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Fractal theory of a propagating crack in austenitic stainless steel

Classical fracture mechanics have limitation when it comes to solving real world applications. Factors such as material properties, probabilistic aspects make it difficult for classical fracture mechanics to be used in fatigue life prediction on working components. The introduction of fractal theory...

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Main Author: Abas, Muhamad Ariff
Format: Thesis
Language:English
Published: 2017
Subjects:
TJ Mechanical engineering and machinery
Online Access:http://eprints.utm.my/id/eprint/78850/1/MuhamadAriffAbasMFKM2017.pdf
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spelling my.utm.788502018-09-17T04:21:15Z http://eprints.utm.my/id/eprint/78850/ Fractal theory of a propagating crack in austenitic stainless steel Abas, Muhamad Ariff TJ Mechanical engineering and machinery Classical fracture mechanics have limitation when it comes to solving real world applications. Factors such as material properties, probabilistic aspects make it difficult for classical fracture mechanics to be used in fatigue life prediction on working components. The introduction of fractal theory provides a better alternative tool for fatigue life prediction. Therefore, this research aims to investigate the relationship between stress intensity factor range, !J.K and local fractal dimension on the crack surface, Df . Compact tension (C(T)) specimen was used for fatigue crack growth rate test in accordance to ASTM E647 to obtain crack length against number of cycles i.e. "a vs N" curve. In the constant growth rate stage ranging from 2.0 (10. 8) to 2.5 (10.7 ) m/cycle, the crack growth rate behavior can be represented by Paris Law equation with coefficient of3.0 (10.12 ) and 3.2851. This linear region ranging from !J.K 16 Ml'avm to 28 Ml'avm will be considered for fractal dimension evaluation. Fractal dimension evaluation was conducted using the Box-counting method. The process was made for different sampling sizes, !J.x to find the optimum range for this method. Results have shown that for every sampling size, increment of Df is fairly consistent with the value of 0.065. We can also deduce that a correlation can be made between Df and !J.K where a linearly increasing relationship was obtained. This shows that the crack tip driving force leaves behind a local uniqueness on the crack surface which varies along the crack length. If was also found that sampling sizes ranging from 0.025mm to 0.055mm have achieved the best consistency for evaluating Df . Fractal dimension for this range only varies from 1.7274 to 1.7293. It contributes to only 5% of the entire Df range that was tested. Improvement to achieve a single value (lower percentage) for Df could be possible if the mentioned recommendations will be considered for future works. 2017-01 Thesis NonPeerReviewed application/pdf en http://eprints.utm.my/id/eprint/78850/1/MuhamadAriffAbasMFKM2017.pdf Abas, Muhamad Ariff (2017) Fractal theory of a propagating crack in austenitic stainless steel. Masters thesis, Universiti Teknologi Malaysia, Faculty of Mechanical Engineering. http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:110278
institution Universiti Teknologi Malaysia
building UTM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Malaysia
content_source UTM Institutional Repository
url_provider http://eprints.utm.my/
language English
topic TJ Mechanical engineering and machinery
spellingShingle TJ Mechanical engineering and machinery
Abas, Muhamad Ariff
Fractal theory of a propagating crack in austenitic stainless steel
description Classical fracture mechanics have limitation when it comes to solving real world applications. Factors such as material properties, probabilistic aspects make it difficult for classical fracture mechanics to be used in fatigue life prediction on working components. The introduction of fractal theory provides a better alternative tool for fatigue life prediction. Therefore, this research aims to investigate the relationship between stress intensity factor range, !J.K and local fractal dimension on the crack surface, Df . Compact tension (C(T)) specimen was used for fatigue crack growth rate test in accordance to ASTM E647 to obtain crack length against number of cycles i.e. "a vs N" curve. In the constant growth rate stage ranging from 2.0 (10. 8) to 2.5 (10.7 ) m/cycle, the crack growth rate behavior can be represented by Paris Law equation with coefficient of3.0 (10.12 ) and 3.2851. This linear region ranging from !J.K 16 Ml'avm to 28 Ml'avm will be considered for fractal dimension evaluation. Fractal dimension evaluation was conducted using the Box-counting method. The process was made for different sampling sizes, !J.x to find the optimum range for this method. Results have shown that for every sampling size, increment of Df is fairly consistent with the value of 0.065. We can also deduce that a correlation can be made between Df and !J.K where a linearly increasing relationship was obtained. This shows that the crack tip driving force leaves behind a local uniqueness on the crack surface which varies along the crack length. If was also found that sampling sizes ranging from 0.025mm to 0.055mm have achieved the best consistency for evaluating Df . Fractal dimension for this range only varies from 1.7274 to 1.7293. It contributes to only 5% of the entire Df range that was tested. Improvement to achieve a single value (lower percentage) for Df could be possible if the mentioned recommendations will be considered for future works.
format Thesis
author Abas, Muhamad Ariff
author_facet Abas, Muhamad Ariff
author_sort Abas, Muhamad Ariff
title Fractal theory of a propagating crack in austenitic stainless steel
title_short Fractal theory of a propagating crack in austenitic stainless steel
title_full Fractal theory of a propagating crack in austenitic stainless steel
title_fullStr Fractal theory of a propagating crack in austenitic stainless steel
title_full_unstemmed Fractal theory of a propagating crack in austenitic stainless steel
title_sort fractal theory of a propagating crack in austenitic stainless steel
publishDate 2017
url http://eprints.utm.my/id/eprint/78850/1/MuhamadAriffAbasMFKM2017.pdf
http://eprints.utm.my/id/eprint/78850/
http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:110278
_version_ 1643658023881670656
score 13.211869

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