fraunhofer - testing of trailer coupling

Testing of Trailer Coupling Devices Considering Multiaxial Trailer Loads

LMS ConferenceApril 18th, 2007

InstituteStructural Durability and System Reliability

S. Weiland

InstituteStructural Durability and System Reliability

Page 2

Contents

• Introduction

• Guideline ECE R 55.01 in Comparison with Customer Usage

• Standardized Load Sequence CARLOS TC

• Usage of CARLOS TC at Fraunhofer LBF

• Control and Monitoring of test

• Summary and Perspective

Page 3

CARLOS TC (CAR LOading Standard, Trailer Coupling) Consortium Participants

Car OEMs:Adam Opel AGAudi AGBMW GroupDaimlerChrysler AGFord-Werke AGPorsche AGSkoda AGVolkswagen AGVolvo Car

Technical Control Boards:RWTÜV Fahrzeug GmbH, EssenTÜV Automotive, München

Suppliers:AL-KO GmbHBosal ResearchKarmann GmbHMVG mbHOris Fahrzeugteile Hans Riehle GmbHPD&E Automotive SolutionsMagna Steyr Fahrzeugtechnik

AG & Co KGWestfalia Automotive GmbH & Co KG

Research Institutes:Fraunhofer Institute for Structural Durability LBF (project manager)KATECH (Korea Automotive Technology Institute)

Page 4

Introduction

• Trailer coupling devices (TCD) are safety-critical components

• Test for homologation of TCDs according to ECE R 55.01

• Car manufacturers are testing with service loads similar to customer usage

• Challenges:- New testing procedure which is accepted by OEMs and suppliers - Implementation of new testing procedure in the guideline ECE R 55.01

Page 5

Comparison of Guideline ECE R 55.01 and Customer Usage

• Tests for the homologation of TCDs according to ECE R 55.01 are performed with - sinusoidal loading

! 1-dimensional loading (1-D) ! constant amplitudes (CA)! no mean load (R = -1)! without car-body

F

• Fatigue relevant local stresses and strains on TCDs are depending on- service loads

! 3-dimensional loading (3-D)! variable amplitudes (VA)! variable mean loads (R ≠ -1)! with car-body

Page 6

Uni- & Multiaxial Load – Cycles to Failure

Uni- & Multiaxial Load:- different cycles to failure with the same force amplitudes

Cycles to Failure N

Max

imum

For

ce F

max

uniaxial load

fatigue life curve uniaxial loadfatigue life curve multiaxial load; partly correlated phase

multiaxial load; partly correlated phase

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Load Cycles to Failure

Points of Crack Initiation

Tors

iona

lMom

ent

Constant Amplitude Testing – Type of Failure

CA-Testing:- type of failure depends on load amplitude

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Mean Load - Cycles to Failure

Cycles to Failure N

Stre

ss A

mpl

itude

σa

axial loading

Strain Amplitude σa

time

R = σu / σo

400 N/mm2

Mean Load:- different cycles to failure with same load amplitude

R = 0R = -1

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Currently used guideline ECE R 55.01

The ECE R 55.01 guideline:- sinusoidal loading

! 1-dimensional loading (1-D) ! constant amplitudes (CA)! no mean load (R = -1)

! Durability assessment is critical with respect to:- type of failure- cycles to failure

F

Improvement:Testing procedure oriented on 3-D service loads captures failure types and life time typical in service.

Page 10

Derivation of a Testing Procedure based on Service Loads

Input:42 verification tests / measurements from OEMs

Signal analysis:verifications, normalizations, correlations, load spectra

Derivation of 3 Modules:based on representative 22 load segments

Testing Procedure:damage sums, duration (< 150 h), frequencies, max. amplitudes

CARLOS TC:duration: ~ 92 h, module mix: 10*[5*(10*M1+M2)+M3]

Page 11

CARLOS TC – Distributions of Test-Modules M1, M2, M3 and whole Test-Procedure: 10*(5*(10*M1+M2)+M3)

1 10 100 1000 10000 100000 1E+06 1E+07-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

Longitudinal Force Fx

Number of Level Crossings

M1, 12% omissionM2, 12% omissionM3, 12% omissionCARLOS TC

Test modules 1, 2 and 3 derived from 22 load segments. Module 1:incl. moderate service loadsModule 2:incl. severe service loadsModule 3:incl. exceptional loads

Forc

e F x

/ D

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Current EC Homologation Test ECE R 55.01 (1-D, CA) and CARLOS Trailer Coupling (Realistic loading: 3-D, VA)

