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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Dynamic and Quasi-Static Mechanical Properties of Fe-Ni Alloy Honeycomb

Clark, Justin Lewis 12 April 2004 (has links)
Several metal honeycombs, termed Linear Cellular Alloys (LCAs), were fabricated via a paste extrusion process and thermal treatment. Two Fe-Ni based alloy compositions were evaluated. Maraging steel and Super Invar were chosen for their compatibility with the process and the wide range of properties they afforded. Cell wall material was characterized and compared to wrought alloy specifications. The bulk alloy was found to compare well with the more conventionally produced wrought product when porosity was taken into account. The presence of extrusion defects and raw material impurities were shown to degrade properties with respect to wrought alloys. The performance of LCAs was investigated for several alloys and cell morphologies. The results showed that out-of-plane properties exceeded model predictions and in-plane properties fell short due to missing cell walls and similar defects. Strength was shown to outperform several existing cellular metals by as much as an order of magnitude in some instances. Energy absorption of these materials was shown to exceed 150 J/cc at strains of 50% for high strength alloys. Finally, the suitability of LCAs as an energetic capsule was investigated. The investigation found that the LCAs added significant static strength and as much as three to five times improvement in the dynamic strength of the system. More importantly, it was shown that the pressures achieved with the LCA capsule were significantly higher than the energetic material could achieve alone. High pressures, approaching 3 GPa, coupled with the fragmentation of the capsule during impact increased the likelihood of initiation and propagation of the energetic reaction. This multi-functional aspect of the LCA makes it a suitable capsule material.
2

The Dynamic Yielding of Mild Steel

Harpalani, Kalyan 05 1900 (has links)
<p> Dynamic stress tests were performed on mild steel samples. The material parameters 'n' and 'G(εᵣ, tₒ)', defined as 'stress dislocation velocity exponent' and 'flow function' respectively, were evaluated using the equation "σₘⁿtₒ K(n) = G(εᵣ, tₒ)" as proposed by Kardos (1). The values determined for 'n' are in agreement with the results obtained by other researchers using different techniques. </p> <p> The equipment for studying the response of materials to dynamic loading was modified to permit a wider duration range for the loading. </p> <p> A technique was developed to monitor the pressure of the oil in the intensifier throughout the entire loading cycle. </p> / Thesis / Master of Engineering (ME)

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