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Sample records for incremental sheet forming

  1. Automobile sheet metal part production with incremental sheet forming

    İsmail DURGUN

    2016-02-01

    Full Text Available Nowadays, effect of global warming is increasing drastically so it leads to increased interest on energy efficiency and sustainable production methods. As a result of adverse conditions, national and international project platforms, OEMs (Original Equipment Manufacturers, SMEs (Small and Mid-size Manufacturers perform many studies or improve existing methodologies in scope of advanced manufacturing techniques. In this study, advanced manufacturing and sustainable production method "Incremental Sheet Metal Forming (ISF" was used for sheet metal forming process. A vehicle fender was manufactured with or without die by using different toolpath strategies and die sets. At the end of the study, Results have been investigated under the influence of method and parameters used.Keywords: Template incremental sheet metal, Metal forming

  2. Single Point Incremental Forming using a Dummy Sheet

    Skjødt, Martin; Silva, Beatriz; Bay, Niels

    2007-01-01

    A new version of single point incremental forming (SPIF) is presented. This version includes a dummy sheet on top of the work piece, thus forming two sheets instead of one. The dummy sheet, which is in contact with the rotating tool pin, is discarded after forming. The new set-up influences....... The possible influence of friction between the two sheets is furthermore investigated. The results show that the use of a dummy sheet reduces wear of the work piece to almost zero, but also causes a decrease in formability. Bulging of the planar sides of the pyramid is reduced and surface roughness...

  3. Single point incremental forming: Formability of PC sheets

    Formisano, A.; Boccarusso, L.; Carrino, L.; Lambiase, F.; Minutolo, F. Memola Capece

    2018-05-01

    Recent research on Single Point Incremental Forming of polymers has slightly covered the possibility of expanding the materials capability window of this flexible forming process beyond metals, by demonstrating the workability of thermoplastic polymers at room temperature. Given the different behaviour of polymers compared to metals, different aspects need to be deepened to better understand the behaviour of these materials when incrementally formed. Thus, the aim of the work is to investigate the formability of incrementally formed polycarbonate thin sheets. To this end, an experimental investigation at room temperature was conducted involving formability tests; varying wall angle cone and pyramid frusta were manufactured by processing polycarbonate sheets with different thicknesses and using tools with different diameters, in order to draw conclusions on the formability of polymer sheets through the evaluation of the forming angles and the observation of the failure mechanisms.

  4. Rapid Prototyping by Single Point Incremental Forming of Sheet Metal

    Skjødt, Martin

    2008-01-01

    . The process is incremental forming since plastic deformation takes place in a small local zone underneath the forming tool, i.e. the sheet is formed as a summation of the movement of the local plastic zone. The process is slow and therefore only suited for prototypes or small batch production. On the other...... in the plastic zone. Using these it is demonstrated that the growth rate of accumulated damage in SPIF is small compared to conventional sheet forming processes. This combined with an explanation why necking is suppressed is a new theory stating that SPIF is limited by fracture and not necking. The theory...... SPIF. A multi stage strategy is presented which allows forming of a cup with vertical sides in about half of the depth. It is demonstrated that this results in strain paths which are far from straight, but strains are still limited by a straight fracture line in the principal strain space. The multi...

  5. Improving process performance in Incremental Sheet Forming (ISF)

    Ambrogio, G.; Filice, L.; Manco, G. L.

    2011-01-01

    Incremental Sheet Forming (ISF) is a relatively new process in which a sheet clamped along the borders is progressively deformed through a hemispherical tool. The tool motion is CNC controlled and the path is designed using a CAD-CAM approach, with the aim to reproduce the final shape contour such as in the surface milling. The absence of a dedicated setup and the related high flexibility is the main point of strength and the reason why several researchers focused their attentions on the ISF process.On the other hand the process slowness is the most relevant drawback which reduces a wider industrial application. In the paper, a first attempt to overcome this process limitation is presented taking into account a relevant speed increasing respect to the values currently used.

  6. Numerical Simulation of Incremental Sheet Forming by Simplified Approach

    Delamézière, A.; Yu, Y.; Robert, C.; Ayed, L. Ben; Nouari, M.; Batoz, J. L.

    2011-01-01

    The Incremental Sheet Forming (ISF) is a process, which can transform a flat metal sheet in a 3D complex part using a hemispherical tool. The final geometry of the product is obtained by the relative movement between this tool and the blank. The main advantage of that process is that the cost of the tool is very low compared to deep drawing with rigid tools. The main disadvantage is the very low velocity of the tool and thus the large amount of time to form the part. Classical contact algorithms give good agreement with experimental results, but are time consuming. A Simplified Approach for the contact management between the tool and the blank in ISF is presented here. The general principle of this approach is to imposed displacement of the nodes in contact with the tool at a given position. On a benchmark part, the CPU time of the present Simplified Approach is significantly reduced compared with a classical simulation performed with Abaqus implicit.

  7. Effect of multiple forming tools on geometrical and mechanical properties in incremental sheet forming

    Wernicke, S.; Dang, T.; Gies, S.; Tekkaya, A. E.

    2018-05-01

    The tendency to a higher variety of products requires economical manufacturing processes suitable for the production of prototypes and small batches. In the case of complex hollow-shaped parts, single point incremental forming (SPIF) represents a highly flexible process. The flexibility of this process comes along with a very long process time. To decrease the process time, a new incremental forming approach with multiple forming tools is investigated. The influence of two incremental forming tools on the resulting mechanical and geometrical component properties compared to SPIF is presented. Sheets made of EN AW-1050A were formed to frustums of a pyramid using different tool-path strategies. Furthermore, several variations of the tool-path strategy are analyzed. A time saving between 40% and 60% was observed depending on the tool-path and the radii of the forming tools while the mechanical properties remained unchanged. This knowledge can increase the cost efficiency of incremental forming processes.

  8. Decoupled Simulation Method For Incremental Sheet Metal Forming

    Sebastiani, G.; Brosius, A.; Tekkaya, A. E.; Homberg, W.; Kleiner, M.

    2007-01-01

    Within the scope of this article a decoupling algorithm to reduce computing time in Finite Element Analyses of incremental forming processes will be investigated. Based on the given position of the small forming zone, the presented algorithm aims at separating a Finite Element Model in an elastic and an elasto-plastic deformation zone. Including the elastic response of the structure by means of model simplifications, the costly iteration in the elasto-plastic zone can be restricted to the small forming zone and to few supporting elements in order to reduce computation time. Since the forming zone moves along the specimen, an update of both, forming zone with elastic boundary and supporting structure, is needed after several increments.The presented paper discusses the algorithmic implementation of the approach and introduces several strategies to implement the denoted elastic boundary condition at the boundary of the plastic forming zone

  9. Radial-rotation profile forming: A new processing technology of incremental sheet metal forming

    Laue, Robert; Härtel, Sebastian; Awiszus, Birgit

    2018-05-01

    Incremental forming processes (i.e., spinning) of sheet metal blanks into cylindrical cups are suitable for lower lot sizes. The produced cups were frequently used as preforms to produce workpieces in further forming steps with additional functions like profiled hollow parts [1]. The incremental forming process radial-rotation profile forming has been developed to enable the production of profiled hollow parts with low sheet thinning and good geometrical accuracy. The two principal forming steps are the production of the preform by rotational swing-folding [2] and the subsequent radial profiling of the hollow part in one clamping position. The rotational swing-folding process is based on a combination of conventional spinning and swing-folding. Therefore, a round blank rotates on a profiled mandrel and due to the swinging of a cylindrical forming tool, the blank is formed to a cup with low sheet thinning. In addition, thickening results at the edge of the blank and wrinkling occurs. However, the wrinkles are formed into the indentation of the profiled mandrel and can be reshaped as an advantage in the second process step, the radial profiling. Due to the rotation and continuous radial feed of a profiled forming tool to the profiled mandrel, the axial profile is formed in the second process step. Because of the minor relative movement in axial direction between tool and blank, low sheet thinning occurs. This is an advantage of the principle of the process.

  10. Optimization of Surface Roughness and Wall Thickness in Dieless Incremental Forming Of Aluminum Sheet Using Taguchi

    Hamedon, Zamzuri; Kuang, Shea Cheng; Jaafar, Hasnulhadi; Azhari, Azmir

    2018-03-01

    Incremental sheet forming is a versatile sheet metal forming process where a sheet metal is formed into its final shape by a series of localized deformation without a specialised die. However, it still has many shortcomings that need to be overcome such as geometric accuracy, surface roughness, formability, forming speed, and so on. This project focus on minimising the surface roughness of aluminium sheet and improving its thickness uniformity in incremental sheet forming via optimisation of wall angle, feed rate, and step size. Besides, the effect of wall angle, feed rate, and step size to the surface roughness and thickness uniformity of aluminium sheet was investigated in this project. From the results, it was observed that surface roughness and thickness uniformity were inversely varied due to the formation of surface waviness. Increase in feed rate and decrease in step size will produce a lower surface roughness, while uniform thickness reduction was obtained by reducing the wall angle and step size. By using Taguchi analysis, the optimum parameters for minimum surface roughness and uniform thickness reduction of aluminium sheet were determined. The finding of this project helps to reduce the time in optimising the surface roughness and thickness uniformity in incremental sheet forming.

  11. An approach to eliminate stepped features in multistage incremental sheet forming process: Experimental and FEA analysis

    Nirala, Harish Kumar; Jain, Prashant K.; Tandon, Puneet [PDPM Indian Institute of Information Technology, Design and Manufacturing Jabalpur Jabalpur-482005, Madhya Pradesh (India); Roy, J. J.; Samal, M. K. [Bhabha Atomic Research Centre, Mumbai (India)

    2017-02-15

    Incremental sheet forming (ISF) is a recently developed manufacturing technique. In ISF, forming is done by applying deformation force through the motion of Numerically controlled (NC) single point forming tool on the clamped sheet metal blank. Single Point Incremental sheet forming (SPISF) is also known as a die-less forming process because no die is required to fabricate any component by using this process. Now a day it is widely accepted for rapid manufacturing of sheet metal components. The formability of SPISF process improves by adding some intermediate stages into it, which is known as Multi-stage SPISF (MSPISF) process. However during forming in MSPISF process because of intermediate stages stepped features are generated. This paper investigates the generation of stepped features with simulation and experimental results. An effective MSPISF strategy is proposed to remove or eliminate this generated undesirable stepped features.

  12. Influence of part orientation on the geometric accuracy in robot-based incremental sheet metal forming

    Störkle, Denis Daniel; Seim, Patrick; Thyssen, Lars; Kuhlenkötter, Bernd

    2016-10-01

    This article describes new developments in an incremental, robot-based sheet metal forming process (`Roboforming') for the production of sheet metal components for small lot sizes and prototypes. The dieless kinematic-based generation of the shape is implemented by means of two industrial robots, which are interconnected to a cooperating robot system. Compared to other incremental sheet metal forming (ISF) machines, this system offers high geometrical form flexibility without the need of any part-dependent tools. The industrial application of ISF is still limited by certain constraints, e.g. the low geometrical accuracy. Responding to these constraints, the authors present the influence of the part orientation and the forming sequence on the geometric accuracy. Their influence is illustrated with the help of various experimental results shown and interpreted within this article.

  13. Incremental electrohydraulic forming - A new approach for the manufacture of structured multifunctional sheet metal blanks

    Djakow, Eugen; Springer, Robert; Homberg, Werner; Piper, Mark; Tran, Julian; Zibart, Alexander; Kenig, Eugeny

    2017-10-01

    Electrohydraulic Forming (EHF) processes permit the production of complex, sharp-edged geometries even when high-strength materials are used. Unfortunately, the forming zone is often limited as compared to other sheet metal forming processes. The use of a special industrial-robot-based tool setup and an incremental process strategy could provide a promising solution for this problem. This paper describes such an innovative approach using an electrohydraulic incremental forming machine, which can be employed to manufacture the large multifunctional and complex part geometries in steel, aluminium, magnesium and reinforced plastic that are employed in lightweight constructions or heating elements.

  14. Robot-based additive manufacturing for flexible die-modelling in incremental sheet forming

    Rieger, Michael; Störkle, Denis Daniel; Thyssen, Lars; Kuhlenkötter, Bernd

    2017-10-01

    The paper describes the application concept of additive manufactured dies to support the robot-based incremental sheet metal forming process (`Roboforming') for the production of sheet metal components in small batch sizes. Compared to the dieless kinematic-based generation of a shape by means of two cooperating industrial robots, the supporting robot models a die on the back of the metal sheet by using the robot-based fused layer manufacturing process (FLM). This tool chain is software-defined and preserves the high geometrical form flexibility of Roboforming while flexibly generating support structures adapted to the final part's geometry. Test series serve to confirm the feasibility of the concept by investigating the process challenges of the adhesion to the sheet surface and the general stability as well as the influence on the geometric accuracy compared to the well-known forming strategies.

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

    Meier, Horst; Laurischkat, Roman; Zhu Junhong

    2011-01-01

    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.

  16. Optimization of Single Point Incremental Forming of Al5052-O Sheet

    Kim, Chan Il; Xiao, Xiao; Do, Van Cuong; Kim, Young Suk [Kyungpook Nat’l Univ., Daegu (Korea, Republic of)

    2017-03-15

    Single point incremental forming (SPIF) is a sheet-forming technique. It is a die-less sheet metal manufacturing process for rapid prototyping and small batch production. The Critical parameters in the forming process include tool diameter, step depth, feed rate, spindle speed, etc. In this study, these parameters and the die shape corresponding to the Varying Wall Angle Conical Frustum(VWACF) model were used for forming 0.8mm in thick Al5052-O sheets. The Taguchi method of Experiments of Design (DOE) and Grey relational optimization were used to determine the optimum parameters in SPIF. A response study was performed on formability, spring back, and thickness reduction. The research shows that the optimum combination of these parameters that yield best performance of SPIF is as follows: tool diameter, 6mm; spin speed, 60rpm; step depth, 0.3mm; and feed rate, 500mm/min.

  17. Modeling of optimization strategies in the incremental CNC sheet metal forming process

    Bambach, M.; Hirt, G.; Ames, J.

    2004-01-01

    Incremental CNC sheet forming (ISF) is a relatively new sheet metal forming process for small batch production and prototyping. In ISF, a blank is shaped by the CNC movements of a simple tool in combination with a simplified die. The standard forming strategies in ISF entail two major drawbacks: (i) the inherent forming kinematics set limits on the maximum wall angle that can be formed with ISF. (ii) since elastic parts of the imposed deformation can currently not be accounted for in CNC code generation, the standard strategies can lead to undesired deviations between the target and the sample geometry.Several enhancements have recently been put forward to overcome the above limitations, among them a multistage forming strategy to manufacture steep flanges, and a correction algorithm to improve the geometric accuracy. Both strategies have been successful in improving the forming of simple parts. However, the high experimental effort to empirically optimize the tool paths motivates the use of process modeling techniques.This paper deals with finite element modeling of the ISF process. In particular, the outcome of different multistage strategies is modeled and compared to collated experimental results regarding aspects such as sheet thickness and the onset of wrinkling. Moreover, the feasibility of modeling the geometry of a part is investigated as this is of major importance with respect to optimizing the geometric accuracy. Experimental validation is achieved by optical deformation measurement that gives the local displacements and strains of the sheet during forming as benchmark quantities for the simulation

  18. Adaptive scallop height tool path generation for robot-based incremental sheet metal forming

    Seim, Patrick; Möllensiep, Dennis; Störkle, Denis Daniel; Thyssen, Lars; Kuhlenkötter, Bernd

    2016-10-01

    Incremental sheet metal forming is an emerging process for the production of individualized products or prototypes in low batch sizes and with short times to market. In these processes, the desired shape is produced by the incremental inward motion of the workpiece-independent forming tool in depth direction and its movement along the contour in lateral direction. Based on this shape production, the tool path generation is a key factor on e.g. the resulting geometric accuracy, the resulting surface quality, and the working time. This paper presents an innovative tool path generation based on a commercial milling CAM package considering the surface quality and working time. This approach offers the ability to define a specific scallop height as an indicator of the surface quality for specific faces of a component. Moreover, it decreases the required working time for the production of the entire component compared to the use of a commercial software package without this adaptive approach. Different forming experiments have been performed to verify the newly developed tool path generation. Mainly, this approach serves to solve the existing conflict of combining the working time and the surface quality within the process of incremental sheet metal forming.

  19. Optimization of the single point incremental forming process for titanium sheets by using response surface

    Saidi Badreddine

    2016-01-01

    Full Text Available The single point incremental forming process is well-known to be perfectly suited for prototyping and small series. One of its fields of applicability is the medicine area for the forming of titanium prostheses or titanium medical implants. However this process is not yet very industrialized, mainly due its geometrical inaccuracy, its not homogeneous thickness distribution& Moreover considerable forces can occur. They must be controlled in order to preserve the tooling. In this paper, a numerical approach is proposed in order to minimize the maximum force achieved during the incremental forming of titanium sheets and to maximize the minimal thickness. A surface response methodology is used to find the optimal values of two input parameters of the process, the punch diameter and the vertical step size of the tool path.

  20. Early Shear Failure Prediction in Incremental Sheet Forming Process Using FEM and ANN

    Moayedfar, Majid; Hanaei, Hengameh; Majdi Rani, Ahmad; Musa, Mohd Azam Bin; Sadegh Momeni, Mohammad

    2018-03-01

    The application of incremental sheet forming process as a rapid forming technique is rising in variety of industries such as aerospace, automotive and biomechanical purposes. However, the sheet failure is a big challenge in this process which leads wasting lots of materials. Hence, this study tried to propose a method to predict the early sheet failure in this process using mathematical solution. For the feasibility of the study, design of experiment with the respond surface method is employed to extract a set of experiments data for the simulation. The significant forming parameters were recognized and their integration was used for prediction system. Then, the results were inserted to the artificial neural network as input parameters to predict a vast range of applicable parameters avoiding sheet failure in ISF. The value of accuracy R2 ∼0.93 was obtained and the maximum sheet stretch in the depth of 25mm were recorded. The figures generate from the trend of interaction between effective parameters were provided for future studies.

  1. Finite element simulation and Experimental verification of Incremental Sheet metal Forming

    Kaushik Yanamundra, Krishna; Karthikeyan, R., Dr.; Naranje, Vishal, Dr

    2018-04-01

    Incremental sheet metal forming is now a proven manufacturing technique that can be employed to obtain application specific, customized, symmetric or asymmetric shapes that are required by automobile or biomedical industries for specific purposes like car body parts, dental implants or knee implants. Finite element simulation of metal forming process is being performed successfully using explicit dynamics analysis of commercial FE software. The simulation is mainly useful in optimization of the process as well design of the final product. This paper focuses on simulating the incremental sheet metal forming process in ABAQUS, and validating the results using experimental methods. The shapes generated for testing are of trapezoid, dome and elliptical shapes whose G codes are written and fed into the CNC milling machine with an attached forming tool with a hemispherical bottom. The same pre-generated coordinates are used to simulate a similar machining conditions in ABAQUS and the tool forces, stresses and strains in the workpiece while machining are obtained as the output data. The forces experimentally were recorded using a dynamometer. The experimental and simulated results were then compared and thus conclusions were drawn.

  2. Investigation of the deformation stability in the incremental sheet forming process

    Ai S.

    2015-01-01

    Full Text Available Incremental sheet forming (ISF is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. One of the unique characters of the ISF process is the improved formability comparing to conventional sheet forming process. This may be due to the localized deformation nature, which increases the deformation stability in the ISF process. Although many hypotheses have been proposed, there is no direct modelling and calculation of the ISF deformation stability. Aiming to obtain a better understanding of the ISF process, an analytical model was developed to investigate and analyse the material deformation stability in this work. Based on the analytical evaluation of stress variations and force equilibrium, a mathematical relationship between the maximum forming angle and the process stability condition was established. To validate the developed model, experiments were carried out by forming a hyperbolic part made of AA1100 material. The maximum forming angle, as an indicator to the ISF formability, was employed compare the analytical evaluation and experimental result. It was found that the ISF deformation stability is one of the key factors that affect the ISF formability.

  3. Performance analysis of the incremental sheet forming on PMMA using a combined chemical and mechanical approach

    Conte, R.; Gagliardi, F.; Ambrogio, G.; Filice, F.; Russo, P.

    2017-10-01

    Single Point Incremental Forming (SPIF) has been widely investigated highlighting advantages as low-cost, higher formability and greater process flexibility if compared to traditional processes [1]. Recent works have proven the SPIF feasibility for polymers processing. Experimental researches have been carried out with the aim to investigate the influence of several working variables, i.e. spindle speed, tool diameter, step depth, etc., on the final quality of the formed parts [2, 3]. The processed thermoplastic materials are characterized by glass temperatures close to the room temperature and, therefore, SPIF has been performed without external thermal source, exploiting mostly the friction heat generated during the forming phases. In the proposed work, the attention has been focused on extruded poly(methyl methacrylate) (PMMA) sheets, which are characterized by a glass temperature of more than 100 °C. Because of that, an experimental equipment has been designed and the PMMA sheets have been placed on the top of chamber with controlled temperature before SPIF beginning. The temperature on the upper face of the sheets has been monitored by thermocamera, which has been properly set by matching its readings with the ones extracted by a thermocouple in contact with the sheets. SPIF at different temperatures has been carried out by changing both the heater temperature and the process parameters which have an influence on the workpiece heating. The influence of the highlighted process conditions on the worked parts and on the process feasibility has been investigated. Furthermore, examinations on the quality of the formed parts have been performed pointing out the effects that different process conditions have on surface integrity.

  4. Localised and Learnt Applications of Machine Learning for Robotic Incremental Sheet Forming

    Nicholas, Paul; Zwierzycki, Mateusz; Ramsgaard Thomsen, Mette

    2017-01-01

    Sheet Forming (ISF) and exemplified in the fabrication of a bridge structure. The methods we describe compensate for springback and improve forming tolerance by using localised in-process distance sensing to adapt tool-paths, and by using pre-process supervised machine learning to predict stringback...

  5. Substructuring in the implicit simulation of single point incremental sheet forming

    Hadoush, A.; van den Boogaard, Antonius H.

    2009-01-01

    This paper presents a direct substructuring method to reduce the computing time of implicit simulations of single point incremental forming (SPIF). Substructuring is used to divide the finite element (FE) mesh into several non-overlapping parts. Based on the hypothesis that plastic deformation is

  6. Formability behavior studies on CP-Al sheets processed through the helical tool path of incremental forming process

    Markanday, H.; Nagarajan, D.

    2018-02-01

    Incremental sheet forming (ISF) is a novel die-less sheet metal forming process, which can produce components directly from the CAD geometry using a CNC milling machine at less production time and cost. The formability of the sheet material used is greatly affected by the process parameters involved and tool path adopted, and the present study is aimed to investigate the influence of different process parameter values using the helical tool path strategy on the formability of a commercial pure Al and to achieve maximum formability in the material. ISF experiments for producing an 80 mm diameter axisymmetric dome were carried out on 2 mm thickness commercially pure Al sheets for different tool speeds and feed rates in a CNC milling machine with a 10 mm hemispherical forming tool. The obtained parts were analyzed for springback, amount of thinning and maximum forming depth. The results showed that when the tool speed was increased by keeping the feed rate constant, the forming depth and thinning were also increased. On contrary, when the feed rate was increased by keeping the tool speed constant, the forming depth and thinning were decreased. Springback was found to be higher when the feed rate was increased rather than the tool speed was increased.

  7. An Integrated Modelling and Toolpathing Approach for a Frameless Stressed Skin Structure, Fabricated Using Robotic Incremental Sheet Forming

    Nicholas, Paul; Stasiuk, David; Nørgaard, Esben Clausen

    2016-01-01

    with performance implications at material, element and structural scales. This paper briefly presents ISF as a method of fabrication, and introduces the context of structures where the skin plays an integral role. It describes the development of an integrated approach for the modelling and fabrication of Stressed...... Skins, an incrementally formed sheet metal structure. The paper then focus upon the use of prototypes and empirical testing as means to inform digital models about fabrication and material parameters including: material forming limits and thinning; the parameterisation of macro and meso simulations...

  8. Analysis of residual stress state in sheet metal parts processed by single point incremental forming

    Maaß, F.; Gies, S.; Dobecki, M.; Brömmelhoff, K.; Tekkaya, A. E.; Reimers, W.

    2018-05-01

    The mechanical properties of formed metal components are highly affected by the prevailing residual stress state. A selective induction of residual compressive stresses in the component, can improve the product properties such as the fatigue strength. By means of single point incremental forming (SPIF), the residual stress state can be influenced by adjusting the process parameters during the manufacturing process. To achieve a fundamental understanding of the residual stress formation caused by the SPIF process, a valid numerical process model is essential. Within the scope of this paper the significance of kinematic hardening effects on the determined residual stress state is presented based on numerical simulations. The effect of the unclamping step after the manufacturing process is also analyzed. An average deviation of the residual stress amplitudes in the clamped and unclamped condition of 18 % reveals, that the unclamping step needs to be considered to reach a high numerical prediction quality.

  9. Creating Helical Tool Paths for Single Point Incremental Forming

    Skjødt, Martin; Hancock, Michael H.; Bay, Niels

    2007-01-01

    Single point incremental forming (SPIF) is a relatively new sheet forming process. A sheet is clamped in a rig and formed incrementally using a rotating single point tool in the form of a rod with a spherical end. The process is often performed on a CNC milling machine and the tool movement...

  10. Apparatus for electrical-assisted incremental forming and process thereof

    Roth, John; Cao, Jian

    2018-04-24

    A process and apparatus for forming a sheet metal component using an electric current passing through the component. The process can include providing an incremental forming machine, the machine having at least one arcuate tipped tool and at least electrode spaced a predetermined distance from the arcuate tipped tool. The machine is operable to perform a plurality of incremental deformations on the sheet metal component using the arcuate tipped tool. The machine is also operable to apply an electric direct current through the electrode into the sheet metal component at the predetermined distance from the arcuate tipped tool while the machine is forming the sheet metal component.

  11. The effect of the model posture on the forming quality in the CNC incremental forming

    Zhu, H; Zhang, W; Bai, J L; Yu, C; Xing, Y F

    2015-01-01

    Sheet rupture caused by a sheet metal thickness non-uniformity persists in CNC (Computer Numerical Control) incremental forming. Because the forming half cone angle is determined by the orientation of the model to be formed, so is the sheet metal's uniformity. The finite element analysis models for the two kinds of the postures of the model were established, and the digital simulation was conducted by using the ANSYS/LA-DYNA software. The effect of the model's posture on the sheet thickness distribution and the sheet thickness thinning rate were studied by comparing the simulation results of two kinds of the finite elements analyzes. (paper)

  12. Revisiting the fundamentals of single point incremental forming by

    Silva, Beatriz; Skjødt, Martin; Martins, Paulo A.F.

    2008-01-01

    Knowledge of the physics behind the fracture of material at the transition between the inclined wall and the corner radius of the sheet is of great importance for understanding the fundamentals of single point incremental forming (SPIF). How the material fractures, what is the state of strain...

  13. Prediction of Path Deviation in Robot Based Incremental Sheet Metal Forming by Means of a New Solid-Shell Finite Element Technology and a Finite Elastoplastic Model with Combined Hardening

    Kiliclar, Yalin; Laurischkat, Roman; Vladimirov, Ivaylo N.; Reese, Stefanie

    2011-08-01

    The presented project deals with a robot based incremental sheet metal forming process, which is called roboforming and has been developed at the Chair of Production Systems. It is characterized by flexible shaping using a freely programmable path-synchronous movement of two industrial robots. The final shape is produced by the incremental infeed of the forming tool in depth direction and its movement along the part contour in lateral direction. However, the resulting geometries formed in roboforming deviate several millimeters from the reference geometry. This results from the compliance of the involved machine structures and the springback effects of the workpiece. The project aims to predict these deviations caused by resiliences and to carry out a compensative path planning based on this prediction. Therefore a planning tool is implemented which compensates the robots's compliance and the springback effects of the sheet metal. The forming process is simulated by means of a finite element analysis using a material model developed at the Institute of Applied Mechanics (IFAM). It is based on the multiplicative split of the deformation gradient in the context of hyperelasticity and combines nonlinear kinematic and isotropic hardening. Low-order finite elements used to simulate thin sheet structures, such as used for the experiments, have the major problem of locking, a nonphysical stiffening effect. For an efficient finite element analysis a special solid-shell finite element formulation based on reduced integration with hourglass stabilization has been developed. To circumvent different locking effects, the enhanced assumed strain (EAS) and the assumed natural strain (ANS) concepts are included in this formulation. Having such powerful tools available we obtain more accurate geometries.

  14. Theory of Single Point Incremental Forming

    Martins, P.A.F.; Bay, Niels; Skjødt, Martin

    2008-01-01

    This paper presents a closed-form theoretical analysis modelling the fundamentals of single point incremental forming and explaining the experimental and numerical results available in the literature for the past couple of years. The model is based on membrane analysis with bi-directional in-plan......-plane contact friction and is focused on the extreme modes of deformation that are likely to be found in single point incremental forming processes. The overall investigation is supported by experimental work performed by the authors and data retrieved from the literature.......This paper presents a closed-form theoretical analysis modelling the fundamentals of single point incremental forming and explaining the experimental and numerical results available in the literature for the past couple of years. The model is based on membrane analysis with bi-directional in...

  15. A numerical analysis on forming limits during spiral and concentric single point incremental forming

    Gipiela, M. L.; Amauri, V.; Nikhare, C.; Marcondes, P. V. P.

    2017-01-01

    Sheet metal forming is one of the major manufacturing industries, which are building numerous parts for aerospace, automotive and medical industry. Due to the high demand in vehicle industry and environmental regulations on less fuel consumption on other hand, researchers are innovating new methods to build these parts with energy efficient sheet metal forming process instead of conventionally used punch and die to form the parts to achieve the lightweight parts. One of the most recognized manufacturing process in this category is Single Point Incremental Forming (SPIF). SPIF is the die-less sheet metal forming process in which the single point tool incrementally forces any single point of sheet metal at any process time to plastic deformation zone. In the present work, finite element method (FEM) is applied to analyze the forming limits of high strength low alloy steel formed by single point incremental forming (SPIF) by spiral and concentric tool path. SPIF numerical simulations were model with 24 and 29 mm cup depth, and the results were compare with Nakajima results obtained by experiments and FEM. It was found that the cup formed with Nakajima tool failed at 24 mm while cups formed by SPIF surpassed the limit for both depths with both profiles. It was also notice that the strain achieved in concentric profile are lower than that in spiral profile.

  16. Failure mechanisms in single-point incremental forming of metals

    Silva, Maria B.; Nielsen, Peter Søe; Bay, Niels

    2011-01-01

    The last years saw the development of two different views on how failure develops in single-point incremental forming (SPIF). Today, researchers are split between those claiming that fracture is always preceded by necking and those considering that fracture occurs with suppression of necking. Each...... on formability limits and development of fracture. The unified view conciliates the aforementioned different explanations on the role of necking in fracture and is consistent with the experimental observations that have been reported in the past years. The work is performed on aluminium AA1050-H111 sheets...

  17. Thermomechanical simulations and experimental validation for high speed incremental forming

    Ambrogio, Giuseppina; Gagliardi, Francesco; Filice, Luigino; Romero, Natalia

    2016-10-01

    Incremental sheet forming (ISF) consists in deforming only a small region of the workspace through a punch driven by a NC machine. The drawback of this process is its slowness. In this study, a high speed variant has been investigated from both numerical and experimental points of view. The aim has been the design of a FEM model able to perform the material behavior during the high speed process by defining a thermomechanical model. An experimental campaign has been performed by a CNC lathe with high speed to test process feasibility. The first results have shown how the material presents the same performance than in conventional speed ISF and, in some cases, better material behavior due to the temperature increment. An accurate numerical simulation has been performed to investigate the material behavior during the high speed process confirming substantially experimental evidence.

  18. Manifold free multiple sheet superplastic forming

    Elmer, John W.; Bridges, Robert L.

    2004-01-13

    Fluid-forming compositions in a container attached to enclosed adjacent sheets are heated to relatively high temperatures to generate fluids (gases) that effect inflation of the sheets. Fluid rates to the enclosed space between the sheets can be regulated by the canal from the container. Inflated articles can be produced by a continuous, rather than batch-type, process.

  19. AI applications in sheet metal forming

    Hussein, Hussein

    2017-01-01

    This book comprises chapters on research work done around the globe in the area of artificial intelligence (AI) applications in sheet metal forming. The first chapter offers an introduction to various AI techniques and sheet metal forming, while subsequent chapters describe traditional procedures/methods used in various sheet metal forming processes, and focus on the automation of those processes by means of AI techniques, such as KBS, ANN, GA, CBR, etc. Feature recognition and the manufacturability assessment of sheet metal parts, process planning, strip-layout design, selecting the type and size of die components, die modeling, and predicting die life are some of the most important aspects of sheet metal work. Traditionally, these activities are highly experience-based, tedious and time consuming. In response, researchers in several countries have applied various AI techniques to automate these activities, which are covered in this book. This book will be useful for engineers working in sheet metal industri...

  20. Determining frustum depth of 304 stainless steel plates with various diameters and thicknesses by incremental forming

    Golabi, Sa' id [University of Kashan, Kashan (Iran, Islamic Republic of); Khazaali, Hossain [Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of)

    2014-08-15

    Nowadays incremental forming is more popular because of its flexibility and cost saving. However, no engineering data is available for manufacturers for forming simple shapes like a frustum by incremental forming, and either expensive experimental tests or finite element analysis (FEA) should be employed to determine the depth of a frustum considering: thickness, material, cone diameter, wall angle, feed rate, tool diameter, etc. In this study, finite element technique, confirmed by experimental study, was employed for developing applicable curves for determining the depth of frustums made from 304 stainless steel (SS304) sheet with various cone angles, thicknesses from 0.3 to 1 mm and major diameters from 50 to 200 mm using incremental forming. Using these curves, the frustum angle and its depth knowing its thickness and major diameter can be predicted. The effects of feed rate, vertical pitch and tool diameter on frustum depth and surface quality were also addressed in this study.

  1. Advanced friction modeling for sheet metal forming

    Hol, J.; Cid Alfaro, M.V.; de Rooij, Matthias B.; Meinders, Vincent T.

    2012-01-01

    The Coulomb friction model is frequently used for sheet metal forming simulations. This model incorporates a constant coefficient of friction and does not take the influence of important parameters such as contact pressure or deformation of the sheet material into account. This article presents a

  2. Advanced friction modeling in sheet metal forming

    Hol, J.; Cid Alfaro, M.V.; Meinders, Vincent T.; Huetink, Han

    2011-01-01

    The Coulomb friction model is frequently used for sheet metal forming simulations. This model incorporates a constant coefficient of friction and does not take the influence of important parameters such as contact pressure or deformation of the sheet material into account. This article presents a

  3. Single-point incremental forming and formability-failure diagrams

    Silva, M.B.; Skjødt, Martin; Atkins, A.G.

    2008-01-01

    In a recent work [1], the authors constructed a closed-form analytical model that is capable of dealing with the fundamentals of single point incremental forming and explaining the experimental and numerical results published in the literature over the past couple of years. The model is based...... of deformation that are commonly found in general single point incremental forming processes; and (ii) to investigate the formability limits of SPIF in terms of ductile damage mechanics and the question of whether necking does, or does not, precede fracture. Experimentation by the authors together with data...

  4. Springback effects during single point incremental forming: Optimization of the tool path

    Giraud-Moreau, Laurence; Belchior, Jérémy; Lafon, Pascal; Lotoing, Lionel; Cherouat, Abel; Courtielle, Eric; Guines, Dominique; Maurine, Patrick

    2018-05-01

    Incremental sheet forming is an emerging process to manufacture sheet metal parts. This process is more flexible than conventional one and well suited for small batch production or prototyping. During the process, the sheet metal blank is clamped by a blank-holder and a small-size smooth-end hemispherical tool moves along a user-specified path to deform the sheet incrementally. Classical three-axis CNC milling machines, dedicated structure or serial robots can be used to perform the forming operation. Whatever the considered machine, large deviations between the theoretical shape and the real shape can be observed after the part unclamping. These deviations are due to both the lack of stiffness of the machine and residual stresses in the part at the end of the forming stage. In this paper, an optimization strategy of the tool path is proposed in order to minimize the elastic springback induced by residual stresses after unclamping. A finite element model of the SPIF process allowing the shape prediction of the formed part with a good accuracy is defined. This model, based on appropriated assumptions, leads to calculation times which remain compatible with an optimization procedure. The proposed optimization method is based on an iterative correction of the tool path. The efficiency of the method is shown by an improvement of the final shape.

  5. Two-Point Incremental Forming with Partial Die: Theory and Experimentation

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

    2013-04-01

    This paper proposes a new level of understanding of two-point incremental forming (TPIF) with partial die by means of a combined theoretical and experimental investigation. The theoretical developments include an innovative extension of the analytical model for rotational symmetric single point incremental forming (SPIF), originally developed by the authors, to address the influence of the major operating parameters of TPIF and to successfully explain the differences in formability between SPIF and TPIF. The experimental work comprised the mechanical characterization of the material and the determination of its formability limits at necking and fracture by means of circle grid analysis and benchmark incremental sheet forming tests. Results show the adequacy of the proposed analytical model to handle the deformation mechanics of SPIF and TPIF with partial die and demonstrate that neck formation is suppressed in TPIF, so that traditional forming limit curves are inapplicable to describe failure and must be replaced by fracture forming limits derived from ductile damage mechanics. The overall geometric accuracy of sheet metal parts produced by TPIF with partial die is found to be better than that of parts fabricated by SPIF due to smaller elastic recovery upon unloading.

  6. Multiscale friction modeling for sheet metal forming

    Hol, J.; Cid Alfaro, M.V.; de Rooij, Matthias B.; Meinders, Vincent T.; Felder, Eric; Montmitonnet, Pierre

    2010-01-01

    The most often used friction model for sheet metal forming simulations is the relative simple Coulomb friction model. This paper presents a more advanced friction model for large scale forming simulations based on the surface change on the micro-scale. The surface texture of a material changes when

  7. RAPID FREEFORM SHEET METAL FORMING: TECHNOLOGY DEVELOPMENT AND SYSTEM VERIFICATION

    Kiridena, Vijitha [Ford Scientific Research Lab., Dearborn, MI (United States); Verma, Ravi [Boeing Research and Technology (BR& T), Seattle, WA (United States); Gutowski, Timothy [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Roth, John [Pennsylvania State Univ., University Park, PA (United States)

    2018-03-31

    The objective of this project is to develop a transformational RApid Freeform sheet metal Forming Technology (RAFFT) in an industrial environment, which has the potential to increase manufacturing energy efficiency up to ten times, at a fraction of the cost of conventional technologies. The RAFFT technology is a flexible and energy-efficient process that eliminates the need for having geometry-specific forming dies. The innovation lies in the idea of using the energy resource at the local deformation area which provides greater formability, process control, and process flexibility relative to traditional methods. Double-Sided Incremental Forming (DSIF), the core technology in RAFFT, is a new concept for sheet metal forming. A blank sheet is clamped around its periphery and gradually deformed into a complex 3D freeform part by two strategically aligned stylus-type tools that follow a pre-described toolpath. The two tools, one on each side of the blank, can form a part with sharp features for both concave and convex shapes. Since deformation happens locally, the forming force at any instant is significantly decreased when compared to traditional methods. The key advantages of DSIF are its high process flexibility, high energy-efficiency, low capital investment, and the elimination of the need for massive amounts of die casting and machining. Additionally, the enhanced formability and process flexibility of DSIF can open up design spaces and result in greater weight savings.

  8. Constitutive Modeling for Sheet Metal Forming

    Barlat, Frederic

    2005-01-01

    This paper reviews aspects of the plastic behaviour common in sheet metals. Macroscopic and microscopic phenomena occurring during plastic deformation are described succinctly. Constitutive models of plasticity suitable for applications to forming, are discussed in a very broad manner. Approaches to plastic anisotropy are described in a somewhat more detailed manner

  9. Lubricant Test Methods for Sheet Metal Forming

    Bay, Niels; Olsson, David Dam; Andreasen, Jan Lasson

    2008-01-01

    appearing in different sheet forming operations such as stretch forming, deep drawing, ironing and punching. The laboratory tests have been especially designed to model the conditions in industrial production. Application of the tests for evaluating new lubricants before introducing them in production has......Sheet metal forming of tribologically difficult materials such as stainless steel, Al-alloys and Ti-alloys or forming in tribologically difficult operations like ironing, punching or deep drawing of thick plate requires often use of environmentally hazardous lubricants such as chlorinated paraffin...... oils in order to avoid galling. The present paper describes a systematic research in the development of new, environmentally harmless lubricants focusing on the lubricant testing aspects. A system of laboratory tests has been developed to study the lubricant performance under the very varied conditions...

  10. The use of single point incremental forming for customized implants of unicondylar knee arthroplasty: a review

    Pankaj Kailasrao Bhoyar

    Full Text Available Abstract Introduction The implantable devices are having enormous market. These products are basically made by traditional manufacturing process, but for the custom-made implants Incremental Sheet Forming is a paramount alternative. Single Point Incremental Forming (SPIF is a manufacturing process to form intricate, asymmetrical components. It forms the component using stretching and bending by maintaining materials crystal structure. SPIF process can be performed using conventional Computer Numerical Control (CNC milling machine. Review This review paper elaborates the various manufacturing processes carried on various biocompatible metallic and nonmetallic customised implantable devices. Conclusion Ti-6Al-4V alloy is broadly used for biomedical implants, but in this alloy, Vanadium is toxic so this alloy is not compatible for implants. The attention of researchers is towards the non toxic and suitable biocompatible materials. For this reason, a novel approach was developed in order to enhance the mechanical properties of this material. . The development of incremental forming technique can improve the formability of existing alloys and may meet the current strict requirements for performance of dies and punches.

  11. Prediction and control of pillow defect in single point incremental forming using numerical simulations

    Isidore, B. B. Lemopi; Hussain, G.; Khan, Wasim A.; Shamachi, S. Pourhassan

    2016-01-01

    Pillows formed at the center of sheets in Single point incremental forming (SPIF) are fabrication defects which adversely affect the geometrical accuracy and formability of manufactured parts. This study is focused on using FEA as a tool to predict and control pillowing in SPIF by varying tool size and shape. 3D Finite element analysis (FEA) and experiments are carried out using annealed Aluminum 1050. From FEA, it is found out that the stress/strain state in the immediate vicinity of the forming tool in the transverse direction plays a determinant role on sheet pillowing. Furthermore, pillow height increases as compression in the sheet-plane increases. The nature of in-plane stresses in the transverse direction varies from compressive to tensile as the tool-end geometry is changed from spherical to flat. Additionally, the magnitude of corresponding in-plane stresses decreases as the tool radius increases. According to measurements from the FEA model, flat end tools and large radii both retard pillow formation. However, the influence of changing tool end shape from hemispherical to flat is observed to be more important than the effect of varying tool radius, because the deformation zone remains in tension in the transverse direction while forming with flat end tools. These findings are verified by conducting a set of experiments. A fair agreement between the FEM and empirical results show that FEM can be employed as a tool to predict and control the pillow defect in SPIF.

  12. Prediction and control of pillow defect in single point incremental forming using numerical simulations

    Isidore, B. B. Lemopi [Eastern Mediterranean University, Gazimagusa (Turkmenistan); Hussain, G.; Khan, Wasim A. [GIK Institute of Engineering, Swabi (Pakistan); Shamachi, S. Pourhassan [University of Minho, Guimaraes (Portugal)

    2016-05-15

    Pillows formed at the center of sheets in Single point incremental forming (SPIF) are fabrication defects which adversely affect the geometrical accuracy and formability of manufactured parts. This study is focused on using FEA as a tool to predict and control pillowing in SPIF by varying tool size and shape. 3D Finite element analysis (FEA) and experiments are carried out using annealed Aluminum 1050. From FEA, it is found out that the stress/strain state in the immediate vicinity of the forming tool in the transverse direction plays a determinant role on sheet pillowing. Furthermore, pillow height increases as compression in the sheet-plane increases. The nature of in-plane stresses in the transverse direction varies from compressive to tensile as the tool-end geometry is changed from spherical to flat. Additionally, the magnitude of corresponding in-plane stresses decreases as the tool radius increases. According to measurements from the FEA model, flat end tools and large radii both retard pillow formation. However, the influence of changing tool end shape from hemispherical to flat is observed to be more important than the effect of varying tool radius, because the deformation zone remains in tension in the transverse direction while forming with flat end tools. These findings are verified by conducting a set of experiments. A fair agreement between the FEM and empirical results show that FEM can be employed as a tool to predict and control the pillow defect in SPIF.

  13. Single Point Incremental Forming to increase material knowledge and production flexibility

    Habraken, A.M.

    2016-01-01

    Nowadays, manufactured pieces can be divided into two groups: mass production and production of low volume number of parts. Within the second group (prototyping or small batch production), an emerging solution relies on Incremental Sheet Forming or ISF. ISF refers to processes where the plastic deformation occurs by repeated contact with a relatively small tool. More specifically, many publications over the past decade investigate Single Point Incremental Forming (SPIF) where the final shape is determined only by the tool movement. This manufacturing process is characterized by the forming of sheets by means of a CNC controlled generic tool stylus, with the sheets clamped by means of a non-workpiece-specific clamping system and in absence of a partial or a full die. The advantage is no tooling requirements and often enhanced formability, however it poses a challenge in term of process control and accuracy assurance. Note that the most commonly used materials in incremental forming are aluminum and steel alloys however other alloys are also used especially for medical industry applications, such as cobalt and chromium alloys, stainless steel and titanium alloys. Some scientists have applied incremental forming on PVC plates and other on sandwich panels composed of propylene with mild steel and aluminum metallic foams with aluminum sheet metal. Micro incremental forming of thin foils has also been developed. Starting from the scattering of the results of Finite Element (FE) simulations, when one tries to predict the tool force (see SPIF benchmark of 2014 Numisheet conference), we will see how SPIF and even micro SPIF (process applied on thin metallic sheet with a few grains within the thickness) allow investigating the material behavior. This lecture will focus on the identification of constitutive laws, on the SPIF forming mechanisms and formability as well as the failure mechanism. Different hypotheses have been proposed to explain SPIF formability, they will be

  14. Single Point Incremental Forming to increase material knowledge and production flexibility

    Habraken, A. M.

    2016-08-01

    Nowadays, manufactured pieces can be divided into two groups: mass production and production of low volume number of parts. Within the second group (prototyping or small batch production), an emerging solution relies on Incremental Sheet Forming or ISF. ISF refers to processes where the plastic deformation occurs by repeated contact with a relatively small tool. More specifically, many publications over the past decade investigate Single Point Incremental Forming (SPIF) where the final shape is determined only by the tool movement. This manufacturing process is characterized by the forming of sheets by means of a CNC controlled generic tool stylus, with the sheets clamped by means of a non-workpiece-specific clamping system and in absence of a partial or a full die. The advantage is no tooling requirements and often enhanced formability, however it poses a challenge in term of process control and accuracy assurance. Note that the most commonly used materials in incremental forming are aluminum and steel alloys however other alloys are also used especially for medical industry applications, such as cobalt and chromium alloys, stainless steel and titanium alloys. Some scientists have applied incremental forming on PVC plates and other on sandwich panels composed of propylene with mild steel and aluminum metallic foams with aluminum sheet metal. Micro incremental forming of thin foils has also been developed. Starting from the scattering of the results of Finite Element (FE) simulations, when one tries to predict the tool force (see SPIF benchmark of 2014 Numisheet conference), we will see how SPIF and even micro SPIF (process applied on thin metallic sheet with a few grains within the thickness) allow investigating the material behavior. This lecture will focus on the identification of constitutive laws, on the SPIF forming mechanisms and formability as well as the failure mechanism. Different hypotheses have been proposed to explain SPIF formability, they will be

  15. Strategies and limits in multi-stage single-point incremental forming

    Skjødt, Martin; Silva, M.B.; Martins, P. A. F.

    2010-01-01

    paths. The results also reveal that the sequence of multi-stage forming has a large effect on the location of strain points in the principal strain space. Strain paths are linear in the first stage and highly non-linear in the subsequent forming stages. The overall results show that the experimentally......Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups......-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain...

  16. Sheet-bulk metal formingforming of functional components from sheet metals

    Merklein Marion

    2015-01-01

    Full Text Available The paper gives an overview on the application of sheet-bulk metal forming operations in both scientific and industrial environment. Beginning with the need for an innovative forming technology, the definition of this new process class is introduced. The rising challenges of the application of bulk metal forming operations on sheet metals are presented and the demand on a holistic investigation of this topic is motivated. With the help of examples from established production processes, the latest state of technology and the lack on fundamental knowledge is shown. Furthermore, perspectives regarding new research topics within sheet-bulk metal forming are presented. These focus on processing strategies to improve the quality of functional components by the application of process-adapted semi-finished products as well as the local adaption of the tribological system.

  17. Damage Prediction in Sheet Metal Forming

    Saanouni, Khemais; Badreddine, Houssem

    2007-01-01

    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

  18. Tribo-systems for Sheet Metal Forming

    Bay, Niels

    2009-01-01

    The present paper gives an overview of more than 10 years work by the author’s research group through participation in national as well as international framework programmes on developing and testing environmentally friendly lubricants and tool materials and coatings inhibiting galling. Partners ......’s research group has especially been involved in the development of a system of tribo-tests for sheet metal forming and in testing and modelling of friction and limits of lubrication of new, environmentally friendly lubricants and tool materials....

  19. Laser-assisted micro sheet forming

    Holtkamp, Jens; Gillner, Arnold

    2008-01-01

    The fast growing market for micro technical products requires parts with increasing complexity. While sheet metal forming enables low cost mass production with short cycle times, it is limited by the maximum degree of deformation and the quality of the cut edge. The technology of warm forming partially eliminates these deficiencies. This operation takes place at elevated temperatures before structural transformation is initiated. It combines characteristic advantages of traditional cold and hot forming processes. Lasers as heat sources provide a high, selective and controllable energy input. The general difficulty of a uniform temperature distribution during the heating process can be reached by using an Axicon which generates an annulus on the sheet metal surface. The temperature of the workpiece, measured by a pyrometer, is tuned by a PI-Controller. A tool incorporating a multistage operation die is used for the manufacturing of up to three parts at the same time. The tool is integrated into a hydraulical press. A gearwheel made of the magnesium alloy AZ31 is chosen as metal demonstrator. The quality of these punched parts could be significantly improved at elevated temperatures

  20. Single point incremental forming of tailored blanks produced by friction stir welding

    Silva, M.B.; Skjødt, Martin; Vilaca, P.

