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Fatigue crack growth with overloads/underloads: Interaction effects and surface roughness

datacite.subject.fosCiências Naturais::Matemáticas
datacite.subject.fosEngenharia e Tecnologia::Engenharia Mecânica
datacite.subject.fosEngenharia e Tecnologia::Engenharia dos Materiais
dc.contributor.authorRomeiro, F.
dc.contributor.authorFreitas, M. de
dc.contributor.authorFonte, M. da
dc.date.accessioned2025-05-16T16:05:59Z
dc.date.available2025-05-16T16:05:59Z
dc.date.issued2009-01-09
dc.descriptionRomeiro, Fernando F.J. - Scopus ID: 6506547784
dc.description.abstractThe generalization of damage tolerance to variable amplitude fatigue is of prime importance in order to maintain the reliability of structures and mechanical components subjected to severe loading conditions. Engineering spectra usually contain overloads and underloads which distribution may not be random. However for predicting the life of a structure, a simplified spectrum is usually determined from the real one, in order to reduce testing periods on prototypes. Therefore it is thus important to know which cycles can contribute to crack growth and which can be neglected. This paper presents an analysis of fatigue crack growth on M (T) specimens made of a medium carbon steel DIN Ck45. The specimens are subjected to repeated blocks of cycles made up of one or several (1, 2, 6 or 10) overloads (or underloads) separated by a variable number (10, 1000 or 10 000) of baseline cycles. The main objective of this study is to better understand the mechanisms at the origin of interactions effects due to the presence of overloads (or underloads) at different locations of each block loading. Under constant amplitude loading, single variables ΔK and Kmax are required in crack growth relationships. The transferability of fatigue laws, obtained under constant amplitude loading to variable amplitude fatigue, requires at least an additional variable, whose evolution with crack length accounts for the interactions effects between cycles of different types. Results have shown that the interaction effects in fatigue crack growth are closely related to the mechanisms of crack growth: cyclic plastic behaviour of the material and fracture surface roughness. Measurements of roughness of the surface fracture were carried out in both constant amplitude and variable amplitude tests. The roughness characterization helped to determine the importance of the mechanisms on variable amplitude fatigue crack growth and determine the influence of overloads/underloads on fatigue crack growth.eng
dc.identifier.citationF. Romeiro, M. de Freitas, M. da Fonte, Fatigue crack growth with overloads/underloads: Interaction effects and surface roughness, International Journal of Fatigue, Volume 31, Issues 11–12, 2009, Pages 1889-1894, ISSN 0142-1123, https://doi.org/10.1016/j.ijfatigue.2009.01.001.
dc.identifier.doi10.1016/j.ijfatigue.2009.01.001
dc.identifier.issn0142-1123
dc.identifier.urihttp://hdl.handle.net/10400.8/12911
dc.language.isoeng
dc.peerreviewedyes
dc.publisherElsevier
dc.relation.hasversionhttps://www.sciencedirect.com/science/article/pii/S0142112309000036?via%3Dihub
dc.relation.ispartofInternational Journal of Fatigue
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectFatigue crack growth
dc.subjectOverloads
dc.subjectUnderloads
dc.subjectFracture roughness
dc.titleFatigue crack growth with overloads/underloads: Interaction effects and surface roughnesseng
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage1894
oaire.citation.issue11-12
oaire.citation.startPage1889
oaire.citation.titleInternational Journal of Fatigue
oaire.citation.volume31
oaire.versionhttp://purl.org/coar/version/c_970fb48d4fbd8a85

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The generalization of damage tolerance to variable amplitude fatigue is of prime importance in order to maintain the reliability of structures and mechanical components subjected to severe loading conditions. Engineering spectra usually contain overloads and underloads which distribution may not be random. However for predicting the life of a structure, a simplified spectrum is usually determined from the real one, in order to reduce testing periods on prototypes. Therefore it is thus important to know which cycles can contribute to crack growth and which can be neglected. This paper presents an analysis of fatigue crack growth on M (T) specimens made of a medium carbon steel DIN Ck45. The specimens are subjected to repeated blocks of cycles made up of one or several (1, 2, 6 or 10) overloads (or underloads) separated by a variable number (10, 1000 or 10 000) of baseline cycles. The main objective of this study is to better understand the mechanisms at the origin of interactions effects due to the presence of overloads (or underloads) at different locations of each block loading. Under constant amplitude loading, single variables ΔK and Kmax are required in crack growth relationships. The transferability of fatigue laws, obtained under constant amplitude loading to variable amplitude fatigue, requires at least an additional variable, whose evolution with crack length accounts for the interactions effects between cycles of different types. Results have shown that the interaction effects in fatigue crack growth are closely related to the mechanisms of crack growth: cyclic plastic behaviour of the material and fracture surface roughness. Measurements of roughness of the surface fracture were carried out in both constant amplitude and variable amplitude tests. The roughness characterization helped to determine the importance of the mechanisms on variable amplitude fatigue crack growth and determine the influence of overloads/underloads on fatigue crack growth.
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