56 Matching Results

Search Results

Advanced search parameters have been applied.

Cryogenic Treatment of Production Components in High-Wear Rate Wells

Description: Deep Cryogenic Tempering (DCT) is a specialized process whereby the molecular structure of a material is ''re-trained'' through cooling to -300 F and then heating to +175-1100 F. Cryocon, Inc. (hereafter referred to as Cryocon) and RMOTC entered an agreement to test the process on oilfield production components, including rod pumps, rods, couplings, and tubing. Three Shannon Formation wells were selected (TD about 500 ft) based on their proclivity for high component wear rates. Phase 1 of the test involved operation for a nominal 120 calendar day period with standard, non-treated components. In Phase 2, treated components were installed and operated for another nominal 120 calendar day period. Different cryogenic treatment profiles were used for components in each well. Rod pumps (two treated and one untreated) were not changed between test phases. One well was operated in pumped-off condition, resulting in abnormal wear and disqualification from the test. Testing shows that cryogenic treatment reduced wear of rods, couplers, and pump barrels. Testing of production tubing produced mixed results.
Date: April 29, 2002
Creator: Milliken, M.
Partner: UNT Libraries Government Documents Department

Quantum Mechanical Single Molecule Partition Function from Path Integral Monte Carlo Simulations

Description: An algorithm for calculating the partition function of a molecule with the path integral Monte Carlo method is presented. Staged thermodynamic perturbation with respect to a reference harmonic potential is utilized to evaluate the ratio of partition functions. Parallel tempering and a new Monte Carlo estimator for the ratio of partition functions are implemented here to achieve well converged simulations that give an accuracy of 0.04 kcal/mol in the reported free energies. The method is applied to various test systems, including a catalytic system composed of 18 atoms. Absolute free energies calculated by this method lead to corrections as large as 2.6 kcal/mol at 300 K for some of the examples presented.
Date: October 1, 2006
Creator: Chempath, Shaji; Bell, Alexis T. & Predescu, Cristian
Partner: UNT Libraries Government Documents Department

AISI/DOE Technology Roadmap Program: Development of Appropriate Resistance Spot Welding Practice for Transformation-Hardened Steels

Description: This report describes work accomplished in the project, titled ''Development of Appropriate Resistance Spot Welding Practice for Transformation-Hardened Steels.'' The Phase 1 of the program involved development of in-situ temper diagrams for two gauges of representative dual-phase and martensitic grades of steels. The results showed that tempering is an effective way of reducing hold-time sensitivity (HTS) in hardenable high-strength sheet steels. In Phase 2, post-weld cooling rate techniques, incorporating tempering, were evaluated to reduce HTS for the same four steels. Three alternative methods, viz., post-heating, downsloping, and spike tempering, for HTS reduction were investigated. Downsloping was selected for detailed additional study, as it appeared to be the most promising of the cooling rate control methods. The downsloping maps for each of the candidate steels were used to locate the conditions necessary for the peak response. Three specific downslope conditions (at a fix ed final current for each material, timed for a zero-, medium-, and full-softening response) were chosen for further metallurgical and mechanical testing. Representative samples, were inspected metallographically, examining both local hardness variations and microstructures. The resulting downslope diagrams were found to consist largely of a C-curve. The softening observed in these curves, however, was not supported by subsequent metallography, which showed that all welds made, regardless of material and downslope condition, were essentially martensitic. CCT/TTT diagrams, generated based on microstructural modeling done at Oak Ridge National Laboratories, showed that minimum downslope times of 2 and 10 s for the martensitic and dual-phase grades of steels, respectively, were required to avoid martensite formation. These times, however, were beyond those examined in this study. These results show that downsloping is not an effective means of reducing HTS for production resistance spot welding (RSW). The necessary downslope times (2-10s) are prohibited by the welding rates currently used today (up to 60 ...
Date: July 8, 2002
Creator: Chuko, Wayne & Gould, Jerry
Partner: UNT Libraries Government Documents Department

