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Sample records for sheet metal workers

  1. Sheet Metal Worker: A Training Profile.

    ERIC Educational Resources Information Center

    Ontario Ministry of Skills Development, Toronto.

    This training profile is intended for use by program developers and trainers in the development of training courses and programs for sheet metal workers. It contains 17 modules: safety for sheet metal worker; tools and machinery; materials and gauges; drafting and shop drawing; pattern development; methods of joining sheet metal; shearing and…

  2. 75 FR 15741 - Sheet Metal Workers Internationl Association, Local 292: Troy, MI; Notice of Termination of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-30

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Employment and Training Administration Sheet Metal Workers Internationl Association, Local 292: Troy, MI... investigation was initiated in response to a petition filed on July 13, 2009 on behalf of workers of Steel...

  3. Mississippi Curriculum Framework for Sheet Metal Programs (Program CIP: 48.0506--Sheet Metal Worker). Postsecondary Programs.

    ERIC Educational Resources Information Center

    Mississippi Research and Curriculum Unit for Vocational and Technical Education, State College.

    This document provides the framework for a postsecondary sheet metal program of instruction. A foreword provides guidelines that were used in developing the program and should be considered in compiling and revising course syllabi and daily lesson plans at the local level. A description of the sheet metal programs (building trades sheet metal work…

  4. Occupational exposure to dust and lung disease among sheet metal workers.

    PubMed Central

    Hunting, K L; Welch, L S

    1993-01-01

    A previous large medical survey of active and retired sheet metal workers with 20 or more years in the trade indicated an unexpectedly high prevalence of obstructive pulmonary disease among both smokers and non-smokers. This study utilised interviews with a cross section of the previously surveyed group to explore occupational risk factors for lung disease. Four hundred and seven workers were selected from the previously surveyed group on the basis of their potential for exposure to fibreglass and asbestos. Selection was independent of health state, and excluded welders. A detailed history of occupational exposure was obtained by telephone interview for 333 of these workers. Exposure data were analysed in relation to previously collected data on chronic bronchitis, obstructive lung disease, and personal characteristics. Assessment of the effects of exposure to fibreglass as distinct from the effects of exposure to asbestos has been difficult in previous studies of construction workers. The experienced workers studied here have performed a diversity of jobs involving exposure to many different types of materials, and this enabled exposure to each dust to be evaluated separately. The risk of chronic bronchitis increased sharply by pack-years of cigarettes smoked; current smokers had a double risk compared with those who had never smoked or had stopped smoking. The occurrence of chronic bronchitis also increased with increasing duration of exposure to asbestos. Workers with a history of high intensity exposure to fibreglass had a more than doubled risk of chronic bronchitis. Obstructive lung disease, defined by results of pulmonary function tests at the medical survey, was also related to both smoking and occupational risk factors. Number of pack years smoked was the strongest predictor of obstructive lung disease. Duration of direct and indirect exposure to welding fume was also a positive predictor of obstructive lung disease. Duration of exposure to asbestos was

  5. Perforating Thin Metal Sheets

    NASA Technical Reports Server (NTRS)

    Davidson, M. E.

    1985-01-01

    Sheets only few mils thick bonded together, punched, then debonded. Three-step process yields perforated sheets of metal. (1): Individual sheets bonded together to form laminate. (2): laminate perforated in desired geometric pattern. (3): After baking, laminate separates into individual sheets. Developed for fabricating conductive layer on blankets that collect and remove ions; however, perforated foils have other applications - as conductive surfaces on insulating materials; stiffeners and conductors in plastic laminates; reflectors in antenna dishes; supports for thermal blankets; lightweight grille cover materials; and material for mockup of components.

  6. Radiological abnormalities among sheet-metal workers in the construction industry in the United States and Canada: Relationship to asbestos exposure

    SciTech Connect

    Selikoff, I.J.; Lilis, R. )

    1991-01-01

    We investigated the possible adverse health effects to sheet-metal workers who had past exposure to asbestos. A cross-sectional medical examination of 1,330 workers was conducted during 1986 and 1987 in seven cities in the United States and Canada. A total of 1,016 workers had been employed for at least 35 y in the industry, and the mean duration from onset of asbestos exposure was 39.5 y (SD = 7.41 y). Chest x-ray abnormalities were found in more than half of the group. Pleural fibrosis, the most frequently found abnormality, was present in 47.0% of the cases and was the only abnormality found in 27.8% of cases; parenchymal interstitial fibrosis, found in 33.1% of cases, was the only abnormality found in 16.2% of cases. Radiologic abnormalities increased as duration of exposure increased. A positive smoking history was associated with a higher prevalence of radiologically detectable parenchymal abnormalities, a finding confirmed by us and others. Dyspnea on exertion was graded by a Medical Research Council questionnaire, the examinee's self-assessment, and a more detailed 12-point scale questionnaire. Few persons had marked shortness of breath, and approximately one-third had slight dyspnea. Individuals who had radiologic abnormalities experienced more shortness of breath than did those who had no radiologic abnormalities. Cigarette smoking also resulted in a higher prevalence of dyspnea. The results indicate that during the past, construction sheet-metal workers have been significantly exposed to asbestos on the job. Every effort should be made to minimize the anticipated serious health consequences, and further asbestos exposure for those who continue in this trade should be avoided.

  7. Twisting of sheet metals

    NASA Astrophysics Data System (ADS)

    Pham, C. H.; Thuillier, S.; Manach, P. Y.

    2013-12-01

    Twisting of metallic sheets is one particular mode of springback that occurs after drawing of elongated parts, i.e. with one dimension much larger than the two others. In this study, a dedicated device for drawing of elongated part with a U-shaped section has been designed on purpose, in order to obtain reproducible data. Very thin metallic sheet, of thickness 0.15 mm, has been used, so that the maximum length of the part is 100 mm. Two different orientations of the part with respect to the tools have been chosen: either aligned with the tools, or purposefully misaligned by 2°. Several samples were drawn for each configuration, leading to the conclusion that almost no twisting occurs in the first case whereas a significant one can be measured for the second one. In a second step, 2D and 3D numerical simulations within the implicit framework for drawing and springback were carried out. A mixed hardening law associated to von Mises yield criterion represents accurately the mechanical behavior of the material. This paper highlights a comparison of numerical predictions with experiments, e.g. the final shape of the part and the twisting parameter.

  8. Sheet Metal Contract. Project Report Phase I with Research Findings.

    ERIC Educational Resources Information Center

    Kirkpatrick, Thomas; Sappe', Hoyt

    This report provides results of Phase I of a project that researched the occupational area of sheet metal, established appropriate committees, and conducted task verification. These results are intended to guide development of a program designed to train sheet metal workers. Section 1 contains general information: purpose of Phase I; description…

  9. Horizontal electromagnetic casting of thin metal sheets

    DOEpatents

    Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1987-01-01

    Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

  10. Horizontal electromagnetic casting of thin metal sheets

    DOEpatents

    Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1988-01-01

    Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

  11. Metals fact sheet: Ruthenium

    SciTech Connect

    1996-06-01

    Ruthenium, named after Ruthenia, a province in Western Russia, was discovered in 1827 by Osann in placer ores from Russia`s Ural mountains. A minor platinum group metal (PGM), Ruthenium was the last of the PGMs to be isolated. In 1844, Klaus prepared the first 6 grams of pure ruthenium metal.

  12. Metals Fact Sheet: Yttrium

    SciTech Connect

    1992-09-01

    Yttrium is a metallic element usually included among the rare earth metals, which it resembles chemically and with which it usually occurs in minerals. Yttrium was named after the village of Ytterby in Sweden---the element was discovered in a quarry near the village. This article discusses sources of the element, the world market for the element, and various applications of the material.

  13. Metals fact sheet - lanthanum

    SciTech Connect

    1995-04-01

    Mosander was the first to extract the elusive rare earth, lanthanum, from unrefined cerium nitrate in 1839. The name was derived from the Greek word lanthanein, meaning {open_quotes}to escape notice.{close_quotes} Lanthanum is the lightest rare earth and a very malleable metal-soft enough to be cut with a knife. Used primarily as an additive in steels and non-ferrous metals, lanthanum is the lightest rare earth element and one of four rare earths from which mischmetal is made. Additional applications include advanced batteries, optical fibers, and phosphors.

  14. Metals fact sheet - indium

    SciTech Connect

    1994-01-01

    Indium is generally found in concentrations averaging 10 to 20 ppm in sphalerite and chalcopyrite ores associated with zinc, copper, lead and tin deposits. Indium is recovered as a by-product of base metal mining by open pit, underground and other methods. After the recovery of zinc by the electrolytic process (copper concentrate by flotation, and lead and tin by electrolysis), indium antimonide slimes left on the anode and the indium-containing spent electrolyte become the input material for the processing of indium. Sulfuric acid is combined with the residues and heated to form sulfates which are then leached with water to filter off the remaining tin, lead and antimony. The indium in solution is recovered by cementation on aluminum, washed, melted, and refined into a metal.

  15. Metals fact sheet - uranium

    SciTech Connect

    1996-04-01

    About 147 million pounds of this radioactive element are consumed annually by the worldwide nuclear power and weapons industries, as well as in the manufacture of ceramics and metal products. The heaviest naturally occurring element, uranium is typically found in intrusive granites, igneous and metamorphic veins, tabular sedimentary deposits, and unconformity-related structures. This article discusses the geology, exploitation, market, and applications of uranium and uranium ores.

  16. Aircraft Sheet Metal Practices, Blueprint Reading, Sheet Metal Forming and Heat Treating; Sheet Metal Work 2: 9855.04.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This course is designed to familiarize vocational students with construction in sheet metal layout. The document outlines goals, specific block objectives, layout practices, blueprint reading, sheet metal forming (by hand and by machine), and heat treatment of metals, and includes posttest samples. Layout techniques and air foil developing are…

  17. Reinforcement for Stretch Formed Sheet Metal

    NASA Technical Reports Server (NTRS)

    Lea, J. B.; Baxter, C. R.

    1983-01-01

    Tearing of aluminum sheet metal durinng stretch forming prevented by flame spraying layer of aluminum on edges held in stretch-forming machine. Technique improves grip of machine on metal and reinforced sheet better able to with stand concentration of force in vicinity of grips.

  18. Synthesis of Metal Phthalocyanine Sheet Polymers

    NASA Technical Reports Server (NTRS)

    Achar, B. N.; Fohlen, G. M.; Parker, J. A.

    1986-01-01

    New method for synthesizing metal phthalocyanine tetracarboxylic acids (MPTCA's) yields high purity end product. In addition, high-purity metal phthalocyanine sheet polymers synthesized from compounds. Monomer formed into sheet polymer by heating. Units of polymer linked in manner similar to phenyl-group linkages in biphenyl: Conjugation extends throughout macromolecule, thereby increasing delocalization of TT-electrons. Increases conductivity and thermal stability of polymer.

  19. Interior view of the Sheet Metal Shop showing the roof ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Interior view of the Sheet Metal Shop showing the roof trusses and corrugated metal roof covering, view facing northwest - Kahului Cannery, Plant No. 28, Boiler House, Sheet Metal and Electrical Shops, 120 Kane Street, Kahului, Maui County, HI

  20. Metals Fact Sheet: Gadolinium GD

    SciTech Connect

    1992-10-01

    Gadolinium is a silvery-white, malleable, ductile metallic element used to improve the high-temperature characteristics of iron, chromium, and related metallic alloys. It was named after the French chemist, Gadolin, discoverer of yttrium. This article discusses sources of the element, the world supply and demand, and also a number of applications. With the largest thermal neutron absorption cross section of any element, one of these applications is as a burnable poison in reactors and as neutron absorbers in other nuclear devices.

  1. Structures of Thin Sheet Metal, Their Design and Construction

    NASA Technical Reports Server (NTRS)

    Wagner, Herbert

    1928-01-01

    This report presents a brief survey of the uses of sheet-metal coverings in conjunction with the inner structure. A method of construction is presented as well as a discussion on the strength of sheet metal.

  2. Metals fact sheet--cesium

    SciTech Connect

    1997-03-01

    Cesium, the most alkaline and electropositive metal, is used by several industries for a variety of applications, including chemical catalysis, biomedical, photoelectrical, and glass manufacturing. While the traditional market for cesium has remained small, potential growth areas exist in the chemical catalysis and the oil and gas industry.

  3. Electromagnetic augmentation for casting of thin metal sheets

    DOEpatents

    Hull, J.R.

    1987-10-28

    Thin metal sheets are cast by magnetically levitating molten metal deposited in a model within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled by the water-cooled walls of the mold to form a solid metal sheet. A conducting shield is electrically coupled to the molten metal sheet to provide a return path for eddy currents induced in the metal sheet by the current in the AC conducting coils. In another embodiment, a DC conducting coil is coupled to the metal sheet for providing a direct current therein which interacts with the magnetic field to levitate the moving metal sheet. Levitation of the metal sheet in both molten and solid forms reduces its contact pressure with the mold walls while maintaining sufficient engagement therebetween to permit efficient conductive cooling by the mold through which a coolant fluid may be circulated. 8 figs.

  4. Introduction to Sheet Metal. Instructor Edition. Introduction to Construction Series.

    ERIC Educational Resources Information Center

    Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    This instructor's guide contains the materials required to teach a competency-based introductory course in sheet metal work to students who have chosen to explore careers in construction. The following topics are covered in the course's three instructional units: sheet metal materials, sheet metal tools, and applied skills. Each unit contains some…

  5. Electromagnetic augmentation for casting of thin metal sheets

    DOEpatents

    Hull, John R.

    1989-01-01

    Thin metal sheets are cast by magnetically levitating molten metal deposited in a mold within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled by the water-cooled walls of the mold to form a solid metal sheet. A conducting shield is electrically coupled to the molten metal sheet to provide a return path for eddy currents induced in the metal sheet by the current in the AC conducting coils. In another embodiment, a DC conducting coil is coupled to the metal sheet for providing a direct current therein which interacts with the magnetic field to levitate the moving metal sheet. Levitation of the metal sheet in both molten and solid forms reduces its contact pressure with the mold walls while maintaining sufficient engagement therebetween to permit efficient conductive cooling by the mold through which a coolant fluid may be circulated. The magnetic fields associated with the currents in the aforementioned coils levitate the molten metal sheet while the mold provides for its lateral and vertical confinement. A leader sheet having electromagnetic characteristics similar to those of the molten metal sheet is used to start the casing process and precedes the molten metal sheet through the yoke/coil arrangement and mold and forms a continuous sheet therewith. The yoke/coil arrangement may be either U-shaped with a single racetrack coil or may be rectangular with a pair of spaced, facing bedstead coils.

  6. Career Preparation Program Curriculum Guide for: Metal Fabrication, Sheet Metal.

    ERIC Educational Resources Information Center

    British Columbia Dept. of Education, Victoria. Curriculum Development Branch.

    This curriculum outline provides secondary and postsecondary instructors with detailed information on student learning outcomes for completion of the sheet metal fabrication program requirements. A program overview discusses the aims of education; secondary school philosophy; and career preparation programs and their goals, organization, and…

  7. Modeling of anisotropic hardening of sheet metals

    NASA Astrophysics Data System (ADS)

    Yoshida, Fusahito; Hamasaki, Hiroshi; Uemori, Takeshi

    2013-12-01

    To describe the evolution of anisotropy of sheet metals, in terms of both r-values and stresses, the present paper proposes anisotropic hardening models, where the shape of yield surface changes with increasing plastic strain. In this framework of modeling, any types of yield functions are able to be used. The evolution of anisotropy is expressed by updating the yield function as an interpolation between two yield functions defined at two different effective plastic strains. In this paper, two types of interpolation models, i.e., nonlinear interpolation model and piecewise interpolation model are presented. These models are validated by comparing the experimental data on 3003-O aluminum sheet (after Hu, Int J Plasticity 23, 620-639, 2007). To describe the Bauschinger effect, the combined anisotropic-kinematic hardening model is formulated based on Yoshida-Uemori kinematic hardening model.

  8. Damage Prediction in Sheet Metal Forming

    NASA Astrophysics Data System (ADS)

    Saanouni, Khémais; Badreddine, Houssem

    2007-05-01

    Ductile (or plastic) damage often occurs during sheet metal forming processes due to the large plastic flow localization. Accordingly, it is crucial for numerical tools, used in the simulation of that processes, to use fully coupled constitutive equations accounting for both hardening and damage. This can be used in both cases, namely to overcome the damage initiation during some sheet metal forming processes as deep drawing, … or to enhance the damage initiation and growth as in sheet metal cutting. In this paper, a fully coupled constitutive equations accounting for combined isotropic and kinematic hardening as well as the ductile damage is implemented into the general purpose Finite Element code for metal forming simulation. First, the fully coupled anisotropic constitutive equations in the framework of Continuum Damage Mechanics are presented. Attention is paid to the strong coupling between the main mechanical fields as elasto-viscoplasticity, mixed hardening, ductile isotropic damage and contact with friction. The anisotropy of the plastic flow is taken into account using various kinds of quadratic or non quadratic yield criteria in the framework of non associative finite plasticity theory with two types of normality rules. The associated numerical aspects concerning both the local integration of the coupled constitutive equations as well as the (global) equilibrium integration schemes are presented. The local integration is outlined thanks to the Newton iterative scheme applied to a reduced system of 2 equations. For the global resolution of the initial and boundary value problem, the classical dynamic explicit (DE) scheme with an adaptive time step control is used. The numerical implementation of the damage is made in such a manner that calculations can be executed with or without damage effect, i.e. fully coupled or uncoupled calculations. For the 2D processes an advanced adaptive meshing procedure is used in order to enhance the numerical solution and

  9. 46. NORTH THROUGH SHEET METAL AND ASSEMBLY AREA IN SOUTHWESTERN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    46. NORTH THROUGH SHEET METAL AND ASSEMBLY AREA IN SOUTHWESTERN QUADRANT OF FACTORY AS SEEN FROM DOORWAY IN SOUTH FRONT WALL. ALONG WEST INTERIOR WALL ARE SHELVES BEARING WATER PUMPS, PARTS FOR PUMPS AND WATER SUPPLY EQUIPMENT, AND NEW OLD STOCK MERCHANDISE. IN FRONT OF THE WALL ARE THE CIRCA 1900 SHEET METAL SHEAR AND CIRCA 1900 SHEET METAL BRAKE. AT THE RIGHT SIDE OF THE IMAGE ALONGSIDE VERTICAL CEILING SUPPORTS IS METAL-COVERED BENCH FOR SHEET METAL WORK. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  10. Sheet metal hydroforming of functional composite structures

    NASA Astrophysics Data System (ADS)

    Ibis, M.; Griesheimer, S.; Salun, L.; Rausch, J.; Groche, P.

    2011-03-01

    This paper studies the formability of functional composite structures, consisting of a metal substrate, insulating plastic foils, flat copper conductors and printable conductive polymers. The aim is the production of smart components in a sheet metal hydroforming process. In addition to their mechanical properties, these components can also transfer energy and data. Conventional boundaries between mechanics and electronics will be relaxed expediently. The challenge of this study is the design of the forming process, so that all elements of the multi-layer composites will withstand the process conditions. In this context, an analytical method for estimating the formability of these smart components is presented. The main objectives are the definition of basic failure modes and the depiction of the process limits.

  11. Theoretical analysis of sheet metal formability

    NASA Astrophysics Data System (ADS)

    Zhu, Xinhai

    Sheet metal forming processes are among the most important metal-working operations. These processes account for a sizable proportion of manufactured goods made in industrialized countries each year. Furthermore, to reduce the cost and increase the performance of manufactured products, in addition to the environmental concern, more and more light weight and high strength materials have been used as a substitute to the conventional steel. These materials usually have limited formability, thus, a thorough understanding of the deformation processes and the factors limiting the forming of sound parts is important, not only from a scientific or engineering viewpoint, but also from an economic point of view. An extensive review of previous studies pertaining to theoretical analyses of Forming Limit Diagrams (FLDs) is contained in Chapter I. A numerical model to analyze the neck evolution process is outlined in Chapter II. With the use of strain gradient theory, the effect of initial defect profile on the necking process is analyzed. In the third chapter, the method proposed by Storen and Rice is adopted to analyze the initiation of localized neck and predict the corresponding FLDs. In view of the fact that the width of the localized neck is narrow, the deformation inside the neck region is constrained by the material in the neighboring homogeneous region. The relative rotation effect may then be assumed to be small and is thus neglected. In Chapter IV, Hill's 1948 yield criterion and strain gradient theory are employed to obtain FLDs, for planar anisotropic sheet materials by using bifurcation analysis. The effects of the strain gradient coefficient c and the material anisotropic parameters R's on the orientation of the neck and FLDs are analyzed in a systematic manner and compared with experiments. In Chapter V, Hill's 79 non-quadratic yield criterion with a deformation theory of plasticity is used along with bifurcation analyses to derive a general analytical

  12. Clinical findings among hard metal workers.

    PubMed Central

    Fischbein, A; Luo, J C; Solomon, S J; Horowitz, S; Hailoo, W; Miller, A

    1992-01-01

    In 1940, the first report appeared describing a pulmonary disorder associated with occupational exposures in the cemented tungsten carbide industry. The disease, known as "hard metal disease," has subsequently been characterised in detail and comprises a wide range of clinical signs and symptoms. In this report, clinical findings in a group of 41 hard metal workers employed until recently are described. A high prevalence of respiratory symptoms was found. Thirteen workers (31%) had abnormal chest radiographs indicative of interstitial lung disease. Fifty per cent of these had been employed in hard metal manufacturing for less than 10 years. Abnormalities of pulmonary function were also frequent and included a restrictive pattern of impairment and decrease in diffusing capacity (27%). Associations were found between diffusing capacity, chest radiographic abnormalities and right ventricular ejection fraction at exercise indicating cardiopulmonary effects. The findings show the continuous need to control excessive occupational exposures to prevent hard metal disease, the history of which now enters its sixth decade. PMID:1733452

  13. Thin, porous metal sheets and methods for making the same

    SciTech Connect

    Liu, Wei; Li, Xiaohong Shari; Canfield, Nathan L.

    2015-07-14

    Thin, porous metal sheets and methods for forming them are presented to enable a variety of applications and devices. The thin, porous metal sheets are less than or equal to approximately 200 .mu.m thick, have a porosity between 25% and 75% by volume, and have pores with an average diameter less than or equal to approximately 2 .mu.m. The thin, porous metal sheets can be fabricated by preparing a slurry having between 10 and 50 wt % solvent and between 20 and 80 wt % powder of a metal precursor. The average particle size in the metal precursor powder should be between 100 nm and 5 .mu.m.

  14. Precision Sheet Metal. Progress Record and Theory Outline.

    ERIC Educational Resources Information Center

    Connecticut State Dept. of Education, Hartford. Div. of Vocational-Technical Schools.

    This combination progress record and course outline is designed for use by individuals teaching a course in precision sheet metal. Included among the topics addressed in the course are the following: employment opportunities in metalworking, measurement and layout, orthographic projection, precision sheet metal drafting, simple layout, hand tools,…

  15. Electrical upsetting of metal sheet forms weld edge

    NASA Technical Reports Server (NTRS)

    Scherba, E. S.

    1966-01-01

    Electric gathering of sheet stock edges forms metal sheets in the shape of gore sections with heavier edge areas that can be welded without loss of strength. The edges are gathered by progressive resistance heating and upsetting, and are formed automatically. This process avoids disturbance of the metals internal structure.

  16. 43. WEST TO DETAIL OF WHEELED SHEET METAL WORK STATION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    43. WEST TO DETAIL OF WHEELED SHEET METAL WORK STATION BEARING ON LEFT CIRCA 1900 ROLLS FOR BENDING STEEL WINDMILL BLADES TO PROPER CURVATURE AND ON RIGHT CIRCA 1900 BEADING MACHINE FOR ADDING STIFFENING CREASES TO THE EDGES OF SHEET METAL PARTS SUCH AS BLADES. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  17. 44. SOUTHWEST TO CIRCA 1900 SHEET METAL BRAKE, THE MACHINE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    44. SOUTHWEST TO CIRCA 1900 SHEET METAL BRAKE, THE MACHINE USED TO BEND SHEET METAL TO EXACT ANGLES AS IN STEEL WATER TANK MANUFACTURE. IN THE BACKGROUND IS THE INTERIOR WEST WALL OF THE FACTORY, ITS SHELVES BEARING WATER PUMPS, PARTS FOR PUMPS AND WATER SUPPLY EQUIPMENT, AND NEW OLD STOCK MERCHANDISE. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  18. 45. WEST TO CIRCA 1900 SHEET METAL SHEAR, THE MACHINE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    45. WEST TO CIRCA 1900 SHEET METAL SHEAR, THE MACHINE USED TO CUT SHEET METAL USED IN WINDMILLS AND WATER TANKS. IN THE BACKGROUND IS THE INTERIOR WEST WALL OF THE FACTORY, ITS SHELVES BEARING WATER PUMPS, PARTS FOR PUMPS AND WATER SUPPLY EQUIPMENT, AND NEW OLD STOCK MERCHANDISE. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  19. Overview of Boiler House and Sheet Metal and Electrical Shops ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of Boiler House and Sheet Metal and Electrical Shops Building (center - with single large chimney), note the monitor on the original section of the Boiler House Building, view facing north - Kahului Cannery, Plant No. 28, Boiler House, Sheet Metal and Electrical Shops, 120 Kane Street, Kahului, Maui County, HI

  20. Modeling of Sandwich Sheets with Metallic Foam

    NASA Astrophysics Data System (ADS)

    Mata, H.; Jorge, R. Natal; Santos, A.; Fernandes, A. A.; Valente, R. A. F.; Parente, M. P. L.

    2011-08-01

    World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new lightweight and energy absorbing materials. On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores foam is presented and some numerical examples are presented. In order to validate those results mechanical experiments are carried out. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. There are two variants of this model available on ABAQUS: the volumetric hardening model and the isotropic hardening model. As a first approximation we chose the isotropic hardening variant. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Based on this constitutive model for the foam, numerical simulations of the tensile and bulge test will be conducted. The numerical results will be validated using the data obtained from the experimental results.

  1. Modeling of Sandwich Sheets with Metallic Foam

    SciTech Connect

    Mata, H.; Jorge, R. Natal; Fernandes, A. A.; Parente, M. P. L.; Santos, A.; Valente, R. A. F.

    2011-08-22

    World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new lightweight and energy absorbing materials. On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores foam is presented and some numerical examples are presented. In order to validate those results mechanical experiments are carried out. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. There are two variants of this model available on ABAQUS: the volumetric hardening model and the isotropic hardening model. As a first approximation we chose the isotropic hardening variant. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Based on this constitutive model for the foam, numerical simulations of the tensile and bulge test will be conducted. The numerical results will be validated using the data obtained from the experimental results.

  2. Method and apparatus for determining weldability of thin sheet metal

    DOEpatents

    Goodwin, Gene M.; Hudson, Joseph D.

    1988-01-01

    A fixture is provided for testing thin sheet metal specimens to evaluate hot-cracking sensitivity for determining metal weldability on a heat-to-heat basis or through varying welding parameters. A test specimen is stressed in a first direction with a load selectively adjustable over a wide range and then a weldment is passed along over the specimen in a direction transverse to the direction of strain to evaluate the hot-cracking characteristics of the sheet metal which are indicative of the weldability of the metal. The fixture provides evaluations of hot-cracking sensitivity for determining metal weldability in a highly reproducible manner with minimum human error.

  3. Working with Design: A Package for Sheet Metal

    ERIC Educational Resources Information Center

    Fiebich, Paul D.

    1974-01-01

    The author describes a design approach used to study sheet metal layout in junior high and high school mechanical drafting courses. Students observe packaging in stores, study package construction, and design and produce their own packages. (EA)

  4. Direct evidence of metallic bands in a monolayer boron sheet

    NASA Astrophysics Data System (ADS)

    Feng, Baojie; Zhang, Jin; Liu, Ro-Ya; Iimori, Takushi; Lian, Chao; Li, Hui; Chen, Lan; Wu, Kehui; Meng, Sheng; Komori, Fumio; Matsuda, Iwao

    2016-07-01

    The search for metallic boron allotropes has attracted great attention in the past decades and recent theoretical works predict the existence of metallicity in monolayer boron. Here, we synthesize the β12-sheet monolayer boron on a Ag(111) surface and confirm the presence of metallic boron-derived bands using angle-resolved photoemission spectroscopy. The Fermi surface is composed of one electron pocket at the S ¯ point and a pair of hole pockets near the X ¯ point, which is supported by the first-principles calculations. The metallic boron allotrope in β12 sheet opens the way to novel physics and chemistry in material science.

  5. Joining of Thin Metal Sheets by Shot Peening

    NASA Astrophysics Data System (ADS)

    Harada, Yasunori

    2011-01-01

    In shot peening the substrate undergoes large plastic deformation near the surface due to the hit with shots. The plastic flow areas formed by cold working may form the surface layer. Authors have recently proposed new joining methods using shot peening, shot lining and shot caulking. Our approach has been applied to the butt joining of the dissimilar metal sheets. In the present study, joining of thin metal sheets using a shot peening process was investigated to improve the joinability. In the joined section, the edge of sheets is the equally-spaced slits. In this method, the convex edges of the sheet are laid on top of the other sheet. Namely, the two sheets are superimposed in the joining area. When the connection is shot-peened, the material of the convex area undergoes large plastic deformation near the surface due to the collision of shots. In this process, particularly noteworthy is the plastic flow near surface layer. The convex edges of the sheet can be joined to the other sheet, thus two sheets are joined each other. In the experiment, the shot peening treatment was performed by using an air-type peening machine. The shots used were made of high carbon cast steel. Air pressure was 0.6 MPa and peening time was in the range of 30-150s. The peening conditions were controlled in the experiment. The thin sheets were commercial low-carbon steel, stainless steel, pure aluminum, and aluminium alloy. The effects of processing conditions on the joinability were mainly examined. The joint strength increased with the kinetic energy of shots. It was found that the present method was effective for joining of thin metal sheets.

  6. Precision Small Angle Bending of Sheet Metals Using Shear Deformation

    NASA Astrophysics Data System (ADS)

    Hirota, Kenji; Mori, Yorifumi

    This paper deals with a new method to bend sheet metals at a small angle precisely, in which a sheet metal is slightly bent by shear deformation at negative punch-die clearance. Deformation behavior and key factors affecting on the bend angle were studied in detail with pure aluminum sheets. It was proved that the bend angle was changed in proportion to both punch penetration and negative punch-die clearance within a certain range. The same was true for high-strength steel and phosphor bronze, which are difficult to bend precisely by conventional methods due to large springback after unloading. By using this relationship as a control law, four kinds of sheet metals were precisely bent within a few degrees. This method was applied to correct the angular errors in U-bend products of high-strength steel and to bend leaf springs of phosphor bronze at an arbitrary small angle.

  7. Mode I fracture of sheet metal

    NASA Astrophysics Data System (ADS)

    Pardoen, T.; Hachez, F.; Marchioni, B.; Blyth, P. H.; Atkins, A. G.

