Four Papers by the Supernova Cosmology Project (open access)

Four Papers by the Supernova Cosmology Project

Our search for high-redshift Type Ia supernovae discovered, in its first years, a sample of seven supernovae. Using a 'batch' search strategy, almost all were discovered before maximum light and were observed over the peak of their light curves. The spectra and light curves indicate that almost all were Type Ia supernovae at redshifts z = 0.35 - 0.5. These high-redshift supernovae can provide a distance indicator and 'standard clock' to study the cosmological parameters q{sub 0}, {Lambda}, {Omega}{sub 0}, and H{sub 0}. This presentation and the following presentations of Kim et al. (1996), Goldhaber et al. (1996), and Pain et al. (1996) will discuss observation strategies and rates, analysis and calibration issues, the sources of measurement uncertainty, and the cosmological implications, including bounds on q{sub 0}, of these first high-redshift supernovae from our ongoing search.
Date: June 1, 1995
Creator: Perlmutter, S. & al., et
Object Type: Article
System: The UNT Digital Library
D0 Silicon Upgrade: Cryogenic Lines at Refrigerator : Thermal Contraction Analysis of Four Cryogenic Utility Lines for the D0 Upgrade (open access)

D0 Silicon Upgrade: Cryogenic Lines at Refrigerator : Thermal Contraction Analysis of Four Cryogenic Utility Lines for the D0 Upgrade

The cryogenic lines GHE and LN2 contain two lines each, one for supply and the other for return. The tubing was stress analyzed per ASME code for pressure piping, standard ANSI/ASME B31.3. A commercial pipe stress analysis and design system by ALGOR{reg_sign} was used for the analysis along with the calculated maximum stress, 25,050 psi. They were all analyzed for combined pressure, thermal movement, and dead weight and all the stresses were below this allowable stress limit. There are sections of the transfer lines that will be increased from a 1-1/2-inch vacuum jacket to a 2-inch vacuum jacket. This increase accounts for the maximum displacement, 0.466-inch in troubled areas as seen in subsequent drawings. The greatest displacement allowed for a 1-1/2-inch vacuum jacket is 0.421-inch for a 1/2-inch pipe on the nominal centerline. The greatest displacement allowed for a 2-inch vacuum jacket is 0.658-inch. We will have a clearance of 0.192-inch when using the 2-inch vacuum jacket.
Date: June 23, 1995
Creator: Kuwazaki, Andrew
Object Type: Report
System: The UNT Digital Library
D0 Silicon Upgrade: Thermal Contraction Analysis of the Solenoid and VLPC Cryogenic Transfer Lines for the D0 Upgrade (open access)

D0 Silicon Upgrade: Thermal Contraction Analysis of the Solenoid and VLPC Cryogenic Transfer Lines for the D0 Upgrade

The stresses developed in the solenoid and VLPC transfer lines have been investigated with the PipePlus v4.5 software package from Algor. 4 cases were considered for each transfer line and the following results were obtained. Pipe deflections have also been kept to a minimum by carefully considering the location of spider guides. Their placement should be as close as possible to the locations shown in Figures 4-7. With regard to chosen pipe sizes, the 2.5-inch OD Cu radiation shield in the solenoid transfer line should be replaced with a 3.5-inch OD tube. The vacuum jackets should also be replaced with 5-inch or larger pipe. These changes should safely accommodate the maximum displacements caused by thermal loading. This engineering note investigates the ability of the solenoid and VLPC cryogenic transfer lines to accommodate thermal stresses. The solenoid and VLPC transfer lines are similar in their construction in that they consist of an outer vacuum jacket, liquid nitrogen supply and return lines, a copper thermal radiation shield, and liquid helium supply and return lines. See Figure 1 for details on their specific construction. Line drawings for the solenoid and VLPC transfer lines are shown in Figures 2 and 3, respectively. The transfer …
Date: June 6, 1995
Creator: Leicht, Todd M.
Object Type: Report
System: The UNT Digital Library
Progress Report on the g-2 Storage Ring Magnet System (open access)