    2009-01-01

    fromthe rotating single point-forming tool. Formability of the tailor welded blanks (TWB) is evaluated by means of benchmark tests carried out on truncated conical and pyramidal shapes and results are compared with similar tests performed on conventional reference blanks of the same material. Results show......This paper is focused on the single point incremental forming (SPIF) of tailored welded blanks produced by friction stirwelding (FSW). Special emphasis is placed on the know-how for producing the tailored blanks and on the utilization of innovative forming strategies to protect thewelding joint...... that the combination of SPIF with tailored welded blanks produced by FSW seems promising in the manufacture of complex sheet metal parts with high depths....

  1. Biomedical Titanium alloy prostheses manufacturing by means of Superplastic and Incremental Forming processes

    Piccininni Antonio

    2016-01-01

    Full Text Available The present work collects some results of the three-years Research Program “BioForming“, funded by the Italian Ministry of Education (MIUR and aimed to investigate the possibility of using flexible sheet forming processes, i.e. Super Plastic Forming (SPF and Single Point Incremental Forming (SPIF, for the manufacturing of patient-oriented titanium prostheses. The prosthetic implants used as case studies were from the skull; in particular, two different Ti alloys and geometries were considered: one to be produced in Ti-Gr23 by SPF and one to be produced in Ti-Gr2 by SPIF. Numerical simulations implementing material behaviours evaluated by characterization tests were conducted in order to design both the manufacturing processes. Subsequently, experimental tests were carried out implementing numerical results in terms of: (i gas pressure profile able to determine a constant (and optimal strain rate during the SPF process; (ii tool path able to avoid rupture during the SPIF process. Post forming characteristics of the prostheses in terms of thickness distributions were measured and compared to data from simulations for validation purposes. A good correlation between numerical and experimental thickness distributions has been obtained; in addition, the possibility of successfully adopting both the SPF and the SPIF processes for the manufacturing of prostheses has been demonstrated.

  2. Aluminium sheet forming at elevated temperatures

    van den Boogaard, Antonius H.; Bolt, P.J.; Werkhoven, R.J.

    2001-01-01

    The formability of aluminum sheet depends on the temperature of the material and the strain rate. E.g. the limiting drawing ratio can be improved by increasing the temperature uniformly, but even more by heating the flange and cooling the punch. To accurately simulate the deep drawing or stretching

  3. Reducing workpieces to their base geometry for multi-step incremental forming using manifold harmonics

    Carette, Yannick; Vanhove, Hans; Duflou, Joost

    2018-05-01

    Single Point Incremental Forming is a flexible process that is well-suited for small batch production and rapid prototyping of complex sheet metal parts. The distributed nature of the deformation process and the unsupported sheet imply that controlling the final accuracy of the workpiece is challenging. To improve the process limits and the accuracy of SPIF, the use of multiple forming passes has been proposed and discussed by a number of authors. Most methods use multiple intermediate models, where the previous one is strictly smaller than the next one, while gradually increasing the workpieces' wall angles. Another method that can be used is the manufacture of a smoothed-out "base geometry" in the first pass, after which more detailed features can be added in subsequent passes. In both methods, the selection of these intermediate shapes is freely decided by the user. However, their practical implementation in the production of complex freeform parts is not straightforward. The original CAD model can be manually adjusted or completely new CAD models can be created. This paper discusses an automatic method that is able to extract the base geometry from a full STL-based CAD model in an analytical way. Harmonic decomposition is used to express the final geometry as the sum of individual surface harmonics. It is then possible to filter these harmonic contributions to obtain a new CAD model with a desired level of geometric detail. This paper explains the technique and its implementation, as well as its use in the automatic generation of multi-step geometries.

  4. Explosive force of primacord grid forms large sheet metal parts

    1966-01-01

    Primacord which is woven through fish netting in a grid pattern is used for explosive forming of large sheet metal parts. The explosive force generated by the primacord detonation is uniformly distributed over the entire surface of the sheet metal workpiece.

  5. Modeling of AlMg Sheet Forming at Elevated Temperatures

    van den Boogaard, Antonius H.; Bolt, P.; Werkhoven, R.

    2001-01-01

    The process limits of aluminum sheet forming processes can be improved by control-ling local flow behavior by means of elevated temperatures and temperature gradients. In order to accurately model the deep drawing or stretching of aluminum sheet at elevated temperatures, a model is required that

  6. Liquid Film Migration in Warm Formed Aluminum Brazing Sheet

    Benoit, M. J.; Whitney, M. A.; Wells, M. A.; Jin, H.; Winkler, S.

    2017-10-01

    Warm forming has previously proven to be a promising manufacturing route to improve formability of Al brazing sheets used in automotive heat exchanger production; however, the impact of warm forming on subsequent brazing has not previously been studied. In particular, the interaction between liquid clad and solid core alloys during brazing through the process of liquid film migration (LFM) requires further understanding. Al brazing sheet comprised of an AA3003 core and AA4045 clad alloy, supplied in O and H24 tempers, was stretched between 0 and 12 pct strain, at room temperature and 523K (250 °C), to simulate warm forming. Brazeability was predicted through thermal and microstructure analysis. The rate of solid-liquid interactions was quantified using thermal analysis, while microstructure analysis was used to investigate the opposing processes of LFM and core alloy recrystallization during brazing. In general, liquid clad was consumed relatively rapidly and LFM occurred in forming conditions where the core alloy did not recrystallize during brazing. The results showed that warm forming could potentially impair brazeability of O temper sheet by extending the regime over which LFM occurs during brazing. No change in microstructure or thermal data was found for H24 sheet when the forming temperature was increased, and thus warm forming was not predicted to adversely affect the brazing performance of H24 sheet.

  7. FEM simulation of multi step forming of thick sheet

    Wisselink, H.H.; Huetink, Han

    2004-01-01

    A case study has been performed on the forming of an industrial product. This product, a bracket, is made of 5mm thick sheet in multiple steps. The process exists of a bending step followed by a drawing and a flanging step. FEM simulations have been used to investigate this forming process. First,

  8. Research Status on the Heterogeneous Sheet Connection Forming Technology

    SHI Wen-yong

    2017-04-01

    Full Text Available The heterogeneous sheet connection forming is one of the effective ways to realize lightweight in many fields,such as equipment manufacturing and transportation. However, there are obvious differences in the material properties,when using the traditional connection methods,there is a certain technical bottlenecks. In this paper, the technological characteristics and research status of the welding method and mechanical connection method are discussed in detail,such as the TIC welding and the laser welding. The advantages and development potential of the technology are introduced in the field of the heterogeneous sheet connection,in combination with the industry development and the use demand,the development of the heterogeneous sheet connection technology is expected,to provide the technical support for the research and development of new heterogeneous sheet connection technology.

  9. Comparison of plastic strains on AA5052 by single point incremental forming process using digital image processing

    Mugendiran, V.; Gnanavelbabu, A. [Anna University, Chennai, Tamilnadu (India)

    2017-06-15

    In this study, a surface based strain measurement was used to determine the formability of the sheet metal. A strain measurement may employ manual calculation of plastic strains based on the reference circle and the deformed circle. The manual calculation method has a greater margin of error in the practical applications. In this paper, an attempt has been made to compare the formability by implementing three different theoretical approaches: Namely conventional method, least square method and digital based strain measurements. As the sheet metal was formed by a single point incremental process the etched circles get deformed into elliptical shapes approximately, image acquisition has been done before and after forming. The plastic strains of the deformed circle grids are calculated based on the non- deformed reference. The coordinates of the deformed circles are measured by various image processing steps. Finally the strains obtained from the deformed circle are used to plot the forming limit diagram. To evaluate the accuracy of the system, the conventional, least square and digital based method of prediction of the forming limit diagram was compared. Conventional method and least square method have marginal error when compared with digital based processing method. Measurement of strain based on image processing agrees well and can be used to improve the accuracy and to reduce the measurement error in prediction of forming limit diagram.

  10. Comparison of plastic strains on AA5052 by single point incremental forming process using digital image processing

    Mugendiran, V.; Gnanavelbabu, A.

    2017-01-01

    In this study, a surface based strain measurement was used to determine the formability of the sheet metal. A strain measurement may employ manual calculation of plastic strains based on the reference circle and the deformed circle. The manual calculation method has a greater margin of error in the practical applications. In this paper, an attempt has been made to compare the formability by implementing three different theoretical approaches: Namely conventional method, least square method and digital based strain measurements. As the sheet metal was formed by a single point incremental process the etched circles get deformed into elliptical shapes approximately, image acquisition has been done before and after forming. The plastic strains of the deformed circle grids are calculated based on the non- deformed reference. The coordinates of the deformed circles are measured by various image processing steps. Finally the strains obtained from the deformed circle are used to plot the forming limit diagram. To evaluate the accuracy of the system, the conventional, least square and digital based method of prediction of the forming limit diagram was compared. Conventional method and least square method have marginal error when compared with digital based processing method. Measurement of strain based on image processing agrees well and can be used to improve the accuracy and to reduce the measurement error in prediction of forming limit diagram.

  11. Forming processes and mechanics of sheet metal forming

    Burchitz, I.A.

    2004-01-01

    The report is dealing with the numerical analysis of forming processes. Forming processes is the large group of manufacturing processes used to obtain various product shapes by means of plastic deformations. The report is organized as follows. An overview of the deformation processes and the

  12. Development of a low energy micro sheet forming machine

    Razali, A. R.; Ann, C. T.; Shariff, H. M.; Kasim, N. I.; Musa, M. A.; Ahmad, A. F.

    2017-10-01

    It is expected that with the miniaturization of materials being processed, energy consumption is also being `miniaturized' proportionally. The focus of this study was to design a low energy micro-sheet-forming machine for thin sheet metal application and fabricate a low direct current powered micro-sheet-forming machine. A prototype of low energy system for a micro-sheet-forming machine which includes mechanical and electronic elements was developed. The machine was tested for its performance in terms of natural frequency, punching forces, punching speed and capability, energy consumption (single punch and frequency-time based). Based on the experiments, the machine can do 600 stroke per minute and the process is unaffected by the machine's natural frequency. It was also found that sub-Joule of power was required for a single stroke of punching/blanking process. Up to 100micron thick carbon steel shim was successfully tested and punched. It concludes that low power forming machine is feasible to be developed and be used to replace high powered machineries to form micro-products/parts.

  13. Testing of environmentally friendly lubricants for sheet metal forming

    Bay, Niels; Olsson, David Dam; Andreasen, Jan Lasson

    2005-01-01

    the authors have especially been involved in the development of a system of test methods for sheet metal forming and in testing of friction and limits of lubrication of new, environmentally friendly lubricants. An overview of the developed tests is presented together with selected results....

  14. Efficient implicit FEM simulation of sheet metal forming

    van den Boogaard, Antonius H.; Meinders, Vincent T.; Huetink, Han

    2003-01-01

    For the simulation of industrial sheet forming processes, the time discretisation is one of the important factors that determine the accuracy and efficiency of the algorithm. For relatively small models, the implicit time integration method is preferred, because of its inherent equilibrium check.

  15. Warm forming simulation of Al-Mg sheet

    Kurukuri, S.; van den Boogaard, Antonius H.; Miroux, A.; Holmedal, B.

    2009-01-01

    The accuracy of warm forming simulations depends to a large extend on the description of the yield surface with temperature and strain-rate dependent hardening and on the modeling of friction. In this paper, the anisotropic behavior of the sheet is described by using the Vegter yield locus, which is

  16. Forming properties and springback evaluation of copper beryllium sheets

    Tseng, A.A.; Jen, K.P.; Chen, T.C.; Kondetimmamhalli, R.

    1995-01-01

    Copper beryllium (CuBe) alloys possess excellent strength and conductivity. They have become the most important materials used for producing high reliability connectors and interconnections for electrical and electronic applications. As demand for high connection density in electrical and electronic products grows, springback behaviors become increasingly critical in fabricating these miniaturized contact components from sheet base materials. In the present article, a study of the springback behavior of CuBe sheets under different heat treatments is presented, with the goal of providing reliable information needed for fabricating more intricate connection parts. Both experimental and analytical techniques were adopted. The tensile tester was first used to study the springback related tensile properties. The governing tensile parameters on springback were identified, and their variations for sheets with different heat treatments were studied. It was found that a bilinear constitutive relationship can be characterize the stress strain behavior of the CuBe alloy. A closed form solution based on this bilinear relationship was formulated to predict the springback for the CuBe sheets at bending conditions. A V-shaped bend tester having an interchangeable punch to accommodate multiple radii was designed and built to evaluate the springback properties of CuBe sheets. A good correlation was found between the analytical predictions and experimental data. A parametric study, as an example, was also performed to provide the springback information needed for designing complicated connectors

  17. Cold Forming of Ni-Ti Shape Memory Alloy Sheet

    Fann, Kaung-Jau; Su, Jhe-Yung

    2018-03-01

    Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its further application, this study attempts to investigate the feasibility of cold forming its sheet blank especially under a bi-axial tensile stress state. Not only experiments but also a Finite Element Analysis (FEA) with DEFORM 2D was conducted in this study. The material data for FEA was accomplished by the tensile test. An Erichsen-like cupping test was performed as well to determine the process parameter for experiment setup. As a result of the study, the Ni-Ti shape memory alloy sheet has a low formability for cold forming and shows a relative large springback after releasing the forming load.

  18. A System of Test Methods for Sheet Metal Forming Tribology

    Bay, Niels; Olsson, David Dam; Andreasen, Jan Lasson

    2007-01-01

    Sheet metal forming of tribologically difficult materials such as stainless steel, Al-alloys and Ti-alloys or forming in tribologically difficult operations like ironing, punching or deep drawing of thick plate requires often use of environmentally hazardous lubricants such as chlorinated paraffin...... oils in order to avoid galling. The present paper describes a systematic research in the development of new, environmentally harmless lubricants focusing on the lubricant testing aspects. A system of laboratory tests has been developed to study the lubricant performance under the very varied conditions...... appearing in different sheet forming operations such as stamping, deep drawing, ironing and punching. The laboratory tests have been especially designed to model the conditions in industrial production....

  19. Multi Scale Models for Flexure Deformation in Sheet Metal Forming

    Di Pasquale Edmondo

    2016-01-01

    Full Text Available This paper presents the application of multi scale techniques to the simulation of sheet metal forming using the one-step method. When a blank flows over the die radius, it undergoes a complex cycle of bending and unbending. First, we describe an original model for the prediction of residual plastic deformation and stresses in the blank section. This model, working on a scale about one hundred times smaller than the element size, has been implemented in SIMEX, one-step sheet metal forming simulation code. The utilisation of this multi-scale modeling technique improves greatly the accuracy of the solution. Finally, we discuss the implications of this analysis on the prediction of springback in metal forming.

  20. Incremental Validity of the Trait Emotional Intelligence Questionnaire-Short Form (TEIQue-SF).

    Siegling, A B; Vesely, Ashley K; Petrides, K V; Saklofske, Donald H

    2015-01-01

    This study examined the incremental validity of the adult short form of the Trait Emotional Intelligence Questionnaire (TEIQue-SF) in predicting 7 construct-relevant criteria beyond the variance explained by the Five-factor model and coping strategies. Additionally, the relative contributions of the questionnaire's 4 subscales were assessed. Two samples of Canadian university students completed the TEIQue-SF, along with measures of the Big Five, coping strategies (Sample 1 only), and emotion-laden criteria. The TEIQue-SF showed consistent incremental effects beyond the Big Five or the Big Five and coping strategies, predicting all 7 criteria examined across the 2 samples. Furthermore, 2 of the 4 TEIQue-SF subscales accounted for the measure's incremental validity. Although the findings provide good support for the validity and utility of the TEIQue-SF, directions for further research are emphasized.

  1. Research on Al-alloy sheet forming formability during warm/hot sheet hydroforming based on elliptical warm bulging test

    Cai, Gaoshen; Wu, Chuanyu; Gao, Zepu; Lang, Lihui; Alexandrov, Sergei

    2018-05-01

    An elliptical warm/hot sheet bulging test under different temperatures and pressure rates was carried out to predict Al-alloy sheet forming limit during warm/hot sheet hydroforming. Using relevant formulas of ultimate strain to calculate and dispose experimental data, forming limit curves (FLCS) in tension-tension state of strain (TTSS) area are obtained. Combining with the basic experimental data obtained by uniaxial tensile test under the equivalent condition with bulging test, complete forming limit diagrams (FLDS) of Al-alloy are established. Using a quadratic polynomial curve fitting method, material constants of fitting function are calculated and a prediction model equation for sheet metal forming limit is established, by which the corresponding forming limit curves in TTSS area can be obtained. The bulging test and fitting results indicated that the sheet metal FLCS obtained were very accurate. Also, the model equation can be used to instruct warm/hot sheet bulging test.

  2. Formability models for warm sheet metal forming analysis

    Jiang, Sen

    Several closed form models for the prediction of strain space sheet metal formability as a function of temperature and strain rate are proposed. The proposed models require only failure strain information from the uniaxial tension test at an elevated temperature setting and failure strain information from the traditionally defined strain space forming limit diagram at room temperature, thereby featuring the advantage of offering a full forming limit description without having to carry out expensive experimental studies for multiple modes of deformation under the elevated temperature. The Power law, Voce, and Johnson-Cook hardening models are considered along with the yield criterions of Hill's 48 and Logan-Hosford yield criteria. Acceptable correlations between the theory and experiment are reported for all the models under a plane strain condition. Among all the proposed models, the model featuring Johnson-Cook hardening model and Logan-Hosford yield behavior (LHJC model) was shown to best correlate with experiment. The sensitivity of the model with respect to various forming parameters is discussed. This work is significant to those aiming to incorporate closed-form formability models directly into numerical simulation programs for the purpose of design and analysis of products manufactured through the warm sheet metal forming process. An improvement based upon Swift's diffuse necking theory, is suggested in order to enhance the reliability of the model for biaxial stretch conditions. Theory relating to this improvement is provided in Appendix B.

  3. New developments in tribomechanical modeling of automotive sheet steel forming

    Khandeparkar, Tushar; Chezan, Toni; van Beeck, Jeroen

    2018-05-01

    Forming of automotive sheet metal body panels is a complex process influenced by both the material properties and contact conditions in the forming tooling. Material properties are described by the material constitutive behavior and the material flow into the forming die can be described by the tribological system. This paper investigates the prediction accuracy of the forming process using the Tata Steel state of the art description of the material constitutive behavior in combination with different friction models. A cross-die experiment is used to investigate the accuracy of local deformation modes typically seen in automotive sheet metal forming operations. Results of advanced friction models as well as the classical Coulomb friction description are compared to the experimentally measured strain distribution and material draw-in. Two hot-dip galvanized coated steel forming grades were used for the investigations. The results show that the accuracy of the simulation is not guaranteed by the advanced friction models for the entire investigated blank holder force range, both globally and locally. A measurable difference between the calculated and measured local strains is seen for both studied models even in the case where the global indicator, i.e. the draw-in, is well predicted.

  4. Testing of Lubricant Performance in Sheet Metal Forming

    Bay, Niels; Olsson, David Dam; Friis, Kasper Leth

    2008-01-01

    Increasing focus on environmental issues in industrial production has urged a number of sheet metal forming companies to look for new tribo-systems in order to substitute hazardous lubricants such as chlorinated paraffin oils. The problems are especially pronounced, when forming tribologically...... of the lubricant film causing pick-up of work piece material on the tool surface and scoring of subsequent work piece surfaces. The present paper gives an overview of more than 10 years work by the authors’ research group through participation in national as well as international framework programmes on developing...

  5. Technological aspects regarding machining the titanium alloys by means of incremental forming

    Bologa Octavian

    2017-01-01

    Full Text Available Titanium alloys are materials with reduced formability, due to their low plasticity. However, today there are high demands regarding their use in the automotive industry and in bio-medical industry, for prosthetic devices. This paper presents some technological aspects regarding the machinability of titanium alloys by means of incremental forming. The research presented in this paper aimed to demonstrate that the parts made from these materials could be machined at room temperature, in certain technological conditions.

  6. Growth of plutons by incremental emplacement of sheets in crystal-rich host: Evidence from Miocene intrusions of the Colorado River region, Nevada, USA

    Miller, C.F.; Furbish, D.J.; Walker, B.A.; Claiborne, L.L.; Koteas, G.C.; Bleick, H.A.; Miller, J.S.

    2011-01-01

    Growing evidence supports the notion that plutons are constructed incrementally, commonly over long periods of time, yet field evidence for the multiple injections that seem to be required is commonly sparse or absent. Timescales of up to several million years, among other arguments, indicate that the dominant volume does not remain largely molten, yet if growing plutons are constructed from rapidly solidifying increments it is unlikely that intrusive contacts would escape notice. A model wherein magma increments are emplaced into melt-bearing but crystal-rich host, rather than either solid or crystal-poor material, provides a plausible explanation for this apparent conundrum. A partially solidified intrusion undoubtedly comprises zones with contrasting melt fraction and therefore strength. Depending on whether these zones behave elastically or ductilely in response to dike emplacement, intruding magma may spread to form sheets by either of two mechanisms. If the melt-bearing host is elastic on the relevant timescale, magma spreads rather than continuing to propagate upward, where it encounters a zone of higher rigidity (higher crystal fraction). Similarly, if the dike at first ascends through rigid, melt-poor material and then encounters a zone that is weak enough (poor enough in crystals) to respond ductilely, the ascending material will also spread because the dike tip ceases to propagate as in rigid material. We propose that ascending magma is thus in essence trapped, by either mechanism, within relatively crystal-poor zones. Contacts will commonly be obscure from the start because the contrast between intruding material (crystal-poorer magma) and host (crystal-richer material) is subtle, and they may be obscured even further by subsequent destabilization of the crystal-melt framework. Field evidence and zircon zoning stratigraphy in plutons of the Colorado River region of southern Nevada support the hypothesis that emplacement of magma replenishments into a

  7. Single-Point Incremental Forming of Two Biocompatible Polymers: An Insight into Their Thermal and Structural Properties

    Luis Marcelo Lozano-Sánchez

    2018-04-01

    Full Text Available Sheets of polycaprolactone (PCL and ultra-high molecular weight polyethylene (UHMWPE were fabricated and shaped by the Single-Point Incremental Forming process (SPIF. The performance of these biocompatible polymers in SPIF was assessed through the variation of four main parameters: the diameter of the forming tool, the spindle speed, the feed rate, and the step size based on a Box–Behnken design of experiments of four variables and three levels. The design of experiments allowed us to identify the parameters that most affect the forming of PCL and UHMWPE. The study was completed by means of a deep characterization of the thermal and structural properties of both polymers. These properties were correlated to the performance of the polymers observed in SPIF, and it was found that the polymer chains are oriented as a consequence of the SPIF processing. Moreover, by X-ray diffraction it was proved that polymer chains behave differently on each surface of the fabricated parts, since the chains on the surface in contact with the forming tool are oriented horizontally, while on the opposite surface they are oriented in the vertical direction. The unit cell of UHMWPE is distorted, passing from an orthorhombic cell to a monoclinic due to the slippage between crystallites. This slippage between crystallites was observed in both PCL and UHMWPE, and was identified as an alpha star thermal transition located in the rubbery region between the glass transition and the melting point of each polymer.

  8. Multi-objective optimization under uncertainty for sheet metal forming

    Lafon Pascal

    2016-01-01

    Full Text Available Aleatory uncertainties in material properties, blank thickness and friction condition are inherent and irreducible variabilities in sheet metal forming. Optimal design configurations, which are obtained by conventional design optimization methods, are not always able to meet the desired targets due to the effect of uncertainties. This paper proposes a multi-objective robust design optimization that aims to tackle this problem. Results obtained on a U shape draw bending benchmark show that spring-back effect can be controlled by optimizing process parameters.

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

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

    2005-01-01

    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

  10. Forming limit and fracture mechanism of ferritic stainless steel sheets

    Xu Le; Barlat, Frederic; Ahn, Deok Chan; Bressan, Jose Divo

    2011-01-01

    Research highlights: → Forming limit curves of two ferritic stainless steel sheets were well predicted. → Failure occurs by necking in uniaxial and plane strain tension for both materials. → Failure occurs by shearing in balanced biaxial tension for both materials. → Strain rate sensitivity does not affect the limit strains a lot for both materials. → Strain rate sensitivity likely influences the failure mode for both materials. - Abstract: In this work, the forming limit curves (FLCs) of two ferritic stainless steel sheets, AISI409L and AISI430, were predicted with the Marciniak-Kuczynski (MK) and Bressan-William-Hill (BWH) models, combined with the Yld2000-2d yield function and the Swift hardening law. Uniaxial tension, disk compression and hydraulic bulge tests were performed to determine the yield loci and hardening curves of both materials. Meanwhile, the strain rate sensitivity (SRS) coefficient was measured through uniaxial tension tests carried out at different strain rates. Out-of-plane stretching tests were conducted in sheet specimens to obtain the surface limit strains under different linear strain paths. Micrographs of the specimens fractured in different stress states were obtained by optical and scanning electron microscopy. The overall results show that the BWH model can predict the FLC better than the MK model, and that the SRS does not have much effect on the limit strains for both materials. The predicted FLCs and micrograph analysis both indicate that failure occurs by surface localized necking in uniaxial and plane strain tension states, whereas it occurs by localized shearing in the through thickness direction in balanced biaxial tension state.

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

    Ofenheimer, Aldo; Buchmayr, Bruno; Kolleck, Ralf; Merklein, Marion

    2005-01-01

    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

  12. Springback of aluminum alloy brazing sheet in warm forming

    Han, Kyu Bin; George, Ryan; Kurukuri, Srihari; Worswick, Michael J.; Winkler, Sooky

    2017-10-01

    The use of aluminum is increasing in the automotive industry due to its high strength-to-weight ratio, recyclability and corrosion resistance. However, aluminum is prone to significant springback due to its low elastic modulus coupled with its high strength. In this paper, a warm forming process is studied to improve the springback characteristics of 0.2 mm thick brazing sheet with an AA3003 core and AA4045 clad. Warm forming decreases springback by lowering the flow stress. The parts formed have complex features and geometries that are representative of automotive heat exchangers. The key objective is to utilize warm forming to control the springback to improve the part flatness which enables the use of harder temper material with improved strength. The experiments are performed by using heated dies at several different temperatures up to 350 °C and the blanks are pre-heated in the dies. The measured springback showed a reduction in curvature and improved flatness after forming at higher temperatures, particularly for the harder temper material conditions.

  13. 48 CFR 53.301-1427 - Standard Form 1427, Inventory Schedule A-Construction Sheet (Metals in Mill Product Form).

    2010-10-01

    ... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Standard Form 1427, Inventory Schedule A-Construction Sheet (Metals in Mill Product Form). 53.301-1427 Section 53.301-1427... Illustrations of Forms 53.301-1427 Standard Form 1427, Inventory Schedule A—Construction Sheet (Metals in Mill...

  14. Design of process parameters for the incremental tube forming (ITF) by FEM to control product properties

    Nazari, Esmaeil; Löbbe, Christian; Gallus, Stefan; Izadyar, S. Ahmad; Tekkaya, A. Erman

    2018-05-01

    The incremental tube forming (ITF) is a process combination of the kinematic tube bending and spinning to shape high strength and tailored tubes with variable diameters and thicknesses. In contrast to conventional bending methods, the compressive stress superposition by the spinning process facilitates low bending stresses, so that geometrical errors are avoided and the shape accuracy is improved. The study reveals the interaction of plastic strains of the rolling and bending process through an explicit FEM investigation. For this purpose, the three-dimensional machine set-up is discretized and modeled in terms of the fully disclosed spinning process during the gradual deflection of the tube end for bending. The analysis shows that, depending on the forming tool shape, the stress superposition is accompanied by high plastic strains. Furthermore, this phenomenon is explained by the three dimensional normal and shear strains during the incremental spinning. Analyzing the strains history also shows a nonlinearity between the strains by bending and spinning. It is also shown that process parameters like rotational velocity of the spinning rolls have a huge influence on the deformation pattern. Finally, the method is used for the manufacturing of an example product, which reveals the high process flexibility. In one clamp a component with a graded wall thickness and outside diameter along the longitudinal axis is produced.

  15. Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes.

    Zhou, Du; Yuan, Xi; Gao, Haoxiang; Wang, Ailing; Liu, Jun; El Fakir, Omer; Politis, Denis J; Wang, Liliang; Lin, Jianguo

    2016-12-13

    The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques. This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

  16. Advanced Gradient Based Optimization Techniques Applied on Sheet Metal Forming

    Endelt, Benny; Nielsen, Karl Brian

    2005-01-01

    The computational-costs for finite element simulations of general sheet metal forming processes are considerable, especially measured in time. In combination with optimization, the performance of the optimization algorithm is crucial for the overall performance of the system, i.e. the optimization algorithm should gain as much information about the system in each iteration as possible. Least-square formulation of the object function is widely applied for solution of inverse problems, due to the superior performance of this formulation.In this work focus will be on small problems which are defined as problems with less than 1000 design parameters; as the majority of real life optimization and inverse problems, represented in literature, can be characterized as small problems, typically with less than 20 design parameters.We will show that the least square formulation is well suited for two classes of inverse problems; identification of constitutive parameters and process optimization.The scalability and robustness of the approach are illustrated through a number of process optimizations and inverse material characterization problems; tube hydro forming, two step hydro forming, flexible aluminum tubes, inverse identification of material parameters

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

    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.

  18. Control of anisotropic shape deviation in single point incremental forming of paperboard

    Stein, Philipp; Franke, Wilken; Hoppe, Florian; Hesse, Daniel; Mill, Katharina; Groche, Peter

    2017-10-01

    The increasing social demand for sustainable material use leads to new process strategies as well as to the use of new materials in nearly all industries. In light of this demand, paperboard shows potential to substitute polymer-based components while also exhibiting improved ecological properties. However, in contrast to polymer-based products, the forming limits of paperboard are relatively low. Therefore, three dimensional forming of paperboard is subject of current research. One area of research focuses on the control of the fiber orientation dependent anisotropic material behavior of industrial paperboard in forming processes. For an examined industrial paperboard, an average elongation at break of 1.2% in the so called machine direction (fiber preferential direction, MD) has been determined at standard climate conditions. In contrast, in cross-direction (orthogonal to the machine direction, CD) a value of 2.6% was observed. With increased moisture content of the specimens the difference between the mechanical properties in MD and CD even increases. As a result of the various fiber-orientation dependent mechanical properties, forming with symmetric tools leads to asymmetrically shaped final parts. Within this article, an approach to reduce the asymmetric shape of three-dimensional formed paperboard by using single point incremental forming technology is presented. For a free spatial processing strategy the 3D Servo Press Technology, which enables circular as well as free processing strategies, is used. Based on reference tests with a circular processing strategy, it is shown that by using an adapted, elliptical tool path, an almost symmetric shaped part can be formed.

  19. Modelling of aluminium sheet forming at elevated temperatures

    van den Boogaard, Antonius H.; Huetink, Han

    2004-01-01

    The formability of Al–Mg sheet can be improved considerably, by increasing the temperature. By heating the sheet in areas with large shear strains, but cooling it on places where the risk of necking is high, the limiting drawing ratio can be increased to values above 2.5. At elevated temperatures,

  20. Numerical study of multi-point forming of thick sheet using remeshing procedure

    Cherouat, A.; Ma, X.; Borouchaki, H.; Zhang, Q.

    2018-05-01

    Multi-point forming MPF is an innovative technology of manufacturing complex thick sheet metal products without the need for solid tools. The central component of this system is a pair of the desired discrete matrices of punches, and die surface constructed by changing the positions of the tools though CAD and a control system. Because reconfigurable discrete tools are used, part-manufacturing costs are reduced and manufacturing time is shorten substantially. Firstly, in this work we develop constitutive equations which couples isotropic ductile damage into various flow stress based on the Continuum Damage Mechanic theory. The modified Johnson-Cook flow model fully coupled with an isotropic ductile damage is established using the quasi-unilateral damage evolution for considering both the open and the close of micro-cracks. During the forming processes severe mesh distortion of elements occur after a few incremental forming steps. Secondly, we introduce 3D adaptive remeshing procedure based on linear tetrahedral element and geometrical/physical errors estimation to optimize the element quality, to refine the mesh size in the whole model and to adapt the deformed mesh to the tools geometry. Simulation of the MPF process (see Fig. 1) and the unloading spring-back are carried out using adaptive remeshing scheme using the commercial finite element package ABAQUS and OPTIFORM mesher. Subsequently, influencing factors of MPF spring-back are researched to investigate the MPF spring-back tendency with the proposed remeshing procedure.

  1. Multi-scale contact modeling of coated steels for sheet metal forming applications

    Shisode, Meghshyam; Hazrati Marangalou, Javad; Mishra, Tanmaya; De Rooij, Matthijn; Van Den Boogaard, Ton; Bay, Niels; Nielsen, Chris V.

    2018-01-01

    Friction in sheet metal forming is a local phenomenon which depends on continuously evolving contact conditions during the forming process. This is mainly influenced by local contact pressure, surface textures of the sheet metal as well as the forming tool surface profile and material behavior. The

  2. Friction and lubrication modelling in sheet metal forming: Influence of lubrication amount, tool roughness and sheet coating on product quality

    Hol, J.; Wiebenga, J. H.; Carleer, B.

    2017-09-01

    In the stamping of automotive parts, friction and lubrication play a key role in achieving high quality products. In the development process of new automotive parts, it is therefore crucial to accurately account for these effects in sheet metal forming simulations. This paper presents a selection of results considering friction and lubrication modelling in sheet metal forming simulations of a front fender product. For varying lubrication conditions, the front fender can either show wrinkling or fractures. The front fender is modelled using different lubrication amounts, tool roughness’s and sheet coatings to show the strong influence of friction on both part quality and the overall production stability. For this purpose, the TriboForm software is used in combination with the AutoForm software. The results demonstrate that the TriboForm software enables the simulation of friction behaviour for varying lubrication conditions, i.e. resulting in a generally applicable approach for friction characterization under industrial sheet metal forming process conditions.

  3. NUMISHEET 2016: 10th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes

    2016-01-01

    The NUMISHEET conference series have been established as a world-class forum through which new intellectual ideas and technologies in the area of sheet metal forming simulation are exchanged. Previous NUMISHEET conferences have given enormous contributions to industry and academia in what regards the development of new methods and ideas for the numerical simulation of sheet metal forming processes. Previous NUMISHEET conferences were held in: Zurich (Switzerland, 1991), Isehara (Japan, 1993), Dearborn (USA, 1996), Besancon (France, 1999), Jeju Island (South Korea, 2002), Detroit (USA, 2005), Interlaken (Switzerland, 2008), Seoul (South Korea, 2011) and Melbourne (Australia, 2014). The NUMISHEET 2016 conference will be held in Bristol, UK. It features technical, keynote and plenary sessions and mini-symposiums in diverse sheet metal forming areas including the recently introduced incremental sheet forming and electromagnetic forming, as well as new prominent numerical methods such as IsoGeometric Analysis and meshless methods for sheet analysis. NUMISHEET 2016 will have eight academic plenary lectures delivered by worldwide recognised experts in the areas of sheet metal forming, material modelling and numerical methods in general. Also, NUMISHEET 2016 will have three industrial plenary lectures which will be addressed by three different companies with strong businesses in sheet metal forming processes: AutoForm, Crown Technology and Jaguar Land Rover. One of the most distinguishing features of NUMISHEET conference series is the industrial benchmark sessions, during which numerical simulations of industrial sheet formed parts are compared with experimental results from the industry. The benchmark sessions provide an extraordinary opportunity for networking, for the exchange of technologies related to sheet metal forming and for the numerical validation of sheet metal forming codes/software. Three benchmark studies have been organised in NUMISHEET 2016: BM1) &apos

  4. 3D tissue formation by stacking detachable cell sheets formed on nanofiber mesh.

    Kim, Min Sung; Lee, Byungjun; Kim, Hong Nam; Bang, Seokyoung; Yang, Hee Seok; Kang, Seong Min; Suh, Kahp-Yang; Park, Suk-Hee; Jeon, Noo Li

    2017-03-23

    We present a novel approach for assembling 3D tissue by layer-by-layer stacking of cell sheets formed on aligned nanofiber mesh. A rigid frame was used to repeatedly collect aligned electrospun PCL (polycaprolactone) nanofiber to form a mesh structure with average distance between fibers 6.4 µm. When human umbilical vein endothelial cells (HUVECs), human foreskin dermal fibroblasts, and skeletal muscle cells (C2C12) were cultured on the nanofiber mesh, they formed confluent monolayers and could be handled as continuous cell sheets with areas 3 × 3 cm 2 or larger. Thicker 3D tissues have been formed by stacking multiple cell sheets collected on frames that can be nested (i.e. Matryoshka dolls) without any special tools. When cultured on the nanofiber mesh, skeletal muscle, C2C12 cells oriented along the direction of the nanofibers and differentiated into uniaxially aligned multinucleated myotube. Myotube cell sheets were stacked (upto 3 layers) in alternating or aligned directions to form thicker tissue with ∼50 µm thickness. Sandwiching HUVEC cell sheets with two dermal fibroblast cell sheets resulted in vascularized 3D tissue. HUVECs formed extensive networks and expressed CD31, a marker of endothelial cells. Cell sheets formed on nanofiber mesh have a number of advantages, including manipulation and stacking of multiple cell sheets for constructing 3D tissue and may find applications in a variety of tissue engineering applications.

  5. The Forming of AISI 409 sheets for fan blade manufacturing

    Foroni, F. D.; Menezes, M. A.; Moreira Filho, L. A.

    2007-01-01

    The necessity of adapting the standardized fan models to conditions of higher temperature has emerged due to the growth of concern referring to the consequences of the gas expelling after the Mont Blanc tunnel accident in Italy and France, where even though, with 100 fans in operation, 41 people died. The objective of this work is to present an alternative to the market standard fans considering a new technology in constructing blades. This new technology introduces the use of the stainless steel AISI 409 due to its good to temperatures of gas exhaust from tunnels in fire situation. The innovation is centered in the process of a deep drawing of metallic sheets in order to keep the ideal aerodynamic superficies for the fan ideal performance. Through the impression of circles on the sheet plane it is shown, experimentally, that, during the pressing process, the more deformed regions on the sheet plane of the blade can not reach the deformation limits of the utilized sheet material

  6. A material model for aluminium sheet forming at elevated temperatures

    van den Boogaard, Antonius H.; Werkhoven, R.J.; Bolt, P.J.

    2001-01-01

    In order to accurately simulate the deep drawing or stretching of aluminum sheet at elevated temperatures, a model is required that incorporates the temperature and strain-rate dependency of the material. In this paper two models are compared: a phenomenological material model in which the

  7. Breakup characteristics of power-law liquid sheets formed by two impinging jets

    Bai, Fuqiang; Diao, Hai; Chang, Qing; Wang, Endong; Du, Qing; Zhang, Mengzheng

    2014-01-01

    The breakup characteristics of the shear-thinning power-law liquid sheets formed by two impinging jets have been investigated with the shadowgraph technique. This paper focuses on the effects of spray parameters (jet velocity), physical parameters (viscosity) and geometry parameters (impinging angle and nozzle cross-sectional shape) on the breakup behaviors of liquid sheets. The breakup mode, sheet length and expansion angle of the sheet are extracted from the spray images obtained by a high speed camera. Impinging angle and Weber number play the similar roles in promoting the breakup of liquid sheets. With the increase of jet velocity, five different breakup modes are observed and the expansion angle increases consistently after the closed-rim mode while the sheet length first increases and then decreases. But there exists a concave consisting of a fierce drop and a second rising process on the sheet length curve for the fluid with smaller viscosity. Different nozzle cross-sectional shapes emphasize significant effects on the sheet length and expansion angle of liquid sheets. At a fixed Weber number, the liquid sheet with greater viscosity has a greater sheet length and a smaller expansion angle due to the damping effect of viscosity. (papers)

  8. The Effect of Grinding and Polishing Procedure of Tool Steels in Sheet Metal Forming

    Lindvall, F.; Bergström, J.; Krakhmalev, P.

    2010-01-01

    The surface finish of tools in sheet metal forming has a large influence on the performance of the forming tool. Galling, concern of wear in sheet metal forming, is a severe form of adhesive wear where sheet material is transferred on to the tool surface. By polishing the tools to a fine surface ...... 40 and Vanadis 6 and up to ten different grinding and polishing treatments were tested against AISI 316 stainless steel. The tests showed that an optimum surface preparation might be found at the transition between abrasive and adhesive wear....

  9. Variation of rock-forming metals in sub-annual increments of modern Greenland snow

    Hinkley, T.K.

    1992-01-01

    Modern snowpack from central south Greenland was sampled in sub-seasonal increments and analysed for a suite of major, minor and trace rock-forming metals (K, Rb, Cs, Ca, Sr, Ba). There is a sharp seasonal concentration maximum for all six metals that comes in summer, later than mid-June. Metal concentrations in all other parts of the year's snowpack are up to 10 or more times smaller. The concentration maximum is preceded by low values in autumn-winter, very low values in early-mid-spring, and moderate-to-high values in late spring early summer; this pattern is seen consistently in three separate time stratigraphic intervals representing the same seasonal periods, spanning the time interval 1981-1984. The absolute concentration values of the snow strata representing the low-concentration portion of the year, autumn-winter-spring, may vary substantially from year to year, by a factor of two, or more. The finding that all rock-forming metals are at a sharp concentration maximum in late summer contrasts with the interpretations of several other studies in high-latitude northern regions. Those studies have reported a broad maximum of continental dust-associated metals in late winter and spring. However samples of the other studies have mostly come from regions farther to the north, and the analyses have emphasized industrial pollutant metals rather than the matched rock-forming suite of the present study. The metals measured were chosen to give information about the origin and identity of the rock and soil dusts, and sea salts, present as impurities in the snow. Metal ratios indicate that the dusts in the snowpacks are of continental origin and from ferromagnesian rocks. Source rock types for dusts in central south Greenland snow contrast with the felsic rock dusts of the Sierra Nevada, CA, annual snowpacks, and with the very felsic rock dusts in large south central Alaskan mountain glaciers. Samples in which masses of sea salt are much larger than those of rock dusts

  10. Investigation of Forming Performance of Laminated Steel Sheets Using Finite Element Analyses

    Liu Wenning; Sun Xin; Ruokolainen, Robert; Gayden Xiaohong

    2007-01-01

    Laminated steel sheets have been used in automotive structures for reducing in-cabin noise. However, due to the marked difference in material properties of the different laminated layers, integrating laminated steel parts into the manufacturing processes can be challenging. Especially, the behavior of laminated sheets during forming processes is very different from that of monolithic steel sheets. During the deep-draw forming process, large shear deformation and corresponding high interfacial stress may initiate and propagate interfacial cracks between the core polymer and the metal skin, hence degrading the performance of the laminated sheets. In this paper, the formability of the laminated steel sheets is investigated by means of numerical analysis. The goal of this work is to gain insight into the relationship between the individual properties of the laminated sheet layers and the corresponding formability of the laminated sheet as a whole, eventually leading to reliable design and successful forming process development of such materials. Finite element analyses of laminate sheet forming are presented. Effects of polymer core thickness and viscoelastic properties of the polymer core, as well as punching velocity, are also investigated

  11. A Dislocation based Constitutive Model for Warm Forming of Aluminum Sheet

    Kurukuri, S.; Ghosh, M.; van den Boogaard, Antonius H.

    2008-01-01

    The formability of aluminum sheet can be improved considerably by increasing the temperature. At elevated temperatures, the mechanical response of the material becomes strain rate dependent. To accurately simulate warm forming of aluminum sheet, a material model is required that incorporates the

  12. Principles for designing proteins with cavities formed by curved β sheets

    Marcos, Enrique; Basanta, Benjamin; Chidyausiku, Tamuka M.; Tang, Yuefeng; Oberdorfer, Gustav; Liu, Gaohua; Swapna, G. V. T.; Guan, Rongjin; Silva, Daniel-Adriano; Dou, Jiayi; Pereira, Jose Henrique; Xiao, Rong; Sankaran, Banumathi; Zwart, Peter H.; Montelione, Gaetano T.; Baker, David

    2017-01-12

    Active sites and ligand-binding cavities in native proteins are often formed by curved β sheets, and the ability to control β-sheet curvature would allow design of binding proteins with cavities customized to specific ligands. Toward this end, we investigated the mechanisms controlling β-sheet curvature by studying the geometry of β sheets in naturally occurring protein structures and folding simulations. The principles emerging from this analysis were used to design, de novo, a series of proteins with curved β sheets topped with α helices. Nuclear magnetic resonance and crystal structures of the designs closely match the computational models, showing that β-sheet curvature can be controlled with atomic-level accuracy. Our approach enables the design of proteins with cavities and provides a route to custom design ligand-binding and catalytic sites.

  13. Tool Monitoring and Electronic Event Logging for Sheet Metal Forming Processes

    Gerd Heiserich

    2010-06-01

    Full Text Available This contribution describes some innovative solutions regarding sensor systems for tool monitoring in the sheet metal industry. Autonomous and tamper-proof sensors, which are integrated in the forming tools, can detect and count the strokes carried out by a sheet metal forming press. Furthermore, an electronic event logger for documentary purposes and quality control was developed. Based on this technical solution, new business models such as leasing of sheet metal forming tools can be established for cooperation among enterprises. These models allow usage-based billing for the contractors, taking the effectively produced number of parts into account.

  14. Feature Size Effect on Formability of Multilayer Metal Composite Sheets under Microscale Laser Flexible Forming

    Huixia Liu

    2017-07-01

    Full Text Available Multilayer metal composite sheets possess superior properties to monolithic metal sheets, and formability is different from monolithic metal sheets. In this research, the feature size effect on formability of multilayer metal composite sheets under microscale laser flexible forming was studied by experiment. Two-layer copper/nickel composite sheets were selected as experimental materials. Five types of micro molds with different diameters were utilized. The formability of materials was evaluated by forming depth, thickness thinning, surface quality, and micro-hardness distribution. The research results showed that the formability of two-layer copper/nickel composite sheets was strongly influenced by feature size. With feature size increasing, the effect of layer stacking sequence on forming depth, thickness thinning ratio, and surface roughness became increasingly larger. However, the normalized forming depth, thickness thinning ratio, surface roughness, and micro-hardness of the formed components under the same layer stacking sequence first increased and then decreased with increasing feature size. The deformation behavior of copper/nickel composite sheets was determined by the external layer. The deformation extent was larger when the copper layer was set as the external layer.

  15. Surface Morphology and Bending Deformation of 2024-T3 Thin Sheets with Laser Peen Forming

    Wu Junfeng

    2018-01-01

    Full Text Available Laser peen forming (LPF is a pure mechanical forming method through accumulated plastic strain, which has been successfully applied in wing components. Experimental investigation has been performed to understand the effect of process parameters such as constraint conditions, sheet thickness and laser energy on surface morphology and bending deformation of 2024-T3 thin sheets of dimensions of 76 mm ×19 mm (length × width. The research results indicated that bulges on the aluminum foil were generated at the bottom surface and not generated at the topmost surface. It was different for transition value of two-way bending deformations of thin sheets after LPF with different constraint conditions. Remain flat thicknesses of thin sheets after LPF were about 1 mm ~ 2 mm for 20 J, 25 J and 30 J. Arc heights and curvatures of 3 mm thickness sheets increased with laser energy and those of 2 mm thickness sheets only made little change. It was found that convex deformation, flat, concave deformation and laser deep drawing for thin sheets with different thicknesses after LPF.

  16. Elaboration of the technology of forming a conical product of sheet metal

    W. Matysiak

    2010-01-01

    Full Text Available The work presents a general knowledge about spinning draw pieces of sheets, one of multi-operational processes of spinning a sheet metal conical product without machining. The objective of the work was to elaborate both the technology of forming conical products of sheet metal and execution of technological tests as well as to determine the technological parameters for the process of spinning a conical insert. As a result of the investigations, the products with improved mechanical properties, stricter execution tolerance and low roughness have been obtained. The series of 200 prototype conical inserts for the shipbuilding industry have been made.

  17. Determination of the forming limit diagram of zinc electro-galvanized steel sheets

    W. Fracz

    2012-04-01

    Full Text Available Forming limit curves (FLC of deep drawing steel sheets have been determined experimentally and calculated on the base of the material tensile properties following the Hill, Swift, Marciniak-Kuczyński and Sing-Rao methods. Only the FLC modeled from a singly linear forming limit stress curve exhibits good consistence with experimental curve. It was established that a linearized limit stress locus describes adequately the actual localized neck conditions for the material chosen in this study. The quantitative X-ray microanalysis of the Fe contents in the sheet surface layer composition was used to determine cracking limit curve (CLC of electro-galvanized steel sheet. The change in zinc layer (and base sheet metal thickness was used as a criteria in calculation of the CLC.

  18. Numerical simulation for the magnetic force distribution in electromagnetic forming of small size flat sheet

    Chen, Xiaowei; Wang, Wenping; Wan, Min

    2013-12-01

    It is essential to calculate magnetic force in the process of studying electromagnetic flat sheet forming. Calculating magnetic force is the basis of analyzing the sheet deformation and optimizing technical parameters. Magnetic force distribution on the sheet can be obtained by numerical simulation of electromagnetic field. In contrast to other computing methods, the method of numerical simulation has some significant advantages, such as higher calculation accuracy, easier using and other advantages. In this paper, in order to study of magnetic force distribution on the small size flat sheet in electromagnetic forming when flat round spiral coil, flat rectangular spiral coil and uniform pressure coil are adopted, the 3D finite element models are established by software ANSYS/EMAG. The magnetic force distribution on the sheet are analyzed when the plane geometries of sheet are equal or less than the coil geometries under fixed discharge impulse. The results showed that when the physical dimensions of sheet are less than the corresponding dimensions of the coil, the variation of induced current channel width on the sheet will cause induced current crowding effect that seriously influence the magnetic force distribution, and the degree of inhomogeneity of magnetic force distribution is increase nearly linearly with the variation of induced current channel width; the small size uniform pressure coil will produce approximately uniform magnetic force distribution on the sheet, but the coil is easy to early failure; the desirable magnetic force distribution can be achieved when the unilateral placed flat rectangular spiral coil is adopted, and this program can be take as preferred one, because the longevity of flat rectangular spiral coil is longer than the working life of small size uniform pressure coil.

