Publications by Type: Conference Paper

2013
H. Daigle and Dugan, B., “Unlocking the Secrets of Subsalt Sedimentary Environments,” in Chikyu+10 International Workshop, Tokyo, Japan, 2013.
2012
J. Lee, Morovat, A., Engelhardt, M., and Taleff, E., “Creep Behavior of ASTM A992 Steel at Elevated Temperatures,” in Proceedings, 7th International Conference on Structures in Fire (SiF), Zurich, Switzerland, 2012. Publisher's Version
P. A. Sherek, Carpenter, A. J., Louis G. Hector, J., Krajewski, P. E., Carter, J. T., Lasceski, J., and Taleff, E. M., “The Effects of Strain and Stress Sate in Hot Forming of Mg AZ31 Sheet,” in Magnesium Technology 2012, TMS Annual Meeting, Orlando, FL, 2012. Publisher's VersionAbstract
Wrought magnesium alloys, such as AZ31 sheet, are of considerable interest for light-weighting of vehicle structural components. The poor room-temperature ductility of AZ31 sheet has been a hindrance to forming the complex part shapes necessary for practical applications. However, the outstanding formability of AZ31 sheet at elevated temperature provides an opportunity to overcome that problem. Complex demonstration components have already been produced at 450°C using gas-pressure forming. Accurate simulations of such hot, gas-pressure forming will be required for the design and optimization exercises necessary if this technology is to be implemented commercially. We report on experiments and simulations used to construct the accurate material constitutive models necessary for finite-element-method simulations. In particular, the effects of strain and stress state on plastic deformation of AZ31 sheet at 450°C are considered in material constitutive model development. Material models are validated against data from simple forming experiments.
A. Morovat, Engelhardt, M., Helwig, T., and Taleff, E., “High-Temperature Creep Buckling Phenomenon of Steel Columns Subjected to Fire,” in Proceedings, 7th International Conference on Structures in Fire (SiF), Zurich, Switzerland, 2012. Publisher's Version
M. Morovat, Engelhardt, M., Helwig, T., and Taleff, E., “Investigation of Time-Dependent Buckling of Steel Columns Exposed to Fire Temperatures,” 2012, pp. 2095–2106. Publisher's VersionAbstract
One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of applied load. The phenomenon of time-dependent buckling can have a significant impact on the safety of steel columns subjected to fire. This phenomenon has received relatively little research attention, and is not currently explicitly considered in code-based design formulas for columns at elevated temperatures, such as those in the Eurocode 3 or those in the AISC Specification. This paper presents some results of on-going research, which aims at developing analytical, computational and experimental predictions of the phenomenon of creep buckling in steel columns subjected to fire. Analytical solutions using the concept of time-dependent tangent modulus are developed to model time-dependent buckling behavior of steel columns at elevated temperatures. Results from computational creep buckling studies using Abaqus are also presented, and compared with analytical predictions. Material creep data on ASTM A992 steel is also presented in the paper and compared to existing creep models for structural steel at high temperatures. Both analytical and computational methods utilize material creep models for structural steel developed by Harmathy, by Fields and Fields, and by the authors. Predictions from this study are also compared against those from Eurocode 3 and the AISC Specification. Results of this work show that neglecting creep effects can lead to erroneous and potentially unsafe predictions of the strength of steel columns subjected to fire.
J. T. Lee, Carpenter, A. J., Jodlowski, J. P., and Taleff, E. M., “Predicting Hot Deformation of AA5182 Sheet,” in In Proceedings of the 13th International Conference on Aluminum Alloys (ICAA-13), Pittsburgh, PA, 2012. Publisher's Version
2011
C. N. Dolder, Villanueva, M. A., Haberman, M. R., and Tinney, C. E., “Application of boundary layer suction for reducing hydrophone sensing noise,” in 162nd Meeting of the Acoustical Society of America, San Diego, CA, 2011, vol. 130:4, Pt 2.
M. Morovat, Engelhardt, M., Helwig, T., and Taleff, E., “Creep Buckling of Steel Columns Subjected to Fire,” in In Proceedings of the 35th International Symposium on Bridge and Structural Engineering, London, England, 2011. Publisher's VersionAbstract
One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of applied load. Although material creep and consequently the phenomenon of creep buckling can significantly impact the safety of steel columns subjected to fire, they have received relatively little research attention, and are not currently explicitly considered in code-based design formula for columns at elevated temperatures, such as those in the Eurocode 3 or in the AISC Specification. This paper will propose a preliminary methodology to study the phenomenon of creep buckling in steel columns subjected to fire. Preliminary analytical solutions are presented, and compared with computational predictions for creep buckling. The analytical and computational results clearly indicate that accurate knowledge of material creep is essential in studying creep buckling phenomenon at elevated temperatures. In addition, the results show that neglecting creep effects can lead to erroneous and potentially unsafe predictions of the strength of steel columns subjected to fire.