    2004-02-01

    The perceived wisdom about thin sheet fracture is that (i) the crack propagates under mixed mode I & III giving rise to a slant through-thickness fracture profile and (ii) the fracture toughness remains constant at low thickness and eventually decreases with increasing thickness. In the present study, fracture tests performed on thin DENT plates of various thicknesses made of stainless steel, mild steel, 6082-O and NS4 aluminium alloys, brass, bronze, lead, and zinc systematically exhibit (i) mode I "bath-tub", i.e. "cup & cup", fracture profiles with limited shear lips and significant localized necking (more than 50% thickness reduction), (ii) a fracture toughness that linearly increases with increasing thickness (in the range of 0.5- 5 mm). The different contributions to the work expended during fracture of these materials are separated based on dimensional considerations. The paper emphasises the two parts of the work spent in the fracture process zone: the necking work and the "fracture" work. Experiments show that, as expected, the work of necking per unit area linearly increases with thickness. For a typical thickness of 1 mm, both fracture and necking contributions have the same order of magnitude in most of the metals investigated. A model is developed in order to independently evaluate the work of necking, which successfully predicts the experimental values. Furthermore, it enables the fracture energy to be derived from tests performed with only one specimen thickness. In a second modelling step, the work of fracture is computed using an enhanced void growth model valid in the quasi plane stress regime. The fracture energy varies linearly with the yield stress and void spacing and is a strong function of the hardening exponent and initial void volume fraction. The coupling of the two models allows the relative contributions of necking versus fracture to be quantified with respect to (i) the two length scales involved in this problem, i.e. the void spacing

  8. WORKER REMOVING SLAG FROM THE MOLTEN METAL BATH IN THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    WORKER REMOVING SLAG FROM THE MOLTEN METAL BATH IN THE ELECTRIC FURNACE AFTER ADDING A CHEMICAL COAGULANT TO FORCE IT TO THE SURFACE. - Southern Ductile Casting Company, Melting, 2217 Carolina Avenue, Bessemer, Jefferson County, AL

  9. Thermal conductance of multilayered metallic sheets

    NASA Astrophysics Data System (ADS)

    Fletcher, L. S.; Blanchard, D. G.; Kinnear, K. P.

    1991-06-01

    An experimental investigation was conducted to determine the thermal conductivity, the overall thermal conductance, and the thermal contact conductance between layers of stacked aluminum alloy 3004, 5042, and 5182 sheet. Tests were conducted for aluminum sample thicknesses of 0.0305 to 0.3074 cm (0.012 to 0.121 in.), mean junction temperatures of 79.5 and 165.5 C (175 and 330 F), and contact pressures of 0.689 to 10.34 MPa (100 to 1500 psi). The overall thermal conductance increased with increasing contact pressure and increasing temperature. It decreased as the number of aluminum layers was increased. The experimental data were used to derive thermal contact conductance between layers of stacked aluminum sheet. From these derived values, a correlation for the thermal contact conductance was developed. The resulting expressions are presented as a function of dimensionless parameters for the layer material, apparent contact pressure, and mean junction temperature.

  10. Formability Evaluation of Sheet Metals Based on Global Strain Distribution

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Lin, Jianping; Min, Junying; Ye, You; Kang, Liugen

    2016-04-01

    According to the conventional methods for formability evaluation, e.g., forming limit curve (FLC), limit dome height, and total elongation, inconsistent results are observed when comparing the formability of four advanced high-strength steels (AHSS) with an ultimate tensile strength grade of 1000 MPa. The strain distribution analysis with the aid of digital image correlation technique shows that different uniform deformation capabilities of sheet metals under the same loading conditions are responsible for this inconsistency. In addition, metallurgical analysis suggests that inhomogeneous microstructure distribution and phase transformation during deformation in some materials play important roles in the uniform deformation capability of sheet metal. Limit strains on the commonly used FLC only relate to the major and minor strains of local deforming elements associated with the onset of necking. However, the formability of a sheet metal component is determined by the strain magnitudes of all deforming elements involved during the forming process. Hence, the formability evaluation of sheet metals from a global aspect is more applicable for practical engineering. A new method based on two indices (i.e., which represent global formability and uniform deformation capability, respectively) is proposed to evaluate the formability of sheet metals based on global strain distribution. The formability and evolution of deformation uniformity of the investigated AHSS at different stress states are studied with this new method. Compared with other formability evaluation methods, the new method is demonstrated to be more appropriate for practical engineering, and it is applicable to both in-plane and out-of-plane deformation. Additionally, the global formability of sheet metals can be more comprehensively understood with this new method.

  11. Formability Evaluation of Sheet Metals Based on Global Strain Distribution

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Lin, Jianping; Min, Junying; Ye, You; Kang, Liugen

    2016-06-01

    According to the conventional methods for formability evaluation, e.g., forming limit curve (FLC), limit dome height, and total elongation, inconsistent results are observed when comparing the formability of four advanced high-strength steels (AHSS) with an ultimate tensile strength grade of 1000 MPa. The strain distribution analysis with the aid of digital image correlation technique shows that different uniform deformation capabilities of sheet metals under the same loading conditions are responsible for this inconsistency. In addition, metallurgical analysis suggests that inhomogeneous microstructure distribution and phase transformation during deformation in some materials play important roles in the uniform deformation capability of sheet metal. Limit strains on the commonly used FLC only relate to the major and minor strains of local deforming elements associated with the onset of necking. However, the formability of a sheet metal component is determined by the strain magnitudes of all deforming elements involved during the forming process. Hence, the formability evaluation of sheet metals from a global aspect is more applicable for practical engineering. A new method based on two indices (i.e., which represent global formability and uniform deformation capability, respectively) is proposed to evaluate the formability of sheet metals based on global strain distribution. The formability and evolution of deformation uniformity of the investigated AHSS at different stress states are studied with this new method. Compared with other formability evaluation methods, the new method is demonstrated to be more appropriate for practical engineering, and it is applicable to both in-plane and out-of-plane deformation. Additionally, the global formability of sheet metals can be more comprehensively understood with this new method.

  12. 17. VIEW OF FORMING EQUIPMENT, DISCS CUT FROM METAL SHEETS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF FORMING EQUIPMENT, DISCS CUT FROM METAL SHEETS WERE FORMED INTO SHAPES. (7/2/86) - Rocky Flats Plant, Uranium Rolling & Forming Operations, Southeast section of plant, southeast quadrant of intersection of Central Avenue & Eighth Street, Golden, Jefferson County, CO

  13. A Collaborative Design Curriculum for Reviving Sheet Metal Handicraft

    ERIC Educational Resources Information Center

    Chan, Patrick K. C.

    2015-01-01

    Galvanised sheet metal was a popular and important material for producing handmade home utensils in Hong Kong from the 1930s onwards. It was gradually replaced by new materials like stainless steel and plastic because similar goods made with these are cheaper, more standardised, more durable and of much better quality. The handicrafts behind sheet…

  14. Introduction to Sheet Metal. Introduction to Construction Series. Instructor Edition.

    ERIC Educational Resources Information Center

    Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    This competency-based curriculum guide on the specialty area of sheet metal is part of the Introduction to Construction series. The series is designed with the flexible training requirements of open shop contractors, preapprenticeship programs, multicraft high school programs, technology education programs, and cooperative education programs in…

  15. Formability of porous tantalum sheet-metal

    NASA Astrophysics Data System (ADS)

    Nebosky, Paul S.; Schmid, Steven R.; Pasang, Timotius

    2009-08-01

    Over the past ten years, a novel cellular solid, Trabecular Metal™, has been developed for use in the orthopaedics industry as an ingrowth scaffold. Manufactured using chemical vapour deposition (CVD) on top of a graphite foam substrate, this material has a regular matrix of interconnecting pores, high strength, and high porosity. Manufacturing difficulties encourage the application of bending, stamping and forming technologies to increase CVD reactor throughput and reduce material wastes. In this study, the bending and forming behaviour of Trabecular Metal™ was evaluated using a novel camera-based system for measuring surface strains, since the conventional approach of printing or etching gridded patterns was not feasible. A forming limit diagram was obtained using specially fabricated 1.65 mm thick sheets. A springback coefficient was measured and modeled using effective hexagonal cell arrangements.

  16. Metal-material workers and lung cancer in Japan.

    PubMed

    Hirayama, T

    1976-01-01

    The distribution by occupation of 39,255 lung cancer deaths in eight years, from 1960 to 1967, was analyzed. An age-standardized comparison of actual deaths and expected deaths revealed that cancer of the lung had tendency to occur with a significantly higher frequency in (1) metal material workers (Obs., 232; Exp., 176.5), and (2) workers in mining and quarrying occupations (Obs., 151; Exp., 127.9). By similar analysis, farmers, miners, and metal-material workers were noted as high-risk occupations for stomach cancer and clerical workers, and farmers were noted as such for leukemia. The value of occupational cancer in monitoring by such a simple analysis was stressed (see Figure 1). PMID:1069513

  17. Ultrasonic metal sheet thickness measurement without prior wave speed calibration

    NASA Astrophysics Data System (ADS)

    Dixon, S.; Petcher, P. A.; Fan, Y.; Maisey, D.; Nickolds, P.

    2013-11-01

    Conventional ultrasonic mensuration of sample thickness from one side only requires the bulk wave reverberation time and a calibration speed. This speed changes with temperature, stress, and microstructure, limiting thickness measurement accuracy. Often, only one side of a sample is accessible, making in situ calibration impossible. Non-contact ultrasound can generate multiple shear horizontal guided wave modes on one side of a metal plate. Measuring propagation times of each mode at different transducer separations, allows sheet thickness to be calculated to better than 1% accuracy for sheets of at least 1.5 mm thickness, without any calibration.

  18. Methyl bromide intoxication in four field-workers during removal of soil fumigation sheets.

    PubMed

    Herzstein, J; Cullen, M R

    1990-01-01

    Methyl bromide is a highly toxic and penetrating compound used extensively as an insecticide for dry foodstuffs and as a soil fumigant (in greenhouses and fields) for the control of nematodes, fungi, and weeds. More than 300 cases of systemic poisoning and 60 fatalities attributable to methyl bromide have been reported [Alexeeff and Kilgore, 1983], resulting in substantial regulations concerning its handling, storage, application, and disposal. A recent exposure incident at a Connecticut nursery represents to our knowledge the first report of toxicity stemming from exposures in the field during removal of plastic sheets days after injection of methyl bromide into soil. Following removal of polyethylene sheets covering soil fumigated with methyl bromide, four field-workers developed fatigue and light-headedness and 3 workers noted progressive respiratory, gastrointestinal (GI), and neurologic symptoms. The acute systemic symptoms improved over several days, but later-onset neuropsychiatric symptoms persisted for several weeks. This incident stresses the need for improved worker education and strict adherence to safety precautions during all stages of methyl bromide fumigation and raises the possibility of an increased risk of toxicity associated with methyl bromide fumigation during a cool season. PMID:2305812

  19. Development of sheet-metal parabolic-trough reflector panels

    SciTech Connect

    Biester, A.W.

    1982-06-01

    Efforts to develop accurate, durable, and mass producible sheet metal parabolic trough solar collectors and the associated support for the collectors are described. The design considered is similar to an automobile hood, a two-piece sheet metal structure consisting of a formed steel frame or stiffening panel and a smooth contoured skin. The two pieces may be bonded or welded to form a rigid structure, and a reflective surface applied such as a film, glass mirror, or any of the presently utilized materials. The work encompassed material selection, adhesive selection and testing, tool design and fabrication, prototype panel production, and design and development of torque tube assemblies on which the trough is inclined. Appended are results of adhesive bonding studies. It is found that high volume technology can be used to produce accurate and structurally sound reflector panels, and one configuration has been selected for fabrication in suitable quantities for performance testing. (LEW)

  20. Ductile damage prediction in sheet and bulk metal forming

    NASA Astrophysics Data System (ADS)

    Badreddine, Houssem; Labergère, Carl; Saanouni, Khemais

    2016-04-01

    This paper is dedicated to the presentation of an advanced 3D numerical methodology for virtual sheet and/or bulk metal forming simulation to predict the anisotropic ductile defects occurrence. First, the detailed formulation of thermodynamically-consistent fully coupled and fully anisotropic constitutive equations is given. The proposed constitutive equations account for the main material nonlinearities as the anisotropic plastic flow, the mixed isotropic and kinematic hardening and the anisotropic ductile damage under large inelastic strains. Second, the related numerical aspects required to solve the initial and boundary value problem (IBVP) are very briefly presented in the framework of the 3D finite element method. The global resolution schemes as well as the local integration schemes of the fully coupled constitutive equations are briefly discussed. Finally, some typical examples of sheet and bulk metal forming processes are numerically simulated using the proposed numerical methodology.

  1. Electromagnetic confinement and movement of thin sheets of molten metal

    SciTech Connect

    Lari, R.J.; Praeg, W.F.; Turner, L.R.

    1990-03-06

    This patent describes an apparatus capable of producing a combination of magnetic fields that can retain a metal in liquid form in a region having a smooth vertical boundary including a levitation magnet that produces low frequency magnetic field traveling waves to retain the metal and a stabilization magnet that produces a high frequency magnetic field to produce a smooth vertical boundary. As particularly adapted to the casting of solid metal sheets, a metal in liquid form can be continuously fed into one end of the confinement region produced by the levitation and stabilization magnets and removed in solid form from the other end of confinement region. An additional magnet may be included for support at the edges of the confinement region where eddy currents loop.

  2. Electromagnetic confinement and movement of thin sheets of molten metal

    SciTech Connect

    Lari, R.J.; Praeg, W.F.; Turner, L.R.

    1988-10-18

    An apparatus capable of producing a combination of magnetic fields that can retain a metal in liquid form in a region having a smooth vertical boundary including a levitation magnet that produces low frequency magnetic field traveling waves to retain the metal and a stabilization magnet that produces a high frequency magnetic field to produce a smooth vertical boundary. As particularly adapted to the casting of solid metal sheets, a metal in liquid form can be continuously fed into one end of the confinement region produced by the levitation and stabilization magnets and removed in solid form from the other end of confinement region. An additional magnet may be included for support at the edges of the confinement region where eddy currents loop.

  3. Electromagnetic confinement and movement of thin sheets of molten metal

    DOEpatents

    Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1990-01-01

    An apparatus capable of producing a combination of magnetic fields that can retain a metal in liquid form in a region having a smooth vertical boundary including a levitation magnet that produces low frequency magnetic field traveling waves to retain the metal and a stabilization magnet that produces a high frequency magnetic field to produce a smooth vertical boundary. As particularly adapted to the casting of solid metal sheets, a metal in liquid form can be continuously fed into one end of the confinement region produced by the levitation and stabilization magnets and removed in solid form from the other end of confinement region. An additional magnet may be included for support at the edges of the confinement region where eddy currents loop.

  4. Electronic and Magnetic Properties of Metal-Doped BN Sheet: A First-Principles Study

    SciTech Connect

    Zhou, Yungang; Xiao-Dong, J.; Wang, Zhiguo; Xiao, Haiyan Y.; Gao, Fei; Zu, Xiaotao T.

    2010-07-21

    Electronic and magnetic properties of BN sheet doped with 3d transition metals (Fe, Co and Ni) have been investigated using ab initio calculations. Our calculations show many interesting physical properties in metal-doped BN sheet. Fe-doped BN sheet is a half-metal with the magnetic moment of 2.0 μB, and Co-doped BN sheet becomes a narrow-gap semiconductor with the magnetic moment of 1.0 μB. However, no magnetic moment is induced on Ni-doped BN sheet, which has the same band gap as pristine BN sheet. Furthermore, Fe atom is easy to form isolated particle on BN sheet, while Ni and Co atoms are likely to form sheet-supported metal nanotemplate. These results are useful for spintronics application and could help in the development of magnetic nanotructures and metallic nanotemplate at room temperature.

  5. Thermographic imaging of cracks in thin metal sheets

    NASA Technical Reports Server (NTRS)

    Cramer, K. E.; Winfree, William P.; Howell, Patricia A.; Syed, Hazari; Renouard, Keith A.

    1992-01-01

    The presence of cracks significantly decreases the structural integrity of thin metal sheets used in aerospace applications. Thermographic detection of surface temperature variations due to these cracks is possible after external heating. An approximate line source of heat is used to produce an inplane flow of heat in the sheet. A crack in the sheet perturbs the inplane flow of heat and can be seen in an image of the surface temperature of the sheet. An effective technique for locating these perturbations is presented which reduces the surface temperature image to an image of variations in the inplane heat flow. This technique is shown to greatly increase the detectability of the cracks. This thermographic method has advantages over other techniques in that it is able to remotely inspect a large area in a short period of time. The effectiveness of this technique depends on the shape, position and orientation of the heat source with respect to the cracks as well as the extent to which the crack perturbs the surface heat flow. The relationship between these parameters and the variation in the heat flow is determined both by experimental and computational techniques. Experimental data is presented for through-the-thickness, subsurface and surface EDM notches. Data for through-the-thickness fatigue cracks are also presented.

  6. Laser-assisted sheet metal working in series production

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    2013-02-01

    Based on the demand for a responsible use of natural resources and energy the need for lightweight materials is increasing. The most common materials for lightweight production are high and highest strength steel. These materials are difficult to machine using conventional sheet metal working processes because the high strength leads to a limited formability and high tool wear. The Fraunhofer IPT developed the laser-assisted sheet metal working. Selective laser based heating of the part directly before machining softens the material locally. Thus the quality of the following cut can be increased, for example for shearing 1.4310 the clear cut surface ratio can be increased from 20% up to 100% using a shearing gap of 10% of the sheet thickness. Because of the softening of the material and thus the increased formability, parts with a higher complexity can be produced. For example 1.4310 can be bent laser-assisted with a radius of 0.25 mm instead of 2-3 mm using the conventional process. For the first time spring steel can be embossed with conventional tools up to 50% of the sheet thickness. For the implementation in series production a modular system upgrade "hy-PRESS" has been developed to include laser and scanner technology into existing presses. For decoupling the sensitive optical elements of the machine vibrations an active-passive damping system has been developed. The combination of this new hybrid process and the system technology allows to produce parts of high strength steel with a high complexity and quality.

  7. Respiratory hazards in hard metal workers: a cross sectional study.

    PubMed Central

    Meyer-Bisch, C; Pham, Q T; Mur, J M; Massin, N; Moulin, J J; Teculescu, D; Carton, B; Pierre, F; Baruthio, F

    1989-01-01

    A cross sectional study was conducted on 513 employees at three hard metal plants: 425 exposed workers (351 men, 74 women) and 88 controls (69 men, 19 women). Cough and sputum were more frequent in workers engaged in "soft powder" and presintering workshops compared with controls (12.5% and 16.5% v 3.5%). Spirometric abnormalities were more frequent among women in sintering and finishing workshops compared with control women (56.8% v 23.8%) and abnormalities of carbon monoxide test were more frequent in exposed groups than in controls; this difference was more pronounced in women (31.4% v 5.6%) than in men (18.5% v 13%). No significant correlation was observed between duration of exposure and age adjusted lung function tests. Slight abnormalities of chest radiographs (0/1, 1/1 according to ILO classification) were more frequent in exposed men than controls (12.8% v 1.9%) and mostly in soft powder workers. In subjects with abnormal chest radiographs FVC, FEV1 and carbon monoxide indices (fractional uptake of CO or CO transfer index or both) were lower compared with those with normal chest radiographs. Although relatively mild, the clinical, radiological, and functional abnormalities uncovered call for a regular supervision of workers exposed to hard metal dust. PMID:2787666

  8. Studies in Cup Drawing Behavior of Polymer Laminated Sheet Metal

    NASA Astrophysics Data System (ADS)

    Elnagmi, M.; Jain, M.; Bruhis, M.; Nielsen, K.

    2011-08-01

    Axisymmetric deep drawing behavior of a polymer laminated sheet metal (PLSM) is investigated using an axisymmetric cup drawing test. PLSMs are of interest as a replacement for painted finishes for automotive applications as they have the potential to achieve good quality long lasting and aesthetically appealing surfaces on stamped parts. However, there is limited understanding of PLSMs in automotive deep drawing situations to produce complex 3-D parts. The tests are carried out using well-controlled, laboratory-based, dual-action, servo-hydraulic forming presses under blank-holder force and punch displacement control conditions. An optical strain mapping system is used to measure the surface strains (and to construct 3D strain maps) from the film side of the deformed samples for a range of forming conditions. Deep drawing characteristics such as punch load versus punch displacement traces, strain distribution along the cup profile, flange wrinkling and fracture characteristics are experimentally assessed for stainless steel-plastic film laminated sheet materials. Also the effect of lamination pressure on wrinkling and delamination is investigated for a decorative pressure sensitive adhesive film affixed to the stainless steel sheet.

  9. Stabilization of ultrafine metal nanocatalysts on thin carbon sheets

    NASA Astrophysics Data System (ADS)

    Liu, Xiaofang; Cui, Xinrui; Liu, Yiding; Yin, Yadong

    2015-10-01

    A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the catalytic efficiency. The advantages of this ultra-stable architecture together with the densely dispersed catalytic sites were demonstrated by their high stability and superior catalytic activity in reducing hydrophilic 4-nitrophenol and hydrophobic nitrobenzene.A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the

  10. RIGGERS LOFT/PAINT SHOP/SHEET METAL SHOP, VIEW TO SOUTHEAST. THE PAINT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RIGGERS LOFT/PAINT SHOP/SHEET METAL SHOP, VIEW TO SOUTHEAST. THE PAINT SHOP WAS LOCATED IN THE CLOSEST CORNER OF THE BUILDING. THE SHEET METAL SHOP WAS LOCATED IN THE CORNER OF THE BUILDING ON THE RIGHT. THE RIGGERS LOFT WAS LOCATED IN THE PORTION OF THE BUILDING OUT OF VIEW TO THE LEFT - Rosie the Riveter National Historical Park, Riggers Loft/Paint Shop/Sheet Metal Shop, 1322 Canal Boulevard, Richmond, Contra Costa County, CA

  11. Self-Pierce Riveting Through 3 Sheet Metal Combinations

    NASA Astrophysics Data System (ADS)

    Andersson, Roger; Jonason, Paul; Pettersson, Tommy

    2011-05-01

    One way to reduce the CO2 emissions in automotives is to reduce the weight of the Body-In-White. One easy to achieve the weight reduction is to replace steel sheet materials with Al alloys, which is 3 times lighter. One issue is the joining process, especially with combinations between steel grades and AL alloys. Example of combination of mixed material combinations (Al-steel) might be found in the door structure. The reason is because of the AL alloys worthier crash performance so the automotive manufacturer might want to use crash impact beams made by high strength steels in a AL intensive door structure. The joining process between aluminum and steel are problematic due it's not possible to use traditional spot-welding technologies due to the materials total difference in microstructure characteristics as well thermal properties. To overcome this issue then mechanical as well adhesion joining are frequently used. This paper describes a development process and subsequently analysis of a self-pierce rivet (SPR) process between 3 sheet metal combinations. The multi-material combinations in this study were a combination of ultra high strength steels sheets (DP1000) and a Al-alloy (AA 6014). The analysis of the SPR process, in sense of mechanical strengths, has been done by peel- and shear tests. To reduce the amount of future physical tests a virtual FE-model has been developed for the process. This FE model of the process has been subsequently used to analyze the mechanical strength during plastic deformation. By using inverse analysis a correct contact algorithm has been evaluated that would predict the binding force between the rivet and sheet under a deformation process. With this new virtual model it will not only possible to analyze and develop the SPR process but also to achieve the final strength of the joint.

  12. Self-Pierce Riveting Through 3 Sheet Metal Combinations

    SciTech Connect

    Andersson, Roger; Jonason, Paul; Pettersson, Tommy

    2011-05-04

    One way to reduce the CO{sub 2} emissions in automotives is to reduce the weight of the Body-In-White. One easy to achieve the weight reduction is to replace steel sheet materials with Al alloys, which is 3 times lighter. One issue is the joining process, especially with combinations between steel grades and AL alloys. Example of combination of mixed material combinations (Al-steel) might be found in the door structure. The reason is because of the AL alloys worthier crash performance so the automotive manufacturer might want to use crash impact beams made by high strength steels in a AL intensive door structure. The joining process between aluminum and steel are problematic due it's not possible to use traditional spot-welding technologies due to the materials total difference in microstructure characteristics as well thermal properties. To overcome this issue then mechanical as well adhesion joining are frequently used. This paper describes a development process and subsequently analysis of a self-pierce rivet (SPR) process between 3 sheet metal combinations. The multi-material combinations in this study were a combination of ultra high strength steels sheets (DP1000) and a Al-alloy (AA 6014). The analysis of the SPR process, in sense of mechanical strengths, has been done by peel- and shear tests. To reduce the amount of future physical tests a virtual FE-model has been developed for the process. This FE model of the process has been subsequently used to analyze the mechanical strength during plastic deformation. By using inverse analysis a correct contact algorithm has been evaluated that would predict the binding force between the rivet and sheet under a deformation process. With this new virtual model it will not only possible to analyze and develop the SPR process but also to achieve the final strength of the joint.

  13. Application of Six Sigma Robust Optimization in Sheet Metal Forming

    SciTech Connect

    Li, Y.Q.; Cui, Z.S.; Ruan, X.Y.; Zhang, D.J.

    2005-08-05

    Numerical simulation technology and optimization method have been applied in sheet metal forming process to improve design quality and shorten design cycle. While the existence of fluctuation in design variables or operation condition has great influence on the quality. In addition to that, iterative solution in numerical simulation and optimization usually take huge computational time or endure expensive experiment cost In order to eliminate effect of perturbations in design and improve design efficiency, a CAE-based six sigma robust design method is developed in this paper. In the six sigma procedure for sheet metal forming, statistical technology and dual response surface approximate model as well as algorithm of 'Design for Six Sigma (DFSS)' are integrated together to perform reliability optimization and robust improvement. A deep drawing process of a rectangular cup is taken as an example to illustrate the method. The optimization solutions show that the proposed optimization procedure not only improves significantly the reliability and robustness of the forming quality, but also increases optimization efficiency with approximate model.

  14. Electrically driven rapidly vaporizing foils, wires and strips used for collision welding and sheet metal forming

    SciTech Connect

    Vivek, Anupam; Daehn, Glenn S; Taber, Geoffrey A; Johnson, Jason R

    2015-05-05

    A method for forming a piece of a sheet metal is performed by positioning a consumable body, made of metal, proximate to the piece of the sheet metal. The consumable body is rapidly vaporized, and the gas pressure generated thereby is directed into the piece of the sheet metal. This results in acceleration of the piece of sheet metal, and it is collided into a stationary body at a velocity, generally in excess of 200 m/s. Depending upon the type of stationary body, the piece of sheet metal is deformed into a predetermined shape or is welded onto the stationary body. The vaporization is accomplished by passing a high current of electricity into the consumable body. The effect of the vaporized metal may be augmented by additional components in the consumable body.

  15. A New Sheet Metal Forming System Based on Incremental Punching

    NASA Astrophysics Data System (ADS)

    Luo, Yuanxin

    Stamping is one of the most commonly used manufacturing processes. Everyday, millions of parts are formed by this process. The conventional stamping is to form a part in one or several operations with a press machine and a set/sets of dies. It is very efficient but is not cost effective for small batch production parts and prototypes as the dies are expensive and time consuming to make. Recently, with the increasing demands for low-volume and customer-made products, a die-less forming method, Incremental Sheet Metal Forming (ISMF), has become one of the leading R&D topics in the industry. ISMF uses a small generic tool to apply a sequence of operations along the given path to deform the sheet incrementally. These small deformations accumulate to form the final shape of the part. As a result, different parts can be made by the same setup. Despite of some 30 years of research and development, however, ISMF technology is still premature for industrial applications due to the following reasons: The accuracy of the part is limited; the surface roughness is poor; and the productivity is low. This motivates the presented research. In this research, a new incremental forming system based on incremental punching is designed and built. The system consists of a 3-axes CNC platform, a high speed hydraulic cylinder with a hemispherical forming tool, and a PC-based CNC control system. The hydraulic system provides the forming force to deform the sheet metal with constant stokes, while the CNC system positions the part. When forming a part, the forming tool punches the sheet metal along the given contour of the part punch by punch; when one layer of the part is completed, the forming tool moves down to the next layer; and the process is finished till all layers are completed. The CNC control system works with standard NC code, and hence, is easy to use. In order to ensure the desirable performance of the machine, dynamic analysis of the machine is necessary. The analysis is

  16. Flat sheet metal girders with very thin metal web. Part I : general theories and assumptions

    NASA Technical Reports Server (NTRS)

    Wagner, Herbert

    1931-01-01

    The object of this report was to develop the structural method of sheet metal girders and should for that reason be considered solely from this standpoint. The ensuing methods were based on the assumption of the infinitely low stiffness in bending of the metal web. This simplifies the basis of calculations to such an extent that many questions of great practical importance can be examined which otherwise cannot be included in any analysis of the bending stiffness of the buckled plate. This report refers to such points as the safety in buckling of uprights to the effect of bending flexibility of spars, to spars not set parallel, etc.

  17. Bifurcation Instability of sheet metal during spring-back

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Bong; Yang, Dong-Yol; Yoon, Jeong Whan

    2013-05-01

    In automotive and home appliance industries, there are many complex-shaped sheet metal components which need to be fabricated in multiple stamping operations. For example, the manufacturing of an outer case of washing machine consists of stamping followed by a bending operation. After the first stage of the stamping process, a large amount of spring-back takes place, and therefore, it is difficult to proceed to the next stage of the bending process. In the stamping process of that kind of sheet component with low geometric constraint, the forming area is large compared to the forming depth. Therefore, the formed part is in an unstable state and is less geometrically constrained, which causes a large amount of spring-back. To investigate this phenomenon, finite element analyses are carried out. During a spring-back analysis after forming, bifurcation takes place and the finite element solution procedure using the Newton-Raphson scheme becomes unstable. To get a stable post-bifurcation solution, a bifurcation algorithm is introduced at the bifurcation point. The deformed shapes obtained from finite element analyses are in good agreement with the experimental data. From this study, it is shown that the bifurcation behaviour enlarges the spring-back and the degree of dimensional error. To obtain additional possible post-bifurcation solutions, non-bifurcation analyses using initial guesses obtained in a modal analysis are carried. For the initial guesses, lowed four eigenmodes are utilized. Finally, the post-bifurcation behaviour and spring-back amount are investigated for various process parameters including the forming depth, punch width and corner radius.

  18. Towards Industrial Application of Damage Models for Sheet Metal Forming

    NASA Astrophysics Data System (ADS)

    Doig, M.; Roll, K.

    2011-05-01

    Due to global warming and financial situation the demand to reduce the CO2-emission and the production costs leads to the permanent development of new materials. In the automotive industry the occupant safety is an additional condition. Bringing these arguments together the preferable approach for lightweight design of car components, especially for body-in-white, is the use of modern steels. Such steel grades, also called advanced high strength steels (AHSS), exhibit a high strength as well as a high formability. Not only their material behavior but also the damage behavior of AHSS is different compared to the performances of standard steels. Conventional methods for the damage prediction in the industry like the forming limit curve (FLC) are not reliable for AHSS. Physically based damage models are often used in crash and bulk forming simulations. The still open question is the industrial application of these models for sheet metal forming. This paper evaluates the Gurson-Tvergaard-Needleman (GTN) model and the model of Lemaitre within commercial codes with a goal of industrial application.

  19. Optimization of Forming Processes with Different Sheet Metal Alloys

    NASA Astrophysics Data System (ADS)

    Sousa, Luísa C.; Castro, Catarina F.; António, Carlos C.

    2007-05-01

    Over the past decades relatively heavy components made of steel alloys comprise the majority of many manufactured parts due to steel's low cost, high formability and good strength. The desire to produce lightweight parts has led to studies searching for lighter and stronger materials such as aluminum alloys. However, they exhibit lower elastic stiffness than steel resulting in higher elastic strains causing known distortions such as spring-back and so decreasing accuracy of manufactured net-shape components. This paper presents a developed computational method to optimize the design of sheet metal processes using genetic algorithms. An inverse approach is considered so that the final geometry of the bended blank closely follows a prescribed one. The developed computational method couples a finite element forming simulation and an evolutionary algorithm searching the optimal design parameters of the process. The developed method searches the optimal parameters that ensure a perfect net-shape part. Different aluminum alloys candidates for automotive structural applications are considered and the optimal solutions are analyzed.

