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1. RetMrt No,
:Z
G
... _ .. Accouion No.
FHW AJTX-90+ 1190-2F
4
Title ond Sublitle
TRUCK
TIRE PAVEMENf CONTACf
PRESSURE
DISTRIBLmON CHARACTERISTICS FOR THE BIAS GOODYEAR 18-22.5,
THE RADIAL MICHELIN 275 80R/24.5, THE RADIAL
MICHELIN
255nOR(22.5, AND THE RADIAL GOODYEAR 11
R24.5 TIRES
Rafael
F.
Pezo, Kurt
M.
Marshek, and
W.
R.
Hudson
9.
Porformint Orgoniaotion
N - •
•• A-.reaa
Center
for
Transportation Research
The
University
of
Texas at Austin
Austin, Texas 78712-1075
TECHNICAl. REPORT STANOARO TITLE PAGE
3.
RoctJIIont' • Cotolot No.
S. Report Dote
September 1989
6. Performi t
Orgoru zotion Cod•
8. Performong Orgoni&atio Report No.
Research Report 1190-2F
10. Work
Unit No.
11. Controct or Gront No.
Research Study 3-8-88/9-1190
h : ; - - ; : - :- : - - : - - : - - - : :- - - : - - : - : - - : - - - - - - - - - - - - - - - - - -113. Typo ol Report ontl Period Covered
12.
SpOI'Iaorint At..,CY
N - •
...... Adore
Texas State Department of Highways and Public Transportation
Transportation Planning Division
Final
P. 0. Box 5051
Austin, Texas 78763-5051
15.
Suppl-ontory
Not••
Study conducted
in
cooperation with the
U. S.
Department
of
Transportation, Federal Highway Administration.
Research Study Title: Tire Contact Pressure Distributions
16. Abatroct
This report presents the results ofan experimental investigation into the contact areas and tire contact pressure
distributions produced by statically loaded truck tires. For this report, the bias Goodyear 18-22.5 LR-H tire, the
radial Michelin 275/SOR/24.5 LR-G tire, the radial Michelin 255nOR/22.5 LR-G tire,
and
the radial Goodyear
11R24.5
LR-G
tire were tested.
The testing consisted of making contact pressure and contact area prints at the interface between the tire and a
steel plate
at
different wheel loads and tire inflation pressures. The pressure prints were produced using Fuji prescale
film. The Fuji prescale film produces color variations, when pressure is applied to it,
in
such a way that darker
pigmentation is produced in zones of higher pressure. The variations
in
color intensities of the Fuji film prints are
related to contact pressure values produced for the
fllm
color calibration curve. Then, by digitizing the images and
using computer software developed exclusively for this project, the tire contact pressure distributions were
determined. The proportions of contact
area
covered
by
the various pressure ranges were computed
and
compared in
order
to
observe the patterns and
to
estimate the significance of high contact pressures.
The contact
area prints were made by applying ink
to
the tire and pressing
the
tire over a white paper that
covered the steel plate. The ink prints have only one color and were used for calculating the tire-plate contact areas.
Also, the side tire movements were measured for the tires during testing to allow other researchers to relate
subsequent theoretical studies to our experimental results.
This report also proposes mathematical models for
(1)
estimating the tire contact area based on the relative
area value (ratio
of
wheel load over inflation pressure) and (2) estimating the tire vertical stiffness based on the tire
contact
area
17
K. .
Word•
tire pressures, truck tires, contact
area,
contact pressure
distributions, axle loads, pavements, side tire
movements, tire deflections, tire vertical stiffness
11
Dl• l l luti•
St.._
..
No
restrictions. This document is available to the
public through the National Technical Information
Service, Springfield, Virginia 22161.
19. Security Clouif. (of lhl• r , ._t) ». S.writy Cl•••lf•
(of
tt.l • . . .
21. No.
of Pogo•
22.
Price
Unclassified
Unclassified
56
Fom
DOT
F 1700.7 c•·••J
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TRUCK TIR PAVEMENT CONTACT PRESSURE DISTRIBUTION
CHARACTERISTICS FOR TH BIAS GOODYEAR 18-22.5
TH
RADIAL MICHELIN 275/SOR/24.5
TH RADIAL MICHELIN 255/70RI22.5
AND TH RADIAL GOODYEAR 11R24.5 TIRES
by
Rafael F Pezo
Kun
M
Marshek
W
R Hudson
Research Report Number 1190-2F
Research Project 3-8-88/9-1190
Tire Contact Pressure Distributions
conducted for
Texas State Department of Highways
and
Public Transportation
in cooperation with the
U.S. Department of Transportation
Federal Highway Administration
by
the
CENTER FOR TRANSPORTATION RESEARCH
Bureau
of Engineering Research
THE UNIVERSITY OF TEXAS AT AUSTIN
September 1989
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The contents of this report reflect the views of
the
authors
who
are responsible
for the facts
and
the
accuracy
of
he
data presented herein. The contents
do not
necessarily
reflect
the
official
views
or policies of
he
Federal
Highway
Administration.
This
report does not constitute a standard
specification or regulation.
ii
There was no invention or discovery conceived or first
actually
reduced to
practice
in
the course of or under
this
contract including any art method process machine
manufacture design
or composition of
matter
or
any
new
and
useful
improvement thereof
or
any variety of plant
which is or
may e
patentable
under the
patent laws of the
United
States of
America
or any foreign country.
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PREF CE
This
is
the second of two reports which describe work
done on Project 1190, Tire Contact Pressure Distribu
tions. This study was conducted at the Center for Transpor
tation Research (CTR), The University of Texas at Austin,
as part of a cooperative research program sponsored
by the
Texas State Department of Highways
and
Public Transpor
tation.
Many people contributed toward
the
completion of this
report. Thanks are expressed
to
Dr. Tom Tielking
for
his
input,
to
Mr. Larry Walker of Walker Tire Company
for
providing the tires,
to
Ms. Peggy Johnson,
and to
CTR
personnel especially Lyn Antoniotti and Carl Bertrand.
We acknowledge their contributions and greatly appre·
ciate their efforts
in
making this a successful project.
September
1989
Rafael
F.
Pezo
Kurt
M.
Marshek
W. R. Hudson
LIST
OF REPORTS
Report
No.
1190-1, Truck Tire-Pavement Contact
Pressure Distributions for Super Single 18-22.5
and
Smooth
11R24.5 Tires,
by
Rex William Hansen, Carl Bertrand,
Kurt
M.
Marshek, and
W.
R.
Hudson, presents experimental
data on the effect of tire inflation pressure and static wheel
load on contact pressure distributions for the bias Goodyear
18-22.5 and the smooth radial Armstrong 11R24.5 tires.
July
1989
Report No. II90-2F, Truck Tire Pavement Contact
Pressure Distribution Characteristics for the Bias Goodyear
18-22.5,
the
Radial Michelin 275/80R/24.5, the Radial
Michelin
255nOR/24.5
and the Radial Goodyear 11R24.5
Tires,
by
Rafael F. Pezo, Kurt
M.
Marshek, and W. R.