  19. Improvement of Weldment Properties by Hot Forming Quenching of Friction Stir Welded TWB Sheet

    Dae-Hoon Ko

    2014-04-01

    Full Text Available The purpose of this study is to improve the mechanical properties and formability of friction stir welded tailor-welded blanks (TWBs of Al6061 alloy with a new forming method called hot forming quenching (HFQ in which solid-solution heat-treated aluminum sheets are formed at elevated temperature. Forming and quenching during HFQ are simultaneously performed with the forming die for the solid-solution heat-treated sheet. In this study, specimens of aluminum TWBs were prepared by friction stir welding (FSW with a butt joint. The effectiveness of FSW joining was evaluated by observation of the macrostructure for different sheet thicknesses. In order to evaluate the formability of TWBs by HFQ, a hemisphere dome stretching test of the limit dome height achieved without specimen failure was performed with various tool temperatures. A Vickers test was also performed to measure weldment hardness as a function of position. The formability and mechanical properties of products formed by HFQ are compared with those formed by conventional forming methods, demonstrating the suitability of HFQ for sheet metal forming of friction stir welded TWBs.

  20. Superplastic Forming/Adhesive Bonding of Aluminum (SPF/AB) Multi-Sheet Structures

    Wagner, John A. (Technical Monitor); Will, Jeff D.; Cotton, James D.

    2003-01-01

    A significant fraction of airframe structure consists of stiffened panels that are costly and difficult to fabricate. This program explored a potentially lower-cost processing route for producing such panels. The alternative process sought to apply concurrent superplastic forming and adhesive bonding of aluminum alloy sheets. Processing conditions were chosen to balance adequate superplasticity of the alloy with thermal stability of the adhesive. As a first objective, an air-quenchable, superplastic aluminum-lithium alloy and a low-volatile content, low-viscosity adhesive with compatible forming/curing cycles were identified. A four-sheet forming pack was assembled which consisted of a welded two-sheet core separated from the face sheets by a layer of adhesive. Despite some preliminary success, of over 30 forming trials none was completely successful. The main problem was inadequate superplasticity in the heat-affected zones of the rib welds, which generally fractured prior to completion of the forming cycle. The welds are a necessary component in producing internal ribs by the 'four-sheet' process. Other challenges, such as surface preparation and adhesive bonding, were adequately solved. But without the larger issue of tearing at the weld locations, complex panel fabrication by SPF/AB does not appear viable.

  1. Investigations of the form and flow of ice sheets and glaciers using radio-echo sounding

    Dowdeswell, J A; Evans, S [Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER (United Kingdom)

    2004-10-01

    Radio-echo sounding (RES), utilizing a variety of radio frequencies, was developed to allow glaciologists to measure the thickness of ice sheets and glaciers. We review the nature of electromagnetic wave propagation in ice and snow, including the permittivity of ice, signal attenuation and volume scattering, along with reflection from rough and specular surfaces. The variety of instruments used in RES of polar ice sheets and temperate glaciers is discussed. The applications and insights that a knowledge of ice thickness, and the wider nature of the form and flow of ice sheets, provides are also considered. The thickest ice measured is 4.7 km in East Antarctica. The morphology of the Antarctic and Greenland ice sheets, and many of the smaller ice caps and glaciers of the polar regions, has been investigated using RES. These findings are being used in three-dimensional numerical models of the response of the cryosphere to environmental change. In addition, the distribution and character of internal and basal reflectors within ice sheets contains information on, for example, ice-sheet layering and its chrono-stratigraphic significance, and has enabled the discovery and investigation of large lakes beneath the Antarctic Ice Sheet. Today, RES from ground-based and airborne platforms remains the most effective tool for measuring ice thickness and internal character.

  2. Effect of material scatter on the plastic behavior and stretchability in sheet metal forming

    Wiebenga, J.H.; Atzema, E.H.; Atzema, E.H.; An, Y.G.; Vegter, H.; van den Boogaard, Antonius H.

    2014-01-01

    Robust design of forming processes is gaining attention throughout the industry. To analyze the robustness of a sheet metal forming process using Finite Element (FE) simulations, an accurate input in terms of parameter scatter is required. This paper presents a pragmatic, accurate and economic

  3. Feasibility Study on Flexibly Reconfigurable Roll Forming Process for Sheet Metal and Its Implementation

    Jun-Seok Yoon

    2014-06-01

    Full Text Available A multicurved sheet metal surface for a skin structure has usually been manufactured using a conventional die forming process involving the use of both a die and a press machine in accordance with the product shape. However, such processes are economically inefficient because additional production costs are incurred for the development and management of forming tools. To overcome this drawback, many alternative processes have been developed; however, these still suffer from problems due to defects such as dimples and wrinkles occurring in the sheet. In this study, a new sheet metal forming process called the flexibly reconfigurable roll forming (FRRF process is proposed as an alternative to existing processes. Unlike existing processes, FRRF can reduce additional production costs resulting from material loss and significantly reduce forming errors. Furthermore, it involves the use of a smaller apparatus. The methodology and applicable procedure of the FRRF process are described. Numerical forming simulations of representative multicurved sheet surfaces are conducted using FEM. In addition, a simple apparatus is developed for verifying the feasibility of this process, and a doubly curved metal is formed to verify the applicability of the reconfigurable roller, a critical component in this forming process.

  4. Damage percolation during stretch flange forming of aluminum alloy sheet

    Chen, Zengtao; Worswick, Michael J.; Keith Pilkey, A.; Lloyd, David J.

    2005-12-01

    A multi-scale finite element (FE)-damage percolation model was employed to simulate stretch flange forming of aluminum alloys AA5182 and AA5754. Material softening and strain gradients were captured using a Gurson-based FE model. FE results were then fed into the so-called damage percolation code, from which the damage development was modelled within measured microstructures. The formability of the stretch flange samples was predicted based upon the onset of catastrophic failure triggered by profuse void coalescence within the measured second-phase particle field. Damage development is quantified in terms of crack and void areal fractions, and compared to metallographic results obtained from interrupted stretch flange specimens. Parametric study is conducted on the effect of void nucleation strain in the prediction of formability of stretch flanges to "calibrate" proper nucleation strains for both alloys.

  5. Manufacture of a four-sheet complex component from different titanium alloys by superplastic forming

    Allazadeh, M. R.; Zuelli, N.

    2017-10-01

    A superplastic forming (SPF) technology process was deployed to form a complex component with eight-pocket from a four-sheet sandwich panel sheetstock. Six sheetstock packs were composed of two core sheets made of Ti-6Al-4V or Ti-5Al-4Cr-4Mo-2Sn-2Zr titanium alloy and two skin sheets made of Ti-6Al-4V or Ti-6Al-2Sn-4Zr-2Mo titanium alloy in three different combinations. The sheets were welded with two subsequent welding patterns over the core and skin sheets to meet the required component's details. The applied welding methods were intermittent and continuous resistance seam welding for bonding the core sheets to each other and the skin sheets over the core panel, respectively. The final component configuration was predicted based on the die drawings and finite element method (FEM) simulations for the sandwich panels. An SPF system set-up with two inlet gas pipe feeding facilitated the trials to deliver two pressure-time load cycles acting simultaneously which were extracted from FEM analysis for specific forming temperature and strain rate. The SPF pressure-time cycles were optimized via GOM scanning and visually inspecting some sections of the packs in order to assess the levels of core panel formation during the inflation process of the sheetstock. Two sets of GOM scan results were compared via GOM software to inspect the surface and internal features of the inflated multisheet packs. The results highlighted the capability of the tested SPF process to form complex components from a flat multisheet pack made of different titanium alloys.

  6. Incremental deformation: A literature review

    Nasulea Daniel

    2017-01-01

    Full Text Available Nowadays the customer requirements are in permanent changing and according with them the tendencies in the modern industry is to implement flexible manufacturing processes. In the last decades, metal forming gained attention of the researchers and considerable changes has occurred. Because for a small number of parts, the conventional metal forming processes are expensive and time-consuming in terms of designing and manufacturing preparation, the manufacturers and researchers became interested in flexible processes. One of the most investigated flexible processes in metal forming is incremental sheet forming (ISF. ISF is an advanced flexible manufacturing process which allows to manufacture complex 3D products without expensive dedicated tools. In most of the cases it is needed for an ISF process the following: a simple tool, a fixing device for sheet metal blank and a universal CNC machine. Using this process it can be manufactured axis-symmetric parts, usually using a CNC lathe but also complex asymmetrical parts using CNC milling machines, robots or dedicated equipment. This paper aim to present the current status of incremental sheet forming technologies in terms of process parameters and their influences, wall thickness distribution, springback effect, formability, surface quality and the current main research directions.

  7. Advanced solid elements for sheet metal forming simulation

    Mataix, Vicente; Rossi, Riccardo; Oñate, Eugenio; Flores, Fernando G.

    2016-08-01

    The solid-shells are an attractive kind of element for the simulation of forming processes, due to the fact that any kind of generic 3D constitutive law can be employed without any additional hypothesis. The present work consists in the improvement of a triangular prism solid-shell originally developed by Flores[2, 3]. The solid-shell can be used in the analysis of thin/thick shell, undergoing large deformations. The element is formulated in total Lagrangian formulation, and employs the neighbour (adjacent) elements to perform a local patch to enrich the displacement field. In the original formulation a modified right Cauchy-Green deformation tensor (C) is obtained; in the present work a modified deformation gradient (F) is obtained, which allows to generalise the methodology and allows to employ the Pull-Back and Push-Forwards operations. The element is based in three modifications: (a) a classical assumed strain approach for transverse shear strains (b) an assumed strain approach for the in-plane components using information from neighbour elements and (c) an averaging of the volumetric strain over the element. The objective is to use this type of elements for the simulation of shells avoiding transverse shear locking, improving the membrane behaviour of the in-plane triangle and to handle quasi-incompressible materials or materials with isochoric plastic flow.

  8. Shape measurement system for single point incremental forming (SPIF) manufacts by using trinocular vision and random pattern

    Setti, Francesco; Bini, Ruggero; Lunardelli, Massimo; Bosetti, Paolo; Bruschi, Stefania; De Cecco, Mariolino

    2012-01-01

    Many contemporary works show the interest of the scientific community in measuring the shape of artefacts made by single point incremental forming. In this paper, we will present an algorithm able to detect feature points with a random pattern, check the compatibility of associations exploiting multi-stereo constraints and reject outliers and perform a 3D reconstruction by dense random patterns. The algorithm is suitable for a real-time application, in fact it needs just three images and a synchronous relatively fast processing. The proposed method has been tested on a simple geometry and results have been compared with a coordinate measurement machine acquisition. (paper)

  9. Quantification of Galling in Sheet Metal Forming by surface topography characterisation

    Andreasen, Jan Lasson; Bay, Niels; De Chiffre, Leonardo

    1998-01-01

    One of the major problems in forming of stainless steel sheet is galling due to lubricant film breakdown leading to scoring and bad surface quality. In a Danish research programme new lubricants substituting the normally applied chlorinated paraffin oils are being developed and tested...... for this purpose. In order to determine the limits of lubrication of these new lubricants, as well as commercial ones already available on the market, two sheet forming tests have been developed. Quantification of the degree of galling is done by roughness measurements on the workpiece surface. In a strip...

  10. Multi Stage Strategies for Single Point Incremental Forming of a Cup

    Skjødt, Martin; Bay, Niels; Endelt, Benny

    2008-01-01

    A five stage forming strategy for forming of a circular cylindrical cup with a height/radius ratio of one is presented. Geometrical relations are discussed and theoretical strains are calculated. The influence of forming direction (upwards or downwards) is investigated for the second stage...... comparing explicit FE analysis with experiments. Good agreement is found between calculated and measured thickness distribution, overall geometry and strains. Using the proposed multi stage strategy it is shown possible to produce a cup with a height close to the radius and side parallel to the symmetry...

  11. Creep age forming of Al-Cu-Li alloy: Application to thick sheet forming of double curvature aircraft panel

    Younes Wael

    2016-01-01

    Full Text Available Creep-age-forming of a thick Al-Cu-Li sheet is studied. An industrial stamping press is used to form a double curvature panel at a reduced scale. This forming, which includes several relaxation steps, is modelled using ABAQUS. A material model describing an elasto-viscoplastic behaviour with anisotropy effect has been identified and implemented in ABAQUS using Fortran subroutine. The numerical model is validated by comparing experiments and numerical results in terms of deformed shapes and an improved forming cycle is suggested.

  12. Development of parallel benchmark code by sheet metal forming simulator 'ITAS'

    Watanabe, Hiroshi; Suzuki, Shintaro; Minami, Kazuo

    1999-03-01

    This report describes the development of parallel benchmark code by sheet metal forming simulator 'ITAS'. ITAS is a nonlinear elasto-plastic analysis program by the finite element method for the purpose of the simulation of sheet metal forming. ITAS adopts the dynamic analysis method that computes displacement of sheet metal at every time unit and utilizes the implicit method with the direct linear equation solver. Therefore the simulator is very robust. However, it requires a lot of computational time and memory capacity. In the development of the parallel benchmark code, we designed the code by MPI programming to reduce the computational time. In numerical experiments on the five kinds of parallel super computers at CCSE JAERI, i.e., SP2, SR2201, SX-4, T94 and VPP300, good performances are observed. The result will be shown to the public through WWW so that the benchmark results may become a guideline of research and development of the parallel program. (author)

  13. Computer controlled experimental device for investigations of tribological influences in sheet metal forming

    Milan Djordjevic

    2012-05-01

    Full Text Available Sheet metal forming, especially deep drawing process, is influenced by many factors. Blank holding force and drawbead displacement are two of them that can be controlled during the forming process. For this purpose, electro-hydraulic computerized sheet-metal strip sliding device has been constructed. Basic characteristic of this device is realization of variable contact pressure and drawbead height as functions of time or stripe displacement. There are both, pressure and drawbead, ten linear and nonlinear functions. Additional features consist of the ability to measure drawing force, contact pressure, drawbead displacement etc. Presented in the paper are the device overview and the first results of steel sheet stripe sliding over rounded  drawbead.

  14. COMPUTER CONTROLLED EXPERIMENTAL DEVICE FOR INVESTIGATIONS OF TRIBOLOGICAL INFLUENCES IN SHEET METAL FORMING

    Tomislav Vujinović

    2012-05-01

    Full Text Available Sheet metal forming, especially deep drawing process is influenced by many factors. Blank holding force and drawbead displacement are two of them that can be controlled during the forming process.For this purpose, an electro-hydraulic computerized sheet-metal strip sliding device has been constructed. The basic characteristic of this device is realization of variable contact pressure and drawbead height as functions of time or stripe displacement. There are both, pressure and drawbead, ten linear and nonlinear functions. Additional features consist of the ability to measure drawing force, contact pressure, drawbead displacement etc.The device overview and first results of steel sheet stripe sliding over rounded drawbead are presented in the paper.

  15. Strain Paths and Fractures in Rotational Symmetric Multi Stage Single Point Incremental Forming

    Skjødt, Martin; Silva, M.B.; Martins, P.A.F.

    2008-01-01

    A multi stage strategy, which allows forming of SPIF parts with vertical walls, is investigated with emphasis on strain paths and fracture strains. Whereas downwards movement of the tool pin results in deformation close to plane strain upwards moving tool results in biaxial strains. A good correl...

  16. Testing and modelling of industrial tribo-systems for sheet metal forming

    Friis, Kasper Leth; Nielsen, Peter Søe; Bay, Niels

    2008-01-01

    Galling is a well-known problem in sheet metal forming of tribological difficult materials such as stainless steel. In this work new, environmentally friendly lubricants and wear resistant tool materials are tested in a laboratory environment using a strip reduction test as well as in a real...

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

    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.

  18. Numerical modelling of microscopic lubricant flow in sheet metal forming. Application to plane strip drawing

    Carretta, Y.; Boman, R.; Bech, Jakob Ilsted

    2017-01-01

    This paper presents a numerical investigation of microscopic lubricant flows from the cavities to the plateaus of the surface roughness of metal sheets during forming processes. This phenomenon, called micro-plasto-hydrodynamic (MPH) lubrication, was observed experimentally in various situations...

  19. EXPERIMENTAL TESTING OF DRAW-BEAD RESTRAINING FORCE IN SHEET METAL FORMING

    J.H. Yang; J. Chen; D.N. He; X. Y. Ruan

    2003-01-01

    Due to complexities of draw-bead restraining force calculated according to theory anddepending on sheet metal forming properties experiment testing system, a simplifiedmethod to calculate draw-bead restraining force is put forward by experimental methodin cup-shaped drawing process. The experimental results were compared with numer-ical results and proved agreement. It shows the method is effective.

  20. Friction modelling in sheet metal forming simulations: application and validation on an U-Bend product

    Sigvant, Mats; Hol, Johan; Chezan, Toni; van den Boogaard, Ton; Hora, P.

    2015-01-01

    The accuracy of sheet metal forming simulations strongly depends on, amongst others, friction modelling. The industrial standard is to use the Coulomb friction model with a constant coefficient of friction. However, it is known that the true friction conditions are dependent on the tribology system,

  1. Improvements in FE-analysis of real-life sheet metal forming

    Huetink, Han; van den Boogaard, Antonius H.; Geijselaers, Hubertus J.M.; Meinders, Vincent T.

    2000-01-01

    An overview will be presented of recent developments concerning the application and development of computer codes for numerical simulation of sheet metal forming processes. In this paper attention is paid to some strategies which are followed to improve the accuracy and to reduce the computation

  2. An advanced material model for aluminum sheet forming at elevated temperatures

    Kurukuri, S.; Miroux, Alexis; Ghosh, Manojit; van den Boogaard, Antonius H.; Oñate, E.; Owen, D.R.J; Suárez, B.

    2009-01-01

    A physically-based material model according to Nes is used to simulate the warm forming of Al-Mg-Si sheet. This model incorporates the influence of the temperature and strain rate on the flow stress and on the hardening rate based on storage and dynamic recovery of dislocations. The effect of size

  3. Increasing the Robustness of the Sheet Metal Forming Simulation by the Prediction of the Forming Limit Band

    Banabic, D.; Vos, M.; Paraianu, L.; Jurco, P.

    2007-05-01

    The experimental research on the formability of metal sheets has shown that there is a significant dispersion of the limit strains in an area delimited by two curves: a lower curve (LFLC) and an upper one (UFLC). The region between the two curves defines the so-called Forming Limit Band (FLB). So far, this forming band has only been determined experimentally. In this paper the authors suggested a method to predict the Forming Limit Band. The proposed method is illustrated on the AA6111-T43 aluminium alloy.

  4. Increasing the Robustness of the Sheet Metal Forming Simulation by the Prediction of the Forming Limit Band

    Banabic, D.; Paraianu, L.; Vos, M.; Jurco, P.

    2007-01-01

    The experimental research on the formability of metal sheets has shown that there is a significant dispersion of the limit strains in an area delimited by two curves: a lower curve (LFLC) and an upper one (UFLC). The region between the two curves defines the so-called Forming Limit Band (FLB). So far, this forming band has only been determined experimentally. In this paper the authors suggested a method to predict the Forming Limit Band. The proposed method is illustrated on the AA6111-T43 aluminium alloy

  5. Strategic surface topographies for enhanced lubrication in sheet forming of stainless steel

    Nilsson, Morten Sixten; Olsson, David Dam; Petrushina, Irina

    2010-01-01

    Strategic stainless steel surfaces have been developed for which the tribological properties are significantly improved for sheet-metal forming compared with the as-received surfaces. The improvements have been achieved by modification of the surface to promote Micro-Plasto Hydrodynamic Lubrication....... The technique, which has been developed, is based on an electrochemical treatment changing the topography of the stainless steel surface. Comparative testing of the new surface topographies in ironing and deep drawing of stainless steel sheet shows significant improvements and possibilities of replacing...

  6. The influence of surface topography on the forming friction of automotive aluminum sheet

    Kramer, Pamela Ann [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

    1998-05-01

    Interest in utilizing aluminum alloys in automobiles has increased in recent years as a result of the desire to lower automobile weight and, consequently, increase fuel economy. While aluminum alloy use in cast parts has increased, outer body panel applications are still being investigated. The industry is interested in improving the formability of these sheet alloys by a combination of alloy design and processing. A different avenue of improving the formability of these alloys may be through patterning of the sheet surface. Surface patterns hold the lubricant during the forming process, with a resulting decrease in the sheet-die surface contact. While it has been speculated that an optimum surface pattern would consist of discrete cavities, detailed investigation into the reduction of forming friction by utilizing discrete patterns is lacking. A series of discrete patterns were investigated to determine the dependence of the forming friction of automotive aluminum alloys on pattern lubricant carrying capacity and on material strength. Automotive aluminum alloys used in outer body panel applications were rolled on experimental rolls that had been prepared with a variety of discrete patterns. All patterns for each alloy were characterized before and after testing both optically and, to determine pattern lubricant capacity, using three dimensional laser profilometry. A draw bead simulation (DBS) friction tester was designed and fabricated to determine the forming friction of the patterned sheets. Tensile testing and frictionless DBS testing were performed to ascertain the material properties of each sheet. The most striking result of this work was the inversely linear dependence of forming friction on the lubricant carrying capacity of the discrete patterns.

  7. Effect of Punch Stroke on Deformation During Sheet Forming Through Finite Element

    Akinlabi, Stephen; Akinlabi, Esther

    2017-08-01

    Forming is one of the traditional methods of making shapes, bends and curvature in metallic components during a fabrication process. Mechanical forming, in particular, employs the use of a punch, which is pressed against the sheet material to be deformed into a die by the application of an external force. This study reports on the finite element analysis of the effects of punch stroke on the resulting sheet deformation, which is directly a function of the structural integrity of the formed components for possible application in the automotive industry. The results show that punch stroke is directly proportional to the resulting bend angle of the formed components. It was further revealed that the developed plastic strain increases as the punch stroke increases.

  8. The Effects of Plastic Anisotropy in Warm and Hot Forming of Magnesium Sheet Materials

    Taleff, Eric M.; Antoniswamy, Aravindha R.; Carpenter, Alexander J.; Yavuz, Emre

    Mg alloy sheet materials often exhibit plastic anisotropy at room temperature as a result of the limited slip systems available in the HCP lattice combined with a commonly strong basal texture. Less well studied is plastic anisotropy developed at the elevated temperatures associated with warm and hot forming. At these elevated temperatures, particularly above 200°C, the activation of additional slip systems significantly increases ductility. However, plastic anisotropy is also induced at elevated temperatures by a strong crystallographic texture, and it can require an accounting in material constitutive models to achieve accurate forming simulations. The type and degree of anisotropy under these conditions depend on both texture and deformation mechanism. The current understanding of plastic anisotropy in Mg AZ31B and ZEK100 sheet materials at elevated temperatures is reviewed in this article. The recent construction of material forming cases is also reviewed with strategies to account for plastic anisotropy in forming simulations.

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

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

    2005-01-01

    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

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

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

    2007-01-01

    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

  11. Non-contact sheet forming using lasers applied to a high strength aluminum alloy

    Rafael Humberto Mota Siqueira

    2016-07-01

    Full Text Available Laser beam forming (LBF is a contactless mechanical process accomplished by the introduction of thermal stresses on the surface of a material using a laser in order to induce plastic deformation. In this work, LBF was performed on 1.6 mm thick sheets of a high strength aluminum alloy, AA6013-T4 class by using a defocused continuous Yb-fiber laser beam of 0.6 mm in diameter on the sheet top surface. The laser power and process speed were varied from 200 W to 2000 W and from 3 to 30 mm/s, respectively. For these experimental conditions, the bending angle of the sheet ranged from 0.1° to 2.5° per run. In the highest bending angle condition, 1000 W and 30 mm/s, the depth of remelted pool was 0.6 mm and the microstructure near the plate bottom surface remained unaltered. For the whole set of experimental conditions, the hardness remained constant at approximately 100 HV, which is similar to the base material. In order to verify the applicability of the method, some previously T-welded sheets were straightened. The method was efficient in correcting the distortion of the sheets with a bending angle up to 5°.

  12. Explicit and implicit springback simulation in sheet metal forming using fully coupled ductile damage and distortional hardening model

    Yetna n'jock, M.; Houssem, B.; Labergere, C.; Saanouni, K.; Zhenming, Y.

    2018-05-01

    The springback is an important phenomenon which accompanies the forming of metallic sheets especially for high strength materials. A quantitative prediction of springback becomes very important for newly developed material with high mechanical characteristics. In this work, a numerical methodology is developed to quantify this undesirable phenomenon. This methodoly is based on the use of both explicit and implicit finite element solvers of Abaqus®. The most important ingredient of this methodology consists on the use of highly predictive mechanical model. A thermodynamically-consistent, non-associative and fully anisotropic elastoplastic constitutive model strongly coupled with isotropic ductile damage and accounting for distortional hardening is then used. An algorithm for local integration of the complete set of the constitutive equations is developed. This algorithm considers the rotated frame formulation (RFF) to ensure the incremental objectivity of the model in the framework of finite strains. This algorithm is implemented in both explicit (Abaqus/Explicit®) and implicit (Abaqus/Standard®) solvers of Abaqus® through the users routine VUMAT and UMAT respectively. The implicit solver of Abaqus® has been used to study spingback as it is generally a quasi-static unloading. In order to compare the methods `efficiency, the explicit method (Dynamic Relaxation Method) proposed by Rayleigh has been also used for springback prediction. The results obtained within U draw/bending benchmark are studied, discussed and compared with experimental results as reference. Finally, the purpose of this work is to evaluate the reliability of different methods predict efficiently springback in sheet metal forming.

  13. Development of tearing instability in a current sheet forming by sheared incompressible flow

    Tolman, Elizabeth A.; Loureiro, Nuno F.; Uzdensky, Dmitri A.

    2018-02-01

    Sweet-Parker current sheets in high Lundquist number plasmas are unstable to tearing, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Formation can occur due to sheared, sub-Alfvénic incompressible flows which narrow the sheet. Standard tearing theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Rutherford, Phys. Fluids, vol. 16 (11), 1973, pp. 1903-1908, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) is not immediately applicable to such forming sheets for two reasons: first, because the flow introduces terms not present in the standard calculation; second, because the changing equilibrium introduces time dependence to terms which are constant in the standard calculation, complicating the formulation of an eigenvalue problem. This paper adapts standard tearing mode analysis to confront these challenges. In an initial phase when any perturbations are primarily governed by ideal magnetohydrodynamics, a coordinate transformation reveals that the flow compresses and stretches perturbations. A multiple scale formulation describes how linear tearing mode theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) can be applied to an equilibrium changing under flow, showing that the flow affects the separable exponential growth only implicitly, by making the standard scalings time dependent. In the nonlinear Rutherford stage, the coordinate transformation shows that standard theory can be adapted by adding to the stationary rates time dependence and an additional term due to the strengthening equilibrium magnetic field. Overall, this understanding supports the use of flow-free scalings with slight modifications to study tearing in a forming sheet.

  14. Local laser-strengthening: Customizing the forming behavior of car body steel sheets

    Wagner, M.; Jahn, A.; Beyer, E.; Balzani, D.

    2018-05-01

    Future trends in designing lightweight components especially for automotive applications increasingly require complex and delicate structures with highest possible level of capacity [1]. The manufacturing of metallic car body components is primarily realized by deep or stretch drawing. The forming process of especially cold rolled and large-sized components is typically characterized by inhomogeneous stress and strain distributions. As a result, the avoidance of undesirable deep drawing effects like earing and local necking is among the greatest challenges in forming complex car body structures [2]. Hence, a novel local laser-treatment approach with the objective of customizing the forming behavior of car body steel sheets is currently explored.

  15. Springback prediction in sheet metal forming process based on the hybrid SA

    Guo Yuqin; Jiang Hong; Wang Xiaochun; Li Fuzhu

    2005-01-01

    In terms of the intensive similarity between the sheet metal forming-springback process and that of the annealing of metals, it is suggested that the simulation of the sheet metal forming process is performed with the Nonlinear FEM and the springback prediction is implemented by solving the large-scale combinational optimum problem established on the base of the energy descending and balancing in deformed part. The BFGS-SA hybrid SA approach is proposed to solve this problem and improve the computing efficiency of the traditional SA and its capability of obtaining the global optimum solution. At the same time, the correlative annealing strategies for the SA algorithm are determined in here. By comparing the calculation results of sample part with those of experiment measurement at the specified sections, the rationality of the schedule of springback prediction used and the validity of the BFGS-SA algorithm proposed are verified

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

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

    2007-01-01

    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. The prediction of necking and failure in 3 D. Sheet forming analysis using damage variable

    Brunet, M.; Sabourin, F.; Mguil-Touchal, S.

    1996-01-01

    The modeling of necking occurrence in sheet metal forming is a real challenge for the engineer concerned with processing of new geometries and materials. As fracture in metal forming is mainly due to the development of ductile damage and to represent the failure of anisotropic sheet-metals, an extension of the Gurson-Tvergaard model is presented and implemented in the context of plane-stress for shell elements. A one dimensional problem is solved and compared with the exact solution of the literature. The paper closes with a numerical and experimental study of the necking of a square cup deep-drawing using the modified Gurson's model to described the constitutive behavior of the material. Finally, a numerical necking criterion is proposed. (orig.)

  18. The prediction of necking and failure in 3 D. Sheet forming analysis using damage variable

    Brunet, M. [INSA, Villeurbanne (France). Lab. de Mecanique des Solides; Sabourin, F. [INSA, Villeurbanne (France). Lab. de Mecanique des Solides; Mguil-Touchal, S. [INSA, Villeurbanne (France). Lab. de Mecanique des Solides

    1996-10-01

    The modeling of necking occurrence in sheet metal forming is a real challenge for the engineer concerned with processing of new geometries and materials. As fracture in metal forming is mainly due to the development of ductile damage and to represent the failure of anisotropic sheet-metals, an extension of the Gurson-Tvergaard model is presented and implemented in the context of plane-stress for shell elements. A one dimensional problem is solved and compared with the exact solution of the literature. The paper closes with a numerical and experimental study of the necking of a square cup deep-drawing using the modified Gurson`s model to described the constitutive behavior of the material. Finally, a numerical necking criterion is proposed. (orig.).

  19. Testing and modelling of new tribo-systems for industrial sheet forming of stainless steels

    Nielsen, Peter Søe; Friis, Kasper Storgaard; Bay, Niels

    2011-01-01

    Sheet metal forming of stainless steels is known to be tribologically demanding. To ensure satisfactory production without pick-up and galling, lubrication with environmentally hazardous chlorinated paraffin oil is normally required and in the most severe cases combined with ceramic tool coatings...... as well as the production test in order to estimate the critical interface temperature for lubricant film breakdown. Simulation results show good agreement with experimental measurements of tool temperature close to the interface....

  20. EXPERIMENTAL TESTING OF DRAW—BEAD RESTRAINING FORCE IN SHEET METAL FORMING

    J.H.Yang; J.Chen; 等

    2003-01-01

    Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system,a simplified method to calculate draw-bead restraining force is put forward by experimental method in cup-shaped drawing process.The experimental results were compared with numer-ical results and proved agreement.It shows the method is effective.

  1. Prediction of forming limit in hydro-mechanical deep drawing of steel sheets using ductile fracture criterion

    Oh, S.-T.; Chang, H.-J.; Oh, K. H.; Han, H. N.

    2006-04-01

    It has been observed that the forming limit curve at fracture (FLCF) of steel sheets, with a relatively higher ductility limit have linear shapes, similar to those of a bulk forming process. In contrast, the FLCF of sheets with a relatively lower ductility limit have rather complex shapes approaching the forming limit curve at neck (FLCN) towards the equi-biaxial strain paths. In this study, the FLCFs of steel sheets were measured and compared with the fracture strains predicted from specific ductile fracture criteria, including a criterion suggested by the authors, which can accurately describe FLCFs with both linear and complex shapes. To predict the forming limit for hydro-mechanical deep drawing of steel sheets, the ductile fracture criteria were integrated into a finite element simulation. The simulation, results based on the criterion suggested by authors accurately predicted the experimetal, fracture limits of steel sheets for the hydro-mechanical deep drawing process.

  2. Experimental and FE simulation validation of sheet thickness optimization in superplastic forming of Al alloy

    Kumaresan, G.; Jothilingam, A. [Anna University, Chennai (India)

    2016-07-15

    Superplasticity is the ability of a polycrystalline materials to exhibit very large elongations without necking prior to failure. In this paper, the superplastic forming potential of fine grained 7075 aluminium alloy was studied. The process parameters like pressure, forming time and initial sheet thickness were selected, using the design of experiments technique. The same condition of formation process was attempted in the finite element simulation using ABAQUS software. The deviation of the thickness distribution between the simulation and experiment was made and the variation lies within 8%.

  3. Constitutive modeling for analysis and design of aluminum sheet forming processes

    Barlat, F.; Chung, K.; Yoon, J-W.; Choi, S-H.

    2000-01-01

    Finite element modeling (FEM) technology is one of the most powerful tools used to design new products, i.e. appliances, automotive, rigid packaging and aerospace parts, etc., and processes. However, FEM users need data and models to characterize the materials used to fabricate the new products. In fact, they need more information than the traditional and standard yield strength, ultimate strength, elongation, etc. Constitutive models and their associated coefficients represent a new way to describe material properties, a way that can be used by FEM users. In order to help manufacturers use more aluminum alloy sheet in their products, appropriate material models are needed to analyze and design specifically for these materials. This work describes a methodology that provides phenomenological constitutive equations based on three main microstructure components of aluminum alloys: dislocation density, second-phase particles and crystallographic texture. Examples of constitutive equations and their applications to numerical sheet forming process analysis and design are provided in this work. (author)

  4. The role of textures in the forming of automotive sheet steels

    Sanak Mishra

    1996-01-01

    Crystallographic textures generally have a strong bearing on the drawability of sheet steels. Particularly in the case of automotive sheets, texture control is of paramount importance. In the last two decades, therefore, texture research has assumed much significance in the steel industry. X-ray diffraction continues to remain the most used tool for the study of textures. Early researches, from about 1940 to 1980, were invariably carried out by the pole figure method. However, for more quantitative results the ODF (Orientation Distribution Functions) analysis technique was developed. Since 1980, the ODF analysis has come to be used extensively. In the present paper, several unique features of textures in automotive grade deep drawing steels, as revealed from X-ray ODFS, will be presented. The relative importance of the various textural components with respect to forming will also be dealt with

  5. Investigation of fatigue strength of tool steels in sheet-bulk metal forming

    Pilz, F.; Gröbel, D.; Merklein, M.

    2018-05-01

    To encounter trends regarding an efficient production of complex functional components in forming technology, the process class of sheet-bulk metal forming (SBMF) can be applied. SBMF is characterized by the application of bulk forming operations on sheet metal, often in combination with sheet forming operations [1]. The combination of these conventional process classes leads to locally varying load conditions. The resulting load conditions cause high tool loads, which lead to a reduced tool life, and an uncontrolled material flow. Several studies have shown that locally modified tool surfaces, so-called tailored surfaces, have the potential to control the material flow and thus to increase the die filling of functional elements [2]. A combination of these modified tool surfaces and high tool loads in SBMF is furthermore critical for the tool life and leads to fatigue. Tool fatigue is hardly predictable and due to a lack of data [3], a challenge in tool design. Thus, it is necessary to provide such data for tool steels used in SBMF. The aim of this study is the investigation of the influence of tailored surfaces on the fatigue strength of the powder metallurgical tool steel ASP2023 (1.3344, AISI M3:2), which is typically used in cold forging applications, with a hardness 60 HRC ± 1 HRC. To conduct this investigation, the rotating bending test is chosen. As tailored surfaces, a DLC-coating and a surface manufactured by a high-feed-milling process are chosen. As reference a polished surface which is typical for cold forging tools is used. Before the rotating bending test, the surface integrity is characterized by measuring topography and residual stresses. After testing, the determined values of the surface integrity are correlated with the reached fracture load cycle to derive functional relations. Based on the gained results the investigated tailored surfaces are evaluated regarding their feasibility to modify tool surfaces within SBMF.

  6. Tribological study in roll forming of lean duplex stainless steel sheets

    Nielsen, Peter Søe; Nielsen, Morten Strogaard; Bay, Niels

    2012-01-01

    . Production tests show that galling can be a problem but pick-up formation on the tools seems to reach a consistent level. Improvements to tool surfaces and lubricant quality are proposed with a view to optimizing the tribo-system in order to increase the produced length before galling initiates and tool...... are relatively low and surface expansion is more or less non-existent, long roll forming production runs imply large sliding/contact lengths due to relative movement between steel strip and rolls. This requires an efficient tribological system to prevent pick-up formation on the forming tools. The present work...... focus on tribological issues are galling and pick-up formation as well as tool life in roll forming of stainless duplex steel sheets. The roll forming process is exemplified by production of an s-shaped profile used in interlock carcass production for flexible pipes used in off-shore oil extraction...

  7. A ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum sheet in thermal forming

    Wang Chu

    2015-01-01

    Full Text Available Formability of pure molybdenum in thermal forming process has been greatly improved, but it is still hard to avoid the generation of rupture and other quality defects. In this paper, a ductile fracture criterion of pure molybdenum sheet in thermal forming was established by considering the plastic deformation capacity of material and stress states, which can be used to describe fracture behaviour and critical rupture prediction of pure molybdenum sheet during hot forming process. Based on the isothermal uniaxial tensile tests which performed at 993 to 1143 K with strain rate range from 0.0005 to 0.2 s−1, the material parameters are calculated by the combination method of experiment with FEsimulation. Based on the observation, new fracture criteria can be expressed as a function of Zener-Hollomon parameter. The critical fracture value that calculated by Oyane-Sato criterion increases with increasing temperature and decreasing strain rate. The ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum in thermal forming is proposed.

  8. A new constitutive model for prediction of springback in sheet metal forming

    Appiah, E.; Jain, M.

    2004-01-01

    With advances in computer capabilities, cost of sheet metal forming has being reducing mainly due to the reduction of trial and error approaches. At the moment, a complete process can be simulated on computer and appropriate forming conditions optimized before actual industrial forming process is carried out. While formability predictions have improved, the problem of springback exhibited by most metal, including aluminum alloy AA6111-T4, after forming persist and often leads to significant part fit-up problems during assembly. There are a number of factors that affect springback and perhaps the most significant one is constitutive equation. In this paper springback predicted by six advanced kinematic models are evaluated. In addition an improved constitutive kinematic model is presented. It is shown that by adding stress correction term (SCT) to Armstrong-Frederick model a relatively simple and yet accurate stress prediction could be obtained. The SCT was developed with the assumption that the yield surface remains convex, yield center depends on translation, size and shape variations of the yield surface. The model is implemented in a commercial finite element code (ABAQUS/Standard) via its user material interface (UMAT). Numerical simulations of U-bending were performed using automotive aluminum sheet material (AA6111-T4). It was noted that springback has inverse relationship with residual stress

  9. Off-Line Testing of Tribo-Systems for Sheet Metal Forming Production

    Bay, Niels; Ceron, Ermanno

    2014-01-01

    Off-line testing of new tribo-systems for sheet metal forming production is an important issue, when new, environmentally benign lubricants are to be introduced. To obtain useful results it is, however, vital to ensure similar conditions as in the production process regarding the main tribo...... leading to very high tool/workpiece interface pressure and temperature in the second re-draw. Under such conditions only the best lubricant systems work satisfactory, and the paper shows how the performance of different tribo-systems in production may be predicted by off-line testing combined...

  10. Forming limit diagrams for anisotropic metal sheets with different yield criteria

    Kuroda, M.; Tvergaard, Viggo

    2000-01-01

    For thin metal sheets subject to stretching under various in-plane tensile stress histories, localized necking is analyzed by using the M-K-model approach, and forming limit diagrams are drawn based on the critical strains for localization. The analyses account for plastic anisotropy......, and predictions are shown based on four different anisotropic plasticity models, which have all been fitted to agree with the same set of experimental data. Situations where the tensile axis is along one of the orthotropic axes of the anisotropy are studied, as well as situations where the tensile axis...

  11. Tooling solutions for sheet metal forming and punching of lean duplex stainless steel

    Wadman, Boel; Madsen, Erik; Bay, Niels

    2012-01-01

    .4509 and lean duplex EN1.4162 in a production designed for austenitic stainless steels, such as EN1.4301 and 1.4401. The result is a guideline that summarizes how stainless material properties may affect tool degradation, and suggests tool solutions for reduced production disturbances and tool maintenance cost.......For producers of advanced stainless components the choice of stainless material influences not only the product properties, but also the tooling solution for sheet metal stamping. This work describes how forming and punching tools will be affected when introducing the stainless alloys ferritic EN1...

  12. Microstructures, Forming Limit and Failure Analyses of Inconel 718 Sheets for Fabrication of Aerospace Components

    Sajun Prasad, K.; Panda, Sushanta Kumar; Kar, Sujoy Kumar; Sen, Mainak; Murty, S. V. S. Naryana; Sharma, Sharad Chandra

    2017-04-01

    Recently, aerospace industries have shown increasing interest in forming limits of Inconel 718 sheet metals, which can be utilised in designing tools and selection of process parameters for successful fabrication of components. In the present work, stress-strain response with failure strains was evaluated by uniaxial tensile tests in different orientations, and two-stage work-hardening behavior was observed. In spite of highly preferred texture, tensile properties showed minor variations in different orientations due to the random distribution of nanoprecipitates. The forming limit strains were evaluated by deforming specimens in seven different strain paths using limiting dome height (LDH) test facility. Mostly, the specimens failed without prior indication of localized necking. Thus, fracture forming limit diagram (FFLD) was evaluated, and bending correction was imposed due to the use of sub-size hemispherical punch. The failure strains of FFLD were converted into major-minor stress space ( σ-FFLD) and effective plastic strain-stress triaxiality space ( ηEPS-FFLD) as failure criteria to avoid the strain path dependence. Moreover, FE model was developed, and the LDH, strain distribution and failure location were predicted successfully using above-mentioned failure criteria with two stages of work hardening. Fractographs were correlated with the fracture behavior and formability of sheet metal.

  13. Coarsening of AA6013-T6 Precipitates During Sheet Warm Forming Applications

    Di Ciano, M.; DiCecco, S.; Esmaeili, S.; Wells, M. A.; Worswick, M. J.

    2018-03-01

    The use of warm forming for AA6xxx-T6 sheet is of interest to improve its formability; however, the effect warm forming may have on the coarsening of precipitates and the mechanical strength of these sheets has not been well studied. In this research, the coarsening behavior of AA6013-T6 precipitates has been explored, in the temperature range of 200-300 °C, and time of 30 s up to 50 h. Additionally, the effect of warm deformation on coarsening behavior was explored using: (1) simulated warm forming tests in a Gleeble thermo-mechanical simulator and (2) bi-axial warm deformation tests. Using a strong obstacle model to describe the yield strength (YS) evolution of the AA6013-T6 material, and a Lifshitz, Slyozov, and Wagner (LSW) particle coarsening law to describe the change in precipitate size with time, the coarsening kinetics were modeled for this alloy. The coarsening kinetics in the range of 220-300 °C followed a trend similar to that previously found for AA6111 for the 180-220 °C range. There was strong evidence that coarsening kinetics were not altered due to warm deformation above 220 °C. For warm forming between 200 and 220 °C, the YS of the AA6013-T6 material increased slightly, which could be attributed to strain hardening during warm deformation. Finally, a non-isothermal coarsening model was used to assess the potential reduction in the YS of AA6013-T6 for practical processing conditions related to auto-body manufacturing. The model calculations showed that 90% of the original AA6013-T6 YS could be maintained, for warm forming temperatures up to 280 °C, if the heating schedule used to get the part to the warm forming temperature was limited to 1 min.

  14. Process for forming thin film, heat treatment process of thin film sheet, and heat treatment apparatus therefor

    Watanabe, S.

    1984-01-01

    The invention provides a process for forming a magnetic thin film on a base film, a heat treatment process of a thin film sheet consisting of the base film and the magnetic thin film, and an apparatus for performing heat treatment of the thin film sheet. Tension applied to the thin film sheet is substantially equal to that applied to the base film when the magnetic thin film is formed thereon. Then, the thin film sheet is treated with heat. The thin film sheet is heated with a given temperature gradient to a reactive temperature at which heat shrinkage occurs, while the tension is being applied thereto. Thereafter, the thin film sheet to which the tension is still applied is cooled with substantially the same temperature gradient as applied in heating. The heat treatment apparatus has a film driving unit including a supply reel, a take-up reel, a drive source and guide rollers; a heating unit including heating plates, heater blocks and a temperature controller for heating the sheet to the reactive temperature; and a heat insulating unit including a thermostat and another temperature controller for maintaining the sheet at the nonreactive temperature which is slightly lower than the reactive temperature

  15. Fabrication of corneal epithelial cell sheets maintaining colony-forming cells without feeder cells by oxygen-controlled method.

    Nakajima, Ryota; Takeda, Shizu

    2014-01-01

    The use of murine 3T3 feeder cells needs to be avoided when fabricating corneal epithelial cell sheets for use in treating ocular surface diseases. However, the expression level of the epithelial stem/progenitor cell marker, p63, is down-regulated in feeder-free culture systems. In this study, in order to fabricate corneal epithelial cell sheets that maintain colony-forming cells without using any feeder cells, we investigated the use of an oxygen-controlled method that was developed previously to fabricate cell sheets efficiently. Rabbit limbal epithelial cells were cultured under hypoxia (1-10% O2) and under normoxia during stratification after reaching confluence. Multilayered corneal epithelial cell sheets were fabricated using an oxygen-controlled method, and immunofluorescence analysis showed that cytokeratin 3 and p63 was expressed in appropriate localization in the cell sheets. The colony-forming efficiency of the cell sheets fabricated by the oxygen-controlled method without feeder cells was significantly higher than that of cell sheets fabricated under 20% O2 without feeder cells. These results indicate that the oxygen-controlled method has the potential to achieve a feeder-free culture system for fabricating corneal epithelial cell sheets for corneal regeneration. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Some recent developments in sheet metal forming for production of lightweight automotive parts

    Tisza, M.; Lukács, Zs; Kovács, P.; Budai, D.

    2017-09-01

    Low cost manufacturing in the automotive industry is one of the main targets due to the ever increasing global competition among car manufacturers all over the World. Sheet metal forming is one of the most important key technologies in the automotive industry; therefore the elaboration of new, innovative low cost manufacturing processes is one of the main objectives in sheet metal forming as well. In 2015 with the initiative of the Imperial College London a research consortium was established under the umbrella Low Cost Materials Processing Technologies for Mass Production of Lightweight Vehicles. The primary aim of this project is to provide affordable low cost weight reduction in mass production of vehicles considering the entire life-cycle. In this project, 19 European Institutions (Universities and Research Institutions) from 9 European countries are participating with the above targets. The University of Miskolc is one of the members of this research Consortium. In this paper, some preliminary results with the contributions of the University of Miskolc will be introduced.

  17. Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets

    Vallellano, C.; Guzman, C.; Garcia-Lomas, F. J.

    2007-01-01

    A number of ductile failure criteria are nowadays being used to predict the formability of aluminium alloy sheets. Generally speaking, integral criteria (e.g. those proposed by Cockcroft and Latham, Brozzo et al., Oyane et al Chaouadi et al., etc.) have been probed to work well when the principal strains are of opposite sign, i.e. in the left side of the Forming Limit Diagram (FLD). However, when tensile biaxial strains are present, as occurs in stretch-forming practice, their predictions are usually very poor and even non-conservatives. As an alternative, local criteria, such as the classical Tresca's and Bressan and Williams' criteria, have demonstrated a good capability to predict the failure in some automotive aluminum alloys under stretching. The present work analyses experimentally and numerically the failure in AA2024-T3 sheets subjected to biaxial stretching. A series of out-of-plane stretching tests have been simulated using ABAQUS. The experimental and the numerical FLD for different failure criteria are compared. The influence on the failure of the hydrostatic pressure and the normal stress to the fracture plane is also discussed

  18. Research on Liquid Forming Process of Nickel Superalloys Thin Sheet Metals

    Hyrcza-Michalska M.

    2017-12-01

    Full Text Available The paper presents the study of drawability of thin sheet metals made of a nickel superalloy Inconel type. The manufacturing process of axisymmetric cup – cone and a closed section profile in the form of a circular tube were designed and analyzed. In both cases, working fluid-oil was used in place of the rigid tools. The process of forming liquid is currently the only alternative method for obtaining complex shapes, coatings, and especially if we do it with high-strength materials. In the case of nickel superalloys the search for efficient methods to manufacture of the shaped shell is one of the most considerable problems in aircraft industry [1-5]. However, the automotive industries have the same problem with so-called advanced high-strength steels (AHSS. Due to this, both industrial problems have been examined and the emphasis have been put on the process of liquid forming (hydroforming. The study includes physical tests and the corresponding numerical simulations performed, using the software Eta/Dynaform 5.9. Numerical analysis of the qualitative and quantitative forecasting enables the formability of materials with complex and unusual characteristics of the mechanical properties and forming technology. It has been found that only the computer aided design based on physical and numerical modeling, makes efficient plastic processing possible using a method of hydroforming. Drawability evaluation based on the determination of the mechanical properties of complex characteristics is an indispensable element of this design in the best practice of industrial manufacturing products made of thin sheet metals.