  20. Systematic Process Improvement of Sheet Metal Forming Processes

    NASA Astrophysics Data System (ADS)

    Carleer, Bart; Stippak, Michael

    2011-08-01

    The design of a forming process of sheet metal forming parts is a complex issue. Many boundary conditions must be fulfilled and many considerations must be made to come to a successful solution. Elimination wrinkles and splits very often need contrary measures. Many times the approach to come to a successful solution is an iterative process which is also dependent on the person who deals with the job. Generally this job has been solved with help of simulation software. AutoForm developed a methodology, systematic process improvement, to systematically approach this job. The systematic process improvement is a standardized way to effectively design forming processes. This systematical approach reduces the number of loops, gives transparency of the different solution statements and makes it easier to pass the work to a colleague. As a result the development of a forming process can be done faster, more reliable and less dependent on individuals. The systematic process improvement will be illustrated on the design of forming process of an automotive part.

  1. Steel--Project Fact Sheet: Recycling Acid and Metal Salts from Pickling Liquors

    SciTech Connect

    Poole, L.; Recca, L.

    1999-01-14

    Regenerating hydrochloric acids from metal finishing pickling baths reduces costs, wastes, and produces a valuable by-product--ferrous sulfate. Order your copy of this OIT project fact sheet and learn more about how your company can benefit.

  2. A new strategy for stiffness evaluation of sheet metal parts

    NASA Astrophysics Data System (ADS)

    Cai, Q.; Volk, W.; Düster, A.; Rank, E.

    2011-08-01

    In the automotive industry, surfaces of styling models are shaped very often in physical models. For example, in the styling process of a car body important design work is realized by clay models and the resulting geometry information typically comes from optical scans. The scanned data is given in the form of point clouds which is then utilized in the virtual planning process for engineering work, e.g. to evaluate the load-carrying capacity. This is an important measure for the stiffness of the car body panels. In this contribution, the following two issues are discussed: what is the suitable geometric representation of the stiffness of the car body and how it is computed if only discrete point clouds exist. In the first part, the suitable geometric representation is identified by constructing continuous CAD models with different geometric parameters, e.g. Gaussian curvature and mean curvature. The stiffness of models is then computed in LS-DYNA and the influence of different geometric parameters is presented based on the simulation result. In the second part, the point clouds from scanned data, rather than continuous CAD models, are directly utilized to estimate the Gaussian curvature, which is normally derived from continuous surfaces. The discrete Gauss-Bonnet algorithm is applied to estimate the Gaussian curvature of the point clouds and the sensitivity of the algorithm with respect to the mesh quality is analyzed. In this way, the stiffness evaluation process in an early stage can be accelerated since the transformation from discrete data to continuous CAD data is labor-intensive. The discrete Gauss-Bonnet algorithm is finally applied to a sheet metal model of the BMW 3 series.

  3. Electro-Hydraulic Forming of Sheet Metals: Free-forming vs. Conical-die Forming

    SciTech Connect

    Rohatgi, Aashish; Stephens, Elizabeth V.; Davies, Richard W.; Smith, Mark T.; Soulami, Ayoub; Ahzi, Said

    2012-05-01

    This work builds upon our recent advances in quantifying high-rate deformation behavior of sheet metals, during electro-hydraulic forming (EHF), using high-speed imaging and digital image correlation techniques. Following recent publication of an earlier manuscript, resulting from this project, in the Journal of Materials Processing Technology, this manuscript further details our results and compares forming behavior when the process is carried out inside an open-die or a conical die. It is anticipated that quantitative information of the sheet deformation history, made possible by the experimental technique developed in this work, will improve our understanding on the roles of strain-rate and sheet-die interactions in enhancing the sheet metal formability during high-rate forming. This knowledge will be beneficial to the automotive industry and enable them to fabricate light-weight sheet parts out of Al and advanced high strength steels.

  4. Material Models for Accurate Simulation of Sheet Metal Forming and Springback

    NASA Astrophysics Data System (ADS)

    Yoshida, Fusahito

    2010-06-01

    For anisotropic sheet metals, modeling of anisotropy and the Bauschinger effect is discussed in the framework of Yoshida-Uemori kinematic hardening model incorporating with anisotropic yield functions. The performances of the models in predicting yield loci, cyclic stress-strain responses on several types of steel and aluminum sheets are demonstrated by comparing the numerical simulation results with the corresponding experimental observations. From some examples of FE simulation of sheet metal forming and springback, it is concluded that modeling of both the anisotropy and the Bauschinger effect is essential for the accurate numerical simulation.

  5. Aircraft Assembly, Riveting and Surface Repair 1; Sheet Metal Work 2: 9855.02.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    The course outline will serve as a guide to the 11th grade student interested in sheet metal occupations. The course, 135 hours in length, covers the basic techniques of cutting and trimming, drilling and hole preparation of metals. Lecture and demonstration techniques are to be utilized, with emphasis on the use of visual aids, mock-ups,…

  6. Residual Stress In Sheet Metal Parts Made By Incremental Forming Process

    NASA Astrophysics Data System (ADS)

    Tanaka, Shigekazu; Nakamura, Tamotsu; Hayakawa, Kunio; Nakamura, Hideo; Motomura, Kazuo

    2007-05-01

    Incremental sheet metal forming, which uses a CNC forming stylus, is new flexible forming process not requiring the use of any expensive dies. We have applied the incremental forming process to dental prosthesis. This new process, however, posed difficult problems. After removing the outer portion of the incremental formed sheet metal part, the inner part is distorted. In this paper, the residual stress in the sheet metal part obtained by incremental forward stretch forming operations has been examined. Numerical simulations were conducted for solid elements. When small rigid ball slides on the metal sheet with a certain vertical feed, tension residual stress is produced in the upper layer of the sheet and compression stress in the lower. Then, the resultant moments throughout the sheet cause negative spring-back when the outer portion is removed. A systematic study of the behavior was conducted in this paper. Parameters considered included the tool radius and the vertical tool feed rate. The tip radius of forming stylus has a significant influence on the residual stress. The smaller radius of forming stylus, the larger bending force becomes. And new process with double forming styluses is examined to reduce the bending force.

  7. Residual Stress In Sheet Metal Parts Made By Incremental Forming Process

    SciTech Connect

    Tanaka, Shigekazu; Nakamura, Tamotsu; Hayakawa, Kunio; Nakamura, Hideo; Motomura, Kazuo

    2007-05-17

    Incremental sheet metal forming, which uses a CNC forming stylus, is new flexible forming process not requiring the use of any expensive dies. We have applied the incremental forming process to dental prosthesis. This new process, however, posed difficult problems. After removing the outer portion of the incremental formed sheet metal part, the inner part is distorted. In this paper, the residual stress in the sheet metal part obtained by incremental forward stretch forming operations has been examined. Numerical simulations were conducted for solid elements. When small rigid ball slides on the metal sheet with a certain vertical feed, tension residual stress is produced in the upper layer of the sheet and compression stress in the lower. Then, the resultant moments throughout the sheet cause negative spring-back when the outer portion is removed. A systematic study of the behavior was conducted in this paper. Parameters considered included the tool radius and the vertical tool feed rate. The tip radius of forming stylus has a significant influence on the residual stress. The smaller radius of forming stylus, the larger bending force becomes. And new process with double forming styluses is examined to reduce the bending force.

  8. Reduction of Springback of Sheet Metals by Bottoming

    NASA Astrophysics Data System (ADS)

    Ogawa, Takayuki; Hirahara, Atsushi; Yoshida, Fusahito

    2010-06-01

    The effect of bottoming on the reduction of springback is investigated by performing V-air-bending experiment on a high strength steel sheet of TS590MPa and the corresponding FE simulation. From the experiment, it was found that the springback is drastically decreased with increasing bottoming force. This is mainly due to the reduction of bending moment by compressive load acting normally to the sheet. At an early stage of bottoming, springback is also influenced by the change of geometrical rigidity of the bent sheet due to the straightening of ridge line warp. Since bottoming is a process of reverse deformation of tension-compression, the Bauschinger effect of materials should be taken into account for its accurate numerical simulation. 3D FE simulation using Yoshida-Uemori kinematic hardening model predicts well the bottoming effect.

  9. Resistance Spot Welding of AA5052 Sheet Metal of Dissimilar Thickness

    NASA Astrophysics Data System (ADS)

    Mat Din, N. A.; Zuhailawati, H.; Anasyida, A. S.

    2016-02-01

    Resistance spot welding of dissimilar thickness of AA5052 aluminum alloy was performed in order to investigate the effect of metal thickness on the weldment strength. Resistance spot welding was done using a spot welder machine available in Coraza Systems Sdn Bhd using a hemispherical of chromium copper electrode tip with radius of 6.00 mm under 14 kA of current and 0.02 bar of pressure for all thickness combinations. Lap joint configuration was produced between 2.0 mm thick sheet and 1.2 - 3.2 mm thick sheet, respectively. Microstructure of joint showed asymmetrical nugget shape that was larger on the thicker side indicating larger molten metal volume. Joint 2.0 mm x 3.2 mm sheets has the lowest hardness in both transverse direction and through thickness direction because less heat left in the weld nugget. The microstructure shows that this joint has coarse grains of HAZ. As thickness of sheet metal increased, the failure load of the joints increased. However, there was no linear correlation established between joint strength and metal thickness due to different shape of fusion zone in dissimilar thickness sheet metal.

  10. Study of Microstructure and Mechanical Properties Effects on Workpiece Quality in Sheet Metal Extrusion Process

    PubMed Central

    Suriyapha, Chatkaew; Bubphachot, Bopit; Rittidech, Sampan

    2015-01-01

    Sheet metal extrusion is a metal forming process in which the movement of a punch penetrates a sheet metal surface and it flows through a die orifice; the extruded parts can be deflected to have an extrusion cavity and protrusion on the opposite side. Therefore, this process results in a narrow region of highly localized plastic deformation due to the formation and microstructure effect on the work piece. This research investigated the characteristics of the material-flow behavior during the formation and its effect on the microstructure of the extruded sheet metal using the finite element method (FEM). The actual parts and FEM simulation model were developed using a blank material made from AISI-1045 steel with a thickness of 5 mm; the material's behavior was determined subject to the punch penetration depths of 20%, 40%, 60%, and 80% of the sheet thickness. The results indicated the formation and microstructure effects on the sheet metal extrusion parts and defects. Namely, when increasing penetration, narrowing the die orifice the material flows through, the material was formed by extruding, and defects were visibility, and the microstructure of the material's grains' size was flat and very fine. Extrusion defects were not found in the control material flow. The region of highly localized plastic deformation affected the material gain and mechanical properties. The FEM simulation results agreed with the experimental results. Moreover, FEM could be investigated as a tool to decrease the cost and time in trial and error procedures. PMID:26229979

  11. High Operating Temperature Liquid Metal Heat Transfer Fluids (Fact Sheet)

    SciTech Connect

    Not Available

    2012-12-01

    The University of California, Los Angeles, the University of California, Berkeley, and Yale University is one of the 2012 SunShot CSP R&D awardees for their Multidisciplinary University Research Initiative (MURI): High Operating Temperature (HOT) Fluids. This fact sheet explains the motivation, description, and impact of the project.

  12. Investigation of the static and dynamic fragmentation of metallic liquid sheets induced by random surface fluctuations

    NASA Astrophysics Data System (ADS)

    Durand, O.; Soulard, L.; Bourasseau, E.; Filippini, G.

    2016-07-01

    We perform molecular dynamics simulations to investigate the static and dynamic fragmentation of metallic liquid sheets of tin induced by random surface fluctuations. The static regime is analyzed by simulating sheets of different thicknesses, and the dynamic fragmentation is ensured by applying along the longitudinal direction of a sheet an instantaneous expansion velocity per initial unit length (expansion rate) with values ranging from 1 × 109 to 3 × 1010 s-1. The simulations show that the static/dynamic fragmentation becomes possible when the fluctuations of the upper and lower surfaces of the sheets can either overlap or make the local volume density of the system go down below a critical value. These two mechanisms cause locally in the sheet the random nucleation of pores of void, on a timescale that exponentially increases with the sheet thickness. Afterwards, the pores develop following distinct stages of growth, coalescence, and percolation, and later in time aggregates of liquid metal are formed. The simulations also show that the fragmentation of static sheets is characterized by relatively mono-dispersed surface and volume distributions of the pores and aggregates, respectively, whereas in extreme conditions of dynamic fragmentation (expansion rate typically in the range of 1 × 1010 s-1), the distributions are rather poly-dispersed and obey a power law decay with surface (volume). A model derived from the simulations suggests that both dynamic and static regimes of fragmentation are similar for expansion rates below typically 1 × 107 s-1.

  13. Adsorption of alkali and alkaline-earth metal atoms on the reconstructed graphene-like BN single sheet

    NASA Astrophysics Data System (ADS)

    Hao, Jun-Hua; Wang, Zheng-Jia; Wang, Yu-Fang; Yin, Yu-Hua; Jiang, Run; Jin, Qing-Hua

    2015-12-01

    A graphene-like BN single sheet with absorbed alkali and alkaline-earth metal atoms have been investigated by using a first-principles method within the framework of density functional theory (DFT). The electronic structure of BN sheet with adsorbed metal atoms is mainly determined by the metal electronic state which is near to the Fermi level owing to the wide band gap of pure BN sheet. So, we calculated the adsorption energy, charge transfer and work function after the metal adsorbed on BN sheet. We found that the interaction between the metal atoms and BN surface was very strong, and the stable adsorption site for all the adsorbed atoms concluded was high-coordination surface site (H-center) rather than the surface dangling bond sites from the perspective of simple bond-counting arguments. Our results indicate that the interaction of BN sheet with metal atoms could help in the development of metallic nanoscale devices.

  14. On the formability, geometrical accuracy, and surface quality of sheet metal parts produced by SPIF

    NASA Astrophysics Data System (ADS)

    Alves, M. L.; Silva, M. B.; Alves, L. M.; Martins, P. A. F.

    2008-11-01

    Conventional sheet metal forming processes are not suitable for flexible small-batch production and, therefore, are not appropriate for the growing agile manufacturing trends requiring very short life-cycles, development and production lead times. In fact, the present need for flexible sheet metal forming techniques requires the development of innovative technological solutions that are capable of reducing the fixed and capital costs of sheet metal forming to a level where small-batch production becomes economically feasible. Single point incremental forming (SPIF) is a new sheet metal forming process with a high potential economic payoff for rapid prototyping applications and for small quantity production. In general terms a typical SPIF set-up makes use of a small number of low cost active tools components; (i) a blankholder, (ii) a backing plate and (iii) a single point forming tool. The tool path is generated in a CNC machining center and during the process there is no backup die supporting the back surface of the sheet. Despite the contributions of many researchers on the development of industrial applications and better characterization of the forming limits of the process, several key topics related to the mechanics of deformation, likely mode of failure, geometric accuracy and surface quality of the formed parts remain little understood and scarcely systematized. This paper attempts to provide new contributions about the abovementioned issues by means of a comprehensive experimental investigation performed under laboratory controlled conditions.

  15. Shubnikov de Haas quantum oscillation of the surface states in the metallic Bismuth Telluride sheets

    NASA Astrophysics Data System (ADS)

    Chen, Taishi; Han, Junhao; Li, Zhaoguo; Song, Fengqi; Zhao, Bo; Wang, Xuefeng; Wang, Baigeng; Wan, Jianguo; Han, Min; Zhang, Rong; Wang, Guanghou

    2013-04-01

    Metallic Bi2Te3 crystalline sheets with the room-temperature resistivity of above 10 mΩ cm were prepared and their magnetoresistive transport was measured in a field of up to 9 T. The Shubnikov de Haas oscillations were identified from the secondly-derived magnetoresistance curves. While changing the angle between the field and normal axis of the sheets, we find that the oscillation periods present a cosine dependence on the angle. This indicates a two-dimensional transport due to the surface state. The work reveals a resolvable surface contribution to the overall conduction even in a metallic topological insulator.

  16. Detection of defects in formed sheet metal using medial axis transformation

    NASA Astrophysics Data System (ADS)

    Murmu, Naresh C.; Velgan, Roman

    2003-05-01

    In the metal forming processes, the sheet metals are often prone to various defects such as thinning, dents, wrinkles etc. In the present manufacturing environments with ever increasing demand of higher quality, detecting the defects of formed sheet metal using an effective and objective inspection system is the foremost norm to remain competitive in market. The defect detection using optical techniques aspire to satisfy its needs to be non-contact and fast. However, the main difficulties to achieve this goal remain essentially on the development of efficient evaluation technique and accurate interpretation of extracted data. The defect like thinning is detected by evaluating the deviations of the thickness in the formed sheet metal against its nominal value. The present evaluation procedure for determination of thickness applied on the measurements data is not without deficiency. To improve this procedure, a new evaluation approach based on medial axis transformation is proposed here. The formed sheet metals are digitized using fringe projection systems in different orientations, and afterwards registered into one coordinate frame. The medial axis transformation (MAT) is applied on the point clouds, generating the point clouds of MAT. This data is further processed and medial surface is determined. The thinning defect is detected by evaluating local wall thickness and other defects like wrinkles are determined using the shape recognition on the medial surface. The applied algorithm is simple, fast and robust.

  17. Simulation of metal transfer and weld pool development in gas metal arc welding of thin sheet metals

    NASA Astrophysics Data System (ADS)

    Wang, Fang

    Gas metal arc welding (GMAW) is the most commonly used arc welding method in industry for joining steels and aluminum alloys. But due to the mathematical difficulties associated with the free surface motion of the molten droplet and the weld pool, the process is not well understood and the development of new welding procedures in the manufacturing industry highly depends on expensive, time-consuming and experience-based trial and error. In this dissertation, numerical methods are developed to overcome the difficulties and to simulate the metal transfer and weld pool development in the GMAW of sheet metals. The simulations are validated by experiments and used to study an industrial welding process. A numerical procedure is first developed to model the free surface motion in fusion welding processes. Thermal and electromagnetic models are integrated with the fluid models. Recommendations are made on the selection and improvement of publicly available numerical algorithms, while alternative methods are also reviewed. A model combining the enthalpy, effective-viscosity and volume-of-fluid methods is then developed to simulate the metal transfer process in globular, spray and short-circuiting transfer modes. The model not only describes the influence of gravity, electromagnetic force and surface tension on droplet profile and transfer frequency, but also models the nonisothermal phenomena such as heat transfer and phase change. The melting front motion, the droplet detachment and oscillation, the satellite formation and the fluid convection within the droplet are analyzed. It has been found that the taper formation in spray transfer is closely related to the heat input on the unmelted portion of the welding wire, and the taper formation affects the globular-spray transition by decelerating the transfer process. Experiments with a high-speed motion analyzer validate the simulation results. The model is then extended to simulate the initiation, development and

  18. FE-Analysis of the Sheet Metal Forming Processes using Continuous Contact Treatment

    SciTech Connect

    Kim, Tae-Jeong; Yang, Dong-Yol

    2005-08-05

    In general, the sheet metal and die are described by finite elements for the simulation of the metal forming processes. Because the characteristics as continuum of the sheet metal are represented with triangles and rectangles, the errors occur inevitably in finite element analysis. Many contact schemes to describe the deformation modes exactly have been introduced in order to decrease these errors. In this study, a scheme for continuous contact treatment is proposed in order to consider the realistic behavior of contact phenomena during the forming process. The discrete mesh causes stepwise propagation of contact nodes of the sheet even though the contact region of the real forming process is altered very smoothly. It gives rise to convergence problem in case that the process, for example bending process, is sensitive to the contact between the sheet and the tools. For the verification of the proposed method, the compression forming of a tube is simulated and the contact pressures at each integration points are evaluated during deformation of the sheet. The analysis of hemi-spherical punch forming without blank holder is also presented in order to investigate the effects of the proposed algorithm.

  19. Blood concentration of essential trace elements and heavy metals in workers exposed to lead and cadmium.

    PubMed

    Wasowicz, W; Gromadzińska, J; Rydzyński, K

    2001-01-01

    The aim of the study was to determine blood concentration of essential trace elements (Se, Zn, Cu) and toxic metals (Pb, Cd), markers of antioxidant (activities of glutathione peroxidase (GPx), superoxidase dismutase and ceruloplasmin) and prooxidant processes (thiobarbituric acid reactive substances (TBARS)) in workers exposed to Pb and Cd. Forty three male workers of the lead-acid batteries department, aged 25-52 years, and twenty two workers, including 15 women, aged 36-51 years, exposed to Cd in the alkaline batteries department were examined. The reference group consisted of 52 healthy inhabitants of the same region. It was found that Se concentration and GPx activity in both erythrocytes and plasma of Cd exposed workers were significantly lower (p < 0.001) than in the reference group. We found an inverse linear correlation between blood Se and Cd concentrations in the workers exposed to Cd (r = -0.449; p < 0.01). Moreover, the activity of erythrocyte and plasma GPx was shown to be significantly lower in the study group of workers (p < 0.001). It was observed that TBARS concentration in plasma was significantly higher (p < 0.05) in the lead exposed workers than in the group without contact with Pb. Our results indicate that exposure to Pb and Cd affects the antioxidant potential of blood in workers exposed to heavy metals. PMID:11764849

  20. Biological monitoring of toxic metals - steel workers respiratory health survey

    NASA Astrophysics Data System (ADS)

    Pinheiro, T.; Almeida, A. Bugalho de; Alves, L.; Freitas, M. C.; Moniz, D.; Alvarez, E.; Monteiro, P.; Reis, M.

    1999-04-01

    The aim of this work is to search for respiratory system aggressors to which workers are submitted in their labouring activity. Workers from one sector of a steel plant in Portugal, Siderurgia Nacional (SN), were selected according to the number of years of exposure and labouring characteristics. The work reports on blood elemental content alterations and lung function tests to determine an eventual bronchial hyper-reactivity. Aerosol samples collected permit an estimate of indoor air quality and airborne particulate matter characterisation to further check whether the elemental associations and alterations found in blood may derive from exposure. Blood and aerosol elemental composition was determined by PIXE and INAA. Respiratory affections were verified for 24% of the workers monitored. There are indications that the occurrence of affections can be associated with the total working years. The influence of long-term exposure, health status parameters, and lifestyle factors in blood elemental variations found was investigated.

  1. Methodology development for the sustainability process assessment of sheet metal forming of complex-shaped products

    NASA Astrophysics Data System (ADS)

    Pankratov, D. L.; Kashapova, L. R.

    2015-06-01

    A methodology was developed for automated assessment of the reliability of the process of sheet metal forming process to reduce the defects in complex components manufacture. The article identifies the range of allowable values of the stamp parameters to obtain defect-free punching of spars trucks.

  2. Rubber-induced uniform laser shock wave pressure for thin metal sheets microforming

    NASA Astrophysics Data System (ADS)

    Shen, Zongbao; Wang, Xiao; Liu, Huixia; Wang, Yayuan; Wang, Cuntang

    2015-02-01

    Laser shock microforming of thin metal sheets is a new high velocity forming technique, which employs laser shock wave to deform the thin metal sheets. The spatial distribution of forming pressure is mainly dependent on the laser beam. A new type of laser shock loading method is introduced which gives a uniform pressure distribution. A low density rubber is inserted between the laser beam and the thin metal sheets. The mechanism of rubber-induced smoothing effect on confined laser shock wave is proposed. Plasticine is used to perform the smoothing effect experiments due to its excellent material flow ability. The influence of rubber on the uniformity of laser shock wave pressure is studied by measuring the surface micro topography of the deformed plasticine. And the four holes forming experiment is used to verify the rubber-induced uniform pressure on thin metal sheets surface. The research results show the possibility of smoothing laser shock wave pressure using rubber. And the good surface quality can be obtained under rubber dynamic loading.

  3. AN INVESTIGATION OF SHEET METAL DEFORMATION BEHAVIOR DURING ELECTRO-HYDRAULIC FORMING (EHF)

    SciTech Connect

    Rohatgi, Aashish; Stephens, Elizabeth V.; Davies, Richard W.; Smith, Mark T.

    2013-06-10

    This presentation will describe the recent advances in our understanding of sheet metal behavior during electro-hydraulic forming (EHF) process. This presentation will describe results of selected experiments that were designed to explore various aspects of the EHF process and how flaws, invariably present in all materials, behave under high-rate forming conditions.

  4. Assessment of nanoparticles and metal exposure of airport workers using exhaled breath condensate.

    PubMed

    Marie-Desvergne, Caroline; Dubosson, Muriel; Touri, Léa; Zimmermann, Eric; Gaude-Môme, Marcelline; Leclerc, Lara; Durand, Catherine; Klerlein, Michel; Molinari, Nicolas; Vachier, Isabelle; Chanez, Pascal; Mossuz, Véronique Chamel

    2016-01-01

    Aircraft engine exhaust increases the number concentration of nanoparticles (NP) in the surrounding environment. Health concerns related to NP raise the question of the exposure and health monitoring of airport workers. No biological monitoring study on this profession has been reported to date. The aim was to evaluate the NP and metal exposure of airport workers using exhaled breath condensate (EBC) as a non-invasive biological matrix representative of the respiratory tract. EBC was collected from 458 French airport workers working either on the apron or in the offices. NP exposure was characterized using particle number concentration (PNC) and size distribution. EBC particles were analyzed using dynamic light scattering (DLS) and scanning electron microscopy coupled to x-ray spectroscopy (SEM-EDS). Multi-elemental analysis was performed for aluminum (Al), cadmium (Cd) and chromium (Cr) EBC contents. Apron workers were exposed to higher PNC than administrative workers (p  <  0.001). Workers were exposed to very low particle sizes, the apron group being exposed to even smaller NP than the administrative group (p  <  0.001). The particulate content of EBC was brought out by DLS and confirmed with SEM-EDS, although no difference was found between the two study groups. Cd concentrations were higher in the apron workers (p  <  0.001), but still remained very low and close to the detection limit. Our study reported the particulate and metal content of airport workers airways. EBC is a potential useful tool for the non-invasive monitoring of workers exposed to NP and metals. PMID:27409350

  5. Enhancement of Incremental Sheet Metal Forming Technology by Means of Stretch Forming

    NASA Astrophysics Data System (ADS)

    Galdos, L.; Sukia, A.; Otegi, N.; Ortubay, R.; Ruiz De La Torre, A.; Forgas, A.; Rastellini, F.

    2011-01-01

    Incremental Sheet Forming (ISF) is a relatively new flexible sheet metal forming process mainly oriented to small batches production and prototyping. The technology has been conceived to enable flexible forming of sheet metal parts based on CNC governed punch movements, being the use of conventional milling machines possible if vertical maximum force is controlled. During the process, a simple shape punch is moved against the surface of the sheet, such that a localised deformation is caused, and the use of spatial punch movements enables the forming of complex 3D shapes. However, the process has some drawbacks: high geometrical inaccuracies, an emphasised problem in complex non-axisymmetric parts, poor final surface quality due to the friction between the punch and the blank, limitations to obtain steep walls and the need of large process times due to the nature of the process. In this paper, the stretch forming is used together with the Incremental Sheet Forming in order to overcome the process limitations, aiming to optimise the material flow and minimise the thinning. Numerical, Finite Element Modelling, and experimental results are presented using a real case study.

  6. Comparison of phosphor bronze metal sheet produced by twin roll casting and horizontal continuous casting

    NASA Astrophysics Data System (ADS)

    Hwang, J. D.; Li, B. J.; Hwang, W. S.; Hu, C. T.

    1998-08-01

    Much effort recently has been expended to study the strip casting process used to produce thin metal strip with a near final thickness. This process eliminates the need for hot rolling, consumes less energy, and offers a feasible method of producing various hard-to-shape alloys. The finer microstructure that results from the high cooling rate used during the casting process enhances mechanical properties. In this study, strips of phosphor bronzes (Cu-Sn-P) metal were produced using a twin roll strip casting process as well as a conventional horizontal continuous casting (HCC) process. The microstructures, macrosegregations, textures, and mechanical properties of the as-cast and as-rolled metal sheet produced by these two methods were examined carefully for comparative purposes. The results indicate that cast strip produced by a twin roll caster exhibit significantly less inverse segregation of tin compared to that produced by the HCC process. The mechanical properties including tensile strength, elongation, and microhardness of the products produced by the twin roll strip casting process are comparable to those of the HCC processed sheet. These properties meet specifications JIS H3110 and ASTM B 103M for commercial phosphor bronze sheet. The texture of the as-rolled sheet from these two processes, as measured from XRD pole figures, were found to be virtually the same, even though a significant difference exists between them in the as-cast condition.

  7. Comparison of Two Commercial FE-Codes for Sheet Metal Forming

    SciTech Connect

    Revuelta, A.; Larkiola, J.; Kanervo, K.; Korhonen, A. S.; Myllykoski, P.

    2007-05-17

    There is urgent need to develop new advanced fast and cost-effective mass-production methods for small sheet metal components. Traditionally progressive dies have been designed by using various CAD techniques. Recent results in mass production of small sheet metal parts using progressive dies and a transfer press showed that the tool design time may be cut in up to a half by using 3D finite element simulation of forming. In numerical simulation of sheet metal forming better constitutive models are required to obtain more accurate results, reduce the time for tool design and cut the production costs further. Accurate models are needed to describe the initial yielding, subsequent work hardening and to predict the formability. In this work two commercially available finite element simulation codes, PAM-STAMP and LS-DYNA, were compared in forming of small austenitic stainless steel sheet part for electronic industry. Several constitutive models were used in both codes and the results were compared. Comparisons were made between the same models in each of the codes and also between different models in the same code. Material models ranged from very simple to advanced ones, which took into account anisotropy and both isotropic and kinematic hardening behavior. In order to make a valid comparison we employed similar finite element meshes. The effects of the material models parameters were studied and the results were compared with experiments. The effects of the computational time were also studied.

  8. Optimum Design Of Addendum Surfaces In Sheet Metal Forming Process

    NASA Astrophysics Data System (ADS)

    Debray, K.; Sun, Z. C.; Radjai, R.; Guo, Y. Q.; Dai, L.; Gu, Y. X.

    2004-06-01

    The design of addendum surfaces in sheet forming process is very important for the product quality, but it is very time-consuming and needs tedious trial-error corrections. In this paper, we propose a methodology to automatically generate the addendum surfaces and then to optimize them using a forming modelling solver. The surfaces' parameters are taken as design variables and modified in course of optimization. The finite element mesh is created on the initial addendum surfaces and mapped onto the modified surfaces without remeshing operation. The Feasible Sequential Quadratic Programming (FSQP) is adopted as our algorithm of optimization. Two objective functions are used: the first one is the thickness function to minimize the thickness variation on the workpiece ; the second one is the appearance function aiming to avoid the scratching defects on the external surfaces of panels. The FSQP is combined with our "Inverse Approach" or "One Step Approach" which is a very fast forming solver. This leads to a very efficient optimization procedure. The present methodology is applied to a square box. The addendum surfaces are characterised by four geometrical variables. The influence of optimization criteria is studied and discussed.

  9. A Model Based Approach to Increase the Part Accuracy in Robot Based Incremental Sheet Metal Forming

    SciTech Connect

    Meier, Horst; Laurischkat, Roman; Zhu Junhong

    2011-01-17

    One main influence on the dimensional accuracy in robot based incremental sheet metal forming results from the compliance of the involved robot structures. Compared to conventional machine tools the low stiffness of the robot's kinematic results in a significant deviation of the planned tool path and therefore in a shape of insufficient quality. To predict and compensate these deviations offline, a model based approach, consisting of a finite element approach, to simulate the sheet forming, and a multi body system, modeling the compliant robot structure, has been developed. This paper describes the implementation and experimental verification of the multi body system model and its included compensation method.

  10. Laser-Assisted Sheet Metal Working of High Strength Steels in Serial Production

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    Within the sheet metal working industry the demand for thinner sheet materials with very high strength is growing due to the increasing need to save energy and a responsible use of natural resources. The high strength and the low ductility restricts using state of art technology to sheer, bend, emboss or deep draw parts with the needed complexity and quality. The Fraunhofer IPT developed a combination of laser-assisted preheating and conventional punching to a new hybrid technology which allows to shear, bend, emboss and draw high strength materials with a high quality and complexity in a serial production.

