Fatigue Failures of Vehicle Components · Durability Life Curve Probability of Survival P s Design...
Transcript of Fatigue Failures of Vehicle Components · Durability Life Curve Probability of Survival P s Design...
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Grub\Tokio-Oct2004.ppt 1
The Automobile Industry in Japan and Germany-ives in the Age of Globalization
12th October 2004 -Tokyo Strategic Challenges and New Perspect
Fatigue Failures of Vehicle Components
by
Vatroslav Grubisic
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Grub\Tokio-Oct2004.ppt 2
1. Introduction
Criteria for the design, classification of vehicle components and product liability
requirements.
2. Influences for the failures
2.1. Design and service loading
2.2. Material and manufacturing
2.3. Usage conditions (Assembly, Environment)
The individual influences will be discussed on examples
and the means to avoid failures presented.
3. Conclusions
Requirements concerning the procedures for the design validation of vehicle
components.
The Automobile Industry in Japan and Germany-Strategic Challenges and New Perspectives in the Age of Globalization
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Grub\Tokio-Oct2004.ppt 3
Recalls in Car Industry
Source:German Traffic Office 2004
DIA
732
9e
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Grub\Tokio-Oct2004.ppt 4
Automotive Failures-Occurence and Costs
1
10
100
100080% of Failures Originated
Design Failures
Production Failures
Failure Detection*Failure Occurence
Cos
t pe
r Fa
ilure
Failu
re P
roba
bilit
yD
istr
ibut
ion
* After study Daimler Chrysler/Fraunhofer Society-IPT
Generalized Overview
DIA
729
0e
DEVELOPMENT MANUFACTURING ASSEMBLY USAGE
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Grub\Tokio-Oct2004.ppt 5
Classification of Components Concerning Reability RequirementsD
IA 7
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Grub\Tokio-Oct2004.ppt 6
Relation between Operational Stresses and Durability Life
Durability Life (log)
Stre
ss A
mpl
itude
Sa
orS a
SaSa
Ni = Nx (Sa,x / Sa,i)k
DIA
732
2e
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Grub\Tokio-Oct2004.ppt 7
Wheel/Hub Assembly of Commercial Vehicles with Drum Brakes
Hub
Bearing
Spindel
Brake Drum
Bolts
Wheel
1
2
3
4
5
6
DIA
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2e
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Grub\Tokio-Oct2004.ppt 8
Influence of Wheel Design on Hub StressesLoad Condition: Cornering
Aluminum Wheel Steel Wheel
Wheel22.5 x 9.00
Steel Wheel
Aluminum Wheel
Measuring PoinRe
lativ
e St
ress
Am
plitu
des
4
DIA
731
7e
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Grub\Tokio-Oct2004.ppt 9
Fatigue Fractures on Trailer HubsWheel: 22.5 x 11.75; Tyre: 385/65R22.5 Bridgestone; Wheel rated load: Fz,stat = 55 kN
Fracture in Biaxial Wheel/Hub Test FacilityLoad Programme „Eurocycle“Test Life ≈ 7 000 kmFracture after ≈ 200 000 km Service usageD
IA
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Grub\Tokio-Oct2004.ppt 10
Fatigue Fracture on Cast Hubs for Commercial Vehicles(Nodular Iron GGG 50)
DIA
388
5e
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Grub\Tokio-Oct2004.ppt 11
Truck OverloadedD
IA 3
885e
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Grub\Tokio-Oct2004.ppt 12
Measurements on roads in Hubei – Province (China)
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Grub\Tokio-Oct2004.ppt 13
Measuring VehicleD
IA
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Grub\Tokio-Oct2004.ppt 14
Pothole Test Track MAO JIAND
IA
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Grub\Tokio-Oct2004.ppt 15
Comparison of Test Spectra (Lt = 15 000 km) Hub, Area Gage 3D
IA
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Grub\Tokio-Oct2004.ppt 16
Influence of Design Spectra on Required Design Modifications
Damage Relation: D China ≈ 5 D Europe
Design Life Relation: L China ≈ 1/5 L Europe
Required Design Modifications
t China = t Europe ⋅nk
1
Europa
China
DD ⋅
t – thickness
k – slope of S-N-Curve
n - ratio of Loading mode
n = 2 (pure bending)
n = 1 (pure tensile/compession)
Required thickness for China compared to Europe for the same operational life and unchanged design of the wheel hub (n = 1.8, k = 7) for hub manufactured from nodular iron:
14.1tt
Europe
China ≈
e.g. from t0 = 12 mm to tnew = 13,7 mm..