Hudson, presents experimental data
on the
effect of
tire
inflation pressure and static wheel load
on
contact pressure
distribution, contact area, tire deflections,
and
tire vertical
stiffness. September 1989.
BSTR CT
This report presents the results o an experimental
investigation into
the
contact areas and tire contact pressure
distributions produced by statically loaded truck tires. For
this report, the bias Goodyear 18-22.5 LR-H tire,
the
radial
Michelin 275/80R/24.5 LR-G tire, the radial Michelin 255/
70R/22.5 LR-G tire, and the radial Goodyear 11R24.5 LR-
G tire were tested.
The testing consisted of making contact pressure and
contact area prints at the interface between the tire and a steel
plate at different wheel loads and
tire
inflation pressures.
The pressure prints were produced using Fuji prescale film.
The Fuji prcscale film produces color variations, when
pressure
is
applied
to
it, in such a
way
that darker pigmenta
tion
is
produced
in
zones
o
higher pressure. The variations
in
color intensities of
the
Fuji film prints are related
to
contact pressure values produced
for
the
fllm
color calibra
tion curve. Then,
by
digitizing the images and using com
puter software developed exclusively for this project, the tire
iii
contact pressure distributions were determined.
The
propor
tions
o
contact area covered
by
the
various pressure ranges
were computed and compared
in
order
to
observe the pat
terns and
to
estimate the significance
o
high contact pres
sures.
Thecontactarea prints were made
by
applying
ink to
the
tire and pressing the tire over a white paper that covered the
steel plate. The ink prints have only one color and were
used
for calculating the tire-plate contact areas. Also, the side tire
movements were measured for the tires during testing
to
allow other researchers
to
relate subsequent theoretical
studies
to
our experimental results.
This report also proposes mathematical models for (
1)
estimating the tire contact area b sed on the relative area
value (ratio of wheel load over inflation pressure) and
2)
estimating
the
vertical stiffness based on
the
tire contact
area.
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SUMM RY
The
rate
of deterioration of highway pavements over
the
last 50 years has
been
accelerating.
During this
time, legal
truck sizes, weights, wheel loads and tire inflation pressures
have
increased. This report describes a study
which
seeks to
measure actual tire-pavement contact pressure distributions,
in
order
to
provide pavement designers with estimates of tire
pressure for
use
in studies of pavement deterioration and to
assist legislators
in
developing legislation regarding tire
usage.
This report presents
the
results of an experimental study
involving several truck tires statically loaded against a steel
plate. The bias Goodyear 18-22.5 LR-H super single tire,
the radial Michelin 275/SOR/24.5 LR-G tire, the radial
Michelin 255170R/22.5 LR-G tire, and the radial Goodyear
11R24
.5
LR
-G
were tested and studied
for
this report. These
tires were chosen because they are popular for use on Texas
highways.
The testing consisted of making contact pressure meas
urements and contact area prints at the interface between the
tire and the support plate t different wheel loads and tire
inflation pressures. The pressure prints were produced using
Fuji prescale
film.
The Fuji prescale
film
produces a color
variation when pressure is applied to it, in
such
a way that
darker pigmentation is produced in zones ofhigherpressure.
The variations in color intensities of the Fuji
film
prints are
related to actual contact pressure values produced for the
film color calibration curve. Then, by digitizing the images
and using computer software developed exclusively
for
this
project, the tire contact pressure distributions were deter
mined. The proportions of contact area covered by the
various pressure ranges
were
computed and compared in
order to observe the patterns and to estimate the significance
of high contact pressures.
The contact area prints were made by applying ink to the
tire and
pressing
the tire
over a
white
paper that covered the
steel plate. The ink prints have only one color and were
used
for calculating the tire-plate contact areas. Also, the side tire
movements were measured during testing to allow other
researchers to relate subsequent theoretical studies to our
experimental results.
This report also proposes mathematical models
for 1)
estimating the tire contact area based on the relative area
value (ratio of wheel load over inflation pressure) and 2)
estimating the tire vertical stiffness based on the tire contact
area
The conclusions from this project canbe summarizedas
follows:
1)
for bias truck tires the shape of the contact area
is generally circular with an oval tendency, while for radial
truck tires the shape is consistently rectangular; 2) in
general,
for
a constant tire inflation pressure, as the wheel
load increases, the proportion of contact area increases
for
higher contact pressure ranges and decreases for lower
contact pressure ranges;
(3)
similarly, for a constant
wheel
load, as the tire inflation pressure increases,
the
proportion
of contact area increases for higher contact pressure ranges
and decreases
for
lower contact pressure ranges.
IMPLEMENT TION ST TEMENT
The results of this project provide tire contact areas, tire
contact pressure distributions, and proportions of contact
area covered by different pressure ranges for truck tires at
several inflation pressures and wheel loads. These relation
ships can be used to evaluate the effects of truck
tire
inflation
pressure
and
axle load
on
the structural capacity of pave-
iv
ments. The results can help to clarify many pressing prob
lems, such as rutting, shoving, etc. Such information and
evaluation leads to changes
in
methods employed
in
current
pavement design
to
improve
the
performance of pavements
and c n also assist legislators in developing legislation
regarding allowable tire pressures and related issues.
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T BLE OF CONTENTS
PREFACE ............................................................................................................................................. 111
LIST OF REPORTS . . .. .. .. ........ . . ..... .. . . . .... .... .. . . .. .. .. .. ..... .... ...... .... .. ...... .. .... .. ... . ..... .. .. . . .... .. . . . . .. ut
ABSTRACT........................................................................................................................................... iii
SUMMARY
........................................................................................................................................... iv
IMPLEMENTATION STATEMENT...........................................................................................................
V
CHAPTER 1.
INTRODUCTION
Backgrolllld
......................................................................................................................................
Objectives .......................................................................................................................................
.
Scope
and Organization of the Study .....................................................................................................
Research Approach ............................................................................................................................
CHAPTER
2.
REVIEW OF
TIRE CONTACT PRESSURE
STUDIES
Literature Survey................................................................................................................................ 3
Tire Pavement
Interface Pressure
Characteristics................................................................................. 3
Tire Contact Pressure and Its Effect on Pavement Performance...... ...... ...... ...... ...... ..... ...... ...... ...... ...... ... 3
Future Trends in Tire Types .
.
.. .
.
..
..
.
.
.
.
.
.
....
.. ..
.. . .
..
..
..
. .. ..
..
.. . . .. .
.
.
.
..
.. ..
.
.
.
.
. .. . 4
Conclusions...................................................................................................................................... 4
CHAPTER
3. EXPERIMENTAL
PROCEDURES
Experimental Parameters...................................................................................................................... 6
Tires.......................................................................................................................................... 6
Loads and Inflation Pressures.......................................................................................................... 6
Experimental Procedure
. . .. . . .. .
.
..
..
. .
..
.
.
....
.
.... ..
.. ..
..
.. ..
. . .
.
..
..
.. ..
..
. . . . . .
..
.
.
.
.