  11. EPA ensures oversight of worker safety and health at Superfund incinerator sites. Fact sheet

    SciTech Connect

    Not Available

    1993-09-01

    In response to increasing concern over the safety and health of hazardous waste workers at Superfund incinerator sites, the Environmental Protection Agency (EPA) recently established a joint EPA-Labor Superfund Health and Safety Task Force to coordinate activities designed to ensure vigorous oversight of occupationl safety and health at these sites. As a result of EPA/Labor Task Force-sponsored inspections, operators of the inspected incinerators have agreed to address the team's findings and to improve their safety and health programs. The EPA/Labor Task Force also has developed a draft 'Protocol for Safety and Health Inspections at Superfund Sites' to be used for inspections of all types of Superfund sites. In 1993, the EPA/Labor Task Force will continue to conduct additional Superfund incinerator site inspections. EPA believes that the initiaties launched with the EPA/Labor Task Force will ensure that the safety and health of workers engaged in hazardous waste cleanup activities is a top priority at these sites.

  12. Sheet metal stamping die design for warm forming

    DOEpatents

    Ghosh, Amit K.

    2003-04-22

    In metal stamping dies, by taking advantage of improved material flow by selectively warming the die, flat sections of the die can contribute to the flow of material throughout the workpiece. Local surface heating can be accomplished by placing a heating block in the die. Distribution of heating at the flat lower train central regions outside of the bend region allows a softer flow at a lower stress to enable material flow into the thinner, higher strain areas at the bend/s. The heating block is inserted into the die and is powered by a power supply.

  13. Effect of Forming Speed on Plastic Bending of Adhesively Bonded Sheet Metals

    NASA Astrophysics Data System (ADS)

    Takiguchi, Michihiro; Yoshida, Fusahito

    Using highly ductile acrylic adhesive, the present authors proposed a new technique of plastic bending of adhesively bonded sheet metals. In this process, the suppression of large transverse shear deformation occurring in the adhesive layer, which in some cases would induce the geometrical imperfection (so-called ‘gull-wing bend') and the delamination of the sheet, is one of the most important technical issues. In the present work, the effect of forming speed on bending deformation was investigated. From experimental observations in V-bending experiments of adhesively bonded aluminium sheets, as well as the corresponding numerical simulations which consider the viscoplasticity nature of the adhesive resin, it was found that the large shear deformation and ‘gull-wing bend' are successfully suppressed by high-speed forming since the deformation resistance of the adhesive resin becomes higher at a high strain rate.

  14. Thermally Sprayed Coatings as Effective Tool Surfaces in Sheet Metal Forming Applications

    NASA Astrophysics Data System (ADS)

    Franzen, V.; Witulski, J.; Brosius, A.; Trompeter, M.; Tekkaya, A. E.

    2011-06-01

    Two approaches to produce wear-resistant effective surfaces for deep drawing tools by thermal arc wire spraying of hard materials are presented. Arc wire spraying is a very economic coating technique due to a high deposition rate. The coated surface is very rough compared to that of conventional sheet metal forming tools. In the first approach, the coated surface is smoothed in a subsequent CNC-based incremental roller burnishing process. In this process, the surface asperities on the surface are flattened, and the roughness is significantly reduced. In the second approach, the hard material coatings are not sprayed directly on the tool but on a negative mould. Afterward, the rough "as-sprayed" side of the coating is backfilled with a polymer. The bonded hard metal shell is removed from the negative mould and acts as the surface of the hybrid sheet metal forming tool. Sheet metal forming experiments using tools based on these two approaches demonstrate that they are suitable to form high-strength steels. Owing to a conventional body of steel or cast iron, the first approach is suitable for large batch sizes. The application of the second approach lies within the range of small up to medium batch size productions.

  15. Electric-Field-Assisted Directed Assembly of Transition Metal Dichalcogenide Monolayer Sheets.

    PubMed

    Deng, Donna D; Lin, Zhong; Elías, Ana Laura; Perea-Lopez, Nestor; Li, Jie; Zhou, Chanjing; Zhang, Kehao; Feng, Simin; Terrones, Humberto; Mayer, Jeffrey S; Robinson, Joshua A; Terrones, Mauricio; Mayer, Theresa S

    2016-05-24

    Directed assembly of two-dimensional (2D) layered materials, such as transition metal dichalcogenides, holds great promise for large-scale electronic and optoelectronic applications. Here, we demonstrate controlled placement of solution-suspended monolayer tungsten disulfide (WS2) sheets on a substrate using electric-field-assisted assembly. Micrometer-sized triangular WS2 monolayers are selectively positioned on a lithographically defined interdigitated guiding electrode structure using the dielectrophoretic force induced on the sheets in a nonuniform field. Triangular sheets with sizes comparable to the interelectrode gap assemble with an observed preferential orientation where one side of the triangle spans across the electrode gap. This orientation of the sheets relative to the guiding electrode is confirmed to be the lowest energy configuration using semianalytical calculations. Nearly all sheets assemble without observable physical deformation, and postassembly photoluminescence and Raman spectroscopy characterization of the monolayers reveal that they retain their as-grown crystalline quality. These results show that the field-assisted assembly process may be used for large-area bottom-up integration of 2D monolayer materials for nanodevice applications. PMID:27082162

  16. Prediction Of Formability In Sheet Metal Forming Processes Using A Local Damage Model

    SciTech Connect

    Teixeira, P.; Santos, Abel; Cesar Sa, J.; Andrade Pires, F.; Barata da Rocha, A.

    2007-05-17

    The formability in sheet metal forming processes is mainly conditioned by ductile fracture resulting from geometric instabilities due to necking and strain localization. The macroscopic collapse associated with ductile failure is a result of internal degradation described throughout metallographic observations by the nucleation, growth and coalescence of voids and micro-cracks. Damage influences and is influenced by plastic deformation and therefore these two dissipative phenomena should be coupled at the constitutive level. In this contribution, Lemaitre's ductile damage model is coupled with Hill's orthotropic plasticity criterion. The coupling between damaging and material behavior is accounted for within the framework of Continuum Damage Mechanics (CDM). The resulting constitutive equations are implemented in the Abaqus/Explicit code, for the prediction of fracture onset in sheet metal forming processes. The damage evolution law takes into account the important effect of micro-crack closure, which dramatically decreases the rate of damage growth under compressive paths.

  17. Numerical simulation on multi-gripper stretch forming process for sheet metal

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Li, M. Z.; Peng, H. L.; Gu, S. H.

    2013-05-01

    Multi-gripper stretch forming (MGSF) is a new flexible forming process compared to traditional stretching forming process. Two kinds of MGSF process, back-vertical drawing (BVD) and front-vertical drawing (FVD) are compared in this study. Spherical-curved part is selected as the research object, and the finite numerical modes for BVD and FVD have been established, and the simulation results are carried out by dynamic explicit finite element analysis. The numerical results indicated that the sheet metal can get the shape of the die at a lower strain ratio and the stretch strain distribution was more uniform by the FVD, which can improve the forming quality of the formed parts. In addition, the sheet metal can be formed by FVD under smaller hydraulic cylinder strokes. The results may provide useful guidance on optimizing the MGSF equipment structure.

  18. Advanced material testing in support of accurate sheet metal forming simulations

    NASA Astrophysics Data System (ADS)

    Kuwabara, Toshihiko

    2013-05-01

    This presentation is a review of experimental methods for accurately measuring and modeling the anisotropic plastic deformation behavior of metal sheets under a variety of loading paths: biaxial compression test, hydraulic bulge test, biaxial tension test using a cruciform specimen, multiaxial tube expansion test using a closed-loop electrohydraulic testing machine for the measurement of forming limit strains and stresses, combined tension-shear test, and in-plane stress reversal test. Observed material responses are compared with predictions using phenomenological plasticity models to highlight the importance of accurate material testing. Special attention is paid to the plastic deformation behavior of sheet metals commonly used in industry, and to verifying the validity of constitutive models based on anisotropic yield functions at a large plastic strain range. The effects of using appropriate material models on the improvement of predictive accuracy for forming defects, such as springback and fracture, are also presented.

  19. Finite element simulation of sheet metal forming and springback using a crystal plasticity approach

    SciTech Connect

    Bertram, A.; Boehlke, T.; Krawietz, A.; Schulze, V.

    2007-05-17

    In this paper the application of a crystal plasticity model for body-centered cubic crystals in the simulation of a sheet metal forming process is discussed. The material model parameters are identified by a combination of a texture approximation procedure and a conventional parameter identification scheme. In the application of a cup drawing process the model shows an improvement of the strain and earing prediction as well as the qualitative springback results in comparison with a conventional phenomenological model.

  20. An expert system for ensuring the reliability of the technological process of cold sheet metal forming

    NASA Astrophysics Data System (ADS)

    Kashapova, L. R.; Pankratov, D. L.; Utyaganov, P. P.

    2016-06-01

    In order to exclude periodic defects in the parts manufacturing obtained by cold sheet metal forming a method of automated estimation of technological process reliability was developed. The technique is based on the analysis of reliability factors: detail construction, material, mechanical and physical requirements; hardware settings, tool characteristics, etc. In the work the expert system is presented based on a statistical accumulation of the knowledge of the operator (technologist) and decisions of control algorithms.

  1. Matched metal die compression molded structural random fiber sheet molding compound flywheel

    DOEpatents

    Kulkarni, Satish V.; Christensen, Richard M.; Toland, Richard H.

    1985-01-01

    A flywheel (10) is described that is useful for energy storage in a hybrid vehicle automotive power system or in some stationary applications. The flywheel (10) has a body of essentially planar isotropic high strength structural random fiber sheet molding compound (SMC-R). The flywheel (10) may be economically produced by a matched metal die compression molding process. The flywheel (10) makes energy intensive efficient use of a fiber/resin composite while having a shape designed by theory assuming planar isotropy.

  2. Matched metal die compression molded structural random fiber sheet molding compound flywheel. [Patent application

    DOEpatents

    Kulkarni, S.V.; Christensen, R.M.; Toland, R.H.

    1980-09-24

    A flywheel is described that is useful for energy storage in a hybrid vehicle automotive power system or in some stationary applications. The flywheel has a body of essentially planar isotropic high strength structural random fiber sheet molding compound (SMC-R). The flywheel may be economically produced by a matched metal die compression molding process. The flywheel makes energy intensive efficient use of a fiber/resin composite while having a shape designed by theory assuming planar isotropy.

  3. Layered SiC sheets: A promising metal-free catalyst for NO reduction.

    PubMed

    Feng, Jing wen; Liu, Yue jie; Zhao, Jing xiang

    2015-07-01

    Recently, the catalytic reduction is shown to be an effective method to remove the harmful NO. In terms of the high cost and limited supply of the traditional transition metal-based catalysts, the novel metal-free catalyst is highly desirable for NO reduction. Here, density functional theory (DFT) computations were performed to explore the potentials of layered SiC sheets as a metal-free catalyst for NO reduction. From our DFT results, it can be predicted that layered SiC sheets exhibit superior catalytic activity toward NO reduction. In particular, a dimer mechanism is shown to be more favorable than the direct dissociation one for NO reduction on this metal-free catalyst and a three-step mechanism is involved in this process: (1) the formation of a (NO)2 dimer on layered SiC sheet, followed by (2) its dissociation into N2O+Oad, and (3) the recovery of catalyst by subsequent NO. The trans-(NO)2 dimer might be a necessary intermediate, in which the calculated barrier for the rate-determining step along the energetically most favorable pathway is 0.722 eV. The high reactivity of layered SiC sheets may be attributed to the certain amount of charge transfer from the catalyst to (NO)2 dimer, which shortens the NN bonding and thus stabilizes these systems due to the extra electrons on the dimers. This excellent catalytic activity provides a useful guidance to design the next generation catalysts for NO reduction with lower cost and higher activity. PMID:26043660

  4. Process Simulation of Aluminium Sheet Metal Deep Drawing at Elevated Temperatures

    SciTech Connect

    Winklhofer, Johannes; Trattnig, Gernot; Sommitsch, Christof

    2010-06-15

    Lightweight design is essential for an economic and environmentally friendly vehicle. Aluminium sheet metal is well known for its ability to improve the strength to weight ratio of lightweight structures. One disadvantage of aluminium is that it is less formable than steel. Therefore complex part geometries can only be realized by expensive multi-step production processes. One method for overcoming this disadvantage is deep drawing at elevated temperatures. In this way the formability of aluminium sheet metal can be improved significantly, and the number of necessary production steps can thereby be reduced. This paper introduces deep drawing of aluminium sheet metal at elevated temperatures, a corresponding simulation method, a characteristic process and its optimization. The temperature and strain rate dependent material properties of a 5xxx series alloy and their modelling are discussed. A three dimensional thermomechanically coupled finite element deep drawing simulation model and its validation are presented. Based on the validated simulation model an optimised process strategy regarding formability, time and cost is introduced.

  5. Lower Restrictions for Sheet Metal Trimming Processes can Reduce Die Costs in The Automotive Industry

    NASA Astrophysics Data System (ADS)

    Hogg, Markus; Rohleder, Martin; Roll, Karl

    2011-05-01

    To reduce costs of trimming dies influencing parameters of the shearing process were identified, new technical approaches for a more cost efficient die design were developed, and comprehensive investigations on a sample tool were done. These approaches will be verified on a trimming die in series production. If this pilot application is successful, many sheet metal forming parts can be trimmed by less die investment in the future. In the automotive industry complex sheet metal forming parts are often trimmed by shearing. Ideally this shearing is done with a 90° angle between the cutting edge and the part surface. Because of complex part geometry different angles always occur. Often shearing angles and the effective sheet thickness increases so much that trimming in the working direction of the press machine is not possible anymore. In these cases sliding cams have to be used. That makes trimming dies expensive and maintenance intensive. For reliable trimming a good understanding of the process and its limitations is necessary. By not considering these limitations the tool can fail after a few operations or/and the resulting edge of the sheet metal part is no longer acceptable. In worst case a new tool has to be built or at least must be reworked. In operational practice so far only empirical values about limitations are known. The stability limit for trimming is not known for all shearing angles and for new high-strength materials. Therefore detailed investigations were done on a sample tool to determine these stability limits for different materials and shearing angles. The basis for starting these principle investigations was empirical values from operational practise. By using a high-quality material and a completely new shape for the trimming die elements both the reliable processable effective sheet thickness respectively the shearing angle as well as the acting forces could be optimized. In the basic investigations trimming in one direction was often still

  6. Development of a Prediction Model Based on RBF Neural Network for Sheet Metal Fixture Locating Layout Design and Optimization

    PubMed Central

    Wang, Zhongqi; Yang, Bo; Kang, Yonggang; Yang, Yuan

    2016-01-01

    Fixture plays an important part in constraining excessive sheet metal part deformation at machining, assembly, and measuring stages during the whole manufacturing process. However, it is still a difficult and nontrivial task to design and optimize sheet metal fixture locating layout at present because there is always no direct and explicit expression describing sheet metal fixture locating layout and responding deformation. To that end, an RBF neural network prediction model is proposed in this paper to assist design and optimization of sheet metal fixture locating layout. The RBF neural network model is constructed by training data set selected by uniform sampling and finite element simulation analysis. Finally, a case study is conducted to verify the proposed method. PMID:27127499

  7. Development of a Prediction Model Based on RBF Neural Network for Sheet Metal Fixture Locating Layout Design and Optimization.

    PubMed

    Wang, Zhongqi; Yang, Bo; Kang, Yonggang; Yang, Yuan

    2016-01-01

    Fixture plays an important part in constraining excessive sheet metal part deformation at machining, assembly, and measuring stages during the whole manufacturing process. However, it is still a difficult and nontrivial task to design and optimize sheet metal fixture locating layout at present because there is always no direct and explicit expression describing sheet metal fixture locating layout and responding deformation. To that end, an RBF neural network prediction model is proposed in this paper to assist design and optimization of sheet metal fixture locating layout. The RBF neural network model is constructed by training data set selected by uniform sampling and finite element simulation analysis. Finally, a case study is conducted to verify the proposed method. PMID:27127499

  8. Estimating risk during showering exposure to VOCs of workers in a metal-degreasing facility.

    PubMed

    Franco, Amaya; Costoya, Miguel Angel; Roca, Enrique

    2007-04-01

    The incremental risk of workers in a metal-degreasing facility exposed to volatile organic compounds (VOCs) present in the water supply during showering was estimated. A probabilistic and worst-case approach using specific-site concentration data and a generalized multipathway exposure model was applied. Estimates of hazard index and lifetime cancer risk were analyzed for each chemical and each route of exposure (inhalation and dermal absorption). The results showed that dermal exposure to trichloroethylene (TCE) and tetrachloroethylene (perchloroethylene, PCE) represented the main contribution to total risk. Although the inhalation route did not produce significant exposure, it was mainly influenced by the liquid flow rate of the shower. Lower values of this parameter during showering resulted in a significant reduction of both carcinogenic and noncarcinogenic risk, while decreasing water temperature produced a minimal effect on exposure by this pathway. The results obtained in the present study indicated that significant exposures of workers may be produced during showering in metal degreasing installations where releases to water of VOCs occur. A sensitivity analysis was developed for investigating the effect of scenario parameters on exposure. Although site-specific data were employed, the exposure of workers was assessed in a model scenario and thus the quantification of risk is associated with uncertainty. Considering that occupational exposure to organic solvents of workers in metal-degreasing facilities may also be significant, risk assessment must be included in the planning of this kind of industrial installation. PMID:17365617

  9. Validation of formability of laminated sheet metal for deep drawing process using GTN damage model

    SciTech Connect

    Lim, Yongbin; Cha, Wan-gi; Kim, Naksoo; Ko, Sangjin

    2013-12-16

    In this study, we studied formability of PET/PVC laminated sheet metal which named VCM (Vinyl Coated Metal). VCM offers various patterns and good-looking metal steel used for appliances such as refrigerator and washing machine. But, this sheet has problems which are crack and peeling of film when the material is formed by deep drawing process. To predict the problems, we used finite element method and GTN (Gurson-Tvergaard-Needleman) damage model to represent damage of material. We divided the VCM into 3 layers (PET film, adhesive and steel added PVC) in finite element analysis model to express the crack and peeling phenomenon. The material properties of each layer are determined by reverse engineering based on tensile test result. Furthermore, we performed the simple rectangular deep drawing and simulated it. The simulation result shows good agreement with drawing experiment result in position, punch stroke of crack occurrence. Also, we studied the fracture mechanism of PET film on VCM by comparing the width direction strain of metal and PET film.

  10. Validation of formability of laminated sheet metal for deep drawing process using GTN damage model

    NASA Astrophysics Data System (ADS)

    Lim, Yongbin; Cha, Wan-gi; Ko, Sangjin; Kim, Naksoo

    2013-12-01

    In this study, we studied formability of PET/PVC laminated sheet metal which named VCM (Vinyl Coated Metal). VCM offers various patterns and good-looking metal steel used for appliances such as refrigerator and washing machine. But, this sheet has problems which are crack and peeling of film when the material is formed by deep drawing process. To predict the problems, we used finite element method and GTN (Gurson-Tvergaard-Needleman) damage model to represent damage of material. We divided the VCM into 3 layers (PET film, adhesive and steel added PVC) in finite element analysis model to express the crack and peeling phenomenon. The material properties of each layer are determined by reverse engineering based on tensile test result. Furthermore, we performed the simple rectangular deep drawing and simulated it. The simulation result shows good agreement with drawing experiment result in position, punch stroke of crack occurrence. Also, we studied the fracture mechanism of PET film on VCM by comparing the width direction strain of metal and PET film.

  11. Metallic tin quantum sheets confined in graphene toward high-efficiency carbon dioxide electroreduction.

    PubMed

    Lei, Fengcai; Liu, Wei; Sun, Yongfu; Xu, Jiaqi; Liu, Katong; Liang, Liang; Yao, Tao; Pan, Bicai; Wei, Shiqiang; Xie, Yi

    2016-01-01

    Ultrathin metal layers can be highly active carbon dioxide electroreduction catalysts, but may also be prone to oxidation. Here we construct a model of graphene confined ultrathin layers of highly reactive metals, taking the synthetic highly reactive tin quantum sheets confined in graphene as an example. The higher electrochemical active area ensures 9 times larger carbon dioxide adsorption capacity relative to bulk tin, while the highly-conductive graphene favours rate-determining electron transfer from carbon dioxide to its radical anion. The lowered tin-tin coordination numbers, revealed by X-ray absorption fine structure spectroscopy, enable tin quantum sheets confined in graphene to efficiently stabilize the carbon dioxide radical anion, verified by 0.13 volts lowered potential of hydroxyl ion adsorption compared with bulk tin. Hence, the tin quantum sheets confined in graphene show enhanced electrocatalytic activity and stability. This work may provide a promising lead for designing efficient and robust catalysts for electrolytic fuel synthesis. PMID:27585984

  12. Trace metal contamination study on scalp hair of occupationally exposed workers

    SciTech Connect

    Ashraf, W.; Jaffar, M. ); Mohammad, D. )

    1994-10-01

    Scalp hair is a metabolic end product that incorporates metals into its structure during the growth process. The levels of trace elements in the hair are considered to be influenced in particular by food, air and occupational exposure, and in general by race, age, sex, metabolism, hygienic condition and geographical location of individuals. Recently, trace metal content of human hair has been explored as a tool for monitoring the impact of environmental pollution on the inhabitants of a community. In this respect, the endogenous and exogenous contents of metals in hair are understood to play important role towards exposure assessment. The exogenous metal content of hair reflects exposure to the occupational, domestic and recreational environments, provided the donor is not suffering from heavy metal poisoning and depressed endogenous levels arising from dietary deficiencies. Keeping this in view, the exogenous and endogenous metal contents of scalp hair of occupationally exposed workers from various workshops were determined in the present study, both in unwashed and washed hair samples to assess the extent of metal contamination. All donors, within the age group of 6-45 years, were full-time workers of various autoworkshops situated in the densely populated and industrialized city of Lahore. ICP atomic emission and atomic absorption spectrophotometric methods were used for determining the levels of five non-essential and three essential elements in the scalp hair. 20 refs., 6 tabs.

  13. Forming Limits in Sheet Metal Forming for Non-Proportional Loading Conditions - Experimental and Theoretical Approach

    SciTech Connect

    Ofenheimer, Aldo; Buchmayr, Bruno; Kolleck, Ralf

    2005-08-05

    The influence of strain paths (loading history) on material formability is well known in sheet forming processes. Sophisticated experimental methods are used to determine the entire shape of strain paths of forming limits for aluminum AA6016-T4 alloy. Forming limits for sheet metal in as-received condition as well as for different pre-deformation are presented. A theoretical approach based on Arrieux's intrinsic Forming Limit Stress Curve (FLSC) concept is employed to numerically predict the influence of loading history on forming severity. The detailed experimental strain paths are used in the theoretical study instead of any linear or bilinear simplified loading histories to demonstrate the predictive quality of forming limits in the state of stress.

  14. Oxygen-induced magnetic properties and metallic behavior of a BN sheet

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Yang, Ping; Xiao, Hai Yan; Gao, Fei

    2010-11-24

    In this paper, ab initio method has been employed to study the adsorption energies, electronic structures and magnetic properties of a BN sheet functionalized by oxygen (O) atom. The adsorption process is typically exothermic, and some unusual properties can be revealed with different adsorption sites. The energy gap of BN sheet narrows due to the strong hybridization between O and BN electronic states when O locates above a BN bond or a nitrogen atom. Upon the adsorption of O above a B3N3 ring or a boron atom, the electrons of O-adsorbed BN system are polarized, which gives rise to the magnetic moment of 2.0 μB. In this case, Fermi level crosses the valence band, resulting the O-adsorbed BN system to be metallic. Furthermore, potential energy curves analysis shows that the magnetism and matellic of BN system can be modulated by the external temperature and pressure.

  15. Respiratory diseases in hard metal workers: an occupational hygiene study in a factory.

    PubMed Central

    Kusaka, Y; Yokoyama, K; Sera, Y; Yamamoto, S; Sone, S; Kyono, H; Shirakawa, T; Goto, S

    1986-01-01

    A hygiene study of a hard metal factory was conducted from 1981 to 1984. All workers exposed to hard metal were medically examined and their exposure to cobalt measured. Eighteen employees had occupational asthma related to exposure to hard metal, a prevalence rate of 5.6%. Nine had a positive bronchial provocation test to cobalt and reactions of the immediate, late, or dual type were elicited. Exposure measurements suggest that asthma may be caused by cobalt at a mean time weighted average concentration below 0.05 mg/m3. Only two of the nine individuals with cobalt asthma had a positive patch test to cobalt. Chest radiographs of three workers showed diffuse shadows of category 1 or over. X ray microanalysis of lung biopsy specimens from two of these three workers showed the presence of tungsten, titanium, cobalt, nickel, and some minerals. One of the two was diagnosed as having pneumoconiosis due to exposure to silica in a steel industry and the other was suspected of having pulmonary fibrosis caused by dust generated from the carborundum wheels used to grind hard metal. There were no cases with interstitial pneumonitis in the factory. Images PMID:3718895

  16. Screening heavy metals levels in hair of sanitation workers by X-ray fluorescence analysis.

    PubMed

    Md Khudzari, Jauharah; Wagiran, Husin; Hossain, I; Ibrahim, Noorddin

    2013-01-01

    This work presents a study of human hair as a bio-indicator for detection of heavy metals as part of environmental health surveillance programs project to develop a subject of interest in the biomedical and environmental sciences. A total of 34 hair samples were analyzed that consisting of 29 samples from sanitation workers and five samples from students. The hair samples were prepared and treated in accordance to the International Atomic Energy Agency (IAEA) recommendations. The concentrations of heavy metals were analyzed using the energy dispersive X-ray fluorescence (EDXRF) technique by X-50 Mobile X-ray Fluorescence (XRF) at Oceanography Institute, Universiti Malaysia Terengganu. The performance of EDXRF analyzer was tested by Standard Reference Material (SRM 2711) Montana Soil which was in good agreement with certified value within 14% deviations except for Hg. While seven heavy metals: Mn, Fe, Ni, Cu, Zn, Se, and Sb were detected in both groups, three additional elements, i.e. As, Hg and Pb, were detected only in sanitation workers group. For sanitation workers group, the mean concentration of six elements, Mn, Fe, Cu, Zn, Se, and Sb, shows elevated concentration as compared to the control samples concentration. Results from both groups were compared and discussed in relation to their respective heavy metals concentrations. PMID:22846873

  17. Urinary neutrophil gelatinase-associated lipocalin is associated with heavy metal exposure in welding workers

    PubMed Central

    Chuang, Kai-Jen; Pan, Chih-Hong; Su, Chien-Ling; Lai, Ching-Huang; Lin, Wen-Yi; Ma, Chih-Ming; Ho, Shu-Chuan; Bien, Mauo-Ying; Chen, Cheng-Hsien; Chuang, Hsiao-Chi

    2015-01-01

    Metals cause nephrotoxicity with acute and/or chronic exposure; however, few epidemiological studies have examined impacts of exposure to metal fumes on renal injury in welding workers. In total, 66 welding workers and 12 office workers were recruited from a shipyard located in southern Taiwan. Urine samples from each subject were collected at the beginning (baseline) and end of the work week (1-week exposure). Personal exposure to PM2.5 was measured. The 8-h mean PM2.5 was 50.3 μg/m3 for welding workers and 27.4 μg/m3 for office workers. iTRAQs coupled with LC-MS/MS were used to discover the pathways in response to welding PM2.5 in the urine, suggesting that extracellular matrix (ECM)-receptor interactions are a critical mechanism. ECM-receptor interaction-related biomarkers for renal injury, kidney injury molecule (KIM)-1 and neutrophil gelatinase-associated lipocalin (NGAL), were significantly elevated in welding workers post-exposure, as well as were urinary Al, Cr, Mn, Fe, Co, and Ni levels. NGAL was more significantly associated with Al (r = 0.737, p < 0.001), Cr (r = 0.705, p < 0.001), Fe (r = 0.709, p < 0.001), and Ni (r = 0.657, p < 0.001) than was KIM-1, suggesting that NGAL may be a urinary biomarker for welding PM2.5 exposure. Nephrotoxicity (e.g., renal tubular injury) may be an emerging concern in occupational health. PMID:26673824

  18. Urinary neutrophil gelatinase-associated lipocalin is associated with heavy metal exposure in welding workers.

    PubMed

    Chuang, Kai-Jen; Pan, Chih-Hong; Su, Chien-Ling; Lai, Ching-Huang; Lin, Wen-Yi; Ma, Chih-Ming; Ho, Shu-Chuan; Bien, Mauo-Ying; Chen, Cheng-Hsien; Chuang, Hsiao-Chi

    2015-01-01

    Metals cause nephrotoxicity with acute and/or chronic exposure; however, few epidemiological studies have examined impacts of exposure to metal fumes on renal injury in welding workers. In total, 66 welding workers and 12 office workers were recruited from a shipyard located in southern Taiwan. Urine samples from each subject were collected at the beginning (baseline) and end of the work week (1-week exposure). Personal exposure to PM2.5 was measured. The 8-h mean PM2.5 was 50.3 μg/m(3) for welding workers and 27.4 μg/m(3) for office workers. iTRAQs coupled with LC-MS/MS were used to discover the pathways in response to welding PM2.5 in the urine, suggesting that extracellular matrix (ECM)-receptor interactions are a critical mechanism. ECM-receptor interaction-related biomarkers for renal injury, kidney injury molecule (KIM)-1 and neutrophil gelatinase-associated lipocalin (NGAL), were significantly elevated in welding workers post-exposure, as well as were urinary Al, Cr, Mn, Fe, Co, and Ni levels. NGAL was more significantly associated with Al (r = 0.737, p < 0.001), Cr (r = 0.705, p < 0.001), Fe (r = 0.709, p < 0.001), and Ni (r = 0.657, p < 0.001) than was KIM-1, suggesting that NGAL may be a urinary biomarker for welding PM2.5 exposure. Nephrotoxicity (e.g., renal tubular injury) may be an emerging concern in occupational health. PMID:26673824

  19. Urinary neutrophil gelatinase-associated lipocalin is associated with heavy metal exposure in welding workers

    NASA Astrophysics Data System (ADS)

    Chuang, Kai-Jen; Pan, Chih-Hong; Su, Chien-Ling; Lai, Ching-Huang; Lin, Wen-Yi; Ma, Chih-Ming; Ho, Shu-Chuan; Bien, Mauo-Ying; Chen, Cheng-Hsien; Chuang, Hsiao-Chi

    2015-12-01

    Metals cause nephrotoxicity with acute and/or chronic exposure; however, few epidemiological studies have examined impacts of exposure to metal fumes on renal injury in welding workers. In total, 66 welding workers and 12 office workers were recruited from a shipyard located in southern Taiwan. Urine samples from each subject were collected at the beginning (baseline) and end of the work week (1-week exposure). Personal exposure to PM2.5 was measured. The 8-h mean PM2.5 was 50.3 μg/m3 for welding workers and 27.4 μg/m3 for office workers. iTRAQs coupled with LC-MS/MS were used to discover the pathways in response to welding PM2.5 in the urine, suggesting that extracellular matrix (ECM)-receptor interactions are a critical mechanism. ECM-receptor interaction-related biomarkers for renal injury, kidney injury molecule (KIM)-1 and neutrophil gelatinase-associated lipocalin (NGAL), were significantly elevated in welding workers post-exposure, as well as were urinary Al, Cr, Mn, Fe, Co, and Ni levels. NGAL was more significantly associated with Al (r = 0.737, p < 0.001), Cr (r = 0.705, p < 0.001), Fe (r = 0.709, p < 0.001), and Ni (r = 0.657, p < 0.001) than was KIM-1, suggesting that NGAL may be a urinary biomarker for welding PM2.5 exposure. Nephrotoxicity (e.g., renal tubular injury) may be an emerging concern in occupational health.