Progress Report on the g-2 Storage Ring Magnet System

The 3.1 GeV muon storage ring for the g-2 experiment at Brookhaven National Laboratory has three large solenoid magnets that form a continuous 1.451 tesla storage ring dipole with an average beam bend radius of 7.1 meters. In addition to the three storage ring solenoids, there is an inflector dipole with nested dipole coils that create very little stray magnetic field. A superconducting shield on the inflector gets rid of most of the remaining stray flux. This paper reports on the progress made on the storage ring solenoid magnet system and the inflector as of June 1995. The results of cryogenic system tests are briefly reported.
Date: June 1, 1995
Creator: Bunce, G.A.; Cullen, J.; Danby, G.; Green, M.A.; Jackson, J.; Jia, L. et al.
Object Type: Article
System: The UNT Digital Library
D0 Silicon Upgrade: Transfer Line Branch Considerations for Solenoid & VLPC (open access)

D0 Silicon Upgrade: Transfer Line Branch Considerations for Solenoid & VLPC

The transfer line for the solenoid currently has a dead branch on it. Issues regarding the solenoid transfer line also apply to the VLPC transfer line. Issues that need to be addressed are: (1) What is the heat load on the branch? (2) Would it be a good idea to run the LN2 radiation shield on the branch? (3) What are the thermal acoustic oscillation parameters of a dead headed branch? A simple remedy, although not analyzed was to install a jumper with a flow restriction at the end of the helium piping to allow a small flow to pass from supply to return. Thus eliminating a stagnant gas volume in which pressure pulses would develop. (4) Do we need to have a vapor trap to keep liquid from sloshing back and forth from the cold end to the warm end? (5) Comment: The tee that passes the 2-phase return into the nested LHe supply/return pipe should be pointed up so that the volume of transfer line acts sort of like a phase separator full of liquid. It is very difficult to predict the behavior of the dead ended branch. Therefore the conservative thing to do is to keep the …
Date: June 16, 1995
Creator: Rucinski, Russ
Object Type: Report
System: The UNT Digital Library
Power Tests of a String of Magnets Comprising a Full Cell of the Superconducting Super Collider (open access)

Power Tests of a String of Magnets Comprising a Full Cell of the Superconducting Super Collider

In this paper we describe the operation and testing of a string of magnets comprising a full cell of the Superconducting Super Collider (SSC). The full cell configuration composed of ten dipoles, two quadrupoles, and three spool pieces is the longest SSC magnet string ever tested. Although the tests of the full cell were undertaken after the SSC project was marked for termination, their completion was deemed necessary and useful to future efforts at other accelerator laboratories utilizing Superconducting magnets. The focus of this work is on the electrical and cryogenic performance of the string components and the quench protection system with an emphasis on solving some of the questions concerning electrical performance raised during the previous two experimental runs involving a half cell configuration.
Date: June 28, 1995
Creator: Burgett, W.; Cromer, L.; Haenni, D.; Hentges, M.; Jaffrey, T.; Kraushaar, P. et al.
Object Type: Article
System: The UNT Digital Library
Department of Energy Review of Laboratory Programs for Women Points-of-Contact Committee: Comparative Report, June 1995 (open access)

Department of Energy Review of Laboratory Programs for Women Points-of-Contact Committee: Comparative Report, June 1995

A survey of the DOE facilities was undertaken by the Points-of-Contact for the DOE Review of Laboratory Programs for Women in order to gather data to be used as a baseline against which to measure future progress. We plan to look at current programs already in place and evaluate them with a view to deciding which programs are most effective, and selecting model programs suitable for implementation at other facilities. The survey focused on four areas: 1) statistical data, 2) laboratory policy, 3) formal and informal programs which affect the quality of life in the work environment, and career development and advancement, and 4) educational programs. Although this report focuses on women, the problems discussed affect all DOE facility employees.
Date: June 1, 1995
Creator: McLane, V. & Layne, A.
Object Type: Report
System: The UNT Digital Library
An In-Situ Photometric and Energy Analysis of a Sulfur LampLighting System (open access)

An In-Situ Photometric and Energy Analysis of a Sulfur LampLighting System

This paper describes the results of a photometric and energy analysis that was conducted on a new light guide and sulfur lamp system recently installed at the U.S. Department of Energy's Forrestal Building. This novel system couples two high lumen output, high efficiency sulfur lamps to a single 73 m (240 ft.) hollow light guide lined with a reflective prismatic film. The system lights a large roadway and plaza area that lies beneath a section of the building. It has been designed to completely replace the grid of 280 mercury vapor lamps formerly used to light the space. This paper details the results of a field study that characterizes the significant energy savings and increased illumination levels that have been achieved. Comparisons to modeled HID lighting scenarios are also included.
Date: June 1, 1995
Creator: Crawford, Doug; Gould, Carl; Packer, Michael; Rubinstein,Francis & Siminovitch, Michael
Object Type: Article
System: The UNT Digital Library
Mammary gland tumor formation in transgenic mice overexpressing stromelysin-1 (open access)

