Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1895. / The entire thesis text is included in file. Holograph [Handwritten and illustrated in entirety by author]. Title from title screen of thesis/dissertation PDF file (viewed )

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This study was designed to examine the effect of impact velocity on the crushing behavior of open-cell aluminum foam over a range of velocities similar to what would be encountered for impact mitigation and blast protection applications. An experimental set-up was designed, fabricated and validated for studying the crushing response of cellular materials at high velocities. It consists of a gas gun, a pressure bar, high-speed data acquisition and high-speed imaging. The facility uses high-speed video images of the crushing event synchronized to force measurements with a pressure bar at one end of the foam to examine the dynamic stress and deformation history of foam specimens. Ten pores per inch open-cell Al-6101-T6 Doucel foam cylindrical specimens with a relative density of about 0.085 were impacted in the rise direction at velocities ranging from 21.6 to 127 m/s. The experimental results show that for impact speeds greater than about 40 m/s crushing of the foam occurred through a shock front. Furthermore, the experiments show an increase in the densification strain, average stress in the crushed region and shock velocity with increasing impact velocity, whereas the stress in the uncrushed region appears to be insensitive to velocity. A method of determining the states across a shock front was derived from shock equations by enforcing conservation of mass and momentum. This was verified through a combination of experiments and direct measurements. The use of high-speed imaging and pressure bar measurements allowed this derivation to be independent of any constitutive model and showed that the assumptions in the commonly used rigid-perfectly-plastic-locking model are not applicable for dynamic impacts. A shock Hugoniot was generated from the test data to characterize the impact response of the foam. / text

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Thesis (M.Sc.) - University of Queensland, 2004. / Includes bibliography.

There is little process control employed at aggregate crushing plants and essentially no optimization at the primary or jaw crushing stage. Jaw crusher selection is very dependent on the subjective judgment/experience of individuals, the characterization of rock material using inadequate and unrepresentative tests, and the desire to limit secondary breakage, resulting in the conservative selection and operation of jaw crushers. A method for predicting the power consumption, product size, and volumetric capacity of jaw crushers based on fracture toughness has been proposed in this study. A new fracture toughness test, the Edge Notched Disk Wedge Splitting test, has been developed and verified in order to rapidly assess the fracture toughness of six quarry rocks. A High Energy Crushing Test system has been used to simulate the operational settings of a jaw crusher so that comparison of fracture toughness, specific comminution energy, and breakage distribution could be performed. The results indicate that the specific comminution energy required to reduce a rock particle to a given size increases with fracture toughness. The breakage distribution has also been shown to be dependent upon fracture toughness as long as the elastic modulus is taken into account. Laboratory jaw crushing experiments show that the capacity of a jaw crusher is dependent upon fracture toughness and the elastic modulus. Models for the prediction of power consumption, breakage function/product size, and volumetric capacity have been developed based on these results. At the experimental level, the models were able to predict the specific comminution energy to within 1% and t10 (characteristic crushing parameter) to within 10%. Prediction of the product size distribution produced by a lab-scale jaw crusher, for four different rocks, was within ± 5% (in terms of percent passing). The models allow for the selection of a jaw crusher based on the nature of the rock being broken and the average amount of size reduction done on the feed material. The models can also be used to optimize feed and operational settings, as well to determine the product size produced for a given rock and reduction ratio. / Ph. D.

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