ecanum We build silence Acoustic aterials: Characterization ecanum Inc. info@mecanum.com www.mecanum.com
otivation Sound quality in vehicles starts at the design stage odels are used to simulate the acoustics of vehicles odels are used to develop and optimize sound packages aterial properties and cell morphology are the input parameters to models 2
What about sound packages? Sound packages are made of a combination of materials, including: Carpet Fabric Felt Fiber Foam Porous film 3
What is a porous material? Porous material Two phases: solid and fluid Elastic coupling Visco-inertial coupling What does it do? Transforms acoustic energy into heat How does it dissipate energy? Viscous effect Thermal effect Structural damping 4
What about their frame? Elastic frame Rigid frame Limp frame Granular 5
Types of Porous aterials Polymeric foam etallic foam Recycled Glass wool / glass fiber Felt ultilayer, carpet and fabric 6
How are they modeled? They are modeled at a homogeneous macroscopic scale. H 2 acroscopic scale h << H h << H 1 << H H 1 << H 2 u x u x h u z u z H 1 u y u y Porous material acroscopic scale Homogeneous solid Homogeneous fluid 7
How are they modeled? At a local scale: heterogeneous At a macroscopic scale: homogeneous Example: Chipped foam 8
How are they modeled? BIOT (u,p) formulation worked out by ATALLA and PANNETON governs the propagation of the coupled elastic waves (compression and shear) and acoustic wave (compression). μu ~ i,jj ~ λ + 1 ω 2~ ρ f μ ~ + u j,ij + ω 2~ ρ s p, ii + p γ ~ ~ 1 = K f u i u i,i = γ ~ p, i Elasto-dynamic equation Helmholtz equation [J. Acoust. Soc. Am. 104(3),p. 1444-1452] Biot's macroscopic parameters u : p : Solid phase macroscopic displacement vectors Fluid phase macroscopic pressure ~: Denotes a complex and frequency dependent quantity λ,µ : Effective solid phase Lamé coefficients K f : Effective fluid phase bulk modulus ρ s : Effective solid phase density ρ f : γ : Effective fluid phase density Fluid-solid coupling coefficient 9
Rigid and Limp limits (P) Rigid frame formulation - Helmholtz equation with effective density and bulk modulus : Laplacian operator (P) Limp frame formulation - Helmholtz equation with effective density and bulk modulus - Added inertia of the solid phase For heavy frame, ρ, the limp limit tends to the rigid limit 10
Porous aterials: odeling (cont d) Accuracy echanical Admittance Empirical Limp Rigid Poroelastic Hypotheses Computation time 11
12 What are the basic parameters? The Biot s parameters are obtained from macroscopically averaged geometrical, physical and elastic properties. loss factor structural ) ( Poisson ratio s modulus Young' ) ( the foam density of 1 characteristic length thermal ' viscous characteristic length tortuosity static flow resistivity porosity ~ ~ ~ ~ ~ ~ η ω ν ω ρ Λ Λ α σ φ E λ μ ρ s γ f ρ f K α Λ Λ ) ( ) ( Λ = s ds s r v v dv r v = Λ s ds v dv
What are the input parameters? Compatible with: NOVA FOA-X Difficult to measure Source: GUI from NOVA 13
easuring input parameters? Impedance tube Resistance meter echanical analyzer Porosity and density meter Tortuosity meter FOA-X NOVA 14
Impedance and Transmission Tube Properties: - Absorption coefficient - Reflection coefficient - Surface impedance AST E1050, ISO 10534-2 Correction for temperature, barometric pressure, and attenuation. Acquisition System 15
Impedance and Transmission Tube Fully automated High accuracy Correction for: - Temperature - Barometric pressure - Tube attenuation Compatible with FOA-X characterization module TUBE-X Software 16
SIGA - Airflow Resistance eter Properties: - Static airflow resistivity - Static air permeability Direct method based on AST C522 Comparative method based on standardized resistance. Foams, fibers, felts, fabrics, and films Acquisition System 17
SIGA - Airflow Resistance eter ay be used for quality control SIGA-X Software 18
QA - Quasi-static echanical Analyzer Properties: - Young s modulus - Poisson s ratio - Damping loss factor Based on standard ISO 18437-5 Novel direct method gives the true elastic properties. Frequency: 10-100 Hz Acquisition System 19
QA - Quasi-static echanical Analyzer Check how elastic properties vary with frequency QA-X Software 20
Porosity and Density eter Properties: - Open porosity - True bulk density Perfect gas law Acquisition System and PHI-X Software 21
Tortuosity eter Properties: - Tortuosity - Two characteristic lengths Ultrasound techniques - Transmission - Reflection (60 to 1000 khz) Hardware and TOR-X Software 22
FOA-X Properties: - Static airflow resistivity - Tortuosity - Viscous length - Thermal length - Open porosity - Thermal static permeability - Young s modulus - Poisson s ratio - Damping loss factor Unique analytical characterization method based on impedance tube measurements. FOA-X Software 23
FOA-X Classic easurements (optional) ρ 1, σ, φ ~ φσ ρ( ω) = ρ 0α 1 j 1+ ωρoα ~ γ 1 β ( ω) = γ H ω 1 j 1+ j 2ω Η ω j H Acoustic odel FOA-X Characterization odule FOA-X and Impedance Tube Configuration Sample and Holder icrophones Enviro Weather Station Atmospheric Pressure Temperature Relative Humidity Standard AST Impedance Tube Test Noise Source 24
