sae 2007 sb nvh workshop web...1 sae sb nvh sae 2005 nvh conference structure borne nvh workshop...

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SAE 2005 NVH ConferenceStructure Borne NVH Workshop

Presenters:

Alan DuncanAlan Duncan Material Sciences Corp.

Greg Greg GoetchiusGoetchius Material Sciences Corp.

SachinSachin GogateGogate DaimlerChrysler Corp.

Greg Greg HoptonHopton LMS North America

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Structure Borne NVH Outline• Introduction• Ride Balance in the Ride Range• NVH Load Conditions• Low Frequency Basics• Live Noise Attenuation Demo• Mid Frequency Basics• Utilization of the NVH Toolbox• Closing Remarks

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The Fundamental Secret ofStructure Borne

NVH Performance


NVH Performance

Revealed here today !

1st Corollary

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Primary References (Workshop Basis: 4 Papers)

1. A. E. Duncan, et. al., “Understanding NVH Basics”, IBEC, 1996

2. A. E. Duncan, et. al., “MSC/NVH_Manager Helps Chrysler Make Quieter Vibration-free Vehicles”, Chrysler PR Article, March 1998.

3. B. Dong, et. al., “Process to Achieve NVH Goals: Subsystem Targets via ‘Digital Prototype’ Simulations”, SAE 1999-01-1692, NVH Conference Proceedings, May 1999.

4. S. D. Gogate, et. al., “’Digital Prototype’ Simulations to Achieve Vehicle Level NVH Targets in the Presence of Uncertainties’”,

SAE 2001-01-1529, NVH Conference Proceedings, May 2001

Structure Borne NVH References

WS + Refs. at www.AutoAnalytics.com/papers.html

Structure Borne NVH Workshop - on InternetAt SAE www.sae.org/events/nvc/specialevents.htm

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Supplemental Reference Recommendations

5. T.D. Gillespie, Fundamentals of Vehicle Dynamics, SAE 1992(Also see SAE Video Lectures Series, same topic and author)

6. D. E. Cole, Elementary Vehicle Dynamics, Dept. of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, Sept. 1972

7. J. Y. Wong, Theory of Ground Vehicles, John Wiley & Sons, New York, 1978

8. N. Takata, et.al. (1986), “An Analysis of Ride Harshness” Int. Journal of Vehicle Design, Special Issue on Vehicle Safety, pp. 291-303.

9. T. Ushijima, et.al. “Objective Harshness Evaluation” SAE Paper No. 951374, (1995).

Structure Borne NVH References

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Structure Borne NVH Outline• Introduction

• Ride Balance in the Ride Range

• NVH Load Conditions

• Low Frequency Basics

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Rideand

Handling

NVH Durability

ImpactCrashWorthiness

Competing Vehicle Design Disciplines

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Structure Borne NoiseAirborne Noise

Res

pons

e

Log Frequency

“Low”Global Stiffness

“Mid”

Local Stiffness+

Damping“High”

Absorption+

Mass+

Sealing

~ 150 Hz ~ 1000 Hz ~ 10,000 Hz

Automotive NVH Frequency Range

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Study of Ride Balance

• Demonstrate the First Order Vehicle Modes

• Demonstrate Transient Response in Time Domain

• Derive Transition into the Frequency Domain

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Ride Balance StudyVehicle Traversing a Bump

Impact at Front Suspension Followed by Impact at Rear Suspension

Response at Rear

Rear Suspension is in-phase with FrontAfter one cycle of ride motion, thusminimizing pitch motion.

Response at Front

See Ref. 5, Gillespie

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Total 2178.2 Kg (4800LBS)Mass Sprung 1996.7 Kg

Unsprung 181.5 Kg (8.33% of Total)Powertrain 181.5 Kg

Tires 350.3 N/mmKF 43.8 N/mmKR 63.1 N /mmBeam mass lumped on grids like a beam M2,3,4 =2 * M1,5

31

8

2

6

4

7

5

NVH Model of Unibody Passenger CarSymbolic Outline

From Reference 6

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Excitation Bum p Profile

0.0

5.0

10.0

15.0

20.0

0 100 200 300 400 500

Distance (mm)

Pro

file

Hei

ght

(mm

) Profile

On to 100,380

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Pitch at Mid-Car DOF3

-1.0E-04

-8.0E-05

-6.0E-05

-4.0E-05

-2.0E-05

0.0E+00

2.0E-05

4.0E-05

6.0E-05

8.0E-05

1.0E-04

0 1 2 3Time (sec.)

