j.c. pais; p.a.a. pereira; m.j.c. minhoto l.p.t.l. fontes; … · 2010-09-29 · universidade do...

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