Mammary gland tumor formation in transgenic mice overexpressing stromelysin-1

An intact basement membrane (BM) is essential for the proper function, differentiation and morphology of many epithelial cells. The disruption or loss of this BM occurs during normal development as well as in the disease state. To examine the importance of BM during mammary gland development in vivo, we generated transgenic mice that inappropriately express autoactivating isoforms of the matrix metalloproteinase stromelysin-1. The mammary glands from these mice are both functionally and morphologically altered throughout development. We have now documented a dramatic incidence of breast tumors in several independent lines of these mice. These data suggest that overexpression of stromelysin-1 and disruption of the BM may be a key step in the multi-step process of breast cancer.
Date: June 1, 1995
Creator: Sympson, Carolyn J; Bissell, Mina J & Werb, Zena
Object Type: Article
System: The UNT Digital Library
CO{sub 2} exchange, environmental productivity indices, and productivity of Agaves and Cacti under current and elevated atmospheric CO{sub 2} concentrations. Terminal report (open access)

CO{sub 2} exchange, environmental productivity indices, and productivity of Agaves and Cacti under current and elevated atmospheric CO{sub 2} concentrations. Terminal report

The research described in the proposal investigated net CO{sub 2} uptake and biomass accumulation for an extremely productive CAM plant, the prickly pear cactus Opuntia ficus-indica, under conditions of elevated CO{sub 2} concentrations for relatively long periods. The influences of soil water status, air temperature, and the photosynthetic photon flux (PPF) on net CO{sub 2} uptake over 24-h periods were evaluated to enable predictions to be made based on an Environmental Productivity Index (EPI). Specifically, EPI predicts the fraction of maximal daily net CO{sub 2} uptake based on prevailing environmental conditions. It is the product of indices for temperature, soil water, and intercepted PPF, each of which range from 0.00 when that index factor completely inhibits net CO{sub 2} uptake to 1.00 when no limitation occurs. For instance, the Water Index is 1.00 under wet conditions and decreases to 0.00 during prolonged drought. Although the major emphasis of the research was on net CO{sub 2} uptake and the resulting biomass production for O. ficus-indica, effects of elevated CO{sub 2} concentrations on root: shoot ratios and on the activities of the two carboxylating enzymes were also investigated. Moreover, experiments were also done on other CAM plants, including Agave deserti, Agave salmiana, …
Date: June 1, 1995
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Recycling zinc by dezincing steel scrap (open access)

Recycling zinc by dezincing steel scrap

In response to the worldwide increase in consumption of galvanized steel for automobiles in the last fifteen years, and the increased cost of environmental compliance associated with remelting larger quantities of galvanized steel scrap, a process is being developed to separate and recover the steel and zinc from galvanized ferrous scrap. The zinc is dissolved from the scrap in hot caustic using anodic assistance and is recovered electrolytically as dendritic powder. The designed ferrous scrap is rinsed and used directly. The process is effective for zinc, lead, and aluminum removal on loose and baled scrap and on all types of galvanized steel. The process has been pilot tested in Hamilton, Ontario for batch treatment of 900 tonnes of mostly baled scrap. A pilot plant in East Chicago, Indiana has designed in a continuous process mode 900 tonnes of loose stamping plant scrap; this scrap typically has residual zinc below 0.1% and sodium dragout below 0.001%. This paper reviews pilot plant performance and the economics of recycling galvanized steel and recovering zinc using a caustic process.
Date: June 1, 1995
Creator: Dudek, F. J.; Daniels, E. J. & Morgan, W. A.
Object Type: Article
System: The UNT Digital Library
An atlas of thermal data for biomass and other fuels (open access)

An atlas of thermal data for biomass and other fuels

Biomass is recognized as a major source of renewable energy. In order to convert biomass energy to more useful forms, it is necessary to have accurate scientific data on the thermal properties of biomass. This Atlas has been written to supply a uniform source of that information. In the last few decades Thermal analysis (TA) tools such as thermogravimetry, differential thermal analysis, thermo mechanical analysis, etc. have become more important. The data obtained from these techniques can provide useful information in terms of reaction mechanism, kinetic parameters, thermal stability, phase transformation, heat of reaction, etc. for gas-solid and gas-liquid systems. Unfortunately, there are no ASTM standards set for the collection of these types of data using TA techniques and therefore, different investigators use different conditions which suit their requirements for measuring this thermal data. As a result, the information obtained from different laboratories is not comparable. This Atlas provides the ability to compare new laboratory results with a wide variety of related data available in the literature and helps ensure consistency in using these data.
Date: June 1, 1995
Creator: Gaur, S. & Reed, T. B.
Object Type: Report
System: The UNT Digital Library
Production and mitigation of acid chlorides in geothermal steam (open access)

