptions
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PBNv2 – First Public Technical Course 27November 29, 2018 | Rejlek et al.
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Outlook & ongoing research
▪ Sound proof of validity range, modelling guidelines
▪ Generalisation of the methodology
▪ thickness variation
▪ non-planar geometries
▪ finite size of trim specimen
▪ Integration into existing OEM / supplier
product development processes
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PBNv2 – First Public Technical Course 28November 29, 2018 | Rejlek et al.
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Publications
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 29
Polanz, M. et al. (2018), The Patch-Transfer-Function (PTF) Method Applied to Numerical Models of Trim Materials
Including Poro-Elastic Layers, SAE International, DOI:10.4271/2018-01-1569.
Veronesi G. and Nijman E.J.M. (2016), On the sampling criterion for structural radiation in fluid. The Journal of the
Acoustical Society of America, 139, 2982-2991, DOI: http://dx.doi.org/10.1121/1.4950989.
Albert, C. G. et al. (2016), Prediction of the vibro-acoustic response of a structure-liner-fluid system based on a patch
transfer function approach and direct experimental subsystem characterisation, Applied Acoustics, 112, 14 – 24, ISSN
0003-682X, DOI: http://dx.doi.org/10.1016/j.apacoust.2016.05.006.
Veronesi G. (2015), A Novel PTF-Based Experimental Characterisation fo Poro-elastic Materials: Method and Sampling
Criterion. PhD Thesis, Università degli Studi di Ferrara, Facoltà di Ingegneria.
Veronesi G., Albert C., Rejlek J., Nijman E., Bocquillet A. (2014), “Patch Transfer Function Approach for Vibro-Acoustic
Analysis of Fluid-Porous- Structural Problems”, In proceedings of the 8th International Styrian Noise, Vibration &
Harshness Congress (ISNVH 2014), July 2-4, Graz, Austria, SAE Technical Paper 2014-01-2092, doi:10.4271/2014-01-
2092.
Rejlek J., Veronesi G., Albert C., Nijman E., Bocquillet A. (2013), “A combined Computational-Experimental Approach for
Modelling of Coupled Vibro-Acoustic Problems”, SAE Technical Paper 2013-01-1997, DOI:10.4271/2013-01-1997.
Albert C. (2012) Vibro-acoustic coupling of structural, porous and fluid domains based on simulation and experiment,
M.Sc. thesis, Institute of Theoretical and Computational Physics, Graz University of Technology.
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Acknowledments
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 30
PBNv2 H2020-MSCA-ITN-ETN project (GA 721615)
VIRTUAL VEHICLE Research Center is funded within the COMET – Competence Centers for Excellent
Technologies – programme by the Austrian Federal Ministry for Transport, Innovation and Technology
(BMVIT), the Federal Ministry for Digital and Economic Affairs (BMDW), the Austrian Research Promotion
Agency (FFG), the province of Styria and the Styrian Business Promotion Agency (SFG). The COMET
programme is administrated by FFG.
Industrial & scientific partners involved
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Thank you for your attention!
November 29, 2018 | Rejlek et al. PBNv2 – First Public Technical Course 31
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~ Trim ~
Dr. Jan Rejlek
Department NVH & Information systems
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Inffeldgasse 21A
A-8010 Graz
www.v2c2.at