Russel Smith and Daniel Carpenter: Managing Fatigue Failures of Longwall Hydraulic Equipment
APPLICATIONS OF ENERGY CONCEPTS FOR FATIGUE ANALYSIS OF AIRPORT PAVEMENTS FAA Fatigue Project...
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Transcript of APPLICATIONS OF ENERGY CONCEPTS FOR FATIGUE ANALYSIS OF AIRPORT PAVEMENTS FAA Fatigue Project...
APPLICATIONS OF APPLICATIONS OF ENERGY CONCEPTS FOR ENERGY CONCEPTS FOR FATIGUE ANALYSIS OF FATIGUE ANALYSIS OF AIRPORT PAVEMENTSAIRPORT PAVEMENTS
APPLICATIONS OF APPLICATIONS OF ENERGY CONCEPTS FOR ENERGY CONCEPTS FOR FATIGUE ANALYSIS OF FATIGUE ANALYSIS OF AIRPORT PAVEMENTSAIRPORT PAVEMENTS
FAA Fatigue Project BriefingOctober 7th, 2004 Urbana, IL
Samuel H. Carpenter, ProfessorShihui Shen, Graduate Research Assistant
University of Illinois at Urbana-Champaign
PRESENTATIONPRESENTATIONPRESENTATIONPRESENTATION
Introduction
Objectives to the New Approach
Problems in Traditional Fatigue Analysis Approach
Energy Concepts & RDEC Approach
Findings & Results
Implications for Airport Pavements
Conclusions & Future Work
Introduction
Objectives to the New Approach
Problems in Traditional Fatigue Analysis Approach
Energy Concepts & RDEC Approach
Findings & Results
Implications for Airport Pavements
Conclusions & Future Work
INTRODUCTION : A NEW INTRODUCTION : A NEW APPROACHAPPROACH
RDEC APPROACHRDEC APPROACH
INTRODUCTION : A NEW INTRODUCTION : A NEW APPROACHAPPROACH
RDEC APPROACHRDEC APPROACH Fatigue is a Damage Phenomenon
Described by Energy Principles
All Fatigue Behavior can be Described by a Single Parameter
Ratio of Dissipated Energy Change (RDEC) : Percent of Load Cycle Input Energy Producing Damage
Plateau Value (PV): the Value When Material’s Ratio of Dissipated Energy Change is Constant During the Fatigue Test
Fatigue is a Damage Phenomenon Described by Energy Principles
All Fatigue Behavior can be Described by a Single Parameter
Ratio of Dissipated Energy Change (RDEC) : Percent of Load Cycle Input Energy Producing Damage
Plateau Value (PV): the Value When Material’s Ratio of Dissipated Energy Change is Constant During the Fatigue Test
OBJECTIVES OF THE OBJECTIVES OF THE NEW APPROACHNEW APPROACHOBJECTIVES OF THE OBJECTIVES OF THE NEW APPROACHNEW APPROACH Overcome the problems of traditional
fatigue analysis approach; Examine energy concepts and the
ratio of dissipated energy change (RDEC) approach;
Apply RDEC approach to airport pavement, and develop design considerations suitable for airfield conditions:
Heavy aircraft loads; Very thick pavements; Low load frequency.
Overcome the problems of traditional fatigue analysis approach;
Examine energy concepts and the ratio of dissipated energy change (RDEC) approach;
Apply RDEC approach to airport pavement, and develop design considerations suitable for airfield conditions:
Heavy aircraft loads; Very thick pavements; Low load frequency.
PROBLEMS IN PROBLEMS IN TRADITIONAL FATIGUE TRADITIONAL FATIGUE ANALYSIS APPROACHANALYSIS APPROACH
PROBLEMS IN PROBLEMS IN TRADITIONAL FATIGUE TRADITIONAL FATIGUE ANALYSIS APPROACHANALYSIS APPROACH
Cannot explain fatigue behavior under heavy loads on pavements of varying thicknesses;
Non-unique strain-Nf relationship. Such relationship is not fundamentally material based.