H. Daigle, Bangs, N., and Dugan, B., “Transient pressures, hydraulic fracturing, and gas migration at southern Hydrate Ridge: Geophysical observations and flow modeling,” in 7th International Conference on Gas Hydrates, Edinburgh, UK, 2011.
2010
E. M. Taleff, Takata, K., and Ichitani, K., “Hot and Warm Deformation of AA5182 Sheet Materials: Ductility and Microstructure Evolution,” in Proceedings of the 12th International Conference on Aluminum Alloys, September 5–9, 2010, 2010, pp. 1231–1236.Abstract
Not available.
E. Bakolas and Tsiotras, P., “Minimum-Time Paths for a Light Aircraft in the Presence of Regionally-Varying Strong Winds,” in AIAA Infotech ’’AT’’ Aerospace, Atlanta, Georgia, 2010.
C. N. Dolder, Haberman, M. R., and Tinney, C. E., “Turbulent Boundary Layers over Receiver Arrays,” in 159th Acoustical Society of America Meeting, NOISE-CON, Baltimore, MD, 2010, vol. 127:3, Pt 2.
2009
Y. Shi, Jiao, D., Schnieders, M. J., and Ren, P., “Trypsin-ligand binding free energy calculation with AMOEBA,” in Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE, 2009, pp. 2328–2331.
2007
C. E. Tinney, Bonnet, J. - P., and Delville, J., “Stochastic estimation: structure eduction techniques for turbulent flows and other dynamical systems,” in Schloss Dagstuhl Seminar–07121: Experimental fluid mechanics, computer vision and pattern recognition, Wadern, Germany, 2007.
2006
J. R. Ciulik and Taleff, E. M., “Dynamic Abnormal Grain Growth in Commercial-Purity Molybdenum,” in Proceedings of the 2006 International Conference on Tungsten, Refractory & Hardmetals {VI}, Orlando, Florida, 2006, pp. CD ROM. Similar link, UT RespositoryAbstract
In this experimental investigation, the tensile creep behavior of commercial-purity molybdenum sheet at temperatures between 1300°C and 1700°C is critically evaluated, based upon experimental creep testing and microstructural characterizations. The high-temperature properties of molybdenum are of interest because there are many applications in which molybdenum and molybdenum alloys are used at elevated temperatures. Understanding of the creep mechanisms and the constitutive relations between stress and strain at elevated temperatures is needed in order to determine if molybdenum is an appropriate choice for a given high-temperature design application and to accurately predict its creep life. The creep behavior of two commercially-available grades of molybdenum was determined using short-term creep tests (1/2 to 14 hours) at slow to moderate true-strain rates of 10⁻⁶ to 10⁻⁴ s⁻¹ and temperatures between 1300°C and 1700°C. High-temperature, uniaxial tensile testing was used to produce data defining the relationship between tensile creep strain-rate and steady-state flow stress at four temperatures: 1340°C, 1440°C, 1540°C, 1640°C. Microstructural changes that occurred during creep testing were evaluated and compared to changes resulting from elevated temperature exposure alone. Mechanisms for dynamic abnormal grain growth that occurred during creep testing and the causes of the microstructural changes that occurred as a function of temperature are discussed.
E. M. Taleff, “Overview of 5000-Series Aluminum Materials for Hot Forming in the Automotive Industry,” in Aluminum Wrought Products for Automotive, Packaging, and Other Applications - The James Morris Honorary Symposium, 2006, pp. 87–96.Abstract
Not available.
A. R. Tsyganov, Warrenchuk, N. M., and Machemehl, R. B., “Safety Impact of Edge Lines on Rural Two-Lane Highways in Texas,” in Research into Practice: 22nd ARRB Conference, 2006.Abstract
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N. E. Lownes and Machemehl, R. B., “VISSIM: a multi-parameter sensitivity analysis,” in Simulation Conference, 2006. WSC 06. Proceedings of the Winter, 2006, pp. 1406–1413.Abstract
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2005
J. R. Ciulik and Taleff, E. M., “Abnormal Dynamic Grain Growth During Creep Deformation of Powder-Metallurgy (PM) Grade Molybdenum Sheet,” in Proceedings of the Space Nuclear Conference 2005 (American Nuclear Society), San Diego, CA, 2005, pp. 790–796.Abstract
No abstract available.
A. R. Tsyganov, Mohan, D. N., and Machemehl, R. B., “Analysis of accident statistics on urban arterial street work zones,” in 12th World Congress on Intelligent Transport Systems, 2005.Abstract
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