FOA-X Verifying the quality of results The final stage of the characterization is to verify if the characterized properties can be used as input parameters in models to predict correctly the material acoustical indicator. The acoustical indicators of a material are measured with the impedance tube. - Normal sound absorption coefficient - Complex reflection coefficient - Surface impedance coefficient 25
FOA-X Verifying the quality of results Once verified, save properties in a material database 26
ecanum s Hardware & Software Integration NOVA Simulation Software FOA-X Tortuosity eter Porosity/Density eter Resistivity eter Acquisition System QA Database Impedance Tube TUBE-X Software 27
Validation examples... 28
FOA-X versus Classic Characterization (1/6) Porosity Resistivity Tortuosity Classical FOA-X Porosity 0.96 ± 0.01 0.95 ± 0.00 Resistivity (Ns/m 4 ) 5111 ± 244 5118 ± 984 Tortuosity 1.14 ± 0.01 1.15 ± 0.03 Viscous length (µm) 147 ± 10 Thermal length (µm) 274 ± 14 Classic characterization uses: Porosity / density meter Resistivity meter Ultrasound tortuosity meter Thermoformable Sheet Foam Absorption coefficient Absorption coefficient 1 0.9 0.8 (45,62 mm) 0.7 0.6 0.5 (22.81mm) 0.4 0.3 0.2 Prediction (RIGID ODEL) 0.1 easure 0 200 1200 2200 3200 4200 5200 6200 Frequency (Hz) Frequency (Hz) 29
FOA-X versus Classic Characterization (2/6) Porosity Resistivity Tortuosity Classical FOA-X Porosity 0.87 ± 0.02 0.84 ± 0.07 Resistivity (Ns/m 4 ) 78806 ± 1227 80814 ± 2500 Tortuosity 2.12 ± 0.27 1.62 ± 0.43 Viscous length (µm) 29.1 ± 10.4 Thermal length (µm) 85.5 ± 13.6 Classic characterization uses: Porosity / density meter Resistivity meter Ultrasound tortuosity meter Absorption coefficient Absorption coefficient Sheet Foam Carpenter Co. 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 25,00 mm 12,56 Prediction (RIGID ODEL) easure 0 100 1100 2100 3100 4100 5100 6100 Frequency (Hz) Frequency (Hz) 30
FOA-X versus Classic Characterization (3/6) Porosity Resistivity Tortuosity Classical FOA-X Porosity 0.996 ± 0.02 0.99 ± 0.07 Resistivity (Ns/m 4 ) 12153 ± 1228 10425 ± 1838 Tortuosity 1.04 ± 0.07 1.00 ± 0.00 Viscous length (µm) 109 ± 11 Thermal length (µm) 128 ± 21 Classic characterization uses: Porosity / density meter Resistivity meter Ultrasound tortuosity meter Absorption coefficient elamine Foam 1 0.9 0.8 54,10 0.7 0.6 0.5 Frame resonance 0.4 27,17 0.3 0.2 Prediction (RIGID ODEL) 0.1 easure 0 200 1200 2200 3200 4200 5200 6200 Frequency Frequency(Hz) (Hz) 31
FOA-X versus Classic Characterization (4/6) Tortuosity Viscous length Thermal length Classical FOA-X Porosity 0.89 ± 0.02 Resistivity (Ns/m 4 ) 43456 ± 1257 Tortuosity 1.13 ± 0.04 1.14 ± 0.02 Rigid Frame - etallic Foam GRNI-35-A (150 C) Viscous length (µm) 17.4 ± 2 17.1 ± 3 Thermal length (µm) 130.7 ± 8 137 ± 5 Direct characterization uses: Porosity / density meter Resistivity meter Ultrasound tortuosity meter Absorption coefficient NOVA prediction with FOA-X foam parameters easure Frequency (Hz) 32
NOVA versus Impedance Tube easurements (5/6) Single Layer - Elastic Frame NOVA is fed by the foam parameters measured with FOA-X Frame resonance 33
Quasi-static echanical Analyzer (QA) Validation (simulation with NOVA) Sound absorption coefficient. 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Rigid-frame model Biot poroelastic model Experimental AST E 1050-86 0 200 400 600 800 1000 1200 1400 1600 Frequency (Hz) 34
Experimental Validation for ultilayer System with Impervious Film Plane wave Absorption coefficient Fibrous Septum Foam 2 Rigid wall Frequency (Hz) 35
Experimental Validation for ultilayer System with a Perforated Screen 1 (25.06 mm) Absorption coefficient 1 Perforated screen 3 Rigid frame Perforated screen (0.79 mm) Prediction easure 3 (12.57 mm) Frequency (Hz) 36
Transmission Loss of an Aluminium Panel elamine Configuration 37
Transmission Loss of an Aluminium Panel + Felt All 5 acoustic material properties of the tested felt are computed using FOA-X and used in NOVA for prediction. Test NOVA prediction 38
Transmission Loss of Car Laminated Glass 6,00E+01 NOVA Predictions vs Test TL (db) 5,00E+01 4,00E+01 3,00E+01 2,00E+01 1,00E+01 Glass (Nova) Laminate (Nova) Glass (Test) Laminate (Test) 0,00E+00 10 100 1000 10000 Frequency (Hz) The frequency dependencies of the core material of the laminated glass are accounted for in NOVA 39
Can we use NOVA for complex 3D problems? Yes. For complex configurations NOVA s formulations and FOA-X s measured parameters are used within a ecanum 3D version. They are also used within a novel substruturing method to handle independently several trim components (Implementation in Straco s PE software). aster-structure Acoustic Cavities Air Gap aster-structure Component atrix Complex Porous Components Y ss Y sc aster Structure dof s Y t sc Y cc Acoustic Cavity dof s 40