Browsing by Author "Stevens, GT"

Now showing 1 - 7 of 7
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    Effect of irradiation on the mechanical properties of beryllium metal.
    (Australian Atomic Energy Commission, 1965-01) Stevens, GT; Hickman, BS
    Results are presented of mechanical property measurements on beryllium metal irradiated up to 6 x 1020 nvt > 1 MeV at 75 - 100ºC and 3.2 x 1020 nvt at 550ºC. The property changes are interpreted in terms of helium distribution in the material.
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    The effect of neutron irradiation on beryllium metal.
    (Australian Atomic Energy Commission, 1963-06) Hickman, BS; Stevens, GT
    This report summarises all the results obtained to date from a programme on the effects of neutron irradiation on the properties of beryllium metal. Results are presented on changes in density and mechanical properties in material fabricated by various routes and irradiated to fast neutron doses from 1019 nvt to 6 x 1023 nvt and at temperatures in the range 75ºC — 700ºC, Summaries of electron microscopy observations and electrical resistivity measurements, which are reported in more detail elsewhere., are also given, It is concluded that all the observed property changes can be interpreted in terms of the distribution of helium which is produced by fast neutron transmutation reactions in beryllium and that damage due to defect production is negligible for irradiation temperatures of 75ºC and above. Density changes duetoheiium bubble formation are shown to be very small but serious deterioration of mechanical properties can occur. The mechanical property changes and the distribution of helium are shown to be very dependent on material history and on the irradiation temperature. The standard Lucas Heights hot extruded material is shown to retain good mechanical properties for irradiation temperatures above 550ºC but serious loss of low temperature ductility is found to occur for irradiation temperatures below 500ºC, particularly in the range 300 — 500ºC, it is concluded that nucleation of gas bubbles at precipitate particles is the only satisfactory explanation of the wide variations in behaviour of beryllium metal fabricated by various methods.
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    The effects of reactive diluents on the mechanical behaviour of an anhydride- cured epoxy resin system
    (Australian Atomic Energy Commission, 1976-10) Stevens, GT; Lupton, AW
    A study was made of, the tensile behaviour at room temperature, 75ºC and 100ºC, of diglycidyl ether of bisphenol A resin systems modified by the introduction of (i) a linear mono-epoxide aliphatic glycidyl ether, (ii) a highly branched mono-epoxide glycidyl ester of a saturated tertiary mono-carboxylic acid, (iii) a mixture of the linear mono-glycidyl and diglycidyl ethers of butanediol and (iv) a low viscosity diepoxide and also an elastomer (Hycar CTBN). Resin systems showing relatively high elongation to failure without severe degradation of strength or stiffness at elevated temperatures were obtained.
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    Microstructural aspects of SYNROC from sandia precursor - 1. some effects of process variables.
    (Australian Atomic Energy Commission, 1987-04) Stevens, GT; Watson, KG; Bellrose, A
    Typical microstructures formed in Synroc C have been observed by optical and scanning electron microscopy. The principal effects of segregation variation of calciner atmosphere and change in hot-pressing conditions are summarised.
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    Microstructural aspects of SYNROC from sandia precursor - 2. some effects of impurities
    (Australian Atomic Energy Commission, 1987-04) Stevens, GT; Watson, KG; Bellrose, A
    A description is given of the effects of small amounts of certain elements (Si Na P Fe Cl F and S) which could be considered to be processing contaminants on the microstructure of a particular batch of Synroc C.
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    The relationship between microcracking and mechanical properties in neutron-irradiated beryllium oxide
    (Australian Atomic Energy Commission, 1964-08) Hanna, GL; Stevens, GT; Hickman, BS
    Beryllium oxide bend test specimens of two grain sizes, 1—2 microns and 8—35 microns, were irradiated to fast neutron doses of up to 5 .6 x 1020 nvt (above 1 MeV) at 75 — 100ºC. Specimens were examined by X—ray line breadth (30.0 reflection), modulus of rupture, elastic modulus, open porosity, and lattice parameter measurements. The results show that there is no significant change in mechanical properties up to the dose at which microcracking is first observed i.e. .5 x 1020 nvt in the case of the fine grain size material and 1.2 x 1020 nvt in the case of the coarse grain size material. Above these doses the modulus of rupture and the apparent elastic constants fall rapidly. Microcracking occurred at an earlier dose in both materials than would have been expected from earlier work.
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    Transverse cracking in orthotropic glass fibre/epoxy resin composites
    (Australian Atomic Energy Commission, 1976-10) Stevens, GT; Lupton, AW
    The transverse cracking in glass-fibre composites based on (i) an unmodified epoxy resin system, (ii) a flexibilised epoxy system and (iii) an epoxy containing an elastomeric toughening agent, was studied under direct tensile loading and repeated tensile loading at room temperature, 75ºC and 100ºC. It was found that when the resin is in the glassy state, the final crack spacing and the relationship between stress and crack spacing can be explained in terms of shear stress transfer from the longitudinal plies. If the toughness of the resin is sufficient to allow slow crack growth, a more closely spaced array of irregular cracks is formed. The elastic modulus of the laminate is lowered by transverse cracking, but the modulus in both the cracked and uncracked state is not greatly affected by the modulus of the resin. The high ductility of the resins in the rubbery state is not sufficient to prevent transverse cracking although, because of the very low modulus of the resin in this state, such cracking is not accompanied by large reductions in the stiffness of the laminate.