A distinctly different fatigue behavior appears when airport pavement is built very thick (low strain/damage levels);
Low load frequency in thick pavement amplifies the healing effect which cannot be observed and described by traditional approach.
Cannot explain fatigue behavior under heavy loads on pavements of varying thicknesses;
Non-unique strain-Nf relationship. Such relationship is not fundamentally material based.
A distinctly different fatigue behavior appears when airport pavement is built very thick (low strain/damage levels);
Low load frequency in thick pavement amplifies the healing effect which cannot be observed and described by traditional approach.
TRADITIONAL FATIGUE TRADITIONAL FATIGUE PLOTPLOTTRADITIONAL FATIGUE TRADITIONAL FATIGUE PLOTPLOT
10
100
1000
10000
1 100000 1E+10 1E+15 1E+20 1E+25 1E+30 1E+35 1E+40
Nf @ 50% stiffness reduction, log
Str
ain
(mic
rost
rain
), lo
g
3N701N1051N105P3N905N1055N90P1N80D1N80DP8N70P1B41-75-76-77-78-48-79-711-717-721-4post
Low Strain/Damage Range
Normal Strain/Damage Range
Nf=1.1E+7
Fatigue Under Heavy LoadFatigue Under Heavy Load
Fatigue In Very Thick PavementFatigue In Very Thick Pavement
ENERGY CONCEPTS: ENERGY CONCEPTS: DISSIPATED ENERGYDISSIPATED ENERGYENERGY CONCEPTS: ENERGY CONCEPTS: DISSIPATED ENERGYDISSIPATED ENERGY
• Ratio of Dissipated Energy Change (RDEC)• Ratio of Dissipated Energy Change (RDEC)
STRAIN
STR
ES
SINITIAL LOAD CYCLE
SECOND LOAD CYCLE
DIFFERENT DISSIPATED ENERGY BETWEEN FIRST AND SECOND LOAD CYCLE
)( iiii SinW
RATIO OF DISIPATED RATIO OF DISIPATED ENERGY CHANGE ENERGY CHANGE CALULATIONCALULATION
RATIO OF DISIPATED RATIO OF DISIPATED ENERGY CHANGE ENERGY CHANGE CALULATIONCALULATION
a
baa DE
DEDE
DE
DERDEC
TYPICAL RDEC PLOT TYPICAL RDEC PLOT WITH THREE WITH THREE BEHAVIOR ZONESBEHAVIOR ZONES
TYPICAL RDEC PLOT TYPICAL RDEC PLOT WITH THREE WITH THREE BEHAVIOR ZONESBEHAVIOR ZONES
IIIIII
IIIIII
Plateau ValuePlateau Value
Rati
o o
f D
issi
pate
d E
nerg
y
Rati
o o
f D
issi
pate
d E
nerg
y
Ch
an
ge,
Log
Ch
an
ge,
Log
Load Repetitions, Load Repetitions, LogLog
CURRENT FINDINGS IN CURRENT FINDINGS IN RDEC APPROACHRDEC APPROACHCURRENT FINDINGS IN CURRENT FINDINGS IN RDEC APPROACHRDEC APPROACH
Unique relationship between PV and Nf
Different mixtures, load levels, loading modes and testing conditions
PV is a comprehensive energy based parameter.
A lower (higher) PV is always associated with a lower (higher) damage, producing a longer (shorter) fatigue life
Unique relationship between PV and Nf
Different mixtures, load levels, loading modes and testing conditions
PV is a comprehensive energy based parameter.