Biomolecular Simulation Using Amber and CHARMM

Description: This project supports the development of software using terascale computers to carry out molecular simulations of protein function and macromolecular interactions. We are building on the existing CHARMM and Amber simulation packages, adapting them in novel ways to massively parallel architectures and high-performance CPUs. Three principal avenues being pursued are: (1) Improvements in load-balancing and communication for large-scale particle-mesh Ewald (PME) simulations of solvated biomolecules. (2) Modern techniques for accelerating convergence of sampling of configuration space offer promise for further exploitation of massively parallel architectures. These methods include parallel tempering and ''lambda dynamics'' procedures that connect multiple, synchronized results from PME simulations like those described in part [1]. (3) The implementation of efficient and scalable algorithms that move towards lower-resolution models in ways that can be carefully calibrated against atomic-level solvated simulations.
Date: November 29, 2004
Creator: Case, David A. & Brooks, Charles L., III
Partner: UNT Libraries Government Documents Department

Tempered glass

Description: This document describes a demonstration for making tempered glass using minimal equipment. The demonstration is intended for a typical student of materials science, at the high school level or above. (JL)
Date: November 1, 1991
Creator: Bunnell, L.R.
Partner: UNT Libraries Government Documents Department

Tempered glass

Description: This document describes a demonstration for making tempered glass using minimal equipment. The demonstration is intended for a typical student of materials science, at the high school level or above. (JL)
Date: November 1, 1991
Creator: Bunnell, L. R.
Partner: UNT Libraries Government Documents Department

Advanced Pressure Boundary Materials

Description: Increasing the operating temperatures of fossil power plants is fundamental to improving thermal efficiencies and reducing undesirable emissions such as CO{sub 2}. One group of alloys with the potential to satisfy the conditions required of higher operating temperatures is the advanced ferritic steels such as ASTM Grade 91, 9Cr-2W, and 12Cr-2W. These are Cr-Mo steels containing 9-12 wt% Cr that have martensitic microstructures. Research aimed at increasing the operating temperature limits of the 9-12 wt% Cr steels and optimizing them for specific power plant applications has been actively pursued since the 1970's. As with all of the high strength martensitic steels, specifying upper temperature limits for tempering the alloys and heat treating weldments is a critical issue. To support this aspect of development, thermodynamic analysis was used to estimate how this critical temperature, the A{sub 1} in steel terminology, varies with alloy composition. The results from the thermodynamic analysis were presented to the Strength of Weldments subgroup of the ASME Boiler & Pressure Vessel Code and are being considered in establishing maximum postweld heat treatment temperatures. Experiments are also being planned to verify predictions. This is part of a CRADA project being done with Alstom Power, Inc.
Date: January 1, 2007
Creator: Santella, Michael L. & Shingledecker, John P.
Partner: UNT Libraries Government Documents Department

Development of Appropriate Spot Welding Practice for Advanced High Strength Steels (TRP 0114)

Description: This program evaluated the effects of common manufacturing variables on spike-tempering effectiveness. The investigation used design-of-experiment (DOE) techniques, and examined both dual-phase and martensitic grades of high-strength steels (HSS). The specific grades chosen for this project were: Dual-phase (DP) 600, galvannealed (GA), 1.55 mm (DP) 600; Dual-phase (DP) 980 (uncoated), 1.55 mm (DP) 980; and Martensitic (M) 1300, 1.55 mm (M) 1300. Common manufacturing conditions of interest included tempering practice (quench and temper time), button size, simulated part fitup (sheet angular misalignment and fitup), and electrode wear (increased electrode face diameter). All of these conditions were evaluated against mechanical performance (static and dynamic tensile shear). Weld hardness data was also used to examine correlations between mechanical performance and the degree of tempering. Mechanical performance data was used to develop empirical models. The models were used to examine the robustness of weld strength and toughness to the selected processing conditions. This was done using standard EWI techniques. Graphical representations of robustness were then coupled with metallographic data to relate mechanical properties to the effectiveness of spike tempering. Mechanical properties for all three materials were relatively robust to variation in tempering. Major deviations in mechanical properties were caused by degradation of the weld itself. This was supported by a lack of correlation between hardness data and mechanical results. Small button sizes and large electrode face diameters (worn electrodes) produced large reductions in both static and dynamic strength levels when compared to standard production setups. Dynamic strength was further degraded by edge-located welds.
Date: September 17, 2004
Creator: Girvin, Brian; Peterson, Warren & Gould, Jerry
Partner: UNT Libraries Government Documents Department