Production and mitigation of acid chlorides in geothermal steam

Measurements of the equilibrium distribution of relatively nonvolatile solutes between aqueous liquid and vapor phases have been made at temperatures to 350{degrees}C for HCl(aq) and chloride salts. These data are directly applicable to problems of corrosive-steam production in geothermal steam systems. Compositions of high-temperature brines which could produce steam having given concentrations of chlorides may be estimated at various boiling temperatures. Effects of mitigation methods (e.g., desuperheating) can be calculated based on liquid-vapor equilibrium constants and solute mass balances under vapor-saturation conditions.
Date: June 1, 1995
Creator: Simonson, J. M. & Palmer, D. A.
Object Type: Article
System: The UNT Digital Library
Interaction of fast waves with ions (open access)

Interaction of fast waves with ions

To fully utilize the available power sources in DIII-D (FW, NBI, ECH), understanding of the synergism between the heating mechanisms is important. In this paper the ion distribution, under simultaneous application of NBI and FW, is calculated from Fokker-Planck code CQL3D coupled to ray-tracing code CURRAY. It is found that interaction between energetic ions and FW can be minimized or maximized by adjusting various parameters such as magnetic field, density, beam energy, and FW frequency. Specifically, in DIII-D, the authors find negligible interactions above 1.8 T and above 80 MHz, while the interaction increases at lower fields and frequencies. The results are compared with experiments in DIII-D including the calculated neutron rate. Energetic ion orbit losses may play an important role in the ion distribution, and this effect is being investigated.
Date: June 1, 1995
Creator: Chiu, S. C.; deGrassie, J. S. & Harvey, R. W.
Object Type: Article
System: The UNT Digital Library
Applying automated data acquisition and management technology to bioremediation (open access)

Applying automated data acquisition and management technology to bioremediation

Operating a bioremediation process requires timely and accurate analysis of physical and chemical parameters that can affect the system. At a fuel oil spill site, the operation of an in-situ bioremediation system, consisting of fluid and nutrient injection, fluid withdrawal, and aeration cycles, is monitored by means of electronic downhole sensors and on-site chemical analysis. A data acquisition and management system was designed and implemented to rapidly analyze data for operational decision malting. A hardware suite, containing an electronic monitoring system data acquisition computer, and data analysis workstation, was also developed. Through the use of both commercial software products and custom software, suites of data management and analysis tools were provided. The data acquisition suite of software tools assisted in programming dataloggers, automatically recording monitored data, and integrating these data with manually sampled chemical data. The data analysis suite of software tools assisted in downloading data to remote workstations, sampling the database for trend analysis, and automating the interface to commercial analysis packages.
Date: June 1, 1995
Creator: Widing, M.A. & Leser, C.
Object Type: Article
System: The UNT Digital Library
Controlling cycle-by-cycle variation in a pulse combustor (open access)

Controlling cycle-by-cycle variation in a pulse combustor

We describe a method for controlling chaos-generated cyclic variations in a pulse combustor. The method is applied to a recently developed thermal pulse combustor model and utilizes a map-based, adaptive proportional feedback algorithm. With this technique we show that it is possible to greatly reduce cycle-by-cycle pulse variation. We further show that minimizing cyclic variation allows combustor operation at conditions well beyond the normal flameout limit.
Date: June 1, 1995
Creator: Daw, C. S.; Thomas, J. F.; Rhode, M. A.; Rollins, R. W. & Markworth, A. J.
Object Type: Article
System: The UNT Digital Library
Ligands for SPECT and PET imaging of muscarinic-cholinergic receptors of the heart and brain (open access)

Ligands for SPECT and PET imaging of muscarinic-cholinergic receptors of the heart and brain

