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PRACTICAL METHOD FOR FATIGUE CRACK
INITIATION DETECTION USING AN
ION-SPUTTERED FILM
SDM COLLEGE OF ENGG AND TECH
UNDER GUIDEProf. A.V.Kulkarni
Presented By
Srinivas Shiggavi1
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The fatigue life is considered to consist of the fatigue
crack initiation life and the fatigue crack growth life.
The fatigue growth life can now be predicted after a
fatigue crack has been detected or after a crack becomes
larger than a micro crack.
The fatigue crack initiation life remains
very difficult to estimate
Surface condition has strong effects on the fatigue
strength of machine elements
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The estimation of fatigue crack initiation life isvery important in fatigue strength design
Makabe et al. used a strain waveform for
the detection of fatigue crack of 0.5 1 mm on a
round test piece with a small hemispherical pit.
Katayama et al and Lee and Sakane detected
crack initiation using an AC potential method
on a sharply notched test piece
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practical method is presented for detecting
fatigue crack initiation during fatigue tests usingan ion-sputtered film.
Ion-sputtered films were formed on acrylic andSteel test pieces having especially designed
round notch
ion-sputtered film method consists of DC power source,electric resister, Digital recorder
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Electric Resistance Measurement of the Ion-Sputtered Film.
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Piece and Test Method
Three-Point Bending Test Piece.
Electric Resistance Measurement of theIon-Sputtered Film.
Fatigue Test Rig and Test Method.
Durability of the Ion-Sputtered Film.
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Fatigue Crack Initiation Detection Method
Principle Of The Method
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Three-Point Bending Test Piece.
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View of a test piece with an ion sputtered film on the test
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Durability of the Ion-Sputtered Film
Ion-sputtered film is formed by the adhesion of ions
Electric resistance of an ion-sputtered film during the test withoutcrack initiation on a steel test piece
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Crack Initiation Detection for Acrylic Test Pieces
Changes in the Electric Resistance Due to Crack Initiation
Change in the electric resistance of the ion-sputtered
film during fatigue crack initiation 11
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A view of the micro crack initiated on the notch surface
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Effect of Ion-Sputtered Film Shape on the Response toCrack Initiation.
variation in the electric resistance of the ion-sputtered
film is very small at the beginning of crack initiation
Electric resistance increase rate for different shapes of films 13
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Crack Initiation Detection for Steel Test Pieces
A very thin insulating film is necessary between the ion-sputtered
film and the steel surface to obtain a good response to
crack initiation.
Section view of the crack initiation detectionspot of a steel test piece 14
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Crack Initiation Detection for Steel Test Pieces.
Fatigue crack initiation detection tests were performed for
the test pieces made of carbon steel
The maximum load was 8500 N
The loading frequency was 30 Hz
The film thickness was about 50 nm
The electric resistance of the ion-sputtered film decreased
gradually after the beginning of the test
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Change in the electric resistance of the ion-sputtered film
during crack initiation on a steel test piece
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Conclusions
Method for detecting fatigue crack initiation is proposed
using an ion-sputtered film and is based on the change in thefilms electric resistance, due to crack initiation and crack
growth.
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