The Effect of Casting Variables and Heat Treatment on the Tensile Properties of Lead-0.02 to 0.10 Weight Per Cent Calcium Alloy

Description: Some of the controllable variables have been investigated in casting of lead alloys having 0.06 to 0.09 wt.% Ca. The alloy has been found to respond to solution heat-treatment, room-temperature precipitation hardening, and accelerated hardening at 100 ts C. Tensile strengths to 7000 psi have been obtained. (auth)
Date: February 25, 1960
Creator: Townsend, A. B.
Partner: UNT Libraries Government Documents Department

Continuous austempering fluidized bed furnace. Final report

Description: The intended objective of this project was to show the benefits of using a fluidized bed furnace for austenitizing and austempering of steel castings in a continuous manner. The division of responsibilities was as follows: (1) design of the fluidized bed furnace--Kemp Development Corporation; (2) fabrication of the fluidized bed furnace--Quality Electric Steel, Inc.; (3) procedure for austempering of steel castings, analysis of the results after austempering--Texas A and M University (Texas Engineering Experiment Station). The Department of Energy provided funding to Texas A and M University and Kemp Development Corporation. The responsibility of Quality Electric Steel was to fabricate the fluidized bed, make test castings and perform austempering of the steel castings in the fluidized bed, at their own expense. The project goals had to be reviewed several times due to financial constraints and technical difficulties encountered during the course of the project. The modifications made and the associated events are listed in chronological order.
Date: September 23, 1997
Creator: Srinivasan, M.N.
Partner: UNT Libraries Government Documents Department


Description: In a comparison of Ni and stainless steel subsize tensile specimens, it was found that property changes induced by irradiation to an estimated fast flux of 4 x 10/sup 20/ nvt were qualitatively similar to those produced by cold working. No basis for direct correlation was found. Tensile properties, elongation, hardness, density, electrical resistivity, corrosion, and annealing results are presented. It was determined that irradiation left the nickel and stainless steel specimens more ductile than did cold working to a comparable ultimate strength. Radiation hardening was found to be completely removed by a 1- hr anneal at 500 deg C, whereas temperatures of 600 to 800 deg C were required to anneal coldwork hardening. (auth)
Date: July 1, 1960
Creator: Paine, S.H.; Murphy, W.F. & Hackett, D.W.
Partner: UNT Libraries Government Documents Department

Parallel tempering Monte Carlo in LAMMPS.

Description: We present here the details of the implementation of the parallel tempering Monte Carlo technique into a LAMMPS, a heavily used massively parallel molecular dynamics code at Sandia. This technique allows for many replicas of a system to be run at different simulation temperatures. At various points in the simulation, configurations can be swapped between different temperature environments and then continued. This allows for large regions of energy space to be sampled very quickly, and allows for minimum energy configurations to emerge in very complex systems, such as large biomolecular systems. By including this algorithm into an existing code, we immediately gain all of the previous work that had been put into LAMMPS, and allow this technique to quickly be available to the entire Sandia and international LAMMPS community. Finally, we present an example of this code applied to folding a small protein.
Date: November 1, 2003
Creator: Rintoul, Mark Daniel; Plimpton, Steven James & Sears, Mark P.
Partner: UNT Libraries Government Documents Department

Stressed glass technology for actuators and removable barrier applications.