Ro

tati

on

- R

adia

ns Base Model

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Pitch Response - Baseline Model

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

0.0 5.0 10.0 15.0 20.0Frequency Hz

Ro

tati

on

Rad

ian

s

Base Model

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X ( f ) = Fourier Transform of X ( t ){X ( f ) } = [ H ( f ) ] ∗∗∗∗ { F ( f ) }{

Fourier transformof the input forces,vector of all inputpossibilities

Fourier transformof the outputfor unit input forcessystem OUT / IN FRF(Known Load = Unity)

Spring Analogy ( C = 1 / K ) X = C * F

{

CaveatCaveat X ( t ) must be PeriodicLinear System 5 sec

F(t) is Periodic

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FFT of the Input Bump

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

0.E+00 4.E-03 8.E-03 1.E-02 2.E-02 2.E-02

Cycles / mm

Ampl

itude

mm

Bump FFT

Transform Input Force to F(f)

20 Hz @ 45 MPH

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FFT of the Input Bump

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

0.E+00 4.E-03 8.E-03 1.E-02 2.E-02 2.E-02

Cycles / mm

Ampl

itude

mm

Bump FFT

Transform Input Force to F(f)

20 Hz @ 45 MPH

0.0 20.0 Hz

Amplitude is ApproximatelyConstant over theFrequency Range

Constant Displacement

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P itch a t M id -C ar D O F 3

1 .0 E-0 8

1 .0 E-0 7

1 .0 E-0 6

1 .0 E-0 5

1 .0 E-0 4

0 5 1 0 1 5 2 0F req u en cy H z

Ro

tati

on

Rad

ian

s Tim e D om a in F F T

F F T o f Inpu t

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Ride Balance Study Summary

• Demonstrated the Fundamental Bounce and Pitch Modes in the Ride Range

• Demonstrated Transient Response in Time Domain then Obtained the FRF

• Derived Direct Computation of FRF in the Frequency Domain

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Two Main Sources

Noise and Vibration Sources

Suspension Powertrain

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Typical NVH Pathways to the Passenger

PATHS FOR

STRUCTURE BORNE

NVH

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• Low Frequency BasicsNew: Harshness Discussion

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StructureBorneN (Noise)V (Vibration)H (Harshness)

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Harshness Definition

Excitation:Transient event transmitted through the tires due to

road irregularities such as tar strip impacts or similar discrete inputs.

Response:An unpleasant ride experience characterized by:1) A short duration For/Aft tactile spike (Shock)2) A short duration Noise spike (Impact Boom)3) Extended post-event oscillatory vibration

(After Shake)4) A combination of the above ! ! ! ! ! ! !

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Tire Patch Loading Schematic

TireTire Patch Points

Tire Patch

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Tire

Cleat

Start of the Impact Event

Forward Travel

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Tire

Net Aft Reaction‘Tractive Force’

Net Reaction

DifferentialVerticalForce

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Tire

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Tire

Net Fwd Reaction‘Tractive Force’

Net Reaction

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Tire

End of the Impact Event

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Factors Leading to Increased For/Aft Response

Ride Spring Rate

• Sign Reversal in For/Aft Direction

• Recession Rate is Higher than Ride Rate

Recession Rate

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Vehicle Response to a Cleat Impact Event

Short Duration ResponsePeak Overshoot (Shock)Observed in time Domain

Logarithmic Decrement Indicates the Performance for Post-Event Oscillation

(After Shake)Ref. 9

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FrequencyDomain(Resonance Content)

Time Domain(Peak Overshoot)