  20. Development of Dynamic Explicit Crystallographic Homogenization Finite Element Analysis Code to Assess Sheet Metal Formability

    NASA Astrophysics Data System (ADS)

    Nakamura, Yasunori; Tam, Nguyen Ngoc; Ohata, Tomiso; Morita, Kiminori; Nakamachi, Eiji

    2004-06-01

    The crystallographic texture evolution induced by plastic deformation in the sheet metal forming process has a great influence on its formability. In the present study, a dynamic explicit finite element (FE) analysis code is newly developed by introducing a crystallographic homogenization method to estimate the polycrystalline sheet metal formability, such as the extreme thinning and "earing." This code can predict the plastic deformation induced texture evolution at the micro scale and the plastic anisotropy at the macro scale, simultaneously. This multi-scale analysis can couple the microscopic crystal plasticity inhomogeneous deformation with the macroscopic continuum deformation. In this homogenization process, the stress at the macro scale is defined by the volume average of those of the corresponding microscopic crystal aggregations in satisfying the equation of motion and compatibility condition in the micro scale "unit cell," where the periodicity of deformation is satisfied. This homogenization algorithm is implemented in the conventional dynamic explicit finite element code by employing the updated Lagrangian formulation and the rate type elastic/viscoplastic constitutive equation. At first, it has been confirmed through a texture evolution analyses in cases of typical deformation modes that Taylor's "constant strain homogenization algorithm" yields extreme concentration toward the preferred crystal orientations compared with our homogenization one. Second, we study the plastic anisotropy effects on "earing" in the hemispherical cup deep drawing process of pure ferrite phase sheet metal. By the comparison of analytical results with those of Taylor's assumption, conclusions are drawn that the present newly developed dynamic explicit crystallographic homogenization FEM shows more reasonable prediction of plastic deformation induced texture evolution and plastic anisotropy at the macro scale.

  1. Effects of Temperature and Forming Speed on Plastic Bending of Adhesively Bonded Sheet Metals

    NASA Astrophysics Data System (ADS)

    Takiguchi, Michihiro; Yoshida, Tetsuya; Yoshida, Fusahito

    This paper deals with the temperature and rate-dependent elasto-viscoplasticity behaviour of a highly ductile acrylic adhesive and its effect on plastic bending of adhesively bonded sheet metals. Tensile lap shear tests of aluminium single-lap joints were performed at various temperature of 10-40°C at several tensile speeds. Based on the experimental results, a new constitutive model of temperature and rate-dependent elasto-viscoplasticity of the adhesive is presented. From V-bending experiments and the corresponding numerical simulation, it was found that the gull-wing bend is suppressed by high-speed forming at a lower temperature.

  2. Control the springback of metal sheets by using an artificial neural network

    NASA Astrophysics Data System (ADS)

    Crina, Axinte

    2007-04-01

    One of the greatest challenges of manufacturing sheet metal parts is to obtain consistent parts dimensions. Springback is the major cause of variations and inconsistencies in the final part geometry. Obtaining a consistent and desirable amount of springback is extremely difficult due to the non-linear effects and interactions of process and material parameters. In this work, the ability of an artificial neural network model to predict optimum process parameters and tools geometry which allow to obtain minimum amount of springback is tested, in the case of a cylindrical deep-drawing process.

  3. Control of Springback in Sheet Metal U-bending Through Design Experiment

    SciTech Connect

    Chirita, Bogdan; Brabie, Gheorghe

    2007-05-17

    For the U-bending of sheet metals, springback represents the most important failure mode that is affecting the parts. The purpose of this study was to develop a method for the reduction or the elimination of springback from the designing stage of the forming process. This paper describes a numerical procedure that combines simulation of springback by finite element method with a fractional factorial design and proposes the optimization of the forming parameters and tools geometry for the reduction of springback intensity. At the end of the study we were able to obtain an important improvement of part precision using the parameters predicted by the factorial design.

  4. European Bronze Age Sheet Metal Objects: 3,000 Years of High-Level Bronze Manufacture

    NASA Astrophysics Data System (ADS)

    Mödlinger, Marianne; El Morr, Ziad

    2014-01-01

    This article focuses on the manufacture and usage of selected sheet metal objects from helmets, a vessel, and two shields from the European Bronze Age and Early Iron Age, which date from the thirteenth to seventh centuries BC. Manufacturing traces on the surface, as well as metallographic investigations and the analyses of the alloy composition with scanning electron microscope-energy-dispersive x-ray spectroscopy, provided an insight into the manufacturing techniques and the production of valuable, high-status objects, and highlighted the potential changes in manufacturing techniques and alloys used during different time periods.

  5. Analysis of hot forming of a sheet metal component made of advanced high strength steel

    NASA Astrophysics Data System (ADS)

    Demirkaya, Sinem; Darendeliler, Haluk; Gökler, Mustafa İlhan; Ayhaner, Murat

    2013-05-01

    To provide reduction in weight while maintaining crashworthiness and to decrease the fuel consumption of vehicles, thinner components made of Advanced High Strength Steels (AHSS) are being increasingly used in automotive industry. However, AHSS cannot be formed easily at the room temperature (i.e. cold forming). The alternative process involves heating, hot forming and subsequent quenching. A-pillar upper reinforcement of a vehicle is currently being produced by cold forming of DP600 steel sheet with a thickness of 1.8 mm. In this study, the possible decrease in the thickness of this particular part by using 22MnB5 as appropriate AHSS material and applying this alternative process has been studied. The proposed process involves deep drawing, trimming, heating, sizing, cooling and piercing operations. Both the current production process and the proposed process are analyzed by the finite element method. The die geometry, blank holding forces and the design of the cooling channels for the cooling process are determined numerically. It is shown that the particular part made of 22MnB5 steel sheet with a thickness of 1.2 mm can be successfully produced by applying the proposed process sequence and can be used without sacrificing the crashworthiness. With the use of the 22MnB5 steel with a thickness of 1.2 mm instead of DP600 sheet metal with a thickness of 1.8 mm, the weight is reduced by approximately 33%.

  6. Thin Porous Metal Sheet-Supported NaA Zeolite Membrane for Water/Ethanol Separation

    SciTech Connect

    Zhang, Jian; Liu, Wei

    2011-04-01

    This paper reports preparation and separation testing results of water-selective zeolite membrane, such as NaA (or 4A-type), supported on a robust, porous metal sheet of 50um thickness. The thin sheet support is of large potential for development of a low-cost, inorganic membrane module of high surface area packing density. The porous Ni alloy sheet of micrometer or sub-micrometer mean pore size, which was prepared by a proprietary process, is used to evaluate different zeolite membrane deposition methods and conditions. The membranes are characterized by SEM, XRD and water/ethanol separation tests. Quality NaA zeolite membrane at thickness <2um is obtained with the secondary hydrothermal growth method. This membrane shows water/ethanol separation factor of >10,000 and water permeation flux of about 4 kg/(m2•h) at 75ºC with a feed of 10wt% water in ethanol. The membrane is also demonstrated with good stability in 66-hour continuous testing at 75ºC and 90ºC.

  7. First-principles study of electronic and magnetic properties of transition metal adsorbed h-BNC2 sheets.

    PubMed

    Srivastava, Pooja; Deshpande, Mrinalini; Sen, Prasenjit

    2011-12-28

    Adsorption of Fe, Co and Ni atoms on a hybrid hexagonal sheet of graphene and boron nitride is studied using density functional methods. Most favorable adsorption sites for these adatoms are identified for different widths of the graphene and boron nitride regions. Electronic structure and magnetic properties of the TM-adsorbed sheets are then studied in detail. The TM atoms change the electronic structure of the sheet significantly, and the resulting system can be a magnetic semiconductor, semi-metal, or a non-magnetic semiconductor depending on the TM chosen. This gives tunability of properties which can be useful in novel electronics applications. Finally, barriers for diffusion of the adatoms on the sheet are calculated, and their tendency to agglomerate on the sheet is estimated. PMID:22068843

  8. 75 FR 65523 - Dawson Metal Company, Inc., Industrial Division, Jamestown, NY; Notice of Negative Determination...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-25

    ... on February 16, 2010 (75 FR 7030). The workers are engaged in employment related to precision sheet... Employment and Training Administration Dawson Metal Company, Inc., Industrial Division, Jamestown, NY; Notice... for workers and former workers of Dawson Metal Company, Inc., Industrial Division, Jamestown, New...

  9. Evidencing the existence of exciting half-metallicity in two-dimensional TiCl3 and VCl3 sheets

    PubMed Central

    Zhou, Yungang; Lu, Haifeng; Zu, Xiaotao; Gao, Fei

    2016-01-01

    Half-metallicity combined with wide half-metallic gap, unique ferromagnetic character and high Curie temperature has become a key driving force to develop next-generation spintronic devices. In previous studies, such half-metallicity always occurred under certain manipulation. Here, we, via examining a series of two-dimensional transition-metal trichlorides, evidenced that TiCl3 and VCl3 sheets could display exciting half-metallicity without involving any external modification. Calculated half-metallic band-gaps for TiCl3 and VCl3 sheets are about 0.60 and 1.10 eV, respectively. Magnetic coupled calculation shows that both sheets favor the ferromagnetic order with a substantial collective character. Estimated Curie temperatures can be up to 376 and 425 K for TiCl3 and VCl3 sheets, respectively. All of these results successfully disclose two new promising two-dimensional half-metallic materials toward the application of next-generation paper-like spintronic devices. PMID:26776358

  10. Evidencing the existence of exciting half-metallicity in two-dimensional TiCl3 and VCl3 sheets.

    PubMed

    Zhou, Yungang; Lu, Haifeng; Zu, Xiaotao; Gao, Fei

    2016-01-01

    Half-metallicity combined with wide half-metallic gap, unique ferromagnetic character and high Curie temperature has become a key driving force to develop next-generation spintronic devices. In previous studies, such half-metallicity always occurred under certain manipulation. Here, we, via examining a series of two-dimensional transition-metal trichlorides, evidenced that TiCl3 and VCl3 sheets could display exciting half-metallicity without involving any external modification. Calculated half-metallic band-gaps for TiCl3 and VCl3 sheets are about 0.60 and 1.10 eV, respectively. Magnetic coupled calculation shows that both sheets favor the ferromagnetic order with a substantial collective character. Estimated Curie temperatures can be up to 376 and 425 K for TiCl3 and VCl3 sheets, respectively. All of these results successfully disclose two new promising two-dimensional half-metallic materials toward the application of next-generation paper-like spintronic devices. PMID:26776358

  11. Simulation and measurement of melting effects on metal sheets caused by direct lightning strikes

    NASA Technical Reports Server (NTRS)

    Kern, Alexander

    1991-01-01

    Direct lightning strikes melt metal parts of various systems, like fuel and propellant tanks of rockets and airplanes, at the point of strike. Responsible for this melting are the impulse current and, if occurring, the long duration current, both carrying a remarkable charge Q. For studying these meltings the simulation in the laboratory has to be based on the parameters of natural lightnings. International standards exist defining certain threat levels of natural lightnings and giving possible generator circuits for the simulation. The melting caused by both types of lightning currents show different appearance. Their characteristics, their differences in melting and heating of metal sheets are investigated. Nevertheless the simulation of lightning in the laboratory is imperfect. While natural lightning is a discharge without a counter electrode, the simulation always demands a close counter electrode. The influence of this counter electrode is studied.

  12. Musculoskeletal problems and fluoride exposure: A cross-sectional study among metal smelting workers.

    PubMed

    Saha, A; Mukherjee, A K; Ravichandran, B

    2016-09-01

    Frequent and repetitive activities in job and awkward postures are shown as major contributors of musculoskeletal problems in most of the occupational health studies; however, efforts to explore newer risk factor are important to plan interventional measures. In this backdrop, this study examined contribution of fluoride exposure to musculoskeletal complaints. A cross-sectional interviewer-administered questionnaire survey was conducted involving 180 randomly selected subjects from a metal smelting industry. Clinical examination of the subjects was also performed to assess their health status and morbidity details. Assessment of personal exposure to particulate and gaseous fluoride at workplace was conducted. Urinary fluoride level was also examined in post-shift samples collected from study subjects. The mean age of the study subjects was 39.1 (±6.7) years. Majority of the workers (42.5%) were engaged in pot room. About 54% workers were suffering from backache and 66% subjects had joint pain. Exposure of workers to both particulate and gaseous fluoride and post-working shift urinary fluoride level was significantly higher in pot-room workers in comparison with all other workers. It was observed that age (odds ratio (OR): 1.62; 95% confidence interval (CI): 1.18-2.34), drinking untreated water (OR: 1.51; 95% CI: 1.03-2.76), working in pot room (OR: 1.44; 95% CI: 1.13-1.91) and urinary fluoride level (OR: 2.71; 95% CI: 1.81-3.75) had significant effects on musculoskeletal complaints. This study concludes that along with other predictors such as nature of work, posture at work and age of worker, exposure to fluoride also has significant role in the occurrence of musculoskeletal morbidity. PMID:25653036

  13. Personal exposures to airborne metals in London taxi drivers and office workers in 1995 and 1996.

    PubMed

    Pfeifer, G D; Harrison, R M; Lynam, D R

    1999-09-01

    In 1995, a petroleum marketer introduced a diesel fuel additive in the UK containing Mn as MMT (methylcyclopentadienyl manganese tricarbonyl). A small study of personal exposures to airborne Mn in London was conducted before and after introduction of the additive to identify any major impact of the additive on exposures. In 1995, personal exposures to Mn were measured in two groups, taxi drivers and office workers (10 subjects per group) for two consecutive 7-day periods. A similar study was carried out in 1996 to determine if exposures had changed. Samples were also analyzed for Ca, Al, Mg and Pb. In 1996, exposures to aerosol mass as total suspended particulates (TSP) and PM2.5 were measured in addition to the metals. Manganese exposures in this cohort did not increase as a result of introduction of the additive. However, a significant source of Mn exposure was discovered during the conduct of these tests. The mean exposure to Mn was higher among the office workers in both years than that of the taxi drivers. This was due to the fact that approximately half of the office workers commuted via the underground railway system where airborne dust and metal concentrations are significantly elevated over those in the general environment. Similar results have been noted in other cities having underground rail systems. Exposure to Mn, Pb, Ca, and Mg were not significantly different between the 2 years. Taxi drivers had higher exposures than office workers to Mg and Pb in both years. Commuting via the underground also had a significant impact on exposures to TSP, PM2.5, Al, and Ca, but had little effect on exposures to Mg. The aerosol in the underground was particularly enriched in Mn, approximately 10-fold, when compared to the aerosol in the general environment. There are several possible sources for this Mn, including mechanical wear of the steel wheels on the steel rais, vaporization of metal from sparking of the third rail, or brake wear. PMID:10535124

  14. Characterization of the Bauschinger effect in sheet metal undergoing large strain reversals in bending

    NASA Astrophysics Data System (ADS)

    Hanzon, Drew Wyatt

    This work consists on the quantification of sheet metal uniaxial stress-strain reversals from pure bending tests. Bending strains to approximately 10% were measured by strain gages and interferometry. Bending-unbending moments and strains were modeled and compared closely to the experimental data. The reverse uniaxial stress-strains curves were determined from the optimal fit of the model. Bauschinger effects were described by the reverse uniaxial response at the elasto-plastic range, between the elastic and the large strain, power fit ranges. Arc and straight line fittings on the lnsigma-lnepsilon scale proved accurate to describe the elasto-plastic behavior. Reverse uniaxial data determined for DP590 and DP780 steels and two Aluminum alloys showed significant Bauschinger effects with distinct features. For the DP steels the magnitudes of the reverse compressive sigma-epsilon curves compared moderately higher, and merging to a power curve with parameters K, n previously defined by tension testing. Bauschinger effects at small reversed strains were less pronounced for the aluminum alloys. However, at higher strains the reverse elasto-plastic response softened considerably, and during the unbending span the magnitudes of the reverse compressive strains remained below the corresponding K, n tensile values. The results showed pure bending as an efficient, simple to use technique to generate sigma-epsilon data for sheet metal at large reverse strains without the complicating restraining hardware required by direct compression methods.

  15. Method of manufacturing metallic products such as sheet by cold working and flash annealing

    DOEpatents

    Hajaligol, Mohammad R.; Sikka, Vinod K.

    2000-01-01

    A metallic alloy composition is manufactured into products such as press formed or stamped products or rolled products such as sheet, strip, rod, wire or band by one or more cold working steps with intermediate or final flash annealing. The method can include cold rolling an iron, nickel or titanium aluminide alloy and annealing the cold worked product in a furnace by infrared heating. The flash annealing is preferably carried out by rapidly heating the cold worked product to an elevated temperature for less than one minute. The flash annealing is effective to reduce surface hardness of the cold worked product sufficiently to allow further cold working. The product to be cold worked can be prepared by casting the alloy or by a powder metallurgical technique such as tape casting a mixture of metal powder and a binder, roll compacting a mixture of the powder and a binder or plasma spraying the powder onto a substrate. In the case of tape casting or roll compaction, the initial powder product can be heated to a temperature sufficient to remove volatile components. The method can be used to form a cold rolled sheet which is formed into an electrical resistance heating element capable of heating to 900.degree. C. in less than 1 second when a voltage up to 10 volts and up to 6 amps is passed through the heating element.

  16. Method of manufacturing metallic products such as sheet by cold working and flash anealing

    DOEpatents

    Hajaligol, Mohammad R.; Sikka, Vinod K.

    2001-01-01

    A metallic alloy composition is manufactured into products such as press formed or stamped products or rolled products such as sheet, strip, rod, wire or band by one or more cold working steps with intermediate or final flash annealing. The method can include cold rolling an iron, nickel or titanium aluminide alloy and annealing the cold worked product in a furnace by infrared heating. The flash annealing is preferably carried out by rapidly heating the cold worked product to an elevated temperature for less than one minute. The flash annealing is effective to reduce surface hardness of the cold worked product sufficiently to allow further cold working. The product to be cold worked can be prepared by casting the alloy or by a powder metallurgical technique such as tape casting a mixture of metal powder and a binder, roll compacting a mixture of the powder and a binder or plasma spraying the powder onto a substrate. In the case of tape casting or roll compaction, the initial powder product can be heated to a temperature sufficient to remove volatile components. The method can be used to form a cold rolled sheet which is formed into an electrical resistance heating element capable of heating to 900.degree. C. in less than 1 second when a voltage up to 10 volts and up to 6 amps is passed through the heating element.

  17. Tunable color parallel tandem organic light emitting devices with carbon nanotube and metallic sheet interlayers

    SciTech Connect

    Oliva, Jorge; Desirena, Haggeo; De la Rosa, Elder; Papadimitratos, Alexios; Zakhidov, Anvar A.

    2015-11-21

    Parallel tandem organic light emitting devices (OLEDs) were fabricated with transparent multiwall carbon nanotube sheets (MWCNT) and thin metal films (Al, Ag) as interlayers. In parallel monolithic tandem architecture, the MWCNT (or metallic films) interlayers are an active electrode which injects similar charges into subunits. In the case of parallel tandems with common anode (C.A.) of this study, holes are injected into top and bottom subunits from the common interlayer electrode; whereas in the configuration of common cathode (C.C.), electrons are injected into the top and bottom subunits. Both subunits of the tandem can thus be monolithically connected functionally in an active structure in which each subunit can be electrically addressed separately. Our tandem OLEDs have a polymer as emitter in the bottom subunit and a small molecule emitter in the top subunit. We also compared the performance of the parallel tandem with that of in series and the additional advantages of the parallel architecture over the in-series were: tunable chromaticity, lower voltage operation, and higher brightness. Finally, we demonstrate that processing of the MWCNT sheets as a common anode in parallel tandems is an easy and low cost process, since their integration as electrodes in OLEDs is achieved by simple dry lamination process.

  18. Fully Integrated EAS-Based Solid-Shell Finite Elements in Implicit Sheet Metal Forming Simulations

    SciTech Connect

    Valente, R.A. Fontes; Cardoso, R.P.R.; Alves de Sousa, R.J.; Parente, M.P.L.; Jorge, R.M. Natal

    2005-08-05

    In this communication sheet metal forming problems are analyzed with the Finite Element Method and a fully-integrated solid-shell element, based on the Enhanced Assumed Strain (EAS) method. Among the solid-shell element's distinguish features, it should be mentioned the solely use of the EAS approach in dealing with either transverse and volumetric-based locking pathologies, thus avoiding the inclusion of other mixed methods into the formulation. The adopted methodology is then able to successfully deal with small thickness shell problems within the incompressible range, aspects commonly appearing in sheet metal forming modeling with solid elements.Simulations of this type of forming processes are mainly solved resorting to membrane and shell-type finite elements, included in explicit commercial programs. Nevertheless, the presented solid-shell formulation, within a fully implicit approach, provides reliable solutions when compared to experimental results. It is also worth mentioning that the present solid-shell formulation encompasses a minimum set of enhancing strain variables, if compared to other fully integrated hexahedral finite elements in the literature.In order to assess the performance of the presented formulation, the S-Rail Forming problem of an aluminum alloy is described and analyzed, with the results being compared to experimental and numerical simulation data.

  19. Tunable color parallel tandem organic light emitting devices with carbon nanotube and metallic sheet interlayers

    NASA Astrophysics Data System (ADS)

    Oliva, Jorge; Papadimitratos, Alexios; Desirena, Haggeo; De la Rosa, Elder; Zakhidov, Anvar A.

    2015-11-01

    Parallel tandem organic light emitting devices (OLEDs) were fabricated with transparent multiwall carbon nanotube sheets (MWCNT) and thin metal films (Al, Ag) as interlayers. In parallel monolithic tandem architecture, the MWCNT (or metallic films) interlayers are an active electrode which injects similar charges into subunits. In the case of parallel tandems with common anode (C.A.) of this study, holes are injected into top and bottom subunits from the common interlayer electrode; whereas in the configuration of common cathode (C.C.), electrons are injected into the top and bottom subunits. Both subunits of the tandem can thus be monolithically connected functionally in an active structure in which each subunit can be electrically addressed separately. Our tandem OLEDs have a polymer as emitter in the bottom subunit and a small molecule emitter in the top subunit. We also compared the performance of the parallel tandem with that of in series and the additional advantages of the parallel architecture over the in-series were: tunable chromaticity, lower voltage operation, and higher brightness. Finally, we demonstrate that processing of the MWCNT sheets as a common anode in parallel tandems is an easy and low cost process, since their integration as electrodes in OLEDs is achieved by simple dry lamination process.

  20. Surrogate POD models for building forming limit diagrams of parameterized sheet metal forming applications

    NASA Astrophysics Data System (ADS)

    Hamdaoui, M.; Le Quilliec, Guénhaël; Breitkopf, Piotr; Villon, Pierre

    2013-05-01

    The aim of this work is to present a surrogate POD (Proper Orthogonal Decomposition) approach for building forming limit diagrams at minimum cost for parameterized sheet metal formed work-pieces. First, a Latin Hypercube Sampling is performed on the design parameter space. Then, at each design site, displacement fields are computed using the popular open-source finite element software Code_Aster. Then, the method of snapshots is used for POD mode determination. POD coefficients are interpolated using kriging. Furthermore, an error analysis of the surrogate POD model is performed on a validation set. It is shown that on the considered use case the accuracy of the surrogate POD model is excellent for the representation of finite element displacement fields. The validated surrogate POD model is then used to build forming limit diagrams (FLD) for any design parameter to assess the quality of stamped metal sheets. Using the surrogate POD model, the Green-Lagrange strain tensor is derived, then major and minor principal deformations are determined at Gauss points for each mesh element. Furthermore, a signed distance between the forming limit curve in rupture and the obtained cloud of points in the plane (ɛ2, ɛ1) is computed to assess the quality of the formed workpiece. The minimization of this signed distance allows determining the safest design for the chosen use case.

  1. Explosive Welding of Aluminum, Titanium and Zirconium to Copper Sheet Metal

    NASA Technical Reports Server (NTRS)

    Hegazy, A. A.; Mote, J. D.

    1985-01-01

    The main material properties affecting the explosive weldability of a certain metal combination are the yield strength, the ductility, the density and the sonic velocity of the two metals. Successful welding of the metal combination depends mainly on the correct choice of the explosive welding parameters; i.e., the stand off distance, the weight of the explosive charge relative to the weight of the flyer plate and the detonation velocity of the explosive. Based on the measured and the handbook values of the properties of interest, the explosive welding parameters were calculated and the arrangements for the explosive welding of the Al alloy 6061-T6, titanium and zirconium to OFHC copper were determined. The relatively small sheet metal thickness (1/8") and the fact that the thickness of the explosive layer must exceed a certain minimum value were considered during the determination of the explosive welding conditions. The results of the metallographic investigations and the measurements of the shear strength at the interface demonstrate the usefulness of these calculations to minimize the number of experimental trials.

  2. Unexpected band structure and half-metal in non-metal-doped arsenene sheet

    NASA Astrophysics Data System (ADS)

    Wang, Ya-ping; Zhang, Chang-wen; Ji, Wei-xiao; Wang, Pei-ji

    2015-06-01

    We performed a first-principles study on two-dimensional (2D) arsenene doped with non-magnetic elements. It was found that dopants (groups III, V, and VII) with odd numbers of valence electrons maintained the semiconducting character of the pristine system, while those (groups IV and VI) with even numbers of valence electrons caused the metallic character to change. Remarkably, the C- and O-doped systems were spin-polarized and could be modulated into half-metals by the external electric field. Our findings reveal a potential method of engineering buckled arsenene for applications in nanoelectronics.

  3. Heavy Metals Exposure and Hygienic Behaviors of Workers in Sanitary Landfill Areas in Southern Thailand

    PubMed Central

    Decharat, Somsiri

    2016-01-01

    Objectives. The main objective of this study was to assess the cadmium and lead exposure levels in subject workers that work in sanitary landfill areas in southern Thailand. The study evaluated the blood cadmium and lead levels in terms of their possible role in worker contamination and transfer of cadmium and lead to the body. Materials and Methods. A cross-sectional study was conducted with 114 subjects. Whole blood samples were collected to determine cadmium and lead levels by graphite furnaces atomic absorption spectrometer chromium analyzer. Results and Discussion. The mean blood cadmium levels and blood lead levels of subjects workers were 2.95 ± 0.58 μg/L (range 1.58–7.03 μg/L) and 8.58 ± 2.58 μg/dL (range 1.98–11.12 μg/dL), respectively. Gender, income, smoked cigarettes, work position, duration of work, personal protective equipment (PPE), and personal hygiene were significantly associated with blood cadmium level and blood lead levels (p < 0.001 and p < 0.001). A multiple regression model was constructed. Significant predictors of blood cadmium levels and blood lead levels included smoked cigarettes, hours worked per day, days worked per week, duration of work (years), work position, use of PPE (mask and gloves), and personal hygiene behavior (ate snacks or drank water at work and washed hands before lunch). Conclusion. The elevated body burden of toxic metals in the solid waste exposure of subject workers is an indication of occupational metal toxicity associated with personal hygiene practices. PMID:27313961

  4. Numerical Determination of Sheet Metal Formability under Simultaneous Stretching and Bending

    NASA Astrophysics Data System (ADS)

    Martinezhyphen; Lopez, A.; van den Boogaard, A. H.

    2011-01-01

    The plastic behavior of AHSS is still far from being completely understood, and its prediction is of large importance in reliability of forming simulation in present automotive industry [1]. Conventional techniques have been proven to be not accurate enough, and underestimate the formability limits for AHSS materials in cases where stretching and bending are combined. In order to satisfy industrial requirements more work need to be done to understand the formability behavior of sheet metal, and special attention needs to be directed to the possible reasons of the lower predicted formability limits. In previous work [2], experimental results for different materials confirmed the positive effect of bending in terms of formability, and demonstrated the influence of curvature on the FLC is especially clear in the plane strain region. Using conventionally determined FLC could lead to not optimal material consumption during sheet forming operations. For this reason, in this study 3D Finite Element simulations were developed using the commercial code ABAQUS/Standard to investigate further the effect of the out of plane stress, and punch radii for the FLC determination. Also the investigation of the influence of different lubrication systems was accomplished.

  5. Tool path influence on electric pulse aided deformation during incremental sheet metal forming

    SciTech Connect

    Asgar, J.; Lingam, R. Reddy, V. N.

    2013-12-16

    Titanium and its alloys are difficult to form at room temperature due to their high flow stress. Super plastic deformation of Ti alloys involves low strain rate forming at very high temperatures which need special tooling which can withstand high temperatures. It was observed that when high current density electric pulse is applied during deformation it reduces the flow stress through electron-dislocation interaction. This phenomenon is known as electro-plasticity. In the present work, importance of tool configuration to enhance the formability without much resistive heating is demonstrated for Incremental Sheet Metal Forming (ISMF). Tool configuration is selected to minimize the current carrying zone in DC pulse aided incremental forming to enhance the formability due to electro plasticity and the same is demonstrated by forming two pyramid shaped components of 30° and 45° wall angles using a Titanium alloy sheet of 0.6 mm thickness. Load measurement indicated that a critical current density is essential for the electro-plasticity to be effective and the same is realized with the load and temperature measurements.

  6. Development of JSTAMP-Works/NV and HYSTAMP for Multipurpose Multistage Sheet Metal Forming Simulation

    NASA Astrophysics Data System (ADS)

    Umezu, Yasuyoshi; Watanabe, Yuko; Ma, Ninshu

    2005-08-01

    Since 1996, Japan Research Institute Limited (JRI) has been providing a sheet metal forming simulation system called JSTAMP-Works packaged the FEM solvers of LS-DYNA and JOH/NIKE, which might be the first multistage system at that time and has been enjoying good reputation among users in Japan. To match the recent needs, "faster, more accurate and easier", of process designers and CAE engineers, a new metal forming simulation system JSTAMP-Works/NV is developed. The JSTAMP-Works/NV packaged the automatic healing function of CAD and had much more new capabilities such as prediction of 3D trimming lines for flanging or hemming, remote control of solver execution for multi-stage forming processes and shape evaluation between FEM and CAD. On the other way, a multi-stage multi-purpose inverse FEM solver HYSTAMP is developed and will be soon put into market, which is approved to be very fast, quite accurate and robust. Lastly, authors will give some application examples of user defined ductile damage subroutine in LS-DYNA for the estimation of material failure and springback in metal forming simulation.

  7. Waste minimization assessment for a manufacturer of iron castings and fabricated sheet metal parts

    SciTech Connect

    Fleischman, M.; Harris, J.J.; Handmaker, A.; Looby, G.P.

    1995-08-01

    The U.S. Environmental Protection Agency (EPA) has funded a pilot project to assist small and medium-size manufacturers who want to minimize their generation of waste but who lack the expertise to do so. Waste Minimization Assessment Centers (WMACs) were established at selected universities and procedures were adapted from the EPA Waste Minimization Opportunity Assessment Manual. That document has been superseded by the Facility Pollution Prevention Guide. The WMAC team at the University of Louisville performed an assessment at a plant that manufactures iron castings and fabricated sheet metal parts. Foundry operations include mixing and mold formation, core making, metal pouring, shakeout, finishing, and painting. Cutting, shaping, and welding are the principal metal fabrication operations. The team`s report, detailing findings and recommendations indicated that paint-related wastes are generated in large quantities, and that significant waste reduction and cost savings could be realized by installing a dry powder coating system or by replacing conventional air spray paint guns with high-volume low-pressure spray guns. This research brief was developed by the principal investigators and EPA`s National Risk Management Research Laboratory, Cincinnati, OH, to announce key findings of an ongoing research project that is fully documented in a separate report of the same title available from University City Science Center.

