Publications by Type: Conference Paper

1997
K. S. Ball and Taleff, E. M., “Can-in-Canister Alternative for Vitrification of Surplus Weapons Plutonium: Overview of Thermal Issues,” in Nuclear Materials Safety Management, Boston, 1997. LinkAbstract
One option for the long-term disposition of excess weapons plutonium involves vitrification, which entails combining the plutonium with radioactive high-level wastes and glass frit in a melter and then filling small stainless steel “cans” with the molten mixture. Several of these cans are then placed on a “rack” within larger stainless steel canisters, which are subsequently filled with molten high-level waste glass (HLWG) for security against theft. This disposition alternative is referred to as the “Can-in-Canister” option [1]. Of particular concern is the ability of the molten HLWG to flow around the Pu-cans and their support structure to form a proliferation barrier. The canister filling process is investigated experimentally using room temperature model fluids as well as molten HLWG surrogates. Also, analytical results obtained from thermal models and detailed simulations show the role of heat transfer on the temperature distribution within the HLWG, and consequently on the strongly temperature dependent viscosity of the HLWG and its ability to flow and fill the canister.
C. E. Aziz, Georgiou, G., and Speitel Jr, G. E., “Cometabolic Degradation of Chlorinated Solvent Mixtures by M. trichosporium OB3b PP358,” in In Situ and On-Site Bioremediation, Columbus, OH, 1997, vol. 3, pp. 79-84.
E. M. Taleff, Syn, C. K., Lesuer, D. R., and Sherby, O. D., “A Comparison of Mechanical Behavior in Pearlitic and Spheroidized Hypereutectoid Steels,” in Thermomechanical Processing and Mechanical Properties of Hypereutectoid Steels and Cast Irons, Warrendale, PA, 1997, pp. 127–142. LinkAbstract
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E. M. Taleff, Lesuer, D. R., Syn, C. K., and Henshall, G. A., “Creep Fracture During Solute-Drag Creep and Superplastic Deformation,” in Recent Advances in Fracture, Warrendale, PA, 1997, pp. 295–306. LinkAbstract
Creep fracture behavior has been studied in Al-Mg and Al-Mg-Mn alloys undergoing solute-drag creep and in microduplex stainless steel undergoing both solute-drag creep and superplastic deformation. Failure in these materials is found to be controlled by two mechanisms, neck formation and cavitation. The mechanism of creep fracture during solute-drag creep in Al-Mg is found to change from necking-controlled fracture to cavitation controlled fracture as Mn content is increased. Binary Al-Mg material fails by neck formation during solute-drag creep, and cavities are formed primarily in the neck region due to high hydrostatic stresses. Ternary alloys of Al-Mg- Mn containing 0.25 and 0.50 wt % Mn exhibit more uniform cavitation, with the 0.50 Mn alloy clearly failing by cavity interlinkage. Failure in the microduplex stainless steel is dominated by neck formation during solute-drag creep deformation but is controlled by cavity growth and interlinkage during superplastic deformation. Cavitation was measured at several strains, and found to increase as an exponential function of strain. An important aspect of cavity growth in the stainless steel is the long latency time before significant cavitation occurs. For a short latency period, cavitation acts to significantly reduce ductility below that allowed by neck growth alone. This effect is most pronounced in materials with a high strain-rate sensitivity, for which neck growth occurs very slowly.
C. Lee and Machemehl, R., “Global, local and iterative searches to the equilibrium network traffic signal setting problem,” in Transportation Research Forum, 39th Annual Meeting, Volume 2, 1997.Abstract
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E. M. Taleff, Bramfitt, B. L., Syn, C. K., Lesuer, D. R., and Sherby, O. D., “Mechanical Behavior of an Ultrahigh-Carbon Steel Exhibiting a Damask Surface Pattern,” in Thermomechanical Processing and Mechanical Properties of Hypereutectoid Steels and Cast Irons, Warrendale, PA, 1997, pp. 189–198. LinkAbstract
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C. C. Kou and Machemehl, R. B., “Probabilistic Aspect of Data Quality in Speed Estimation Through Video Image Technique,” in Conference on the Scientific Use of Statistical Software (9th). SoftStat’97, 1997.Abstract
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E. M. Taleff and Kim, W. - J., “The Roles of Grain-Boundary Sliding and Dislocation-Pipe Diffusion in High-Strain-Rate Superplasticity,” in Seventh International Conference on Creep and Fracture of Engineering Materials and Structures, Irvine, CA, 1997.Abstract
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D. R. Lesuer, Nieh, T. G., Syn, C. K., and Taleff, E. M., “Superplastic Deformation in Two Microduplex Stainless Steels,” in International Conference on Superplasticity in Advanced Materials (ICSAM), Bangalore, India, 1997.Abstract
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P. C. de Blanc, Brown, C. L., McKinney, D. C., Speitel Jr, G. E., and Pope, G. A., “Surfactant Flushing and Bioremediation - Striking a Balance,” in In Situ and On-Site Bioremediation, Columbus, OH, 1997, vol. 2, pp. 565-574.
1996
J. M. Symons, Xia, R., Diehl, A. C., Speitel Jr, G. E., Hwang, C. J., Krasner, S. W., and Barrett, S. E., “The Influence of Operational Variables on the Formation of Dissolved Organic Halogen During Chloramination,” in Water Disinfection and Natural Organic Matter: Characterization and Control, ACS Symposium Series 649, Washington, DC, 1996, pp. 78-104.