. 6
Mounting
the
Tire........................................................................................................................ 6
Testing
the
Tire and Producing Calibration Squares............................................................................. 6
Analysis of the Fuji
and
Ink Prints.......... ............ ............ ............ ............. ............ ............ ............ ... 9
Presentations of Results . .. . . .. . . .. .. . . .. .. . . .. .. .. .. .. . . .. .. .. .. . . .. .. .. .. .. .. . . .. .. .. .. . . .. . . .. .. . ... . .. . . . 9
CHAPTER
4. EXPERIMENTAL RESULTS
Bias Goodyear
18 22.5
LR H Super Single Tire ......... ......... ......... ......... ......... ......... ......... ......... ......... ...
10
Radial Michelin 275/SOR/24.5 LR-G Tire ..............................................................................................
10
Radial Michelin 255/70R/22.5 LR-G Tire ............................................................................................. . 11
Radial
Goodyear l1R24.5 LR G
Tire
..................................................................................................... 16
CHAPTER 5. DISCUSSION AND ANALYSIS OF RESULTS
Tire
Contact
rea 39
Discussion of Results . ... ..
..
........
.. .. .. .. ..
... .
. ..
..... .
.
.. .. .... .
.
.. .... ....
.
.. . . . . .
.
. .. . ... . . . . .
.
.. .
. ..
39
Analysis of Results ..
..
.
.
..
.. ..
.. .... ...
.
. . .
. ..
.. .
.
....... ............ ... ..
..
..
.. ..
..
..
.. .
. ..
. .
.. ..
..
..
.. .... . .
.. ..
.
. ..
.
.
39
Tire Contact Pressure Distributions .. . . .. .. .. .. .. .. .. .. . . . ....... .. . .. . . . . . .. .. ... . . . . . .. .. .. . . .. . . . . 40
Proportions of Contact Area... ........... ........... .......... ........... ........... ........... .......... ........... ........... ........... .. 40
Discussion.................................................................................................................................. 40
Analysis..................................................................................................................................... 40
v
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Comparison Between the Tires 4
Load Dist ribution Along the Tread Width 42
Tire Vertical Stiffness 42
Discussion 42
Analysis
of
Results 42
CAHPTER 6 CONCLUSIONS AND RECOMMENDATIONS
Conclusions 44
Recommendations 44
REFERENCES 45
APPENDIX A EXPERIMENTAL AND ANALYTICAL PROCEDURES FOR
DETERMINING TIRE CONTACT PRESSURE DISTRffiUTIONS 47
APPENDIX B SIDE TIRE MOVEMENT DATA 48
vi
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BACKGROUND
CHAPTER l INTRODUCTION
OBJECTIVES
The rate of highway pavement deterioration has been
observed to
be
accelerating over
r.he
last 50 years (Refs 26
and
27). A variety of factors
have
been identified as contrib
uting to
r.he
accelerated
rate
of pavement damage, including
increased truck weights, sizes, wheel loads, and tire inflation
pressures. Tire contact pressure distribution and its eroding
effect on r.he pavement has, until recently ,received very little
attention. It
is now
increasingly recognized r.hat the tire
pavement contact pressure distribution
is an
important
fac-
tor
in
pavement deterioration and, consequently, a major
consideration
in
new pavement
and
rehabilitation design.
As the
cost of
fuel has
increased,
r.he
trucking industry
has
sought ways to economize its operations. One approach
was
an
attempt to improve truck gas mileage
by
reducing
rolling resistance through the use of higher tire inflation
pressures. This increased tire pressure has presumably
caused an increase in the rutting and fatigue failures of
asphaltic concrete pavements.
The AASHO Road Test was conducted and analyzed
using 1958-1960 truck characteristics. Since r.hen tire pres
sures have increased, and their effects
on
fatigue damage
t
pavements are not documented. AI .hough pavement design
ers have
in
the past attempted to counteract
r.he
effects of
increased loading through improved pavement and geomet
ric designs, the rate of pavement deterioration continues
t
increase (Refs 6,
11, 15,
and 23). The actual pavement
loading mechanisms and
r.heir magnitudes must be identi
fied
in
order to estimate real pavement perfonnance.
Current pavement design assumes a unifonn pressure
distribution equal to r.he tire inflation pressure loaded over a
circular tire contact area. Research has clearly demonstrated
that r.he actual pressures are dependent on the user vehicle
operating characteristics, tire type, wheel load, and tire
inflation pressures.
Severa attempts have been made t detennine tire
contact pressure distributions. Tielking (Ref 15), for ex
ample, developed a fmite element model of tires to estimate
stresses and strains
in
pavements when
r.he
tire is loaded and
inflated
t
different
air
pressures. However, none of
r.hese
studies has been related to and calibrated wir.h experimental
measurements.
At The University of Texas at Austin, contact pressure
distributions of a statically loaded tire have been experimen
tally detennined (Refs 1, 2, and 25). This has been possible
through a system which provides numerical pressure values
for
r.he
contact area and two-dimensional color spectrum
graphics that clearly focus on
the
variations
in
contact
pressures
and
show
r.he
locations
of he peak
pressure values.
The objectives of r.he study described in this report arc
(
1)
to establish pressure distributions for four different types
and sizes of tires
in
contact with a steel plate, (2)
t
provide
data
t
assist pavement designers
in
estimating the increas
ing rate of highway deterioration, and (3) to provide legisla
tors with infonnation for use
in
developing legislation re-
garding tire pressure limits and usage.
SCOPE
AND
ORGANIZATION
OF THE
STUDY
Chapter 2 contains a brief summary of related studies
dealing
wir.h
r.his
subject. A description
of r.he
experimental
procedure used
in
r.his project
is
presented
in
Chapter
3.
Chapter 4 contains the experimental results, including tire
contact pressure distributions, contact areas, load distribu
tions across
r.he
tread width, and proportions of contact area
covered by different pressure ranges for the tires tested. A
discussion and
an
analysis
of r.he
results are presented
in
Chapter
5,
along with appropriate statistical analyses.
In
Chapter 6, conclusions and recommendations for future
research are presented.
RESEARCH APPROACH
To identify the contact area and pressure magnitudes,
static testing
was
perfonned at The University of Texas at
Austin
on
several tires at various inflation pressures
and
wheel loads. These tires were a bias Goodyear 18-22.5
LR-
H super single, a radial Michelin
275/BOR/24.5
LR-G, a
radial Michelin 255nOR/22.5
LR
-G, and a radial Goodyear
11R24.5 LR-G.
The experimental procedure consisted of four stages:
(1) mounting
r.he
tire, (2) testing the tire and producing
calibration squares,
(3)
analyzing r.he Fuji and ink prints, and
(4) presenting
the
results. Details of
r.he
experimental proce
dure can
be
found
in
Chapter 3
of
this report.
In genera , Fuji prescale
film
was the medium
used
t
capture the tire contact pressure distributions. This
is
the
film
used by Hansen, Chan, and Marshek
in
References
1, 2,
and
25.
The
Fuji prescale film was located between the tire
nd
r.he
steel plate. By applying different loads t r.he tire, the
Fuji prints were produced. The Fuji prints were r.hen scanned
and digitized using
an
Adage 3006Graphics system. Several
computer programs written exclusively for
r.his
project were
run
in
order to measure, analyze, and display
r.he
truck tire
contact pressure distributions.