  19. Theories, Methods and Numerical Technology of Sheet Metal Cold and Hot Forming Analysis, Simulation and Engineering Applications

    Hu, Ping; Liu, Li-zhong; Zhu, Yi-guo

    2013-01-01

    Over the last 15 years, the application of innovative steel concepts in the automotive industry has increased steadily. Numerical simulation technology of hot forming of high-strength steel allows engineers to modify the formability of hot forming steel metals and to optimize die design schemes. Theories, Methods and Numerical Technology of Sheet Metal Cold and Hot Forming focuses on hot and cold forming theories, numerical methods, relative simulation and experiment techniques for high-strength steel forming and die design in the automobile industry. Theories, Methods and Numerical Technology of Sheet Metal Cold and Hot Forming introduces the general theories of cold forming, then expands upon advanced hot forming theories and simulation methods, including: • the forming process, • constitutive equations, • hot boundary constraint treatment, and • hot forming equipment and experiments. Various calculation methods of cold and hot forming, based on the authors’ experience in commercial CAE software f...

  20. Oscillations Excited by Plasmoids Formed During Magnetic Reconnection in a Vertical Gravitationally Stratified Current Sheet

    Jelínek, P.; Karlický, M.; Van Doorsselaere, T.; Bárta, M.

    2017-10-01

    Using the FLASH code, which solves the full set of the 2D non-ideal (resistive) time-dependent magnetohydrodynamic (MHD) equations, we study processes during the magnetic reconnection in a vertical gravitationally stratified current sheet. We show that during these processes, which correspond to processes in solar flares, plasmoids are formed due to the tearing mode instability of the current sheet. These plasmoids move upward or downward along the vertical current sheet and some of them merge into larger plasmoids. We study the density and temperature structure of these plasmoids and their time evolution in detail. We found that during the merging of two plasmoids, the resulting larger plasmoid starts to oscillate with a period largely determined by L/{c}{{A}}, where L is the size of the plasmoid and c A is the Alfvén speed in the lateral parts of the plasmoid. In our model, L/{c}{{A}} evaluates to ˜ 25 {{s}}. Furthermore, the plasmoid moving downward merges with the underlying flare arcade, which causes oscillations of the arcade. In our model, the period of this arcade oscillation is ˜ 35 {{s}}, which also corresponds to L/{c}{{A}}, but here L means the length of the loop and c A is the average Alfvén speed in the loop. We also show that the merging process of the plasmoid with the flare arcade is a complex process as presented by complex density and temperature structures of the oscillating arcade. Moreover, all these processes are associated with magnetoacoustic waves produced by the motion and merging of plasmoids.

  1. Model Identification and FE Simulations: Effect of Different Yield Loci and Hardening Laws in Sheet Forming

    Flores, P.; Duchêne, L.; Lelotte, T.; Bouffioux, C.; El Houdaigui, F.; Van Bael, A.; He, S.; Duflou, J.; Habraken, A. M.

    2005-08-01

    The bi-axial experimental equipment developed by Flores enables to perform Baushinger shear tests and successive or simultaneous simple shear tests and plane-strain tests. Such experiments and classical tensile tests investigate the material behavior in order to identify the yield locus and the hardening models. With tests performed on two steel grades, the methods applied to identify classical yield surfaces such as Hill or Hosford ones as well as isotropic Swift type hardening or kinematic Armstrong-Frederick hardening models are explained. Comparison with the Taylor-Bishop-Hill yield locus is also provided. The effect of both yield locus and hardening model choice will be presented for two applications: Single Point Incremental Forming (SPIF) and a cup deep drawing.

  2. Model Identification and FE Simulations: Effect of Different Yield Loci and Hardening Laws in Sheet Forming

    Flores, P.; Lelotte, T.; Bouffioux, C.; El Houdaigui, F.; Habraken, A.M.; Duchene, L.; Bael, A. van; He, S.; Duflou, J.

    2005-01-01

    The bi-axial experimental equipment developed by Flores enables to perform Baushinger shear tests and successive or simultaneous simple shear tests and plane-strain tests. Such experiments and classical tensile tests investigate the material behavior in order to identify the yield locus and the hardening models. With tests performed on two steel grades, the methods applied to identify classical yield surfaces such as Hill or Hosford ones as well as isotropic Swift type hardening or kinematic Armstrong-Frederick hardening models are explained. Comparison with the Taylor-Bishop-Hill yield locus is also provided. The effect of both yield locus and hardening model choice will be presented for two applications: Single Point Incremental Forming (SPIF) and a cup deep drawing

  3. Forming characteristics of artificial aging Al-Mg-Si-Cu sheet alloys

    Klos, Artur; Kellner, Sven; Wortberg, Daniel; Walter, Philipp; Bassi, Corrado; Merklein, Marion

    2017-10-01

    AA6111 is a commonly used aluminum alloy for body-in-white (BIW) components with good bake-hardening response, high strength and excellent formability. For industrial applications various process strategies are considered to reach strength of about 250 MPa in the final body part with that type of alloy. The purpose of this paper is to discuss recent process strategies of high-strength AA6111 sheets to evaluate the forming characteristics, precipitation kinetics dissolution and mechanical properties in the final condition. The forming behavior is investigated by four potential process chains after single-stage or multi-stage heat treatment including T4 (pre-aged at > 80 °C after quenching), T61 (T4 + artificial aged at 120-150 °C for 10-18 h), T6 (T4 + artificial aged at 180-220°C up to 12 h) and PFHT (T4 + post form heat treatment at 205°C for 30 min). The experimental input for characterization of the formability consists of tensile tests, bending tests and drawing tests. Differential Scanning Calorimetry (DSC) is used, to correlate the forming behavior with the precipitation distribution in the advanced stages of aging. The study shows that the forming behavior is strongly dependent on the condition the alloy.

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

    Umezu, Yasuyoshi; Watanabe, Yuko; Ma, Ninshu

    2005-01-01

    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

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

    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.

  6. Effect of Bottoming on Material Property during Sheet Forming Process through Finite Element Method

    Akinlabi, Stephen A.; Fatoba, Olawale S.; Mashinini, Peter M.; Akinlabi, Esther T.

    2018-03-01

    Metal forming is one of the conventional manufacturing processes of immense relevance till date even though modern manufacturing processes have evolved over the years. It is a known fact that material tends to return or spring back to its original form during forming or bending. The phenomena have been well managed through its application in various manufacturing processes by compensating for the spring back through overbending and bottoming. Overbending is bending the material beyond the desired shape to allow the material to spring back to the expected shape. Bottoming, on the other hand, is a process of undergoing plastic deformation at the point of bending. This study reports on the finite element analysis of the effect of bottoming on the material property during the sheet forming process with the aim of optimising the process. The result of the analysis revealed that the generated plastic strains are in the order between 1.750e00-1 at the peak of the bending and 3.604e00-2, which was at the early stage of the bending.

  7. Testing and Prediction of Limits of Lubrication in Sheet Metal Forming

    Ceron, Ermanno; Bay, Niels

    2012-01-01

    Increasing focus on environmental issues in industrial production has urged a number of sheet metal forming companies to look for new tribo-systems, here meaning the combination of tool_material/workpiece_material/lubricant, in order to substitute hazardous lubricants such as chlorinated paraffin...... laboratory and production tests as well as numerical analyses in order to evaluate and compare performance of the new tribo-systems. A part is selected from industrial production and analyzed by this methodology in order to substitute the existing tribo-system with a new one....... oils. Testing of new tribo-systems under production conditions is, however, very costly. For preliminary testing it is more feasible to introduce laboratory tests. In this paper a new methodology for testing new tribo-systems is presented. The methodology describes a series of investigations combining...

  8. Superplastic forming of 7475 Al sheet after friction stir processing (FSP)

    Mahoney, M.; Bingel, W.H.; Fuller, C. [Rockwell Scientific Co., Thousand Oaks, CA (United States); Barnes, A.J. [Superform USA, Riverside, CA (United States)

    2004-07-01

    Since the invention of friction stir welding (FSW) in 1991, an increasing number of successful applications have been found for this unique solid-state welding technique. More recently, attention has been given to utilizing the mechanics of friction stirring to thermo-mechanically modify the microstructure of aluminum alloys to create or enhance superplasticity. Until now, superplasticity induced by friction stir processing (FSP) has only been demonstrated in small samples and evaluated by hot tensile elongation testing. The present work describes what we believe to be the first biaxial testing and full size component superplastic forming of friction stir processed aluminum sheet. The remarkable formability demonstrated in these 'first time' trials is described in detail. (orig.)

  9. Apparatus for forming an explosively expanded tube-tube sheet joint

    Schroeder, J.W.

    1984-01-01

    The invention relates to apparatus for expanding a tube into a bore formed in a tube sheet. According to the invention, a primary explosive containing a relatively high number of grains of explosive per unit length extends within the tube coextensive with that portion of the tube to be expanded. An energy transfer cord extends between a detonator and the primary explosive and includes a relatively low number of grains of explosive per unit length which are insufficient to detonate the primary explosive. The transfer cord is covered by a sheath to contain the debris and gases associated with the explosion of the explosive therein. A booster extends between the energy transfer cord and the primary explosive and contains an explosive which can be detonated by the explosive in the energy transfer cord and can, upon exploding, in turn detonate the primary explosive. (author)

  10. Implementation of virtual models from sheet metal forming simulation into physical 3D colour models using 3D printing

    Junk, S.

    2016-08-01

    Today the methods of numerical simulation of sheet metal forming offer a great diversity of possibilities for optimization in product development and in process design. However, the results from simulation are only available as virtual models. Because there are any forming tools available during the early stages of product development, physical models that could serve to represent the virtual results are therefore lacking. Physical 3D-models can be created using 3D-printing and serve as an illustration and present a better understanding of the simulation results. In this way, the results from the simulation can be made more “comprehensible” within a development team. This paper presents the possibilities of 3D-colour printing with particular consideration of the requirements regarding the implementation of sheet metal forming simulation. Using concrete examples of sheet metal forming, the manufacturing of 3D colour models will be expounded upon on the basis of simulation results.

  11. Impact Of Elastic Modulus Degradation On Springback In Sheet Metal Forming

    Halilovic, Miroslav; Stok, Boris; Vrh, Marko

    2007-01-01

    Strain recovery after removal of forming loads, commonly defined as springback, is of great concern in sheet metal forming, in particular with regard to proper prediction of the final shape of the part. To control the problem a lot of work has been done, either by minimizing the springback on the material side or by increasing the estimation precision in corresponding process simulations. Unfortunately, by currently available software springback still cannot be adequately predicted, because most analyses of springback are using linear, isotropic and constant Young's modulus and Poisson's ratio. But, as it was measured and reported, none of it is true. The aim of this work is to propose an upgraded mechanical model which takes evolution of damage and related orthotropic stiffness degradation into account. Damage is considered by inclusion of ellipsoidal cavities, and their influence on the stiffness degradation is taken in accordance with the Mori-Tanaka theory, adopting the GTN model for plastic flow. In order to improve the numerical springback prediction, two major things are important: first, the correct evaluation of the stress-strain state at the end of the forming process, and second, correctness of the elastic properties used in the elastic relaxation analysis. Since in modelling of the forming process we adopt a damage constitutive model with orthotropic stiffness degradation considered, a corresponding damage parameters identification upon specific experimental tests data must be performed first, independently of the metal forming modelling. An improved identification of material parameters, which simultaneously considers tensile test results with different type of specimens and using neural network, is proposed. With regard to the case in which damage in material is neglected it is shown in the article how the springback of a formed part differs, when we take orthotropic damage evolution into consideration

  12. Indirect Versus Direct Heating of Sheet Materials: Superplastic Forming and Diffusion Bonding Using Lasers

    Jocelyn, Alan; Kar, Aravinda; Fanourakis, Alexander; Flower, Terence; Ackerman, Mike; Keevil, Allen; Way, Jerome

    2010-06-01

    Many from within manufacturing industry consider superplastic forming (SPF) to be ‘high tech’, but it is often criticized as too complicated, expensive, slow and, in general, an unstable process when compared to other methods of manipulating sheet materials. Perhaps, the fundamental cause of this negative perception of SPF, and also of diffusion bonding (DB), is the fact that the current process of SPF/DB relies on indirect sources of heating to produce the conditions necessary for the material to be formed. Thus, heat is usually derived from the electrically heated platens of hydraulic presses, to a lesser extent from within furnaces and, sometimes, from heaters imbedded in ceramic moulds. Recent evaluations of these isothermal methods suggest they are slow, thermally inefficient and inappropriate for the process. In contrast, direct heating of only the material to be formed by modern, electrically efficient, lasers could transform SPF/DB into the first choice of designers in aerospace, automotive, marine, medical, architecture and leisure industries. Furthermore, ‘variable temperature’ direct heating which, in theory, is possible with a laser beam(s) may provide a means to control material thickness distribution, a goal of enormous importance as fuel efficient, lightweight structures for transportation systems are universally sought. This paper compares, and contrasts, the two systems and suggests how a change to laser heating might be achieved.

  13. On the effect of incremental forming on alpha phase precipitation and mechanical behavior of beta-Ti-10V-2Fe-3Al

    Winter, S.; F-X Wagner, M.

    2016-03-01

    A combination of good ductility and fatigue resistance makes β-titanium alloys interesting for many current and potential future applications. The mechanical behavior is primarily determined by microstructural parameters like (beta phase) grain size, morphology and volume fraction of primary / secondary α-phase precipitates, and this allows changing and optimizing their mechanical properties across a wide range. In this study, we investigate the possibility to modify the microstructure of the high-strength beta titanium alloy Ti-10V-2Fe-3Al, with a special focus on shape and volume fraction of primary α-phase. In addition to the conventional strategy for precipitation of primary α, a special thermo-mechanical processing is performed; this processing route combines the conventional heat treatment with incremental forming during the primary α-phase annealing. After incremental forming, considerable variations in terms of microstructure and mechanical properties can be obtained for different thermo-mechanical processing routes. The microstructures of the deformed samples are characterized by globular as well as lamellar (bimodal) α precipitates, whereas conventional annealing only results in the formation of lamellar precipitates. Because of the smaller size, and the lower amount, of α-phase after incremental forming, tensile strength is not as high as after the conventional strategy. However, high amounts of grain boundary α and lamellar αp-phase in the undeformed samples lead to a significantly lower ductility in comparison to the matrix with bimodal structures obtained by thermo-mechanical processing. These results illustrate the potential of incremental forming during the annealing to modify the microstructure of the beta titanium Ti-10V-2Fe-3Al in a wide range of volume fractions and morphologies of the primary α phase, which in turn leads to considerably changes, and improved, mechanical properties.

  14. Material characterization and finite element simulations of aluminum alloy sheets during non-isothermal forming process

    Zhang, Nan

    The utilization of more non-ferrous materials is one of the key factors to succeed out of the constantly increasing demand for lightweight vehicles in automotive sector. Aluminum-magnesium alloys have been identified as the most promising substitutions to the conventional steel without significant compromise in structural stiffness and strength. However, the conventional forming methods to deform the aluminum alloy sheets are either costly or insufficient in formability which limit the wide applications of aluminum alloy sheets. A recently proposed non-isothermal hot stamping approach, which is also referred as Hot Blank - Cold Die (HB-CD) stamping, aims at fitting the commercial grade aluminum alloy sheets, such as AA5XXX and AA7XXX, into high-volume and cost-effective production for automotive sector. In essence, HB-CD is a mutation of the conventional hot stamping approach for boron steel (22MnB5) which deforms the hot blank within the cold tool set. By elevating the operation temperature, the formability of aluminum alloy sheets can be significantly improved. Meanwhile, heating the blank only and deforming within the cold tool sets allow to reduce the energy and time consumed. This research work aims at conducting a comprehensive investigation of HB-CD with particular focuses on material characterization, constitutive modeling and coupled thermo-mechanical finite element simulations with validation. The material properties of AA5182-O, a popular commercial grade of aluminum alloy sheet in automotive sector, are obtained through isothermal tensile testing at temperatures from 25° to 300°, covering a quasi-static strain-rate range (0.001--0.1s-1). As the state-of-the-art non-contact strain measurement technique, digital image correlation (DIC) system is utilized to evaluate the stress-strain curves as well as to reveal the details of material deformation with full-field and multi-axis strain measurement. Material anisotropy is characterized by extracting the

  15. Springback Simulation and Tool Surface Compensation Algorithm for Sheet Metal Forming

    Shen Guozhe; Hu Ping; Zhang Xiangkui; Chen Xiaobin; Li Xiaoda

    2005-01-01

    Springback is an unquenchable forming defect in the sheet metal forming process. How to calculate springback accurately is a big challenge for a lot of FEA software. Springback compensation makes the stamped final part accordant with the designed part shape by modifying tool surface, which depends on the accurate springback amount. How ever, the meshing data based on numerical simulation is expressed by nodes and elements, such data can not be supplied directly to tool surface CAD data. In this paper, a tool surface compensation algorithm based on numerical simulation technique of springback process is proposed in which the independently developed dynamic explicit springback algorithm (DESA) is used to simulate springback amount. When doing the tool surface compensation, the springback amount of the projected point can be obtained by interpolation of the springback amount of the projected element nodes. So the modified values of tool surface can be calculated reversely. After repeating the springback and compensation calculations for 1∼3 times, the reasonable tool surface mesh is gained. Finally, the FEM data on the compensated tool surface is fitted into the surface by CAD modeling software. The examination of a real industrial part shows the validity of the present method

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

    Xu Da; Liu Xuesong; Fang Kun; Fang Hongyuan

    2010-01-01

    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.

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

    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.

  18. A sheet metal forming simulation of automotive outer panels considering the behavior of air in die cavity

    Choi, Kwang Yong; Kim, Yun Chang; Choi, Hee Kwan; Kang, Chul Ho; Kim, Heon Young

    2013-12-01

    During a sheet metal forming process of automotive outer panels, the air trapped between a blank sheet and a die tool can become highly compressed, ultimately influencing the blank deformation and the press force. To prevent this problem, vent holes are drilled into die tools and needs several tens to hundreds according to the model size. The design and the drilling of vent holes are based on expert's experience and try-out result and thus the process can be one of reasons increasing development cycle. Therefore the study on the size, the number, and the position of vent holes is demanded for reducing development cycle, but there is no simulation technology for analyzing forming defects, making numerical sheet metal forming process simulations that incorporate the fluid dynamics of air. This study presents a sheet metal forming simulation of automotive outer panels (a roof and a body side outer) that simultaneously simulates the behavior of air in a die cavity. Through CAE results, the effect of air behavior and vent holes to blank deformation was analyzed. For this study, the commercial software PAM-STAMP{trade mark, serif} and PAM-SAFE{trade mark, serif} was used.

  19. Characterization of the conformational space of a triple-stranded beta-sheet forming peptide with molecular dynamics simulations

    Soto, P; Colombo, G

    2004-01-01

    Molecular dynamics (MD) simulations have been performed on a series of mutants of the 20 amino acid peptide Betanova in order to critically assess the ability of MD simulations to reproduce the folding and stability of small beta-sheet-forming peptides on currently accessible timescales. Simulations

  20. Testing new tribo-systems for sheet metal forming of advanced high strength steels and stainless steels

    Bay, Niels; Ceron, Ermanno

    2014-01-01

    of a methodology for off-line testing of new tribo-systems for advanced high strength steels and stainless steels. The methodology is presented and applied to an industrial case, where different tribo-systems are tested. A universal sheet tribotester has been developed, which can run automatically repetitive......Testing of new tribo-systems in sheet metal forming has become an important issue due to new legislation, which forces industry to replace current, hazardous lubricants. The present paper summarizes the work done in a recent PhD project at the Technical University of Denmark on the development...

  1. Decontamination sheet

    Hirose, Emiko; Kanesaki, Ken.

    1995-01-01

    The decontamination sheet of the present invention is formed by applying an adhesive on one surface of a polymer sheet and releasably appending a plurality of curing sheets. In addition, perforated lines are formed on the sheet, and a decontaminating agent is incorporated in the adhesive. This can reduce the number of curing operation steps when a plurality steps of operations for radiation decontamination equipments are performed, and further, the amount of wastes of the cured sheets, and operator's exposure are reduced, as well as an efficiency of the curing operation can be improved, and propagation of contamination can be prevented. (T.M.)

  2. A Methodology for Off-line Evaluation of New Environmentally Friendly Tribo-systems for Sheet Metal Forming

    Ceron, Ermanno; Bay, Niels

    2013-01-01

    Increasing focus on environmental issues in industrial production has urged sheet stamping companies to look for new tribo-systems in order to substitute hazardous lubricants such as chlorinated paraffin oils. Production testing of new lubricants is, however, costly and makes industry reluctant...... towards testing alternative solutions. The present paper presents a methodology for off-line testing of new tribo-systems based on numerical modelling of production process as well as laboratory test to adjust the latter combined with testing of selected tribo-systems on a new automatic sheet......-tribo-tester emulating typical sheet forming production processes. Final testing of the tribo-systems in production verifies the methodology. © 2013 CIRP....

  3. An advanced constitutive model in the sheet metal forming simulation: the Teodosiu microstructural model and the Cazacu Barlat yield criterion

    Alves, J.L.; Oliveira, M.C.; Menezes, L.F.

    2004-01-01

    Two constitutive models used to describe the plastic behavior of sheet metals in the numerical simulation of sheet metal forming process are studied: a recently proposed advanced constitutive model based on the Teodosiu microstructural model and the Cazacu Barlat yield criterion is compared with a more classical one, based on the Swift law and the Hill 1948 yield criterion. These constitutive models are implemented into DD3IMP, a finite element home code specifically developed to simulate sheet metal forming processes, which generically is a 3-D elastoplastic finite element code with an updated Lagrangian formulation, following a fully implicit time integration scheme, large elastoplastic strains and rotations. Solid finite elements and parametric surfaces are used to model the blank sheet and tool surfaces, respectively. Some details of the numerical implementation of the constitutive models are given. Finally, the theory is illustrated with the numerical simulation of the deep drawing of a cylindrical cup. The results show that the proposed advanced constitutive model predicts with more exactness the final shape (medium height and ears profile) of the formed part, as one can conclude from the comparison with the experimental results

  4. A numerical simulation of thermodynamic processes for cryogenic metal forming of aluminum sheets and comparison with experimental results

    Reichl, Ch.; Schneider, R.; Hohenauer, W.; Grabner, F.; Grant, R.J.

    2017-01-01

    Highlights: • Thermodynamic processes for cryogenic sheet metal forming tools were examined. • Static and transient temperature field simulations are evaluated on a Nakajima tool. • Differently arranged cooling loops lead to homogeneous temperature distribution. • Scaling of the geometry leads to significantly increased heat transfer times. • The temperature management of complex forming tools can be developed numerically. - Abstract: Forming at cryogenic temperatures provides a significant improvement in formability of aluminum sheets. This offers the potential for light, complex and highly integrated one-piece components to be produced out of aluminum alloys at sub-zero temperatures. This would allow weight reduction, environmental conservation and cost reduction of a car body to give one example in the automotive industry. For temperature supported processes special forming tools and cooling strategies are required to be able to reach and maintain process stability. Time dependent numerical simulations of the thermodynamic processes of cryogenic sheet metal forming covering all aspects of heat transfer through conduction, convection and radiation play a vital role in the design and development of future tools and are presented for several geometries. Cooling (and heating) strategies (including selection of the number of cooling loops and their relative positioning) in a Nakajima testing tool were evaluated using computational fluid dynamics. These simulations were performed with static and transient solvers to demonstrate the extraction of tool surface temperature distributions on different forming tool geometries. Comparisons of predicted temperature characteristics of an aluminum sheet and experimentally determined temperature distributions were made. The temperature distribution of the surface of an aluminum sheet could be predicted with high accuracy. Further, the influence of the tool size on the parameters temperature transfer times and

  5. Strain- and stress-based forming limit curves for DP 590 steel sheet using Marciniak-Kuczynski method

    Kumar, Gautam; Maji, Kuntal

    2018-04-01

    This article deals with the prediction of strain-and stress-based forming limit curves for advanced high strength steel DP590 sheet using Marciniak-Kuczynski (M-K) method. Three yield criteria namely Von-Mises, Hill's 48 and Yld2000-2d and two hardening laws i.e., Hollomon power and Swift hardening laws were considered to predict the forming limit curves (FLCs) for DP590 steel sheet. The effects of imperfection factor and initial groove angle on prediction of FLC were also investigated. It was observed that the FLCs shifted upward with the increase of imperfection factor value. The initial groove angle was found to have significant effects on limit strains in the left side of FLC, and insignificant effect for the right side of FLC for certain range of strain paths. The limit strains were calculated at zero groove angle for the right side of FLC, and a critical groove angle was used for the left side of FLC. The numerically predicted FLCs considering the different combinations of yield criteria and hardening laws were compared with the published experimental results of FLCs for DP590 steel sheet. The FLC predicted using the combination of Yld2000-2d yield criterion and swift hardening law was in better coorelation with the experimental data. Stress based forming limit curves (SFLCs) were also calculated from the limiting strain values obtained by M-K model. Theoretically predicted SFLCs were compared with that obtained from the experimental forming limit strains. Stress based forming limit curves were seen to better represent the forming limits of DP590 steel sheet compared to that by strain-based forming limit curves.

  6. Effects of die quench forming on sheet thinning and 3-point bend testing of AA7075-T6

    Kim, Samuel; Omer, Kaab; Rahmaan, Taamjeed; Butcher, Clifford; Worswick, Michael

    2017-10-01

    Lab-scaled AA7075 aluminum side impact beams were manufactured using the die quenching technique in which the sheet was solutionized and then quenched in-die during forming to a super saturated solid state. Sheet thinning measurements were taken at various locations throughout the length of the part and the effect of lubricant on surface scoring and material pick-up on the die was evaluated. The as-formed beams were subjected to a T6 aging treatment and then tested in three-point bending. Simulations were performed of the forming and mechanical testing experiments using the LS-DYNA finite element code. The thinning and mechanical response was predicted well.

  7. Revisiting single-point incremental forming and formability/failure diagrams by means of finite elements and experimentation

    Silva, M. B.; Skjødt, Martin; Bay, Niels

    2009-01-01

    framework accounts for the influence of major process parameters and their mutual interaction to be studied both qualitatively and quantitatively. It enables the conclusion to be drawn that the probable mode of material failure in SPIF is consistent with stretching, rather than shearing being the governing...... mode of deformation. The study of the morphology of the cracks combined with the experimentally observed suppression of neck formation enabled the authors to conclude that traditional forming limit curves are inapplicable for describing failure. Instead, fracture forming limit curves should be employed...... the forming limits determined by the analytical framework with experimental values. It is shown that agreement between analytical, finite element, and experimental results is good, implying that the previously proposed analytical framework can be utilized to explain the mechanics of deformation...

  8. Prediction of stress- and strain-based forming limits of automotive thin sheets by numerical, theoretical and experimental methods

    Béres, Gábor; Weltsch, Zoltán; Lukács, Zsolt; Tisza, Miklós

    2018-05-01

    Forming limit is a complex concept of limit values related to the onset of local necking in the sheet metal. In cold sheet metal forming, major and minor limit strains are influenced by the sheet thickness, strain path (deformation history) as well as material parameters and microstructure. Forming Limit Curves are plotted in ɛ1 - ɛ2 coordinate system providing the classic strain-based Forming Limit Diagram (FLD). Using the appropriate constitutive model, the limit strains can be changed into the stress-based Forming Limit Diagram (SFLD), irrespective of the strain path. This study is about the effect of the hardening model parameters on defining of limit stress values during Nakazima tests for automotive dual phase (DP) steels. Five limit strain pairs were specified experimentally with the loading of five different sheet geometries, which performed different strain-paths from pure shear (-2ɛ2=ɛ1) up to biaxial stretching (ɛ2=ɛ1). The former works of Hill, Levy-Tyne and Keeler-Brazier made possible some kind of theoretical strain determination, too. This was followed by the stress calculation based on the experimental and theoretical strain data. Since the n exponent in the Nádai expression is varying with the strain at some DP steels, we applied the least-squares method to fit other hardening model parameters (Ludwik, Voce, Hockett-Sherby) to calculate the stress fields belonging to each limit strains. The results showed that each model parameters could produce some discrepancies between the limit stress states in the range of higher equivalent strains than uniaxial stretching. The calculated hardening models were imported to FE code to extend and validate the results by numerical simulations.

  9. Investigation into Composites Property Effect on the Forming Limits of Multi-Layer Hybrid Sheets Using Hydroforming Technology

    Liu, Shichen; Lang, Lihui; Guan, Shiwei; Alexandrov, Seigei; Zeng, Yipan

    2018-04-01

    Fiber-metal laminates (FMLs) such as Kevlar reinforced aluminum laminate (ARALL), Carbon reinforced aluminum laminate (CARALL), and Glass reinforced aluminum laminate (GLARE) offer great potential for weight reduction applications in automobile and aerospace construction. In order to investigate the feasibility for utilizing such materials in the form of laminates, sheet hydroforming technology are studied under the condition of uniform blank holder force for three-layered aluminum and aluminum-composite laminates using orthogonal carbon and Kevlar as well as glass fiber in the middle. The experimental results validate the finite element results and they exhibited that the forming limit of glass fiber in the middle is the highest among the studied materials, while carbon fiber material performs the worst. Furthermore, the crack modes are different for the three kinds of fiber materials investigated in the research. This study provides fundamental guidance for the selection of multi-layer sheet materials in the future manufacturing field.

  10. Finite element simulation of aluminum sheet warm forming using alflow hardening model

    Kurukuri, S.; van den Boogaard, Antonius H.; Huetink, Han

    2007-01-01

    In order to accurately model the plastic deformation of Aluminum sheet at elevated temperatures, a model is required that incorporate the temperature and strain rate dependency of the material. In this article, two physically based models are compared: Bergstr¨om and Alflow model. Although both

  11. Rubber pad forming - Efficient approach for the manufacturing of complex structured sheet metal blanks for food industry

    Spoelstra, Paul; Djakow, Eugen; Homberg, Werner

    2017-10-01

    The production of complex organic shapes in sheet metals is gaining more importance in the food industry due to increasing functional and hygienic demands. Hence it is necessary to produce parts with complex geometries promoting cleanability and general sanitation leading to improvement of food safety. In this context, and especially when stainless steel has to be formed into highly complex geometries while maintaining desired surface properties, it is inevitable that alternative manufacturing processes will need to be used which meet these requirements. Rubber pad forming offers high potential when it comes to shaping complex parts with excellent surface quality, with virtually no tool marks and scratches. Especially in cases where only small series are to be produced, rubber pad forming processes offers both technological and economic advantages. Due to the flexible punch, variation in metal thickness can be used with the same forming tool. The investments to set-up Rubber pad forming is low in comparison to conventional sheet metal forming processes. The process facilitates production of shallow sheet metal parts with complex contours and bends. Different bending sequences in a multiple tool set-up can also be conducted. The planned contribution thus describes a brief overview of the rubber pad technology. It shows the prototype rubber pad forming machine which can be used to perform complex part geometries made from stainless steel (1.4301). Based on an analysis of the already existing systems and new machines for rubber pad forming processes, together with their process properties, influencing variables and areas of application, some relevant parts for the food industry are presented.

  12. Comparison of Conventional Deep Drawing, Hydromechanical Deep-Drawing and High Pressure Sheet Metal Forming by Numerical Experiments

    Oender, I. Erkan; Tekkaya, A. Erman

    2005-01-01

    Increasing use of new technologies in automotive and aircraft applications requires intensive research and developments on sheet metal forming processes. This study focuses on the assessment of sheet hydroforming, hydro-mechanical deep drawing and conventional deep-drawing processes by performing a systematic analysis by numerical simulations. Circular, elliptic, rectangular and square cross-section cups have been selected for the geometry spectrum. Within the range of each cross section, depth, drawing ratio and fillet radii have been altered systematically. St14 stainless steel has been used as the material throughout the study. The deformation behavior has been described by an elasto-plastic material model and all numerical simulations have been carried out by using a dynamic-explicit commercial finite element code. During the analyses each workpiece is produced by the three competing processes. The analyses results such as sheet thickness distribution, necking, forming of radii etc., are used for assessing the success of each forming process alternative. The analyses revealed that depending on the workpiece geometry and dimensional properties certain processes are preferable for obtaining satisfactory products. The process windows for each process have been established based on the analyzed parameters of the three different product geometries. This data is expected to be useful for selecting the appropriate production process for a given workpiece geometry

  13. Development of an in-plane biaxial test for forming limit curve (FLC) characterization of metallic sheets

    Zidane, I; Guines, D; Léotoing, L; Ragneau, E

    2010-01-01

    The main objective of this work is to propose a new experimental device able to give for a single specimen a good prediction of rheological parameters and formability under static and dynamic conditions (for intermediate strain rates). In this paper, we focus on the characterization of sheet metal forming. The proposed device is a servo-hydraulic testing machine provided with four independent dynamic actuators allowing biaxial tensile tests on cruciform specimens. The formability is evaluated thanks to the classical forming limit diagram (FLD), and one of the difficulties of this study was the design of a dedicated specimen for which the necking phenomenon appears in its central zone. If necking is located in the central zone of the specimen, then the speed ratio between the two axes controls the strain path in this zone and a whole forming limit curve can be covered. Such a specimen is proposed through a numerical and experimental validation procedure. A rigorous procedure for the detection of numerical and experimental forming strains is also presented. Finally, an experimental forming limit curve is determined and validated for an aluminium alloy dedicated to the sheet forming processes (AA5086)

  14. Orientation-related phenomena in Al-Li sheet during superplastic forming

    Randle, V.; Wilshire, B.

    1996-01-01

    The microtexture of superplastically deformed 8090 Al-Li sheet has been measured using electron back-scatter diffraction, for true strains of 0, 0.25, 0.75, 1.5 and 2.4. The data have been interpreted in terms of individual texture variants, grain boundary types (low angle or high angle) and grain junction types (I-lines or U -lines, as defined by an extension to the 0-lattice theory)

  15. Improvement of formability for fabricating thin continuously corrugated structures in sheet metal forming process

    Choi, Sung Woo; Park, Sang Hu; Park, Seong Hun; Ha, Man Yeong; Jeong, Ho Seung; Cho, Jong Rae

    2012-01-01

    A stamping process is widely used for fabricating various sheet metal parts for vehicles, airplanes, and electronic devices by the merit of low processing cost and high productivity. Recently, the use of thin sheets with a corrugated structure for sheet metal parts has rapidly increased for use in energy management devices, such as heat exchangers, separators in fuel cells, and many others. However, it is not easy to make thin corrugated structures directly using a single step stamping process due to their geometrical complexity and very thin thickness. To solve this problem, a multi step stamping (MSS) process that includes a heat treatment process to improve formability is proposed in this work: the sequential process is the initial stamping, heat treatment, and final shaping. By the proposed method, we achieved successful results in fabricating thin corrugated structures with an average thickness of 75μm and increased formability of about 31% compared to the single step stamping process. Such structures can be used in a plate-type heat exchanger requiring low weight and a compact shape

  16. Advanced `KS-6` dry type lubricant for aluminum sheet forming; Arumi ban seikeiyo koseino kokei junkatsuzai `KS-5`

    Matsui, K.; Sugita, T.; Imamura, Y. [Kobe Steel, Ltd., Kobe (Japan)

    1997-09-01

    The advanced `KS-5` dry film type lubricant was developed for press forming of aluminum sheets. KS-5 uses water- soluble resin poly-alkylene-oxide superior in formability, weldability and adhesivity, and contains higher fatty-acid soap as oil solvent to improve a formability. The verification test result of KS-5 is as follows. Both stretchability and drawability were confirmed through a ball head stretching test and a cylinder drawing test as formability test, respectively, and a forming height more than that of mild steel sheets was obtained by using the solid lubricant showing a high stretchability. The drawability of nearly 80% of that of mild steel sheets was also obtained showing a high formability. Since the amount of the solid lubricant has reciprocal effect on the formability and degreasing property, it is important to select the suitable amount of the solid lubricant according to use conditions. Lubricants generally deteriorate a spot weldability, however, this lubricant has no practical problems by coating rust preventive oil. 3 refs., 8 figs., 3 tabs.

  17. Die design optimization on sheet metal forming with considering the phenomenon of springback to improve product quality

    Darmawan Agung Setyo

    2018-01-01

    Full Text Available The process of sheet metal forming is one of the very important processes in manufacture of products mainly in the automotive field. In sheet metal forming, it is added a certain size at the die to tolerate a result of the elasticity restoration of material. Therefore, when the product is removed from the die then the process elastic recovery will end within the allowable tolerance size. Extra size of the die is one method to compensate for springback. The aim of this research is to optimize the die by entering a springback value in die design to improve product quality that is associated with accuracy the final size of the product. Simulation processes using AutoForm software are conducted to determine the optimal parameters to be used in the forming process. Variations the Blank Holder Force of 77 N, 97 N, and 117 N are applied to the plate material. The Blank Holder Force application higher than 97 N cannot be conducted because the Forming Limit Diagram indicates the risk of tearing. Then the Blank Holder Force of 37 N, 57 N and 77 N are selected and applied in cup drawing process. Even though a few of wrinkling are appear, however there is no significant deviation of dimension between the product and the design of cup.

  18. Experimental research and numerical optimisation of multi-point sheet metal forming implementation using a solid elastic cushion system

    Tolipov, A. A.; Elghawail, A.; Shushing, S.; Pham, D.; Essa, K.

    2017-09-01

    There is a growing demand for flexible manufacturing techniques that meet the rapid changes in customer needs. A finite element analysis numerical optimisation technique was used to optimise the multi-point sheet forming process. Multi-point forming (MPF) is a flexible sheet metal forming technique where the same tool can be readily changed to produce different parts. The process suffers from some geometrical defects such as wrinkling and dimpling, which have been found to be the cause of the major surface quality problems. This study investigated the influence of parameters such as the elastic cushion hardness, blank holder force, coefficient of friction, cushion thickness and radius of curvature, on the quality of parts formed in a flexible multi-point stamping die. For those reasons, in this investigation, a multipoint forming stamping process using a blank holder was carried out in order to study the effects of the wrinkling, dimpling, thickness variation and forming force. The aim was to determine the optimum values of these parameters. Finite element modelling (FEM) was employed to simulate the multi-point forming of hemispherical shapes. Using the response surface method, the effects of process parameters on wrinkling, maximum deviation from the target shape and thickness variation were investigated. The results show that elastic cushion with proper thickness and polyurethane with the hardness of Shore A90. It has also been found that the application of lubrication cans improve the shape accuracy of the formed workpiece. These final results were compared with the numerical simulation results of the multi-point forming for hemispherical shapes using a blank-holder and it was found that using cushion hardness realistic to reduce wrinkling and maximum deviation.

  19. Avidin-biotin-based approach to forming heterotypic cell clusters and cell sheets on a gas-permeable membrane

    Hamon, M; Ozawa, T; Montagne, K; Kojima, N; Ishii, R; Sakai, Y [Institute of Industrial Science (IIS), University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Yamaguchi, S; Nagamune, T [Department of Bioengineering, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Ushida, T, E-mail: mzh0026@auburn.edu [Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2011-09-15

    Implantation of sheet-like liver tissues is a promising method in hepatocyte-based therapies, because angiogenesis is expected to occur upon implantation from the surrounding tissues. In this context, we introduce here a new methodology for the formation of a functional thick hepatic tissue usable for cell sheet technology. First, we report the formation of composite tissue elements in suspension culture. Composite elements were composed of human hepatoma Hep G2 cells and mouse NIH/3T3 fibroblasts which are important modulators for thick-tissue formation. To overcome the very low attachment and organization capability between different cells in suspension, we synthesized a new cell-to-cell binding molecule based on the avidin-biotin binding system that we previously applied to attach hepatocytes on artificial substrata. This newly synthesized biotin-conjugated biocompatible anchoring molecule was inserted in the plasma membrane of both cell types. NIH/3T3 cells were further conjugated with avidin and incubated with biotin-presenting Hep G2 cells to form highly composite tissue elements. Then, we seeded those elements on highly gas-permeable membranes at their closest packing density to induce the formation of a thick, composite, functional hepatic tissue without any perfusion. This methodology could open a new way to engineer implantable thick liver tissue sheets where different cell types are spatially organized and well supplied with oxygen.

  20. Explosive Forming of Low Carbon Steel Sheet into a Stepped Disc Shape

    S. Balasubramanian; S. Sarvat Ali; E.S. Bhagiradha Rao

    1984-01-01

    This paper deals with the explosive forming of deep drawing quality steel into a two stepped disc type shape. An attempt has been made to predict the forming parameters from theoretical considerations by equating the disc shape with an equivalent dome. Results of forming this shape in a single stage vis-a-vis forming in two stages are compared.

  1. Determination of friction in sheet metal forming by means of simulative tribo-tests

    Ceron, Ermanno; Bay, Niels

    2013-01-01

    operations a coefficient of friction μ is often determined by calibration of the simulation results with experimental observations of material flow and/or measured load. In case of modeling of new stamping operations μ is typically selected based on former experience. These procedures are, however......, not appropriate when introducing new tribo-systems (lubricant, workpiece material, tool material or tool coating). In order to determine friction under the very varied conditions in sheet stamping simulative testing may be applied, e.g., Plane-Strip-Testing (PST), Draw-Bead-Testing (DBT) and Bending......-Under- Tension testing (BUT) but these tests should be analyzed and carefully tuned with the production process in question to ensure useful results. The present paper illustrates how the BUT test combined with classical analytical modeling may lead to very large errors in estimation of the coefficient...

  2. Contact Modelling in Isogeometric Analysis: Application to Sheet Metal Forming Processes

    Cardoso, Rui P. R.; Adetoro, O. B.; Adan, D.

    2016-08-01

    Isogeometric Analysis (IGA) has been growing in popularity in the past few years essentially due to the extra flexibility it introduces with the use of higher degrees in the basis functions leading to higher convergence rates. IGA also offers the capability of easily reproducing discontinuous displacement and/or strain fields by just manipulating the multiplicity of the knot parametric coordinates. Another advantage of IGA is that it uses the Non-Uniform Rational B-Splines (NURBS) basis functions, that are very common in CAD solid modelling, and consequently it makes easier the transition from CAD models to numerical analysis. In this work it is explored the contact analysis in IGA for both implicit and explicit time integration schemes. Special focus will be given on contact search and contact detection techniques under NURBS patches for both the rigid tools and the deformed sheet blank.

  3. Effectiveness of Rotation-free Triangular and Quadrilateral Shell Elements in Sheet-metal Forming Simulations

    Brunet, M.; Sabourin, F.

    2005-01-01

    This paper is concerned with the effectiveness of triangular 3-node shell element without rotational d.o.f. and the extension to a new 4-node quadrilateral shell element called S4 with only 3 translational degrees of freedom per node and one-point integration. The curvatures are computed resorting to the surrounding elements. Extension from rotation-free triangular element to a quadrilateral element requires internal curvatures in order to avoid singular bending stiffness. Two numerical examples with regular and irregular meshes are performed to show the convergence and accuracy. Deep-drawing of a box, spring-back analysis of a U-shape strip sheet and the crash simulation of a beam-box complete the demonstration of the bending capabilities of the proposed rotation-free triangular and quadrilateral elements

  4. Methods of forming aluminum oxynitride-comprising bodies, including methods of forming a sheet of transparent armor

    Chu, Henry Shiu-Hung [Idaho Falls, ID; Lillo, Thomas Martin [Idaho Falls, ID

    2008-12-02

    The invention includes methods of forming an aluminum oxynitride-comprising body. For example, a mixture is formed which comprises A:B:C in a respective molar ratio in the range of 9:3.6-6.2:0.1-1.1, where "A" is Al.sub.2O.sub.3, "B" is AlN, and "C" is a total of one or more of B.sub.2O.sub.3, SiO.sub.2, Si--Al--O--N, and TiO.sub.2. The mixture is sintered at a temperature of at least 1,600.degree. C. at a pressure of no greater than 500 psia effective to form an aluminum oxynitride-comprising body which is at least internally transparent and has at least 99% maximum theoretical density.

  5. Forming Limit Diagrams of Zircaloy-4 and Zirlo Sheets for Stamping of Spacer Grids of Nuclear Fuel Rods

    Seo, Yun Mi; Hyun, Hong Chul; Lee, Hyung Yil; Kim, Nak Soo

    2011-01-01

    In this work, we investigated the theoretical forming limit models for Zircaloy-4 and Zirlo used for spacer grid of nuclear fuel rods. Tensile and anisotropy tests were performed to obtain stress-strain curves and anisotropic coefficients. The experimental forming limit diagrams (FLD) for two materials were obtained by dome stretching tests following NUMISHEET 96. Theoretical FLD depends on FL models and yield criteria. To obtain the right hand side (RHS) of FLD, we applied the FL models (Swift's diffuse necking, M-K theory, S-R vertex theory) to Zircaloy-4 and Zirlo sheets. Hill's local necking theory was adopted for the left hand side (LHS) of FLD. To consider the anisotropy of sheets, the yield criteria of Hill and Hosford were applied. Comparing the predicted curves with the experimental data, we found that the RHS of FLD for Zircaloy-4 can be described by the Swift model (with the Hill's criterion), while the LHS of the FLD can be explained by Hill model. The FLD for Zirlo can be explained by the S-R model and the Hosford's criterion (a = 8)

  6. Beta-Sheet-Forming, Self-Assembled Peptide Nanomaterials towards Optical, Energy, and Healthcare Applications.

    Kim, Sungjin; Kim, Jae Hong; Lee, Joon Seok; Park, Chan Beum

    2015-08-12

    Peptide self-assembly is an attractive route for the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide-based, self-assembled materials have expanded beyond the construction of high-order architectures; they are now reporting new functional materials that have application in the emerging fields such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been few reviews particularly concentrating on such versatile, emerging applications. Herein, recent advances in the synthesis of self-assembled peptide nanomaterials (e.g., cross β-sheet-based amyloid nanostructures, peptide amphiphiles) are selectively reviewed and their new applications in diverse, interdisciplinary fields are described, ranging from optics and energy storage/conversion to healthcare. The applications of peptide-based self-assembled materials in unconventional fields are also highlighted, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium-ion battery components. The relation of such functional materials to the rapidly progressing biomedical applications of peptide self-assembly, which include biosensors/chips and regenerative medicine, are discussed. The combination of strategies shown in these applications would further promote the discovery of novel, functional, small materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. STUDY THE EFFECTS OF PRESTRAINS IN UNIAXIAL TENSION ON THE FORMING LIMIT DIAGRAM OF ALUMINUM ALLOY SHEETS(2024 T3

    Waleed J. Ali

    2015-02-01

    Full Text Available           The strain path for sheet metal may be changed during forming , this may be affect the forming limit curve (FLC . In this work the FLC before and after prestraining was determined for aluminum alloy (2024 T3 to study the effect of this type of prestraining and in different values on the FLC. This alloy was chosen because it is used widely , specially in aircraft structures .It was shown that the using of uniaxial tension prestrain affects the FLC . The major strain in right side is increased with the increasing in the prestrain , while in the left side the effect is small .

  8. Evidence for a current sheet forming in the wake of a coronal mass ejection from multi-viewpoint coronagraph observations

    Patsourakos, S.; Vourlidas, A.

    2011-01-01

    sheets. Therefore, our multi-viewpoint observations supply strong evidence that the observed post-CME ray is indeed related to a post-CME current sheet. Movies are only available in electronic form at http://www.aanda.org

  9. Sensitivity and variability of Presage dosimeter formulations in sheet form with application to SBRT and SRS QA

    Dumas, Michael, E-mail: mdumas1127@gmail.com [Department of Radiation Oncology, Wayne State University School of Medicine and Karmanos Cancer Institute Detroit, Detroit, Michigan 48201 and Department of Radiation Oncology, Henry Ford Hospital, Detroit, Michigan 48202 (United States); Rakowski, Joseph T. [Department of Radiation Oncology, Wayne State University School of Medicine and Karmanos Cancer Institute Detroit, Detroit, Michigan 48201 (United States)

    2015-12-15

    Purpose: To measure sensitivity and stability of the Presage dosimeter in sheet form for various chemical concentrations over a range of clinical photon energies and examine its use for stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) QA. Methods: Presage polymer dosimeters were formulated to investigate and optimize their sensitivity and stability. The dosimeter is composed of clear polyurethane base, leucomalachite green (LMG) reporting dye, and bromoform radical initiator in 0.9–1.0 mm thick sheets. The chemicals are mixed together for 2 min, cast in an aluminum mold, and left to cure at 60 psi for a minimum of two days. Dosimeter response was characterized at energies Co-60, 6 MV, 10 MV flattening-filter free, 15 MV, 50 kVp (mean 19.2 keV), and Ir-192. The dosimeters were scanned by a Microtek Scanmaker i800 at 300 dpi, 2{sup 16} bit depth per color channel. Red component images were analyzed with ImageJ and RIT. SBRT QA was done with gamma analysis tolerances of 2% and 2 mm DTA. Results: The sensitivity of the Presage dosimeter increased with increasing concentration of bromoform. Addition of tin catalyst decreased curing time and had negligible effect on sensitivity. LMG concentration should be at least as high as the bromoform, with ideal concentration being 2% wt. Gamma Knife SRS QA measurements of relative output and profile widths were within 2% of manufacturer’s values validated at commissioning, except the 4 mm collimator relative output which was within 3%. The gamma pass rate of Presage with SBRT was 73.7%, compared to 93.1% for EBT2 Gafchromic film. Conclusions: The Presage dosimeter in sheet form was capable of detecting radiation over all tested photon energies and chemical concentrations. The best sensitivity and photostability of the dosimeter were achieved with 2.5% wt. LMG and 8.2% wt. bromoform. Scanner used should not emit any UV radiation as it will expose the dosimeter, as with the Epson 10000 XL scanner

  10. Multi-scale friction modeling for sheet metal forming: the boundary lubrication regime

    Hol, J.D.; Meinders, Vincent T.; de Rooij, Matthias B.; van den Boogaard, Antonius H.

