A Fully Automated System for Monitoring Short Crack Growth

Hussey, I.W.; Roche, Joseph M.; Grabowski, L.

doi:10.1111/j.1460-2695.1991.tb00660.x

Cited by 9 publications

(2 citation statements)

References 2 publications

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“…For example, Hussey et al 14 studied small fatigue crack growth in Waspaloy by monitoring the major crack length using an image processing technique. For example, Hussey et al 14 studied small fatigue crack growth in Waspaloy by monitoring the major crack length using an image processing technique.…”

Section: Relationship Between N S and N Fmentioning

confidence: 99%

Characterization of Low-cycle Fatigue Damage in Inconel 718 by Laser Light Scanning

Chou

Earthman

1997

J. Mater. Res.

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A technique for in situ laser light scanning (LLS) was developed to monitor surface damage on nickel-base superalloy specimens under low-cycle fatigue conditions. This technique characterizes the surface state with a parameter called the defect frequency which minimizes memory requirements and data processing time since it does not involve image processing. As a result, the present technique is capable of scanning speeds that are substantially greater than those achieved with image processing methods. Cylindrical Inconel 718 specimens were tested using an automated servo-hydraulic machine at ambient temperature under fully reversed strain control conditions for constant strain amplitudes ranging from 0.3% to 1%. The fatigue damage was monitored by scanning a laser beam along the gauge section of the specimens during periodic interruptions of the cyclic loading. Acetate replicas of the gauge section surface were also made on some of the specimens to characterize the damage using SEM and image analysis techniques. Comparisons of the results demonstrate the capabilities of the present light-scanning technique for characterizing fatigue damage on the surface of the Inconel 718 specimens. In particular, a rapid rise in the mean defect frequency is shown to correspond to an initial increase in microcrack density that saturates at approximately 20% of the fatigue life. This transient behavior is followed by a plateau in defect frequency which corresponds to crack propagation and interlinkage until failure occurs. The number of cycles to microcrack density saturation as indicated by the defect frequency is found to be linearly related to the number of cycles to failure. Accordingly, the present system provides a characterization of microcrack damage that may be used to predict the low-cycle fatigue life of Inconel 718 specimens long before failure occurs.

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Section: Relationship Between N S and N Fmentioning

confidence: 99%

Characterization of Low-cycle Fatigue Damage in Inconel 718 by Laser Light Scanning

Chou

Earthman

1997

J. Mater. Res.

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“…The early stage of crack propagation can be influenced by the microstructure [S]. For example, the growth rate may be erratic, from high (lo-' mm/cycle), to arrested, crack arrest being primarily due to microstructural barriers [ 7 ] .…”

Section: Introductionmentioning

confidence: 99%

The Behaviour of Small Corner Cracks in a Ferritic/Pearlitic Steel: Experiments and Analyis

Craig

Ellyin

Kujawski

1995

Fatigue Fract Eng Mat Struct

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An experimental investigation into the growth and closure behaviour of small corner cracks has been conducted on a low carbon steel (ASTM A516 Grade 70). This ferritic/pearlitic steel has been chosen to investigate the complexities of small crack behaviour in the dual phase material. Innovative procedures are used for compliance measurement and opening load determination. The closure and growth behaviour of the small comer cracks are presented in terms of shape and size. The results are divided into two stages, the first pertaining to the "stationary crack", and the second dealing with the crack as it grows. The cracks are shown to exhibit an irregular growth rate, which is in part, shown to correspond with microstructural features of the material. In the short crack regime, the linear fracture mechanics parameter, AK does not correlate with the data and the use of a AKen based on the effective applied load provided little improvement.

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Growth and behaviour of small cracks

Ellyin

1997

Fatigue Damage, Crack Growth and Life Prediction

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A Fully Automated System for Monitoring Short Crack Growth

Cited by 9 publications

References 2 publications

Characterization of Low-cycle Fatigue Damage in Inconel 718 by Laser Light Scanning

Characterization of Low-cycle Fatigue Damage in Inconel 718 by Laser Light Scanning

The Behaviour of Small Corner Cracks in a Ferritic/Pearlitic Steel: Experiments and Analyis

Growth and behaviour of small cracks

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