Interest in the potential use of cerebral SPECT and PET imaging for determination of the density and activity of muscarinic-cholinergic receptors (mAChR) has been stimulated by the changes in these receptors which occur in many neurological diseases. In addition, the important involvement of mAChR in modulating negative inotropic cardiac activity suggests that such receptor ligands may have important applications in evaluation of changes which may occur in cardiac disease. In this paper, the properties of several key muscarinic receptor ligands being developed or which have been used for clinical SPECT and PET are discussed. In addition, the ORNL development of the new iodinated IQNP ligand based on QNB and the results of in vivo biodistribution studies in rats, in vitro competitive binding studies and ex vivo autoradiographic experiments are described. The use of radioiodinated IQNP may offer several advantages in comparison to IQNB because of its easy and high yield preparation and high brain uptake and the potential usefulness of the {open_quotes}partial{close_quotes} subtype selective IONP isomers. We also describe the development of new IQNP-type analogues which offer the opportunity for radiolabeling with positron-emitting radioisotopes (carbon-11, fluorine-18 and bromine-76) for potential use with PET.
Date: June 1, 1995
Creator: Knapp, F. F. Jr.; McPherson, D. W. & Luo, H.
Object Type: Article
System: The UNT Digital Library
Creep in Topopah Spring Member welded tuff. Yucca Mountain Site Characterization Project (open access)

Creep in Topopah Spring Member welded tuff. Yucca Mountain Site Characterization Project

A laboratory investigation has been carried out to determine the effects of elevated temperature and stress on the creep deformation of welded tuffs recovered from Busted Butte in the vicinity of Yucca Mountain, Nevada. Water saturated specimens of tuff from thermal/mechanical unit TSw2 were tested in creep at a confining pressure of 5.0 MPa, a pore pressure of 4.5 MPa, and temperatures of 25 and 250 C. At each stress level the load was held constant for a minimum of 2.5 {times} 10{sup 5} seconds and for as long as 1.8 {times} 10{sup 6} seconds. One specimen was tested at a single stress of 80 MPa and a temperature of 250 C. The sample failed after a short time. Subsequent experiments were initiated with an initial differential stress of 50 or 60 MPa; the stress was then increased in 10 MPa increments until failure. The data showed that creep deformation occurred in the form of time-dependent axial and radial strains, particularly beyond 90% of the unconfined, quasi-static fracture strength. There was little dilatancy associated with the deformation of the welded tuff at stresses below 90% of the fracture strength. Insufficient data have been collected in this preliminary study to determine …
Date: June 1, 1995
Creator: Martin, R. J., III; Boyd, P. J.; Noel, J. S. & Price, R. H.
Object Type: Report
System: The UNT Digital Library
Human Reliability Analysis for In-Tank Precipitation Alignment and Startup of Emergency Purge Ventilation Equipment. Revision 4 (open access)

Human Reliability Analysis for In-Tank Precipitation Alignment and Startup of Emergency Purge Ventilation Equipment. Revision 4

This report documents the methodology used for calculating the human error probability for establishing air based ventilation using emergency purge ventilation equipment on In-Tank Precipitation (ITP) processing tanks 48 and 49 after a failure of the nitrogen purge system following a seismic event. The analyses were performed according to THERP (Technique for Human Error Rate Prediction) as describes in NUREG/CR-1278-F.
Date: June 1, 1995
Creator: Shapiro, B. J. & Britt, T. E.
Object Type: Report
System: The UNT Digital Library
Ceramic composites with a ductile Ni{sub 3}Al binder phase (open access)

Ceramic composites with a ductile Ni{sub 3}Al binder phase

Composites using B-doped ductile Ni{sub 3}Al alloys were produced with both non-oxide (WC, TiC) and oxide (Al{sub 2}0{sub 3}) ceramic powders. Typical powder processing techniques were used to fabricate materials with ceramic contents from 0-95 vol. %. The microstructural morphology of the composites depends primarily on the wetting behavior between the alloys and the ceramic powders. The non-oxide ceramic powders wet well and the Ni{sub 3}Al alloys form a semi-continuous intergranular phase. On the other hand, the Ni{sub 3}Al alloys do not wet the oxide powders well and tend to form discrete ``islands`` of the metallic phase. Wetting in these materials can be improved by the addition of non-oxide particles, such as TiC. Results on the mechanical properties showed ambient temperature flexural strength similar to other Ni-based hardmetals. In contrast to the WC-Co materials, the flexural strength is retained to temperatures of at least 800 C. The fracture toughness and hardness were found to be equal or higher than comparable Co-based hardmetal systems. Initial corrosion tests showed excellent resistance to acid solutions.
Date: June 1, 1995
Creator: Tiegs, T. N.; Alexander, K. B.; Plucknett, K. P.; Menchhofer, P. A.; Becher, P. F. & Waters, S. B.
Object Type: Article
System: The UNT Digital Library
Report of ground water monitoring for expansion of the golf course, Salt Lake City, Utah, vitro processing site (open access)