NoiseResponse

TactileResponse

HarshnessParameters

Harshness Criteria : Tactile and Noise Response


1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

0.0 5.0 10.0 15.0 20.0Frequency Hz

Ro

tati

on

Rad

ian

s

Base Model


1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

0.0 5.0 10.0 15.0 20.0Frequency Hz

Ro

tati

on

Rad

ian

s

Base Model

Ref. 8

Ref. 9

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NVH Workshop Topic Outline• Introduction




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Low Frequency NVH Basics

• Subjective to Objective Relationships

• Single Degree of Freedom Vibration

• Vibration and Noise Attenuation Strategies

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RECEIVER

PATH

SOURCE

Low Frequency NVH Fundamentals

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Subjective to Objective Conversions

Subjective NVH Ratings are typically based on a 10 Point Scale resulting from Ride Testing

A 2 ≈≈≈≈ 1/2 A 1Represents 1.0 Rating Change

TACTILE: 50% reduction in motion

SOUND : 6.dB reduction in sound pressure level ( long standing rule of thumb )

Receiver Sensitivity is a Key Consideration

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m

APPLIED FORCE

F = FO sin 2 π f t

k c FT

TR = FT / F

TransmittedForce

Single Degree of Freedom Vibration

=√ f 2fn

2) 2

ffn

( 2 d ) 21 +1 + ffn

( 2 d ) 21 +

( 1- ffn

( 2 d ) 2+

d = fraction of critical damping

fn = natural frequency √(k/m)

f = operating frequency

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0 1 2 3 4 50

1

2

3

4Tr

ansm

issi

bilit

y R

atio

1.414

0.5

0.1

0.15

0.375

1.0

0.25

Frequency Ratio (f / fn)

Vibration Isolation Principle

m

APPLIED FORCEF = FO sin 2 π f t

k c FT

TR = FT / F

TransmittedForce

Isolation RegionIsolation Region

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Body on Suspension Single DOF ModelIsolation from Base Excitation

Xin

Xout

Transmissibility Ratio is Xout / Xin

Example: Vertical Ride Mode at 1.3 Hz provides isolation starting at 1.8 Hz. This provides isolation for the first order Hop and Tramp modes.

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Simplified Models from 1 to 8 DOF’s

1 DOF 2 DOF

fYO

x

YO

x

4 DOF 8 DOF

YO

x

Enforced Base Motion

YO

x

XYO

Isolation Region

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8 Degree of Freedom Vehicle NVH Model

1 2 4 5

6 7

8

3

TiresWheels

SuspensionSprings

Engine Mass

EngineIsolator

Flexible Beam for Body

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Vibration and Noise Attenuation Methods

Main Attenuation Strategies• Reduce the Input Forces from the Source

• Provide Isolation

• Mode Management

• Nodal Point Mounting

• Dynamic Absorbers

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• Mode Management



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Reduction of Input Forces from the Source

Road Load Excitation• Use Bigger / Softer Tires• Reduce Tire Force Variation• Drive on Smoother Roads

Powertrain Excitation• Reduce Driveshaft Unbalance Tolerance• Use a Smaller Output Engine• Move Idle Speed to Avoid Excitation Alignment• Modify Reciprocating Imbalance to alter Amplitude or

Plane of Action of the Force.

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• Provide Improved Isolation

• Mode Management



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8 Degree of Freedom Vehicle NVH ModelForce Applied to Powertrain Assembly

Forces at Powertrain could represent a First OrderRotating Imbalance

1 2 4 5

6 7

8

3

Feng

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Engine Isolation Example

Response at Mid Car

0.0001

0.0010

0.0100

0.1000

1.0000

5.0 10.0 15.0 20.0Frequency Hz

Velo

city

(mm

/sec

)

Constant Force Load; F ~ A 15.9 Hz8.5 Hz7.0 Hz

700 Min. RPM First Order UnbalanceOperation Range of Interest

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Concepts for Increased Isolation“Double” isolation is the typical strategy for further improving isolation of a given vehicle design.