  8. A quantitative assessment of risks of heavy metal residues in laundered shop towels and their use by workers.

    PubMed

    Connor, Kevin; Magee, Brian

    2014-10-01

    This paper presents a risk assessment of exposure to metal residues in laundered shop towels by workers. The concentrations of 27 metals measured in a synthetic sweat leachate were used to estimate the releasable quantity of metals which could be transferred to workers' skin. Worker exposure was evaluated quantitatively with an exposure model that focused on towel-to-hand transfer and subsequent hand-to-food or -mouth transfers. The exposure model was based on conservative, but reasonable assumptions regarding towel use and default exposure factor values from the published literature or regulatory guidance. Transfer coefficients were derived from studies representative of the exposures to towel users. Contact frequencies were based on assumed high-end use of shop towels, but constrained by a theoretical maximum dermal loading. The risk estimates for workers developed for all metals were below applicable regulatory risk benchmarks. The risk assessment for lead utilized the Adult Lead Model and concluded that predicted lead intakes do not constitute a significant health hazard based on potential worker exposures. Uncertainties are discussed in relation to the overall confidence in the exposure estimates developed for each exposure pathway and the likelihood that the exposure model is under- or overestimating worker exposures and risk. PMID:24973502

  9. Modeling and FE Simulation of Quenchable High Strength Steels Sheet Metal Hot Forming Process

    NASA Astrophysics Data System (ADS)

    Liu, Hongsheng; Bao, Jun; Xing, Zhongwen; Zhang, Dejin; Song, Baoyu; Lei, Chengxi

    2011-08-01

    High strength steel (HSS) sheet metal hot forming process is investigated by means of numerical simulations. With regard to a reliable numerical process design, the knowledge of the thermal and thermo-mechanical properties is essential. In this article, tensile tests are performed to examine the flow stress of the material HSS 22MnB5 at different strains, strain rates, and temperatures. Constitutive model based on phenomenological approach is developed to describe the thermo-mechanical properties of the material 22MnB5 by fitting the experimental data. A 2D coupled thermo-mechanical finite element (FE) model is developed to simulate the HSS sheet metal hot forming process for U-channel part. The ABAQUS/explicit model is used conduct the hot forming stage simulations, and ABAQUS/implicit model is used for accurately predicting the springback which happens at the end of hot forming stage. Material modeling and FE numerical simulations are carried out to investigate the effect of the processing parameters on the hot forming process. The processing parameters have significant influence on the microstructure of U-channel part. The springback after hot forming stage is the main factor impairing the shape precision of hot-formed part. The mechanism of springback is advanced and verified through numerical simulations and tensile loading-unloading tests. Creep strain is found in the tensile loading-unloading test under isothermal condition and has a distinct effect on springback. According to the numerical and experimental results, it can be concluded that springback is mainly caused by different cooling rats and the nonhomogengeous shrink of material during hot forming process, the creep strain is the main factor influencing the amount of the springback.

  10. A three-dimensional porous metal-organic framework constructed from two-dimensional sheets via interdigitation exhibiting dynamic features.

    SciTech Connect

    Ma, S.; Sun, D.; Forster, P. M.; Yuan, D.; Zhuang, W.; Chen, Y. S.; Parise, J. B.; Zhou, H. C.

    2009-04-23

    A three-dimensional porous metal-organic framework (PCN-18) was constructed through interdigitating two-dimensional grid sheets composed of 4,4{prime}-(anthracene-9,10-diyl)dibenzoate and copper paddlewheel secondary building units, and its dynamic features were evidenced by gas sorption isotherms.

  11. Calculation of electromagnetic force in electromagnetic forming process of metal sheet

    NASA Astrophysics Data System (ADS)

    Xu, Da; Liu, Xuesong; Fang, Kun; Fang, Hongyuan

    2010-06-01

    Electromagnetic forming (EMF) is a forming process that relies on the inductive electromagnetic force to deform metallic workpiece at high speed. Calculation of the electromagnetic force is essential to understand the EMF process. However, accurate calculation requires complex numerical solution, in which the coupling between the electromagnetic process and the deformation of workpiece needs be considered. In this paper, an appropriate formula has been developed to calculate the electromagnetic force in metal work-piece in the sheet EMF process. The effects of the geometric size of coil, the material properties, and the parameters of discharge circuit on electromagnetic force are taken into consideration. Through the formula, the electromagnetic force at different time and in different positions of the workpiece can be predicted. The calculated electromagnetic force and magnetic field are in good agreement with the numerical and experimental results. The accurate prediction of the electromagnetic force provides an insight into the physical process of the EMF and a powerful tool to design optimum EMF systems.

  12. Oxidative damage of workers in secondary metal recovery plants affected by smoking status and joining the smelting work.

    PubMed

    Chia, Taipau; Hsu, Ching Yi; Chen, Hsiu Ling

    2008-04-01

    In Taiwan, secondary copper smelters and zinc recovery plants primarily utilize recovering metal from scrap and dross, and handles mostly fly ash and slag with high temperature to produce ZnO from the iron and steel industry. The materials may contain organic impurities, such as plastic and organic chloride chemicals, and amounts of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are produced during the smelting process. Therefore, secondary metal recovery industries are major emission sources of PCDD/Fs, which may have been demonstrated to elicit oxidative stress and to involve the production of plasma malondialdehyde (MDA). Many studies have also indicated that the intake of antioxidants, smoking, age and exposure to environmental pollutants may be implicated to DNA damage or lipid peroxidation. This study therefore aims to elucidate the roles of occupational exposure like joining the smelting work, age, smoking and alcohol status, and antioxidant intake on oxidative damage in secondary metal recovery workers in Taiwan. 73 workers were recruited from 2 secondary metal recovery plants. The analysis of 8-hydroxydeoxyguanosine (8-OH-dG) in urine, DNA strand breakage (comet assay) and lipid peroxidation (MDA) in blood samples were completed for all of the workers. The results showed that the older subjects exhibited significantly lower levels of 8-OH-dG and MDA than younger subjects. Our investigation also showed that working departments were in related to plasma MDA and DNA strand breakage levels of nonsmokers, however, the observation become negligible in smokers. And it is implicated that cigarette type might affect 8-OH-dG levels in secondary metal recovery workers. Since, adding to results above, the MDA level in production workers was significantly higher than those in managerial departments, it is important for the employers to make efforts on improving occupational environments or serving protective equipments to protect workers

  13. Laser-Assisted Sheet Metal Working by the Integration of Scanner System Technology into a Progressive Die

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    Within the sheet metal working industry the demand for thinner sheet materials with very high strength is growing due to the increasing importance for saving energy and responsible usage of natural resources. High strength and low ductility restrict application of state-of-the-art technology to shear, bend or deep draw parts with the needed complexity and quality. The Fraunhofer IPT has developed a "hy-PRESS" system to combine laser-assisted preheating and conventional punching to a hybrid technology in a progressive die, which allows to shear, bend and deep draw high strength materials with a high quality and complexity in progressive dies.

  14. Control of sheet-metal forming processes with piezoactuators in smart structures

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Hoffmann, Michael; Roscher, Hans-Jürgen; Scheffler, Sören; Wolf, Klaus

    2006-03-01

    The most important project in sheet metal forming is streamlining the material flow since each rejects increases production costs. Using the multipoint cushion device together with an elastic blankholder makes it possible to actively manipulate the material flow in the flange range. This allows major enhancements in the deformation ratio, especially with the novel high strength materials in car body production. State-of-the-art is multiple draw pins to initiate the force on selected points on the blankholder. Admittedly, the cushion plate does not allow optimum force allocation because it is situated between hydraulic pressure rollers and draw pins. Replacing selected draw pins with piezoactuators for generating high forces allows systematic control of the force progression at critical forming areas during sheet draw-in. The system, consisting of the piezostack actuator, dynamometer and components for force initiation, was built as a compact unit with low resilience with the intension of using the inherent sensory properties of the piezostack actuator to measure force. Applying this principle throughout allows a reduction of hydraulic components which eventually lead to a less expensive one- point cushion device. Initial finding have already been arrived at in the context of a research project at the Fraunhofer Institute for Machine Tools and Forming Technology in Chemnitz, Germany in cooperation with a partner from the automobile industry. A draw pin was replaced ad hoc with a highly durable piezoactuator integrated in a force control cycle. The force progression during the sheet draw-in could be accurately adjusted according to a predetermined master curve. The master curve was taken up in the unregulated process and represents the quality criteria of a formed useable part. The real-time MATLAB Simulink XPC- Target simulation tool was used to develop an adjustment strategy that connects the specific signals of the press control (such as the tappet path, the die

  15. Experimental Investigation of Resistance Spot Welding for Sheet Metals Used in Automotive Industry

    NASA Astrophysics Data System (ADS)

    Jou, Min

    Resistance spot welding (RSW) is used for the fabrication of sheet metal assemblies. The major advantages of spot welding are high speed and adaptability for automation in high-volume and/or high-rate production. Despite these advantages, resistance spot welding suffers from a major problem of inconsistent quality from weld to weld. This problem results from both the complexity of the basic process as well as from numerous sources of variability, noise, and errors. Any or all of these complicate automation, reduce weld quality, demand over welding and drive up production costs. For this reason, ensuring weld quality has been and remains a major challenge and goal. The objective of this research is to explore the phenomenon of how changes in a controllable parameter of % heat input affect a measurable output signal indicative of strength and weld quality for various sheet steels used in the automotive industry. The approach of this research is to create a relationship between a key process input variable and the key process output of a quality weld. The input parameter chosen is % heat input, as this directly effects the size and strength of the resulting weld. The output chosen is electrode displacement, as this has been shown to accurately reflect the formation and growth of a weld nugget. A series of experiments was conducted to explore how changes of % heat input and process variations affect the electrode displacement curve for various sheet steels used in the automotive industry. Experimental results show that the electrode displacement increased when higher % heat input was applied. Weld nugget starts to grow when electrode velocity cube changes from positive to negative. Characteristic electrode displacement curves were developed for process variations. A poor part fit-up condition shifted the electrode displacement curve to the right as a result of a smaller weld nugget being formed. Worn electrode lowers the electrode displacement curve. For bare steel

  16. Studies on the finite element simulation in sheet metal stamping processes

    NASA Astrophysics Data System (ADS)

    Huang, Ying

    The sheet metal stamping process plays an important role in modern industry. With the ever-increasing demand for shape complexity, product quality and new materials, the traditional trial and error method for setting up a sheet metal stamping process is no longer efficient. As a result, the Finite Element Modeling (FEM) method has now been widely used. From a physical point of view, the formability and the quality of a product are influenced by several factors. The design of the product in the initial stage and the motion of the press during the production stage are two of these crucial factors. This thesis focuses on the numerical simulation for these two factors using FEM. Currently, there are a number of commercial FEM software systems available in the market. These software systems are based on an incremental FEM process that models the sheet metal stamping process in small incremental steps. Even though the incremental FEM is accurate, it is not suitable for the initial conceptual design for its needing of detailed design parameters and enormous calculation times. As a result, another type of FEM, called the inverse FEM method or one-step FEM method, has been proposed. While it is less accurate than that of the incremental method, this method requires much less computation and hence, has a great potential. However, it also faces a number of unsolved problems, which limits its application. This motivates the presented research. After the review of the basic theory of the inverse method, a new modified arc-length search method is proposed to find better initial solution. The methods to deal with the vertical walls are also discussed and presented. Then, a generalized multi-step inverse FEM method is proposed. It solves two key obstacles: the first one is to determine the initial solution of the intermediate three-dimensional configurations and the other is to control the movement of nodes so they could only slide on constraint surfaces during the search by

  17. Edge pinch instability of liquid metal sheet in a transverse high-frequency ac magnetic field.

    PubMed

    Priede, Jānis; Etay, Jacqueline; Fautrelle, Yves

    2006-06-01

    We analyze the linear stability of the edge of a thin liquid metal layer subject to a transverse high-frequency ac magnetic field. The layer is treated as a perfectly conducting liquid sheet that allows us to solve the problem analytically for both a semi-infinite geometry with a straight edge and a thin disk of finite radius. It is shown that the long-wave perturbations of a straight edge are monotonically unstable when the wave number exceeds the critical value k(c) = F0/(gamma l0), which is determined by the linear density of the electromagnetic force F0 acting on the edge, the surface tension gamma, and the effective arclength of edge thickness l0. Perturbations with wavelength shorter than critical are stabilized by the surface tension, whereas the growth rate of long-wave perturbations reduces as similar to k for k --> 0. Thus, there is the fastest growing perturbation with the wave number k max = 2/3 k(c). When the layer is arranged vertically, long-wave perturbations are stabilized by the gravity, and the critical perturbation is characterized by the capillary wave number k(c) = square root of (g rho/gamma), where g is the acceleration due to gravity and rho is the density of metal. In this case, the critical linear density of electromagnetic force is F(0,c) = 2k(c)l0 gamma, which corresponds to the critical current amplitude I(0,c) = 4 square root of (pi k(c) l0L gamma/mu 0) when the magnetic field is generated by a straight wire at the distance L directly above the edge. By applying the general approach developed for the semi-infinite sheet, we find that a circular disk of radius R0 placed in a transverse uniform high-frequency ac magnetic field with the induction amplitude B0 becomes linearly unstable with respect to exponentially growing perturbation with the azimuthal wave number m = 2 when the magnetic Bond number exceeds Bm(c) = B(0)2 R(0)2 / (2 mu 0 l0 gamma) = 3 pi. For Bm > Bm(c), the wave number of the fastest growing perturbation is m(max) = [2

  18. Cancer incidence among mild steel and stainless steel welders and other metal workers.

    PubMed

    Hansen, K S; Lauritsen, J M; Skytthe, A

    1996-10-01

    The cancer incidence in a historical cohort of 10,059 metal workers employed during the period 1964-1984 was investigated. Standardized incidence ratios (SIR) were calculated based on registry extracts from the Danish Cancer registry. Lifetime exposure data (occupational and other) were obtained by a postal questionnaire in living cohort members and interviews by proxy for deceased and emigrated subjects. The incidence of lung cancer was increased among workers ever "employed as welders" (SIR = 1.38, 95% C.I. 1.03-1.81). There was a significant excess risk of lung cancer among "mild steel (MS) only welders" (SIR = 1.61, 95% C.I. 1.07-2.33) and "nonwelders" (SIR = 1.69, 95% C.I. 1.23-2.26) (indicating carcinogenic exposures other than welding), a borderline significant lung cancer excess among "MS ever welders" (SIR = 1.32, 95% C.I. 0.97-1.76), and a nonsignificant excess risk of lung cancer among "stainless steel (SS) only welders" (SIR = 2.38, 95% C.I. 0.77-5.55). In spite of signs of inconsistency in the risk estimation by duration and latency, we find the results support the conclusions of other studies: employment as a welder is associated with an increased lung cancer risk. PMID:8892541

  19. Effects of customized foot orthoses on manufacturing workers in the metal industry.

    PubMed

    García-Hernández, César; Huertas-Talón, José-Luis; Sánchez-Álvarez, Eduardo J; Marín-Zurdo, Javier

    2016-01-01

    This 8-week study evaluates the effects of customized foot orthoses on work-related musculoskeletal disorders (WMSDs) of metal industry workers. These WMSDs were evaluated applying the Nordic musculoskeletal questionnaire (NMQ) at three different times (start, 4th week and 8th week) and additional questions were also formulated to obtain information about adaptation, fatigue, comfort and possible improvements. According to the NMQ results, statistical significance was found in the improvements after 4 weeks (p < 0.05 in two areas, p < 0.01 in three areas, p < 0.001 in two areas and no significance in the other two) and after 8 weeks (p < 0.01 in three areas, p < 0.001 in four areas and no significance in the other two). The additional questions indicated fatigue reduction (both in general and in lower extremity), comfort level increase (after the adaptation period) and good acceptance, according to workers' answers, suggesting customized orthoses can be effective in reducing and preventing WMSDs in several body regions. PMID:26651384

  20. Lead poisoning in precious metals refinery assayers: a failure to notify workers at high risk.

    PubMed

    Kern, D G

    1994-05-01

    Lead poisoning in a precious metals refinery fire assayer and a routine OSHA inspection prompted an investigation of the index facility, a survey of the industry, and efforts to notify assayers of this previously unrecognized hazard. Air and blood samples were obtained at the index facility. Management personnel from all fire assay laboratories in Rhode Island and southern Massachusetts were interviewed. The industry's trade association, OSHA, NIOSH, trade unions, and the media were asked to assist in a nationwide notification effort. Assayers at the index facility had excessive exposures to lead due to an age-old, lead-based assaying method that remains the industry gold standard. Blood lead levels of the three assayers (mean 61.3 micrograms/dl, range 48-86 micrograms/dl) were considerably higher than those of 16 other refinery workers (mean 27.4 micrograms/dl, range 13-49 micrograms/dl). The industry survey revealed inadequate knowledge of both the lead hazard and the applicability of the OSHA lead standard. Notification efforts failed in large part due to economic obstacles. The notification of workers at high risk of lead exposure and the eradication of occupational lead poisoning will require greater attention to economic forces. PMID:8030646

  1. [Skin diseases and sensitization to metals in construction workers engaged in the production of pre-cast cellular concrete slabs].

    PubMed

    Kieć-Swierczyńska, M; Woźniak, H; Wojtczak, J

    1989-01-01

    The study involved 461 building workers exposed to ashes, cement and ash-cement mixtures in direct production and at auxiliary posts (fitters, welders, mechanics, electricians etc.). In addition, all those workers were exposed to lubricants ans machine oils, as well as anti-adhesive oils used to lubricate moulds. All the subjects underwent patch tests. Dermatitis was found in 18.9%, whereas oil acne in 7.4% of subjects, 23.0% exhibited chromium allergy, 15.2% - cobalt allergy and 5.0% - nickel allergy. Two workers were ++hypersensitive to zinc. No differences were found in the rates of dermatitis, oil acne and metal allergy between production workers and auxiliary ones. Airborne dust concentrations at those workplaces were similar. Cement and ashes contained compounds of chromium, cobalt and nickel. PMID:2531830

  2. Exposures to inhalable and "total" oil mist aerosol by metal machining shop workers.

    PubMed

    Wilsey, P W; Vincent, J H; Bishop, M J; Brosseau, L M; Greaves, I A

    1996-12-01

    Several recent studies have compared worker personal aerosol exposures as measured by the current method with those obtained by a new approach based on collecting the inhalable fraction, intended to represent all the particles that are capable of entering through the nose and/or mouth during breathing. The present study investigated this relationship for a metal machining facility where aerosols were generated from severely refined, nonaqueous ("straight") cutting oils used during the lathe working of metal rod stock. Workers (n = 23) wore two personal aerosol samplers simulataneously, one of the 37-mm type (for "total" aerosol exposure, E37) and the other of the Institute of Occupational Medicine (IOM) type (for inhalable aerosol exposure, EIOM). The data were analyzed by weighted least squares linear regression to determine the coefficient S in the relation EIOM = S.E37. It was found that S = 2.96 +/- 0.60. This ratio-in which exposure to inhalable aerosol was greater than to "total" aerosol-is consistent with previous observations in other industries. The relative coarsenss of the oil mist aerosol, as estimated by cascade impactor measurements, probably explains the difference between the sampling methods. The collection of large "splash" droplets, may also contribute. Future occupational aerosol standards for metalworking fluids will be based on the new, health-related criteria, and exposures will be assessed on the basis of the inhalable fraction. Results of studies like that described here will enable assessment of the impact on future workplace aerosol exposure assessments of introducing new standards. PMID:8976589

  3. Electronic and magnetic properties of monolayer SiC sheet doped with 3d-transition metals

    NASA Astrophysics Data System (ADS)

    Bezi Javan, Masoud

    2016-03-01

    We theoretically studied the electronic and magnetic properties of the monolayer SiC sheet doped by 3d transition-metal (TM) atoms. The structural properties, induced strain, electronic and magnetic properties were studied for cases that a carbon or silicon of the SiC sheet replaced with TM atoms. We found that the mount of induced strain to the lattice structure of the SiC sheet with substituting TM atoms is different for Si (TMSi) and C (TMC) sites as the TMSi structures have lower value of the strain. Also the TM atoms can be substituted in the lattice of the SiC sheet with different binding energy values for TMSi and TMC structures as the TMSi structures have higher value of the binding energies. Dependent to the structural properties, the TM doped SiC sheets show magnetic or nonmagnetic properties. We found that some structures such as MnSi, CuSi and CoC configurations have significant total magnetic moment about 3 μB.

  4. A simple method for understanding the triangular growth patterns of transition metal dichalcogenide sheets

    SciTech Connect

    Zhu, Siya; Wang, Qian

    2015-10-15

    Triangular nanoflake growth patterns have been commonly observed in synthesis of transition metal dichalcogenide sheets and their hybrid structures. Triangular nanoflakes not only show exceptional properties, but also can serve as building blocks for two or three dimensional structures. In this study, taking the MoS{sub 2} system as a test case, we propose a Matrix method to understand the mechanism of such unique growth pattern. Nanoflakes with different edge types are mathematically described with configuration matrices, and the total formation energy is calculated as the sum of the edge formation energies and the chemical potentials of sulfur and molybdenum. Based on energetics, we find that three triangular patterns with the different edge configurations are energetically more favorable in different ranges of the chemical potential of sulfur, which are in good agreement with experimental observations. Our algorithm has high efficiency and can deal with nanoflakes in microns which are beyond the ability of ab-initio method. This study not only elucidates the mechanism of triangular nanoflake growth patterns in experiment, but also provides a clue to control the geometric configurations in synthesis.

  5. Electrode Erosion Observed in Electrohydraulic Discharges Used in Pulsed Sheet Metal Forming

    NASA Astrophysics Data System (ADS)

    Bonnen, John J. F.; Golovashchenko, Sergey F.; Dawson, Scott A.; Mamutov, Alexander V.

    2013-12-01

    In this paper, we present results of electrode durability testing and electrode design in a pulsed electrohydraulic discharge environment. Pulsed electrohydraulic forming (EHF) is an electrodynamic process based upon high-voltage discharge of capacitors between two electrodes positioned in a fluid-filled chamber. EHF enables a more uniform distribution of strains, widens the formability window, and reduces elastic springback in the final part when compared to traditional sheet metal stamping. This extended formability allows the fabrication of panels of alternative high strength alloys that are otherwise difficult to make conventionally. It was found that, of the materials tested, steel electrodes not only survived the stresses encountered in the EHF chamber but also had lower erosion rates compared to molybdenum. Erosion rates were found to be constant for low carbon steel at 3.7 mm3/discharge, and they were high enough that the initial tip geometry was rapidly worn away and a more geometrically and thus electrically stable tip geometry had to be selected. Entrained air in the system had little influence on erosion rates but numerical modeling suggests that the erosion process takes place during the very initial stages of the pulse. Lastly, it was determined that the electrodes discussed in this paper can survive 2000 pulses.

  6. Three-dimensional reconstruction and morphologic characteristics of porous metal fiber sintered sheet

    SciTech Connect

    Wang, Qinghui; Huang, Xiang; Zhou, Wei; Li, Jingrong

    2013-12-15

    This paper presents an approach to achieve morphological characterizing for complex porous materials based on micro X-ray tomography images, with an example of a novel porous metal fiber sheet produced through solid-state sintering method. The geometrical reconstruction was performed after selection of volume of interest and image processing of anisotropic diffusion smooth. The reconstructed gray level images were then transferred into binary images by adjusting binarization threshold according to the actual porosity. Taking into account the tubular structural feature of the fibers, skeleton extraction algorithm based on the distance transform function was applied and further improved by the scale axis transform method. The skeleton was later pruned and segmented according to the contact points to perform morphological characterizing. Compared with actual manufacturing parameters, the style, length, radius, orientation and tortuosity of fiber segments were discussed. The results show that our proposed method can well describe the actual geometrical and morphological characteristics, which will provide a promising method for the structural description of fibrous networks. - Highlights: • Micro-CT technology was used to achieve the 3D geometrical reconstruction. • Skeleton extraction algorithm was modified to get the medial skeleton. • Skeleton filter operation was adopted to deal with the segmented skeleton. • Useful morphological statistics was obtained through skeleton segments. • Relationship between structure and manufacturing processes was discussed.

  7. Technology maturation project on optimization of sheet metal forming of aluminum for use in transportation systems

    NASA Astrophysics Data System (ADS)

    Johnson, Ken I.; Smith, Mark T.; Lavender, Curt A.; Khalell, Mohammad A.

    1994-10-01

    Using aluminum instead of steel in transportation systems could dramatically reduce the weight of vehicles, an effective way of decreasing energy consumption and emissions. The current cost of sheet metal formed (SMF) aluminum alloys (about $4 per pound) and the relatively long forming times of current materials are serious drawbacks to the widespread use of SMF in industry. The interdependence of materials testing and model development is critical to optimizing SMF since the current process is conducted in a heated, pressurized die where direct measurement of critical SMF parameters is extremely difficult. Numerical models provide a means of tracking the forming process, allowing the applied gas pressure to be adjusted to maintain the optimum SMF behavior throughout the forming process. Thus, models can help produce the optimum SMF component in the least amount of time. The Pacific Northwest Laboratory is integrating SMF model development with research in improved aluminum alloys for SMF. The objectives of this research are: develop and characterize competitively priced aluminum alloys for SMF applications in industry; improve numerical models to accurately predict the optimum forming cycle for reduced forming time and improved quality; and verify alloy performance and model accuracy with forming tests conducted in PNL's Superplastic Forming User Facility. The activities performed in this technology maturation project represent a critical first step in achieving these objectives through cooperative research among industry, PNL, and universities.

  8. A simple method for understanding the triangular growth patterns of transition metal dichalcogenide sheets

    NASA Astrophysics Data System (ADS)

    Zhu, Siya; Wang, Qian

    2015-10-01

    Triangular nanoflake growth patterns have been commonly observed in synthesis of transition metal dichalcogenide sheets and their hybrid structures. Triangular nanoflakes not only show exceptional properties, but also can serve as building blocks for two or three dimensional structures. In this study, taking the MoS2 system as a test case, we propose a Matrix method to understand the mechanism of such unique growth pattern. Nanoflakes with different edge types are mathematically described with configuration matrices, and the total formation energy is calculated as the sum of the edge formation energies and the chemical potentials of sulfur and molybdenum. Based on energetics, we find that three triangular patterns with the different edge configurations are energetically more favorable in different ranges of the chemical potential of sulfur, which are in good agreement with experimental observations. Our algorithm has high efficiency and can deal with nanoflakes in microns which are beyond the ability of ab-initio method. This study not only elucidates the mechanism of triangular nanoflake growth patterns in experiment, but also provides a clue to control the geometric configurations in synthesis.

  9. Explicit Analysis of Transversely Anisotropic and Axisymmetric Sheet Metal Forming Process Using 6-component Barlat Yield Function

    NASA Astrophysics Data System (ADS)

    Wang, Jin-Yan; Sun, Ji-Xian; Chen, Jun

    2005-08-01

    In most FEM codes, the isotropic-elastic & transversely anisotropic-elastoplastic model using Hill's yield function has been widely adopted in 3D shell elements (modified to meet the plane-stress condition) and 3D solid elements. However, when the 4-node quadrilateral axisymmetric element is used for 2D sheet metal forming simulation, the above transversely anisotropic model is not available in FEM code LS-DYNA3D. A novel approach for the explicit analysis of transversely anisotropic and axisymmetric sheet metal forming using 6-component Barlat yield function is elaborated in detail in this paper. The related formula and parameters are derived directly. Numerical results obtained using the new model fit well with the Hill solution.

  10. A reliability study of springback on the sheet metal forming process under probabilistic variation of prestrain and blank holder force

    NASA Astrophysics Data System (ADS)

    Mrad, Hatem; Bouazara, Mohamed; Aryanpour, Gholamreza

    2013-08-01

    This work deals with a reliability assessment of springback problem during the sheet metal forming process. The effects of operative parameters and material properties, blank holder force and plastic prestrain, on springback are investigated. A generic reliability approach was developed to control springback. Subsequently, the Monte Carlo simulation technique in conjunction with the Latin hypercube sampling method was adopted to study the probabilistic springback. Finite element method based on implicit/explicit algorithms was used to model the springback problem. The proposed constitutive law for sheet metal takes into account the adaptation of plastic parameters of the hardening law for each prestrain level considered. Rackwitz-Fiessler algorithm is used to find reliability properties from response surfaces of chosen springback geometrical parameters. The obtained results were analyzed using a multi-state limit reliability functions based on geometry compensations.

  11. Metal-free Ketjenblack incorporated nitrogen-doped carbon sheets derived from gelatin as oxygen reduction catalysts.

    PubMed

    Nam, Gyutae; Park, Joohyuk; Kim, Sun Tai; Shin, Dong-bin; Park, Noejung; Kim, Youngsik; Lee, Jang-Soo; Cho, Jaephil

    2014-01-01

    Electrocatalysts facilitating oxygen reduction reaction (ORR) are vital components in advanced fuel cells and metal-air batteries. Here we report Ketjenblack incorporated nitrogen-doped carbon sheets derived from gelatin and apply these easily scalable materials as metal-free electrocatalysts for ORR. These carbon nanosheets demonstrate highly comparable catalytic activity for ORR as well as better durability than commercial Vulcan carbon supported Pt catalysts in alkaline media. Physico-chemical characterization and theoretical calculations suggest that proper combination of graphitic and pyridinic nitrogen species with more exposed edge sites effectively facilitates a formation of superoxide, [O2(ad)](-), via one-electron transfer, thus increasing catalytic activities for ORR. Our results demonstrate a novel strategy to expose more nitrogen doped edge sites by irregular stacked small sheets in developing better electrocatalysts for Zn-air batteries. These desirable architectures are embodied by an amphiphlilic gelatin mediated compatible synthetic strategy between hydrophobic carbon and aqueous water. PMID:24635744

  12. Scalable synthesis of layer-controlled WS2 and MoS2 sheets by sulfurization of thin metal films

    NASA Astrophysics Data System (ADS)

    Orofeo, Carlo M.; Suzuki, Satoru; Sekine, Yoshiaki; Hibino, Hiroki

    2014-08-01

    Transition metal dichalcogenides (TMDs) have emerged as exciting 2D materials beyond graphene due to their promising applications in the field of electronics and optoelectronics. Hence, the ability to produce controllable and uniformly thick TMD sheets over a large area is of utmost important for large-scale applications. Here, a facile method of synthesizing large-area, layer-controlled WS2, and MoS2 sheets by sulfurization of their corresponding thin metal films is reported. A metal film, which is deposited by magnetron sputtering method, can be adjusted to produce, with great control, the desired sheet thickness down to a monolayer. Various characterization techniques, such as Raman, photoluminescence, and transmission electron microscopy, were used to evaluate the grown films. The results confirmed some of the exotic properties of TMDs such as the thickness dependent band-gap transition (indirect to direct band gap) and Raman shift. Devices made directly on the as-grown film showed modest mobility, ranging from 0.005 to 0.01 cm2 V-1s-1. Our synthesis method is simple and could also be used to synthesize other TMDs.

  13. Ductile Damage and Fatigue Behavior of Semi-Finished Tailored Blanks for Sheet-Bulk Metal Forming Processes

    NASA Astrophysics Data System (ADS)

    Besserer, Hans-Bernward; Hildenbrand, Philipp; Gerstein, Gregory; Rodman, Dmytro; Nürnberger, Florian; Merklein, Marion; Maier, Hans Jürgen

    2016-03-01

    To produce parts from sheet metal with thickened functional elements, bulk forming operations can be employed. For this new process class, the term sheet-bulk metal forming has been established recently. Since sheet-bulk metal forming processes such as orbital forming generates triaxial stress and strain states, ductile damage is induced in the form of voids in the microstructure. Typical parts will experience cyclic loads during service, and thus, the influence of ductile damage on the fatigue life of parts manufactured by orbital forming is of interest. Both the formation and growth of voids were characterized following this forming process and then compared to the as-received condition of the ferritic deep drawing steel DC04 chosen for this study. Subsequent to the forming operation, the specimens were fatigued and the evolution of ductile damage and the rearrangement of the dislocation networks occurring during cyclic loading were determined. It was shown, that despite an increased ductile damage due to the forming process, the induced strain hardening has a positive effect on the fatigue life of the material. However, by analyzing the fatigued specimens a development of the ductile damage by an increasing number of voids and a change in the void shape were detected.