A lower (higher) PV is always associated with a lower (higher) damage, producing a longer (shorter) fatigue life
RDEC APPROACHRDEC APPROACHRDEC APPROACHRDEC APPROACH
PV vs. Nf @ 50% stiffness reduction
y = 0.5746x-1.1121
R2 = 0.9769
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
loading cycles @ 50% stiffness reduction
Pla
teau
Val
ue
Various mixture types and testing conditions under heavy aircraft loads
RDEC RDEC APPROACHAPPROACHRDEC RDEC APPROACHAPPROACH
Normal PV: y = 0.5662x-1.1106
R2 = 0.9885
Low PV: y = 0.2871x-1.0793
R2 = 0.9984
1.E-35
1.E-30
1.E-25
1.E-20
1.E-15
1.E-10
1.E-05
1.E+00
1.E+00 1.E+04 1.E+08 1.E+12 1.E+16 1.E+20 1.E+24 1.E+28 1.E+32 1.E+36 1.E+40
loading cycles @ 50% stiffness reduction, log
Pla
teau
Val
ue,
log
Normal PVLow PV
8.57E-9
1.10E+7
Including the strain conditions (low strain/damage level) in very thick airport pavements
IMPLICATIONS FOR IMPLICATIONS FOR AIRPORT PAVEMENTSAIRPORT PAVEMENTSIMPLICATIONS FOR IMPLICATIONS FOR AIRPORT PAVEMENTSAIRPORT PAVEMENTS A fatigue endurance limit exists,
and is an important consideration for the design/performance of thick pavements (low strain/damage)
Healing effect is significant in pavements with low load occurrence.
A fatigue endurance limit exists, and is an important consideration for the design/performance of thick pavements (low strain/damage)
Healing effect is significant in pavements with low load occurrence.
UNIQUE ENERGY LEVEL UNIQUE ENERGY LEVEL AT WHICH NO FATIGUE AT WHICH NO FATIGUE DAMAGE EXISTSDAMAGE EXISTS
UNIQUE ENERGY LEVEL UNIQUE ENERGY LEVEL AT WHICH NO FATIGUE AT WHICH NO FATIGUE DAMAGE EXISTSDAMAGE EXISTS
PV vs. Nf @ 50% stiffness reduction
y = 0.5746x-1.1121
R2 = 0.9769y = 0.0659x-1.026
R2 = 0.9983
1.E-41
1.E-38
1.E-35
1.E-321.E-29
1.E-26
1.E-23
1.E-20
1.E-17
1.E-14
1.E-111.E-08
1.E-05
1.E-02
1.E+01
1.E+00 1.E+04 1.E+08 1.E+12 1.E+16 1.E+20 1.E+24 1.E+28 1.E+32 1.E+36 1.E+40
loading cycles @ 50% stiffness reduction
Pla
teau
Val
ue
Normal PV
Low PVPV=8.57E-PV=8.57E-99
Nf=1.10ENf=1.10E+7+7
FATIGUE ENDURANCE FATIGUE ENDURANCE LIMITLIMITFATIGUE ENDURANCE FATIGUE ENDURANCE LIMITLIMIT
Crucial for Design and Performance of Thick Pavements
Limit to HMA Thickness Unique fatigue curves
Independent of Traffic Level Significant element for structural
design
Minimizes Effect of Overloads
Crucial for Design and Performance of Thick Pavements
Limit to HMA Thickness Unique fatigue curves
Independent of Traffic Level Significant element for structural
design
Minimizes Effect of Overloads
1.E-27
1.E-24
1.E-21
1.E-18
1.E-15
1.E-12
1.E-09
1.E-27 1.E-25 1.E-23 1.E-21 1.E-19 1.E-17 1.E-15 1.E-13 1.E-11 1.E-09
PV from extended testing
PV
fro
m s
ho
rten
ed t
esti
ng
500,000
1 million
2million
3 million
5 million
Line of Equality
Compare PV projected from shortened testing with extended testingCompare PV projected from shortened testing with extended testing
USE OF PV TO USE OF PV TO SHORTEN FATIGUE SHORTEN FATIGUE TESTING FOR THICK TESTING FOR THICK PAVEMENTSPAVEMENTS
USE OF PV TO USE OF PV TO SHORTEN FATIGUE SHORTEN FATIGUE TESTING FOR THICK TESTING FOR THICK PAVEMENTSPAVEMENTS
USE OF PV TO USE OF PV TO SHORTEN FATIGUE SHORTEN FATIGUE TESTING FOR THICK TESTING FOR THICK PAVEMENTSPAVEMENTS
USE OF PV TO USE OF PV TO SHORTEN FATIGUE SHORTEN FATIGUE TESTING FOR THICK TESTING FOR THICK PAVEMENTSPAVEMENTS Plateau Value period can be reached much earlier than Nf @ 50% stiffness reduction point;
Reasonable projection can be obtained through greatly shortened low strain/damage testing.