Subframe is Intermediate Structure

Suspension Bushing is first level

Second Level of Isolation is at Subframe

to Body Mount

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8 Degree of Freedom Vehicle NVH ModelRemoved Double Isolation Effect

1 2 4 5

6 7

8

3

WheelMass

Removed

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Double Isolation ExampleVertical Response at DOF3

0.0E+00

1.0E+00

2.0E+00

3.0E+00

4.0E+00

5.0E+00

6.0E+00

5.0 10.0 15.0 20.0Frequency Hz

Velo

city

(m

m/s

ec)

Base Model

Without Double_ISO

1.414*fn

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• Mode Management



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Mode Management Chart

0 5 10 15 20 25 30 35 40 45 50HzFirst Order Wheel/Tire Unbalance V8 Idle

Hot - Cold

EXCITATION SOURCESInherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.)Process Variation Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances)

Hz

Hz0 5 10 15 20 25 30 35 40 45 50

0 5 10 15 20 25 30 35 40 45 50

CHASSIS/POWERTRAIN MODES

Ride ModesPowertrain Modes

Suspension Hop and Tramp ModesSuspension Longitudinal Modes

Exhaust Modes

BODY/ACOUSTIC MODES

Body First Bending First Acoustic Mode

Steering Column First Vertical BendingBody First Torsion

(See Ref. 1)

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8 Degree of Freedom Vehicle NVH ModelBending Mode Frequency Separation

1 2 4 5

6 7

8

3

Beam Stiffness was adjusted to align Bending

Frequency with Suspension Modes and then

progressively separated back to Baseline.

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Response at Mid Car

0.10

1.00

10.00

100.00

5 10 15 20Frequency Hz

Velo

city

(mm

/sec

)

18.2 Hz Bending13.Hz Bending10.6 Bending

8 DOF Mode Separation Example

18.2 Hz13.0 Hz

10.6 Hz

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• Mode Management



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Front input forces Rear input forces

First Bending: Nodal Point Mounting ExampleMount at Nodal Point

Locate wheel centers at node points of the first bending modeshapeto prevent excitation coming from suspension input motion.

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Passenger sits at node point for First Torsion.

Side View

First Torsion: Nodal Point Mounting ExamplesMount at Nodal Point

Transmission Mount of a3 Mount N-S P/T is nearthe Torsion Node.

Rear View

Engine

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Powertrain Bending Mode Nodal Mounting

1 2 4 5

6 7

3

Mount system is placed to support Powertrain at the Nodal Locations of the First order Bending Mode. Best compromise with Plan View nodes should also be considered.

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8 Degree of Freedom Vehicle NVH ModelBending Node Alignment with Wheel Centers

1 2 4 5

6 7

8

3

Redistribute Beam Masses to move Node Points to

Align with points 2 and 4

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Response at Mid-Car

0.0E+00

1.0E+00

2.0E+00

3.0E+00

4.0E+00

5.0 10.0 15.0 20.0Frequency Hz

Velo

city

(m

m/s

ec)

Node ShiftedBase Model

First Bending Nodal Point Alignment

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• Mode Management



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YO

xSDOF

Dynamic Absorber Concept

MYO

x

Auxiliary Spring-Mass-Damperm = M / 10

2DOFM

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Powertrain Example of Dynamic Absorber

Anti-Node Identifiedat end of Powerplant

k c

Absorber attached at anti-node acting in the Vertical and Lateral plane.

Tuning Frequency = √√√√ k/m

m

[Figure Courtesy of DaimlerChrysler Corporation]

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Baseline Sound Level63 Hz Dynamic Absorber63 + 110 Hz Absorbers

Baseline Sound Level63 Hz Dynamic Absorber63 + 110 Hz Absorbers


10 dB

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• Mode Management



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Greg Goetchius

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Sachin Gogate

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RECEIVER

PATH

SOURCE

Mid Frequency NVH Fundamentals

This looks familiar!Frequency Range of Interest has changed to

150 Hz to 500 Hz

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Typical NVH Pathways to the Passenger

PATHS FOR

STRUCTURE BORNE

NVH

Noise Paths are thesame as Low

Frequency Region

Noise Paths are thesame as Low

Frequency Region

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Mid-Frequency Analysis CharacterStructure Borne Noise

Airborne Noise

Res

pons

e

Log Frequency“Low”

Global Stiffness“Mid”

Local Stiffness+

Damping

“High”

Absorption+

Mass+

Sealing

~ 150 Hz ~ 1000 Hz ~ 10,000 Hz

High modal densityand coupling in

source, path andreceiver

• Mode separation is less practical inmid-frequency

• New Strategy is Effective Isolation:Achieved by reducing energy transferlocally between source and receiver atkey paths.