    2015-01-01

    A physical based friction model is presented to describe friction in full-scale forming simulations. The advanced friction model accounts for the change in surface topography and the evolution of friction in the boundary lubrication regime. The implementation of the friction model in FE software

  11. Paradigm Change: Alternate Approaches to Constitutive and Necking Models for Sheet Metal Forming

    Stoughton, Thomas B.; Yoon, Jeong Whan

    2011-01-01

    This paper reviews recent work proposing paradigm changes for the currently popular approach to constitutive and failure modeling, focusing on the use of non-associated flow rules to enable greater flexibility to capture the anisotropic yield and flow behavior of metals using less complex functions than those needed under associated flow to achieve that same level of fidelity to experiment, and on the use of stress-based metrics to more reliably predict necking limits under complex conditions of non-linear forming. The paper discusses motivating factors and benefits in favor of both associated and non-associated flow models for metal forming, including experimental, theoretical, and practical aspects. This review is followed by a discussion of the topic of the forming limits, the limitations of strain analysis, the evidence in favor of stress analysis, the effects of curvature, bending/unbending cycles, triaxial stress conditions, and the motivation for the development of a new type of forming limit diagram based on the effective plastic strain or equivalent plastic work in combination with a directional parameter that accounts for the current stress condition.

  12. Tool degradation during sheet metal forming of three stainless steel alloys

    Wadman, Boel; Nielsen, Peter Søe; Wiklund, Daniel

    2010-01-01

    To evaluate if changes in tool design and tool surface preparation are needed when low-Ni stainless steels are used instead of austenitic stainless steels, the effect on tool degradation in the form of galling was investigated with three different types of stainless steel. The resistance to tool ...

  13. Application Of A New Semi-Empirical Model For Forming Limit Prediction Of Sheet Material Including Superposed Loads Of Bending And Shearing

    Held, Christian; Liewald, Mathias; Schleich, Ralf; Sindel, Manfred

    2010-06-01

    The use of lightweight materials offers substantial strength and weight advantages in car body design. Unfortunately such kinds of sheet material are more susceptible to wrinkling, spring back and fracture during press shop operations. For characterization of capability of sheet material dedicated to deep drawing processes in the automotive industry, mainly Forming Limit Diagrams (FLD) are used. However, new investigations at the Institute for Metal Forming Technology have shown that High Strength Steel Sheet Material and Aluminum Alloys show increased formability in case of bending loads are superposed to stretching loads. Likewise, by superposing shearing on in plane uniaxial or biaxial tension formability changes because of materials crystallographic texture. Such mixed stress and strain conditions including bending and shearing effects can occur in deep-drawing processes of complex car body parts as well as subsequent forming operations like flanging. But changes in formability cannot be described by using the conventional FLC. Hence, for purpose of improvement of failure prediction in numerical simulation codes significant failure criteria for these strain conditions are missing. Considering such aspects in defining suitable failure criteria which is easy to implement into FEA a new semi-empirical model has been developed considering the effect of bending and shearing in sheet metals formability. This failure criterion consists of the combination of the so called cFLC (combined Forming Limit Curve), which considers superposed bending load conditions and the SFLC (Shear Forming Limit Curve), which again includes the effect of shearing on sheet metal's formability.

  14. Application Of A New Semi-Empirical Model For Forming Limit Prediction Of Sheet Material Including Superposed Loads Of Bending And Shearing

    Held, Christian; Liewald, Mathias; Schleich, Ralf; Sindel, Manfred

    2010-01-01

    The use of lightweight materials offers substantial strength and weight advantages in car body design. Unfortunately such kinds of sheet material are more susceptible to wrinkling, spring back and fracture during press shop operations. For characterization of capability of sheet material dedicated to deep drawing processes in the automotive industry, mainly Forming Limit Diagrams (FLD) are used. However, new investigations at the Institute for Metal Forming Technology have shown that High Strength Steel Sheet Material and Aluminum Alloys show increased formability in case of bending loads are superposed to stretching loads. Likewise, by superposing shearing on in plane uniaxial or biaxial tension formability changes because of materials crystallographic texture. Such mixed stress and strain conditions including bending and shearing effects can occur in deep-drawing processes of complex car body parts as well as subsequent forming operations like flanging. But changes in formability cannot be described by using the conventional FLC. Hence, for purpose of improvement of failure prediction in numerical simulation codes significant failure criteria for these strain conditions are missing. Considering such aspects in defining suitable failure criteria which is easy to implement into FEA a new semi-empirical model has been developed considering the effect of bending and shearing in sheet metals formability. This failure criterion consists of the combination of the so called cFLC (combined Forming Limit Curve), which considers superposed bending load conditions and the SFLC (Shear Forming Limit Curve), which again includes the effect of shearing on sheet metal's formability.

  15. Surface Defects in Sheet Metal Forming: a Simulative Laboratory Device and Comparison with FE Analysis

    Thuillier, Sandrine; Le Port, Alban; Manach, Pierre-Yves

    2011-08-01

    Surface defects are small concave imperfections that can develop during forming on outer convex panels of automotive parts like doors. They occur during springback steps, after drawing in the vicinity of bending over a curved line and flanging/hemming in the vicinity of the upper corner of a door. They can alter significantly the final quality of the automobile and it is of primary importance to deal with them as early as possible in the design of the forming tools. The aim of this work is to reproduce at the laboratory scale such a defect, in the case of the flanging along a curved edge, made of two orthogonal straight part of length 50 mm and joint by a curved line. A dedicated device has been designed and steel samples were tested. Each sample was measured initially (after laser cutting) and after flanging, with a 3D measuring machine. 2D profiles were extracted and the curvature was calculated. Surface defects were defined between points where the curvature sign changed. Isovalues of surface defect depth could then be plotted, thus displaying also the spatial geometry on the part surface. An experimental database has been created on the influence of process parameters like the flanging height and the flanging radius. Numerical simulations have been performed with the finite element code Abaqus to predict the occurrence of such surface defects and to analyze stress and strain distribution within the defect area.

  16. Acquisition of material properties in production for sheet metal forming processes

    Heingärtner, Jörg; Hora, Pavel; Neumann, Anja; Hortig, Dirk; Rencki, Yasar

    2013-01-01

    In past work a measurement system for the in-line acquisition of material properties was developed at IVP. This system is based on the non-destructive eddy-current principle. Using this system, a 100% control of material properties of the processed material is possible. The system can be used for ferromagnetic materials like standard steels as well as paramagnetic materials like Aluminum and stainless steel. Used as an in-line measurement system, it can be configured as a stand-alone system to control material properties and sort out inapplicable material or as part of a control system of the forming process. In both cases, the acquired data can be used as input data for numerical simulations, e.g. stochastic simulations based on real world data

  17. New tribo-systems for sheet metal forming of advanced high strength steels and stainless steels

    Ceron, Ermanno

    that the performance of the workpiece materials have to improve in order to satisfy higher strength and lower weight requirements. This however leads to challenges in the forming operation, especially when high surface expansion and elevated strain are involved. The challenge is to achieve long production run...... Tribotester was developed. A production process was selected at Grundfos, which is currently running with chlorinated paraffin oil. The process includes a deep drawing and two subsequent re-drawings in a progressive tool. The process was numerically analyzed to investigate the tribological conditions....... A suitable laboratory test (BUT test) was selected to simulate the production process. The BUT test was numerically analyzed to verify that the tribological conditions are close to the production process ones. A few interesting new tribo-systems were selected to be investigated in the BUT test. Some of them...

  18. Fabrication of Hadfield-Cored Multi-layer Steel Sheet by Roll-Bonding with 1.8-GPa-Strength-Grade Hot-Press-Forming Steel

    Chin, Kwang-Geun; Kang, Chung-Yun; Park, Jaeyeong; Lee, Sunghak

    2018-05-01

    An austenitic Hadfield steel was roll-bonded with a 1.8-GPa-strength-grade martensitic hot-press-forming (HPF) steel to fabricate a multi-layer steel (MLS) sheet. Near the Hadfield/HPF interface, the carburized and decarburized layers were formed by the carbon diffusion from the Hadfield (1.2%C) to HPF (0.35%C) layers, and could be regarded as kinds of very thin multi-layers of 35 μm in thickness. The tensile test and fractographic data indicated that the MLS sheet was fractured abruptly within the elastic range by the intergranular fracture occurred in the carburized layer. This was because C was mainly segregated at prior austenite grain boundaries in the carburized layer, which weakened grain boundaries to induce the intergranular fracture. In order to solve the intergranular facture problem, the MLS sheet was tempered at 200 °C. The stress-strain curve of the tempered MLS sheet lay between those of the HPF and Hadfield sheets, and a rule of mixtures was roughly satisfied. Tensile properties of the MLS sheet were dramatically improved after the tempering, and the intergranular fracture was erased completely. In particular, the yield strength up to 1073 MPa along with the high strain hardening and excellent ductility of 32.4% were outstanding because the yield strength over 1 GPa was hardly achieved in conventional austenitic steels.

  19. Tribological evaluation of surface modified H13 tool steel in warm forming of Ti–6Al–4V titanium alloy sheet

    Wang, Dan; Li, Heng; Yang, He; Ma, Jun; Li, Guangjun

    2014-01-01

    The H13 hot-working tool steel is widely used as die material in the warm forming of Ti–6Al–4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti–6Al–4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods (c...

  20. Effect of stereochemistry, chain length and sequence pattern on antimicrobial properties of short synthetic β-sheet forming peptide amphiphiles.

    Ong, Zhan Yuin; Cheng, Junchi; Huang, Yuan; Xu, Kaijin; Ji, Zhongkang; Fan, Weimin; Yang, Yi Yan

    2014-01-01

    In the face of mounting global antibiotics resistance, the identification and development of membrane-active antimicrobial peptides (AMPs) as an alternative class of antimicrobial agent have gained significant attention. The physical perturbation and disruption of microbial membranes by the AMPs have been proposed to be an effective means to overcome conventional mechanisms of drug resistance. Recently, we have reported the design of a series of short synthetic β-sheet folding peptide amphiphiles comprised of recurring (X1Y1X2Y2)n-NH2 sequences where X: hydrophobic amino acids, Y: cationic amino acids and n: number of repeat units. In efforts to investigate the effects of key parameters including stereochemistry, chain length and sequence pattern on antimicrobial effects, systematic d-amino acid substitutions of the lead peptides (IRIK)2-NH2 (IK8-all L) and (IRVK)3-NH2 (IK12-all L) were performed. It was found that the corresponding D-enantiomers exhibited stronger antimicrobial activities with minimal or no change in hemolytic activities, hence translating very high selectivity indices of 407.0 and >9.8 for IK8-all D and IK12-all D respectively. IK8-all D was also demonstrated to be stable to degradation by broad spectrum proteases trypsin and proteinase K. The membrane disrupting bactericidal properties of IK8-all D effectively prevented drug resistance development and inhibited the growth of various clinically isolated MRSA, VRE, Acinetobacter baumanni, Pseudomonas aeruginosa, Cryptococcus. neoformans and Mycobacterium tuberculosis. Significant reduction in intracellular bacteria counts was also observed following treatment with IK8-all D in the Staphylococcus. aureus infected mouse macrophage cell line RAW264.7 (P < 0.01). These results suggest that the d-amino acids substituted β-sheet forming peptide IK8-all D with its enhanced antimicrobial activities and improved protease stability, is a promising therapeutic candidate with potential to combat

  1. Accurate hardening modeling as basis for the realistic simulation of sheet forming processes with complex strain-path changes

    Levkovitch, Vladislav; Svendsen, Bob

    2007-01-01

    Sheet metal forming involves large strains and severe strain-path changes. Large plastic strains lead in many metals to the development of persistent dislocation structures resulting in strong flow anisotropy. This induced anisotropic behavior manifests itself in the case of a strain path change through very different stress-strain responses depending on the type of the strain-path change. While many metals exhibit a drop of the yield stress (Bauschinger effect) after a load reversal, some metals show an increase of the yield stress after an orthogonal strain-path change (so-called cross hardening). To model the Bauschinger effect, kinematic hardening has been successfully used for years. However, the usage of the kinematic hardening leads automatically to a drop of the yield stress after an orthogonal strain-path change contradicting tests exhibiting the cross hardening effect. Another effect, not accounted for in the classical elasto-plasticity, is the difference between the tensile and compressive strength, exhibited e.g. by some steel materials. In this work we present a phenomenological material model whose structure is motivated by polycrystalline modeling that takes into account the evolution of polarized dislocation structures on the grain level - the main cause of the induced flow anisotropy on the macroscopic level. The model considers besides the movement of the yield surface and its proportional expansion, as it is the case in conventional plasticity, also the changes of the yield surface shape (distortional hardening) and accounts for the pressure dependence of the flow stress. All these additional attributes turn out to be essential to model the stress-strain response of dual phase high strength steels subjected to non-proportional loading

  2. Accurate Hardening Modeling As Basis For The Realistic Simulation Of Sheet Forming Processes With Complex Strain-Path Changes

    Levkovitch, Vladislav; Svendsen, Bob

    2007-01-01

    Sheet metal forming involves large strains and severe strain-path changes. Large plastic strains lead in many metals to the development of persistent dislocation structures resulting in strong flow anisotropy. This induced anisotropic behavior manifests itself in the case of a strain path change through very different stress-strain responses depending on the type of the strain-path change. While many metals exhibit a drop of the yield stress (Bauschinger effect) after a load reversal, some metals show an increase of the yield stress after an orthogonal strain-path change (so-called cross hardening). To model the Bauschinger effect, kinematic hardening has been successfully used for years. However, the usage of the kinematic hardening leads automatically to a drop of the yield stress after an orthogonal strain-path change contradicting tests exhibiting the cross hardening effect. Another effect, not accounted for in the classical elasto-plasticity, is the difference between the tensile and compressive strength, exhibited e.g. by some steel materials. In this work we present a phenomenological material model whose structure is motivated by polycrystalline modeling that takes into account the evolution of polarized dislocation structures on the grain level - the main cause of the induced flow anisotropy on the macroscopic level. The model considers besides the movement of the yield surface and its proportional expansion, as it is the case in conventional plasticity, also the changes of the yield surface shape (distortional hardening) and accounts for the pressure dependence of the flow stress. All these additional attributes turn out to be essential to model the stress-strain response of dual phase high strength steels subjected to non-proportional loading

  3. Crystallization behaviors of Zr-Ti-Cu-Ni-Be BMG sheet fabricated by squeeze-casting method and its micro-scaled forming

    Jeong, H.G. [Advanced Fusion Process Group, Production Technology R and D Department, Korea Institute of Industrial Technology, Incheon (Korea, Republic of); Lee, J.B., E-mail: ljb01@kitech.re.kr [Advanced Fusion Process Group, Production Technology R and D Department, Korea Institute of Industrial Technology, Incheon (Korea, Republic of)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Compressibility and formability of Zr{sub 62.6}Ti{sub 11}Cu{sub 13.2}Ni{sub 9.8}Be{sub 3.4} BMG sheets increases with an increase in forging temperature and pressure. Black-Right-Pointing-Pointer Crystallization in the alloy BMG sheet began to occur during micro-scaled forming. Black-Right-Pointing-Pointer The volume fraction of crystalline phase increases as the forging temperature and pressure increase. - Abstract: We report the micro-scaled forming of Zr{sub 62.6}Ti{sub 11}Cu{sub 13.2}Ni{sub 9.8}Be{sub 3.4} bulk metallic glass (BMG) as a function of the forging pressure within super-cooled liquid region (SLR), and its effects on the transition to crystallization. The morphology after micro-scaled forming was examined by using a field emission scanning electron microscope (FE-SEM). Thermal behavior of the forged samples was analyzed by using a differential scanning calorimeter (DSC). It was found for perfect forming of the alloy BMG sheets that the temperature of 703 K and the pressure of 20 MPa are required in the present study. The compressibility and the volume fraction of crystalline phase increase with an increase of the forging pressure and temperature, and they are sensitive to temperature more than pressure within SLR.

  4. PB1-F2 influenza A virus protein adopts a beta-sheet conformation and forms amyloid fibers in membrane environments.

    Chevalier, Christophe; Al Bazzal, Ali; Vidic, Jasmina; Février, Vincent; Bourdieu, Christiane; Bouguyon, Edwige; Le Goffic, Ronan; Vautherot, Jean-François; Bernard, Julie; Moudjou, Mohammed; Noinville, Sylvie; Chich, Jean-François; Da Costa, Bruno; Rezaei, Human; Delmas, Bernard

    2010-04-23

    The influenza A virus PB1-F2 protein, encoded by an alternative reading frame in the PB1 polymerase gene, displays a high sequence polymorphism and is reported to contribute to viral pathogenesis in a sequence-specific manner. To gain insights into the functions of PB1-F2, the molecular structure of several PB1-F2 variants produced in Escherichia coli was investigated in different environments. Circular dichroism spectroscopy shows that all variants have a random coil secondary structure in aqueous solution. When incubated in trifluoroethanol polar solvent, all PB1-F2 variants adopt an alpha-helix-rich structure, whereas incubated in acetonitrile, a solvent of medium polarity mimicking the membrane environment, they display beta-sheet secondary structures. Incubated with asolectin liposomes and SDS micelles, PB1-F2 variants also acquire a beta-sheet structure. Dynamic light scattering revealed that the presence of beta-sheets is correlated with an oligomerization/aggregation of PB1-F2. Electron microscopy showed that PB1-F2 forms amorphous aggregates in acetonitrile. In contrast, at low concentrations of SDS, PB1-F2 variants exhibited various abilities to form fibers that were evidenced as amyloid fibers in a thioflavin T assay. Using a recombinant virus and its PB1-F2 knock-out mutant, we show that PB1-F2 also forms amyloid structures in infected cells. Functional membrane permeabilization assays revealed that the PB1-F2 variants can perforate membranes at nanomolar concentrations but with activities found to be sequence-dependent and not obviously correlated with their differential ability to form amyloid fibers. All of these observations suggest that PB1-F2 could be involved in physiological processes through different pathways, permeabilization of cellular membranes, and amyloid fiber formation.

  5. PB1-F2 Influenza A Virus Protein Adopts a β-Sheet Conformation and Forms Amyloid Fibers in Membrane Environments

    Chevalier, Christophe; Al Bazzal, Ali; Vidic, Jasmina; Février, Vincent; Bourdieu, Christiane; Bouguyon, Edwige; Le Goffic, Ronan; Vautherot, Jean-François; Bernard, Julie; Moudjou, Mohammed; Noinville, Sylvie; Chich, Jean-François; Da Costa, Bruno; Rezaei, Human; Delmas, Bernard

    2010-01-01

    The influenza A virus PB1-F2 protein, encoded by an alternative reading frame in the PB1 polymerase gene, displays a high sequence polymorphism and is reported to contribute to viral pathogenesis in a sequence-specific manner. To gain insights into the functions of PB1-F2, the molecular structure of several PB1-F2 variants produced in Escherichia coli was investigated in different environments. Circular dichroism spectroscopy shows that all variants have a random coil secondary structure in aqueous solution. When incubated in trifluoroethanol polar solvent, all PB1-F2 variants adopt an α-helix-rich structure, whereas incubated in acetonitrile, a solvent of medium polarity mimicking the membrane environment, they display β-sheet secondary structures. Incubated with asolectin liposomes and SDS micelles, PB1-F2 variants also acquire a β-sheet structure. Dynamic light scattering revealed that the presence of β-sheets is correlated with an oligomerization/aggregation of PB1-F2. Electron microscopy showed that PB1-F2 forms amorphous aggregates in acetonitrile. In contrast, at low concentrations of SDS, PB1-F2 variants exhibited various abilities to form fibers that were evidenced as amyloid fibers in a thioflavin T assay. Using a recombinant virus and its PB1-F2 knock-out mutant, we show that PB1-F2 also forms amyloid structures in infected cells. Functional membrane permeabilization assays revealed that the PB1-F2 variants can perforate membranes at nanomolar concentrations but with activities found to be sequence-dependent and not obviously correlated with their differential ability to form amyloid fibers. All of these observations suggest that PB1-F2 could be involved in physiological processes through different pathways, permeabilization of cellular membranes, and amyloid fiber formation. PMID:20172856

  6. Planning Through Incrementalism

    Lasserre, Ph.

    1974-01-01

    An incremental model of decisionmaking is discussed and compared with the Comprehensive Rational Approach. A model of reconciliation between the two approaches is proposed, and examples are given in the field of economic development and educational planning. (Author/DN)

  7. Deep Incremental Boosting

    Mosca, Alan; Magoulas, George D

    2017-01-01

    This paper introduces Deep Incremental Boosting, a new technique derived from AdaBoost, specifically adapted to work with Deep Learning methods, that reduces the required training time and improves generalisation. We draw inspiration from Transfer of Learning approaches to reduce the start-up time to training each incremental Ensemble member. We show a set of experiments that outlines some preliminary results on some common Deep Learning datasets and discuss the potential improvements Deep In...

  8. An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection

    Reeves, Katharine K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS 58, Cambridge, MA 02138 (United States); Freed, Michael S.; McKenzie, David E. [Montana State University, Bozeman, MT 59717 (United States); Savage, Sabrina L., E-mail: kreeves@cfa.harvard.edu [NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States)

    2017-02-10

    We perform a detailed analysis of the thermal structure of the region above the post-eruption arcade for a flare that occurred on 2011 October 22. During this event, a sheet of hot plasma is visible above the flare loops in the 131 Å bandpass of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory . Supra-arcade downflows (SADs) are observed traveling sunward through the post-eruption plasma sheet. We calculate differential emission measures using the AIA data and derive an emission measure weighted average temperature in the supra-arcade region. In areas where many SADs occur, the temperature of the supra-arcade plasma tends to increase, while in areas where no SADs are observed, the temperature tends to decrease. We calculate the plane-of-sky velocities in the supra-arcade plasma and use them to determine the potential heating due to adiabatic compression and viscous heating. Of the 13 SADs studied, 10 have noticeable signatures in both the adiabatic and the viscous terms. The adiabatic heating due to compression of plasma in front of the SADs is on the order of 0.1–0.2 MK/s, which is similar in magnitude to the estimated conductive cooling rate. This result supports the notion that SADs contribute locally to the heating of plasma in the supra-arcade region. We also find that in the region without SADs, the plasma cools at a rate that is slower than the estimated conductive cooling, indicating that additional heating mechanisms may act globally to keep the plasma temperature high.

  9. An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection

    Reeves, Katharine K.; Freed, Michael S.; McKenzie, David E.; Savage, Sabrina L.

    2017-01-01

    We perform a detailed analysis of the thermal structure of the region above the post-eruption arcade for a flare that occurred on 2011 October 22. During this event, a sheet of hot plasma is visible above the flare loops in the 131 Å bandpass of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory . Supra-arcade downflows (SADs) are observed traveling sunward through the post-eruption plasma sheet. We calculate differential emission measures using the AIA data and derive an emission measure weighted average temperature in the supra-arcade region. In areas where many SADs occur, the temperature of the supra-arcade plasma tends to increase, while in areas where no SADs are observed, the temperature tends to decrease. We calculate the plane-of-sky velocities in the supra-arcade plasma and use them to determine the potential heating due to adiabatic compression and viscous heating. Of the 13 SADs studied, 10 have noticeable signatures in both the adiabatic and the viscous terms. The adiabatic heating due to compression of plasma in front of the SADs is on the order of 0.1–0.2 MK/s, which is similar in magnitude to the estimated conductive cooling rate. This result supports the notion that SADs contribute locally to the heating of plasma in the supra-arcade region. We also find that in the region without SADs, the plasma cools at a rate that is slower than the estimated conductive cooling, indicating that additional heating mechanisms may act globally to keep the plasma temperature high.

  10. Hydro mechanical deep-drawing and high pressure sheet metal forming as forming technologies for the production of complex parts made of magnesium sheet metal AZ31B-0; Hydromechanisches Tiefziehen und Hochdruckblechumformung als Verfahren zur Herstellung komplexer Bauteile aus Magnesiumfeinblechen des Typs AZ31B-0

    Viehweger, B.; Richter, G.; Duering, M.; Karabet, A. [Lehrstuhlleiter, BTU Cottbus, Lehrstuhl Konstruktion und Fertigung, Konrad-Wachsmann Allee 1, 03046 Cottbus (Germany); Sviridov, A.; Hartmann, H.; Richter, U. [Forschungs- und Qualitaetszentrum Oderbruecke gGmbH Eisenhuettenstadt (Germany)

    2004-07-01

    Semi - finished sheet - metal products made of magnesium alloys such as AZ31B are known as better deformable at temperatures in the range of 175 C - 240 C. By means of hydroforming technologies, as there are hydro mechanical deep-drawing and high pressure sheet metal forming, the influence of different forming parameters on the forming results has been investigated. A more complex experimental geometry was deformed applying forming temperatures of 175 C, 200 C, 225 C and 240 C and accordingly adjusted forces of the blank holder. Concerning the applied forming - methods and experimental parameters the forming results have been evaluated and compared regarding the decrease of sheet thickness and the development of small radii. For some experimental parts, which have been deformed by means of high pressure sheet metal forming at temperatures of 175 C and 225 C, supplementary investigations have been carried out in order to determine the evolution of characteristic surface values in dependence on the forming operation. On the basis of these results practical recommendations for the limits of application of aforementioned forming technologies for AZ31B-0 magnesium sheet metal are given. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [German] Eine gute Umformbarkeit von Blechhalbzeugen aus Magnesiumknetlegierungen stellt sich bekanntlich bei Anwendung von Umformtemperaturen im Bereich von 175 C - 240 C ein. Anhand der wirkmedienbasierten Umformverfahren hydromechanisches Tiefziehen und Hochdruckblechumformung ist an handelsueblichen AZ31B-0 Feinblechen die Einstellung unterschiedlicher Umformparameter erprobt worden. Unter Verwendung von Umformtemperaturen von 175 C, 200 C, 225 C und 240 C und entsprechend angepassten Niederhalterdruecken ist eine praxisnahe Versuchsgeometrie ''Minihood'' ausgeformt worden. Im Hinblick auf angewendete Umformverfahren und Versuchsparameter wurde an den Versuchsbauteilen die Blechdickenabnahme und die

  11. The Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF): incremental validity in predicting early postoperative outcomes in spine surgery candidates.

    Marek, Ryan J; Block, Andrew R; Ben-Porath, Yossef S

    2015-03-01

    A substantial proportion of individuals who undergo surgical procedures to relieve spine pain continue to report significant pain and dysfunction after recovery. Psychopathology and patient expectations have been linked to poor results, leading to an increasing reliance on presurgical psychological screening (PPS) as part of the surgical diagnostic process. The original Minnesota Multiphasic Personality Inventory (MMPI; Hathaway & McKinley, 1943) and the MMPI-2 (Butcher, Graham, Ben-Porath, Tellegen, & Dahlstrom, 2001) were among the measures most commonly used in PPS evaluations and research. This study focuses on the newest version of the test, the MMPI-2-Restructured Form (MMPI-2-RF; Ben-Porath & Tellegen, 2008/2011; Tellegen & Ben-Porath, 2008/2011) as a predictor of outcomes for spine surgery candidates. Using a sample of 172 men and 210 women who underwent a PPS, we examined the ability of MMPI-2-RF scale scores to predict early surgical outcomes independent of other presurgical risk factors identified by other means, as well as patients' presurgical expectations. MMPI-2-RF results accounted for up to 11% of additional variance in measures of early postoperative functioning. MMPI-2-RF scales that assess for emotional/internalizing problems, specifically Demoralization, measures of somatoform dysfunction, and interpersonal problems contributed most to the prediction of diminished outcome. 2015 APA, all rights reserved

  12. Tribological evaluation of surface modified H13 tool steel in warm forming of Ti–6Al–4V titanium alloy sheet

    Wang Dan

    2014-08-01

    Full Text Available The H13 hot-working tool steel is widely used as die material in the warm forming of Ti–6Al–4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti–6Al–4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods (chromium plating, TiAlN coating, surface polishing and nitriding treatment were applied to the H13 surfaces. Taking the coefficient of friction (CoF and the wear degree as evaluation indicators, the high-temperature tribological behavior of the surface modified H13 steel was experimentally investigated under different tribological conditions. The results of this study indicate that the tribological properties of the TiAlN coating under dry friction condition are better than the others for a wide range of temperature (from room temperature to 500 °C, while there is little difference of tribological properties between different surface modifications under graphite lubricated condition, and the variation law of CoF with temperature under graphite lubricated is opposite to that under the dry friction.

  13. Laboratory setup for incremental forming at IPL

    Young, Dave; Andreasen, Jan Lasson

    and machining laboratories. A laboratory equipment was developed during spring 2004 with our Cincinatti CNC milling machine as basis. The first obstacle to overcome was to establish a possibility for running CNC programs larger than capacity of the memory in the CNC controller of the milling machine. A solution...... is a collection of the work done by Dave in cooperation with Lars P. Holmbæck, Jan L. Andreasen and Niels Bay during his 1 month stay here. The work has been concentrated on following subjects: 1. Design and construction of a rig for SPIF for our Cincinatti CNC milling machine 2. Establishment of methods...

  14. Analytic description of the frictionally engaged in-plane bending process incremental swivel bending (ISB)

    Frohn, Peter; Engel, Bernd; Groth, Sebastian

    2018-05-01

    Kinematic forming processes shape geometries by the process parameters to achieve a more universal process utilizations regarding geometric configurations. The kinematic forming process Incremental Swivel Bending (ISB) bends sheet metal strips or profiles in plane. The sequence for bending an arc increment is composed of the steps clamping, bending, force release and feed. The bending moment is frictionally engaged by two clamping units in a laterally adjustable bending pivot. A minimum clamping force hindering the material from slipping through the clamping units is a crucial criterion to achieve a well-defined incremental arc. Therefore, an analytic description of a singular bent increment is developed in this paper. The bending moment is calculated by the uniaxial stress distribution over the profiles' width depending on the bending pivot's position. By a Coulomb' based friction model, necessary clamping force is described in dependence of friction, offset, dimensions of the clamping tools and strip thickness as well as material parameters. Boundaries for the uniaxial stress calculation are given in dependence of friction, tools' dimensions and strip thickness. The results indicate that changing the bending pivot to an eccentric position significantly affects the process' bending moment and, hence, clamping force, which is given in dependence of yield stress and hardening exponent. FE simulations validate the model with satisfactory accordance.

  15. Giant seafloor craters formed by hydrate-controlled large-scale methane expulsion from the Arctic seafloor after ice sheet retreat

    Andreassen, K.; Hubbard, A.; Patton, H.; Vadakkepuliyambatta, S.; Winsborrow, M.; Plaza-Faverola, A. A.; Serov, P.

    2017-12-01

    Large-scale methane releases from thawing Arctic gas hydrates is a major concern, yet the processes and fluxes involved remain elusive. We present geophysical data indicating two contrasting processes of natural methane emissions from the seafloor of the northern Barents Sea, Polar North Atlantic. Abundant gas flares, acoustically imaged in the water column reveal slow, gradual release of methane bubbles, a process that is commonly documented from nearby areas, elsewhere in the Arctic and along continental margins worldwide. Conversely, giant craters across the study area indicate a very different process. We propose that these are blow-out craters, formed through large-scale, abrupt methane expulsion induced when gas hydrates destabilized after the Barents Sea Ice Sheet retreated from the area. The data reveal over 100 giant seafloor craters within an area of 440 km2. These are up to 1000 m in diameter, 30 m deep and with a semi-circular to elliptical shape. We also identified numerous large seafloor mounds, which we infer to have formed by the expansion of gas hydrate accumulations within the shallow subsurface, so-called gas hydrate pingos. These are up to 1100 m wide and 20 m high. Smaller craters and mounds < 200 m wide and with varying relief are abundant across the study site. The empirical observations and analyses are combined with numerical modelling of ice sheet, isostatic and gas hydrate evolution and indicate that during glaciation, natural gas migrating from underlying hydrocarbon reservoirs was stored as subglacial gas hydrates. On ice sheet retreat, methane from these hydrate reservoirs and underlying free gas built up and abruptly released, forming the giant mounds and craters observed in the study area today. Petroleum basins are abundant beneath formerly and presently glaciated regions. We infer that episodes of subglacial sequestration of gas hydrates and underlying free gas and subsequent abrupt expulsions were common and widespread throughout

  16. Role of Hydrophobic/Aromatic Residues on the Stability of Double-Wall β-Sheet Structures Formed by a Triblock Peptide.

    Ozgur, Beytullah; Sayar, Mehmet

    2017-04-27

    Bioinspired self-assembling peptides serve as powerful building blocks in the manufacturing of nanomaterials with tailored features. Because of their ease of synthesis, biocompatibility, and tunable activity, this emerging branch of biomolecules has become very popular. The triblock peptide architecture designed by the Hartgerink group is a versatile system that allows control over its assembly and has been shown to demonstrate tunable bioactivity. Three main forces, Coulomb repulsion, hydrogen bonding and hydrophobicity act together to guide the triblock peptides' assembly into one-dimensional objects and hydrogels. It was shown previously that both the nanofiber morphology (e.g., intersheet spacing, formation of antiparallel/parallel β-sheets) and hydrogel rheology strictly depend on the choice of the core residue where the triblock peptide fibers with aromatic cores in general form shorter fibers and yield poor hydrogels with respect to the ones with aliphatic cores. However, an elaborate understanding of the molecular reasons behind these changes remained unclear. In this study, by using carefully designed computer based free energy calculations, we analyzed the influence of the core residue on the formation of double-wall fibers and single-wall β-sheets. Our results demonstrate that the aromatic substitution impairs the fiber cores and this impairment is mainly associated with a reduced hydrophobic character of the aromatic side chains. Such weakening is most obvious in tryptophan containing peptides where the fiber core absorbs a significant amount of water. We also show that the ability of tyrosine to form side chain hydrogen bonds plays an indispensable role in the fiber stability. As opposed to the impairment of the fiber cores, single-wall β-sheets with aromatic faces become more stable compared to the ones with aliphatic faces suggesting that the choice of the core residue can also affect the underlying assembly mechanism. We also provide an in

  17. Quantum independent increment processes

    Franz, Uwe

    2005-01-01

    This volume is the first of two volumes containing the revised and completed notes lectures given at the school "Quantum Independent Increment Processes: Structure and Applications to Physics". This school was held at the Alfried-Krupp-Wissenschaftskolleg in Greifswald during the period March 9 – 22, 2003, and supported by the Volkswagen Foundation. The school gave an introduction to current research on quantum independent increment processes aimed at graduate students and non-specialists working in classical and quantum probability, operator algebras, and mathematical physics. The present first volume contains the following lectures: "Lévy Processes in Euclidean Spaces and Groups" by David Applebaum, "Locally Compact Quantum Groups" by Johan Kustermans, "Quantum Stochastic Analysis" by J. Martin Lindsay, and "Dilations, Cocycles and Product Systems" by B.V. Rajarama Bhat.

  18. Quantum independent increment processes

    Franz, Uwe

    2006-01-01

    This is the second of two volumes containing the revised and completed notes of lectures given at the school "Quantum Independent Increment Processes: Structure and Applications to Physics". This school was held at the Alfried-Krupp-Wissenschaftskolleg in Greifswald in March, 2003, and supported by the Volkswagen Foundation. The school gave an introduction to current research on quantum independent increment processes aimed at graduate students and non-specialists working in classical and quantum probability, operator algebras, and mathematical physics. The present second volume contains the following lectures: "Random Walks on Finite Quantum Groups" by Uwe Franz and Rolf Gohm, "Quantum Markov Processes and Applications in Physics" by Burkhard Kümmerer, Classical and Free Infinite Divisibility and Lévy Processes" by Ole E. Barndorff-Nielsen, Steen Thorbjornsen, and "Lévy Processes on Quantum Groups and Dual Groups" by Uwe Franz.

  19. Efficient incremental relaying

    Fareed, Muhammad Mehboob

    2013-07-01

    We propose a novel relaying scheme which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from destination. Our scheme capitalizes on the fact that relaying is only required when direct transmission suffers deep fading. We calculate the packet error rate for the proposed efficient incremental relaying scheme with both amplify and forward and decode and forward relaying. Numerical results are also presented to verify their analytical counterparts. © 2013 IEEE.

  20. Energy-switching potential energy surface for the water molecule revisited: A highly accurate singled-sheeted form.

    Galvão, B R L; Rodrigues, S P J; Varandas, A J C

    2008-07-28

    A global ab initio potential energy surface is proposed for the water molecule by energy-switching/merging a highly accurate isotope-dependent local potential function reported by Polyansky et al. [Science 299, 539 (2003)] with a global form of the many-body expansion type suitably adapted to account explicitly for the dynamical correlation and parametrized from extensive accurate multireference configuration interaction energies extrapolated to the complete basis set limit. The new function mimics also the complicated Sigma/Pi crossing that arises at linear geometries of the water molecule.

  1. Experimental Research on the Impact of Thin-Wall Ratio and the Fillet Radius of Forming Roller on the Limiting Spinning Ratio of AMS 5504 Sheets

    Kut S.

    2017-12-01

    Full Text Available Results of experimental investigations of metal spinning process of AMS 5504 sheets. cylindrical drawpieces with use of discs-shaped sheet with various diameter and thickness were shown in this work. Tests were performed on two roller metal spinning machine of a vertical axis Leifeld SFC 800 V500.

  2. Numerical analysis of tailored sheets to improve the quality of components made by SPIF

    Gagliardi, Francesco; Ambrogio, Giuseppina; Cozza, Anna; Pulice, Diego; Filice, Luigino

    2018-05-01

    In this paper, the authors pointed out a study on the profitable combination of forming techniques. More in detail, the attention has been put on the combination of the single point incremental forming (SPIF) and, generally, speaking, of an additional process that can lead to a material thickening on the initial blank considering the local thinning which the sheets undergo at. Focalizing the attention of the research on the excessive thinning of parts made by SPIF, a hybrid approach can be thought as a viable solution to reduce the not homogeneous thickness distribution of the sheet. In fact, the basic idea is to work on a blank previously modified by a deformation step performed, for instance, by forming, additive or subtractive processes. To evaluate the effectiveness of this hybrid solution, a FE numerical model has been defined to analyze the thickness variation on tailored sheets incrementally formed optimizing the material distribution according to the shape to be manufactured. Simulations based on the explicit formulation have been set up for the model implementation. The mechanical properties of the sheet material have been taken in literature and a frustum of cone as benchmark profile has been considered for the performed analysis. The outcomes of numerical model have been evaluated in terms of both maximum thinning and final thickness distribution. The feasibility of the proposed approach will be deeply detailed in the paper.

  3. Parameter optimization and stretch enhancement of AISI 316 sheet using rapid prototyping technique

    Moayedfar, M.; Rani, A. M.; Hanaei, H.; Ahmad, A.; Tale, A.

    2017-10-01

    Incremental sheet forming is a flexible manufacturing process which uses the indenter point-to-point force to shape the sheet metal workpiece into manufactured parts in batch production series. However, the problem sometimes arising from this process is the low plastic point in the stress-strain diagram of the material which leads the low stretching amount before ultra-tensile strain point. Hence, a set of experiments is designed to find the optimum forming parameters in this process for optimum sheet thickness distribution while both sides of the sheet are considered for the surface quality improvement. A five-axis high-speed CNC milling machine is employed to deliver the proper motion based on the programming system while the clamping system for holding the sheet metal was a blank mould. Finally, an electron microscope and roughness machine are utilized to evaluate the surface structure of final parts, illustrate any defect may cause during the forming process and examine the roughness of the final part surface accordingly. The best interaction between parameters is obtained with the optimum values which lead the maximum sheet thickness distribution of 4.211e-01 logarithmic elongation when the depth was 24mm with respect to the design. This study demonstrates that this rapid forming method offers an alternative solution for surface quality improvement of 65% avoiding the low probability of cracks and low probability of crystal structure changes.

  4. Friction in sheet metal forming

    Wiklund, D.; Liljebgren, M.; Berglund, J.

    2010-01-01

    and calls for functional tool surfaces that are durable in these severe tribological conditions. In this study the influence of tool surface topography on friction has been investigated. The frictional response was studied in a Bending Under Tension test. The results did show that a low frictional response...

  5. The antigen-binding fragment of human gamma immunoglobulin prevents amyloid β-peptide folding into β-sheet to form oligomers

    Valls-Comamala, Victòria; Guivernau, Biuse; Bonet, Jaume; Puig, Marta; Perálvarez-Marín, Alex; Palomer, Ernest; Fernàndez-Busquets, Xavier; Altafaj, Xavier; Tajes, Marta; Puig-Pijoan, Albert; Vicente, Rubén; Oliva, Baldomero; Muñoz, Francisco J.

    2017-01-01

    The amyloid beta-peptide (Aβ) plays a leading role in Alzheimer's disease (AD) physiopathology. Even though monomeric forms of Aβ are harmless to cells, Aβ can aggregate into β-sheet oligomers and fibrils, which are both neurotoxic. Therefore, one of the main therapeutic approaches to cure or delay AD onset and progression is targeting Aβ aggregation. In the present study, we show that a pool of human gamma immunoglobulins (IgG) protected cortical neurons from the challenge with Aβ oligomers, as assayed by MTT reduction, caspase-3 activation and cytoskeleton integrity. In addition, we report the inhibitory effect of IgG on Aβ aggregation, as shown by Thioflavin T assay, size exclusion chromatography and atomic force microscopy. Similar results were obtained with Palivizumab, a human anti-sincitial virus antibody. In order to dissect the important domains, we cleaved the pool of human IgG with papain to obtain Fab and Fc fragments. Using these cleaved fragments, we functionally identified Fab as the immunoglobulin fragment inhibiting Aβ aggregation, a result that was further confirmed by an in silico structural model. Interestingly, bioinformatic tools show a highly conserved structure able to bind amyloid in the Fab region. Overall, our data strongly support the inhibitory effect of human IgG on Aβ aggregation and its neuroprotective role. PMID:28467807

  6. The Cognitive Underpinnings of Incremental Rehearsal

    Varma, Sashank; Schleisman, Katrina B.

    2014-01-01

    Incremental rehearsal (IR) is a flashcard technique that has been developed and evaluated by school psychologists. We discuss potential learning and memory effects from cognitive psychology that may explain the observed superiority of IR over other flashcard techniques. First, we propose that IR is a form of "spaced practice" that…

  7. El conformado incremental como nueva técnica de prototipado rápido

    Miguel Ángel Peydró Rasero

    2012-08-01

    Full Text Available Various industrial sectors (aerospace, automotive, use forming processes nowadays to produce components of complex shapes from sheet metal. Traditional processes that use arrays are suitable for the production of large volumes of parts, but are not profitable for small series (special vehicles, prototypes, .... Incremental forming is a different process, intelligent and flexible, which presents itself as an alternative to traditional forming methods. This process is based on Rapid Manufacturing methodologies, and greatly reduces tooling costs, since it only requires a simple tool support. It’s well suited to the manufacture of prototypes and small series by low production costs, but the time required to manufacture a part, typically several hours, which makes it impractical for longer runs.

  8. Single Point Incremental Forming and Multi-Stage Incremental Forming on Aluminium Alloy 1050

    Suriyaprakan, Premika

    As piroxenas sao um vasto grupo de silicatos minerais encontrados em muitas rochas igneas e metamorficas. Na sua forma mais simples, estes silicatos sao constituidas por cadeias de SiO3 ligando grupos tetrahedricos de SiO4. A formula quimica geral das piroxenas e M2M1T2O6, onde M2 se refere a catioes geralmente em uma coordenacao octaedrica distorcida (Mg2+, Fe2+, Mn2+, Li+, Ca2+, Na+), M1 refere-se a catioes numa coordenacao octaedrica regular (Al3+, Fe3+, Ti4+, Cr3+, V3+, Ti3+, Zr4+, Sc3+, Zn2+, Mg2+, Fe2+, Mn2+), e T a catioes em coordenacao tetrahedrica (Si4+, Al3+, Fe3+). As piroxenas com estrutura monoclinica sao designadas de clinopiroxenes. A estabilidade das clinopyroxenes num espectro de composicoes quimicas amplo, em conjugacao com a possibilidade de ajustar as suas propriedades fisicas e quimicas e a durabilidade quimica, tem gerado um interesse mundial devido a suas aplicacoes em ciencia e tecnologia de materiais. Este trabalho trata do desenvolvimento de vidros e de vitro-cerâmicos baseadas de clinopiroxenas para aplicacoes funcionais. O estudo teve objectivos cientificos e tecnologicos; nomeadamente, adquirir conhecimentos fundamentais sobre a formacao de fases cristalinas e solucoes solidas em determinados sistemas vitro-cerâmicos, e avaliar a viabilidade de aplicacao dos novos materiais em diferentes areas tecnologicas, com especial enfase sobre a selagem em celulas de combustivel de oxido solido (SOFC). Com este intuito, prepararam-se varios vidros e materiais vitro-cerâmicos ao longo das juntas Enstatite (MgSiO3) - diopsidio (CaMgSi2O6) e diopsidio (CaMgSi2O6) - Ca - Tschermak (CaAlSi2O6), os quais foram caracterizados atraves de um vasto leque de tecnicas. Todos os vidros foram preparados por fusao-arrefecimento enquanto os vitro-cerâmicos foram obtidos quer por sinterizacao e cristalizacao de fritas, quer por nucleacao e cristalizacao de vidros monoliticos. Estudaram-se ainda os efeitos de varias substituicoes ionicas em composicoes de diopsidio contendo Al na estrutura, sinterizacao e no comportamento durante a cristalizacao de vidros e nas propriedades dos materiais vitro-cerâmicos, com relevância para a sua aplicacao como selantes em SOFC. Verificou-se que Foi observado que os vidros/vitro-cerâmicos a base de enstatite nao apresentavam as caracteristicas necessarias para serem usados como materiais selantes em SOFC, enquanto as melhores propriedades apresentadas pelos vitro-cerâmicos a base de diopsidio qualificaram-nos para futuros estudos neste tipo de aplicacoes. Para alem de investigar a adequacao dos vitro-cerâmicos a base de clinopyroxene como selantes, esta tese tem tambem como objetivo estudar a influencia dos agentes de nucleacao na nucleacao em volume dos vitro-cerâmicos resultantes a base de diopsidio, de modo a qualifica-los como potenciais materiais hopedeiros de residuos nucleares radioactivos.

  9. Legislative Bargaining and Incremental Budgeting

    Dhammika Dharmapala

    2002-01-01

    The notion of 'incrementalism', formulated by Aaron Wildavsky in the 1960's, has been extremely influential in the public budgeting literature. In essence, it entails the claim that legislators engaged in budgetary policymaking accept past allocations, and decide only on the allocation of increments to revenue. Wildavsky explained incrementalism with reference to the cognitive limitations of lawmakers and their desire to reduce conflict. This paper uses a legislative bargaining framework to u...

  10. Radiation protecting sheet

    Makiguchi, Hiroshi.

    1989-01-01

    As protection sheets used in radioactivity administration areas, a thermoplastic polyurethane composition sheet with a thickness of less 0.5 mm, solid content (ash) of less than 5% and a shore D hardness of less than 60 is used. A composite sheet with thickness of less than 0.5 mm laminated or coated with such a thermoplastic polyurethane composition as a surface layer and the thermoplastic polyurethane composition sheet applied with secondary fabrication are used. This can satisfy all of the required properties, such as draping property, abrasion resistance, high breaking strength, necking resistance, endurance strength, as well as chemical resistance and easy burnability in burning furnace. Further, by forming uneveness on the surface by means of embossing, etc. safety problems such as slippage during operation and walking can be overcome. (T.M.)

  11. 76 FR 73475 - Immigration Benefits Business Transformation, Increment I; Correction

    2011-11-29

    ... Benefits Business Transformation, Increment I, 76 FR 53764 (Aug. 29, 2011). The final rule removed form... [CIS No. 2481-09; Docket No. USCIS-2009-0022] RIN 1615-AB83 Immigration Benefits Business Transformation, Increment I; Correction AGENCY: U.S. Citizenship and Immigration Services, DHS. ACTION: Final...

  12. Remaining Sites Verification Package for the 100-D-2 Lead Sheeting Waste Site. Attachment to Waste Site Reclassification Form 2007-030

    Dittmer, L.M.

    2008-01-01

    The 100-D-2 Lead Sheeting waste site was located approximately 50 m southwest of the 185-D Building and approximately 16 m north of the east/west oriented road. The site consisted of a lead sheet covering a concrete pad. In accordance with this evaluation, the verification sampling results support a reclassification of this site to Interim Closed Out. The results of verification sampling show that residual contaminant concentrations do not preclude any future uses and allow for unrestricted use of shallow zone soils. The results also demonstrate that residual contaminant concentrations are protective of groundwater and the Columbia River

  13. Incremental Volumetric Remapping Method: Analysis and Error Evaluation

    Baptista, A. J.; Oliveira, M. C.; Rodrigues, D. M.; Menezes, L. F.; Alves, J. L.

    2007-01-01

    In this paper the error associated with the remapping problem is analyzed. A range of numerical results that assess the performance of three different remapping strategies, applied to FE meshes that typically are used in sheet metal forming simulation, are evaluated. One of the selected strategies is the previously presented Incremental Volumetric Remapping method (IVR), which was implemented in the in-house code DD3TRIM. The IVR method fundaments consists on the premise that state variables in all points associated to a Gauss volume of a given element are equal to the state variable quantities placed in the correspondent Gauss point. Hence, given a typical remapping procedure between a donor and a target mesh, the variables to be associated to a target Gauss volume (and point) are determined by a weighted average. The weight function is the Gauss volume percentage of each donor element that is located inside the target Gauss volume. The calculus of the intersecting volumes between the donor and target Gauss volumes is attained incrementally, for each target Gauss volume, by means of a discrete approach. The other two remapping strategies selected are based in the interpolation/extrapolation of variables by using the finite element shape functions or moving least square interpolants. The performance of the three different remapping strategies is address with two tests. The first remapping test was taken from a literature work. The test consists in remapping successively a rotating symmetrical mesh, throughout N increments, in an angular span of 90 deg. The second remapping error evaluation test consists of remapping an irregular element shape target mesh from a given regular element shape donor mesh and proceed with the inverse operation. In this second test the computation effort is also measured. The results showed that the error level associated to IVR can be very low and with a stable evolution along the number of remapping procedures when compared with the

  14. FEM Simulation of Incremental Shear

    Rosochowski, Andrzej; Olejnik, Lech

    2007-01-01

    A popular way of producing ultrafine grained metals on a laboratory scale is severe plastic deformation. This paper introduces a new severe plastic deformation process of incremental shear. A finite element method simulation is carried out for various tool geometries and process kinematics. It has been established that for the successful realisation of the process the inner radius of the channel as well as the feeding increment should be approximately 30% of the billet thickness. The angle at which the reciprocating die works the material can be 30 deg. . When compared to equal channel angular pressing, incremental shear shows basic similarities in the mode of material flow and a few technological advantages which make it an attractive alternative to the known severe plastic deformation processes. The most promising characteristic of incremental shear is the possibility of processing very long billets in a continuous way which makes the process more industrially relevant

  15. FDTD Stability: Critical Time Increment

    Z. Skvor; L. Pauk

    2003-01-01

    A new approach suitable for determination of the maximal stable time increment for the Finite-Difference Time-Domain (FDTD) algorithm in common curvilinear coordinates, for general mesh shapes and certain types of boundaries is presented. The maximal time increment corresponds to a characteristic value of a Helmholz equation that is solved by a finite-difference (FD) method. If this method uses exactly the same discretization as the given FDTD method (same mesh, boundary conditions, order of ...

