Drawn and annealed copper wires of diameters ranging from 50 μ to 900 μ were tested in tension and the results examined for evidence of size-effects. No size-effect on yield-stress or work-hardening rate has been definitely established. The results were discussed in terms of the fraction of the number of grains in the specimen which have a free surface. The ultimate tensile strength and ductility decrease with decreasing diameter
for diameters below 200 μ. An explanation has been put forward in terms of void-formation during deformation.
Polycrystals and single crystals of copper were tested at room
temperature with the strain-rate cycled between 10⁻¹ min⁻¹ and 10⁻³ min⁻¹.
Polycrystalline copper obeys the Cottrell-Stokes law but shows a variation in the ratio of flow-stresses with varying grain diameter and with a varying value of the fraction of grains in the specimen which show a free surface. Copper specimens were also tested with the temperature cycled between 78°K and 293°K. Copper polycrystals do not obey the Cottrell-Stokes law, the deviation depending on the grain size. These results are discussed in terms of stacking-fault energy and several possible explanations are considered.
Aluminum polycrystals were tested with the temperature cycled between 78°K and 293°K. Aluminum obeys the Cottrell-Stokes law for temperature variation. A work-softening effect accompanies the yield-drop found at 293°K after prior deformation at 78°K. This was discussed in terms of cross-slip and dislocation climb mechanisms. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/39616 |
| Date | January 1961 |
| Creators | Costanzo, Ronald Albert Joseph |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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