Description: There are commercial and military applications in which a material needs to serve as a barrier that must subsequently be removed. In many cases it is desirable that once the barrier has served its function that it then be reduced to small pieces. For example, in pipelines and in downhole drilling applications, valves are needed to function as barriers that can sustain high pressures. Later the valves must be removed and essentially disappear or be rendered to such a small size that they do not interfere with the functioning of other equipment. Military applications include covers on missile silos or launch vehicles. Other applications might require that a component be used once as an actuator or for passive energy storage, and then be irreversibly removed, again so as not to interfere with the function or motion of other parts of the device. Brittle materials, especially those that are very strong, or are pre-stressed, are ideal candidates for these applications. Stressed glass can be produced in different sizes and shapes and the level of strength and pre-stress, both of which control the fragmentation, can be manipulated by varying the processing. Stressed glass can be engineered to fracture predictably at a specific stress level. Controlling the central tension allows the fragment size to be specified. The energy that is stored in the residual stress profile that results from ion exchange or thermal tempering processes can be harnessed to drive fragmentation of the component once it has been deliberately fractured. Energy can also be stored in the glass by mechanical loading. Energy from both of these sources can be released either to perform useful work or to initiate another reaction. Once the stressed glass has been used as a barrier or actuator it can never be ''used'' again because it fragments into many ...
Date: July 1, 2007
Creator: Schwing, Kamilla, J.; Warren, Mial E.; Glass, Sarah Jill & Tappan, Alexander Smith
Partner: UNT Libraries Government Documents Department

Effect of single-point sequence alterations on the aggregationpropensity of a model protein

Description: Sequences of contemporary proteins are believed to have evolved through process that optimized their overall fitness including their resistance to deleterious aggregation. Biotechnological processing may expose therapeutic proteins to conditions that are much more conducive to aggregation than those encountered in a cellular environment. An important task of protein engineering is to identify alternative sequences that would protect proteins when processed at high concentrations without altering their native structure associated with specific biological function. Our computational studies exploit parallel tempering simulations of coarse-grained model proteins to demonstrate that isolated amino-acid residue substitutions can result in significant changes in the aggregation resistance of the protein in a crowded environment while retaining protein structure in isolation. A thermodynamic analysis of protein clusters subject to competing processes of folding and association shows that moderate mutations can produce effects similar to those caused by changes in system conditions, including temperature, concentration, and solvent composition that affect the aggregation propensity. The range of conditions where a protein can resist aggregation can therefore be tuned by sequence alterations although the protein generally may retain its generic ability for aggregation.
Date: October 7, 2005
Creator: Bratko, Dusan; Cellmer, Troy; Prausnitz, John M. & Blanch, Harvey W.
Partner: UNT Libraries Government Documents Department


Description: >The corrosion resistance of mantensitic and ferritic austenitic stainless steels and carbon steels in pressurized water at 500 to 600 deg F is compared. Included are specific out-of-pile data for austenitic stainless steels, AISI types types 410, 420, 431, and 440C; the ferritic AISI types 430, 442, and 446; the precipitation-hardening type 17-4PH; and carbon steels, ASTM 212 A and B. Available corrosion results obtained under irradiation at exposures in the range of 7 x 10/sup 16/ to 3 x 10/sup 19/ nvt are also included for types 304, types of martensitic and ferritic stainless steels which were evaluated do not contain nickel. For application where it is desirable to minimize Co/sup 58/ activity produced from nickel, selection of a martensitic or ferritic stainless steel may be more appropriate than choosing the more popular nickel-bearing austenitic stainless steel or a fuel-element cladding material. Interpretation of the data indicates that, on the average, martensitic and ferritic stainless steels corrode more rapidly than austenitic alloys but more slowly than carbon and low-alloy steels. Under selected controlled water conditions or under irradiation, the corrosion of the nickel-free stainless steels appears to differ little from the austenitics. The corrosion of martensitic and ferritic stainless steels in pressurized-water systems therefore does not appear of such magnitude as to rule out development of these materials as the cladding fuel elements for specific applications. (auth)
Date: July 16, 1963
Creator: Beaver, R.J. & Leitten, C.F. Jr.
Partner: UNT Libraries Government Documents Department

Laser welding and post weld treatment of modified 9Cr-1MoVNb steel.

