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dc.contributor.advisorClarke, Kester
dc.contributor.authorMadrid, Mykal
dc.date.accessioned2018-10-08T19:39:23Z
dc.date.accessioned2022-02-03T13:11:23Z
dc.date.available2018-10-08T19:39:23Z
dc.date.available2022-02-03T13:11:23Z
dc.date.issued2018
dc.identifierMadrid_mines_0052N_11590.pdf
dc.identifierT 8577
dc.identifier.urihttps://hdl.handle.net/11124/172533
dc.descriptionIncludes bibliographical references.
dc.description2018 Summer.
dc.description.abstractThe automotive industry is in constant search for steels that can reduce vehicle weight to help satisfy the stringent fuel economy and safety standards. Advanced high strength steels (AHSS) have become a viable option due to their excellent mechanical properties; however, these high strength steels exhibit edge cracking during stamping processes, failing at strains lower than those predicted by forming limit diagrams (FLD). Therefore, test methods such as hole expansion testing (HET) have been implemented to help understand edge failure in these AHSS. Characterizing the mechanical properties and microstructures of AHSS becomes crucial to understanding the hole expansion ratio (HER) determined through HET. In this study, we focus on the effects of mechanical properties and microstructure on HER performance. We also focus on a crack resistance parameter known as the crack tip opening angle (CTOA). The materials of interest are high strength dual phase (DP) and quenched and partitioned (QP) steels. The results showed that the difference in hardness between martensite and ferrite proved to have the most effect on the HER for the DP steels. For the QP steels, there did not seem to be a mechanical property that was tested in this study that correlated with the HER. The microstructural aspects that contributed to the HER performance were the martensite morphology and retained austenite (RA) stability for the DP and QP steels, respectively. A martensite network along ferrite grain boundaries proved to be beneficial in the DP steels studied, while a steady, continuous amount of RA transformation throughout deformation was beneficial to HER performance in the QP steels. Finally, CTOA correlated well with HER and proved that a crack resistance parameter was important to begin understanding HER.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2018 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.titleHole expansion performance and the resistance to crack propagation in high strength DP and QP steels
dc.typeText
dc.contributor.committeememberVan Tyne, C. J.
dc.contributor.committeememberFindley, Kip Owen
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineMetallurgical and Materials Engineering
thesis.degree.grantorColorado School of Mines


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