The tire contact area and the applied wheel load values
obtained
from r.he
analysis
of r.he
Fuji prints were checked
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2
for consistency. Tire contact areas were estimated by pro
ducing ink prints and analyzing lhem. The applied wheel
loads were detennined using lhe computer programs and
compared wilh lhe actual applied loads used
in
testing. This
checking process enhanced lhe validity
o
lhe results.
The truck tire pavement contact pressure distributions
o
lhe four tested tires are presented in two ways,
in
Chapter
:
1) numerical p ~ s s u r maps and 2) two-dimensional
color pressure plots.
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CHAPTER 2 REVIEW OF
TIRE
CONTACT PRESSURE STUDIES
This chapter discusses the literature associated with tire
contact pressure disuibutions. Several technical publica
tions related to tire contact pressures, wheel loads, tire types,
and tire inflation pressures were reviewed. Descriptions
of
the tire-pavement interface pressure characteristics, their
effect on pavement life, and future trends in tire types are
presented below.
LITERATURE SURVEY
A literature search was conducted to determine the
existing state
of
knowledge relating to the project. The
reference collection of the Center for Transportation Re
search at The University of Texas
at
Austin, the Highway
Department libraries in various states, and o ther academic
libraries were among the sources
of
information for this
project. This section presents a review of several papers
addressing the problems of tire-pavement interface pressure
characteristics and tire contact effects
on
pavement life.
Tire Pavement Interface
ressure
Characteristics
In pavement design, it is frequently assumed that
(1)
the
tire contact pressure is equal to the tire inflation pressure, and
(2) the tire contact pressure is uniformly distributed over a
circular area. These assumptions are based on the idea that,
if
an inflated membrane is
in
contact with a flat surface, the
contact pressure at each point is equal to the membrane s
inflation pressure and the contact area is circular. Theoreti
cally, as well as experimentally, it has been demonstrated
that contact pressures are not uniform and con tact areas are
not circular. Models constructed with these assumptions are
hardly accurate because carcass stiffness as well
as
stiffness
in
the sidewalls prohibits equal pressure distribution in the
contact area Ref 20).
Lippmann and Oblizajek Ref 17) stated that tire pave
ment contact area is influenced by factors such as vehicle
speed, wheel load,
tir
inflation pressures, wheel camber,
steering, braking, vehicle suspension, and
tir
configura
tion. Tielking and Roberts Ref 15) described the mecha
nism whereby a tir transfers a wheel load to the pavement.
Tielking and Roberts stated that changes in either the wheel
load or the tire inflation pressure result in variations in actual
contact area.
Ginn and Marlowe (Ref 22) explained the characteris
tics of tire-pavement contact stresses, describing their
components and orientations. The stresses can be repre
sented by two components, one perpendicular and the other
tangent to the contact surface. This latter component may
also be subdivided into two sub-components, each lying in
the contact plane. One
of
the two sub-components is parallel
to the central plane
of
the tire and is called the longitudinal
3
stress component; the other, called the lateral stress compo
nent, is perpendicular to the central plane of the tire. In
general, these sub-components are ca lled shear components.
The shear components are created when an inflated tire
is deflected against the pavement, causing the doubly
curved surface of the tread to become a flat surface. When
the tire is vertically deflected against a flat surface, the
motion is restrained by friction between the tire and the
pavement, creating perpendicular horizontal shear compo
nents
of
contact pressure. However, when the tire rolls freely
without camber, the shear pressure is re-directed, due to the
superposition
of
an angular velocity on the tread surface.
Bonse and Kuhn (Ref 21) experimentally confirmed this as
early as 1959 by rolling a tire over a circular force-measuring
stud placed in a manhole cover.
Tielking and Roberts (Ref 15) believed that the magni
tude
of
the lateral shear is dependent on tire construction,
with the radial tires producing about one-half lower peak
pressure values than bias tires. They also believed that the
lateral shear pressure applies a much higher stress to the
pavement than does longitudinal shear pressure.
Tire Contact Pressure and Its Effect
on
Pavement
Performance
A pavement must provide
the
load-bearing surface for
which it is designed. This depends on the expected traffic
loads, density
of
traffic, and desired service life. The pave
ment must maintain an adequa te surface condition such that
t
is able to permit comfortable and safe driving within the
designated speed limits. The service life is dependant on the
loading the pavement receives. Traditionally, pavement
design engineers have been primarily concerned with only
the wheel loading effects, but, recently, research efforts have
also investigated environmental and traffic effects caused by
wheel loads and
tir
inflation pressures. References 4, 15,
18, 27, 28, and 29 discuss the stress and strain relationship
in an asphalt pavement system caused by wheel load and
inflation pressure.
In general, the literature shows that the major causes for
increases in pavement fatigue and rutting rates are increases
in wheel loads and
tir
inflation pressures.
For
example, van
Vuuren (Ref 4) analyzed various linear elastic pavement
structures under many combinations
of
wheel loads and
inflation pressures, using the Chevron computer program.
He attributed four types of pavement failure to high contact
pressure: (1) fatigue
of
the surface layer, (2) fatigue of
cement stabilized bases, (3) surface densification, and (4)
consolidation
of
the subgrade. Another researcher, Eisen
mann (Ref 27), states that pavement rutting is caused by
mechanical abrasion and is due to irreversible material
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4
deformations. These defonnations are mainly caused by
high tire contact pressure concentrations, which are
in
turn
caused
by
a change
in
wheel load and/or a change
in
tire
innation pressure. Papagianak:is Ref 18) likewise believes
that
the compressive strains at the top of
the
asphalt surface
are
dramatically affected
by
high tire inflation and contact
pressures.
Many researchers have addressed this growing prob-
lem,
the effects of tire contact pressures on pavement life.
References
5, 18, and 26
describe possible pavement-life
saving solutions. For example, Brown Ref 5), at a sympo
sium for high pressure truck tires, stated that, through
legislation and improved engineering, pavement life could
possibly be maintained and extended. The possible legal
measures
he
mentioned were
1)
placing legal limits
on
tire
pressures, 2) placing controls on the manufacture of high
pressure tires, 3) requiring approval by FHWA of any new
tire
carcass design, 4) requiring approval
for
any
new
suspension system considering tires as a component of the
suspension system), and 5) using tire inflation pressure as
a factor in setting truck user taxes.
Nine states have already implemented conditional pro
visions for the maximum wheel load as a function of the tire
inflation pressure Refs 6 and 16). These regulations are
generally expressed as two allowable loads per tire, one
for
inflation pressures below 100 psi and another
for
inflation
pressures above 100 psi.
The possible engineering improvements suggested by
Brown include 1) the use of more accurate pavement
structural design models, 2) possible development of better
binders and cements, and 3) emphasis
on
better quality
control and
mix
design criteria. These improvements, i
implemented, will help in estimating
the
pavement perfonn
ance and service life
in
a more reliable manner.
