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Application of plateau value to predict fatigue life
Universidade do Minho, Portugal
J.C. Pais; P.A.A. Pereira; M.J.C. MinhotoL.P.T.L. Fontes; D.S.N.V.A. Kumar; B.T.A. Silva
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Background
1 hour
1 day
1 week
1 month
100
1000
1E+03 1E+04 1E+05 1E+06 1E+07
Tens
ile s
train
(E-6
)
Fatigue life (cycles)
Mix 17
Mix 02
Mix 13
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Background
Carpenter and Jansen (1997)Ratio of Dissipated Energy Change (RDEC)
a, b = loading cycle a and b
RDECa = the average ratio of dissipated energy change at cycle a, comparing to cycle b
DEa, DEb = dissipated energy at cycle a and b, respectively, which were calculated directly by fatigue testing program
( )abDEDEDERDEC
a
baa −×
−=
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Background
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Background
Shen and Carpenter (2005)found a unique relationship between PV and Nf50
for different mixturesloading modesloading levelstesting conditions
AAPT (2007), discussion
1102.1504428.0 −= NfPV
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Developed study
Maximum aggregate sizeMixture 1: 25 mmMixture 2: 14 mmMixture 3: 19 mm
Mixture DescriptionBinder type
(pen)Binder content
(%)
1 0/25 dense graded asphalt concrete for base layers 35/50 4.52 0/14 dense graded asphalt concrete for top layers 40/50 5.53 0/19 dense graded asphalt concrete for binder layers 35/50 4.3
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Fatigue testing results
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Shen and Carpenter (2005)simplified RDEC approach
dissipated energy must be fitted, by a power law relationship with the loading cycles
the slope, k, is used to calculate the plateau value as follows
50NfkPV −=
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Calculation of plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Proposed method to calculate the plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Proposed method to calculate the plateau value
The proposed method calculates the dissipated energy from the cumulative dissipated energy
To ensure that the calculated dissipated energy decreases during the considered loading cycles, the authors defined the following ones: 1E3, 2E3, 5E3, 1E4, 2E4, 5E4 and 1E5.
These loading cycles are approximately spaced in a logarithmic scale.
The plateau value is defined as the average of the RDEC for the calculated loading cycles before the failure of the specimen.
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Proposed method to calculate the plateau value
Universidade do Minho, Portugal
Application of plateau value to predict fatigue life
Conclusion
Interesting approach for the analysis of fatigue results
However, it needs more development
The proposed method must be improved mainly for low strain levels