practical method for fatigue crack experience

8/8/2019 Practical Method for Fatigue Crack Experience

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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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practical method for fatigue crack experience

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