Future Trends n Tire Types
Pavement designers are concerned with future trends
in
tire types. For example, Papagianalcis and
Haas
Ref
18)
mentioned that inflation pressures, regardless of tire types,
are much higher than they were two decades ago. Yeager
Ref 19), based
on
the fact that radial tires have a demon-
strated higher wear
life,
predicted that
the
amount of radial
replacement tires would increase from
65
to 88 percent
within the next
10
years. Yeager also stated that
the
average
set of radial automotive tires currently serves
for
approxi
mately 39,000 miles before replacement some of the
new
designs are capable of 65,000 miles). Recently, with the
introduction to the market of the all-season radial tire,
traditional bias tires are being rapidly replaced.
Most experts agree that the popularity of radial tires
will continue to grow, particularly the all-season radials. The
all-season tire has proven
to be fuel
efficient and provides
good traction
on
wet and snowy roads. The all-season tire,
with
its improved perfonnance capability and lower profile,
has
become even more attractive.
Papagianak:is Ref 18} stated that tire manufacturers are
attempting to improve tire unifonnity and further reduce
rolling resistance
by,
modifying design and production
pro-
cedures. Rolling resistance has also been reduced by
in-
creasing inflation pressures. This trend will continue with
the
widespread
use
of low-profile tires and variable comfort
suspension systems.
Roberts Ref
3},
for example, used a tire inflation
pressure of
125 psi in his
model
to
estimate the behavior of
thin asphalt concrete surfaces on granular bases.
He
said
that. although 125 psi
may
appear high, representatives
from
various tire manufacturers indicate that within the next
years 1986-91)
tire
inflation pressures would continue to
rise,
to
nearly
150
psi.
He
believed that higher tire inflation
pressures resulted because increased
fuel
costs prompted the
trucking industry
to
attempt
to
reduce rolling resistance
and
thereby increase
fuel
economy. Therefore, the tire manufac
turers
have
responded
by
marketing both bias and radial tires
that operate at higher tire inflation pressures.
Zekoski Ref 23) believes radialization will continue
into applications that traditionally have been bias domi-
nated,
to
increase
fuel
economy e.g.,
on
school buses,
pick-
up trucks, and delivery trucks).
Zekoski lso addressed the possible impact of European
tires. There is a trend
in
Europe to manufacture tires having
higher load capabilities and inflation pressures
to
meet the
increasing regional legal load limits, which are higher than
those in the U.S. He believed that, as the global marketplace
continues to mature,
an
increasing number of these tires will
enter the United States, and the effect of these tires on
pavement life must
be
addressed.
CONCLUSIONS
From the literature review the following conclusions
maybe made:
1}
Wheel
load
and tir inflation pressure have a signifi
cant effect on pavement service life.
2} The major causes for the increase
in
pavement fatigue
and rutting rates are increases
in
the wheel loads and
tire inflation pressures.
3} Theoretically and experimentally
it
has been demon
strated that contact pressures are not unifonn and that
the contact area is not circular.
4)
Tire contact forces are nonnal stresses, and are longi
tudinal and lateral shear stresses.
5) Factors affecting contact pressure distributions
in-
clude speed, steering, tire camber, tire construction,
braking, inflation pressure, and wheel load .
6)
The
use
of radial tires will increase significantly,
replacing the bias tire market at a faster rate.
7) Improved engineering and increased legislation
may
reduce pavement rutting and fatigue caused by high
wheel
loads and
high
inflation pressures.
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These conclusions reinforce the need for the experi-
mental
determination of
the tir
contact pressure distribu-
tions since these pressure distributions have a major influ-
ence on pavement performance and service life As stated in
5
Chapter 1 this report addresses this need by testing several
popular tir s and presenting the variations of tire contact
pressures.
when a wheel load and/or a tire inflation pressure
changes
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CHAPTER3. EXPERIMENTALPROCEDURES
This chapter describes the experimental procedures
used
in
obt.aining tire pavement contact pressure distribu
tions
and
lists
the
experimental parameters which were
selected for measurement.
EXPERIMENTAL PARAMETERS
Fuji and ink: prints were produced for various
com
bina
tions of tires, wheel loads, and inflation pressures. The
parameters and the reasons for their selection are discussed
below. The experimental parameters are t.abulated
in
Table
3.1.
TABLE 3.1. TIRE EXPERIMENTAL
PARAMETERS
In
nation
In nation
Tire
Pressure
Loads
Pressure
Loads
Type
(psi)
.J 2L
(psi)
.J 2L
18-22.5 85 15,000 100 15.000
275 80R/24.5 95
6,000 110
6,000
95
8,000
110
8,000
255/70R/22.5 110
6,000 135
6,000
110
8,000
135
8,000
l1R24.5
95
6,000 110
6,000
95
8,000 110
8,000
Tires
Four
truck:
tires were selected for experimentation: a
bias Goodyear 18-22.5 LR-H super single tire, a radial
Michelin 275/80R{24.5 LR-G tire, a radial Michelin 255/
70R22.5 LR-G tire, and a radial Goodyear 11R24.5 LR-G
tire. The bias Goodyear 18-22.5 LR-H truck: tire, tested by
Hansen (Ref 1 , was subjected to further tests to obtain more
information on this tire, due to its popularity and growing
demand.
The radial Michelin 27 5/80R/24
5 LR
-G tire, the radial
Michelin 255{70R/22.5 LR-G tire, and the radial Goodyear
11R24.5
LR-G tire were selected due to their popularity on
Texas highways. In fact, the radial11 R24.5 tire is generally
considered to be
the
most common truck tire found running
on U.S. highways today (Refs 3 and 7).
Loads
and Inflation Pressures
All the tires except the bias Goodyear 18-22.5 LR-H
super single tire were tested at the maximum inflation
pressures and loads recommended by the manufacturers and
also at loads and inflation pressures that were roughly 20
percent higher. For the bias Goodyear 18-22.5 tire, it was
decided to load the tire at 15 ,000 pounds under the inflation
pressures (85 and 100 psi) used by Hansen (Ref
1).
The
6
applied wheel loads and tire inflation pressures are shown in
Table 3.1.
EXPERIMENTAL PROCEDURE
The flow chart of the experimental procedure used to
obtain tire contact pressure distributions
is
shown
in
Fig 3 1.
The experimental procedure used in this project consisted of
four stages: (1) mounting the tire, (2) testing the tire and
producing calibration squares, (3) analysis of the Fuji and
ink:
prints, and (4) presentation of results. For additional
details on the experimental procedure, consult Ref
I
Mounting
the Tire
The work: prior to the testing consisted of mounting the
tire
and placing the tire into the load frame, which was
followed by operations such as tightening the connections,
adjusting the alignment, installing the load calibration cell,
and controlling
the
tire inflation pressure
to the
desired
setting. Figure 3.2 shows the setup for the experiment: the
mounted tire
ready
for testing, the load frame, the hydraulic
pumps, the platfonn, the data acquisition system, and the
load cell.
Testing the
Tire
and Producing
alibration
Square
Fuji and ink: prints were made of the tires as they were
subjected to different combinations of wheel loads and
inflation pressures. The procedure was similar
to the
one
followed
by
Hansen (Ref 1), except that here the side tire
movements were lso recorded. This was done by measuring
the horizontal and vertical deflections of previously selected
reference points (see Appendix B for side tire movement
data).