  14. Validity of the sheet demagnetising factor in characterisation of advanced metal particle tapes

    NASA Astrophysics Data System (ADS)

    Cookson, R. D.; Bissell, P. R.; Kay, G. E.; Parker, D. A.

    2002-04-01

    This paper describes a model to test the validity of using the sheet demagnetising factor for advanced particulate tape magnetic measurements. The model predicts that, as the tape thickness and the volume packing fraction are reduced, the effective demagnetising factor deviates from the sheet value and, for a typical commercial advanced double coated MP tape, is in error by ˜6%.

  15. Experimental Studies on Flexible Forming of Sheet Metals Assisted by Magnetic Force Transfer Medium

    NASA Astrophysics Data System (ADS)

    Li, Feng; Zhou, Fu Jian; Wang, Mo Nan; Xu, Peng; Jin, Cheng Chuang

    2016-06-01

    To improve the thickness uniformity and increase the forming limit of sheets to enhance their overall quality, a magnetorheological fluid (MRF) was injected into the punch cavity to act as the force transfer medium and fulfill the function of flexible pressing during the sheet bulging process. The rheological properties of the MRF were changed under the influence of a magnetic field produced by loading different currents, which allowed variation of stress states and deformation modes in the 0.75-mm-thick 304 stainless steel sheets. With increasing current (up to 3.5 A), the sheet-forming limit increased by 16.13% at most, and the fracture morphology experienced a certain change. Additionally, both the bulge height and the wall thickness distribution had obvious changes with a punch stroke of 10 mm. According to the experimental analysis, the MRF can be used successfully as a pressure-carrying medium in the sheet forming process.

  16. Endoscopic fringe projection for in-situ inspection of a sheet-bulk metal forming process

    NASA Astrophysics Data System (ADS)

    Matthias, Steffen; Kästner, Markus; Reithmeier, Eduard

    2015-05-01

    Sheet-bulk metal forming is a new production process capable of performing deep-drawing and massive forming steps in a single operation. However, due to the high forming forces of the forming process, continuous process control is required in order to detect wear on the forming tool before production quality is impacted. To be able to measure the geometry of the forming tool in the limited space of forming presses, a new inspection system is being developed within the SFB/TR 73 collaborative research center. In addition to the limited space, the process restricts the amount of time available for inspection. Existing areal optical measurement systems suffer from shadowing when measuring the tool's inner elements, as they cannot be placed in the limited space next to the tool, while tactile measurement systems cannot meet the time restrictions for measuring the areal geometries. The new inspection system uses the fringe projection optical measurement principle to capture areal geometry data from relevant parts of the forming tool in short time. Highresolution image fibers are used to connect the system's compact sensor head to a base unit containing both camera and projector of the fringe projection system, which can be positioned outside of the moving parts of the press. To enable short measurement times, a high intensity laser source is used in the projector in combination with a digital micro-mirror device. Gradient index lenses are featured in the sensor head to allow for a very compact design that can be used in the narrow space above the forming tool inside the press. The sensor head is attached to an extended arm, which also guides the image fibers to the base unit. A rotation stage offers the possibility to capture measurements of different functional elements on the circular forming tool by changing the orientation of the sensor head next to the forming tool. During operation of the press, the arm can be travelled out of the moving parts of the forming press

  17. Experimental, Statistical and Simulation Study on Spring-back Behavior in Incremental Sheet Metal Forming (ISMF) Process

    NASA Astrophysics Data System (ADS)

    Vahdati, Alireza; Vahdati, Mehdi

    2011-01-01

    Recently, considerable attention has been paid for the many kinds of flexible production processes. Most concerned one is the incremental sheet metal forming (ISMF) process, which does not require any high capacity press machine and a set of dies with specified shape for the product. ISMF process apparatus requires a traveling tool with simple shape and a holder which holds the sheet stationary at its periphery. In this research, spring-back and its effect on dimensional precision of ISMF process has been studied. The influence of process parameters such as: vertical step size (ν), sheet thickness (t), tool diameter (d), feed rate (f) and spindle speed (n) have been investigated. A series of experimental tests have been implemented for a straight groove bead-shape part made of aluminum sheets (Al 1050-O). In first section, a reliable statistical analysis has been carried out to extract the importance of each parameter. The obtained model permits to select appropriate process parameters to reduce spring-back effectively. In second section, simulation process has been implemented by FEM software. In final, experimental results confirm the results of simulation and comparisons between experimental and simulation results of spring-back have shown good agreement.

  18. Metal release from stainless steel powders and massive sheets--comparison and implication for risk assessment of alloys.

    PubMed

    Hedberg, Yolanda; Mazinanian, Neda; Odnevall Wallinder, Inger

    2013-02-01

    Industries that place metal and alloy products on the market are required to demonstrate that they are safe for all intended uses, and that any risks to humans, animals or the environment are adequately controlled. This requires reliable and robust in vitro test procedures. The aim of this study is to compare the release of alloy constituents from stainless steel powders of different grades (focus on AISI 316L) and production routes into synthetic body fluids with the release of the same metals from massive sheets in relation to material and surface characteristics. The comparison is justified by the fact that the difference between massive surfaces and powders from a metal release/dissolution and surface perspective is not clearly elucidated within current legislations. Powders and abraded and aged (24 h) massive sheets were exposed to synthetic solutions of relevance for biological settings and human exposure routes, for periods of up to one week. Concentrations of released iron, chromium, nickel, and manganese in solution were measured, and the effect of solution pH, acidity, complexation capacity, and proteins elucidated in relation to surface oxide composition and its properties. Implications for risk assessments based on in vitro metal release data from alloys are elucidated. PMID:25208703

  19. Effect of Individual Layer Shape on the Mechanical Properties of Dissimilar Al Alloys Laminated Metal Composite Sheets

    NASA Astrophysics Data System (ADS)

    Chen, Zejun; Wu, Xia; Hu, Hongbo; Chen, Quanzhong; Liu, Qing

    2014-03-01

    For the dissimilar laminated metal composite sheets (LMCS) fabricated by roll bonding technology, the great differences of mechanical properties between the constituent metals lead to the non-uniform deformation and individual layer necking. The individual layer shape affects the mechanical properties and microstructure of dissimilar LMCS. The Al/Al alloy (1100/7075) LMCS with the same thickness and ratio of dissimilar metals, but different individual layer shapes, have been successfully fabricated by hot accumulative roll bonding in conjunction with cold rolling technology. Some effective methods (such as sheet crown, warp degree, and slant angle) were presented to quantitatively evaluate the individual layer shape and necking of constituent metals. The microstructure and mechanical properties of 1100/7075 LMCS with different individual layer shapes were investigated. The effects of bonding interface on the mechanical properties were obtained based on the assessment of individual layer shapes and necking. The strength and elongation of LMCS decrease with the increase of variation of individual layer shapes and necking when the number of layers keeps constant. The research results offer some theoretical guides and references for adjusting the control measures of compatibility deformation, optimizing the hot roll bonding technologies, and designing the novel high-performance dissimilar LMCS.

  20. First-principles study of half-metallicity in semi-hydrogenated BC3, BC5, BC7, and B-doped graphone sheets

    PubMed Central

    2011-01-01

    Using first principles calculations, we investigate the electronic structures of semi-hydrogenated BC3, BC5, BC7, and B-doped graphone sheets. We find that all the semi-hydrogenated boron-carbon sheets exhibit half-metallic behaviors. The magnetism originates from the non-bonding pz orbitals of carbon atoms, which cause the flat bands to satisfy the Stoner criterion. On the other hand, boron atoms weaken the magnetic moments of nearby carbon atoms and act as holes doped in the sheets. It induces the down shift of the Fermi level and the half-metallicity in semi-hydrogenated sheets. Our studies demonstrate that the semi-hydrogenation is an effective route to achieve half-metallicity in the boron-carbon systems. PMID:21711690

  1. A general and efficient method for decorating graphene sheets with metal nanoparticles based on the non-covalently functionalized graphene sheets with hyperbranched polymers.

    PubMed

    Li, Haiqing; Han, Lina; Cooper-White, Justin J; Kim, Il

    2012-02-21

    Multipyrene terminated hyperbranched polyglycidol (mPHP) has been synthesized and used to non-covalently functionalize pristine graphene sheets (GSs) through π-π stacking interactions. Mediated by the mPHP layer, a variety of metal nanoparticles (Au, Ag and Pt) were in situ generated and deposited onto the surface-modified GS, yielding versatile GS/mPHP/metal nanohybrids. As typical examples, by simply controlling the concentration of HAuCl(4) used, Au nanostructures ranging from isolated spheres to a continuous film were created and coated onto the surface-modified GS. The studies on the fluorescence properties of resulting GS/mPHP/Au hybrid nanostructures reveal that the GS and controllable content of Au components in the hybrids can effectively quench the fluorescence emission of mPHP in a controlled manner. Further investigation indicates that GS/mPHP/Au hybrids are promising surface enhanced Raman scattering (SERS) substrates. The SERS activities of these hybrids depend on the contents and form of the Au. The GS/mPHP/Au hybrid containing continuous Au films exhibits the strongest SERS activity. GS/mPHP/Au hybrids are also used as efficient heterogeneous catalysts for the reduction of 4-NP, and demonstrate excellent catalytic performance. The detailed reaction kinetics and the reusability of such catalysts have also been investigated. PMID:22278595

  2. Topometry optimization of sheet metal structures for crashworthiness design using hybrid cellular automata

    NASA Astrophysics Data System (ADS)

    Mozumder, Chandan K.

    The objective in crashworthiness design is to generate plastically deformable energy absorbing structures which can satisfy the prescribed force-displacement (FD) response. The FD behavior determines the reaction force, displacement and the internal energy that the structure should withstand. However, attempts to include this requirement in structural optimization problems remain scarce. The existing commercial optimization tools utilize models under static loading conditions because of the complexities associated with dynamic/impact loading. Due to the complexity of a crash event and the consequent time required to numerically analyze the dynamic response of the structure, classical methods (i.e., gradient-based and direct) are not well developed to solve this undertaking. This work presents an approach under the framework of the hybrid cellular automaton (HCA) method to solve the above challenge. The HCA method has been successfully applied to nonlinear transient topology optimization for crashworthiness design. In this work, the HCA algorithm has been utilized to develop an efficient methodology for synthesizing shell-based sheet metal structures with optimal material thickness distribution under a dynamic loading event using topometry optimization. This method utilizes the cellular automata (CA) computing paradigm and nonlinear transient finite element analysis (FEA) via ls-dyna. In this method, a set field variables is driven to their target states by changing a convenient set of design variables (e.g., thickness). These rules operate locally in cells within a lattice that only know local conditions. The field variables associated with the cells are driven to a setpoint to obtain the desired structure. This methodology is used to design for structures with controlled energy absorption with specified buckling zones. The peak reaction force and the maximum displacement are also constrained to meet the desired safety level according to passenger safety

  3. Finite Element Simulation of Sheet Metal Forming Process Using Local Interpolation for Tool Surfaces

    SciTech Connect

    Hama, Takayuki; Takuda, Hirohiko; Takamura, Masato; Makinouchi, Akitake; Teodosiu, Cristian

    2005-08-05

    Treatment of contact between a sheet and tools is one of the most difficult problems to deal with in finite-element simulations of sheet forming processes. In order to obtain more accurate tool models without increasing the number of elements, this paper describes a new formulation for contact problems using interpolation proposed by Nagata for tool surfaces. A contact search algorithm between sheet nodes and the interpolated tool surfaces was developed and was introduced into the static-explicit elastoplastic finite-element method code STAMP3D. Simulations of a square cup deep drawing process with a very coarsely discretized punch model were carried out. The simulated results showed that the proposed algorithm gave the proper drawn shape, demonstrating the validity of the proposed algorithm.

  4. Experimental Characterization of Sheet Metal Deformation During Electro-Hydraulic Forming

    SciTech Connect

    Rohatgi, Aashish; Stephens, Elizabeth V.; Soulami, Ayoub; Davies, Richard W.; Smith, Mark T.

    2011-11-01

    This manuscripts reports results of the last 2-3 years work pertaining to DOE-OVT funded project on pulse-pressure forming of light-weight materials. We report experimental results of electrohydraulically formed sheets where data is determined using a pair of high-speed cameras and analyzed using a digital image correlation technique. These results are relevant to the formability of sheet materials and of importance to the automotive industry. To the authors’ knowledge, such results have not been published in the literature.

  5. 76 FR 37153 - Indianapolis Metal Center, a Division of General Motors Company, Including Workers Whose Wages...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-24

    ... automotive stampings. The notice was published in the Federal Register on March 10, 2011 (76 FR 13230). At... Workers From Aerotek, Comprehensive Logistics Company, Inc., Hewlett Packard, Ideal Setech, LLC, Quaker... workers from Aerotek, Comprehensive Logistics Company, Inc., Hewlett Packard, Ideal Setech, LLC,...

  6. PM2.5 metal exposures and nocturnal heart rate variability: a panel study of boilermaker construction workers

    PubMed Central

    Cavallari, Jennifer M; Eisen, Ellen A; Fang, Shona C; Schwartz, Joel; Hauser, Russ; Herrick, Robert F; Christiani, David C

    2008-01-01

    Background To better understand the mechanism(s) of particulate matter (PM) associated cardiovascular effects, research priorities include identifying the responsible PM characteristics. Evidence suggests that metals play a role in the cardiotoxicity of fine PM (PM2.5) and in exposure-related decreases in heart rate variability (HRV). We examined the association between daytime exposure to the metal content of PM2.5 and night HRV in a panel study of boilermaker construction workers exposed to metal-rich welding fumes. Methods Twenty-six male workers were monitored by ambulatory electrocardiogram (ECG) on a workday while exposed to welding fume and a non-workday (baseline). From the ECG, rMSSD (square root of the mean squared differences of successive intervals) was summarized over the night (0:00–7:00). Workday, gravimetric PM2.5 samples were analyzed by x-ray fluorescence to determine metal content. We used linear mixed effects models to assess the associations between night rMSSD and PM2.5 metal exposures both with and without adjustment for total PM2.5. Matched ECG measurements from the non-workday were used to control for individual cardiac risk factors and models were also adjusted for smoking status. To address collinearity between PM2.5 and metal content, we used a two-step approach that treated the residuals from linear regression models of each metal on PM2.5 as surrogates for the differential effects of metal exposures in models for night rMSSD. Results The median PM2.5 exposure was 650 μg/m3; median metal exposures for iron, manganese, aluminum, copper, zinc, chromium, lead, and nickel ranged from 226 μg/m3 to non-detectable. We found inverse linear associations in exposure-response models with increased metal exposures associated with decreased night rMSSD. A statistically significant association for manganese was observed, with a decline of 0.130 msec (95% CI: -0.162, -0.098) in night rMSSD for every 1 μg/m3 increase in manganese. However, even

  7. Laser processing for strengthening of the self-restoring metal-elastomer interface on a silicone sheet

    NASA Astrophysics Data System (ADS)

    Yasuda, Kiyokazu

    2012-08-01

    A self-restoring microsystem is a unique concept which realizes the sensing functionality and robust interface which mechanically and electrically connects a deformable object such as a human body with printed electronic devices. For this purpose, the formation of conductive wiring on an elastomer substrate was attempted using the nickel ink printing process. Before the wiring process, surface patterning of a silicone sheet by a galvano-scanned infrared laser was conducted for the enhancement of interface adhesion of the metal deposit and polymer. Characterization of the fabricated pattern was conducted by optical microscopy. The novel method was successfully demonstrated as a fabrication of selective patterns of metal particles on self-restoring MEMS.

  8. Mutual Inductance Problem for a System Consisting of a Current Sheet and a Thin Metal Plate

    NASA Technical Reports Server (NTRS)

    Fulton, J. P.; Wincheski, B.; Nath, S.; Namkung, M.

    1993-01-01

    Rapid inspection of aircraft structures for flaws is of vital importance to the commercial and defense aircraft industry. In particular, inspecting thin aluminum structures for flaws is the focus of a large scale R&D effort in the nondestructive evaluation (NDE) community. Traditional eddy current methods used today are effective, but require long inspection times. New electromagnetic techniques which monitor the normal component of the magnetic field above a sample due to a sheet of current as the excitation, seem to be promising. This paper is an attempt to understand and analyze the magnetic field distribution due to a current sheet above an aluminum test sample. A simple theoretical model, coupled with a two dimensional finite element model (FEM) and experimental data will be presented in the next few sections. A current sheet above a conducting sample generates eddy currents in the material, while a sensor above the current sheet or in between the two plates monitors the normal component of the magnetic field. A rivet or a surface flaw near a rivet in an aircraft aluminum skin will disturb the magnetic field, which is imaged by the sensor. Initial results showed a strong dependence of the flaw induced normal magnetic field strength on the thickness and conductivity of the current-sheet that could not be accounted for by skin depth attenuation alone. It was believed that the eddy current imaging method explained the dependence of the thickness and conductivity of the flaw induced normal magnetic field. Further investigation, suggested the complexity associated with the mutual inductance of the system needed to be studied. The next section gives an analytical model to better understand the phenomenon.

  9. Growth of Hollow Transition Metal (Fe, Co, Ni) Oxide Nanoparticles on Graphene Sheets through Kirkendall Effect as Anodes for High-Performance Lithium-Ion Batteries.

    PubMed

    Yu, Xianbo; Qu, Bin; Zhao, Yang; Li, Chunyan; Chen, Yujin; Sun, Chunwen; Gao, Peng; Zhu, Chunling

    2016-01-26

    A general strategy based on the nanoscale Kirkendall effect has been developed to grow hollow transition metal (Fe, Co or Ni) oxide nanoparticles on graphene sheets. When applied as lithium-ion battery anodes, these hollow transition metal oxide-based composites exhibit excellent electrochemical performance, with high reversible capacities and long-term stabilities at a high current density, superior to most transition metal oxides reported to date. PMID:26502895

  10. In-situ stress analysis with X-Ray diffraction for yield locus characterization of sheet metals

    SciTech Connect

    Güner, A.; Tekkaya, A. E.; Zillmann, B.; Lampke, T.

    2013-12-16

    A main problem in the field of sheet metal characterization is the inhomogeneous plastic deformation in the gauge regions of specimens which causes the analytically calculated stresses to differ from the sought state of stress acting in the middle of the gauge region. To overcome this problem, application of X-Ray diffraction is analyzed. For that purpose a mobile X-ray diffractometer and an optical strain measurement system are mounted on a universal tensile testing machine. This enables the recording of the whole strain and stress history of a material point. The method is applied to uniaxial tension tests, plane strain tension tests and shear tests to characterize the interstitial free steel alloy DC06. The applicability of the concepts of stress factors is verified by uniaxial tension tests. The experimentally obtained values are compared with the theoretical values calculated with crystal elasticity models utilizing the orientation distribution functions (ODF). The relaxation problem is addressed which shows itself as drops in the stress values with the strain kept at a constant level. This drop is analyzed with elasto-viscoplastic material models to correct the measured stresses. Results show that the XRD is applicable to measure the stresses in sheet metals with preferred orientation. The obtained yield locus is expressed with the Yld2000–2D material model and an industry oriented workpiece is analyzed numerically. The comparison of the strain distribution on the workpiece verifies the identified material parameters.

  11. In-situ stress analysis with X-Ray diffraction for yield locus characterization of sheet metals

    NASA Astrophysics Data System (ADS)

    Güner, A.; Zillmann, B.; Lampke, T.; Tekkaya, A. E.

    2013-12-01

    A main problem in the field of sheet metal characterization is the inhomogeneous plastic deformation in the gauge regions of specimens which causes the analytically calculated stresses to differ from the sought state of stress acting in the middle of the gauge region. To overcome this problem, application of X-Ray diffraction is analyzed. For that purpose a mobile X-ray diffractometer and an optical strain measurement system are mounted on a universal tensile testing machine. This enables the recording of the whole strain and stress history of a material point. The method is applied to uniaxial tension tests, plane strain tension tests and shear tests to characterize the interstitial free steel alloy DC06. The applicability of the concepts of stress factors is verified by uniaxial tension tests. The experimentally obtained values are compared with the theoretical values calculated with crystal elasticity models utilizing the orientation distribution functions (ODF). The relaxation problem is addressed which shows itself as drops in the stress values with the strain kept at a constant level. This drop is analyzed with elasto-viscoplastic material models to correct the measured stresses. Results show that the XRD is applicable to measure the stresses in sheet metals with preferred orientation. The obtained yield locus is expressed with the Yld2000-2D material model and an industry oriented workpiece is analyzed numerically. The comparison of the strain distribution on the workpiece verifies the identified material parameters.

  12. Battery with a microcorrugated, microthin sheet of highly porous corroded metal

    DOEpatents

    LaFollette, Rodney M.

    2005-09-27

    Microthin sheet technology is disclosed by which superior batteries are constructed which, among other things, accommodate the requirements for high load rapid discharge and recharge, mandated by electric vehicle criteria. The microthin sheet technology has process and article overtones and can be used to form thin electrodes used in batteries of various kinds and types, such as spirally-wound batteries, bipolar batteries, lead acid batteries silver/zinc batteries, and others. Superior high performance battery features include: (a) minimal ionic resistance; (b) minimal electronic resistance; (c) minimal polarization resistance to both charging and discharging; (d) improved current accessibility to active material of the electrodes; (e) a high surface area to volume ratio; (f) high electrode porosity (microporosity); (g) longer life cycle; (h) superior discharge/recharge characteristics; (i) higher capacities (A.multidot.hr); and (j) high specific capacitance.

  13. Noise-Induced Hearing Loss in Korean Workers: Co-Exposure to Organic Solvents and Heavy Metals in Nationwide Industries

    PubMed Central

    Choi, Yoon-Hyeong; Kim, KyooSang

    2014-01-01

    Background Noise exposure is a well-known contributor to work-related hearing loss. Recent biological evidence suggests that exposure to ototoxic chemicals such as organic solvents and heavy metals may be additional contributors to hearing loss. However, in industrial settings, it is difficult to determine the risks of hearing loss due to these chemicals in workplaces accompanied by excessive noise exposure. A few studies suggest that the effect of noise may be enhanced by ototoxic chemicals. Therefore, this study investigated whether co-exposure to organic solvents and/or heavy metals in the workplace modifies the risk of noise exposure on hearing loss in a background of excessive noise. Methods We examined 30,072 workers nationwide in a wide range of industries from the Korea National Occupational Health Surveillance 2009. Data on industry-based exposure (e.g., occupational noise, heavy metals, and organic solvents) and subject-specific health outcomes (e.g., audiometric examination) were collected. Noise was measured as the daily 8-h time-weighted average level. Air conduction hearing thresholds were measured from 0.5 to 6 kHz, and pure-tone averages (PTA) (i.e., means of 2, 3, and 4 kHz) were computed. Results In the multivariate linear model, PTA increment with occupational noise were 1.64-fold and 2.15-fold higher in individuals exposed to heavy metals and organic solvents than in unexposed individuals, respectively. Conclusion This study provides nationwide evidence that co-exposure to heavy metals and/or organic solvents may exacerbate the effect of noise exposure on hearing loss in workplaces. These findings suggest that workers in industries dealing with heavy metals or organic solvents are susceptible to such risks. PMID:24870407

  14. Numerical Modeling of Magnesium Alloy Sheet Metal Forming at Elevated Temperature

    SciTech Connect

    Lee, Myeong-Han; Oh, Soo-Ik; Kim, Heon-Young; Kim, Hyung-Jong; Choi, Yi-Chun

    2007-05-17

    The development of light-weight vehicle is in great demand for enhancement of fuel efficiency and dynamic performance. The vehicle weight can be reduced effectively by using lightweight materials such as magnesium alloys. However, the use of magnesium alloys in sheet forming processes is still limited because of their low formability at room temperature and the lack of understanding of the forming process of magnesium alloys at elevated temperatures. In this study, uniaxial tensile tests of the magnesium alloy AZ31B-O at various temperatures were performed to evaluate the mechanical properties of this alloy relevant for forming of magnesium sheets. To construct a FLD (forming limit diagram), a forming limit test were conducted at temperature of 100 and 200 deg. C. For the evaluation of the effects of the punch temperature on the formability of a rectangular cup drawing with AZ31B-O, numerical modelling was conducted. The experiment results indicate that the stresses and possible strains of AZ31B-O sheets largely depend on the temperature. The stress decreases with temperature increase. Also, the strain increase with temperature increase. The numerical modelling results indicate that formability increases with the decrease in the punch temperature at the constant temperature of the die and holder.

  15. Microstructural and failure characteristics of metal-lntermetallic layered sheet composites

    NASA Astrophysics Data System (ADS)

    Alman, D. E.; Rawers, J. C.; Hawk, J. A.

    1995-03-01

    A processing technique for the fabrication of layered metal-intermetallic composites is presented, in which a self-propagating, high-temperature synthesis reaction (SHS) was initiated at the interface between dissimilar elemental metal foils. The resultant composite microstructure consisted of a fully dense, well-bonded metal-intermetallic layered composite. In this United States Bureau of Mines study, metal (Fe, Ni, or Ti) foils were reacted with Al foils to produce metal-metal aluminide layered composites. Tensile tests conducted at room temperature revealed that composites could be designed to behave in a high-strength and high-toughness manner by altering the thicknesses of the starting elemental foils. Failure characteristics revealed that the processes that govern ductile vs brittle behavior of the composites occur early in the fracture.

  16. Municipal waste incinerators: air and biological monitoring of workers for exposure to particles, metals, and organic compounds

    PubMed Central

    Maitre, A; Collot-Fertey, D; Anzivino, L; Marques, M; Hours, M; Stoklov, M

    2003-01-01

    Aims: To evaluate occupational exposure to toxic pollutants at municipal waste incinerators (MWIs). Methods: Twenty nine male subjects working near the furnaces in two MWIs, and 17 subjects not occupationally exposed to combustion generated pollutants were studied. Individual air samples were taken throughout the shift; urine samples were collected before and after. Stationary air samples were taken near potential sources of emission. Results: Occupational exposure did not result in the infringement of any occupational threshold limit value. Atmospheric exposure levels to particles and metals were 10–100 times higher in MWIs than at the control site. The main sources were cleaning operations for particles, and residue transfer and disposal operations for metals. MWI workers were not exposed to higher levels of polycyclic aromatic hydrocarbons than workers who are routinely in contact with vehicle exhaust. The air concentrations of volatile organic compounds and aldehydes were low and did not appear to pose any significant threat to human health. Only the measurement of chlorinated hydrocarbon levels would seem to be a reliable marker for the combustion of plastics. Urine metal levels were significantly higher at plant 1 than at plant 2 because of high levels of pollutants emanating from one old furnace. Conclusion: While biological monitoring is an easy way of acquiring data on long term personal exposure, air monitoring remains the only method that makes it possible to identify the primary sources of pollutant emission which need to be controlled if occupational exposure and environmental pollution are to be reduced. PMID:12883016

  17. Springback control in sheet metal bending by laser-assisted bending: Experimental analysis, empirical and neural network modelling

    NASA Astrophysics Data System (ADS)

    Gisario, A.; Barletta, M.; Conti, C.; Guarino, S.

    2011-12-01

    The present investigation deals with the control of springback phenomena in the bending process of aluminium sheets by hybrid forming process. Metal substrates were pre-bent to nominal shapes on a built-ad-hoc mould after being constrained on it. Then, they were post-treated by high power diode laser to prevent the deformation of the pre-bent sheets after the release of the constraints. The extent of springback phenomena were estimated by measuring the difference between the nominal bending angles and those achieved on the unconstrained substrates after laser post-treatments. Analytical models, aimed at predicting the springback by varying the setting of the operational parameters of the forming process, were developed. Neural network solutions were also proposed to improve the matching between experimental and numerical data, with the Multi-Layer Perceptrons trained by Back-Propagation algorithm being the fittest one. On this basis, a control modulus very useful to practitioners for automation and simulation purposes was built-on.

  18. Combined crystal plasticity and phase-field method for recrystallization in a process chain of sheet metal production

    NASA Astrophysics Data System (ADS)

    Vondrous, Alexander; Bienger, Pierre; Schreijäg, Simone; Selzer, Michael; Schneider, Daniel; Nestler, Britta; Helm, Dirk; Mönig, Reiner

    2015-02-01

    In sheet metal production, a typical process chain contains hot rolling, cold rolling and annealing as a sequence of consecutive processing steps. We investigate the grain structure evolution of body centered cubic low carbon steel and focus on recrystallization, by employing different computational methods which operate across the process chain and across length scales. In particular, we combine finite element crystal plasticity with phase-field simulations to study the effect of deformation of the grain structure by hot and cold rolling on recrystallization during annealing. The overall goal is to represent the most important technological quantities such as texture evolution and the fraction of recrystallization. The results of grain quantities are validated by a comparison of the orientation distribution functions with experimental electron backscatter measurements. The coupling of the simulation methods has shown that the effects of recrystallization can be recovered well, depending on the preceding processing conditions.

  19. Analysis of hardening behavior of sheet metals by a new simple shear test method taking into account the Bauschinger effect

    NASA Astrophysics Data System (ADS)

    Bang, Sungsik; Rickhey, Felix; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo

    2013-12-01

    In this study we establish a process to predict hardening behavior considering the Bauschinger effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Bauschinger effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with FEA. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.

  20. Massachusetts Beryllium Screening Program for Former Workers of Wyman-Gordon, Norton Abrasives, and MIT/Nuclear Metals

    SciTech Connect

    Pepper, L. D.

    2008-05-21

    The overall objective of this project was to provide medical screening to former workers of Wyman-Gordon Company, Norton Abrasives, and MIT/Nuclear Metals (NMI) in order to prevent and minimize the health impact of diseases caused by site related workplace exposures to beryllium. The program was developed in response to a request by the U.S. Department of Energy (DOE) that had been authorized by Congress in Section 3162 of the 1993 Defense Authorization Act, urging the DOE to carry out a program for the identification and ongoing evaluation of current and former DOE employees who are subjected to significant health risks during such employment." This program, funded by the DOE, was an amendment to the medical surveillance program for former DOE workers at the Nevada Test Site (NTS). This program's scope included workers who had worked for organizations that provided beryllium products or materials to the DOE as part of their nuclear weapons program. These organizations have been identified as Beryllium Vendors.

  1. Levels of some trace metals and related enzymes in workers at storage-battery factories in Iraq.

    PubMed

    Mehdi, J K; al-Imarah, F J; al-Suhail, A A

    2000-01-01

    Levels of some trace metals (copper, iron, lead and zinc), aminolevulinate dehydratase (ALAD), caeruloplasmin and haemoglobin were measured in the blood of 37 male workers from private-sector storage-battery factories. The men were divided into three groups depending on their jobs: 11 chargers (group I), 8 repair workers (group II) and 18 casting workers (group III); 60 men were selected as controls. Mean levels were 14.63, 36.35, 58.00 and 71.70 micrograms/100 mL for lead, 192.54, 133.90, 96.75 and 45.37 U/mL for ALAD, and 14.02, 12.72, 12.20 and 11.40 g/100 mL for haemoglobin for control and groups I, II and III respectively. Significant negative correlations were found between lead and both ALAD and haemoglobin. The only significant positive correlation was between lead levels and duration of exposure. PMID:11370344

  2. Structural, electronic and magnetic properties of 3d transition metals embedded graphene-like carbon nitride sheet: A DFT + U study

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Chi, Runze; Li, Chong; Jia, Yu

    2016-03-01

    Using first-principles calculations, we have investigated the structural, electronic and magnetic properties of 3d transition-metals (TMs) embedded two dimensional graphene-like carbon nitride sheet (TMs@g-CN). Our results show that TMs embed in the cavity of g-CN sheet regularly and keep intact of the planar structure, though there is Jahn-Teller distortion inevitably. Additionally, the nonmagnetic and semiconducting sheet can be significantly modulated to be magnetic and metallic behaviors induced by the resonant impurity states between TMs 3d and g-CN 2p orbitals. Moreover, we also explore the magnetic coupling of TMs@g-CN and find that it varies dramatically with the change of the distance between TMs, i.e., from ferromagnetic (FM) to antiferromagnetic (AFM) transition. Finally, the underlying physical mechanism of the above findings is discussed.

