Effect of residual stress and cold work on fatigue of inconel 718

Fatigue is one of the common types of failures in engineering components. It is defined as the failure of a component under repetitive loading. As the research on fatigue progresses over time, the variety and number of factors contributing to fatigue have developed as well. From the early interest c...

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Main Author: Chin, Kai Siang
Other Authors: Sridhar Idapalapati
Format: Thesis-Doctor of Philosophy
Language:English
Published: Nanyang Technological University 2020
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Online Access:https://hdl.handle.net/10356/137207
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1372072023-03-11T18:01:58Z Effect of residual stress and cold work on fatigue of inconel 718 Chin, Kai Siang Sridhar Idapalapati School of Mechanical and Aerospace Engineering A*STAR - Advanced Remanufacturing and Technology Centre msridhar@ntu.edu.sg Engineering::Materials::Material testing and characterization Engineering::Aeronautical engineering::Aviation Fatigue is one of the common types of failures in engineering components. It is defined as the failure of a component under repetitive loading. As the research on fatigue progresses over time, the variety and number of factors contributing to fatigue have developed as well. From the early interest concerning mechanical and materials behaviour, factors such as heat, corrosion, surface finish have also been taken into consideration. This study aims to investigate the interaction between two factors of interest, residual stress and cold work and to correlate their effects to fatigue performance. Residual stress is defined as the stress that is still present in the equilibrium of the materials when all the loading from machining process are removed or completed. Compressive residual stress has been linked to fatigue life enhancement by inducing crack closure and delaying crack initiation. On the other hand, cold work is defined as the strengthening of a metal by plastic deformation due to dislocations generation and movement within the crystal structure itself. Residual stress and cold work are introduced simultaneously through surface treatment process such as shot peening and deep cold rolling. As a result of that, the effects of residual stress and cold work are hard to discern and differentiate. In addition, the investigation of the already intricate interaction between residual stress and cold work is made even more difficult by residual stress relaxation. This thesis focused on the correlation between residual stress and cold work to further determine their influence on fatigue life. The investigation begins with materials characterisation and fatigue test. Next, emphasize is given to mechanical cyclic relaxation and thermal relaxation as stress relaxation is an inevitable phenomenon during fatigue. The use of neutron diffraction to investigate the mechanical stress relaxation will be highlighted. A modified Zener-Wert-Avrami method has also been developed to model the thermal stress relaxation. Doctor of Philosophy 2020-03-06T05:09:12Z 2020-03-06T05:09:12Z 2019 Thesis-Doctor of Philosophy Chin, K. S (2019). Effect of residual stress and cold work on fatigue of inconel 718. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/137207 10.32657/10356/137207 en This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). application/pdf Nanyang Technological University
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Materials::Material testing and characterization
Engineering::Aeronautical engineering::Aviation
spellingShingle Engineering::Materials::Material testing and characterization
Engineering::Aeronautical engineering::Aviation
Chin, Kai Siang
Effect of residual stress and cold work on fatigue of inconel 718
description Fatigue is one of the common types of failures in engineering components. It is defined as the failure of a component under repetitive loading. As the research on fatigue progresses over time, the variety and number of factors contributing to fatigue have developed as well. From the early interest concerning mechanical and materials behaviour, factors such as heat, corrosion, surface finish have also been taken into consideration. This study aims to investigate the interaction between two factors of interest, residual stress and cold work and to correlate their effects to fatigue performance. Residual stress is defined as the stress that is still present in the equilibrium of the materials when all the loading from machining process are removed or completed. Compressive residual stress has been linked to fatigue life enhancement by inducing crack closure and delaying crack initiation. On the other hand, cold work is defined as the strengthening of a metal by plastic deformation due to dislocations generation and movement within the crystal structure itself. Residual stress and cold work are introduced simultaneously through surface treatment process such as shot peening and deep cold rolling. As a result of that, the effects of residual stress and cold work are hard to discern and differentiate. In addition, the investigation of the already intricate interaction between residual stress and cold work is made even more difficult by residual stress relaxation. This thesis focused on the correlation between residual stress and cold work to further determine their influence on fatigue life. The investigation begins with materials characterisation and fatigue test. Next, emphasize is given to mechanical cyclic relaxation and thermal relaxation as stress relaxation is an inevitable phenomenon during fatigue. The use of neutron diffraction to investigate the mechanical stress relaxation will be highlighted. A modified Zener-Wert-Avrami method has also been developed to model the thermal stress relaxation.
author2 Sridhar Idapalapati
author_facet Sridhar Idapalapati
Chin, Kai Siang
format Thesis-Doctor of Philosophy
author Chin, Kai Siang
author_sort Chin, Kai Siang
title Effect of residual stress and cold work on fatigue of inconel 718
title_short Effect of residual stress and cold work on fatigue of inconel 718
title_full Effect of residual stress and cold work on fatigue of inconel 718
title_fullStr Effect of residual stress and cold work on fatigue of inconel 718
title_full_unstemmed Effect of residual stress and cold work on fatigue of inconel 718
title_sort effect of residual stress and cold work on fatigue of inconel 718
publisher Nanyang Technological University
publishDate 2020
url https://hdl.handle.net/10356/137207
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