  16. Implementing Kernel Methods Incrementally by Incremental Nonlinear Projection Trick.

    Kwak, Nojun

    2016-05-20

    Recently, the nonlinear projection trick (NPT) was introduced enabling direct computation of coordinates of samples in a reproducing kernel Hilbert space. With NPT, any machine learning algorithm can be extended to a kernel version without relying on the so called kernel trick. However, NPT is inherently difficult to be implemented incrementally because an ever increasing kernel matrix should be treated as additional training samples are introduced. In this paper, an incremental version of the NPT (INPT) is proposed based on the observation that the centerization step in NPT is unnecessary. Because the proposed INPT does not change the coordinates of the old data, the coordinates obtained by INPT can directly be used in any incremental methods to implement a kernel version of the incremental methods. The effectiveness of the INPT is shown by applying it to implement incremental versions of kernel methods such as, kernel singular value decomposition, kernel principal component analysis, and kernel discriminant analysis which are utilized for problems of kernel matrix reconstruction, letter classification, and face image retrieval, respectively.

  17. Disintegration of liquid sheets

    Mansour, Adel; Chigier, Norman

    1990-01-01

    The development, stability, and disintegration of liquid sheets issuing from a two-dimensional air-assisted nozzle is studied. Detailed measurements of mean drop size and velocity are made using a phase Doppler particle analyzer. Without air flow the liquid sheet converges toward the axis as a result of surface tension forces. With airflow a quasi-two-dimensional expanding spray is formed. The air flow causes small variations in sheet thickness to develop into major disturbances with the result that disruption starts before the formation of the main break-up region. In the two-dimensional variable geometry air-blast atomizer, it is shown that the air flow is responsible for the formation of large, ordered, and small chaotic 'cell' structures.

  18. A Modified Johnson-Cook Model for Sheet Metal Forming at Elevated Temperatures and Its Application for Cooled Stress-Strain Curve and Spring-Back Prediction

    Duc-Toan, Nguyen; Tien-Long, Banh; Young-Suk, Kim; Dong-Won, Jung

    2011-01-01

    In this study, a modified Johnson-Cook (J-C) model and an innovated method to determine (J-C) material parameters are proposed to predict more correctly stress-strain curve for tensile tests in elevated temperatures. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. As the first verification, an FEM tensile test simulation based on the isotropic hardening model for boron sheet steel at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code, and compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation of cooling process. The modified (J-C) model showed the good agreement between the simulation results and the corresponding experiments. The second investigation was applied for V-bending spring-back prediction of magnesium alloy sheets at elevated temperatures. Here, the combination of proposed J-C model with modified hardening law considering the unusual plastic behaviour for magnesium alloy sheet was adopted for FEM simulation of V-bending spring-back prediction and shown the good comparability with corresponding experiments.

  19. On the possible eigenoscillations of neutral sheets

    Almeida, W.A.; Costa, J.M. da; Aruquipa, E.G.; Sudano, J.P.

    1974-12-01

    A neutral sheet model with hyperbolic tangent equilibrium magnetic field and hyperbolic square secant density profiles is considered. It is shown that the equation for small oscillations takes the form of an eigenvalue oscillation problem. Computed eigenfrequencies of the geomagnetic neutral sheet were found to be in the range of the resonant frequencies of the geomagnetic plasma sheet computed by other authors

  20. Incremental Visualizer for Visible Objects

    Bukauskas, Linas; Bøhlen, Michael Hanspeter

    This paper discusses the integration of database back-end and visualizer front-end into a one tightly coupled system. The main aim which we achieve is to reduce the data pipeline from database to visualization by using incremental data extraction of visible objects in a fly-through scenarios. We...... also argue that passing only relevant data from the database will substantially reduce the overall load of the visualization system. We propose the system Incremental Visualizer for Visible Objects (IVVO) which considers visible objects and enables incremental visualization along the observer movement...... path. IVVO is the novel solution which allows data to be visualized and loaded on the fly from the database and which regards visibilities of objects. We run a set of experiments to convince that IVVO is feasible in terms of I/O operations and CPU load. We consider the example of data which uses...

  1. Plasma dynamics in current sheets

    Bogdanov, S.Yu.; Drejden, G.V.; Kirij, N.P.; AN SSSR, Leningrad

    1992-01-01

    Plasma dynamics in successive stages of current sheet evolution is investigated on the base of analysis of time-spatial variations of electron density and electrodynamic force fields. Current sheet formation is realized in a two-dimensional magnetic field with zero line under the action of relatively small initial disturbances (linear regimes). It is established that in the limits of the formed sheet is concentrated dense (N e ∼= 10 16 cm -3 ) (T i ≥ 100 eV, bar-Z i ≥ 2) hot pressure of which is balanced by the magnetic action of electrodynamic forces is carried out both plasma compression in the sheet limits and the acceleration along the sheet surface from a middle to narrow side edges

  2. Incremental Trust in Grid Computing

    Brinkløv, Michael Hvalsøe; Sharp, Robin

    2007-01-01

    This paper describes a comparative simulation study of some incremental trust and reputation algorithms for handling behavioural trust in large distributed systems. Two types of reputation algorithm (based on discrete and Bayesian evaluation of ratings) and two ways of combining direct trust and ...... of Grid computing systems....

  3. Convergent systems vs. incremental stability

    Rüffer, B.S.; Wouw, van de N.; Mueller, M.

    2013-01-01

    Two similar stability notions are considered; one is the long established notion of convergent systems, the other is the younger notion of incremental stability. Both notions require that any two solutions of a system converge to each other. Yet these stability concepts are different, in the sense

  4. Conformational Effects through Hydrogen Bonding in a Constrained γ-Peptide Template: From Intraresidue Seven-Membered Rings to a Gel-Forming Sheet Structure.

    Awada, Hawraà; Grison, Claire M; Charnay-Pouget, Florence; Baltaze, Jean-Pierre; Brisset, François; Guillot, Régis; Robin, Sylvie; Hachem, Ali; Jaber, Nada; Naoufal, Daoud; Yazbeck, Ogaritte; Aitken, David J

    2017-05-05

    A series of three short oligomers (di-, tri-, and tetramers) of cis-2-(aminomethyl)cyclobutane carboxylic acid, a γ-amino acid featuring a cyclobutane ring constraint, were prepared, and their conformational behavior was examined spectroscopically and by molecular modeling. In dilute solutions, these peptides showed a number of low-energy conformers, including ribbonlike structures pleated around a rarely observed series of intramolecular seven-membered hydrogen bonds. In more concentrated solutions, these interactions defer to an organized supramolecular assembly, leading to thermoreversible organogel formation notably for the tripeptide, which produced fibrillar xerogels. In the solid state, the dipeptide adopted a fully extended conformation featuring a one-dimensional network of intermolecularly H-bonded molecules stacked in an antiparallel sheet alignment. This work provides unique insight into the interplay between inter- and intramolecular H-bonded conformer topologies for the same peptide template.

  5. Porous honeycomb structures formed from interconnected MnO2 sheets on CNT-coated substrates for flexible all-solid-state supercapacitors

    Ko, Wen-Yin; Chen, You-Feng; Lu, Ke-Ming; Lin, Kuan-Jiuh

    2016-01-01

    The use of lightweight and easily-fabricated MnO2/carbon nanotube (CNT)-based flexible networks as binder-free electrodes and a polyvinyl alcohol/H2SO4 electrolyte for the formation of stretchable solid-state supercapacitors was examined. The active electrodes were fabricated from 3D honeycomb porous MnO2 assembled from cross-walled and interconnected sheet-architectural MnO2 on CNT-based plastic substrates (denoted as honeycomb MnO2/CNT textiles).These substrates were fabricated through a simple two-step procedure involving the coating of multi-walled carbon nanotubes (MWCNTs) onto commercial textiles by a dipping-drying process and subsequent electrodeposition of the interconnected MnO2 sheets onto the MWCNT-coated textile. With such unique MnO2 architectures integrated onto CNT flexible films, good performance was achieved with a specific capacitance of 324 F/g at 0.5 A/g. A maximum energy density of 7.2 Wh/kg and a power density as high as 3.3 kW/kg were exhibited by the honeycomb MnO2/CNT network device, which is comparable to the performance of other carbon-based and metal oxide/carbon-based solid-state supercapacitor devices. Specifically, the long-term cycling stability of this material is excellent, with almost no loss of its initial capacitance and good Coulombic efficiency of 82% after 5000 cycles. These impressive results identify these materials as a promising candidate for use in environmentally friendly, low-cost, and high-performance flexible energy-storage devices. PMID:26726724

  6. Process for the production of a pressure-sensitive carbonless copy sheet using microcapsules formed in situ in a radiation curable binder

    Lee, Y.S.; Shackle, D.R.

    1978-01-01

    A process is provided for the production of a coating composition containing microcapsules having a hydrophilic core for use in the manufacture of pressure-sensitive carbonless transfer papers comprising the following steps. A hydrophilic emulsion component is prepared by dispersing at least one chromogenic material being soluble in the hydrophilic liquid. A hydrophobic emulsion component is prepared by dispersing an emulsifier in a radiation curable hydrophobic liquid. A first wall-forming material and a second wall-forming material are added to the hydrophobic emulsion component, with mixing. The first and second wall-forming materials are soluble in the hydrophobic emulsion component, and the first wall-forming material is reactive with the second wall-forming material to form a polymeric capsule wall. The resultant polymeric capsule wall is substantially insoluble in the hydrophilic and the hydrophobic emulsion components. The hydrophobic emulsion component is mixed together with the hydrophilic emulsion component to form an emulsion containing droplets of the hydrophilic emulsion component dispersed in the hydrophobic emulsion component. Mixing is maintained for a period of time sufficient to allow the first and second wall-forming materials to react to form a dispersion of microcapsules in the hydrophobic emulsion component. The formed microcapsules have capsule walls substantially impermeable to the hydrophobic and the hydrophilic emulsion components. Pressure-sensitive carbonless transfer paper may be produced by applying the despersion of the microcapsules prepared as above to a substrate,and curing the dispersion by subjecting the dispersion on the substrate to radiation for a period of time sufficient to cure the radiation curable hydrophobic liquid, thereby producing a tack-free, resinous film on the substrate

  7. Molding cork sheets to complex shapes

    Sharpe, M. H.; Simpson, W. G.; Walker, H. M.

    1977-01-01

    Partially cured cork sheet is easily formed to complex shapes and then final-cured. Temperature and pressure levels required for process depend upon resin system used and final density and strength desired. Sheet can be bonded to surface during final cure, or can be first-formed in mold and bonded to surface in separate step.

  8. Chlamydia - CDC Fact Sheet

    ... Archive STDs Home Page Bacterial Vaginosis (BV) Chlamydia Gonorrhea Genital Herpes Hepatitis HIV/AIDS & STDs Human Papillomavirus ( ... sheet Pelvic Inflammatory Disease (PID) – CDC fact sheet Gonorrhea – CDC fact sheet STDs Home Page Bacterial Vaginosis ( ...

  9. Experimental formability analysis of bondal sandwich sheet

    Kami, Abdolvahed; Banabic, Dorel

    2018-05-01

    Metal/polymer/metal sandwich sheets have recently attracted the interests of industries like automotive industry. These sandwich sheets have superior properties over single-layer metallic sheets including good sound and vibration damping and light weight. However, the formability of these sandwich sheets should be enhanced which requires more research. In this paper, the formability of Bondal sheet (DC06/viscoelastic polymer/DC06 sandwich sheet) was studied through different types of experiments. The mechanical properties of Bondal were determined by uniaxial tensile tests. Hemispherical punch stretching and hydraulic bulge tests were carried out to determine the forming limit diagram (FLD) of Bondal. Furthermore, cylindrical and square cup drawing tests were performed in dry and oil lubricated conditions. These tests were conducted at different blank holding forces (BHFs). An interesting observation about Bondal sheet deep drawing was obtaining of higher drawing depths at dry condition in comparison with oil-lubricated condition.

  10. GASN sheets

    2013-12-01

    This document gathers around 50 detailed sheets which describe and present various aspects, data and information related to the nuclear sector or, more generally to energy. The following items are addressed: natural and artificial radioactive environment, evolution of energy needs in the world, radioactive wastes, which energy for France tomorrow, the consequences in France of the Chernobyl accident, ammunitions containing depleted uranium, processing and recycling of used nuclear fuel, transport of radioactive materials, seismic risk for the basic nuclear installations, radon, the precautionary principle, the issue of low doses, the EPR, the greenhouse effect, the Oklo nuclear reactors, ITER on the way towards fusion reactors, simulation and nuclear deterrence, crisis management in the nuclear field, does nuclear research put a break on the development of renewable energies by monopolizing funding, nuclear safety and security, the plutonium, generation IV reactors, comparison of different modes of electricity production, medical exposure to ionizing radiations, the control of nuclear activities, food preservation by ionization, photovoltaic solar collectors, the Polonium 210, the dismantling of nuclear installations, wind energy, desalination and nuclear reactors, from non-communication to transparency about nuclear safety, the Jules Horowitz reactor, CO 2 capture and storage, hydrogen, solar energy, the radium, the subcontractors of maintenance of the nuclear fleet, biomass, internal radio-contamination, epidemiological studies, submarine nuclear propulsion, sea energy, the Three Mile Island accident, the Chernobyl accident, the Fukushima accident, the nuclear after Fukushima

  11. Optimal swimming of a sheet.

    Montenegro-Johnson, Thomas D; Lauga, Eric

    2014-06-01

    Propulsion at microscopic scales is often achieved through propagating traveling waves along hairlike organelles called flagella. Taylor's two-dimensional swimming sheet model is frequently used to provide insight into problems of flagellar propulsion. We derive numerically the large-amplitude wave form of the two-dimensional swimming sheet that yields optimum hydrodynamic efficiency: the ratio of the squared swimming speed to the rate-of-working of the sheet against the fluid. Using the boundary element method, we show that the optimal wave form is a front-back symmetric regularized cusp that is 25% more efficient than the optimal sine wave. This optimal two-dimensional shape is smooth, qualitatively different from the kinked form of Lighthill's optimal three-dimensional flagellum, not predicted by small-amplitude theory, and different from the smooth circular-arc-like shape of active elastic filaments.

  12. Unmanned Maritime Systems Incremental Acquisition Approach

    2016-12-01

    REPORT TYPE AND DATES COVERED MBA professional report 4. TITLE AND SUBTITLE UNMANNED MARITIME SYSTEMS INCREMENTAL ACQUISITION APPROACH 5. FUNDING...Approved for public release. Distribution is unlimited. UNMANNED MARITIME SYSTEMS INCREMENTAL ACQUISITION APPROACH Thomas Driscoll, Lieutenant...UNMANNED MARITIME SYSTEMS INCREMENTAL ACQUISITION APPROACH ABSTRACT The purpose of this MBA report is to explore and understand the issues

  13. Googling your hand hygiene data: Using Google Forms, Google Sheets, and R to collect and automate analysis of hand hygiene compliance monitoring.

    Wiemken, Timothy L; Furmanek, Stephen P; Mattingly, William A; Haas, Janet; Ramirez, Julio A; Carrico, Ruth M

    2018-06-01

    Hand hygiene is one of the most important interventions in the quest to eliminate healthcare-associated infections, and rates in healthcare facilities are markedly low. Since hand hygiene observation and feedback are critical to improve adherence, we created an easy-to-use, platform-independent hand hygiene data collection process and an automated, on-demand reporting engine. A 3-step approach was used for this project: 1) creation of a data collection form using Google Forms, 2) transfer of data from the form to a spreadsheet using Google Spreadsheets, and 3) creation of an automated, cloud-based analytics platform for report generation using R and RStudio Shiny software. A video tutorial of all steps in the creation and use of this free tool can be found on our YouTube channel: https://www.youtube.com/watch?v=uFatMR1rXqU&t. The on-demand reporting tool can be accessed at: https://crsp.louisville.edu/shiny/handhygiene. This data collection and automated analytics engine provides an easy-to-use environment for evaluating hand hygiene data; it also provides rapid feedback to healthcare workers. By reducing some of the data management workload required of the infection preventionist, more focused interventions may be instituted to increase global hand hygiene rates and reduce infection. Copyright © 2018 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  14. Lubricant Film Breakdown and Material Pick-Up in Sheet Forming of Advanced High Strength Steels and Stainless Steels when Using Environmental Friendly Lubricants

    Ceron, Ermanno; Olsson, M.; Bay, Niels

    2014-01-01

    chemically with the tool and workpiece material forming thin films, which adhere strongly to the surfaces and reduce the tendency to metal-metal contact and material pick-up. Production tests of new, environmentally benign tribo-systems are, however, costly and laboratory tests are preferred as a preliminary...... the tribological performance, i.e. tendency to material pick-up and galling, of the evaluated tribo-systems. Moreover the SEM analysis shows that different workpiece materials result in different types of material pick-up....

  15. FDTD Stability: Critical Time Increment

    Z. Skvor

    2003-06-01

    Full Text Available A new approach suitable for determination of the maximal stable timeincrement for the Finite-Difference Time-Domain (FDTD algorithm incommon curvilinear coordinates, for general mesh shapes and certaintypes of boundaries is presented. The maximal time incrementcorresponds to a characteristic value of a Helmholz equation that issolved by a finite-difference (FD method. If this method uses exactlythe same discretization as the given FDTD method (same mesh, boundaryconditions, order of precision etc., the maximal stable time incrementis obtained from the highest characteristic value. The FD system issolved by an iterative method, which uses only slightly alteredoriginal FDTD formulae. The Courant condition yields a stable timeincrement, but in certain cases the maximum increment is slightlygreater [2].

  16. Incremental Observer Relative Data Extraction

    Bukauskas, Linas; Bøhlen, Michael Hanspeter

    2004-01-01

    The visual exploration of large databases calls for a tight coupling of database and visualization systems. Current visualization systems typically fetch all the data and organize it in a scene tree that is then used to render the visible data. For immersive data explorations in a Cave...... or a Panorama, where an observer is data space this approach is far from optimal. A more scalable approach is to make the observer-aware database system and to restrict the communication between the database and visualization systems to the relevant data. In this paper VR-tree, an extension of the R......-tree, is used to index visibility ranges of objects. We introduce a new operator for incremental Observer Relative data Extraction (iORDE). We propose the Volatile Access STructure (VAST), a lightweight main memory structure that is created on the fly and is maintained during visual data explorations. VAST...

  17. Antibubbles and fine cylindrical sheets of air

    Beilharz, D.; Guyon, A.; Li, E.Q.; Thoraval, Marie-Jean; Thoroddsen, S.T.

    2015-01-01

    Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a

  18. On excursion increments in heartbeat dynamics

    Guzmán-Vargas, L.; Reyes-Ramírez, I.; Hernández-Pérez, R.

    2013-01-01

    We study correlation properties of excursion increments of heartbeat time series from healthy subjects and heart failure patients. We construct the excursion time based on the original heartbeat time series, representing the time employed by the walker to return to the local mean value. Next, the detrended fluctuation analysis and the fractal dimension method are applied to the magnitude and sign of the increments in the time excursions between successive excursions for the mentioned groups. Our results show that for magnitude series of excursion increments both groups display long-range correlations with similar correlation exponents, indicating that large (small) increments (decrements) are more likely to be followed by large (small) increments (decrements). For sign sequences and for both groups, we find that increments are short-range anti-correlated, which is noticeable under heart failure conditions

  19. Increment memory module for spectrometric data recording

    Zhuchkov, A.A.; Myagkikh, A.I.

    1988-01-01

    Incremental memory unit designed to input differential energy spectra of nuclear radiation is described. ROM application as incremental device has allowed to reduce the number of elements and do simplify information readout from the unit. 12-bit 2048 channels present memory unit organization. The device is connected directly with the bus of microprocessor systems similar to KR 580. Incrementation maximal time constitutes 3 mks. It is possible to use this unit in multichannel counting mode

  20. Small Diameter Bomb Increment II (SDB II)

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-439 Small Diameter Bomb Increment II (SDB II) As of FY 2017 President’s Budget Defense... Bomb Increment II (SDB II) DoD Component Air Force Joint Participants Department of the Navy Responsible Office References SAR Baseline (Production...Mission and Description Small Diameter Bomb Increment II (SDB II) is a joint interest United States Air Force (USAF) and Department of the Navy

  1. Incremental Query Rewriting with Resolution

    Riazanov, Alexandre; Aragão, Marcelo A. T.

    We address the problem of semantic querying of relational databases (RDB) modulo knowledge bases using very expressive knowledge representation formalisms, such as full first-order logic or its various fragments. We propose to use a resolution-based first-order logic (FOL) reasoner for computing schematic answers to deductive queries, with the subsequent translation of these schematic answers to SQL queries which are evaluated using a conventional relational DBMS. We call our method incremental query rewriting, because an original semantic query is rewritten into a (potentially infinite) series of SQL queries. In this chapter, we outline the main idea of our technique - using abstractions of databases and constrained clauses for deriving schematic answers, and provide completeness and soundness proofs to justify the applicability of this technique to the case of resolution for FOL without equality. The proposed method can be directly used with regular RDBs, including legacy databases. Moreover, we propose it as a potential basis for an efficient Web-scale semantic search technology.

  2. Modelling the Antarctic Ice Sheet

    Pedersen, Jens Olaf Pepke; Holm, A.

    2015-01-01

    to sea level high stands during past interglacial periods. A number of AIS models have been developed and applied to try to understand the workings of the AIS and to form a robust basis for future projections of the AIS contribution to sea level change. The recent DCESS (Danish Center for Earth System......The Antarctic ice sheet is a major player in the Earth’s climate system and is by far the largest depository of fresh water on the planet. Ice stored in the Antarctic ice sheet (AIS) contains enough water to raise sea level by about 58 m, and ice loss from Antarctica contributed significantly...

  3. fibrin–chitosan–sodium alginate composite sheet

    sodium alginate composite (F–C–SA) in sheet form. F–C–SA composite was prepared and characterized for its physicochemical properties like water absorption capacity, surface morphology, FTIR spectra and mechanical properties.

  4. TRIBOLOGICAL TESTING IN SHEET METAL FORMING

    Vega Tarantino, Salvador

    alternative lubricants in order to substitute the old and harmful chlorinated paraffin oils. The present project is a small part included in that bigger project called Enlub, in which the newly developed lubricants have been tested by tribological simulative methods. The bending under tension test (BUT...

  5. Natural Gas pipelines: economics of incremental capacity

    Kimber, M.

    2000-01-01

    A number of gas transmission pipeline systems in Australia exhibit capacity constraints, and yet there is little evidence of creative or innovative processes from either the service provides of the regulators which might provide a market-based response to these constraints. There is no provision in the Code in its current form to allow it to accommodate these processes. This aspect is one of many that require review to make the Code work. It is unlikely that the current members of the National Gas Pipeline Advisory Committee (NGPAC) or its advisers have sufficient understanding of the analysis of risk and the consequential commercial drivers to implement the necessary changes. As a result, the Code will increasingly lose touch with the commercial realities of the energy market and will continue to inhibit investment in new and expanded infrastructure where market risk is present. The recent report prepared for the Business Council of Australia indicates a need to re-vitalise the energy reform process. It is important for the Australian energy industry to provide leadership and advice to governments to continue the process of reform, and, in particular, to amend the Code to make it more relevant. These amendments must include a mechanism by which price signals can be generated to provide timely and effective information for existing service providers or new entrants to install incremental pipeline capacity

  6. Incremental fold tests of remagnetized carbonate rocks

    Van Der Voo, R.; van der Pluijm, B.

    2017-12-01

    Many unmetamorphosed carbonates all over the world are demonstrably remagnetized, with the age of the secondary magnetizations typically close to that of the nearest orogeny in space and time. This observation did not become compelling until the mid-1980's, when the incremental fold test revealed the Appalachian carbonates to carry a syn-deformational remanence of likely Permian age (Scotese et al., 1982, Phys. Earth Planet. Int., v. 30, p. 385-395; Cederquist et al., 2006, Tectonophysics v. 422, p. 41-54). Since that time scores of Appalachian and Rocky Mountain carbonate rocks have added results to the growing database of paleopoles representing remagnetizations. Late Paleozoic remagnetizations form a cloud of results surrounding the reference poles of the Laurentian APWP. Remagnetizations in other locales and with inferred ages coeval with regional orogenies (e.g., Taconic, Sevier/Laramide, Variscan, Indosinian) are also ubiquitous. To be able to transform this cornucopia into valuable anchor-points on the APWP would be highly desirable. This may indeed become feasible, as will be explained next. Recent studies of faulted and folded carbonate-shale sequences have shown that this deformation enhances the illitization of smectite (Haines & van der Pluijm, 2008, Jour. Struct. Geol., v. 30, p. 525-538; Fitz-Diaz et al., 2014, International Geol. Review, v. 56, p. 734-755). 39Ar-40Ar dating of the authigenic illite (neutralizing any detrital illite contribution by taking the intercept of a mixing line) yields, therefore, the age of the deformation. We know that this date is also the age of the syndeformational remanence; thus we have the age of the corresponding paleopole. Results so far are obtained for the Canadian and U.S. Rocky Mountains and for the Spanish Cantabrian carbonates (Tohver et al., 2008, Earth Planet. Sci. Lett., v. 274, p. 524-530) and make good sense in accord with geological knowledge. Incremental fold tests are the tools used for this

  7. Efficient Incremental Checkpointing of Java Programs

    Lawall, Julia Laetitia; Muller, Gilles

    2000-01-01

    This paper investigates the optimization of language-level checkpointing of Java programs. First, we describe how to systematically associate incremental checkpoints with Java classes. While being safe, the genericness of this solution induces substantial execution overhead. Second, to solve...

  8. Joining of Aluminium Alloy Sheets by Rectangular Mechanical Clinching

    Abe, Y.; Mori, K.; Kato, T.

    2011-01-01

    A mechanical clinching has the advantage of low running costs. However, the joint strength is not high. To improve the maximum load of the joined sheets by a mechanical clinching, square and rectangular mechanical clinching were introduced. In the mechanical clinching, the two sheets are mechanically joined by forming an interlock between the lower and upper sheets by the punch and die. The joined length with the interlock was increased by the rectangular punch and die. The deforming behaviours of the sheets in the mechanical clinching were investigated, and then the interlock in the sheets had distribution in the circumference of the projection. Although the interlocks were formed in both projection side and diagonal, the interlock in the diagonal was smaller because of the long contact length between the lower sheet and the die cavity surface. The maximum load of the joined sheets by the rectangular mechanical clinching was two times larger than the load by the round mechanical clinching.

  9. Orientation and Morphology Effects in Rapid Silicon Sheet Solidification

    Ciszek, T. F.

    1984-01-01

    Radial growth anisotropies and equilibrium forms of point nucleated, dislocation free silicon sheets spreading horizontally on the free surface of a silicon melt were measured for (100), (110), (111), and (112) sheet planes. The growth process was recorded. Qualitative Wulff surface free energy polar plots were deduced from the equilibrium shapes for each sheet plane. Predicted geometries for the tip shape of unidirectional, dislocation free, horizontally grown sheets growing in various directions within the planes were analyzed. Polycrystalline sheets and dendrite propagation were analyzed. For dendrites, growth rates on the order of 2.5 m/min and growth rate anisotropies of 25 are measured.

  10. Thermomechanical processing of plasma sprayed intermetallic sheets

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  11. Antibubbles and fine cylindrical sheets of air

    Beilharz, D.

    2015-08-14

    Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a higher-viscosity drop onto a lower-viscosity pool, we have explored new geometries of such air films. In this way we are able to maintain stable air layers which can wrap around the entire drop to form repeatable antibubbles, i.e. spherical air layers bounded by inner and outer liquid masses. Furthermore, for the most viscous drops they enter the pool trailing a viscous thread reaching all the way to the pinch-off nozzle. The air sheet can also wrap around this thread and remain stable over an extended period of time to form a cylindrical air sheet. We study the parameter regime where these structures appear and their subsequent breakup. The stability of these thin cylindrical air sheets is inconsistent with inviscid stability theory, suggesting stabilization by lubrication forces within the submicron air layer. We use interferometry to measure the air-layer thickness versus depth along the cylindrical air sheet and around the drop. The air film is thickest above the equator of the drop, but thinner below the drop and up along the air cylinder. Based on microbubble volumes, the thickness of the cylindrical air layer becomes less than 100 nm before it ruptures.

  12. Antibubbles and fine cylindrical sheets of air

    Beilharz, D.; Guyon, A.; Li, E.  Q.; Thoraval, M.-J.; Thoroddsen, Sigurdur T

    2015-01-01

    Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a higher-viscosity drop onto a lower-viscosity pool, we have explored new geometries of such air films. In this way we are able to maintain stable air layers which can wrap around the entire drop to form repeatable antibubbles, i.e. spherical air layers bounded by inner and outer liquid masses. Furthermore, for the most viscous drops they enter the pool trailing a viscous thread reaching all the way to the pinch-off nozzle. The air sheet can also wrap around this thread and remain stable over an extended period of time to form a cylindrical air sheet. We study the parameter regime where these structures appear and their subsequent breakup. The stability of these thin cylindrical air sheets is inconsistent with inviscid stability theory, suggesting stabilization by lubrication forces within the submicron air layer. We use interferometry to measure the air-layer thickness versus depth along the cylindrical air sheet and around the drop. The air film is thickest above the equator of the drop, but thinner below the drop and up along the air cylinder. Based on microbubble volumes, the thickness of the cylindrical air layer becomes less than 100 nm before it ruptures.

  13. Ice sheet in peril

    Hvidberg, Christine Schøtt

    2016-01-01

    Earth's large ice sheets in Greenland and Antarctica are major contributors to sea level change. At present, the Greenland Ice Sheet (see the photo) is losing mass in response to climate warming in Greenland (1), but the present changes also include a long-term response to past climate transitions...

  14. Mobility Balance Sheet 2009

    Jorritsma, P.; Derriks, H.; Francke, J.; Gordijn, H.; Groot, W.; Harms, L.; Van der Loop, H.; Peer, S.; Savelberg, F.; Wouters, P.

    2009-06-01

    The Mobility Balance Sheet provides an overview of the state of the art of mobility in the Netherlands. In addition to describing the development of mobility this report also provides explanations for the growth of passenger and freight transport. Moreover, the Mobility Balance Sheet also focuses on a topical theme: the effects of economic crises on mobility. [nl

  15. Growth increments in teeth of Diictodon (Therapsida

    J. Francis Thackeray

    1991-09-01

    Full Text Available Growth increments circa 0.02 mm in width have been observed in sectioned tusks of Diictodon from the Late Permian lower Beaufort succession of the South African Karoo, dated between about 260 and 245 million years ago. Mean growth increments show a decline from relatively high values in the Tropidostoma/Endothiodon Assemblage Zone, to lower values in the Aulacephalodon/Cistecephaluszone, declining still further in the Dicynodon lacerficeps/Whaitsia zone at the end of the Permian. These changes coincide with gradual changes in carbon isotope ratios measured from Diictodon tooth apatite. It is suggested that the decline in growth increments is related to environmental changes associated with a decline in primary production which contributed to the decline in abundance and ultimate extinction of Diictodon.

  16. Automatic incrementalization of Prolog based static analyses

    Eichberg, Michael; Kahl, Matthias; Saha, Diptikalyan

    2007-01-01

    Modem development environments integrate various static analyses into the build process. Analyses that analyze the whole project whenever the project changes are impractical in this context. We present an approach to automatic incrementalization of analyses that are specified as tabled logic...... programs and evaluated using incremental tabled evaluation, a technique for efficiently updating memo tables in response to changes in facts and rules. The approach has been implemented and integrated into the Eclipse IDE. Our measurements show that this technique is effective for automatically...

  17. Incremental Integrity Checking: Limitations and Possibilities

    Christiansen, Henning; Martinenghi, Davide

    2005-01-01

    Integrity checking is an essential means for the preservation of the intended semantics of a deductive database. Incrementality is the only feasible approach to checking and can be obtained with respect to given update patterns by exploiting query optimization techniques. By reducing the problem...... to query containment, we show that no procedure exists that always returns the best incremental test (aka simplification of integrity constraints), and this according to any reasonable criterion measuring the checking effort. In spite of this theoretical limitation, we develop an effective procedure...

  18. History Matters: Incremental Ontology Reasoning Using Modules

    Cuenca Grau, Bernardo; Halaschek-Wiener, Christian; Kazakov, Yevgeny

    The development of ontologies involves continuous but relatively small modifications. Existing ontology reasoners, however, do not take advantage of the similarities between different versions of an ontology. In this paper, we propose a technique for incremental reasoning—that is, reasoning that reuses information obtained from previous versions of an ontology—based on the notion of a module. Our technique does not depend on a particular reasoning calculus and thus can be used in combination with any reasoner. We have applied our results to incremental classification of OWL DL ontologies and found significant improvement over regular classification time on a set of real-world ontologies.

  19. The transposition of the balance sheet to financial and functional balance sheet. Research and development

    Liana GĂDĂU

    2015-09-01

    Full Text Available As the title suggests, through this paper we want to highlight the necessity of treating again the content and the form of the balance sheet in order to adapt it to a more efficient analysis, this way surpassing the informational valences of the classic balance sheet. The functional and the financial balance sheet will be taken into account. These models of balance sheet permit the complex analyses regarding the solvability or the bankruptcy risk of an enterprise to take place, and also other analyses, like the analysis of the structure and the financial/ functional equilibrium, the analysis of the company on operating cycles and their role in the functioning of the company. Through the particularities offered by each of these two models of balance sheet, we want to present the advantages of a superior informing. This content of this material is based on a vast investigation of the specialized literature.

  20. Single clay sheets inside electrospun polymer nanofibers

    Sun, Zhaohui

    2005-03-01

    Nanofibers were prepared from polymer solution with clay sheets by electrospinning. Plasma etching, as a well controlled process, was used to supply electrically excited gas molecules from a glow discharge. To reveal the structure and arrangement of clay layers in the polymer matrix, plasma etching was used to remove the polymer by controlled gasification to expose the clay sheets due to the difference in reactivity. The shape, flexibility, and orientation of clay sheets were studied by transmission and scanning electron microscopy. Additional quantitative information on size distribution and degree of exfoliation of clay sheets were obtained by analyzing electron micrograph of sample after plasma etching. Samples in various forms including fiber, film and bulk, were thinned by plasma etching. Morphology and dispersion of inorganic fillers were studied by electron microscopy.

  1. Simulations of the Scandinavian ice sheet and its subsurface conditions

    Boulton, G.S.; Caban, P.; Hulton, N.

    1999-12-01

    An ice sheet model has been applied to an approximate flow line through the area of the Fennoscandian ice sheet. The modelled ice sheet fluctuations have been matched with stratigraphic evidence of Weichselian ice sheet fluctuation in order to simulate ice sheet attributes through time along the flowline. The model predicts extensive melting at the base of the ice sheet. This output has been used as an input to a simplified model of hydrogeology along the southern flank of the ice sheet so as to reconstruct patterns of subglacial groundwater flow. The output from the model is also used to estimate patterns of subglacial stress and strain. Results suggest that large scale subglacial groundwater catchment are formed which were quite different in extent from modern catchment; that fossil subglacial groundwaters should be found at sampling depths; and much fracturing in shallow bedrock in Sweden could be glacially generated

  2. Simulations of the Scandinavian ice sheet and its subsurface conditions

    Boulton, G.S.; Caban, P.; Hulton, N. [Edinburgh Univ. (United Kingdom). Dept of Geology and Geophysics

    1999-12-01

    An ice sheet model has been applied to an approximate flow line through the area of the Fennoscandian ice sheet. The modelled ice sheet fluctuations have been matched with stratigraphic evidence of Weichselian ice sheet fluctuation in order to simulate ice sheet attributes through time along the flowline. The model predicts extensive melting at the base of the ice sheet. This output has been used as an input to a simplified model of hydrogeology along the southern flank of the ice sheet so as to reconstruct patterns of subglacial groundwater flow. The output from the model is also used to estimate patterns of subglacial stress and strain. Results suggest that large scale subglacial groundwater catchment are formed which were quite differentin extent from modern catchment; that fossil subglacial groundwaters should be found at sampling depths; and much fracturing in shallow bedrock in Sweden could be glacially generated.

  3. Carbon sheet pumping

    Ohyabu, N.; Sagara, A.; Kawamura, T.; Motojima, O.; Ono, T.

    1993-07-01

    A new hydrogen pumping scheme has been proposed which controls recycling of the particles for significant improvement of the energy confinement in toroidal magnetic fusion devices. In this scheme, a part of the vacuum vessel surface near the divertor is covered with carbon sheets of a large surface area. Before discharge initiation, the sheets are baked up to 700 ∼ 1000degC to remove the previously trapped hydrogen atoms. After being cooled down to below ∼ 200degC, the unsaturated carbon sheets trap high energy charge exchange hydrogen atoms effectively during a discharge and overall pumping efficiency can be as high as ∼ 50 %. (author)

  4. Design of methodology for incremental compiler construction

    Pavel Haluza

    2011-01-01

    Full Text Available The paper deals with possibilities of the incremental compiler construction. It represents the compiler construction possibilities for languages with a fixed set of lexical units and for languages with a variable set of lexical units, too. The methodology design for the incremental compiler construction is based on the known algorithms for standard compiler construction and derived for both groups of languages. Under the group of languages with a fixed set of lexical units there belong languages, where each lexical unit has its constant meaning, e.g., common programming languages. For this group of languages the paper tries to solve the problem of the incremental semantic analysis, which is based on incremental parsing. In the group of languages with a variable set of lexical units (e.g., professional typographic system TEX, it is possible to change arbitrarily the meaning of each character on the input file at any time during processing. The change takes effect immediately and its validity can be somehow limited or is given by the end of the input. For this group of languages this paper tries to solve the problem case when we use macros temporarily changing the category of arbitrary characters.

  5. Existing School Buildings: Incremental Seismic Retrofit Opportunities.

    Federal Emergency Management Agency, Washington, DC.

    The intent of this document is to provide technical guidance to school district facility managers for linking specific incremental seismic retrofit opportunities to specific maintenance and capital improvement projects. The linkages are based on logical affinities, such as technical fit, location of the work within the building, cost saving…

  6. Automatic incrementalization of Prolog based static analyses

    Eichberg, Michael; Kahl, Matthias; Saha, Diptikalyan

    2007-01-01

    Modem development environments integrate various static analyses into the build process. Analyses that analyze the whole project whenever the project changes are impractical in this context. We present an approach to automatic incrementalization of analyses that are specified as tabled logic prog...

  7. Anesthesia Fact Sheet

    ... Education About NIGMS NIGMS Home > Science Education > Anesthesia Anesthesia Tagline (Optional) Middle/Main Content Area En español ... Version (464 KB) Other Fact Sheets What is anesthesia? Anesthesia is a medical treatment that prevents patients ...

  8. Structural Biology Fact Sheet

    ... NIGMS NIGMS Home > Science Education > Structural Biology Structural Biology Tagline (Optional) Middle/Main Content Area PDF Version (688 KB) Other Fact Sheets What is structural biology? Structural biology is the study of how biological ...

  9. Global ice sheet modeling

    Hughes, T.J.; Fastook, J.L.

    1994-05-01

    The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed

  10. Sheet production apparatus for removing a crystalline sheet from the surface of a melt using gas jets located above and below the crystalline sheet

    Kellerman, Peter L.; Thronson, Gregory D.

    2017-06-14

    In one embodiment, a sheet production apparatus comprises a vessel configured to hold a melt of a material. A cooling plate is disposed proximate the melt and is configured to form a sheet of the material on the melt. A first gas jet is configured to direct a gas toward an edge of the vessel. A sheet of a material is translated horizontally on a surface of the melt and the sheet is removed from the melt. The first gas jet may be directed at the meniscus and may stabilize this meniscus or increase local pressure within the meniscus.

  11. Energy information sheets

    NONE

    1995-07-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

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

    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

  13. Copper contamination in thin stainless steel sheet

    Holbert, R.K. Jr.; Dobbins, A.G.; Bennett, R.K. Jr.

    1986-01-01

    The standard welding technique used at Oak Ridge Y-12 Plant for joining thin stainless sheet is the gas tungsten arc (GTA) welding process. One of the reoccurring problems with the sheet welds is surface cracking in the heat-affected zone (HAZ). Metallography shows that the cracks are only about 0.05 mm (0.002 in.) deep which is significant in a 0.25 mm (0.01 in.) thick sheet. Thus, welding requirements do not permit any surfacing cracking as detected by a fluorescent dye penetrant test conducted on every part after welding. Surface cracks have been found in both of the two most common weld designs in the thin sheet fabricated at the Oak Ridge Y-12 Plant. These butt joints are welded between two 0.25 mm thick stainless steel sheets and a tube with eyelet welded to a 25 mm (0.98 in.) thick sheet. The weld between the two sheets is made on a semiautomatic seam welding unit, whereas the tube-to-eyelet-to-sheet welds are done manually. The quality of both welds is very dependent on the welding procedure and the way the parts are placed in the weld fixturing. Metallographic examination has indicated that some welded parts with surface cracking in the weld region had copper particles on the surface, and the question of copper contamination has been raised. With the aid of a scanning electron microscope and an electron microprobe, the existence of copper in an around the surface cracks has been verified. The copper is on the surface of the parts prior to welding in the form of small dust particles

  14. Statistics of wind direction and its increments

    Doorn, Eric van; Dhruva, Brindesh; Sreenivasan, Katepalli R.; Cassella, Victor

    2000-01-01

    We study some elementary statistics of wind direction fluctuations in the atmosphere for a wide range of time scales (10 -4 sec to 1 h), and in both vertical and horizontal planes. In the plane parallel to the ground surface, the direction time series consists of two parts: a constant drift due to large weather systems moving with the mean wind speed, and fluctuations about this drift. The statistics of the direction fluctuations show a rough similarity to Brownian motion but depend, in detail, on the wind speed. This dependence manifests itself quite clearly in the statistics of wind-direction increments over various intervals of time. These increments are intermittent during periods of low wind speeds but Gaussian-like during periods of high wind speeds. (c) 2000 American Institute of Physics

  15. Evolving effective incremental SAT solvers with GP

    Bader, Mohamed; Poli, R.

    2008-01-01

    Hyper-Heuristics could simply be defined as heuristics to choose other heuristics, and it is a way of combining existing heuristics to generate new ones. In a Hyper-Heuristic framework, the framework is used for evolving effective incremental (Inc*) solvers for SAT. We test the evolved heuristics (IncHH) against other known local search heuristics on a variety of benchmark SAT problems.

  16. Teraflop-scale Incremental Machine Learning

    Özkural, Eray

    2011-01-01

    We propose a long-term memory design for artificial general intelligence based on Solomonoff's incremental machine learning methods. We use R5RS Scheme and its standard library with a few omissions as the reference machine. We introduce a Levin Search variant based on Stochastic Context Free Grammar together with four synergistic update algorithms that use the same grammar as a guiding probability distribution of programs. The update algorithms include adjusting production probabilities, re-u...

  17. Numerical simulation on chain-die forming of an AHSS top-hat section

    Majji, Raju; Xiang, Yang; Ding, Scott; Yang, Chunhui

    2018-05-01

    The applications of Advanced High-Strength Steels (AHSS) in the automotive industry are rapidly increasing due to a demand for a lightweight material that significantly reduces fuel consumption without compromising passenger safety. Automotive industries and material suppliers are expected by consumers to deliver reliable and affordable products, thus stimulating these manufacturers to research solutions to meet these customer requirements. The primary advantage of AHSS is its extremely high strength to weight ratio, an ideal material for the automotive industry. However, its low ductility is a major disadvantage, in particular, when using traditional cold forming processes such as roll forming and deep drawing process to form profiles. Consequently, AHSS parts frequently fail to form. Thereby, in order to improve quality and reliability on manufacturing AHSS products, a recently-developed incremental cold sheet metal forming technology called Chain-die Forming (CDF) is recognised as a potential solution to the forming process of AHSS. The typical CDF process is a combination of bending and roll forming processes which is equivalent to a roll with a large deforming radius, and incrementally forms the desired shape with split die and segments. This study focuses on manufacturing an AHSS top-hat section with minimum passes without geometrical or surface defects by using finite element modelling and simulations. The developed numerical simulation is employed to investigate the influences on the main control parameter of the CDF process while forming AHSS products and further develop new die-punch sets of compensation design via a numerical optimal process. In addition, the study focuses on the tool design to compensate spring-back and reduce friction between tooling and sheet-metal. This reduces the number of passes, thereby improving productivity and reducing energy consumption and material waste. This numerical study reveals that CDF forms AHSS products of complex

  18. Shakedown analysis by finite element incremental procedures

    Borkowski, A.; Kleiber, M.

    1979-01-01

    It is a common occurence in many practical problems that external loads are variable and the exact time-dependent history of loading is unknown. Instead of it load is characterized by a given loading domain: a convex polyhedron in the n-dimensional space of load parameters. The problem is then to check whether a structure shakes down, i.e. responds elastically after a few elasto-plastic cycles, or not to a variable loading as defined above. Such check can be performed by an incremental procedure. One should reproduce incrementally a simple cyclic process which consists of proportional load paths that connect the origin of the load space with the corners of the loading domain. It was proved that if a structure shakes down to such loading history then it is able to adopt itself to an arbitrary load path contained in the loading domain. The main advantage of such approach is the possibility to use existing incremental finite-element computer codes. (orig.)

  19. Safety advice sheets

    HSE Unit

    2013-01-01

    You never know when you might be faced with questions such as: when/how should I dispose of a gas canister? Where can I find an inspection report? How should I handle/store/dispose of a chemical substance…?   The SI section of the DGS/SEE Group is primarily responsible for safety inspections, evaluating the safety conditions of equipment items, premises and facilities. On top of this core task, it also regularly issues “Safety Advice Sheets” on various topics, designed to be of assistance to users but also to recall and reinforce safety rules and procedures. These clear and concise sheets, complete with illustrations, are easy to display in the appropriate areas. The following safety advice sheets have been issued so far: Other sheets will be published shortly. Suggestions are welcome and should be sent to the SI section of the DGS/SEE Group. Please send enquiries to general-safety-visits.service@cern.ch.

  20. Friction and bending forces evaluation of AISI 304 DDQ steel sheet forming by bending tests under deep-drawing multiaxial stresses; Evaluacion de la fuerza de doblado y de friccion en el conformado de chapa de acero inoxidable AISI 304 DDQ mediante ensayos de doblado en condiciones multiaxiales de embuticion

    Coello, J.; Miguel, V.; Ferrer, C.; Calatayud, A.; Martinez, A.

    2012-11-01

    Die radius is a critical area from the viewpoint of friction in forming processes. Moreover the sheet, that has been previously deformed in flange area, suffers bending and unbending stresses. Then, die-sheet contact in die radius must be especially considered in order to guarantee the suitable lubrication conditions. In the present work, a test method is carried out for evaluating an AISI 304 DDQ steel under similar conditions to those existing in the die radius area and that, usually, are not really reproduced in traditional bending under tensions tests. Deformation under pure shear condition, the bending and the radius angle have been established as variables of the tests. Results allow to obtain the apparent pressure sheet-bending tool, that increases with bending angle and decreases with tool radius. This last variable is the most significant while the bending angle has lesser influence. Although experimental results present some concordances with values obtained by analytical methods, some corrections must be considered in them in order to improve the theoretical values. (Author) 18 refs.

  1. Warm Deep Drawing of Aluminium Sheet

    Bolt, P.J.; Werkhoven, R.J.; van den Boogaard, Antonius H.

    2003-01-01

    Aluminium sheet drawing processes can be improved by manipulating local flow behaviour by means of elevated temperatures and temperature gradients in the tooling. Forming tests showed that a substantial improvement is possible not only for 5xxx but also for 6xxx series alloys. Finite element method

  2. 16 CFR 460.13 - Fact sheets.

    2010-01-01

    ... INSULATION § 460.13 Fact sheets. If you are a manufacturer, you must give retailers and installers fact... uses. (b) A heading: “This is ____ insulation.” Fill in the blank with the type and form of your... compressed during installation.” (e) After the chart and any statement dealing with the specific type of...

  3. Laboratory Powder Metallurgy Makes Tough Aluminum Sheet

    Royster, D. M.; Thomas, J. R.; Singleton, O. R.

    1993-01-01

    Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

  4. Environmental constraints on West Antarctic ice-sheet formation

    Lindstrom, D R; MacAyeal, D R

    1987-01-01

    Small perturbations in Antarctic environmental conditions can culminate in the demise of the Antarctic ice sheet's western sector. This may have happened during the last interglacial period, and could recur within the next millennium due to atmospheric warming from trace gas and CO/sub 2/ increases. In this study, we investigate the importance of sea-level, accumulation rate, and ice influx from the East Antarctic ice sheet in the re-establishment of the West Antarctic ice sheet from a thin cover using a time-dependent numerical ice-shelf model. Our results show that a precursor to the West Antarctic ice sheet can form within 3000 years. Sea-level lowering caused by ice-sheet development in the Northern Hemisphere has the greatest environmental influence. Under favorable conditions, ice grounding occurs over all parts of the West Antarctic ice sheet except up-stream of Thwaites Glacier and in the Ross Sea region.