P. C. de Blanc, McKinney, D. C., and Speitel Jr, G. E., “Modeling Subsurface Biodegradation of Non-Aqueous Phase Liquids,” in Advances in Porous Media, Amsterdam, The Netherlands, 1996, vol. 3, pp. 1-82.
C. Lee and Machemehl, R. B., “Multiobjective Optimization of Equilibrium Network Signal Setting and Pricing,” in Transportation Research Forum, 38th Annual Meeting, Volume 2., 1996.Abstract
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S. C. Otis and Machemehl, R. B., “Predicting pedestrian safety at suburban signalized intersections,” in Compendium of Technical Papers for the 66th ITE Annual Meeting, 1996.Abstract
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C. C. Kou and Machemehl, R. B., “Super Street Long Term Improvement Schemes and Capacity Analysis: A Case Study,” in Transportation Research Forum, 38th Annual Meeting, Volume 2, 1996.Abstract
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1995
E. M. Taleff, Henshall, G. A., Lesuer, D. R., Nieh, T. G., and Wadsworth, J., “Enhanced Ductility of Coarse-Grain Al-Mg Alloys,” in Superplasticity and Superplastic Forming, 1995, pp. 3–10. LinkAbstract
Enhanced ductilities,i.e., values of tensile ductility exceeding those normally expected in metallic alloys, have been observed at warm temperatures in coarse-grained Al-Mg alloys which exhibit viscous-glide controlled creep. Numerous tests have been conducted in order to quantify this phe-nomenon over wide ranges of temperature and magnesium concentration. The contributions of strain-rate sensitivity and strain hardening have been analyzed in relation to the observed tensile ductilities. It is shown that an analysis based only on flow instability in tension cannot be used to predict failure in a unique manner.
E. M. Taleff, Henshall, G. A., Lesuer, D. R., Nieh, T. G., and Wadsworth, J., “Enhanced Tensile Ductility in Al-Mg Alloys by Solid-Solution Interactions,” in Aluminum and Magnesium for Automotive Applications, Warrendale, PA, 1995, pp. 125–134. LinkAbstract
The development of methods for obtaining high tensile elongation in aluminum alloys is of great importance for the practical forming of near-net-shape parts. Current superplastic alloys are limited in use by high material costs. The utilization of solute-drag creep processes, the approach used in this study, to obtain enhanced tensile ductility in aluminum alloys has lead to tensile elongations of up to 325% in simple, binary Al-Mg alloys with coarse grain sizes. This method has the advantage of lowering processing costs in comparison with superplastic alloys because a fine grain size is not necessary. Whereas superplastic alloys typically have a strain-rate sensitivity of m = 0.5, the enhanced ductility Al-Mg alloys typically exhibit m = 0.3 where maximum ductility is observed. Although a strain-rate sensitivity of rn = 0.5 can lead to elongations of over 1000% (superplastic materials) a value of m = 0.3 is shown experimentally to be sufficient for obtaining elongations of 150% to a maximum observed of 325%. Enhanced ductility is also affected strongly by ternary alloying additions, such as Mn, for which a preliminary understanding is pursued.
J. Wadsworth, Henshall, G. A., Nieh, T. G., and Taleff, E. M., “Materials Issues in Some Advanced Forming Techniques, Including Superplasticity,” in Emerging Technologies, 1995, pp. 87–94. LinkAbstract
From mechanics and macroscopic viewpoints, the sensitivity of the flow stress of a material to the strain rate, i.e. the strain rate sensitivity (m), governs the development of neck formation and therefore has a strong influence on the tensile ductility and hence formability of materials. Values of strain rate sensitivity range from unity, for the case of Newtonian viscous materials, to less than 0.1 for some dispersion strengthened alloys. Intermediate values of m = 0.5 are associated with classical superplastic materials which contain very fine grain sizes following specialized processing. An overview is given of the influence of strain rate sensitivity on tensile ductility and of the various materials groups that can exhibit high values of strain rate sensitivity. Recent examples of enhanced formability (or extended tensile ductility) in specific regimes between m = 1 and m = 0.3 are described, and potential areas for commercial exploitation are noted. These examples include: internal stress superplasticity, superplastic ceramics, superplastic intermetallics, superplastic laminated composites, superplastic behavior over six orders of magnitude of strain rate in a range of aluminum-based alloys and composites, and enhanced ductility in Al-Mg alloys that require no special processing for microstructural development.
S. C. Otis, Machemehl, R. B., and Mahmassani, H. S., “PREDICTING PEDESTRIAN VOLUMES BASED UPON LAND USE: A METHODOLOGY,” in Fifth National Conference on Transportation Planning Methods Applications-Volume I: A Compendium of Papers Based on a Conference Held in Seattle, Washington in April 1995, 1995.Abstract
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1994
E. M. Taleff, Henshall, G. A., Lesuer, D. R., and Nieh, T. G., “Warm Formability of Aluminum-Magnesium Alloys,” in Aluminum Alloys: Their Physical Properties and Mechanical Properties (ICAA4), Atlanta, Georgia: Georgia Institute of Technology, 1994, pp. 338–345.Abstract
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