  3. 76 FR 5839 - Investigations Regarding Certifications of Eligibility To Apply for Worker Adjustment Assistance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-02

    .../07/11 75076 Sheet Metal Workers Local Southfield, MI........ 01/10/11 12/20/10 80 (Workers). 75077 Dama Jewelry Technology, Johnston, RI 01/10/11 01/07/11 Inc. (Company). 75078 NGK Spark Plugs (USA... 01/13/11 10/22/10 (Company). 75098 IBM (Company) Research Triangle 01/14/11 01/10/11 Park, NC....

  4. Numerical Method to Analyze Local Stiffness of the Workpiece to avoid Rebound During Electromagnetic Sheet Metal Forming

    SciTech Connect

    Risch, Desiree; Brosius, Alexander; Psyk, Verena; Kleiner, Matthias

    2007-04-07

    Electromagnetic sheet metal forming is a high speed forming process using pulsed magnetic fields to form metals with high electrical conductivity such as aluminum. Thereby, workpiece velocities of more than 300 m/s are achievable, which can cause difficulties when forming into a die: the kinetic energy, which is related to the workpiece velocity, must dissipate in a short time slot when the workpiece hits the die; otherwise undesired effects, for example rebound, can occur. One possibility to handle this shortcoming is to locally increase the stiffness of the workpiece. In order to be able to estimate the local stiffness a method is presented which is based on a modal analysis by means of the Finite-Element-Method. For this reason, it is necessary to fractionize the considered geometries into a part-dependent number of segments. These are subsequently analyzed separately to determine regions of low geometrical stiffness. Combined with the process knowledge concerning the velocity distribution within the workpiece over the time, a prediction of the feasibility of the forming process and a target-oriented design of the workpiece geometry will be possible. Numerical results are compared with experimental investigations.

  5. The electronic properties of bare and alkali metal adsorbed two-dimensional GeSi alloy sheet

    NASA Astrophysics Data System (ADS)

    Qiu, Wenhao; Ye, Han; Yu, Zhongyuan; Liu, Yumin

    2016-09-01

    In this paper, the structural and electronic properties of both bare and alkali metal (AM) atoms adsorbed two-dimensional GeSi alloy sheet (GeSiAS) are investigated by means of first-principles calculations. The band gaps of bare GeSiAS are shown slightly opened at Dirac point with the energy dispersion remain linear due to the spin-orbit coupling effect at all concentrations of Ge atoms. For metal adsorption, AM atoms (including Li, Na and K) prefer to occupy the hexagonal hollow site of GeSiAS and the primary chemical bond between AM adatom and GeSiAS is ionic. The adsorption energy has an increase tendency with the increase of the Ge concentration in supercell. Besides, single-side adsorption of AM atoms introduces band gap at Dirac point, which can be tuned by the Ge concentration and the species of AM atoms. The strong relation between the band gaps and the distribution of Si and Ge atoms inside GeSiAS are also demonstrated. The opened band gaps of AM covered GeSiAS range from 14.8 to 269.1 meV along with the effective masses of electrons ranging from 0.013 to 0.109 me, indicating the high tunability of band gap as well as high mobility of carriers. These results provide a development in two-dimensional alloys and show potential applications in novel micro/nano-electronic devices.

  6. Fatigue properties of sheet, bar, and cast metallic materials for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Green, E. F.

    1970-01-01

    Cryogenic fatigue and tensile properties for metallic materials are determined in the operating life-time range of ten thousand to ten million cycles at room temperature, at minus 320 degrees F, and at minus 423 degrees F. Results are presented as stress versus number of cycles to failure.

  7. Continuous process for forming sheet metal from an alloy containing non-dendritic primary solid

    DOEpatents

    Flemings, Merton C.; Matsuniya, Tooru

    1983-01-01

    A homogeneous mixture of liquid-solid metal is shaped by passing the composition from an agitation zone onto a surface moving relative to the exit of the agitation zone. A portion of the composition contacting the moving surface is solidified and the entire composition then is formed.

  8. An investigation on co-axial water-jet assisted fiber laser cutting of metal sheets

    NASA Astrophysics Data System (ADS)

    Madhukar, Yuvraj K.; Mullick, Suvradip; Nath, Ashish K.

    2016-02-01

    Water assisted laser cutting has received significant attention in recent times with assurance of many advantages than conventional gas assisted laser cutting. A comparative study between co-axial water-jet and gas-jet assisted laser cutting of thin sheets of mild steel (MS) and titanium (Ti) by fiber laser is presented. Fiber laser (1.07 μm wavelength) was utilised because of its low absorption in water. The cut quality was evaluated in terms of average kerf, projected dross height, heat affected zone (HAZ) and cut surface roughness. It was observed that a broad range process parameter could produce consistent cut quality in MS. However, oxygen assisted cutting could produce better quality only with optimised parameters at high laser power and high cutting speed. In Ti cutting the water-jet assisted laser cutting performed better over the entire range of process parameters compared with gas assisted cutting. The specific energy, defined as the amount of laser energy required to remove unit volume of material was found more in case of water-jet assisted laser cutting process. It is mainly due to various losses associated with water assisted laser processing such as absorption of laser energy in water and scattering at the interaction zone.

  9. Integral sheet metal design via severe plastic deformation - state of the art and future challenges

    NASA Astrophysics Data System (ADS)

    Bruder, E.; Kaune, V.; Müller, C.

    2014-08-01

    The innovative forming processes Linear Flow Splitting (LFS) and Linear Bend Splitting (LBS) were developed to facilitate the continuous production of branched profiles with tailored sheet thickness by inducing severe plastic strain. In contrast to most SPD processes the stress state in LFS and LBS is very complex and plastic deformation is confined to limited volumes which results in steep strain gradients and consequently ultrafine grained (UFG) gradient microstructures. Even though the processes have been commercialized, the increased lightweight potential that originates from the local grain refinement remains mostly idle since it is neither fully understood nor easily assessable yet. The present work shows the state of the art for the LFS and LBS processes and compares the microstructures and distribution of mechanical properties for different steels processed with different LFS parameters. The data is used to identify characteristic manufacturing induced properties that are insensitive to processing parameters. Based on the experimental results a material flow model for the processing zone is proposed which is discussed with respect to the current understanding of plasticity at severe strains.

  10. A DFT investigation of CO adsorption on VIIIB transition metal-doped graphene sheets

    NASA Astrophysics Data System (ADS)

    Wanno, Banchob; Tabtimsai, Chanukorn

    2014-03-01

    Adsorptions of CO on pristine, Fe-, Ru-, Os-, Co-, Rh-, Ir-, Ni-, Pd-, and Pt-doped graphene were investigated, using density functional theory calculation at B3LYP/LanL2DZ theoretical level. This work revealed that the transition metal doped graphenes were more highly sensitive to CO adsorption than that of pristine graphene. The Os- and Fe-doped graphenes displayed the strongest interaction with C and O atoms of CO molecule, respectively.

  11. A Study on Flexural Properties of Sandwich Structures with Fiber/Metal Laminate Face Sheets

    NASA Astrophysics Data System (ADS)

    Dariushi, S.; Sadighi, M.

    2013-10-01

    In this work, a new family of sandwich structures with fiber metal laminate (FML) faces is investigated. FMLs have benefits over both metal and fiber reinforced composites. To investigate the bending properties of sandwich beams with FML faces and compare with similar sandwich beams with fibrous composite faces, 6 groups of specimen with different layer arrangements were made and tested. Results show that FML faces have good resistance against transverse local loads and minimize stress concentration and local deformations of skin and core under the loading tip. In addition, FML faces have a good integrity even after plateau region of foam cores and prevent from catastrophic failures, which cannot be seen in fibrous composite faces. Also, FML faces are lighter than metal faces and have better connection with foam cores. Sandwich beams with FML faces have a larger elastic region because of simultaneous deformation of top and bottom faces and larger failure strain thanks to good durability of FMLs. A geometrical nonlinear classical theory is used to predict force-deflection behavior. In this model an explicit formula between symmetrical sandwich beams deflections and applied force which can be useful for designers, is derived. Good agreement is obtained between the analytical predictions and experimental results. Also, analytical results are compared with small deformation solution in a parametric study, and the effects of geometric parameters on difference between linear and nonlinear results are discussed.

  12. Sheet-metal Worker (any ind.) 804.281 -- Technical Report on Development of USTES Aptitude Test Battery.

    ERIC Educational Resources Information Center

    Manpower Administration (DOL), Washington, DC. U.S. Training and Employment Service.

    The United States Training and Employment Service General Aptitude Test Battery (GATB), first published in 1947, has been included in a continuing program of research to validate the tests against success in many different occupations. The GATB consists of 12 tests which measure nine aptitudes: General Learning Ability; Verbal Aptitude; Numerical…

  13. Cyclic Bending and Stationary Drawing Deformation of Metal Sheets : Experiments and Associated Numerical Simulations

    SciTech Connect

    Moreira, L.P.; Romao, E.C.; Vieira, L.C.A.; Ferron, G.; Sampaio, A.P.

    2005-08-05

    A simple bend-draw experimental device is employed to analyze the behavior of narrow strips submitted to a nearly cyclic bending deformation mode followed by a steady state drawing. In this bending-drawing experiment, the strip is firstly bent over a central bead and two lateral beads by applying a controlled holding load and then is pulled out of device throughout the bead radii by a drawing load. The apparatus is mounted in a standard tensile test machine where the holding and drawing loads are recorded with an acquisition data system. The specimen is a rectangular strip cut with 320 mm long and 7 mm wide. The longitudinal (1) and width (w) strip plastic strains are determined from two hardness marks 120 mm spaced whereas the corresponding thickness (t) strain is obtained by volume conservation. Previous experiments showed a correlation between the plastic strain ({epsilon}w/{epsilon}t)BD resulting from the bending-drawing and the Lankford R-values obtained from the uniaxial tensile test. However, previous 3D numerical simulations based upon Hill's quadratic and Ferron's yield criteria revealed a better correlation between the ({epsilon}w/{epsilon}t)BD and the stress ratio {sigma}PS/{sigma}({alpha}), where {sigma}PS stands for the plane-strain tension yield stress and {sigma}({alpha}) for the uniaxial yield stress in uniaxial tension along the drawing direction making an angle {alpha} with the rolling direction. In the present work, the behavior of an IF steel sheet is firstly evaluated by means of uniaxial tensile and drawing-bending experiments conducted at every 15 degrees with respect to the rolling direction. Afterwards, the bending-drawing experiment is investigated with the commercial finite element (FE) code ABAQUS/Standard in an attempt to assess the influence of cyclic loadings upon the bending-drawing strain-ratios.

  14. Change and anisotropy of elastic modulus in sheet metals due to plastic deformation

    NASA Astrophysics Data System (ADS)

    Ishitsuka, Yuki; Arikawa, Shuichi; Yoneyama, Satoru

    2015-03-01

    In this study, the effect of the plastic deformation on the microscopic structure and the anisotropy of the elastic modulus in the cold-rolled steel sheet (SPCC) is investigated. Various uniaxial plastic strains (0%, 2.5%, 5%, 7.5%, and 10%) are applied to the annealed SPCC plates, then, the specimens for the tensile tests are cut out from them. The elastic moduli in the longitudinal direction and the transverse direction to the direction that are pre-strained are measured by the tensile tests. Cyclic tests are performed to investigate the effects of the internal friction caused by the movable dislocations in the elastic deformation. Also, the movable dislocations are quantified by the boundary tracking for TEM micrographs. In addition, the behaviors of the change of the elastic modulus in the solutionized and thermal aged aluminum alloy (A5052) are measured to investigate the effect on the movable dislocations with the amount of the depositions. As a result in SPCC, the elastic moduli of the 0° and 90° directions decrease more than 10% as 10% prestrain applied. On the other hand, the elastic modulus shows the recovery behavior after the strain aging and the annealing. The movable dislocation and the internal friction show a tendency to increase as the plastic strain increases. The marked anisotropy is not observed in the elastic modulus and the internal friction. The elastic modulus in A5052 with many and few depositions decreases similarly by the plastic deformation. From the above, the movable dislocations affect the elastic modulus strongly without depending on the deposition amount. Moreover, the elastic modulus recovers after the plastic deformation by reducing the effects of them with the strain aging and the heat treatment.

  15. Multi-level modeling for sensitivity assessment of springback in sheet metal forming

    NASA Astrophysics Data System (ADS)

    Lebon, J.; Lequilliec, G.; Coelho, R. Filomeno; Breitkopf, P.; Villon, P.

    2013-05-01

    In this work, we highlight that sensitivity analysis of metal forming process requires both high precision and low cost numerical models. We propose a two-pronged methodology to address these challenges. The deep drawing simulation process is performed using an original low cost semi-analytical approach based on a bending under tension model (B-U-T) with a good accuracy for small random perturbations of the physical and process parameters. The springback sensitivity analysis is based on the Sobol indices approach and performed using an non intrusive efficient methodology based on the post-treatment of the polynomial chaos coefficients.

  16. Search for giant magnetic anisotropy in transition-metal dimers on defected hexagonal boron nitride sheet.

    PubMed

    Li, J; Wang, H; Hu, J; Wu, R Q

    2016-05-28

    Structural and magnetic properties of many transition-metal dimers embedded in a defected hexagonal boron nitride monolayer are investigated through density functional calculations to search for systems with magnetic anisotropy energies (MAEs) larger than 30meV. In particular, Ir-Ir@Dh-BN is found to have both large MAE (∼126 meV) and high structural stability against dissociation and diffusion, and it hence can serve as magnetic unit in spintronics and quantum computing devices. This giant MAE mainly results from the spin orbit coupling and the magnetization of the upper Ir atom, which is in a rather isolated environment. PMID:27250322

  17. Search for giant magnetic anisotropy in transition-metal dimers on defected hexagonal boron nitride sheet

    NASA Astrophysics Data System (ADS)

    Li, Jie; Wang, Hui; Hu, Jun; Wu, Ruqian

    For a magnetic units at the nanometer scale, one of the most important issues is how to hold thermal fluctuation of its magnetization, i.e., how to enhance its blocking temperature (TB) to above 300K. Through systematic density functional calculations, the structural stability and magnetic properties of many transition-metal dimers embedded in a defected hexagonal boron nitride monolayer are investigated. We find twelve cases that may have magnetic anisotropy energies (MAEs) larger than 30 meV. In particular, Ir-Ir@Dh-BN has both large MAE (~126 meV) and high structural stability, which makes it a promising candidate of magnetic unit in spintronics and quantum computing devices. Work at Fudan was supported by the Chinese National Science Foundation (11474056) and National Basic Research Program of China (2015CB921400). Work at UCI was supported by DOE-BES (Grant No. DE-FG02-05ER46237).

  18. Mica sheets with embedded metal nanorods: Chemical imaging in a topographically smooth structure

    SciTech Connect

    Graca, Malgorzata; Turner, Jeff; Marshall, Michael; Granick, Steve

    2007-09-15

    We demonstrate the concept to combine topographical smoothness and plasmonic properties to produce flat substrates with surface enhanced Raman spectroscopy activity--properties that may find use in nanotribology and other thin film applications. Preliminary findings to this end are described. A dual-beam focused ion beam (FIB) system is used to drill large arrays of small pores in single crystals of mica, 2-6 {mu}m thick, yielding controlled cross sections (squares, triangles, and circles), sizes (100 nm to many microns), and arrangements (square, hexagonal, and random). When filled with metals, arrays result to embedded nanorods with their long axis oriented normal to the surface. As an extension of this method, arrays of nanorods standing perpendicular to a supporting surface can also be produced.

  19. On the modelling of complex kinematic hardening and nonquadratic anisotropic yield criteria at finite strains: application to sheet metal forming

    NASA Astrophysics Data System (ADS)

    Grilo, Tiago J.; Vladimirov, Ivaylo N.; Valente, Robertt A. F.; Reese, Stefanie

    2016-02-01

    In the present paper, a finite strain model for complex combined isotropic-kinematic hardening is presented. It accounts for finite elastic and finite plastic strains and is suitable for any anisotropic yield criterion. In order to model complex cyclic hardening phenomena, the kinematic hardening is described by several back stress components. To that end, a new procedure is proposed in which several multiplicative decompositions of the plastic part of the deformation gradient are considered. The formulation incorporates a completely general format of the yield function, which means that any yield function can by employed by following a procedure that ensures the principle of material frame indifference. The constitutive equations are derived in a thermodynamically consistent way and numerically integrated by means of a backward-Euler algorithm based on the exponential map. The performance of the constitutive model is assessed via numerical simulations of industry-relevant sheet metal forming processes (U-channel forming and draw/re-draw of a panel benchmarks), the results of which are compared to experimental data. The comparison between numerical and experimental results shows that the use of multiple back stress components is very advantageous in the description of springback. This holds in particular if one carries out a comparison with the results of using only one component. Moreover, the numerically obtained results are in excellent agreement with the experimental data.

  20. Effect of strain rate on shear properties and fracture characteristics of DP600 and AA5182-O sheet metal alloys

    NASA Astrophysics Data System (ADS)

    Rahmaan, Taamjeed; Butcher, Cliff; Abedini, Armin; Worswick, Michael

    2015-09-01

    Shear tests were performed at strain rates ranging from quasi-static (.01 s-1) to 600 s-1 for DP600 steel and AA5182-O sheet metal alloys at room temperature. A miniature sized shear specimen was modified and validated in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments, and a criterion to detect the onset of fracture based on the hardening rate of the materials is proposed. At equivalent strains greater than 20%, the DP600 and AA5182 alloys demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the DP600 shows positive rate sensitivity while the AA5182 was not sensitive to strain rate. For both alloys, the equivalent fracture strain and elongation to failure decreased with strain rate. A conversion of the shear stress to an equivalent stress using the von Mises yield criterion provided excellent agreement with the results from tensile tests at elevated strain rates. Unlike the tensile test, the shear test is not limited by the onset of necking so the equivalent stress can be determined over a larger range of strain.

  1. On the modelling of complex kinematic hardening and nonquadratic anisotropic yield criteria at finite strains: application to sheet metal forming

    NASA Astrophysics Data System (ADS)

    Grilo, Tiago J.; Vladimirov, Ivaylo N.; Valente, Robertt A. F.; Reese, Stefanie

    2016-06-01

    In the present paper, a finite strain model for complex combined isotropic-kinematic hardening is presented. It accounts for finite elastic and finite plastic strains and is suitable for any anisotropic yield criterion. In order to model complex cyclic hardening phenomena, the kinematic hardening is described by several back stress components. To that end, a new procedure is proposed in which several multiplicative decompositions of the plastic part of the deformation gradient are considered. The formulation incorporates a completely general format of the yield function, which means that any yield function can by employed by following a procedure that ensures the principle of material frame indifference. The constitutive equations are derived in a thermodynamically consistent way and numerically integrated by means of a backward-Euler algorithm based on the exponential map. The performance of the constitutive model is assessed via numerical simulations of industry-relevant sheet metal forming processes (U-channel forming and draw/re-draw of a panel benchmarks), the results of which are compared to experimental data. The comparison between numerical and experimental results shows that the use of multiple back stress components is very advantageous in the description of springback. This holds in particular if one carries out a comparison with the results of using only one component. Moreover, the numerically obtained results are in excellent agreement with the experimental data.

  2. Study on the Hemisphere Deep Drawing Process of Metal Sheet Based on the FEM Simulation

    SciTech Connect

    Tzou, G.-Y.; Hwang, Y.-M.; Hu, H.-L.; Chien, W.-T.; Hu, J.-J.

    2007-05-17

    Deep drawing is a manner of the metal forming, and the most important position in the industry has been occupied because of its high efficiency. In the past, people often used a trial-and-error method and experiences to complete the deep drawing processes. However the time is consuming and the cost is high by this way, so this study adopts the finite element method to simulate the deep drawing forming in order to reduce the processing cost and time, furthermore to predict the thickness distribution of the product and to find the suitable forming parameters. The material properties and forming parameters have the significant influences to the deep drawing forming, such as strain hardening, plastic strain rate, friction and lubrication, blank holder force, radii of die and punch etc. In this study, two popular commercial FEA software, SUPERFORM and DEFORM, have been used to simulate hemisphere deep drawing forming, and the analysis results will be in comparison with experiment results published to verify the correctness of FEM simulations. Throughout this study, the effects of the blank holder force, the radii of die and punch, the gap between punch and die, the frictional coefficient etc upon the maximum forming force and the minimum thickness, are discussed systematically. After a series of simulations, the comparisons between the SUPERFORM and DEFORM show a good agreement with the experiment and the error is very small.

  3. Think regionally, act locally: metals in honeybee workers in the Netherlands (surveillance study 2008).

    PubMed

    van der Steen, J J M; Cornelissen, B; Blacquière, T; Pijnenburg, J E M L; Severijnen, M

    2016-08-01

    In June 2008, a surveillance study for metals in honeybees was performed in the Netherlands. Randomly, 150 apiaries were selected. In each apiary, five colonies were sampled. Per apiary, the hive samples were pooled. The apiary sample was analysed for Al, As, Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Sb, Se, Sn, Sr, Ti, V and Zn. All metals could be detected in all apiaries. As, Li, Sb, Sn and V were detected in part of the apiaries. The overall picture showed a regional pattern. In apiaries in the east of the Netherlands, Al, Ba, Cr, Mn, Mo, Ni, Se and Ti are found in higher concentrations compared to the west. In-region variation was demonstrated, indicating local effects. The vicinity of the apiaries was mapped afterwards and characterised as land uses of >50 % agricultural area, >50 % wooded area, >50 % urban area and mixed land use within a circle of 28 km(2) around the apiary. The results indicated that in apiaries located in >50 % wooded areas, significantly higher concentrations of Al, Ba, Cd, Cr, Cu, Li, Mn, Mo, Ni, Sb, Sr, Ti and Zn were found compared to agricultural, urban and mixed land use areas. We conclude that (1) the ratio between metal concentrations varies per region, demonstrating spatial differences, and (2) there is in-region local variation per metal. The results indicate the impact of land use on metal concentrations in honeybees. For qualitative bioindication studies, regional, local and land use effects should be taken into account. PMID:27406208

  4. Scalable synthesis of layer-controlled WS{sub 2} and MoS{sub 2} sheets by sulfurization of thin metal films

    SciTech Connect

    Orofeo, Carlo M.; Suzuki, Satoru; Sekine, Yoshiaki; Hibino, Hiroki

    2014-08-25

    Transition metal dichalcogenides (TMDs) have emerged as exciting 2D materials beyond graphene due to their promising applications in the field of electronics and optoelectronics. Hence, the ability to produce controllable and uniformly thick TMD sheets over a large area is of utmost important for large-scale applications. Here, a facile method of synthesizing large-area, layer-controlled WS{sub 2}, and MoS{sub 2} sheets by sulfurization of their corresponding thin metal films is reported. A metal film, which is deposited by magnetron sputtering method, can be adjusted to produce, with great control, the desired sheet thickness down to a monolayer. Various characterization techniques, such as Raman, photoluminescence, and transmission electron microscopy, were used to evaluate the grown films. The results confirmed some of the exotic properties of TMDs such as the thickness dependent band-gap transition (indirect to direct band gap) and Raman shift. Devices made directly on the as-grown film showed modest mobility, ranging from 0.005 to 0.01 cm{sup 2} V{sup −1}s{sup −1}. Our synthesis method is simple and could also be used to synthesize other TMDs.

  5. [FEATURES OF THE IMMUNE GENETIC PARAMETERS IN WORKERS IN NON-FERROUS METAL INDUSTRY].

    PubMed

    Dolgikh, O V; Krivtsov, A V; Lykhina, T S; Bubnova, O A; Lanin, D V; Vdovina, N A; Luzhetskiĭ, K P; Andreeva, E E

    2015-01-01

    There was performed a comparative analysis of immunogenetic indices in non-ferrous metallurgy employees under the exposure to different combinations of harmful occupational factors. The combined effect of chlorine and vanadium fumes, noise, overall vibration appeared to be associated with the gene polymorphism of cytokine regulation--VEGF and TNF (p < 0.05). In workers the combination offactors such as dust containing silicon dioxide, noise, elevated environmental thermal load was associated with cytochrome p450 gene polymorphism, allele variation ofwhich is formed owing to the homozygous genotype. At the same time there was observed an excess production of specific antibodies to vanadium and silicon, significantly differed from that of the indices in the reference group. There are proposed genetic (CYP1A1, VEGF TNFalfa) and immunological (IgG to vanadium and silicon) indices as markers of susceptibility and effect in health risk assessment of different combinations of harmful occupational factors, which will allow to increase the availability of laboratory control during surveillance activities at the objects. PMID:26155646

  6. Sensitivity Analysis of the Sheet Metal Stamping Processes Based on Inverse Finite Element Modeling and Monte Carlo Simulation

    SciTech Connect

    Yu Maolin; Du, R.

    2005-08-05

    Sheet metal stamping is one of the most commonly used manufacturing processes, and hence, much research has been carried for economic gain. Searching through the literatures, however, it is found that there are still a lots of problems unsolved. For example, it is well known that for a same press, same workpiece material, and same set of die, the product quality may vary owing to a number of factors, such as the inhomogeneous of the workpice material, the loading error, the lubrication, and etc. Presently, few seem able to predict the quality variation, not to mention what contribute to the quality variation. As a result, trial-and-error is still needed in the shop floor, causing additional cost and time delay. This paper introduces a new approach to predict the product quality variation and identify the sensitive design / process parameters. The new approach is based on a combination of inverse Finite Element Modeling (FEM) and Monte Carlo Simulation (more specifically, the Latin Hypercube Sampling (LHS) approach). With an acceptable accuracy, the inverse FEM (also called one-step FEM) requires much less computation load than that of the usual incremental FEM and hence, can be used to predict the quality variations under various conditions. LHS is a statistical method, through which the sensitivity analysis can be carried out. The result of the sensitivity analysis has clear physical meaning and can be used to optimize the die design and / or the process design. Two simulation examples are presented including drawing a rectangular box and drawing a two-step rectangular box.

  7. The effects of heavy metals and their interactions with polycyclic aromatic hydrocarbons on the oxidative stress among coke-oven workers.

    PubMed

    Wang, Tian; Feng, Wei; Kuang, Dan; Deng, Qifei; Zhang, Wangzhen; Wang, Suhan; He, Meian; Zhang, Xiaomin; Wu, Tangchun; Guo, Huan

    2015-07-01

    Heavy metals and polycyclic aromatic hydrocarbons (PAHs) are predominate toxic constituents of particulate air pollution that may be related to the increased risk of cardiopulmonary events. We aim to investigate the effects of the toxic heavy metals (arsenic, As; cadmium, Cd; chromium, Cr; nickel, Ni; and lead, Pb), and their interactions with PAHs on oxidative stress among coke-oven workers. A total of 1333 male workers were recruited in this study. We determined their urinary levels of As, Cd, Cr, Ni, Pb, twelve PAH metabolites, 8-hydroxydeoxyguanosine (8-OHdG), and 8-iso-prostaglandin-F2α (8-iso-PGF2α). Multivariate linear regression models were used to analyze the effects of these metals and their interactions with PAHs on 8-OHdG and 8-iso-PGF2α levels. It was found that only urinary As and Ni showed marginal or significant positive linear dose-dependent effects on 8-OHdG in this study population, especially among smokers (β=0.103, P=0.073 and β=0.110, P=0.002, respectively). After stratifying all participants by the quartiles of ΣOH-PAH, all five metals showed linear association with 8-OHdG in the highest quartile subgroup (Q4) of ΣOH-PAHs. However, these five urinary metals showed significantly consistent linear associations with 8-iso-PGF2α in all subjects and each stratum. Urinary ΣOH-PAHs can significant modify the effects of heavy metals on oxidative stress, while co-exposure to both high levels of ΣOH-PAHs and heavy metals render the workers with highest 8-OHdG and 8-iso-PGF2α (all P(interaction)≤0.005). This study showed evidence on the interaction effects of heavy metals and PAHs on increasing the oxidative stress, and these results warrant further investigation in more longitudinal studies. PMID:25956561

  8. Leptospirosis Seroprevalence Among Blue Metal Mine Workers of Tamil Nadu, India.

    PubMed

    Parveen, Sakkarai Mohamed Asha; Suganyaa, Baskar; Sathya, Muthu Sri; Margreat, Alphonse Asirvatham Princy; Sivasankari, Karikalacholan; Shanmughapriya, Santhanam; Hoffman, Nicholas E; Natarajaseenivasan, Kalimuthusamy

    2016-07-01

    Leptospirosis is mainly considered an occupational disease, prevalent among agriculture, sewage works, forestry, and animal slaughtering populations. However, putative risk to miners and their inclusion in the high-risk leptospirosis group remain in need of rigorous analysis. Therefore, a study was conducted with the objective to assess the leptospirosis seroprevalence among miners of two districts of Tamil Nadu, India. A total of 244 sera samples from Pudukkottai miners (124) and Karur miners (120) were analyzed by microscopic agglutination test. Antibodies to leptospires were detected in 94 samples giving an overall seroprevalence of 38.5%. The seroprevalence was higher among Pudukkottai miners (65.3%) when compared with Karur miners (10.8%). Seroprevalence among control population (13%) was significantly less than that of the Pudukkottai miners marking a possible high-risk population group distinction. Subject sera most commonly reacted with organisms of the serogroup Autumnalis, and the pattern was similar in carrier animals of the study areas. Two leptospires were isolated from kidney samples of rats. The prevalence of Autumnalis among rodents and humans source tracked human leptospirosis among the miners. The study also determined that Pudukkottai miners are subjected to high-risk challenges such as exposure to water bodies on the way to the mines (odds ratio [OR] = 10.6), wet mine areas (OR = 10.6), rat infestation (OR = 4.6), and cattle rearing (OR = 10.4) and are thus frequently exposed to leptospirosis compared with Karur miners. Hence, control strategies targeting these populations will likely to prove to be effective remediation strategies benefiting Pudukkottai miners and workers in similar environments across occupations. PMID:27044567

  9. Mortality of nickel workers: experience of men working with metallic nickel.

    PubMed Central

    Cox, J E; Doll, R; Scott, W A; Smith, S

    1981-01-01

    The mortality of men employed in a plant manufacturing nickel alloys from metallic nickel and other metals has been examined. The plant has operated since May 1953, and 1925 men were identified who had been employed in the operating areas at the plant, other than as members of the staff, for a total of five or more years, excluding breaks. Analysis of samples of air obtained from personal samplers showed that since 1975 most of the men are likely to have been exposed to average concentrations of nickel of between 0.5 and 0.9 mg Ni/m3. All but 22 (1.1%) of the men were successfully traced to 1 April 1978 or until they died or emigrated. One hundred and seventeen had died. The numbers of deaths observed from cancers of respiratory and other sites, other respiratory disease, ischaemic heart disease, and other causes of death were compared with the numbers expected from national and local mortality rates. No evidence of the existence of any occupational hazard was obtained. The number of deaths from lung cancer (15) in men employed for five years or more is small. At 98% of the number expected at local rates it is statistically compatible with risks of between 0.5 and 2.2 times "normal." PMID:7272235

  10. Metals fact sheet - Dysprosium

    SciTech Connect

    1997-01-01

    The article contains a summary of factors pertinent to dysprosium use. Geology and exploitation, mineral sources, production processes, global production,applications, and the dysprosium market are reviewed. Applications very briefly described include use as a cooling agent in nuclear control rods, magnets, magnetostrictive devices, phosphors, photoelectric devices, and glass. Current and historical market prices are given.