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Grub\Tokio-Oct2004.ppt 17
Proof Test in Biaxial Test Facility Load Program CHINACYCLE D
IA
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Grub\Tokio-Oct2004.ppt 18
Fatigue Damage on a Cast Nodular Iron Hub for Dual WheelsD
IA 7
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Grub\Tokio-Oct2004.ppt 19
Classification of Allowable and Non-Allowable Pores in Nodular Cast Hubs (GGG 50)
c. Non-allowable outer pore in bearing seat area
b. Non-allowable flange shrinkage
Bearing seat
DIA
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Grub\Tokio-Oct2004.ppt 20
Areas of Shrinkage and Porosity on Cast Hubs for Commercial Vehicles
DIA
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Grub\Tokio-Oct2004.ppt 21
Allowable Shrinkage and Porosity on Highly Stressed Areas of Nodular Iron Hubs for Commercial Vehicles
DIA
731
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Grub\Tokio-Oct2004.ppt 22
Operational Stresses (Cornering) and Fracture Modes on Steel Wheels
DIA
730
1e α = angle of rotation0° corresponding to load input
x σr = radial stress• σt = tangential stress
σe = equivalent stressσe,3 ≤ 0,95 σe,2
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Grub\Tokio-Oct2004.ppt 23
Fatigue Crack on Welding between Disc and Rim
rim
disc
DIA
730
2e
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Grub\Tokio-Oct2004.ppt 24
Fatigue Cracks on Wheels with Large Rims (>7 inches) and Low Profile Tyres Operational Usage 60.000 – 100.000 km
Fracture Initiation Fracture Initiation
Fracture Initiation Fracture Initiation
Wheels: 8J x 17; 9,5 x 16 (240 TR 415); 10,5 x 18
Tyres: 245/40 ZR 17 280/45 VR 415 295/35 ZR 18
8J x 17 9,5 x 16
DIA
733
6e
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Grub\Tokio-Oct2004.ppt 25
Procedure for Pre-Loading of Wheels for Durability Approval
Static Pre-Loading:Vertical Force: Fv = 2,5 ⋅ Fv,statTyre pressure: pl = 0,6 ⋅ pl,nHalf tyre width (inside section)Obstacle radius r = 12 cm
cracked section
Fatigue Crack after validation test
Plastic deformation on rim strain gauges
Wh
eelf
orc
es
Strain ε 1000 µm/mPlastic deformation: ∆D = 0,9 mm
DIA
729
8e
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Grub\Tokio-Oct2004.ppt 26
Fatigue Cracks at Durability Approval on Wheels after Pre-LoadingD
IA 7
297e
_2
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Grub\Tokio-Oct2004.ppt 27
Influence of the Rim Design on Plastic Deformation and Durability
*
DIA
729
9e
* After Preloading: Fv = 2.5 · Fz,stat; pl = 0.6 · pl,n
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Grub\Tokio-Oct2004.ppt 28
Fracture of Washer (1), Hub (3) and Drive Shaft (2)
1 1 2 3
3 2
DIA
731
9e
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Grub\Tokio-Oct2004.ppt 29
Assembly of Drive WheelD
IA 7
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Grub\Tokio-Oct2004.ppt 30
Fatigue Failure of Drive Wheel Assembly
Washer1
Spindle End2
Hub3
DIA
734
2e
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Grub\Tokio-Oct2004.ppt 31
Steering-Knuckle Arm
Section A-B
Ball Pin
Track Rod Force
DIA
733
7e
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Grub\Tokio-Oct2004.ppt 32
Typical Cracks on Steering-Knuckle Arms
rust out
corroded
DIA
733
8e
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Grub\Tokio-Oct2004.ppt 33
Design Load Spectrum and Test Results with corroded Steering-Knuckle Arms
Result of tests with36 specimens in usage5 to 8 years and 32.000 to 129.000 km
DIA
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9e
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Grub\Tokio-Oct2004.ppt 34
Reliability Requirements for Safety Components
σa, 50%
Sa,max
Scatter of Allowable Stresses
Durability Life CurveProbability of Survival Ps
Design SpectrumProbability of Occurence Po ≤ 1 %
Design LifeTheoretical Probability ofFailure PF ≤ 10-3 or PF ≤ 10-4
Failure RateScatter of Operational Stresses
LD
50%
Ps = 90% or 99%
Life (log)
Stre
ssA
mp
litu
des
Sa
(lo
g)
Sa,50%
Safety FactorSF=σa,50% / Sa,50%≈1,7 or 2,2
Operational LifeDIA
729
6e
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Grub\Tokio-Oct2004.ppt 35
Realibility Requirements at Durability Life Approval
Durability Life (log)
LT – Required test life Lt = Lp· RF
( )( )n4/1NF T/1R =
TN = L90%L10%
n = number of tests
DIA
729
6e
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Grub\Tokio-Oct2004.ppt 36
CODEX HAMMURABI (18 Century b.C.)
• If the wall of a house tumbles down, the house builder must repair it with a stronger wall on his own cost.
• If the house collapses because it is not properly built and his owner is killed, the house builder will be killed, too.
DIA
729
6e
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Grub\Tokio-Oct2004.ppt 37
The Automobile Industry in Japan and Germany-Strategic Challenges and New Perspectives in the Age of Globalization
12th October 2004 -Tokyo
In every development a certain amount of risk reamains. If we try to
eliminate risks completely, it would be a totally unrealistic goal. But we
have to take into account in the approach we apply to determine the
operational strength and durability, whether or not a safety item is
under consideration and to what degree the function of vehicle is
influenced by possible failure. For such cases the procedures we apply
have to guarantee the whole functionability under operational
usage and we are responsible for the methods we apply to prove
it.