Description: Laser welding and post weld laser treatment of modified 9Cr-1MoVNb steels (Grade P91) were performed in this preliminary study to investigate the feasibility of using laser welding process as a potential alternative to arc welding methods for solving the Type IV cracking problem in P91 steel welds. The mechanical and metallurgical testing of the pulsed Nd:YAG laser-welded samples shows the following conclusions: (1) both bead-on-plate and circumferential butt welds made by a pulsed Nd:YAG laser show good welds that are free of microcracks and porosity. The narrow heat affected zone has a homogeneous grain structure without conventional soft hardness zone where the Type IV cracking occurs in conventional arc welds. (2) The laser weld tests also show that the same laser welder has the potential to be used as a multi-function tool for weld surface remelting, glazing or post weld tempering to reduce the weld surface defects and to increase the cracking resistance and toughness of the welds. (3) The Vicker hardness of laser welds in the weld and heat affected zone was 420-500 HV with peak hardness in the HAZ compared to 240 HV of base metal. Post weld laser treatment was able to slightly reduce the peak hardness and smooth the hardness profile, but failed to bring the hardness down to below 300 HV due to insufficient time at temperature and too fast cooling rate after the time. Though optimal hardness of weld made by laser is to be determined for best weld strength, methods to achieve the post weld laser treatment temperature, time at the temperature and slow cooling rate need to be developed. (4) Mechanical testing of the laser weld and post weld laser treated samples need to be performed to evaluate the effects of laser post treatments such as surface remelting, glazing, re-hardening, or tempering ...
Date: April 3, 2012
Creator: Xu, Z. (Nuclear Engineering Division)
Partner: UNT Libraries Government Documents Department

Summary of failure analysis activities at Brookhaven National Laboratory

Description: Brookhaven National Laboratory has for many years conducted examinations related to the failures of nuclear materials and components. These examinations included the confirmation of root cause analyses, the determination of the causes of failure, identification of the species that accelerate corrosion, and comparison of the results of nondestructive examinations with those obtained by destructive examination. The results of those examinations, which had previously appeared in various formats (formal and informal reports, journal articles, etc.), have been collected together and summarized in the present report. The report is divided into sections according to the general subject matter (for example, corrosion, fatigue, etc.). Each section presents summaries of the information contained in specific reports and publications, all of which are fully identified as to title, authors, report number or journal reference, date of publication, and FIN number under which the work was performed.
Date: October 1, 1996
Creator: Cowgill, M.G.; Czajkowski, C.J. & Franz, E.M.
Partner: UNT Libraries Government Documents Department

Metal cutting simulation of 4340 steel using an accurate mechanical description of meterial strength and fracture

Description: Strength and fracture constitutive relationships containing strain rate dependence and thermal softening are important for accurate simulation of metal cutting. The mechanical behavior of a hardened 4340 steel was characterized using the von Mises yield function, the Mechanical Threshold Stress model and the Johnson- Cook fracture model. This constitutive description was implemented into the explicit Lagrangian FEM continuum-mechanics code EPIC, and orthogonal plane-strain metal cutting calculations were performed. Heat conduction and friction at the toolwork-piece interface were included in the simulations. These transient calculations were advanced in time until steady state machining behavior (force) was realized. Experimental cutting force data (cutting and thrust forces) were measured for a planning operation and compared to the calculations. 13 refs., 6 figs.
Date: September 1, 1996
Creator: Maudlin, P.J. & Stout, M.G.
Partner: UNT Libraries Government Documents Department

Development of Diffusion-Type Bonding Techniques for Berylco-25 Alloy

Description: Bond tensile strengths in excess of 90,000 psi in joining precipitation- hardened beryllium -copper have been obtained by diffusion techniques. Ordinary brazing techniques for beryllium--copper have resulted in an average of 40,000- psi tensile strength in the bond. Bonds with tensile strengths averaging 108,400 psi have been developed using high-vacuum, diffusion-type bonding techniques. Hardnesses averaging 38 Rockwell C'' can be obtained by air-blast cooling of the beryllium-copper after solution heat treatment (followed by precipitation hardening). (R.J.S.)
Date: September 1, 1961
Creator: Baxter, G.R.; Hoffman, J.A.; Bertossa, R.C. & Cottrell, B.R.
Partner: UNT Libraries Government Documents Department