[kN] )mm(

mmgDTV

TV

+⋅

⋅= mV = vehicle massmT = trailer mass

ECE R 55.01

ECE R 55.01

ECE R 55.01 FxECE R 55.01 Fz

Number of load cyclesFo

rce

(am

plitu

de) /

D

CARLOS TC Fz

CARLOS TC Fy

CARLOS TC Fx

Page 13

0.02 0.04 0.06 0.08 0.1 0.2 0.4 0.6 0.8 1 20.003

0.130.5

125

102030405060708090959899

99.599.87

99.997

Pro

bab i

lity

%Comparison of Damage-Equivalent Amplitudes ECE R 55.01, Scatter Bands of 42 Verification Tests, CARLOS TC

Damage Equivalent Amplitude Fx/D, Fy/D, Fz/D

Pro

babi

lity,

%

Calibration for test with bodies

CARLOS TC (FxCARLOS TC (FyCARLOS TC (Fz94/20/EC (Fx)94/20/EC (Fz)Fx, Verific TestFy, Verific TestFz, Verific Test

ECE R 55.01 (Fx)ECE R 55.01 (Fz)

Page 14

CARLOS TC – Rainflow Matrices for Whole Test (Car Body)

Fx FyFz

Number of Cycles

From

Bin

, For

ce/D

To Bin, Force/D

Longitudinal Force Lateral ForceVertical Force

Page 15

CARLOS TC – Display of Fictitious Damage Values Using the Load Influence Sphere

0.1 0.5 1.0

Late

ral F

orce

Ver

tical

For

ce

Longitudinal Force Longitudinal Force Lateral Force

Normalized fictitiousdamage value(S-N curve: k = 5)

Ver

tical

For

ce

Page 16

Ratio of Fictitious Damage Values Dfict- CARLOS TC vs. ECE R 55.01

CTC115 / ECE R 55.01

[%]

>1000

400

200

100

50

25

<10

y

z

x

z

01.55_

_

−−

−=RECEfict

TCCARLOSfictrel D

DD

k = 5Miner elementary

• Fx, Fz (My): ECE R 55.01 is much more severe than CARLOS TC

• Fy (Mx, Mz): CARLOS TC is much more severe than ECE R 55.01

uni-axial testing procedure leads to unrealistic damage distribution

Drel

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Multiaxial Test-Rig for Trailer Coupling Devices of Passenger Cars and Light Trucks at Fraunhofer LBF (Dmax=17kN)

Page 18

Spring/Damper Replacements

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Iteration Process at Test Rig (1)

Forc

e [k

N]

Time [s]

Desired Signal: Vertical Force FzResponse Signal: Vertical Force Fz

Iteration Number

Sta

tistic

s[%

]

1-Damage_Response, 3, Fx

2-Stats_ResponseMax, 3, Fx

3-Stats_ResponseMin, 3, Fx

4-Stats_RMSError, 3, Fx

432100 %

00 %

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Iteration Process Test Rig Using (2)

Frequency [Hz]

Pow

er-S

pect

ral-D

ensi

ty[k

N2 /H

z]

Desired Signal: Vertical Force FzResponse Signal: Vertical Force Fz

Forc

e [k

N]

Cycles

Desired Signal: Vertical Force FzResponse Signal: Vertical Force Fz

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Monitoring of Tests

Results:

100100100

112,26102,36 103,58

0

20

40

60

80

100

120

Fx Fy Fz

[%]

Damage of desired signalDamage of response signal

Dam

age

[%]

Page 22

Test Results – Failure at Rear Light House

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Test Results – Failure at Boot Bottom

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Test Results – Failure at Wheelhouse

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CARLOS TC – Summary and Perspective

• Development of safety-critical components requires consideration of service loading

• Legal requirement ECE R 55.01 does not take into account currentdurability sign-off tests of car manufacturers (service loads)

• CARLOS TC:- considers 3-D service loads- failures are similar to failures at proving-ground- reduces development loops with physical prototypes

• Planned: integration of CARLOS TC in ECE R 55.01

• LBF provides test facility according to CARLOS TC requirements

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Used Software-Tools

LMS.Tecware:signal processing, rainflow counting, calculation of damage impact

LMS.Tecware / RainEdit:editing of rainflow matrices, super-positioning of rainflow matrices

LMS.Tecware / CombiTrack:schedule of load modules (“optimized histogram”)

LMS.Falancs:fatigue assessment based on FEA (stress approach)

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Thank you for your kind attention!