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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorMackenzie, John D.
dc.contributor.authorNeely Jr., James E.
dc.date.accessioned2021-11-03T08:44:54Z
dc.date.available2021-11-03T08:44:54Z
dc.date.created2017-02-23T15:29:26Z
dc.date.issued1969-05
dc.identifier.urihttps://hdl.handle.net/20.500.13015/1880
dc.descriptionMay 1969
dc.descriptionSchool of Engineering
dc.description.abstractThe annealing behavior of indentations in Si02 and caO·Si02 glass was investigated. The effect of heat treatment on indentation depths in silica glass was determined on 400 and 600 gram indentations. During the first 1/4 hour of annealing of silica glass, large indentation depth recoveries were observed, after which little or no change was observed for several hours of annealing at temperature. It was found that the indentation depth which is observed after a given time at a specific temperature is, statistically, independent of previous heat treatment at lower temperatures. Since most indentation recovery occurred rapidly in the initial stage of annealing, the experimental activation energy characteristic of this process was determined from the initial rates of indentation recovery for temperatures from 6000 to lOOOoC. Experimental activation energies of approximately 4 Kcal/mole were evaluated for both loads. Approximately one-half of the indentation depth of silica glass was found to anneal out below Tg. Indentation depths of caO·Si02 glass recovered much less at temperatures below Tg, such that no analysis of an activation energy could be made.
dc.description.abstractIn this study fracture-free Vickers indentations were made at high loads up to 8000 grams. All indentation dimensions were determined from high resolution photomicrographs usually at magnifications of 1460X for bright field, and 2000X for interference photography. Therefore, the attainable accuracy was much greater than in all previous investigations.
dc.description.abstractThe primary mechanism of indentation deformation in the glasses investigated was shown to be densification by molecular entanglement and an approach of the glass structure to its equilibrium volume.
dc.description.abstractHardness numbers of glasses have been determined by many investigators as an empirical measure of the strength of glass. Early investigators believed that 'permanent" indentations in glass were formed by plastic deformation, while later investigators suggested a variety of deformation mechanisms such as viscous flow, radial plastic flow, viscoelastic deformation, and densification. As a result of this situation, the present investigation was undertaken to determine the nature and possible variation of the deformation which occurs during indentation in order to define glass hardness.
dc.description.abstractHardness of a variety of glasses was found to be independent of load for all loads above 50 grams. The hardness of silica glass was investigated as a function of load time and loading rate,from which it was observed that hardness is significantly affected only after a load time of ~lOS seconds or at loading rates above 40 mm/min. As a result of the former observation, it was concluded that static fatigue of high load indentations is non-existent for silica glass. The hardness of silica glass as determined from 1000 gram indentations was found to vary only from 610 ±15 Kg/mm2 to 655 ± 15 Kg/mm2 over the temperature range of 130° to -72°C.
dc.description.abstractIt was found that the elastic recovery of indentation depths varied from 19 to 53% for the glasses investigated. It was observed that as the per cent elastic recovery increased, the maximum load which could be used to obtain fracture-free indentations generally increased. No relation was observed to exist between elastic deformation and Vickers hardness for the variety of glasses indented. The size of indentations in silica glass was shown to be independent of the elastic recovery of the indentation depth. It was concluded that the deformation which leads to the formation of indentations is independent of elastic deformation. This is in agreement with the observation that insignificant recoveries occur along the diagonals of Vickers indentations upon unloading.
dc.description.abstractBy indenting over surface scratches, it was proven that non-elastic displacement of glass during indentation does not occur in a radial direction.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMaterials science glass science
dc.titleHardness and high pressure deformation mechanisms of glass
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid177975
dc.digitool.pid177976
dc.digitool.pid177977
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDepartment of Materials Engineering


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