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dc.contributor.advisorVan Tyne, C. J.
dc.contributor.advisorFindley, Kip Owen
dc.contributor.authorTerrazas, Oscar R.
dc.date.accessioned2016-09-19T21:51:54Z
dc.date.accessioned2022-02-03T12:56:22Z
dc.date.available2016-09-19T21:51:54Z
dc.date.available2022-02-03T12:56:22Z
dc.date.issued2016
dc.identifierT 8123
dc.identifier.urihttps://hdl.handle.net/11124/170419
dc.descriptionIncludes bibliographical references.
dc.description2016 Fall.
dc.description.abstractThe demand for advanced high strength steels (AHSS) with higher strengths is increasing in the automotive industry. While there have been major improvements recently in the trade-off between ductility and strength, sheared-edge formability of AHSS remains a critical issue. AHSS sheets exhibit cracking during stamping and forming operations below the predictions of forming limits. It has become important to understand the correlation between microstructure and sheared edge formability. The present work investigates the effects of shearing conditions, microstructure, and tensile properties on sheared edge formability. Seven commercially produced steels with tensile strengths of 1000 ± 100 MPa were evaluated: five dual-phase (DP) steels with different compositions and varying microstructural features, one trip aided bainitic ferrite (TBF) steel, and one press-hardened steel tempered to a tensile strength within the desired range. It was found that sheared edge formability is influenced by the martensite in DP steels. Quantitative stereology measurements provided results that showed martensite size and distribution affect hole expansion ratio (HER). The overall trend is that HER increases with more evenly dispersed martensite throughout the microstructure. This microstructure involves a combination of martensite size, contiguity, mean free distance, and number of colonies per unit area. Additionally, shear face characterization showed that the fracture and burr region affect HER. The HER decreases with increasing size of fracture and burr region. With a larger fracture and burr region more defects and/or micro-cracks will be present on the shear surface. This larger fracture region on the shear face facilitates cracking in sheared edge formability. Finally, the sheared edge formability is directly correlated to true fracture strain (TFS). The true fracture strain from tensile samples correlates to the HER values. HER increases with increasing true fracture strain.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2016 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjecthole expansion
dc.subjectAHSS
dc.subjectmicrostructure
dc.titleCorrelation of microstructure, tensile properties and hole expansion ratio in cold rolled advanced high strength steels
dc.typeText
dc.contributor.committeememberDe Moor, Emmanuel
dc.contributor.committeememberCryderman, Robert
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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