•• Mode separation is less practical inMode separation is less practical inmidmid--frequencyfrequency

•• New Strategy is Effective Isolation:New Strategy is Effective Isolation:Achieved by reducing energy transferAchieved by reducing energy transferlocally between source and receiver atlocally between source and receiver atkey paths.key paths.

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Mid-Frequency Analysis Character

• Important characteristics of mid frequency analysis

&

Identifying Key Noise Paths

Effective Isolation

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&



Effective IsolationEffective Isolation

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Classical SDOF: Rigid Source and Receiver

T ran

smis

s ibi

l ity

Ra t

io

1.0 1.414 10.0

f / f n

“Real Structure”Flexible (Mobile)Source and Receiver

Isolation Effectiveness

Effectiveness deviates from the classical development as resonances occur in the receiver structure and in the foundation of the source.

Isolation RegionIsolation Region

1.0

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Mobility• Mobility is the ratio of velocity response at the excitation point on structure

where point force is applied

Mobility =Velocity

Force

• Mobility, related to Admittance, characterizes Dynamic Stiffness of the structure at load application point

Mobility =Frequency * Displacement

Force

=Frequency

Dynamic Stiffness

NVH Workshop

• The isolation effectiveness can be quantified by a theoretical model based on analysis of mobilities of receiver, isolator and source

• Transmissibility ratio is used to objectively define measure of isolation

TR =Force from source without isolator

Force from source with isolator

Isolation

V r

V ir

V is

F r

F ir

Receiver

Source

F is

Fs V s

Isolator

VF s=

Y i + Y r + Y s

V r

F r

Receiver

Source

F s V s

VF s=

Y r + Y s

VV

2003, 2005 ERRATA

NVH Workshop

• The isolation effectiveness can be quantified by a theoretical model based on analysis of mobilities of receiver, isolator and source

• Transmissibility ratio is used to objectively define measure of isolation

TR =Force from source without isolator

Force from source with isolator

Isolation

V r

V ir

V is

F r

F ir

Receiver

Source

F is

Fs V s

Isolator

VF s=

Y i + Y r + Y s

V r

F r

Receiver

Source

F s V s

VF s=

Y r + Y s

VV

NVH Workshop

Isolation

TR = ⏐ ( Y r + Y s ) / ( Y i + Y r + Y s ) ⏐

• For Effective Isolation (Low TR) the Isolator Mobility must exceed the sum of the Source and Receiver Mobilities.

Y r : Receiver mobility

Y s : Source mobility

Y i : Isolator mobility

V m

V im

V if

F m

F im

Receiver

Source

F if

F f V f

Isolator

TR = Force from source without an isolator Force from source with an isolator

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Effective Isolation

&


Identifying Key Noise PathsIdentifying Key Noise Paths

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Identifying Key NVH PathsKey NVH paths are identified by Transfer Path Analysis (TPA)

Fi

TactileTransferTactile

TransferAcousticTransfer

AcousticTransfer

Operating loads Operating loads

• TPA is a technique to perform phased summation of partial responses through all NVH paths to give total tactile or acoustic response under operating loads at a given frequency

• TPA is applicable in both testing and simulation scenarios to identify key paths

Break the system at the points where the forces enter the body (Receiver)

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Noise Path Analysis

Fi

• Total Acoustic Response is summation of partial responses over all noise paths

Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ (P/F) i * Fi ]

Acoustic Transfer (P/F)iAcoustic Transfer (P/F)i

Pi : Partial contribution of path i due to operating force

Operating loads createForces (Fi) into body atAll noise paths

(P/F) i : Acoustic Transfer Function of the ith Path

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Transfer Path Analysis

( contributors + )

( reducers - )

…

FrontUpperControlArm

FrontShockAbsorber Rear

ShockAbsorber

RearUpperArm

TotalNoise

(((( AllPaths))))

FrontStabilizer

FrontSpring

• TPA allows path rankings based on contribution to total response of noise paths at a given frequency

• TPA thus helps identify key noise paths

• TPA is mainly used for acoustic response in mid frequency range

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Designing for Mid Frequency


Effective Isolation

&


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When designing a new vehicle, the first phase is to satisfy generic targets for key parameters along all noise paths in order to achieve effective isolation.

