Post on 14-Sep-2020
Prof. Dr.-Ing. habil. Egon-Christian von Glasner
Tire Mechanics
Lecture
Contents
0226 / 1103
1. Fundamentals2. Requirements and evaluation criteria3. Safety aspects4. Cost effectiveness5. Comfort6. Adhesion performance6.1. Influence of surface pressure6.2. Forces acting on tires6.3. Tires on dry road surfaces6.3.1. Free rolling wheel subjected to slip angle6.3.2. Straight ahead rolling wheel while accelerating and decelerating6.3.3. Combination of slip angle and slip6.4. Tires on wet road surface6.5. Tires on wintry/icy road surfaces
0229 /0903
Tire Design Fundamentals
Interior insulating layerBead
Bead reinforcement
Bead core
Sidewall
Carcass
Intermediate plyBelt
Shoulder Running surface
0227 / 0802
The Tire - A Compromise (1)
Good damping characteristics
Excellent ride comfort
Low rolling resistance
Minimal heat up
Excellent adhesion on wetroad surface
Good cornering stability
Large volume
Low inflation pressureObtuse cord angle
Increased inflation pressureAcute cord angleBelt type
Thin sidewallMixture with marginal damping
Transversely situated tread lugsFine profileFlat, broad running surface
Higher inflation pressureAcute cord angle
Longitudinally orientated profileLow height/width ratioBroadened rim width
Limited high speed capacityIncreased substructure loading
Reduced service lifeIncreased heat-upLess sufficient cornering stability
Moderate springing characteristicsBad road surface contactMinimal service life
Marginal sidewall stiffnessMarginal adhesion on wet roads
Marginal smoothnessMarginal service lifeIncreased running noise
Marginal ride comfortMarginal springing characteristics
Increased shoulder loading
Requirements Tire Design Measures Trend
0228 / 0903
The Tire - A Compromise (2)
Maximum service life
Operational safety at high speed
Rolling noise reduction
Driveability in winter
Off-roadcapacity
Increasing stiffness of running surfaceUniform surface pressure distribution
High-strength cord typesThin sidewallsAcute cord angleHeat resistant mixture
Circumferential-rib tread, no fine treadNo lateral cuttingRunning surface mixture with high damping
Massive bar winter tread profileSpikes
Big volumeLow inflation pressureMassive bar tread profileAdaptable carcass
Limited high speed capacityIncreased heat-upMarginal ride comfort
Flat spots after prolonged standstillMarginal ride comfort
Marginal adhesion when wet, snow and iceIncreased rolling resistance
Increased riding noiseDecreased service lifeLimited high speed capacity
Increased heat-upLimited high speed capacity
Requirements Tire Design Measures Trend
Safety
Economy
Maximum attainable comfort fordriver and load
0230 / 0903
System ”Wheel/Tire” - Evaluation Criteria
Primary criteria
0231 / 0903
System “Wheel/Tire” - Tire Characteristics Influencing Safety
Safety criteria
Mechanical strength
Tire force fit
Adhesion on dry, wet and icy road surfaces, when decelerating and accelerating
Economic criteria
Service life
Rolling resistance
Dimension and weights
Tire/chain compatibility
0232 / 0903
System “Wheel/Tire” - Tire Characteristics Influencing Economy
0233 / 0903
Influence of Inflation Pressure and Load on the Service Life of a Tire
Prozentsatzdes Luftdrucks der Beladung
10
20
30
40
50
60
70
80
90
100
30 40 50 60 70 80 90 100 110 120 130 140 150
Lauf
leis
tung
%
74
%
Lauf
leis
tung
Prozentsatz
7074
100
Percentageof inflation pressure of load
Serv
ice
life
0234 / 0903
Influence of Inflation Pressure on Fuel Consumption of Commercial Vehicles
Incr
ease
d fu
el c
onsu
mpt
ion
(mea
n va
lues
)
Vans and light trucks (<7,5 t) Heavy trucks (>7,5 t)Reduction of inflation pressure
Results from test vehicles 1996-2002
··
···
0235 / 0903
System “Wheel/Tire” - Tire Characteristics Influencing Ride Comfort
Comfort criteria
Springing behavior
Response- and re-aligning behavior
Uniformity and running noise
Ease of assembly
0373 / 0802
Radial Spring Stiffness of a Commercial Vehicle Tire
Spring stiffnessTire:
Slip angle
0236 /0903
Adhesion between Tire and Road Surface - Scope of Testing
- Straight-ahead rolling wheel while
accelerating and decelerating
- Tire on wintry/icy road surface
- Free rolling wheel under slip
