Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip

A stereo microscope coupled to a 3-D Digital Image Correlation system is used to measure strain ranges on the cyclic plastic zone ahead of a fatigue crack-tip. First, a very refined speckle pattern is applied on the surface of a disk-shaped compact tension specimen of 1020 low-C steel by spraying to...

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Main Authors: Giancarlo luis Gómez Gonzáles, Julián Andrés Ortiz González, Jaime Tupiassú Pinho de Castro, José Luiz de França Freire
Format: Article
Language:English
Published: Gruppo Italiano Frattura 2019-05-01
Series:Fracture and Structural Integrity
Subjects:
Online Access:https://www.fracturae.com/index.php/fis/article/view/2497
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author Giancarlo luis Gómez Gonzáles
Julián Andrés Ortiz González
Jaime Tupiassú Pinho de Castro
José Luiz de França Freire
author_facet Giancarlo luis Gómez Gonzáles
Julián Andrés Ortiz González
Jaime Tupiassú Pinho de Castro
José Luiz de França Freire
author_sort Giancarlo luis Gómez Gonzáles
collection DOAJ
description A stereo microscope coupled to a 3-D Digital Image Correlation system is used to measure strain ranges on the cyclic plastic zone ahead of a fatigue crack-tip. First, a very refined speckle pattern is applied on the surface of a disk-shaped compact tension specimen of 1020 low-C steel by spraying toner powder over a layer of white paint, a suitable technique to produce the very small dots needed to map surface strain loops on that small region. This technique can achieve enough resolution to measure elastoplastic strain ranges Δε near the crack tip, which cause damage accumulation inside the cyclic plastic zone as the crack grows. The applied technique can identify as well the effects of other nonlinear phenomena that happen in the near-tip region, such as crack closure. Therefore, such measurements can be used to verify the validity of the hypotheses behind the main fatigue crack growth models.
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publisher Gruppo Italiano Frattura
record_format Article
series Fracture and Structural Integrity
spelling doaj-art-f680a1aac6da4ac2b1632b66beda3d762025-01-03T00:39:47ZengGruppo Italiano FratturaFracture and Structural Integrity1971-89932019-05-011349Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tipGiancarlo luis Gómez Gonzáles0Julián Andrés Ortiz González1Jaime Tupiassú Pinho de Castro2José Luiz de França Freire3Pontifical Catholic University of Rio de Janeiro, PUC-Rio.Pontifical Catholic University of Rio de Janeiro, PUC-Rio.Pontifical Catholic University of Rio de Janeiro, PUC-Rio.Pontifical Catholic University of Rio de Janeiro, PUC-Rio.A stereo microscope coupled to a 3-D Digital Image Correlation system is used to measure strain ranges on the cyclic plastic zone ahead of a fatigue crack-tip. First, a very refined speckle pattern is applied on the surface of a disk-shaped compact tension specimen of 1020 low-C steel by spraying toner powder over a layer of white paint, a suitable technique to produce the very small dots needed to map surface strain loops on that small region. This technique can achieve enough resolution to measure elastoplastic strain ranges Δε near the crack tip, which cause damage accumulation inside the cyclic plastic zone as the crack grows. The applied technique can identify as well the effects of other nonlinear phenomena that happen in the near-tip region, such as crack closure. Therefore, such measurements can be used to verify the validity of the hypotheses behind the main fatigue crack growth models.https://www.fracturae.com/index.php/fis/article/view/2497Digital Image CorrelationCrack-tip strain fieldCyclic plastic zoneDamage ahead of the crack tipStereo microscope measurements
spellingShingle Giancarlo luis Gómez Gonzáles
Julián Andrés Ortiz González
Jaime Tupiassú Pinho de Castro
José Luiz de França Freire
Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
Fracture and Structural Integrity
Digital Image Correlation
Crack-tip strain field
Cyclic plastic zone
Damage ahead of the crack tip
Stereo microscope measurements
title Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
title_full Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
title_fullStr Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
title_full_unstemmed Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
title_short Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
title_sort using dic techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip
topic Digital Image Correlation
Crack-tip strain field
Cyclic plastic zone
Damage ahead of the crack tip
Stereo microscope measurements
url https://www.fracturae.com/index.php/fis/article/view/2497
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