What are these generic targets andkey parameters ?

What are these generic targets andkey parameters ?

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Generic Noise Path Targets



∆∆∆∆ XKBsng

V/F

P/VP/F

F

Ksource

(Kbody)

Transmissibility along a given noise path (TRi)

TR = ( Y r + Y s ) //// ( Y i + Y r + Y s )

TR = ( ) //// ( ) K body

1K source

1+ K body

1 + K iso.

1K source

1+

88SAE SB NVH


Generic Noise Path TargetsTR = ( ) //// ( ) K body

1K source

1+ K body

1 + K iso.

1K source

1+

K iso

K sourceK body

K iso1.0 5.0 Infinite

1.0

5.0

Infinite

0.67 0.54 0.50

0.54 0.28 0.17

0.50 0.17 0.00

As a generic target, body to bushing stiffness ratio of at least 5.0 and very high source to bushing stiffness ratio (~ infinite) is desired to achieve “good” TR of 0.17

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0

0.1

0.2

0.3

0.4

0.5

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

Series2

0.0

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 10

Stiffness Ratio; K body / K bsg

Tran

smis

sibi

lity

Rat

io

TR = ( K bsg ) //// ( K bsg + K body )

For a very stiff source

Target Min. = 5 gives TR = .17

Relationship of Body-to-Bushing Stiffness Ratio to Transmissibility

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Fi



Operating loads createForces (Fi) into body atAll noise paths

Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ Fi * (P/F) i ] = ΣΣΣΣ paths [ Fi * (P/V) i * (V/F)i]


(P/F) Acoustic Sensitivity(V/F) Structural Point Mobility (Receiver)

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• For a given force generated at a source attachment to body, lowering sensitivities (P/F) or (V/F) along a pathwould reduce total response

• Typical generic targets,

- Acoustic Sensitivity (P/F) in 50 - 60 dBL/N range

- Structural Mobility (V/F) less than 0.312 mm/sec/N

For example, for Acoustic Response Pt

Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ Fi * (P/F) i ] = ΣΣΣΣ paths [ Fi * (P/V) i * (V/F)i]

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K iso

K body >= 5.0K iso

K source ~ very high

AcousticSensitivity < 50 - 60

dBL/N

StructuralMobility < 0.312 mm/sec/N

How does one achieve these generic targets ?

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Generic Noise Path TargetsHow does one achieve

• Increase local body attachment stiffness (Kbody) through structural modifications

K iso

K body >= 5.0

• Reduce attachment isolator stiffness (Kiso) while balancing the conflicting requirement of other functionalities such as Ride & Handling

StructuralMobility < 0.312

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How does one achieve

• Increase source side attachment stiffness (Ksource)

• Reduce attachment isolator stiffness (Kiso)

K iso

K source ~ very high

In Automotive Structures, it is realistic to expect that the Source to isolator stiffness ratio is high since Source usually corresponds to a stiff structure (such as powertrain or axle).


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How does one achieve

• At a given frequency, Acoustic Sensitivity (P/F) is

P/F = (P/V) X FrequencyBody stiffness

• Based on the above equation, increasing body stiffness usually reduces Acoustic Sensitivity.



dBL/N

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How does one achieve:

• In such cases, the Acoustic Sensitivity can be reduced by reducing the overall body panel velocity through application of damping treatments

• There are situations when increasing body stiffness does not reduce Acoustic Sensitivity


dBL/N


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Application of Damping TreatmentEffect on sound response of damping treatment

applied on key identified contributing panels


12.5dBA Reduction

Floor without damping treatment

Floor with damping treatment

Frequency (Hz)

5.0 dBA

SPL

(dB

A)

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While designing a new vehicle, generic targets are set for key parameters along all noise paths in order to achieve effective isolation.