(1) When
pressure is applied to a Fuji prescale film, the
film
changes color
in
such a way that darker pigmentation is
produced
in
zones of higher pressure. The Fuji or pressure
prints are used
to
relate the contact pressures with color
intensities. The Fuji preseale films are comprised of
A"
and
"C" sheets. Both sheets have a low compressibility polyester
base. The A sheet has a thin coating of microcapsule, color
forming material, and the C sheet has a thin coating
of
color
A special strategy was followed
for
the bias Goodyear
18-
22.5 LR-H tire, since it
was
felt that
in
this case the peak
pressure values would not be recorded, because they were
beyond the capacity (0 to285 psi)of the Fuji Super Low film.
Hansen stated that there was a possibility of not recording
higher pressure values due to the limited capacity of the Fuji
Super Low film. The very high intensities suggest that
pressure values could becomeas high as 500 psi or even 600
psi. Hence,
an
additional experiment was conducted using
Fuji Low range film, which has a higher capacity (170 to
1,000 psi).
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0
MOUNT
T H E T I F ~ E
f t . TESTTHETIRE
V
AND PRODUCE
CALl B. SOUA.RES
f t . ANALYSIS
OF
V THEFWIAND
INK PRINTS
0
PRESENTATION
OF RESULTS
MOUNTTHE TIRE
c
-ed<
A l i g n m ~ t Tightness,
Tre
lrtlal:ion
Presstre,
Symr-netry
at
Loading, and the
load
Calitration
Cell
•
RODUCE
TEST THE
TIRE
TEST
THE
TIRE
CALIS.
SOUA.RES
Using
the
Fuji
Using
the
Fuji Fim
Prescale
F
m
USing IIi<
'
•
WI PRINT
ANALYSIS
II INK PRINT ANALYSIS
' '
l
CALIBRATION
DIGITAllON
DETERMINATION
OF THE
CURVE
1----
PROCESS
CONTACTAREA
Color
lntensty
ol tt e
Based
on
the
vs.
Pressure Fuji
PrintS
Ill<
Prints
C O M ~ R I S O N
•
EST
CALCULATION
z
~ R M E T E R
OF
THE
0
APPLIED LOAD
APPLIED LOAD
Q
a:
CALCULATION
OF
0
r
0
THE CONTACT
CHECK
AREA
&.REPEAT
Based
on
the
0
.
Fuji Pri1ts
YES
l
SIMILAR?
TIRE CONTACT
PRESSURE
DISTI= IBUTION OUllPUT
NO
+
0
Pressure
Det«mlnal:bn r
Pld:s
NUTierical
Prop:>rtiors
d
CHECK
3D
Pressure
Presstre
COntact Area
. REPEAT
Pld:s
Map;
Cavered y Specific
0
resstre a ~
Fig 3.1. Flow chart of the experimental procedures used to obtain tire contact pressure
distributions.
7
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8
P
150AComputer
Fig 3.2. Load frame schematic Ref 1).
l ~
~ ~ ~ = : : . : :
r '''I+YJ&
z; ; ; ; ; ;; ; . . . ._ lnterm ediate
Layer
C-sheet ... ._Substrate
Fig
3.3.
Fuji prescale film working principle Ref 1).
developing material. The microcapsules
on the
A sheets are
of various sizes, and this allows them to break at different
pressure levels. Large microcapsules break at relatively
low
pressures, while smaller capsules break at higher pressures.
To
produce a color density image,
the
A and C sheets
are
superimposed
with the
coated surfaces
face to face. As
pressure
is
applied,
the
microcapsules
on the
A sheets break,
releasing
the
color material. Figure 3.3,
which is
taken
from
Ref 1, shows the working principle of
the
Fuji prescale film.
2)
The
calibration squares
were
produced
on
the Fuji
prescale
film
using a compression machine. These squares
were
produced at different
loads in
order
to have
a variety of
points to enable
us
to analyze and construct a calibration
curve
to
relate color intensities
with
pressure values. Since
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the Fuji prescale film changes with time and from box to box,
these calibration squares were produced at approximately
the same
time
as the Fuji prints; and,
in
the case where
two
separate boxes of Fuji prcscale film were used
to
complete
the
testing of one tire, a set o calibration squares
was
produced for each box of
film.
3) The ink prints were produced under
the
same
testing parameters as the Fuji prints. The monochrome
ink
prints were used for calculating the tire-plate contact areas.
The
ink
prints were made by applying a common black
ink
to the tire and pressing the tire down on a white paper that
covered the steel plate. From these prints, the tire contact
areas were determined using the counting method, i.e., by
placing a transparent grid paperon the ink print and counting
the number of shaded squares
in
the transparent grid paper.
4) The side tire movements were determined
by
se
lecting five reference points on
the
bias Goodyear
18-22.5
LR-
H super single tire and four reference points
on
the other
tires. Then the horizontal and vertical deflections of these
reference points were measured. These
data
are recorded in
Appendix B.
nalysis
o
h Fuji and Ink Prints
Analysis of the Fuji prints consisted of running the
programs developed by Chan Ref 2),
with
some modifica
tions by
these authors, and calculating
the
tire contact areas
from the
ink prints. The Adage System was used to digitize
and analyze the Fuji prints. The Adage system consists of an
Eikonix Scanner and an Adage3006Graphics System. A tire
image analysis program was run on this system to determine
the contact pressure distributions. Complete details of the
Adage system can be
found
in Ref 2 and
in
the Advanced
Graphics Laboratory of The University of Texas
at
Austin.
Also,acompleteexplanationthecomputerprogramsuscdto
determine the tire contact pressure distributions can be
found in
Refs 1
and 2.
A brief description of these is included
in
Appendix A.
During the analysis of
the
Fuji prints,
two
checks were
performed
in
order to validate the tire contact pressure
9
distribution output These checks were done for each tire and
at each set of experimental parameters. The first check was
to c o m p r ~ the calculated load obtained from the Adage
system with the actual wheel load applied during testing.
The second check was to compare the calculated tire contact
area obtained
from
the Adage system with the tire contact
area obtained from the counting method.
In
order to have
high reliability, these differences had to have
an
offsetofless
than 5 percent. Otherwise the whole analysis was checked
and repeated.
Presentationso Results
The results consisted of 2D contact pressure plots in
color, the numerical pressure maps, and the proportions of
the tire contact area at different pressure ranges.
The 2D pressure plots were produced in the Adage
system. These pressure plots are color spectra representing
the tire contact pressure distributions. These plots are dis
played on the screen of the computer monitor and then
recorded photographically.
The numerical pressure maps show the actual contact
pressure values acting
in the
contact area. The
2D
pressure
plots
and
the numerical pressure maps present the same data
but in different
ways.
The proportions o the contact area covered
by
the
following pressure ranges were determined from the nu
merical pressure maps:
1)
300 psi. This
was
done to provide
more
information on the tire-pavement contact pressure distribu
tions.
For
the
bias Goodyear 18-22.5 LR-H tire, results
from
both the Fuji Super Low and the Fuji Low range films were
combined, and the proportions of contact areas
for
the
following pressure ranges were determined:
301
to 400 psi,
401 to 500 psi, 501 to 600 psi, and >6 psi.