  5. Ice Sheets & Ice Cores

    Mikkelsen, Troels Bøgeholm

    Since the discovery of the Ice Ages it has been evident that Earth’s climate is liable to undergo dramatic changes. The previous climatic period known as the Last Glacial saw large oscillations in the extent of ice sheets covering the Northern hemisphere. Understanding these oscillations known....... The first part concerns time series analysis of ice core data obtained from the Greenland Ice Sheet. We analyze parts of the time series where DO-events occur using the so-called transfer operator and compare the results with time series from a simple model capable of switching by either undergoing...

  6. Energy information sheets

    1993-12-02

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the general public. Written for the general public, the EIA publication Energy Information Sheets was developed to provide information on various aspects of fuel production, prices, consumption and capability. The information contained herein pertains to energy data as of December 1991. Additional information on related subject matter can be found in other EIA publications as referenced at the end of each sheet.

  7. Buckling of Aluminium Sheet Components

    Hegadekatte, Vishwanath; Shi, Yihai; Nardini, Dubravko

    Wrinkling is one of the major defects in sheet metal forming processes. It may become a serious obstacle to implementing the forming process and assembling the parts, and may also play a significant role in the wear of the tool. Wrinkling is essentially a local buckling phenomenon that results from compressive stresses (compressive instability) e.g., in the hoop direction for axi-symmetric systems such as beverage cans. Modern beverage can is a highly engineered product with a complex geometry. Therefore in order to understand wrinkling in such a complex system, we have started by studying wrinkling with the Yoshida buckling test. Further, we have studied the buckling of ideal and dented beverage cans under axial loading by laboratory testing. We have modelled the laboratory tests and also the imperfection sensitivity of the two systems using finite element method and the predictions are in qualitative agreement with experimental data.

  8. Balance sheet capacity and endogenous risk

    Jon Danielsson; Hyun Song Shin; Jean-Pierre Zigrand

    2011-01-01

    Banks operating under Value-at-Risk constraints give rise to a well-defined aggregate balance sheet capacity for the banking sector as a whole that depends on total bank capital. Equilibrium risk and market risk premiums can be solved in closed form as functions of aggregate bank capital. We explore the empirical properties of the model in light of recent experience in the financial crisis and highlight the importance of balance sheet capacity as the driver of the financial cycle and market r...

  9. Simulation and comparison of perturb and observe and incremental ...

    Perturb and Observe (P & O) algorithm and Incremental conductance algorithm. ... Keywords. Solar array; insolation; MPPT; modelling, P & O; incremental conductance. 1. .... voltage level. It is also ..... Int. J. Advances in Eng. Technol. 133–148.

  10. Stem analysis program (GOAP for evaluating of increment and growth data at individual tree

    Gafura Aylak Özdemir

    2016-07-01

    Full Text Available Stem analysis is a method evaluating in a detailed way data of increment and growth of individual tree at the past periods and widely used in various forestry disciplines. Untreated data of stem analysis consist of annual ring count and measurement procedures performed on cross sections taken from individual tree by section method. The evaluation of obtained this untreated data takes quite some time. Thus, a computer software was developed in this study to quickly and efficiently perform stem analysis. This computer software developed to evaluate untreated data of stem analysis as numerical and graphical was programmed as macro by utilizing Visual Basic for Application feature of MS Excel 2013 program currently the most widely used. In developed this computer software, growth height model is formed from two different approaches, individual tree volume depending on section method, cross-sectional area, increments of diameter, height and volume, volume increment percent and stem form factor at breast height are calculated depending on desired period lengths. This calculated values are given as table. Development of diameter, height, volume, increments of these variables, volume increment percent and stem form factor at breast height according to periodic age are given as chart. Stem model showing development of diameter, height and shape of individual tree in the past periods also can be taken from computer software as chart.

  11. Collisionless current sheet equilibria

    Neukirch, T.; Wilson, F.; Allanson, O.

    2018-01-01

    Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic energy via processes such as magnetic reconnection. In this contribution we will focus on collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for collisionless current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets). This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas. In this paper we will give an overview of some of the recent developments, discuss their potential applications and address a number of open questions.

  12. Cholera Fact Sheet

    ... news-room/fact-sheets/detail/cholera","@context":"http://schema.org","@type":"Article"}; العربية 中文 français русский español ... that includes feedback at the local level and information-sharing at the global level. Cholera cases are ...

  13. Pseudomonas - Fact Sheet

    Public Health Agency

    2012-01-01

    Fact sheet on Pseudomonas, including:What is Pseudomonas?What infections does it cause?Who is susceptible to pseudomonas infection?How will I know if I have pseudomonas infection?How can Pseudomonas be prevented from spreading?How can I protect myself from Pseudomonas?How is Pseudomonas infection treated?

  14. NTPR Fact Sheets

    History Documents US Underground Nuclear Test History Reports NTPR Radiation Exposure Reports Enewetak Atoll Cleanup Documents TRAC About Who We Are Our Values History Locations Our Leadership Director Support Center Contact Us FAQ Sheet Links Success Stories Contracts Business Opportunities Current

  15. Production (information sheets)

    2007-01-01

    Documentation sheets: Geo energy 2 Integrated System Approach Petroleum Production (ISAPP) The value of smartness 4 Reservoir permeability estimation from production data 6 Coupled modeling for reservoir application 8 Toward an integrated near-wellbore model 10 TNO conceptual framework for "E&P

  16. Hibernia fact sheet

    Anon.

    1994-01-01

    This fact sheet gives details of the Hibernia oil field including its location, discovery date, oil company's interests in the project, the recoverable reserves of the two reservoirs, the production system used, capital costs of the project, and overall targets for Canadian benefit. Significant dates for the Hibernia project are listed. (UK)

  17. Ethanol Basics (Fact Sheet)

    2015-01-01

    Ethanol is a widely-used, domestically-produced renewable fuel made from corn and other plant materials. More than 96% of gasoline sold in the United States contains ethanol. Learn more about this alternative fuel in the Ethanol Basics Fact Sheet, produced by the U.S. Department of Energy's Clean Cities program.

  18. Estimation of incremental reactivities for multiple day scenarios: an application to ethane and dimethyoxymethane

    Stockwell, William R.; Geiger, Harald; Becker, Karl H.

    Single-day scenarios are used to calculate incremental reactivities by definition (Carter, J. Air Waste Management Assoc. 44 (1994) 881-899.) but even unreactive organic compounds may have a non-negligible effect on ozone concentrations if multiple-day scenarios are considered. The concentration of unreactive compounds and their products may build up over a multiple-day period and the oxidation products may be highly reactive or highly unreactive affecting the overall incremental reactivity of the organic compound. We have developed a method for calculating incremental reactivities for multiple days based on a standard scenario for polluted European conditions. This method was used to estimate maximum incremental reactivities (MIR) and maximum ozone incremental reactivities (MOIR) for ethane and dimethyoxymethane for scenarios ranging from 1 to 6 days. It was found that the incremental reactivities increased as the length of the simulation period increased. The MIR of ethane increased faster than the value for dimethyoxymethane as the scenarios became longer. The MOIRs of ethane and dimethyoxymethane increased but the change was more modest for scenarios longer than 3 days. MOIRs of both volatile organic compounds were equal within the uncertainties of their chemical mechanisms by the 5 day scenario. These results show that dimethyoxymethane has an ozone forming potential on a per mass basis that is only somewhat greater than ethane if multiple-day scenarios are considered.

  19. Broad Learning System: An Effective and Efficient Incremental Learning System Without the Need for Deep Architecture.

    Chen, C L Philip; Liu, Zhulin

    2018-01-01

    Broad Learning System (BLS) that aims to offer an alternative way of learning in deep structure is proposed in this paper. Deep structure and learning suffer from a time-consuming training process because of a large number of connecting parameters in filters and layers. Moreover, it encounters a complete retraining process if the structure is not sufficient to model the system. The BLS is established in the form of a flat network, where the original inputs are transferred and placed as "mapped features" in feature nodes and the structure is expanded in wide sense in the "enhancement nodes." The incremental learning algorithms are developed for fast remodeling in broad expansion without a retraining process if the network deems to be expanded. Two incremental learning algorithms are given for both the increment of the feature nodes (or filters in deep structure) and the increment of the enhancement nodes. The designed model and algorithms are very versatile for selecting a model rapidly. In addition, another incremental learning is developed for a system that has been modeled encounters a new incoming input. Specifically, the system can be remodeled in an incremental way without the entire retraining from the beginning. Satisfactory result for model reduction using singular value decomposition is conducted to simplify the final structure. Compared with existing deep neural networks, experimental results on the Modified National Institute of Standards and Technology database and NYU NORB object recognition dataset benchmark data demonstrate the effectiveness of the proposed BLS.

  20. 48 CFR 3432.771 - Provision for incremental funding.

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Provision for incremental funding. 3432.771 Section 3432.771 Federal Acquisition Regulations System DEPARTMENT OF EDUCATION..., Incremental Funding, in a solicitation if a cost-reimbursement contract using incremental funding is...

  1. Mountain building and the initiation of the Greenland Ice Sheet

    Solgaard, Anne Munck; Bonow, Johan; Langen, Peter Lang

    2013-01-01

    The effects of a new hypothesis about mountain building in Greenland on ice sheet initiation are investigated using an ice sheet model in combination with a climate model. According to this hypothesis, low-relief landscapes near sea level characterised Greenland in Miocene times until two phases...... superimposed by cold and warm excursions. The modelling results show that no ice initiates in the case of the low-lying and almost flat topography prior to the uplifts. However, the results demonstrate a significant ice sheet growth in response to the orographically induced increase in precipitation....... Under conditions that are colder than the present, the ice can overcome the Föhn effect, flow into the interior and form a coherent ice sheet. The results thus indicate that the Greenland Ice Sheet of today is a relict formed under colder conditions. The modelling results are consistent...

  2. Optimal Output of Distributed Generation Based On Complex Power Increment

    Wu, D.; Bao, H.

    2017-12-01

    In order to meet the growing demand for electricity and improve the cleanliness of power generation, new energy generation, represented by wind power generation, photovoltaic power generation, etc has been widely used. The new energy power generation access to distribution network in the form of distributed generation, consumed by local load. However, with the increase of the scale of distribution generation access to the network, the optimization of its power output is becoming more and more prominent, which needs further study. Classical optimization methods often use extended sensitivity method to obtain the relationship between different power generators, but ignore the coupling parameter between nodes makes the results are not accurate; heuristic algorithm also has defects such as slow calculation speed, uncertain outcomes. This article proposes a method called complex power increment, the essence of this method is the analysis of the power grid under steady power flow. After analyzing the results we can obtain the complex scaling function equation between the power supplies, the coefficient of the equation is based on the impedance parameter of the network, so the description of the relation of variables to the coefficients is more precise Thus, the method can accurately describe the power increment relationship, and can obtain the power optimization scheme more accurately and quickly than the extended sensitivity method and heuristic method.

  3. Enabling Incremental Query Re-Optimization.

    Liu, Mengmeng; Ives, Zachary G; Loo, Boon Thau

    2016-01-01

    As declarative query processing techniques expand to the Web, data streams, network routers, and cloud platforms, there is an increasing need to re-plan execution in the presence of unanticipated performance changes. New runtime information may affect which query plan we prefer to run. Adaptive techniques require innovation both in terms of the algorithms used to estimate costs , and in terms of the search algorithm that finds the best plan. We investigate how to build a cost-based optimizer that recomputes the optimal plan incrementally given new cost information, much as a stream engine constantly updates its outputs given new data. Our implementation especially shows benefits for stream processing workloads. It lays the foundations upon which a variety of novel adaptive optimization algorithms can be built. We start by leveraging the recently proposed approach of formulating query plan enumeration as a set of recursive datalog queries ; we develop a variety of novel optimization approaches to ensure effective pruning in both static and incremental cases. We further show that the lessons learned in the declarative implementation can be equally applied to more traditional optimizer implementations.

  4. Incremental learning for automated knowledge capture

    Benz, Zachary O. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Basilico, Justin Derrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Davis, Warren Leon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Dixon, Kevin R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jones, Brian S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Nathaniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wendt, Jeremy Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2013-12-01

    People responding to high-consequence national-security situations need tools to help them make the right decision quickly. The dynamic, time-critical, and ever-changing nature of these situations, especially those involving an adversary, require models of decision support that can dynamically react as a situation unfolds and changes. Automated knowledge capture is a key part of creating individualized models of decision making in many situations because it has been demonstrated as a very robust way to populate computational models of cognition. However, existing automated knowledge capture techniques only populate a knowledge model with data prior to its use, after which the knowledge model is static and unchanging. In contrast, humans, including our national-security adversaries, continually learn, adapt, and create new knowledge as they make decisions and witness their effect. This artificial dichotomy between creation and use exists because the majority of automated knowledge capture techniques are based on traditional batch machine-learning and statistical algorithms. These algorithms are primarily designed to optimize the accuracy of their predictions and only secondarily, if at all, concerned with issues such as speed, memory use, or ability to be incrementally updated. Thus, when new data arrives, batch algorithms used for automated knowledge capture currently require significant recomputation, frequently from scratch, which makes them ill suited for use in dynamic, timecritical, high-consequence decision making environments. In this work we seek to explore and expand upon the capabilities of dynamic, incremental models that can adapt to an ever-changing feature space.

  5. Two models of minimalist, incremental syntactic analysis.

    Stabler, Edward P

    2013-07-01

    Minimalist grammars (MGs) and multiple context-free grammars (MCFGs) are weakly equivalent in the sense that they define the same languages, a large mildly context-sensitive class that properly includes context-free languages. But in addition, for each MG, there is an MCFG which is strongly equivalent in the sense that it defines the same language with isomorphic derivations. However, the structure-building rules of MGs but not MCFGs are defined in a way that generalizes across categories. Consequently, MGs can be exponentially more succinct than their MCFG equivalents, and this difference shows in parsing models too. An incremental, top-down beam parser for MGs is defined here, sound and complete for all MGs, and hence also capable of parsing all MCFG languages. But since the parser represents its grammar transparently, the relative succinctness of MGs is again evident. Although the determinants of MG structure are narrowly and discretely defined, probabilistic influences from a much broader domain can influence even the earliest analytic steps, allowing frequency and context effects to come early and from almost anywhere, as expected in incremental models. Copyright © 2013 Cognitive Science Society, Inc.

  6. Incremental Nonnegative Matrix Factorization for Face Recognition

    Wen-Sheng Chen

    2008-01-01

    Full Text Available Nonnegative matrix factorization (NMF is a promising approach for local feature extraction in face recognition tasks. However, there are two major drawbacks in almost all existing NMF-based methods. One shortcoming is that the computational cost is expensive for large matrix decomposition. The other is that it must conduct repetitive learning, when the training samples or classes are updated. To overcome these two limitations, this paper proposes a novel incremental nonnegative matrix factorization (INMF for face representation and recognition. The proposed INMF approach is based on a novel constraint criterion and our previous block strategy. It thus has some good properties, such as low computational complexity, sparse coefficient matrix. Also, the coefficient column vectors between different classes are orthogonal. In particular, it can be applied to incremental learning. Two face databases, namely FERET and CMU PIE face databases, are selected for evaluation. Compared with PCA and some state-of-the-art NMF-based methods, our INMF approach gives the best performance.

  7. Rubella - Fact Sheet for Parents

    ... and 4 through 6 years Fact Sheet for Parents Color [2 pages] Español: Rubéola The best way ... according to the recommended schedule. Fact Sheets for Parents Diseases and the Vaccines that Prevent Them Chickenpox ...

  8. [Incremental cost effectiveness of multifocal cataract surgery].

    Pagel, N; Dick, H B; Krummenauer, F

    2007-02-01

    Supplementation of cataract patients with multifocal intraocular lenses involves an additional financial investment when compared to the corresponding monofocal supplementation, which usually is not funded by German health care insurers. In the context of recent resource allocation discussions, however, the cost effectiveness of multifocal cataract surgery could become an important rationale. Therefore an evidence-based estimation of its cost effectiveness was carried out. Three independent meta-analyses were implemented to estimate the gain in uncorrected near visual acuity and best corrected visual acuity (vision lines) as well as the predictability (fraction of patients without need for reading aids) of multifocal supplementation. Study reports published between 1995 and 2004 (English or German language) were screened for appropriate key words. Meta effects in visual gain and predictability were estimated by means and standard deviations of the reported effect measures. Cost data were estimated by German DRG rates and individual lens costs; the cost effectiveness of multifocal cataract surgery was then computed in terms of its marginal cost effectiveness ratio (MCER) for each clinical benefit endpoint; the incremental costs of multifocal versus monofocal cataract surgery were further estimated by means of their respective incremental cost effectiveness ratio (ICER). An independent meta-analysis estimated the complication profiles to be expected after monofocal and multifocal cataract surgery in order to evaluate expectable complication-associated additional costs of both procedures; the marginal and incremental cost effectiveness estimates were adjusted accordingly. A sensitivity analysis comprised cost variations of +/- 10 % and utility variations alongside the meta effect estimate's 95 % confidence intervals. Total direct costs from the health care insurer's perspective were estimated 3363 euro, associated with a visual meta benefit in best corrected visual

  9. Film sheet cassette

    1981-01-01

    A novel film sheet cassette is described for handling CAT photographic films under daylight conditions and facilitating their imaging. A detailed description of the design and operation of the cassette is given together with appropriate illustrations. The resulting cassette is a low-cost unit which is easily constructed and yet provides a sure light-tight seal for the interior contents of the cassette. The individual resilient fingers on the light-trap permit the ready removal of the slide plate for taking pictures. The stippled, non-electrostatic surface of the pressure plate ensures an air layer and free slidability of the film for removal and withdrawal of the film sheet. The advantage of the daylight system is that a darkroom need not be used for inserting and removing the film in and out of the cassette resulting in a considerable time saving. (U.K.)

  10. Clean Cities Fact Sheet

    2004-01-01

    This fact sheet explains the Clean Cities Program and provides contact information for all coalitions and regional offices. It answers key questions such as: What is the Clean Cities Program? What are alternative fuels? How does the Clean Cities Program work? What sort of assistance does Clean Cities offer? What has Clean Cities accomplished? What is Clean Cities International? and Where can I find more information?

  11. Information sheets on energy

    2004-01-01

    These sheets, presented by the Cea, bring some information, in the energy domain, on the following topics: the world energy demand and the energy policy in France and in Europe, the part of the nuclear power in the energy of the future, the greenhouse gases emissions and the fight against the greenhouse effect, the carbon dioxide storage cost and the hydrogen economy. (A.L.B.)

  12. Biomolecular Science (Fact Sheet)

    2012-04-01

    A brief fact sheet about NREL Photobiology and Biomolecular Science. The research goal of NREL's Biomolecular Science is to enable cost-competitive advanced lignocellulosic biofuels production by understanding the science critical for overcoming biomass recalcitrance and developing new product and product intermediate pathways. NREL's Photobiology focuses on understanding the capture of solar energy in photosynthetic systems and its use in converting carbon dioxide and water directly into hydrogen and advanced biofuels.

  13. Scalable Prediction of Energy Consumption using Incremental Time Series Clustering

    Simmhan, Yogesh; Noor, Muhammad Usman

    2013-10-09

    Time series datasets are a canonical form of high velocity Big Data, and often generated by pervasive sensors, such as found in smart infrastructure. Performing predictive analytics on time series data can be computationally complex, and requires approximation techniques. In this paper, we motivate this problem using a real application from the smart grid domain. We propose an incremental clustering technique, along with a novel affinity score for determining cluster similarity, which help reduce the prediction error for cumulative time series within a cluster. We evaluate this technique, along with optimizations, using real datasets from smart meters, totaling ~700,000 data points, and show the efficacy of our techniques in improving the prediction error of time series data within polynomial time.

  14. Sheet pinch devices

    Anderson, O.A.; Baker, W.R.; Ise, J. Jr.; Kunkel, W.B.; Pyle, R.V.; Stone, J.M.

    1958-01-01

    Three types of sheet-like discharges are being studied at Berkeley. The first of these, which has been given the name 'Triax', consists of a cylindrical plasma sleeve contained between two coaxial conducting cylinders A theoretical analysis of the stability of the cylindrical sheet plasma predicts the existence of a 'sausage-mode' instability which is, however, expected to grow more slowly than in the case of the unstabilized linear pinch (by the ratio of the radial dimensions). The second pinch device employs a disk shaped discharge with radial current guided between flat metal plates, this configuration being identical to that of the flat hydromagnetic capacitor without external magnetic field. A significant feature of these configurations is the absence of a plasma edge, i.e., there are no regions of sharply curved magnetic field lines anywhere in these discharges. The importance of this fact for stability is not yet fully investigated theoretically. As a third configuration a rectangular, flat pinch tube has been constructed, and the behaviour of a flat plasma sheet with edges is being studied experimentally

  15. Investigation of the Formability of TRIP780 Steel Sheets

    Song, Yang

    The formability of a metal sheet is dependent on its work hardening behaviour and its forming limits; and both aspects must be carefully determined in order to accurately simulate a particular forming process. This research aims to characterize the formability of a TRIP780 sheet steel using advanced experimental testing and analysis techniques. A series of flat rolling and tensile tests, as well as shear tests were conducted to determine the large deformation work hardening behaviour of this TRIP780 steel. Nakazima tests were carried out up to fracture to determine the forming limits of this sheet material. A highly-automated method for generating a robust FLC for sheet materials from DIC strain measurements was created with the help of finite element simulations, and evaluated against the conventional method. A correction algorithm that aims to compensate for the process dependent effects in the Nakazima test was implemented and tested with some success.

  16. Research on Computer Integrated Manufacturing of Sheet Metal Parts for Lithium Battery

    Pan Wei-Min

    2016-01-01

    Full Text Available Lithium battery has been widely used as the main driving force of the new energy vehicle in recent years. Sheet metal parts are formed by means of pressure forming techniques with the characteristics of light weight, small size and high structural strength. The sheet metal forming has higher productivity and material utilization than the mechanical cutting, therefore sheet metal parts are widely used in many fields, such as modern automotive industry, aviation, aerospace, machine tools, instruments and household appliances. In this paper, taking a complex lithium battery box as an example, the integrated manufacturing of sheet metal parts is studied, and the digital integrated design and manufacturing process system is proposed. The technology is studied such as sheet metal design, unfolding, sheet nesting and laser cutting, CNC turret punch stamping programming, CNC bending etc. The feasibility of the method is verified through the examples of products and the integrated manufacturing of sheet metal box is completed.

  17. Forced tearing of ductile and brittle thin sheets.

    Tallinen, T; Mahadevan, L

    2011-12-09

    Tearing a thin sheet by forcing a rigid object through it leads to complex crack morphologies; a single oscillatory crack arises when a tool is driven laterally through a brittle sheet, while two diverging cracks and a series of concertinalike folds forms when a tool is forced laterally through a ductile sheet. On the other hand, forcing an object perpendicularly through the sheet leads to radial petallike tears in both ductile and brittle materials. To understand these different regimes we use a combination of experiments, simulations, and simple theories. In particular, we describe the transition from brittle oscillatory tearing via a single crack to ductile concertina tearing with two tears by deriving laws that describe the crack paths and wavelength of the concertina folds and provide a simple phase diagram for the morphologies in terms of the material properties of the sheet and the relative size of the tool.

  18. Dense sheet Z-pinches

    Tetsu, Miyamoto

    1999-01-01

    The steady state and quasi-steady processes of infinite- and finite-width sheet z-pinches are studied. The relations corresponding to the Bennett relation and Pease-Braginskii current of cylindrical fiber z-pinches depend on a geometrical factor in the sheet z-pinches. The finite-width sheet z-pinch is approximated by a segment of infinite-width sheet z-pinch, if it is wide enough, and corresponds to a number of (width/thickness) times fiber z-pinch plasmas of the diameter that equals the sheet thickness. If the sheet current equals this number times the fiber current, the plasma created in the sheet z-pinches is as dense as in the fiber z-pinches. The total energy of plasma and magnetic field per unit mass is approximately equal in both pinches. Quasi-static transient processes are different in several aspects from the fiber z-pinch. No radiation collapse occurs in the sheet z-pinch. The stability is improved in the sheet z-pinches. The fusion criterions and the experimental arrangements to produce the sheet z-pinches are also discussed. (author)

  19. New directions in the science and technology of advanced sheet explosive formulations and the key energetic materials used in the processing of sheet explosives: Emerging trends.

    Talawar, M B; Jangid, S K; Nath, T; Sinha, R K; Asthana, S N

    2015-12-30

    This review presents the work carried out by the international community in the area of sheet explosive formulations and its applications in various systems. The sheet explosive is also named as PBXs and is a composite material in which solid explosive particles like RDX, HMX or PETN are dispersed in a polymeric matrix, forms a flexible material that can be rolled/cut into sheet form which can be applied to any complex contour. The designed sheet explosive must possess characteristic properties such as flexible, cuttable, water proof, easily initiable, and safe handling. The sheet explosives are being used for protecting tanks (ERA), light combat vehicle and futuristic infantry carrier vehicle from different attacking war heads etc. Besides, sheet explosives find wide applications in demolition of bridges, ships, cutting and metal cladding. This review also covers the aspects such as risks and hazard analysis during the processing of sheet explosive formulations, effect of ageing on sheet explosives, detection and analysis of sheet explosive ingredients and the R&D efforts of Indian researchers in the development of sheet explosive formulations. To the best of our knowledge, there has been no review article published in the literature in the area of sheet explosives. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Incremental passivity and output regulation for switched nonlinear systems

    Pang, Hongbo; Zhao, Jun

    2017-10-01

    This paper studies incremental passivity and global output regulation for switched nonlinear systems, whose subsystems are not required to be incrementally passive. A concept of incremental passivity for switched systems is put forward. First, a switched system is rendered incrementally passive by the design of a state-dependent switching law. Second, the feedback incremental passification is achieved by the design of a state-dependent switching law and a set of state feedback controllers. Finally, we show that once the incremental passivity for switched nonlinear systems is assured, the output regulation problem is solved by the design of global nonlinear regulator controllers comprising two components: the steady-state control and the linear output feedback stabilising controllers, even though the problem for none of subsystems is solvable. Two examples are presented to illustrate the effectiveness of the proposed approach.

  1. Perforation of metal sheets

    Steenstrup, Jens Erik

    simulation is focused on the sheet deformation. However, the effect on the tool and press is included. The process model is based on the upper bound analysis in order to predict the force progress and hole characteristics etc. Parameter analyses are divided into two groups, simulation and experimental tests......The main purposes of this project are:1. Development of a dynamic model for the piercing and performation process2. Analyses of the main parameters3. Establishing demands for process improvements4. Expansion of the existing parameter limitsThe literature survey describes the process influence...

  2. Performance Evaluation of Incremental K-means Clustering Algorithm

    Chakraborty, Sanjay; Nagwani, N. K.

    2014-01-01

    The incremental K-means clustering algorithm has already been proposed and analysed in paper [Chakraborty and Nagwani, 2011]. It is a very innovative approach which is applicable in periodically incremental environment and dealing with a bulk of updates. In this paper the performance evaluation is done for this incremental K-means clustering algorithm using air pollution database. This paper also describes the comparison on the performance evaluations between existing K-means clustering and i...

  3. Towards a multiconfigurational method of increments

    Fertitta, E.; Koch, D.; Paulus, B.; Barcza, G.; Legeza, Ö.

    2018-06-01

    The method of increments (MoI) allows one to successfully calculate cohesive energies of bulk materials with high accuracy, but it encounters difficulties when calculating dissociation curves. The reason is that its standard formalism is based on a single Hartree-Fock (HF) configuration whose orbitals are localised and used for the many-body expansion. In situations where HF does not allow a size-consistent description of the dissociation, the MoI cannot be guaranteed to yield proper results either. Herein, we address the problem by employing a size-consistent multiconfigurational reference for the MoI formalism. This leads to a matrix equation where a coupling derived by the reference itself is employed. In principle, such an approach allows one to evaluate approximate values for the ground as well as excited states energies. While the latter are accurate close to the avoided crossing only, the ground state results are very promising for the whole dissociation curve, as shown by the comparison with density matrix renormalisation group benchmarks. We tested this two-state constant-coupling MoI on beryllium rings of different sizes and studied the error introduced by the constant coupling.

  4. Evolution of cooperation driven by incremental learning

    Li, Pei; Duan, Haibin

    2015-02-01

    It has been shown that the details of microscopic rules in structured populations can have a crucial impact on the ultimate outcome in evolutionary games. So alternative formulations of strategies and their revision processes exploring how strategies are actually adopted and spread within the interaction network need to be studied. In the present work, we formulate the strategy update rule as an incremental learning process, wherein knowledge is refreshed according to one's own experience learned from the past (self-learning) and that gained from social interaction (social-learning). More precisely, we propose a continuous version of strategy update rules, by introducing the willingness to cooperate W, to better capture the flexibility of decision making behavior. Importantly, the newly gained knowledge including self-learning and social learning is weighted by the parameter ω, establishing a strategy update rule involving innovative element. Moreover, we quantify the macroscopic features of the emerging patterns to inspect the underlying mechanisms of the evolutionary process using six cluster characteristics. In order to further support our results, we examine the time evolution course for these characteristics. Our results might provide insights for understanding cooperative behaviors and have several important implications for understanding how individuals adjust their strategies under real-life conditions.

  5. Computer-readable ''Nuclear Data Sheets''

    Ewbank, W.B.

    1975-01-01

    The evaluated nuclear structure data contained in ''Nuclear Data Sheets'' are available in computer-readable form. Experimentally established properties of nuclear levels are included as well as radiations from nuclear reactions and radioactive decay. Portions of the data can be selected for distribution in several formats on magnetic tape or computer cards. A variety of different listing and drawing formats are also available. 4 figures

  6. Single sheet metal oxides and hydroxides

    Huang, Lizhi

    The synthesis of layered double hydroxides (LDHs) provides a relatively easy and traditional way to build versatile chemical compounds with a rough control of the bulk structure. The delamination of LDHs to form their single host layers (2D nanosheets) and the capability to reassemble them offer......) Delamination of the LDHs structure (oxGRC12) with the formation of single sheet iron (hydr)oxide (SSI). (3) Assembly of the new 2D nanosheets layer by layer to achieve desired functionalities....

  7. Power variation for Gaussian processes with stationary increments

    Barndorff-Nielsen, Ole Eiler; Corcuera, J.M.; Podolskij, Mark

    2009-01-01

    We develop the asymptotic theory for the realised power variation of the processes X=•G, where G is a Gaussian process with stationary increments. More specifically, under some mild assumptions on the variance function of the increments of G and certain regularity conditions on the path of the pr......We develop the asymptotic theory for the realised power variation of the processes X=•G, where G is a Gaussian process with stationary increments. More specifically, under some mild assumptions on the variance function of the increments of G and certain regularity conditions on the path...... a chaos representation....

  8. Experiments on sheet metal shearing

    Gustafsson, Emil

    2013-01-01

    Within the sheet metal industry, different shear cutting technologies are commonly used in several processing steps, e.g. in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material.Numerical models to predict forces and sheared edge geometry for different sheet metal grades and different shear parameter set-ups a...

  9. On the structure of the magnetotail current sheet

    Ashour-Abdalla, M.; Peroomian, V.; Richard, R.L.; Zelenyi, L.M.

    1993-01-01

    Results from modeling ion distribution functions in a two-dimensional reduction of the Tsyganenko magnetic field model have enabled the authors to calculate the full ion pressure tensor inside the model magnetotail. A thin current sheet is formed in the distant tail and the pressure tensor within this sheet has significant off-diagonal terms. These terms resulting from quasiadiabatic ion trajectories create azimuthally asymmetric distribution functions which are capable of maintaining stress-balance. Outside the current sheet the off-diagonal terms disappear and moderate anisotropy builds up with P perpendicular/P parallel ∼ 0.8. Closer to the Earth rapid isotropization of the distribution occurs

  10. New technology for the production of magnesium strips and sheets

    R. Kawalla

    2008-07-01

    Full Text Available A new production technology for magnesium strip, based on twin-roll-casting and strip rolling was developed in Freiberg Germany. By means of this economic method it is possible to produce strips in deep drawing quality with good forming properties in order to satisfy the request for low cost Mg sheets in the automotive and electronic industry. Both, coils as single sheets, were manufactured and rolled to a thickness of 1mm(0,5 mm. The technology of the new process and the properties of the twin-roll-casted material and the final sheets are presented.

  11. Top-down attention based on object representation and incremental memory for knowledge building and inference.

    Kim, Bumhwi; Ban, Sang-Woo; Lee, Minho

    2013-10-01

    Humans can efficiently perceive arbitrary visual objects based on an incremental learning mechanism with selective attention. This paper proposes a new task specific top-down attention model to locate a target object based on its form and color representation along with a bottom-up saliency based on relativity of primitive visual features and some memory modules. In the proposed model top-down bias signals corresponding to the target form and color features are generated, which draw the preferential attention to the desired object by the proposed selective attention model in concomitance with the bottom-up saliency process. The object form and color representation and memory modules have an incremental learning mechanism together with a proper object feature representation scheme. The proposed model includes a Growing Fuzzy Topology Adaptive Resonance Theory (GFTART) network which plays two important roles in object color and form biased attention; one is to incrementally learn and memorize color and form features of various objects, and the other is to generate a top-down bias signal to localize a target object by focusing on the candidate local areas. Moreover, the GFTART network can be utilized for knowledge inference which enables the perception of new unknown objects on the basis of the object form and color features stored in the memory during training. Experimental results show that the proposed model is successful in focusing on the specified target objects, in addition to the incremental representation and memorization of various objects in natural scenes. In addition, the proposed model properly infers new unknown objects based on the form and color features of previously trained objects. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Enthalpy-increment measurements for CsI(s) and Cs2CrO4(s) by high-temperature Calvet calorimetry

    Venugopal, V.; Agarwal, R.; Roy, K.N.; Prasad, R.; Sood, D.D.

    1987-01-01

    Molar thermodynamic properties of CsI(s) and Cs 2 Cr O 4 (s) have been evaluated by enthalpy-increment measurements, using a Calvet high-temperature calorimeter. Least squares analyses were performed on the enthalpy increment results. Data is presented in tabular form for the dependence of enthalpy increments on temperature, in the range 333 to 822 K, for both caesium compounds, along with the thermal properties of the compounds. Good agreement is found between the present data and previously reported results on reduced enthalpy increments of CsI(s) and Cs 2 CrO 4 (s). (U.K.)

  13. Application of Hydroforming Process in Sheet Metal Formation

    GRIZELJ, Branko; CUMIN, Josip; ERGIĆ, Todor

    2009-01-01

    This article deals with the theory and application of a hydroforming process. Nowadays automobile manufacturers use high strength sheet metal plates. This high strength steel sheet metal plates are strain hardened in the process of metal forming. With the use of high strength steel, cars are made lightweight, which is intended for low fuel consumption because of high energy prices. Some examples of application of a hydroforming process are simulated with FEM.

  14. FeCoNi coated glass fibers in composite sheets for electromagnetic absorption and shielding behaviors

    Lee, Joonsik; Jung, Byung Mun; Lee, Sang Bok; Lee, Sang Kwan; Kim, Ki Hyeon

    2017-09-01

    To evaluate the electromagnetic (EM) absorption and shield of magnetic composite sheet, we prepared the FeCoNi coated glass fibers filled in composite sheet. The FeCoNi was coated by electroless plating on glass fiber as a filler. The coated FeCoNi found that consist of mixtures of bcc and fcc phase. The magnetization and coercivity of coated FeCoNi are about 110 emu/g and 57 Oe, respectively. The permittivity and permeability of the FeCoNi composite sheet were about 21 and 1, respectively. Power absorption increased 95% with the increment of frequency up to 10 GHz. Inter-decoupling of this composite sheet showed maximum 30 dB at around 5.3 GHz, which is comparable to that of a conductive Cu foil. Shielding effectiveness (SE) was measured by using rectangular waveguide method. SE of composite obtained about 37 dB at X-band frequency region.

  15. Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

    Gabriel Centeno

    2017-11-01

    Full Text Available Single Point Incremental Forming (SPIF is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows stable plastic deformation well above the conventional forming limits, as this enhanced formability is only achievable within a certain range of process parameters depending on the material type. This paper analyzes formability and failure of AISI304-H111 sheets deformed by SPIF compared to conventional testing conditions (including Nakazima and stretch-bending tests. With this purpose, experimental tests in SPIF and stretch-bending were carried out and a numerical model of SPIF is performed. The results allow the authors to establish the following contributions regarding SPIF: (i the setting of the limits of the formability enhancement when small tool diameters are used, (ii the evolution of the crack when failure is attained and (iii the determination of the conditions upon which necking is suppressed, leading directly to ductile fracture in SPIF.

  16. One Step at a Time: SBM as an Incremental Process.

    Conrad, Mark

    1995-01-01

    Discusses incremental SBM budgeting and answers questions regarding resource equity, bookkeeping requirements, accountability, decision-making processes, and purchasing. Approaching site-based management as an incremental process recognizes that every school system engages in some level of site-based decisions. Implementation can be gradual and…

  17. Defense Agencies Initiative Increment 2 (DAI Inc 2)

    2016-03-01

    module. In an ADM dated September 23, 2013, the MDA established Increment 2 as a MAIS program to include budget formulation; grants financial...2016 Major Automated Information System Annual Report Defense Agencies Initiative Increment 2 (DAI Inc 2) Defense Acquisition Management...President’s Budget RDT&E - Research, Development, Test, and Evaluation SAE - Service Acquisition Executive TBD - To Be Determined TY - Then

  18. Incrementality in naming and reading complex numerals: Evidence from eyetracking

    Korvorst, M.H.W.; Roelofs, A.P.A.; Levelt, W.J.M.

    2006-01-01

    Individuals speak incrementally when they interleave planning and articulation. Eyetracking, along with the measurement of speech onset latencies, can be used to gain more insight into the degree of incrementality adopted by speakers. In the current article, two eyetracking experiments are reported

  19. Lifetime costs of lung transplantation : Estimation of incremental costs

    VanEnckevort, PJ; Koopmanschap, MA; Tenvergert, EM; VanderBij, W; Rutten, FFH

    1997-01-01

    Despite an expanding number of centres which provide lung transplantation, information about the incremental costs of lung transplantation is scarce. From 1991 until 1995, in The Netherlands a technology assessment was performed which provided information about the incremental costs of lung

  20. Finance for incremental housing: current status and prospects for expansion

    Ferguson, B.; Smets, P.G.S.M.

    2010-01-01

    Appropriate finance can greatly increase the speed and lower the cost of incremental housing - the process used by much of the low/moderate-income majority of most developing countries to acquire shelter. Informal finance continues to dominate the funding of incremental housing. However, new sources

  1. Validation of the periodicity of growth increment deposition in ...

    Validation of the periodicity of growth increment deposition in otoliths from the larval and early juvenile stages of two cyprinids from the Orange–Vaal river ... Linear regression models were fitted to the known age post-fertilisation and the age estimated using increment counts to test the correspondence between the two for ...

  2. 76 FR 53763 - Immigration Benefits Business Transformation, Increment I

    2011-08-29

    ..., 100, et al. Immigration Benefits Business Transformation, Increment I; Final Rule #0;#0;Federal... Benefits Business Transformation, Increment I AGENCY: U.S. Citizenship and Immigration Services, DHS... USCIS is engaged in an enterprise-wide transformation effort to implement new business processes and to...

  3. The Time Course of Incremental Word Processing during Chinese Reading

    Zhou, Junyi; Ma, Guojie; Li, Xingshan; Taft, Marcus

    2018-01-01

    In the current study, we report two eye movement experiments investigating how Chinese readers process incremental words during reading. These are words where some of the component characters constitute another word (an embedded word). In two experiments, eye movements were monitored while the participants read sentences with incremental words…

  4. On conditional scalar increment and joint velocity-scalar increment statistics

    Zhang Hengbin; Wang Danhong; Tong Chenning

    2004-01-01

    Conditional velocity and scalar increment statistics are usually studied in the context of Kolmogorov's refined similarity hypotheses and are considered universal (quasi-Gaussian) for inertial-range separations. In such analyses the locally averaged energy and scalar dissipation rates are used as conditioning variables. Recent studies have shown that certain local turbulence structures can be captured when the local scalar variance (φ 2 ) r and the local kinetic energy k r are used as the conditioning variables. We study the conditional increments using these conditioning variables, which also provide the local turbulence scales. Experimental data obtained in the fully developed region of an axisymmetric turbulent jet are used to compute the statistics. The conditional scalar increment probability density function (PDF) conditional on (φ 2 ) r is found to be close to Gaussian for (φ 2 ) r small compared with its mean and is sub-Gaussian and bimodal for large (φ 2 ) r , and therefore is not universal. We find that the different shapes of the conditional PDFs are related to the instantaneous degree of non-equilibrium (production larger than dissipation) of the local scalar. There is further evidence of this from the conditional PDF conditional on both (φ 2 ) r and χ r , which is largely a function of (φ 2 ) r /χ r , a measure of the degree of non-equilibrium. The velocity-scalar increment joint PDF is close to joint Gaussian and quad-modal for equilibrium and non-equilibrium local velocity and scalar, respectively. The latter shape is associated with a combination of the ramp-cliff and plane strain structures. Kolmogorov's refined similarity hypotheses also predict a dependence of the conditional PDF on the degree of non-equilibrium. Therefore, the quasi-Gaussian (joint) PDF, previously observed in the context of Kolmogorov's refined similarity hypotheses, is only one of the conditional PDF shapes of inertial range turbulence. The present study suggests that

  5. Soft Costs Fact Sheet

    None

    2016-05-01

    This fact sheet is an overview of the systems integration subprogram at the U.S. Department of Energy SunShot Initiative. Soft costs can vary significantly as a result of a fragmented energy marketplace. In the U.S., there are 18,000 jurisdictions and 3,000 utilities with different rules and regulations for how to go solar. The same solar equipment may vary widely in its final installation price due to process and market variations across jurisdictions, creating barriers to rapid industry growth. SunShot supports the development of innovative solutions that enable communities to build their local economies and establish clean energy initiatives that meet their needs, while at the same time creating sustainable solar market conditions.

  6. Photovoltaics Fact Sheet

    None

    2016-02-01

    This fact sheet is an overview of the Photovoltaics (PV) subprogram at the U.S. Department of Energy SunShot Initiative. The U.S. Department of Energy (DOE)’s Solar Energy Technologies Office works with industry, academia, national laboratories, and other government agencies to advance solar PV, which is the direct conversion of sunlight into electricity by a semiconductor, in support of the goals of the SunShot Initiative. SunShot supports research and development to aggressively advance PV technology by improving efficiency and reliability and lowering manufacturing costs. SunShot’s PV portfolio spans work from early-stage solar cell research through technology commercialization, including work on materials, processes, and device structure and characterization techniques.

  7. Systems Integration Fact Sheet

    None

    2016-06-01

    This fact sheet is an overview of the Systems Integration subprogram at the U.S. Department of Energy SunShot Initiative. The Systems Integration subprogram enables the widespread deployment of safe, reliable, and cost-effective solar energy technologies by addressing the associated technical and non-technical challenges. These include timely and cost-effective interconnection procedures, optimal system planning, accurate prediction of solar resources, monitoring and control of solar power, maintaining grid reliability and stability, and many more. To address the challenges associated with interconnecting and integrating hundreds of gigawatts of solar power onto the electricity grid, the Systems Integration program funds research, development, and demonstration projects in four broad, interrelated focus areas: grid performance and reliability, dispatchability, power electronics, and communications.

  8. Hyperspectral light sheet microscopy

    Jahr, Wiebke; Schmid, Benjamin; Schmied, Christopher; Fahrbach, Florian O.; Huisken, Jan

    2015-09-01

    To study the development and interactions of cells and tissues, multiple fluorescent markers need to be imaged efficiently in a single living organism. Instead of acquiring individual colours sequentially with filters, we created a platform based on line-scanning light sheet microscopy to record the entire spectrum for each pixel in a three-dimensional volume. We evaluated data sets with varying spectral sampling and determined the optimal channel width to be around 5 nm. With the help of these data sets, we show that our setup outperforms filter-based approaches with regard to image quality and discrimination of fluorophores. By spectral unmixing we resolved overlapping fluorophores with up to nanometre resolution and removed autofluorescence in zebrafish and fruit fly embryos.

  9. Settlement during vibratory sheet piling

    Meijers, P.

    2007-01-01

    During vibratory sheet piling quite often the soil near the sheet pile wall will settle. In many cases this is not a problem. For situations with houses, pipelines, roads or railroads at relative short distance these settlements may not be acceptable. The purpose of the research described in this

  10. Assembly for testing weldability of sheet metal

    David, S.A.; Woodhouse, J.J.

    1985-01-01

    A test assembly for determining the weldability of sheet metal includes a base having a flat side surface with an annular groove in the side surface, a counterbore being formed in the outer wall of the groove and the surface portion of the base circumscribed by the inner wall of the groove being substantially coplanar with the bottom of the counterbore, a test disk of sheet metal the periphery of which is positioned in the counterbore and the outer surface of which is coplanar with one side of the base, and a clamp ring overlying the side surface of the base and the edge portion of the test disk and a plurality of clamp screws which extend through the clamp ring for holding the periphery of the test disk against the bottom of the counterbore

  11. Predicting Hot Deformation of AA5182 Sheet

    Lee, John T.; Carpenter, Alexander J.; Jodlowski, Jakub P.; Taleff, Eric M.

    Aluminum 5000-series alloy sheet materials exhibit substantial ductilities at hot and warm temperatures, even when grain size is not particularly fine. The relatively high strain-rate sensitivity exhibited by these non-superplastic materials, when deforming under solute-drag creep, is a primary contributor to large tensile ductilities. This active deformation mechanism influences both plastic flow and microstructure evolution across conditions of interest for hot- and warm-forming. Data are presented from uniaxial tensile and biaxial bulge tests of AA5182 sheet material at elevated temperatures. These data are used to construct a material constitutive model for plastic flow, which is applied in finite-element-method (FEM) simulations of plastic deformation under multiaxial stress states. Simulation results are directly compared against experimental data to explore the usefulness of this constitutive model. The effects of temperature and stress state on plastic response and microstructure evolution are discussed.

  12. Incremental Validity of Test Session and Classroom Observations in a Multimethod Assessment of Attention Deficit/Hyperactivity Disorder

    McConaughy, Stephanie H.; Harder, Valerie S.; Antshel, Kevin M.; Gordon, Michael; Eiraldi, Ricardo; Dumenci, Levent

    2010-01-01

    This study tested the incremental validity of behavioral observations, over and above parent and teacher reports, for assessing symptoms of Attention Deficit/Hyperactivity Disorder (ADHD) in children ages 6 to 12, using the Test Observation Form (TOF) and Direct Observation Form (DOF) from the Achenbach System of Empirically Based Assessment. The…

  13. Efficiency of Oral Incremental Rehearsal versus Written Incremental Rehearsal on Students' Rate, Retention, and Generalization of Spelling Words

    Garcia, Dru; Joseph, Laurice M.; Alber-Morgan, Sheila; Konrad, Moira

    2014-01-01

    The purpose of this study was to examine the efficiency of an incremental rehearsal oral versus an incremental rehearsal written procedure on a sample of primary grade children's weekly spelling performance. Participants included five second and one first grader who were in need of help with their spelling according to their teachers. An…

  14. Behavior of protruding lateral plane graphene sheets in liquid dodecane: molecular dynamics simulations

    Chen, Shenghui; Sun, Shuangqing, E-mail: sunshuangqing@upc.edu.cn; Li, Chunling [China University of Petroleum (East China), College of Science (China); Pittman, Charles U. [Mississippi State University, Department of Chemistry (United States); Lacy, Thomas E. [Mississippi State University, Department of Aerospace Engineering (United States); Hu, Songqing, E-mail: songqinghu@upc.edu.cn [China University of Petroleum (East China), College of Science (China); Gwaltney, Steven R. [Mississippi State University, Department of Chemistry (United States)

    2016-11-15

    Molecular dynamics simulations are used to investigate the behavior of two parallel graphene sheets fixed on one edge (lateral plane) in liquid dodecane. The interactions of these sheets and dodecane molecules are studied with different starting inter-sheet distances. The structure of the dodecane solvent is also analyzed. The results show that when the distance between the two graphene sheets is short (less than 6.8 Å), the sheets will expel the dodecane molecules between them and stack together. However, when the distance between two sheets is large (greater than 10.2 Å), the two sheets do not come together, and the dodecane molecules will form ordered layers in the interlayer spacing. The equilibrium distance between the graphene sheets can only take on specific discrete values (3.4, 7.8, and 12.1 Å), because only an integer number of dodecane layers forms between the two sheets. Once the graphene sheets are in contact, they remain in contact; the sheets do not separate to allow dodecane into the interlayer spacing.

  15. Vitamin and Mineral Supplement Fact Sheets

    ... website Submit Search NIH Office of Dietary Supplements Vitamin and Mineral Supplement Fact Sheets Search the list ... Supplements: Background Information Botanical Dietary Supplements: Background Information Vitamin and Mineral Fact Sheets Botanical Supplement Fact Sheets ...

  16. Plasma sheet behavior during substorms

    Hones, E.W. Jr.

    1983-01-01

    Auroral or magnetic substorms are periods of enhanced auroral and geomagnetic activity lasting one to a few hours that signify increased dissipation of energy from the magnetosphere to the earth. Data acquired during the past decade from satellites in the near-earth sector of the magnetotail have suggested that during a substorm part of the plasma sheet is severed from earth by magnetic reconnection, forming a plasmoid, i.e., a body of plasma and closed magnetic loops, that flows out of the tail into the solar wind, thus returning plasma and energy that have earlier been accumulated from the solar wind. Very recently this picture has been dramatically confirmed by observations, with the ISEE 3 spacecraft in the magnetotail 220 R/sub E/ from earth, of plasmoids passing that location in clear delayed response to substorms. It now appears that plasmoid release is a fundamental process whereby the magnetosphere gives up excess stored energy and plasma, much like comets are seen to do, and that the phenomena of the substorm seen at earth are a by-product of that fundamental process

  17. Teaching Form as Form

    Keiding, Tina Bering

    2012-01-01

    understanding of form per se, or, to use an expression from this text, of form as form. This challenge can be reduced to one question: how can design teaching support students in achieving not only the ability to recognize and describe different form-related concepts in existing design (i.e. analytical...

