Show simple item record

Very High Cycle Fatigue Behavior of Nickel-based Superalloy Rene 88 DT/

dc.contributor.authorMiao, Jiashien_US
dc.date.accessioned2010-08-27T15:09:09Z
dc.date.availableNO_RESTRICTIONen_US
dc.date.available2010-08-27T15:09:09Z
dc.date.issued2010en_US
dc.date.submitteden_US
dc.identifier.urihttps://hdl.handle.net/2027.42/77730
dc.description.abstractThe fatigue behavior of the polycrystalline nickel-based superalloy René 88 DT has been investigated at 593°C up to the very high cycle fatigue regime using ultrasonic fatigue techniques. Conventional damage tolerant methods failed to predict the fatigue life nor the large fatigue life viability of two orders of magnitude observed in the very high cycle regime. Fatigue crack initiation rather than fatigue crack growth is the life determining process in this alloy in the very high cycle regime. At 593°C, all fatigue failures have subsurface origins. Most fatigue crack initiation sites consist of a large crystallographic facet or a cluster of several large crystallographic facets. By combining electron backscatter diffraction, metallographic serial sectioning and SEM-stereo-image-based quantitative fractographic analysis, critical microstructure features associated with subsurface crystallographic fatigue crack initiation were identified. Subsurface fatigue cracks formed by the localization of cyclic plastic deformation on {111} slip planes in the region close to and parallel to twin boundaries in favorably oriented large grains. The facet plane in the crack initiation grain is parallel to the slip plane with the highest resolved shear stresses. Analytical calculations show that twin boundary elastic incompatibility stresses contribute to the onset of cyclic plastic strain localization in the fatigue crack initiation grains. Favorably oriented neighbor grains also can assist with fatigue crack initiation and especially early small crack propagation. Environment may play an important role in the shift of fatigue crack initiation sites from surface to subsurface at elevated temperature. The fatigue behavior of René 88 DT was also investigated under fully reversed loading at room temperature using ultrasonic fatigue techniques. Cyclic plastic strain localization and microcrack formation on specimen surfaces were quantitatively studied by EBSD. All microcracks examined in detail initiated near Σ3s twin boundaries, especially Σ3 twin boundaries which are parallel to slip planes with the highest Schmid factor within crack initiation grains.en_US
dc.format.extent31019497 bytes
dc.format.extent1373 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypetext/plain
dc.language.isoen_USen_US
dc.subjectFatigueen_US
dc.subjectSuperalloyen_US
dc.subjectCrack Initiationen_US
dc.subjectTwin Boundaryen_US
dc.subjectCrystallographic Faceten_US
dc.subjectElectron Backscatter Diffractionen_US
dc.titleVery High Cycle Fatigue Behavior of Nickel-based Superalloy Rene 88 DT/en_US
dc.typeThesisen_US
dc.description.thesisdegreenamePhDen_US
dc.description.thesisdegreedisciplineMaterials Science and Engineeringen_US
dc.description.thesisdegreegrantorUniversity of Michigan, Horace H. Rackham School of Graduate Studiesen_US
dc.contributor.committeememberJones, J. Wayneen_US
dc.contributor.committeememberPollock, Tresa M.en_US
dc.contributor.committeememberAtzmon, Michaelen_US
dc.contributor.committeememberVan Der Ven, Antonen_US
dc.subject.hlbsecondlevelMaterials Science and Engineeringen_US
dc.subject.hlbtoplevelEngineeringen_US
dc.description.bitstreamurlhttp://deepblue.lib.umich.edu/bitstream/2027.42/77730/1/miaojias_1.pdf
dc.owningcollnameDissertations and Theses (Ph.D. and Master's)


Files in this item

Show simple item record

Remediation of Harmful Language

The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.

Accessibility

If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.