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CHAPTER 4. EXPERIMENTAL RESULTS
Using l.he Fuji prescale film and l.he Adage analysis
system, contact pressure distributions for the bias Goodyear
18-22.5 LR-H "Super Single" tire, the radial Michelin 275/
SOR/24.5 LR-G tire, lhe radial Michelin 255 70R22.5 LR-G
tire, and
l.he
radial Goodyear 11R24.5 LR-G tire were
recorded and analyzed. The experimental parameters and
the resulting contact pressures for each tire are presented.
BIAS GOODYEAR 18-22.5 LR-H "SUPER
SINGLE" TIRE
The bias Goodyear 18-22.5 LR-H truck tire, tested by
Hansen (Ref 1), was subjected to further tests to obtain more
information on this tire, due to its popularity and growing
demand. Hansen (Refl)
tested this tireat8,000, 10,000,and
12,000 pounds,
at
inflation pressures of85 and 100 psi. Here,
this tire was tested at 15,000 pounds, at the same inflation
pressures. Both films, the Super Low and l.he Low range Fuji
prescale films, were used. Also, ink prints were produced
in
each case.
Table4.1 shows (1) l.he print width, (2) the print length,
(3) the mean contact pressure values, (4)
l.he
tirecontact area
obtained from the Adage system, and (5) the tire contact area
obtained from the counting mel.hod for the various tire
inflation pressures and w heel1oads. Note that,
in
general, the
mean contact pressures are higher than the tire inflation
pressures. The differences in the tire contact areas obtained
from the Adage system and the counting method are on
l.he
order of± percent For this tire, results from l.he Fuji "Super
Low" and the Fuji
Low
range films were combined. Table
4.2 shows the contact area for various pressure ranges for the
case where the wheel load is 15,000 pounds.
The contact areas covered by
l.he
various pressure
ranges are computed from the numerical pressure maps
presented by Hansen (Ref 1) for l.he 12,000, 10,000, and
8,000-pound wheel load cases. These data are tabulated in
Table 4.3. Table 4.4 shows the load distribution across the
tread widl.h, obtained from the Adage system, when
l.he
tire
was tested at the 15,000-pound wheel load.
Figures 4.1 and 4.2 show two-dimensional contact
pressure plots in color for the tire loaded to a 15,000-pound
load when inflated to 100 and 85 psi, respectively. Figures
4.3 and 4.4 show
l.he
numerical contact pressure maps for the
same parameters. Figures 4.5 l.hrough 4.10 have been con
structed using the data from Tables
4.2
and 4.3. These
histograms show the effects
of
changing from one load to
another load, and
from one inflation pressure to another
inflation pressure.
RADIAL MICHELIN 275/SOR/24.5 LR-G
TIRE
The radial Michelin 275 80R/24.5 LR-G tire was ana
lyzed following the same procedure described in Chapter 3.
This tire was tested under its rated parameters and under a
setof
parameters roughly
20
percent higher. This tire is rated
for a maximum load of 6,005 pounds and a maximum
inflation pressureof 100 psi. This tire was tested
at
6,000 and
8,000 pounds, at inflation pressures
of
95 and 110 psi. Ink
prints were produced in each case.
The tire contact areas obtained from the Adage system
and the counting method, l.he print width and print length of
the contact areas, and the mean contact pressures are tabu
lated in Table 4.5. Note l.hat in general, the mean contact
pressures are higher than l.he tire inflation pressures. The
differences in the tire contact areas obtained from
l.he
Adage
system and the counting method are on the order of ± 5
percent.
The
proportions
of
contact area covered by the various
pressure ranges are computed from the numerical pressure
TABLE 4.2. BIAS 18-22.5
PROPORTIONS
OF
CONTACT
TABLE
4.1. BIAS GOODYEAR 18-22.5 TIRE TEST
AREA
(PERCENT)
FOR THE 15,000-
POUND WHEEL LOAD
DIMENSIONS
Pressure
Ranges
Innation Pressure
(f Sl)
8S
psi 100 psi
600
0.12
0.09
10
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TABLE 4.3.
BIAS 18-22.5
PROPORTIONS CONTACT AREA
PERCENT) OF THE
12,000, 10,000, AND 8,000-POUND
TABLE
4.4. BIAS 18-22.5 LOAD
DISTRIBUTION
LB) ACROSS
WHEEL
LOADS
THE TREAD WIDTH FOR THE
Pressure
12,000-lb Load
10,000-lb Load 8
1
000-lb Load
15,000-POUND
LOAD
Ranges
Tnnation Pressure
psi)
85 psi
100 psi
85 psi 100 psi 85 psi
300
0 00
0.00
1 16
1 00
0.68
maps forthe6,000 and 8,000-pound wheel loadcases.These
data are tabulated
in
Table 4.6. Table 4.7 shows the load
distribution across the tread width, obtained from the Adage
system, when the tire was tested
at
the tire inflation pressures
and wheel loads given
in
Table 3.
1
Figures 4.11 and 4.12 show two-dimensional contact
pressure plots for the tire loaded to a 6,000-pound load when
inflated to 95 and 110 psi, respectively. Figures 4.13 and
4.14 show two-dimensional contact pressure plots for the
tire loaded to an 8,000-pound load when inflated to 95 and
110 psi, respectively. Figures 4.15 through 4.18 show the
numerical contact pressure maps for the same parameters.
Figures 4.19 through 4.22 have been constructed using the
data from Table 4.6. These histograms show the effects
of
changing from one load to another load, and from one
inflation pressure to another inflation pressure.
RADIAL MICHELIN 255/70R/22.5 LR-G
TIRE
The radial Michelin
255nOR{22 5
LR-G tire was ana
lyzed following the procedure described in Chapter 3. This
tire was tested under its rated parameters and under a set
of
parameters roughly
20
percent higher. This tire is rated for
a maximum load
of
5,510 pounds and a maximum inflation
pressure
of
115 psi. This tire was tested
at6,000
and 8,000
pounds,
at
inflation pressures
of
110 and 135 psi. Ink prints
were produced in each case.
The
tire contact areas obtained from the Adage system
and the counting method, the print width and print length
of
the contact areas, and the mean contact pressures are tabu
lated in Tables 4.8. Note that, in general, the mean contact
pressures are higher than the tire inflation pressures. The
differences in the tire contactareas obtained from the Adage
system and the counting method are on the order
of
5
percent.
100 psi Position Innation Pressure
7 01
Tread
Width
85 psi
100 psi
48.65
Left
2339.3
2237.8
28.56
Left-Center
3249.1
3303
.6
9 35
Center
3363.7
3569.5
3 66
Right-Center
3244 1
3370.4
1 90
Right 2803
.3
2518.7
0 87
Fig
4.1.
Two-dimensional contact
pressure
plot for
the
bias Goodyear 18-22.5
LR-H tire
inflated to 100 psi
and
loaded to
15,000
pounds.
Fig
4.2.
Two-dimensional contact
pressure
plot
for the
bias Goodyear 18-22.5
LR-H tire
inflated to 85 psi and
loaded to
15,000
pounds.