Is it really necessary to achieve generic targets forall noise paths ?

Is it really necessary to achieve generic targets forall noise paths ?

Probably Not !!Probably Not !!

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Designing for Mid FrequencyDriver’s Ear Noise

Vehicle Level Response

Original Noise Path Contributions

Transfer Path Analysis

Some noise paths are more dominant than others

Impose more strict requirements for these dominant paths and relax requirements for other paths to achieve more “rebalanced”noise

Improved Noise Path Contributions

Driver’s Ear Noise

Vehicle Response to Meet NVH Targets

Original NoiseReduced Noise

100SAE SB NVH


Yesor

Time Out

No

Re-DesignSub-System

Evaluate Sub-SystemPerformance

Evaluate Sub-SystemPerformance

No

Meet VehicleGoals?

RebalanceTrade-OffRebalanceTrade-Off

Meet Sub-System

Goals? Evaluate Vehicle GoalsEvaluate Vehicle Goals

Mid Frequency NVH Goal Achievement Process

Initial Sub-System Targets

Yesor

Time Out

101SAE SB NVH



Principles to follow

• At the beginning of program, work towards generic targets for all noise paths in order to achieve effective isolation.

• As the design is firmed out, shift focus to key contributing noise paths using Transfer Path Analysis in order to meet target for all NVH operating load conditions.• Perform path “rebalancing” to arrive at revised path targets if Sub-System goal achievement is not possible due to architectural constraints.

102SAE SB NVH


Final Remarks on Mid Frequency Analysis

• Effective isolation at dominant noise paths is critical• Effective isolation at dominant noise paths is critical

• Reduced mobilities at body & source and softenedbushing are key for effective isolation

• Reduced mobilities at body & source and softenedbushing are key for effective isolation

• It is important to balance NVH requirements againstother functionalities (Ride and Handling, Impact)

• It is important to balance NVH requirements againstother functionalities (Ride and Handling, Impact)

• It is important to understand the robustness ofdesign recommendations

• It is important to understand the robustness ofdesign recommendations

• Other means of dealing high levels of source inputsuch as damping treatments are also effective

• Other means of dealing high levels of source inputsuch as damping treatments are also effective

103SAE SB NVH


Structure Borne NVH Outline• Introduction• Ride Balance in the Ride Range• NVH Load Conditions• Low Frequency Basics• Live Noise Attenuation Demo• Mid Frequency Basics• Utilization of the NVH Toolbox• Closing Remarks Greg Hopton

104SAE SB NVH


Utilization of the NVH Toolbox

DashboardDashboard

Air treatmentAir treatment

EngineEngine

AuxiliariesAuxiliaries

TiresTires

GearboxGearbox Drive lineDrive lineSteering SystemSteering System

Wheel SuspensionsWheel Suspensions

Body TrimBody Trim

Body StructureBody StructureSeatsSeats

105SAE SB NVH


ExperimentalExperimentalAssessmentAssessment

ExperimentalExperimentalModelingModeling

NumericalNumericalModelingModeling

Spectral AnalysisSpectral Analysis

SSignatureignature

IntensityIntensityHolographyHolographyOperational DeflectionOperational Deflection

SSoundound QQualityuality

ModalModal AnalysisAnalysis

TPA TPA (structure(structure--borne)borne)

FRF BasedFRF Based ModelingModeling

ASQ ASQ (air(air--borne)borne)