500,000 Load repetitions
Plateau Value period can be reached much earlier than Nf @ 50% stiffness reduction point;
Reasonable projection can be obtained through greatly shortened low strain/damage testing.
500,000 Load repetitions
HEALINGHEALINGHEALINGHEALING Accepted Description
Between loads the damage is reversed as the asphalt-aggregate interface reattaches, removing micro-cracks
Actual Occurrence A continuous physical-chemical reaction
that occurs even during continuous loadings at low strain levels
Accepted Description Between loads the damage is reversed as
the asphalt-aggregate interface reattaches, removing micro-cracks
Actual Occurrence A continuous physical-chemical reaction
that occurs even during continuous loadings at low strain levels
HEALING IN AIRPORT HEALING IN AIRPORT PAVEMENTSPAVEMENTSHEALING IN AIRPORT HEALING IN AIRPORT PAVEMENTSPAVEMENTS
A Material Property Constant The HMA has the potential to recover
a relative amount of damage
When Load Damage Falls Below Healing Potential, Damage Accumulation is Minimal or Non-Existent
Fatigue Endurance Limit exists
Field Fatigue Life is Increased Over Lab Testing
A Material Property Constant The HMA has the potential to recover
a relative amount of damage
When Load Damage Falls Below Healing Potential, Damage Accumulation is Minimal or Non-Existent
Fatigue Endurance Limit exists
Field Fatigue Life is Increased Over Lab Testing
CURRENT HEALING CURRENT HEALING STUDYSTUDYCURRENT HEALING CURRENT HEALING STUDYSTUDY
y = -0.0282x2 - 0.0011x - 5.0937
R2 = 0.9786
-7
-6.5
-6
-5.5
-5
0 1 2 3 4 5 6 7
rest period (sec.)
log
(PV
)
PV – An energy level related to fatigue life, Nf
CONCLUSIONSCONCLUSIONSCONCLUSIONSCONCLUSIONS
Ratio of Dissipated Energy Change (RDEC) provides a unique way to study fatigue behavior of HMA;
Plateau Value, PV, is a function of material properties and pavement response;
PV-Nf relationship is unique for mixture type, loading mode, and all testing conditions;
Ratio of Dissipated Energy Change (RDEC) provides a unique way to study fatigue behavior of HMA;
Plateau Value, PV, is a function of material properties and pavement response;
PV-Nf relationship is unique for mixture type, loading mode, and all testing conditions;
CONCLUSIONSCONCLUSIONSCONCLUSIONSCONCLUSIONS PV shows a unique threshold for the
fatigue endurance limit (PVL). . Current results shows such PVL is around 8.57E-9;
PV-Nf uniqueness can be used to predict long fatigue life without running test to failure;
Healing can be observed with the PV. Represents an energy level of damage,
which decreases with an increase in rest periods (healing effect).
PV shows a unique threshold for the fatigue endurance limit (PVL). . Current results shows such PVL is around 8.57E-9;
PV-Nf uniqueness can be used to predict long fatigue life without running test to failure;
Healing can be observed with the PV. Represents an energy level of damage,
which decreases with an increase in rest periods (healing effect).
FUTURE WORKFUTURE WORK FUTURE WORKFUTURE WORK
Substantiate the relationship between PV and rest periods:
Relate PV with healing using energy concepts
Healing Index
Healing Rate
Asphalt Type Influence
Substantiate the relationship between PV and rest periods:
Relate PV with healing using energy concepts
Healing Index
Healing Rate
Asphalt Type Influence
FUTURE WORKFUTURE WORK FUTURE WORKFUTURE WORK
Integrate the energy based healing effects, rest periods, into an improved rational design procedure suitable for airfield conditions:
Heavy aircraft load
Thick pavement layers
Low loading frequency and extended rest periods
Integrate the energy based healing effects, rest periods, into an improved rational design procedure suitable for airfield conditions:
Heavy aircraft load
Thick pavement layers
Low loading frequency and extended rest periods
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