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60
Load Inflation Pressure
50
•
8000 lb 85 psi
Ill
8000 lb 100 psi
40
30
20
10
0
300
Pressure Range (psi)
60
50
Load Inflation Pressure
•
10000 lb 85 psi
10000 lb 100 psi
40
30
20
10
0 300
Pressure Range (psi)
60
Load Inflation Pressure
50
•
12000 lb 85 psi
12000 lb 100 psi
40
30
20
10
o ~ . . . .
300
Pressure Range (psi)
Fig 4.5. Histogram for the bias Goodyear
18-22.5 LR-H tire. Shown are the
proportions
of
contact area
at
the various
contact pressure ranges for a 8 000-pound
wheel load and inflation pressures
of
85 and
100 psi.
Fig 4.6. Histogram for the bias Goodyear
18-22.5 LR-H tire. Shown are the
proportions of contact area at the various
contact pressure ranges for a 10 000-pound
wheel load and inflation pressures of 85 and
100 psi.
Fig 4.7. Histogram for the bias Goodyear
18-22.5 LR-H tire. Shown
are
the
proportions
of
contact area at the various
contact pressure ranges for a 12 000-pound
wheel load and inflation pressures of 85 and
100 psi.
-
8/17/2019 1190-2F
22/57
F
ig 4.8. H istog ra
m for the bias Go
odyear
18
-22.5 LR-H tire .
Shownare th e
prop
ortions
o
f conta c
t
a
rea at the var i
ous
contact pre s
sure ranges for a
15,000-pound
wheel load a
nd infiation press u
res
of
85 and
10
0 psi.
Fig 4.9. H isto g
ram for the bias
Goodyear
1
8-22.5 LR-H tire
. Shown are th e
proport
ions
of
contact are
a at the variou
s
contact
pressure ranges
for an infiation
pressure of
1
00 psi and lo a
ds of 8,000,
10,000
, 12,000 and 15,0
00 pounds.
Fig 4.10
. Histogram for
the bias Goodyea
r
18-22.5 L
R· tire. Shown a
re the
pr
oportions of cont
act area at th e v a
rious
contact
pressure ranges f
or
an
infiation
pressure of 8
5 psi and loads of
8,000, 10,000,
12,00
0 and 15,000 pou
nds.
60
L
50
ns
<
40
t
ns
E
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0
-
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a.
6
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ns
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E
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c:
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£
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t
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0
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c:
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0
a
0
10
a.
0
L
oa d Inflation Pres
sure
• 15000 lb 85
psi
15000 lb
100 psi
15
3
00
300
Pressure Rang e
(psi)
Lo
ad Inflation Press
ure
•
aooo lb
85 psi
10000 lb
85 psi
:
12000
lb 85 psi
[J
15000 lb 85 ps
i
50 -100 101-150
15 1-200 201·250
25 1-300 >300
Pressure R
ange (psi)
-
8/17/2019 1190-2F
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16
The proportions of contact area covered
by
the various pressure ranges
are
computed
from
the
numerical pressure maps
for the
6,000 and 8,000-pound wheel
load
cases.
These data
are
tabulated in Table 4.9. Table
4JO shows the load distribution across the
tread width, obtained
from
the Adage system,
when the
tire was tested at these experimental
parameters.
TABLE
4.5. RADIAL 275/SOR/24.5 TIRE TEST DIMENSIONS
Figures 4.11 and 4.12 show two
dimensional contact pressure plots for the tire
Inflation
Pressure
psi)
95
95
110
110
loaded
to a 6,000-pound load
when
inflated t 95
and 110
psi, respectively. Figures 4.13 and 4.14 show two
dimensional contact pressure plots
for
the tire
loaded
t an
8,000-pound load when inflated to 95 and 110 psi,
respectively. Figures 4.15 through 4.18 show the numerical
contact pressure
maps for
the
same
parameters. Figures4.19
Lhrough 4.22
have been
constructed
using
the data from
Table 4.6. These histograms show
the
effects of changing
from
one load to another
load
and
from
one inflation
pressure
to
another inflation pressure.
RADIAL GOODYEAR 11R24.5
LR·G TIRE
The radial Goodyear 11R24.5 LR-G was analyzed
fol
lowing the same procedure described in Chapter 3. This tire
was
tested under its rated parameters and under a set of
parameters roughly 20 percent
higher.
This tire is rated for
a maximum
load
of 6,430 pounds
and
a maximum inflation
pressure of 105 psi. This tire was tested at 6,000 and 8,000
pounds,
at
inflation pressures of 95 and 110 psi. Ink prints
were produced in
each
case.
The tire
contact areas obtained from the
Adage
system
and the counting
method;
the print
width and
print length of
the
contact areas;
and the mean
contact pressures
are tabu
lated in
Table
4.11.
Note that,
in general,
the
mean contact
pressures are higher than the tire inflation pressures.
The
differences in the
tire
contact areas obtained from
the Adage
system and the counting method
are
on the order of ±
percent.
The
proportions of contact area covered by the various
pressure ranges are computed
from
the numerical pressure
maps
for the 6,000
and
8,000-pound wheel
load
cases. These
data
are
tabulated in Table 4.12. Table
4.13
shows
the
load
distribution across the tread width, obtained
from
the Adage
system,
when
the tire was tested at these experimental
parameters.
Figures 4.35
and
4.36
show
two-dimensional contact
pressure plots for
the
tire loaded
to
a 6,000-pound load
when
inflated t 95
and
110 psi, respectively. Figures 4.37
and
4.38
show
two-dimensional contact pressure plots for the
tire loaded
t an
8,000-pound
load
when inflated
to 95
and
Wheel Print
Print
Mean
Tire Contact Area
Load Width
Length
Contact
Adage Manual
in.)
.J. :L
sq in.)
6,000 7.28
10.16 113.87 54.60 52.69
8,000 7.28
11.81 125.90 62.70 63.54
6,000 7.28 10.16 123.18 51.20 48.71
8,000
7.28 11.85 140.35
61.27 57.00
TABLE 4.6. RADIAL MICHELIN 275/SOR/24.5
PROPORTIONS OF
CONTACT
AREA PERCENT)
FOR THE
6,000 AND 8,000
POUNDS
Pressure
6,000-lb Load
8,000-lb Load
Ranges
Inflation Pressure
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Fig 4.11. Two-dimensional contact pressure plot for
the radial Michelin 275/SOR/24.5 LR-G tire innated to
95 psi nd loaded to 6 000 pounds.
Fig 4.12. Two-dimensional contact pressure plot for
the radial Michelin 275/SOR/24.5 LR-G tire inflated to
110 psi nd loaded to 6 000 pounds.
7
Fig 4.13. Two-dimensional contact pressure plot for
the radial Michelin 275/SOR/24.5 LR-G tire innated to
95 psi
nd
loaded to 8 000 pounds.
Fig 4.14. Two-dimensional contact pressure plot for
the radial Michelin 275/80R/24.S LR-G tire inflated to
110 psi
nd
loaded to 8 000 pounds.
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8/17/2019 1190-2F
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Fig 4.17. Numerical pressure
map
for the radial Michelin 275/SOR/24.5 tire inflated to 95 psi and loaded to 8,000
pounds. The pressure
print is
11.81 inches long and 7.28 inches wide.
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8/17/2019 1190-2F
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21
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