BEMBEM

Ray TracingRay Tracing

VibroVibro--acoustic Modalacoustic Modal AnalysisAnalysis

EESEASEA

Technologies for NVHInputInput TransferTransfer ResponseResponse

Acoustical Acoustical MechanicalMechanical

MediumMediumStructure Surface Structure Surface AirBorneAirBorne

Acoustic Acoustic VibrationVibration

Spectral AnalysisSpectral Analysis

FFRF AnalysisRF Analysis

Acoustical FEMAcoustical FEMStructural FEMStructural FEM

SSignatureignature

MBSMBS

SEASEA

106SAE SB NVH


Various TechniquesLow Frequency Mid Frequency High Frequency

Modal Structuring

PCA Acoustic holography

SEA

Modal analysisTPA, ASQ

Inverse BEMODS

Vibro-acoustic

Spectral AnalysisSound Quality

Intensity

Ray tracingFEMBEM

Time domain BEM

ExperimentalExperimentalModelingModeling

NumericalNumericalModelingModeling

HybridHybridModelingModeling

CATCAT

CAECAE

FRF Structuring Experimental SEA

107SAE SB NVH


Hybrid Modeling

•• A A ““HybridHybrid”” model is a full system performance model is a full system performance model composed of both numerical and model composed of both numerical and experimental based modelsexperimental based models

•• TestTest--based models are used for existing / carryover based models are used for existing / carryover subsub--systemssystems•• Faster than building numerical modelsFaster than building numerical models•• More accurately match hardwareMore accurately match hardware

•• Numerical models are used for subNumerical models are used for sub--systems of systems of design interestdesign interest•• Automatic optimizationAutomatic optimization•• Design Space StudiesDesign Space Studies

•• Performance is evaluated at system levelPerformance is evaluated at system level•• More accurate, faster runMore accurate, faster run--times than fulltimes than full

numerical modelsnumerical models•• More flexibility than full testMore flexibility than full test--based modelsbased models

108SAE SB NVH


When to Use These Methods

Experimental ModelingExperimental Modeling• Utilize previous generation hardware• Utilize prototype builds• Numerical models are not available

Numerical ModelingNumerical Modeling• Physical hardware is not available• Evaluate a variety of analysis cases quickly• Understand variability

Hybrid ModelingHybrid Modeling• Both numerical and experimental models are available• Fast run times• Evaluate variety of sub-assemblies or components quickly

109SAE SB NVH


Structure Borne NVH Outline• Introduction• Ride Balance in the Ride Range• NVH Load Conditions• Low Frequency Basics• Live Noise Attenuation Demo• Mid Frequency Basics• Utilization of the NVH Toolbox• Closing Remarks Alan Duncan

110SAE SB NVH


Rideand

Handling

NVH Durability

ImpactCrashWorthiness

Competing Vehicle Design Disciplines

111SAE SB NVH



NVH Performance


NVH Performance

Revealed here today !

112SAE SB NVH


The Fundamental Secret of Structure Borne NVH Performance

The Fundamental Secret of Structure The Fundamental Secret of Structure Borne NVH PerformanceBorne NVH Performance

To Minimize Structure Borne NVH, connect between Source and Receiver Sub-Systems at Locations where the Motion is at a Minimum.

First Best Principle for NVH Improvement is Minimization /

Understanding of the Source Excitation.

Ist Corollary

113SAE SB NVH


First Best Principle for NVH Improvement is Minimization /

Understanding of the Source Excitation.

IstCorollary

The Fundamental Secret of Structure Borne NVH Performance

The Fundamental Secret of Structure The Fundamental Secret of Structure Borne NVH PerformanceBorne NVH Performance

Meets Conditions of the Attenuations Strategies

Thank You for Attending theStructure Borne NVH Workshop

Your Presenters today were:

Alan Duncan, Material Sciences Corp.Contact: [email protected] or [email protected]

Greg Goetchius, Material Sciences Corp.Contact: [email protected]

Sachin Gogate, DaimlerChrysler Corp.Contact: [email protected]

Visit: SAE at www.sae.org/events/nvc/specialevents.htmAlso with Ref.s at: www.AutoAnalytics.com/papers.html

to download the Structure Borne NVH Workshops

To Minimize Structure Borne NVH, connect between Source and Receiver Sub-Systems at Locations where the Motion is at a Minimum.

Greg Hopton, LMS North AmericaContact: [email protected]

sae 2007 sb nvh workshop web...1 sae sb nvh sae 2005 nvh conference structure borne nvh workshop...

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