Report of ground water monitoring for expansion of the golf course, Salt Lake City, Utah, vitro processing site

To determine the potential impacts of the proposed golf course expansion on the south side of the Vitro site, ground water data from the UMTRA Vitro processing site were evaluated in response to the U.S. Department of Energy (DOE) Uranium Mill Tailings Remedial Action (UMTRA) Project Office request. Golf in the Round, Inc., has proposed an expansion of the present driving range to include a 9-hole golf course on the UMTRA Vitro processing site, which is owned by the Central Valley Water Reclamation Facility (CVWRF). An expanded golf course would increase irrigation and increase the amount of water that could infiltrate the soil, recharging the unconfined aquifer. Increased water levels in the aquifer could alter the ground water flow regime; contaminants in the shallow ground water could then migrate off the site or discharge to surface water in the area. Dewatering of the unconfined aquifer on CVWRF property could also impact site contaminant migration; a significant amount of ground water extraction at CVWRF could reduce the amount of contaminant migration off the site. Since 1978, data have been collected at the site to determine the distribution of tailings materials (removed from the site from 1985 to 1987) and to characterize …
Date: June 1, 1995
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Status of the synchrotron radiation monitors for the APS facility rings (open access)

Status of the synchrotron radiation monitors for the APS facility rings

Initial results from the Optical synchrotron radiation (OSR) monitors for the Advanced Photon Source (APS) have been obtained. Data using electron beams on the positron accumulator ring (PAR) at 400 MeV, the injector synchrotron (IS) up to 7-GeV, and the main storage ring (SR) at 4.5 and 7 GeV address both transverse profiles and/or longitudinal bunch length. Recent measurements on OSR transported outside of the PAR and IS enclosures include transverse damping information. Streak camera and photodiode detectors have been used to measure bunch length compression {sigma}{sub t} = 1000 to 400 ps on the PAR and damping on the IS of {sigma}{sub t} = 200 to 75 ps. First transverse images have been recorded on the main ring from a single turn and for stored beam.
Date: June 1, 1995
Creator: Lumpkin, A. & Yang, B.
Object Type: Article
System: The UNT Digital Library
Plutonium Consumption Program, CANDU Reactor Project: Feasibility of BNFP Site as MOX Fuel Supply Facility. Final report (open access)

Plutonium Consumption Program, CANDU Reactor Project: Feasibility of BNFP Site as MOX Fuel Supply Facility. Final report

An evaluation was made of the technical feasibility, cost, and schedule for converting the existing unused Barnwell Nuclear Fuel Facility (BNFP) into a Mixed Oxide (MOX) CANDU fuel fabrication plant for disposition of excess weapons plutonium. This MOX fuel would be transported to Ontario where it would generate electricity in the Bruce CANDU reactors. Because CANDU MOX fuel operates at lower thermal load than natural uranium fuel, the MOX program can be licensed by AECB within 4.5 years, and actual Pu disposition in the Bruce reactors can begin in 2001. Ontario Hydro will have to be involved in the entire program. Cost is compared between BNFP and FMEF at Hanford for converting to a CANDU MOX facility.
Date: June 30, 1995
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Application of damage models in metal forming (open access)

Application of damage models in metal forming

The development of damage models in the analysis of metal forming processes, to characterize the formability limits, is an important area of ongoing research. In this paper, two energy-based damage models for the simulation of crack initiation in metal forming processes are presented. The first one is an isotropic damage model with two damage variables. The second one is an anisotropic model with a damage characteristic tensor. The damage models are developed within the general framework of continuum thermodynamics for irreversible processes by identifying a proper set of internal variables together with their associated generalized forces. An approach is proposed to account for microcrack opening and closing. A viscoplastic regularization algorithm is used to take into account the strain rate effect and to improve numerical stability. Both models have been incorporated into the finite element code, LAGAMINE. The models were applied to simulations of upsetting of collar cylinders and nonisothermal hemispherical punch stretching. The results of the analyses were validated by comparing the finite element simulations with experimentally obtained data.
Date: June 1, 1995
Creator: Zhu, Y. Y. & Zacharia, T.
Object Type: Article
System: The UNT Digital Library