- Forces acting on a tire- Influence of surface pressure
- Tire on wet road surface
- Tire on dry road surface
- Combination of slip angle and slip
Measuring axle
0237 / 0903
Tire Test Truck
0238 / 0903
Tire Test Stand
0239 / 0903
300
Coefficient of Adhesion in Dependence of Surface Pressure
0
1
100 300N/cm2
Surface pressure pm
N/cm2200
Commercial vehicles
Coe
ffici
ent o
f adh
esio
n k
Dry road surface
Passengercars
0,5
0240 / 0903
Forces Acting on Tires
B kN braking force f mm tire rebound forceM Nm re-alignment torqueMγ Nm camber torquen mm distance between resulting
force and vertical axispi bar tire inflationQ kN resulting forceR kN wheel loadrdyn mm dynamic tire radiusS kN lateral forcev0 km/h road speedα ° slip angleβ ° angle of resulting force Qγ ° camber angle
B SR
v0
R
B
QS
rdyn
Unit TermDimension
0241 / 0903
Tire Characteristics According to GoughLa
tera
l for
ce
Wheel load R
Re-aligning torque
Dry road surfaceSlip angle
Caster
0374/ 0903
Late
ral f
orce
Wheel load R = 40 kNDry road surface
Lateral Force/Slip Angle Characteristics
Speed = 40 km/h Inflation pressure = 7,75 bar
11 R 22.5
Slip angle
0375/ 0903
Influence of Camber Angle on Lateral Forces
Late
ral f
orce
Wheel load
Camber angle
Dry road surface
Slip angle
0376/ 0903
Influence of Tread Conditions on Lateral Forces
Tread conditionLa
tera
l for
ce
Dry road surface
Slip angle
0,1 0,2 0,3 0,4 0,5Slip λ
Bra
king
forc
e B
Michelin XZA
11 R 22.5pi = 7,75 barv0 = 60 km/h
0
10
20
30
40
kN
Wheel load R = 40 kN
0392/ 0903
Braking Force/Slip Characteristics
Dry road surface
0377/ 0903
Influence of Tire Inflation Pressure on Lateral and Braking Forces
Dry road surface
Bra
king
forc
e
Late
ral f
orce Wheel load R
Tire inflation pressure piTire inflation pressure pi
Slip Slip angle
Dry road surface
Wheel load
0378/ 0903
Influence of Camber Angle on Braking Forces
Tendenz
1 2 3 4 5 6 7 8 9 10
Schlupf
Bre
msk
raft
Sturzwinkel nimmt zu
0°
5°
Slip λ
Bre
msk
raft
B
5°
0°Tendency
Bra
king
fo
rce
Camber angle increases
Slip angle increases
Michelin XZA11 R 22.5
pi = 7,75 barR = 40 kN
v0 = 60 km/hdry road surface
0,1 0,2 0,3 0,4 0,5 Slip λ
Bra
king
forc
e B
0
10
20
30
40
kN
0379/ 0903
Influence of Slip Angle when Braking
0253 /0903
The Principle of Cooperation between Circumferential Forces, Lateral Forces, Slip Angle and Slip
Lateral force
Slip angleBraking force Driving force
Slip
Braking force
Michelin XZA
11 R 22.5pi = 7,75 bar
R = 40 kNv0 = 60 km/h
dry road surface
Braking force B
Late
ral f
orce
S
Slip angle α
0380/ 0903
Measured Tire Characteristics
Michelin XZA
11 R 22.5pi = 7,75 barv0 = 60 km/h
dry road surface
Braking force B
Late
ral f
orce
S
Wheel loadR = 40 kN
0381/ 0903
Envelope Curves for Maximum Possible Adhesion of a Tire with Wheel Load as Parameter
Contact Area of a Tire on a Wet Road Surface
0255 / 0903
Direction of traveln
Contact area for a dryroad surface
Water wedge
Contact area fora wet
road surface
Water depth increases
Slip(Slip angle)
Speed Tread depth
Bra
king
forc
e (L
ater
al fo
rce)
Bra
king
forc
e
Bra
king
forc
e0256 / 0802
Influence of Water Depth on Braking Force/Lateral Force - Characteristics
Water depth increases Water depth increases
0393 / 0903
Dependence of Adhesion Limits from Water Depth
Lateral force
Dry road surface
Water depth (mm) increases
0.5
1,01,5
Braking force B Driving force A
C
EB
E
C
B
F
E
DA
B
CF
ED
C
A B
0
0,1
0,2
0,3
0,4
0,5
Produkte A, B, C, D, E, F bestimmter Reifenhersteller
Kra
ftsch
lußb
eiw
ert
k
Dimensionen:175 R 14 185 R 14 215 R 14205 R 14
∆ ≈ 300 % ∆ ≈ 300 %B
F
E
Products A, B, C, D, E, F of certain tire manufacturers
Coe
ffici
ento
f adh
esio
nk
Test Conditions: Water depth 2mm, Speed 100km/h, Wheel load 2kN
Tire sizes:175 R 14 185 R 14 205 R 14 215 R 14
∆ ∼ 300 % ∆ ∼ 300 %
0258 / 0903
Aquaplaning Performance of Tires made by Different Manufacturers
0259 / 0903
Influence of Ice Temperature on Lateral Force Capacities
Eisoberflächentemperaturnimmt zu
Schräglaufwinkel
Seite
nkra
ft
-4°
-2°
-1°
0°
Geschwindigkeitnimmt zu
Eisoberflächentemperatur (fallend
Seite
nkra
ft
)
Ice surfacetemperature increases
Late
ral f
orce
S
Slip angle a
- 4°
- 2°
- 1°- 0°
Ice surface temperature ϑ
Road speed increasesLa
tera
l for
ce S