  18. Innovative forming and fabrication technologies : new opportunities.

    Davis, B.; Hryn, J.; Energy Systems; Kingston Process Metallurgy, Inc.

    2008-01-31

    The advent of light metal alloys and advanced materials (polymer, composites, etc.) have brought the possibility of achieving important energy reductions into the full life cycle of these materials, especially in transportation applications. 1 These materials have gained acceptance in the aerospace industry but use of light metal alloys needs to gain wider acceptance in other commercial transportation areas. Among the main reasons for the relatively low use of these materials are the lack of manufacturability, insufficient mechanical properties, and increased material costs due to processing inefficiencies. Considering the enormous potential energy savings associated with the use of light metal alloys and advanced materials in transportation, there is a need to identify R&D opportunities in the fields of materials fabrication and forming aimed at developing materials with high specific mechanical properties combined with energy efficient processes and good manufacturability. This report presents a literature review of the most recent developments in the areas of fabrication and metal forming focusing principally on aluminum alloys. In the first section of the document, the different sheet manufacturing technologies including direct chill (DC) casting and rolling, spray forming, spray rolling, thin slab, and strip casting are reviewed. The second section of the document presents recent research on advanced forming processes. The various forming processes reviewed are: superplastic forming, electromagnetic forming, age forming, warm forming, hydroforming, and incremental forming. Optimization of conventional forming processes is also discussed. Potentially interesting light metal alloys for high structural efficiency including aluminum-scandium, aluminum-lithium, magnesium, titanium, and amorphous metal alloys are also reviewed. This section concludes with a discussion on alloy development for manufacturability. The third section of the document reviews the latest

  19. Synthesis and characterization of large WO{sub 3} sheets synthesized by resistive heating method

    Filippo, Emanuela, E-mail: emanuela.filippo@unisalento.it [Department of Engineering for Innovation, University of Salento, Monteroni Street, Lecce I-73100 Italy (Italy); Tepore, Marco [Department of Engineering for Innovation, University of Salento, Monteroni Street, Lecce I-73100 Italy (Italy); Baldassarre, Francesca [Department of Cultural Heritage, University of Salento, Lecce I-73100 Italy (Italy); Quarta, Gianluca; Calcagnile, Lucio [Department of Engineering for Innovation, University of Salento, Monteroni Street, Lecce I-73100 Italy (Italy); Guascito, Maria Rachele [DiSTeBA, University of Salento, Lecce I-73100 Italy (Italy); Tepore, Antonio [Department of Cultural Heritage, University of Salento, Lecce I-73100 Italy (Italy)

    2015-09-01

    A simple, low-cost method is presented to grow tungsten oxide large sheets simply by resistively heating a pure tungsten filament under air/water vapor flow. The obtained structures were studied using scanning and transmission electron microscopy, selected area diffraction, X Ray diffraction, Raman and X-ray photoelectron spectroscopy, photoluminescence and zeta potential measurements. SEM observations revealed that sheets formed by broadening of the wires/belts over longer growth period. Photoluminescence measurements showed that tungsten oxide sheets had an intense visible emission band. - Highlights: • WO{sub 3} large sheets were prepared by resistively heating a W filament. • WO{sub 3} sheets were carefully characterized. • Formation mechanism of sheets was studied. • WO{sub 3} sheets had an intense visible emission band at 462 nm.

  20. Incremental Tensor Principal Component Analysis for Handwritten Digit Recognition

    Chang Liu

    2014-01-01

    Full Text Available To overcome the shortcomings of traditional dimensionality reduction algorithms, incremental tensor principal component analysis (ITPCA based on updated-SVD technique algorithm is proposed in this paper. This paper proves the relationship between PCA, 2DPCA, MPCA, and the graph embedding framework theoretically and derives the incremental learning procedure to add single sample and multiple samples in detail. The experiments on handwritten digit recognition have demonstrated that ITPCA has achieved better recognition performance than that of vector-based principal component analysis (PCA, incremental principal component analysis (IPCA, and multilinear principal component analysis (MPCA algorithms. At the same time, ITPCA also has lower time and space complexity.

  1. Selectively reflective transparent sheets

    Waché, Rémi; Florescu, Marian; Sweeney, Stephen J.; Clowes, Steven K.

    2015-08-01

    We investigate the possibility to selectively reflect certain wavelengths while maintaining the optical properties on other spectral ranges. This is of particular interest for transparent materials, which for specific applications may require high reflectivity at pre-determined frequencies. Although there exist currently techniques such as coatings to produce selective reflection, this work focuses on new approaches for mass production of polyethylene sheets which incorporate either additives or surface patterning for selective reflection between 8 to 13 μ m. Typical additives used to produce a greenhouse effect in plastics include particles such as clays, silica or hydroxide materials. However, the absorption of thermal radiation is less efficient than the decrease of emissivity as it can be compared with the inclusion of Lambertian materials. Photonic band gap engineering by the periodic structuring of metamaterials is known in nature for producing the vivid bright colors in certain organisms via strong wavelength-selective reflection. Research to artificially engineer such structures has mainly focused on wavelengths in the visible and near infrared. However few studies to date have been carried out to investigate the properties of metastructures in the mid infrared range even though the patterning of microstructure is easier to achieve. We present preliminary results on the diffuse reflectivity using FDTD simulations and analyze the technical feasibility of these approaches.

  2. Reconstructing the last Irish Ice Sheet 2: a geomorphologically-driven model of ice sheet growth, retreat and dynamics

    Greenwood, Sarah L.; Clark, Chris D.

    2009-12-01

    The ice sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and ice-marginal dynamics and chronologies, with less attention paid to an ice sheet wide view of the first order properties of the ice sheet: centres of mass, ice divide structure, ice flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an ice sheet reconstruction yielding these fundamental ice sheet properties. We present a seven stage model of ice sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of ice from Scotland likely coalesced with local ice caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish Ice Sheet was then established during ice sheet growth, with a branching ice divide structure whose main axis migrated up to 140 km from the west coast towards the east. Ice stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. Ice cover is reconstructed as extending to the continental shelf break. The Irish Ice Sheet became autonomous (i.e. separate from the British Ice Sheet) during deglaciation and fragmented into multiple ice masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the ice sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the ice stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid

  3. Superfund fact sheet: The remedial program. Fact sheet

    1992-09-01

    The fact sheet describes what various actions the EPA can take to clean up hazardous wastes sites. Explanations of how the criteria for environmental and public health risk assessment are determined and the role of state and local governments in site remediation are given. The fact sheet is one in a series providing reference information about Superfund issues and is intended for readers with no formal scientific training

  4. Substorms in the Inner Plasma Sheet

    Le Contel, O.; Perraut, S.; Roux, A.; Pellat, R.; Korth, A.

    Thin Current Sheets (TCS) are regularly formed prior to substorm breakup, even in the near-Earth plasma sheet, as close as the geostationary orbit. A self-consistent kinetic theory describing the response of the plasma sheet to an electromagnetic perturbation is given. This perturbation corresponds to an external forcing, for instance caused by the solar wind (not an internal instability). The equilibrium of the configuration of this TCS in the presence of a time varying perturbation is shown to produce a strong parallel thermal anisotropy (T∥ > T⊺) of energetic electrons and ions (E>50keV) as well as an enhanced diamagnetic current carried by low energy ions (Ecurrents tend to enhance the confinement of this current sheet near the magnetic equator. These results are compared with data gathered by GEOS-2 at the geostationary orbit, where the magnetic signatures of TCS, and parallel anisotropies are regularly observed prior to breakup. By ensuring quasi-neutrality everywhere we find, when low frequency electromagnetic perturbations are applied, that although the magnetic field line remains an equipotential to the lowest order in Te/Ti, a field-aligned potential drop exists to the next order in (Te/Ti). Thus the development of a TCS implies the formation of a field-aligned potential drop (~= few hundred volts) to ensure the quasi-neutrality everywhere. For an earthward directed pressure gradient, a field-aligned electric field, directed towards the ionosphere, is obtained, on the western edge of the perturbation (i.e. western edge of the current sheet). Thus field aligned beams of electrons are expected to flow towards the equatorial region on the western edge of the current sheet. We study the stability of these electron beams and show that they are unstable to ``High Frequency'' (HF) waves. These ``HF'' waves are regularly observed at frequencies of the order of the proton gyrofrequency (fH+) just before, or at breakup. The amplitude of these HF waves is so

  5. An application of the J-integral to an incremental analysis of blunting crack behavior

    Merkle, J.G.

    1989-01-01

    This paper describes an analytical approach to estimating the elastic-plastic stresses and strains near the tip of a blunting crack with a finite root radius. Rice's original derivation of the path independent J-integral considered the possibility of a finite crack tip root radius. For this problem Creager's elastic analysis gives the relation between the stress intensity factor K I and the near tip stresses. It can be shown that the relation K I 2 = E'J holds when the root radius is finite. Recognizing that elastic-plastic behavior is incrementally linear then allows a derivation to be performed for a bielastic specimen having a crack tip region of reduced modulus, and the result differentiated to estimate elastic-plastic behavior. The result is the incremental form of Neuber's equation. This result does not require the assumption of any particular stress-strain relation. However by assuming a pure power law stress-strain relation and using Ilyushin's principle, the ordinary deformation theory form of Neuber's equation, K σ K var epsilon = K t 2 , is obtained. Applications of the incremental form of Neuber's equation have already been made to fatigue and fracture analysis. This paper helps to provide a theoretical basis for these methods previously considered semiempirical. 26 refs., 4 figs

  6. Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet

    Azizah Intan Pangesty

    2016-06-01

    Full Text Available A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone (PLCL sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo.

  7. Parallel Algorithm for Incremental Betweenness Centrality on Large Graphs

    Jamour, Fuad Tarek; Skiadopoulos, Spiros; Kalnis, Panos

    2017-01-01

    : they either require excessive memory (i.e., quadratic to the size of the input graph) or perform unnecessary computations rendering them prohibitively slow. We propose iCentral; a novel incremental algorithm for computing betweenness centrality in evolving

  8. Incremental Frequent Subgraph Mining on Large Evolving Graphs

    Abdelhamid, Ehab; Canim, Mustafa; Sadoghi, Mohammad; Bhatta, Bishwaranjan; Chang, Yuan-Chi; Kalnis, Panos

    2017-01-01

    , such as social networks, utilize large evolving graphs. Mining these graphs using existing techniques is infeasible, due to the high computational cost. In this paper, we propose IncGM+, a fast incremental approach for continuous frequent subgraph mining problem

  9. Increment and mortality in a virgin Douglas-fir forest.

    Robert W. Steele; Norman P. Worthington

    1955-01-01

    Is there any basis to the forester's rule of thumb that virgin forests eventually reach an equilibrium where increment and mortality approximately balance? Are we wasting potential timber volume by failing to salvage mortality in old-growth stands?

  10. 2012 Swimming Season Fact Sheets

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  11. State Fact Sheets on COPD

    ... Submit Search The CDC Chronic Obstructive Pulmonary Disease (COPD) Note: Javascript is disabled or is not supported ... message, please visit this page: About CDC.gov . COPD Homepage Data and Statistics Fact Sheets Publications Publications ...

  12. Shear flow generation and transport barrier formation on rational surface current sheets in tokamaks

    Wang Xiaogang; Xiao Chijie; Wang Jiaqi

    2009-01-01

    Full text: A thin current sheet with a magnetic field component in the same direction can form the electrical field perpendicularly pointing to the sheet, therefore an ExB flow with a strong shear across the current sheet. An electrical potential well is also found on the rational surface of RFP as well as the neutral sheet of the magnetotail with the E-field pointing to the rational (neutral) surface. Theoretically, a current singularity is found to be formed on the rational surface in ideal MHD. It is then very likely that the sheet current on the rational surfaces will generate the electrical potential well in its vicinity so the electrical field pointing to the sheet. It results in an ExB flow with a strong shear in the immediate neighborhood of the rational surface. It may be the cause of the transport barrier often seen near the low (m, n) rational surfaces with MHD signals. (author)

  13. Mission Planning System Increment 5 (MPS Inc 5)

    2016-03-01

    2016 Major Automated Information System Annual Report Mission Planning System Increment 5 (MPS Inc 5) Defense Acquisition Management Information...President’s Budget RDT&E - Research, Development, Test, and Evaluation SAE - Service Acquisition Executive TBD - To Be Determined TY - Then Year...Phone: 845-9625 DSN Fax: Date Assigned: May 19, 2014 Program Information Program Name Mission Planning System Increment 5 (MPS Inc 5) DoD

  14. Shredder: GPU-Accelerated Incremental Storage and Computation

    Bhatotia, Pramod; Rodrigues, Rodrigo; Verma, Akshat

    2012-01-01

    Redundancy elimination using data deduplication and incremental data processing has emerged as an important technique to minimize storage and computation requirements in data center computing. In this paper, we present the design, implementation and evaluation of Shredder, a high performance content-based chunking framework for supporting incremental storage and computation systems. Shredder exploits the massively parallel processing power of GPUs to overcome the CPU bottlenecks of content-ba...

  15. On the instability increments of a stationary pinch

    Bud'ko, A.B.

    1989-01-01

    The stability of stationary pinch to helical modes is numerically studied. It is shown that in the case of a rather fast plasma pressure decrease to the pinch boundary, for example, for an isothermal diffusion pinch with Gauss density distribution instabilities with m=0 modes are the most quickly growing. Instability increments are calculated. A simple analytical expression of a maximum increment of growth of sausage instability for automodel Gauss profiles is obtained

  16. Biometrics Enabling Capability Increment 1 (BEC Inc 1)

    2016-03-01

    modal biometrics submissions to include iris, face, palm and finger prints from biometrics collection devices, which will support the Warfighter in...2016 Major Automated Information System Annual Report Biometrics Enabling Capability Increment 1 (BEC Inc 1) Defense Acquisition Management...Phone: 227-3119 DSN Fax: Date Assigned: July 15, 2015 Program Information Program Name Biometrics Enabling Capability Increment 1 (BEC Inc 1) DoD

  17. The Dark Side of Malleability: Incremental Theory Promotes Immoral Behaviors

    Huang, Niwen; Zuo, Shijiang; Wang, Fang; Cai, Pan; Wang, Fengxiang

    2017-01-01

    Implicit theories drastically affect an individual’s processing of social information, decision making, and action. The present research focuses on whether individuals who hold the implicit belief that people’s moral character is fixed (entity theorists) and individuals who hold the implicit belief that people’s moral character is malleable (incremental theorists) make different choices when facing a moral decision. Incremental theorists are less likely to make the fundamental attribution err...

  18. A Syntactic-Semantic Approach to Incremental Verification

    Bianculli, Domenico; Filieri, Antonio; Ghezzi, Carlo; Mandrioli, Dino

    2013-01-01

    Software verification of evolving systems is challenging mainstream methodologies and tools. Formal verification techniques often conflict with the time constraints imposed by change management practices for evolving systems. Since changes in these systems are often local to restricted parts, an incremental verification approach could be beneficial. This paper introduces SiDECAR, a general framework for the definition of verification procedures, which are made incremental by the framework...

  19. Logistics Modernization Program Increment 2 (LMP Inc 2)

    2016-03-01

    Sections 3 and 4 of the LMP Increment 2 Business Case, ADM), key functional requirements, Critical Design Review (CDR) Reports, and Economic ...from the 2013 version of the LMP Increment 2 Economic Analysis and replace it with references to the Economic Analysis that will be completed...of ( inbound /outbound) IDOCs into the system. LMP must be able to successfully process 95% of ( inbound /outbound) IDOCs into the system. Will meet

  20. Organization Strategy and Structural Differences for Radical Versus Incremental Innovation

    John E. Ettlie; William P. Bridges; Robert D. O'Keefe

    1984-01-01

    The purpose of this study was to test a model of the organizational innovation process that suggests that the strategy-structure causal sequence is differentiated by radical versus incremental innovation. That is, unique strategy and structure will be required for radical innovation, especially process adoption, while more traditional strategy and structure arrangements tend to support new product introduction and incremental process adoption. This differentiated theory is strongly supported ...

  1. Incremental Learning for Place Recognition in Dynamic Environments

    Luo, Jie; Pronobis, Andrzej; Caputo, Barbara; Jensfelt, Patric

    2007-01-01

    This paper proposes a discriminative approach to template-based Vision-based place recognition is a desirable feature for an autonomous mobile system. In order to work in realistic scenarios, visual recognition algorithms should be adaptive, i.e. should be able to learn from experience and adapt continuously to changes in the environment. This paper presents a discriminative incremental learning approach to place recognition. We use a recently introduced version of the incremental SVM, which ...

  2. MRI: Modular reasoning about interference in incremental programming

    Oliveira, Bruno C. D. S; Schrijvers, Tom; Cook, William R

    2012-01-01

    Incremental Programming (IP) is a programming style in which new program components are defined as increments of other components. Examples of IP mechanisms include: Object-oriented programming (OOP) inheritance, aspect-oriented programming (AOP) advice and feature-oriented programming (FOP). A characteristic of IP mechanisms is that, while individual components can be independently defined, the composition of components makes those components become tightly coupled, sh...

  3. Incremental short daily home hemodialysis: a case series

    Toth-Manikowski, Stephanie M.; Mullangi, Surekha; Hwang, Seungyoung; Shafi, Tariq

    2017-01-01

    Background Patients starting dialysis often have substantial residual kidney function. Incremental hemodialysis provides a hemodialysis prescription that supplements patients? residual kidney function while maintaining total (residual + dialysis) urea clearance (standard Kt/Vurea) targets. We describe our experience with incremental hemodialysis in patients using NxStage System One for home hemodialysis. Case presentation From 2011 to 2015, we initiated 5 incident hemodialysis patients on an ...

  4. Australian Government Balance Sheet Management

    Wilson Au-Yeung; Jason McDonald; Amanda Sayegh

    2006-01-01

    Since almost eliminating net debt, the Australian Government%u2019s attention has turned to the financing of broader balance sheet liabilities, such as public sector superannuation. Australia will be developing a significant financial asset portfolio in the %u2018Future Fund%u2019 to smooth the financing of expenses through time. This raises the significant policy question of how best to manage the government balance sheet to reduce risk. This paper provides a framework for optimal balance sh...

  5. Energy information sheets, July 1998

    NONE

    1998-07-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  6. Energy information sheets, September 1996

    NONE

    1996-09-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  7. Single sheet iron oxides

    Yin, Zhou

    profile with reversible reduction and oxidation, suggesting the formation of FeII-OH/O-FeIII clusters as that in GRs were formed on the ITO electrode (trichloroethylene (TCE), tetrachloride (CT) and 4-chlorophenol are used to test...

  8. Pharmacogenomics Fact Sheet

    ... all prescription drugs. For example, it converts the painkiller codeine into its active form, morphine. There are ... patients by providing guidance on dose, possible side effects, or differences in effectiveness for people with certain ...

  9. Atmospheric response to Saharan dust deduced from ECMWF reanalysis increments

    Kishcha, P.; Alpert, P.; Barkan, J.; Kirchner, I.; Machenhauer, B.

    2003-04-01

    This study focuses on the atmospheric temperature response to dust deduced from a new source of data - the European Reanalysis (ERA) increments. These increments are the systematic errors of global climate models, generated in reanalysis procedure. The model errors result not only from the lack of desert dust but also from a complex combination of many kinds of model errors. Over the Sahara desert the dust radiative effect is believed to be a predominant model defect which should significantly affect the increments. This dust effect was examined by considering correlation between the increments and remotely-sensed dust. Comparisons were made between April temporal variations of the ERA analysis increments and the variations of the Total Ozone Mapping Spectrometer aerosol index (AI) between 1979 and 1993. The distinctive structure was identified in the distribution of correlation composed of three nested areas with high positive correlation (> 0.5), low correlation, and high negative correlation (Forecast(ECMWF) suggests that the PCA (NCA) corresponds mainly to anticyclonic (cyclonic) flow, negative (positive) vorticity, and downward (upward) airflow. These facts indicate an interaction between dust-forced heating /cooling and atmospheric circulation. The April correlation results are supported by the analysis of vertical distribution of dust concentration, derived from the 24-hour dust prediction system at Tel Aviv University (website: http://earth.nasa.proj.ac.il/dust/current/). For other months the analysis is more complicated because of the essential increasing of humidity along with the northward progress of the ITCZ and the significant impact on the increments.

  10. Entity versus incremental theories predict older adults' memory performance.

    Plaks, Jason E; Chasteen, Alison L

    2013-12-01

    The authors examined whether older adults' implicit theories regarding the modifiability of memory in particular (Studies 1 and 3) and abilities in general (Study 2) would predict memory performance. In Study 1, individual differences in older adults' endorsement of the "entity theory" (a belief that one's ability is fixed) or "incremental theory" (a belief that one's ability is malleable) of memory were measured using a version of the Implicit Theories Measure (Dweck, 1999). Memory performance was assessed with a free-recall task. Results indicated that the higher the endorsement of the incremental theory, the better the free recall. In Study 2, older and younger adults' theories were measured using a more general version of the Implicit Theories Measure that focused on the modifiability of abilities in general. Again, for older adults, the higher the incremental endorsement, the better the free recall. Moreover, as predicted, implicit theories did not predict younger adults' memory performance. In Study 3, participants read mock news articles reporting evidence in favor of either the entity or incremental theory. Those in the incremental condition outperformed those in the entity condition on reading span and free-recall tasks. These effects were mediated by pretask worry such that, for those in the entity condition, higher worry was associated with lower performance. Taken together, these studies suggest that variation in entity versus incremental endorsement represents a key predictor of older adults' memory performance. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  11. Incremental short daily home hemodialysis: a case series.

    Toth-Manikowski, Stephanie M; Mullangi, Surekha; Hwang, Seungyoung; Shafi, Tariq

    2017-07-05

    Patients starting dialysis often have substantial residual kidney function. Incremental hemodialysis provides a hemodialysis prescription that supplements patients' residual kidney function while maintaining total (residual + dialysis) urea clearance (standard Kt/Vurea) targets. We describe our experience with incremental hemodialysis in patients using NxStage System One for home hemodialysis. From 2011 to 2015, we initiated 5 incident hemodialysis patients on an incremental home hemodialysis regimen. The biochemical parameters of all patients remained stable on the incremental hemodialysis regimen and they consistently achieved standard Kt/Vurea targets. Of the two patients with follow-up >6 months, residual kidney function was preserved for ≥2 years. Importantly, the patients were able to transition to home hemodialysis without automatically requiring 5 sessions per week at the outset and gradually increased the number of treatments and/or dialysate volume as the residual kidney function declined. An incremental home hemodialysis regimen can be safely prescribed and may improve acceptability of home hemodialysis. Reducing hemodialysis frequency by even one treatment per week can reduce the number of fistula or graft cannulations or catheter connections by >100 per year, an important consideration for patient well-being, access longevity, and access-related infections. The incremental hemodialysis approach, supported by national guidelines, can be considered for all home hemodialysis patients with residual kidney function.

  12. FDTD modeling of thin impedance sheets

    Luebbers, Raymond J.; Kunz, Karl S.

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

  13. Formability of porous tantalum sheet-metal

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

    2009-01-01

    Over the past ten years, a novel cellular solid, Trabecular Metal T M , 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 T M 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.

  14. Dynamics of a radially expanding liquid sheet: Experiments

    Majumdar, Nayanika; Tirumkudulu, Mahesh

    2017-11-01

    A recent theory predicts that sinuous waves generated at the center of a radially expanding liquid sheet grow spatially even in absence of a surrounding gas phase. Unlike flat liquid sheets, the thickness of a radially expanding liquid sheet varies inversely with distance from the center of the sheet. To test the predictions of the theory, experiments were carried out on a horizontal, radially expanding liquid sheet formed by collision of a single jet on a solid impactor. The latter was placed on a speaker-vibrator with controlled amplitude and frequency. The growth of sinuous waves was determined by measuring the wave surface inclination angle using reflected laser light under both atmospheric and sub-atmospheric pressure conditions. It is shown that the measured growth rate matches with the predictions of the theory over a large range of Weber numbers for both pressure conditions suggesting that the thinning of the liquid sheet plays a dominant role in setting the growth rate of sinuous waves with minimal influence of the surrounding gas phase on its dynamics. IIT Bombay.

  15. Ice_Sheets_CCI: Essential Climate Variables for the Greenland Ice Sheet

    Forsberg, R.; Sørensen, L. S.; Khan, A.; Aas, C.; Evansberget, D.; Adalsteinsdottir, G.; Mottram, R.; Andersen, S. B.; Ahlstrøm, A.; Dall, J.; Kusk, A.; Merryman, J.; Hvidberg, C.; Khvorostovsky, K.; Nagler, T.; Rott, H.; Scharrer, M.; Shepard, A.; Ticconi, F.; Engdahl, M.

    2012-04-01

    As part of the ESA Climate Change Initiative (www.esa-cci.org) a long-term project "ice_sheets_cci" started January 1, 2012, in addition to the existing 11 projects already generating Essential Climate Variables (ECV) for the Global Climate Observing System (GCOS). The "ice_sheets_cci" goal is to generate a consistent, long-term and timely set of key climate parameters for the Greenland ice sheet, to maximize the impact of European satellite data on climate research, from missions such as ERS, Envisat and the future Sentinel satellites. The climate parameters to be provided, at first in a research context, and in the longer perspective by a routine production system, would be grids of Greenland ice sheet elevation changes from radar altimetry, ice velocity from repeat-pass SAR data, as well as time series of marine-terminating glacier calving front locations and grounding lines for floating-front glaciers. The ice_sheets_cci project will involve a broad interaction of the relevant cryosphere and climate communities, first through user consultations and specifications, and later in 2012 optional participation in "best" algorithm selection activities, where prototype climate parameter variables for selected regions and time frames will be produced and validated using an objective set of criteria ("Round-Robin intercomparison"). This comparative algorithm selection activity will be completely open, and we invite all interested scientific groups with relevant experience to participate. The results of the "Round Robin" exercise will form the algorithmic basis for the future ECV production system. First prototype results will be generated and validated by early 2014. The poster will show the planned outline of the project and some early prototype results.

  16. On Jovian plasma sheet structure

    Khurana, K.K.; Kivelson, M.G.

    1989-01-01

    The authors evaluate several models of Jovian plasma sheet structure by determining how well they organize several aspects of the observed Voyager 2 magnetic field characteristics as a function of Jovicentric radial distance. It is shown that in the local time sector of the Voyager 2 outbound pass (near 0300 LT) the published hinged-magnetodisc models with wave (i.e., models corrected for finite wave velocity effects) are more successful than the published magnetic anomaly model in predicting locations of current sheet crossings. They also consider the boundary between the plasma sheet and the magnetotail lobe which is expected to vary slowly with radial distance. They use this boundary location as a further test of the models of the magnetotail. They show that the compressional MHD waves have much smaller amplitude in the lobes than in the plasma sheet and use this criterion to refine the identification of the plasma-sheet-lobe boundary. When the locations of crossings into and out of the lobes are examined, it becomes evident that the magnetic-anomaly model yields a flaring plasma sheet with a halfwidth of ∼ 3 R J at a radial distance of 20 R J and ∼ 12 R J at a radial distance of 100 R J . The hinged-magnetodisc models with wave, on the other hand, predict a halfwidth of ∼ 3.5 R J independent of distance beyond 20 R J . New optimized versions of the two models locate both the current sheet crossings and lobe encounters equally successfully. The optimized hinged-magnetodisc model suggests that the wave velocity decreases with increasing radial distance. The optimized magnetic anomaly model yields lower velocity contrast than the model of Vasyliunas and Dessler (1981)

  17. Selection and Interview Forms for Nomination Area Committees. Appendix A.

    Georgia State Dept. of Education, Atlanta. Office of Instructional Services.

    The selection and interview forms for use in selecting students for the Georgia Governor's Honors Program are provided. These forms are: Science Interview Summary Sheet; Interview Form for Candidates in Music; State College Musicality Test; Mathematics Interview Sheet; Criteria for Selection of Students for Mathematics, 1972; Visual Arts…

  18. Lines of Evidence–Incremental Markings in Molar Enamel of Soay Sheep as Revealed by a Fluorochrome Labeling and Backscattered Electron Imaging Study

    Kierdorf, Horst; Kierdorf, Uwe; Frölich, Kai; Witzel, Carsten

    2013-01-01

    We studied the structural characteristics and periodicities of regular incremental markings in sheep enamel using fluorochrome injections for vital labeling of forming enamel and backscattered electron imaging in the scanning electron microscope. Microscopic analysis of mandibular first molars revealed the presence of incremental markings with a daily periodicity (laminations) that indicated successive positions of the forming front of interprismatic enamel. In addition to the laminations, incremental markings with a sub-daily periodicity were discernible both in interprismatic enamel and in enamel prisms. Five sub-daily increments were present between two consecutive laminations. Backscattered electron imaging revealed that each sub-daily growth increment consisted of a broader and more highly mineralized band and a narrower and less mineralized band (line). The sub-daily markings in the prisms of sheep enamel morphologically resembled the (daily) prisms cross striations seen in primate enamel. Incremental markings with a supra-daily periodicity were not observed in sheep enamel. Based on the periodicity of the incremental markings, maximum mean daily apposition rates of 17.0 µm in buccal enamel and of 13.4 µm in lingual enamel were recorded. Enamel extension rates were also high, with maximum means of 180 µm/day and 217 µm/day in upper crown areas of buccal and lingual enamel, respectively. Values in more cervical crown portions were markedly lower. Our results are in accordance with previous findings in other ungulate species. Using the incremental markings present in primate enamel as a reference could result in a misinterpretation of the incremental markings in ungulate enamel. Thus, the sub-daily growth increments in the prisms of ungulate enamel might be mistaken as prism cross striations with a daily periodicity, and the laminations misidentified as striae of Retzius with a supra-daily periodicity. This would lead to a considerable overestimation of

  19. Uranium mining sites - Thematic sheets

    2009-01-01

    A first sheet proposes comments, data and key numbers about uranium extraction in France: general overview of uranium mining sites, status of waste rock and tailings after exploitation, site rehabilitation. The second sheet addresses the sources of exposure to ionizing radiations due to ancient uranium mining sites: discussion on the identification of these sources associated with these sites, properly due to mining activities or to tailings, or due to the transfer of radioactive substances towards water and to the contamination of sediments, description of the practice and assessment of radiological control of mining sites. A third sheet addresses the radiological exposure of public to waste rocks, and the dose assessment according to exposure scenarios: main exposure ways to be considered, studied exposure scenarios (passage on backfilled path and grounds, stay in buildings built on waste rocks, keeping mineralogical samples at home). The fourth sheet addresses research programmes of the IRSN on uranium and radon: epidemiological studies (performed on mine workers; on French and on European cohorts, French and European studies on the risk of lung cancer associated with radon in housing), study of the biological effects of chronic exposures. The last sheet addresses studies and expertises performed by the IRSN on ancient uranium mining sites in France: studies commissioned by public authorities, radioactivity control studies performed by the IRSN about mining sites, participation of the IRSN to actions to promote openness to civil society

  20. Modeling the Alzheimer Abeta17-42 fibril architecture: tight intermolecular sheet-sheet association and intramolecular hydrated cavities.

    Zheng, Jie; Jang, Hyunbum; Ma, Buyong; Tsai, Chung-Jun; Nussinov, Ruth

    2007-11-01

    We investigate Abeta(17-42) protofibril structures in solution using molecular dynamics simulations. Recently, NMR and computations modeled the Abeta protofibril as a longitudinal stack of U-shaped molecules, creating an in-parallel beta-sheet and loop spine. Here we study the molecular architecture of the fibril formed by spine-spine association. We model in-register intermolecular beta-sheet-beta-sheet associations and study the consequences of Alzheimer's mutations (E22G, E22Q, E22K, and M35A) on the organization. We assess the structural stability and association force of Abeta oligomers with different sheet-sheet interfaces. Double-layered oligomers associating through the C-terminal-C-terminal interface are energetically more favorable than those with the N-terminal-N-terminal interface, although both interfaces exhibit high structural stability. The C-terminal-C-terminal interface is essentially stabilized by hydrophobic and van der Waals (shape complementarity via M35-M35 contacts) intermolecular interactions, whereas the N-terminal-N-terminal interface is stabilized by hydrophobic and electrostatic interactions. Hence, shape complementarity, or the "steric zipper" motif plays an important role in amyloid formation. On the other hand, the intramolecular Abeta beta-strand-loop-beta-strand U-shaped motif creates a hydrophobic cavity with a diameter of 6-7 A, allowing water molecules and ions to conduct through. The hydrated hydrophobic cavities may allow optimization of the sheet association and constitute a typical feature of fibrils, in addition to the tight sheet-sheet association. Thus, we propose that Abeta fiber architecture consists of alternating layers of tight packing and hydrated cavities running along the fibrillar axis, which might be possibly detected by high-resolution imaging.

  1. Support vector machine incremental learning triggered by wrongly predicted samples

    Tang, Ting-long; Guan, Qiu; Wu, Yi-rong

    2018-05-01

    According to the classic Karush-Kuhn-Tucker (KKT) theorem, at every step of incremental support vector machine (SVM) learning, the newly adding sample which violates the KKT conditions will be a new support vector (SV) and migrate the old samples between SV set and non-support vector (NSV) set, and at the same time the learning model should be updated based on the SVs. However, it is not exactly clear at this moment that which of the old samples would change between SVs and NSVs. Additionally, the learning model will be unnecessarily updated, which will not greatly increase its accuracy but decrease the training speed. Therefore, how to choose the new SVs from old sets during the incremental stages and when to process incremental steps will greatly influence the accuracy and efficiency of incremental SVM learning. In this work, a new algorithm is proposed to select candidate SVs and use the wrongly predicted sample to trigger the incremental processing simultaneously. Experimental results show that the proposed algorithm can achieve good performance with high efficiency, high speed and good accuracy.

  2. Three routes forward for biofuels: Incremental, leapfrog, and transitional

    Morrison, Geoff M.; Witcover, Julie; Parker, Nathan C.; Fulton, Lew

    2016-01-01

    This paper examines three technology routes for lowering the carbon intensity of biofuels: (1) a leapfrog route that focuses on major technological breakthroughs in lignocellulosic pathways at new, stand-alone biorefineries; (2) an incremental route in which improvements are made to existing U.S. corn ethanol and soybean biodiesel biorefineries; and (3) a transitional route in which biotechnology firms gain experience growing, handling, or chemically converting lignocellulosic biomass in a lower-risk fashion than leapfrog biorefineries by leveraging existing capital stock. We find the incremental route is likely to involve the largest production volumes and greenhouse gas benefits until at least the mid-2020s, but transitional and leapfrog biofuels together have far greater long-term potential. We estimate that the Renewable Fuel Standard, California's Low Carbon Fuel Standard, and federal tax credits provided an incentive of roughly $1.5–2.5 per gallon of leapfrog biofuel between 2012 and 2015, but that regulatory elements in these policies mostly incentivize lower-risk incremental investments. Adjustments in policy may be necessary to bring a greater focus on transitional technologies that provide targeted learning and cost reduction opportunities for leapfrog biofuels. - Highlights: • Three technological pathways are compared that lower carbon intensity of biofuels. • Incremental changes lead to faster greenhouse gas reductions. • Leapfrog changes lead to greatest long-term potential. • Two main biofuel policies (RFS and LCFS) are largely incremental in nature. • Transitional biofuels offer medium-risk, medium reward pathway.

  3. Spread-sheet application to classify radioactive material for shipment

    Brown, A.N.

    1998-01-01

    A spread-sheet application has been developed at the Idaho National Engineering and Environmental Laboratory to aid the shipper when classifying nuclide mixtures of normal form, radioactive materials. The results generated by this spread-sheet are used to confirm the proper US DOT classification when offering radioactive material packages for transport. The user must input to the spread-sheet the mass of the material being classified, the physical form (liquid or not) and the activity of each regulated nuclide. The spread-sheet uses these inputs to calculate two general values: 1)the specific activity of the material and a summation calculation of the nuclide content. The specific activity is used to determine if the material exceeds the DOT minimal threshold for a radioactive material. If the material is calculated to be radioactive, the specific activity is also used to determine if the material meets the activity requirement for one of the three low specific activity designations (LSA-I, LSA-II, LSA-III, or not LSA). Again, if the material is calculated to be radioactive, the summation calculation is then used to determine which activity category the material will meet (Limited Quantity, Type A, Type B, or Highway Route Controlled Quantity). This spread-sheet has proven to be an invaluable aid for shippers of radioactive materials at the Idaho National Engineering and Environmental Laboratory. (authors)

  4. γ-ray irradiation effect on magnetic properties of electromagnetic Fe-Si sheets

    Harara, W.

    1994-11-01

    The present work investigates the effect of γ-ray irradiation on the relative and differential magnetic permeabilities of electromagnetic steel sheets. The experimental work was carried out using transformer Fe-Si (97-3%) sheets. The sheets have two different forms E and I> The magnetic field dependence on the relative permeability as well as on the differential permeability before and after irradiation were measured. The measurements show that the relative permeability values of the sheets after irradiation in the region of rotation of magnetization domains were decreased whereas the value of their differential permeability around each working point remains unchangeable. (author). 7 refs., 14 figs., 6 tabs

  5. On the energy release rate in a turbulent current sheet on the Sun

    Bardakov, V.M.

    1986-01-01

    It is shown that turbulent current sheets on the Sun, realizing in the form of the Parker - Sweet flow, are in quasilinear regime of turbulence (or in the regime of instability threshold). The energy release rate in such sheets does not exceed 10 26 erg/s for typical plasma parameters in active regions

  6. Infill of tunnel valleys associated with landward‐flowing ice sheets

    Moreau, Julien; Huuse, Mads

    2014-01-01

    The southern termination of the Middle and Late Pleistocene Scandinavian ice sheets was repeatedly located in the southern North Sea (sNS) and adjacent, north-sloping land areas. Giant meltwater-excavated valleys (tunnel valleys) formed at the southern termination of the ice sheets and contain...

  7. Root-growth-inhibiting sheet

    Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.; Van Voris, P.

    1993-01-26

    In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a geotextile'' and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

  8. Root-growth-inhibiting sheet

    Burton, Frederick G.; Cataldo, Dominic A.; Cline, John F.; Skiens, W. Eugene; Van Voris, Peter

    1993-01-01

    In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

  9. Making context explicit for explanation and incremental knowledge acquisition

    Brezillon, P. [Univ. Paris (France)

    1996-12-31

    Intelligent systems may be improved by making context explicit in problem solving. This is a lesson drawn from a study of the reasons why a number of knowledge-based systems (KBSs) failed. We discuss the interest to make context explicit in explanation generation and incremental knowledge acquisition, two important aspects of intelligent systems that aim to cooperate with users. We show how context can be used to better explain and incrementally acquire knowledge. The advantages of using context in explanation and incremental knowledge acquisition are discussed through SEPIT, an expert system for supporting diagnosis and explanation through simulation of power plants. We point out how the limitations of such systems may be overcome by making context explicit.

  10. Martingales, nonstationary increments, and the efficient market hypothesis

    McCauley, Joseph L.; Bassler, Kevin E.; Gunaratne, Gemunu H.

    2008-06-01

    We discuss the deep connection between nonstationary increments, martingales, and the efficient market hypothesis for stochastic processes x(t) with arbitrary diffusion coefficients D(x,t). We explain why a test for a martingale is generally a test for uncorrelated increments. We explain why martingales look Markovian at the level of both simple averages and 2-point correlations. But while a Markovian market has no memory to exploit and cannot be beaten systematically, a martingale admits memory that might be exploitable in higher order correlations. We also use the analysis of this paper to correct a misstatement of the ‘fair game’ condition in terms of serial correlations in Fama’s paper on the EMH. We emphasize that the use of the log increment as a variable in data analysis generates spurious fat tails and spurious Hurst exponents.

  11. ACCOUNTING POLICIES EFFECTS ON DEPRECIATION AND EVALUATION OF BALANCE SHEET

    Andreea Elena DREGHICIU

    2016-12-01

    Starting from the diversity of principles and rules that exist within the accounting, this paper aims to form a main problematic frame concerning the principle of the method’s constancy, whose purpose is applying the same registration, evaluation and presentation methods for operations, transactions, and balance sheet elements.

  12. Sucrose Treated Carbon Nanotube and Graphene Yarns and Sheets

    Sauti, Godfrey (Inventor); Kim, Jae-Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor)

    2017-01-01

    Consolidated carbon nanotube or graphene yarns and woven sheets are consolidated through the formation of a carbon binder formed from the dehydration of sucrose. The resulting materials, on a macro-scale are lightweight and of a high specific modulus and/or strength. Sucrose is relatively inexpensive and readily available, and the process is therefore cost-effective.

  13. Large patternable metal nanoparticle sheets by photo/e-beam lithography

    Saito, Noboru; Wang, Pangpang; Okamoto, Koichi; Ryuzaki, Sou; Tamada, Kaoru

    2017-10-01

    Techniques for micro/nano-scale patterning of large metal nanoparticle sheets can potentially be used to realize high-performance photoelectronic devices because the sheets provide greatly enhanced electrical fields around the nanoparticles due to localized surface plasmon resonances. However, no single metal nanoparticle sheet currently exists with sufficient durability for conventional lithographical processes. Here, we report large photo and/or e-beam lithographic patternable metal nanoparticle sheets with improved durability by incorporating molecular cross-linked structures between nanoparticles. The cross-linked structures were easily formed by a one-step chemical reaction; immersing a single nanoparticle sheet consisting of core metals, to which capping molecules ionically bond, in a dithiol ethanol solution. The ligand exchange reaction processes were discussed in detail, and we demonstrated 20 μm wide line and space patterns, and a 170 nm wide line of the silver nanoparticle sheets.

  14. Ice sheet hydrology - a review

    Jansson, Peter; Naeslund, Jens-Ove [Dept. of Physical Geography and Quaternary Geology, Stockholm Univ., Stockholm (Sweden); Rodhe, Lars [Geological Survey of Sweden, Uppsala (Sweden)

    2007-03-15

    This report summarizes the theoretical knowledge on water flow in and beneath glaciers and ice sheets and how these theories are applied in models to simulate the hydrology of ice sheets. The purpose is to present the state of knowledge and, perhaps more importantly, identify the gaps in our understanding of ice sheet hydrology. Many general concepts in hydrology and hydraulics are applicable to water flow in glaciers. However, the unique situation of having the liquid phase flowing in conduits of the solid phase of the same material, water, is not a commonly occurring phenomena. This situation means that the heat exchange between the phases and the resulting phase changes also have to be accounted for in the analysis. The fact that the solidus in the pressure-temperature dependent phase diagram of water has a negative slope provides further complications. Ice can thus melt or freeze from both temperature and pressure variations or variations in both. In order to provide details of the current understanding of water flow in conjunction with deforming ice and to provide understanding for the development of ideas and models, emphasis has been put on the mathematical treatments, which are reproduced in detail. Qualitative results corroborating theory or, perhaps more often, questioning the simplifications made in theory, are also given. The overarching problem with our knowledge of glacier hydrology is the gap between the local theories of processes and the general flow of water in glaciers and ice sheets. Water is often channelized in non-stationary conduits through the ice, features which due to their minute size relative to the size of glaciers and ice sheets are difficult to incorporate in spatially larger models. Since the dynamic response of ice sheets to global warming is becoming a key issue in, e.g. sea-level change studies, the problems of the coupling between the hydrology of an ice sheet and its dynamics is steadily gaining interest. New work is emerging

  15. Ice sheet hydrology - a review

    Jansson, Peter; Naeslund, Jens-Ove; Rodhe, Lars

    2007-03-01

    This report summarizes the theoretical knowledge on water flow in and beneath glaciers and ice sheets and how these theories are applied in models to simulate the hydrology of ice sheets. The purpose is to present the state of knowledge and, perhaps more importantly, identify the gaps in our understanding of ice sheet hydrology. Many general concepts in hydrology and hydraulics are applicable to water flow in glaciers. However, the unique situation of having the liquid phase flowing in conduits of the solid phase of the same material, water, is not a commonly occurring phenomena. This situation means that the heat exchange between the phases and the resulting phase changes also have to be accounted for in the analysis. The fact that the solidus in the pressure-temperature dependent phase diagram of water has a negative slope provides further complications. Ice can thus melt or freeze from both temperature and pressure variations or variations in both. In order to provide details of the current understanding of water flow in conjunction with deforming ice and to provide understanding for the development of ideas and models, emphasis has been put on the mathematical treatments, which are reproduced in detail. Qualitative results corroborating theory or, perhaps more often, questioning the simplifications made in theory, are also given. The overarching problem with our knowledge of glacier hydrology is the gap between the local theories of processes and the general flow of water in glaciers and ice sheets. Water is often channelized in non-stationary conduits through the ice, features which due to their minute size relative to the size of glaciers and ice sheets are difficult to incorporate in spatially larger models. Since the dynamic response of ice sheets to global warming is becoming a key issue in, e.g. sea-level change studies, the problems of the coupling between the hydrology of an ice sheet and its dynamics is steadily gaining interest. New work is emerging

  16. Sheet Beam Klystron Instability Analysis

    Bane, K.

    2009-01-01

    Using the principle of energy balance we develop a 2D theory for calculating growth rates of instability in a two-cavity model of a sheet beam klystron. An important ingredient is a TE-like mode in the gap that also gives a longitudinal kick to the beam. When compared with a self-consistent particle-in-cell calculation, with sheet beam klystron-type parameters, agreement is quite good up to half the design current, 65 A; at full current, however, other, current-dependent effects come in and the results deviate significantly

  17. The social balance sheet 2004

    Ph. Delhez; P. Heuse

    2005-01-01

    Each year, in the 4th quarter’s Economic Review, the National Bank examines the provisional results of the social balance sheets. As all the social balance sheets are not yet available for 2004, the study is based on a limited population of enterprises, compiled according to the principle of a constant sample. This population is made up of 38,530 enterprises employing around 1,331,000 workers in 2004. The main results of the analysis, in terms of employment, working hours, labour cost and tra...

  18. Motion-Induced Blindness Using Increments and Decrements of Luminance

    Stine Wm Wren

    2017-10-01

    Full Text Available Motion-induced blindness describes the disappearance of stationary elements of a scene when other, perhaps non-overlapping, elements of the scene are in motion. We measured the effects of increment (200.0 cd/m2 and decrement targets (15.0 cd/m2 and masks presented on a grey background (108.0 cd/m2, tapping into putative ON- and OFF-channels, on the rate of target disappearance psychophysically. We presented two-frame motion, which has coherent motion energy, and dynamic Glass patterns and dynamic anti-Glass patterns, which do not have coherent motion energy. Using the method of constant stimuli, participants viewed stimuli of varying durations (3.1 s, 4.6 s, 7.0 s, 11 s, or 16 s in a given trial and then indicated whether or not the targets vanished during that trial. Psychometric function midpoints were used to define absolute threshold mask duration for the disappearance of the target. 95% confidence intervals for threshold disappearance times were estimated using a bootstrap technique for each of the participants across two experiments. Decrement masks were more effective than increment masks with increment targets. Increment targets were easier to mask than decrement targets. Distinct mask pattern types had no effect, suggesting that perceived coherence contributes to the effectiveness of the mask. The ON/OFF dichotomy clearly carries its influence to the level of perceived motion coherence. Further, the asymmetry in the effects of increment and decrement masks on increment and decrement targets might lead one to speculate that they reflect the ‘importance’ of detecting decrements in the environment.

  19. The Dark Side of Malleability: Incremental Theory Promotes Immoral Behaviors.

    Huang, Niwen; Zuo, Shijiang; Wang, Fang; Cai, Pan; Wang, Fengxiang

    2017-01-01

    Implicit theories drastically affect an individual's processing of social information, decision making, and action. The present research focuses on whether individuals who hold the implicit belief that people's moral character is fixed (entity theorists) and individuals who hold the implicit belief that people's moral character is malleable (incremental theorists) make different choices when facing a moral decision. Incremental theorists are less likely to make the fundamental attribution error (FAE), rarely make moral judgment based on traits and show more tolerance to immorality, relative to entity theorists, which might decrease the possibility of undermining the self-image when they engage in immoral behaviors, and thus we posit that incremental beliefs facilitate immorality. Four studies were conducted to explore the effect of these two types of implicit theories on immoral intention or practice. The association between implicit theories and immoral behavior was preliminarily examined from the observer perspective in Study 1, and the results showed that people tended to associate immoral behaviors (including everyday immoral intention and environmental destruction) with an incremental theorist rather than an entity theorist. Then, the relationship was further replicated from the actor perspective in Studies 2-4. In Study 2, implicit theories, which were measured, positively predicted the degree of discrimination against carriers of the hepatitis B virus. In Study 3, implicit theories were primed through reading articles, and the participants in the incremental condition showed more cheating than those in the entity condition. In Study 4, implicit theories were primed through a new manipulation, and the participants in the unstable condition (primed incremental theory) showed more discrimination than those in the other three conditions. Taken together, the results of our four studies were consistent with our hypotheses.

  20. The Dark Side of Malleability: Incremental Theory Promotes Immoral Behaviors

    Niwen Huang

    2017-08-01

    Full Text Available Implicit theories drastically affect an individual’s processing of social information, decision making, and action. The present research focuses on whether individuals who hold the implicit belief that people’s moral character is fixed (entity theorists and individuals who hold the implicit belief that people’s moral character is malleable (incremental theorists make different choices when facing a moral decision. Incremental theorists are less likely to make the fundamental attribution error (FAE, rarely make moral judgment based on traits and show more tolerance to immorality, relative to entity theorists, which might decrease the possibility of undermining the self-image when they engage in immoral behaviors, and thus we posit that incremental beliefs facilitate immorality. Four studies were conducted to explore the effect of these two types of implicit theories on immoral intention or practice. The association between implicit theories and immoral behavior was preliminarily examined from the observer perspective in Study 1, and the results showed that people tended to associate immoral behaviors (including everyday immoral intention and environmental destruction with an incremental theorist rather than an entity theorist. Then, the relationship was further replicated from the actor perspective in Studies 2–4. In Study 2, implicit theories, which were measured, positively predicted the degree of discrimination against carriers of the hepatitis B virus. In Study 3, implicit theories were primed through reading articles, and the participants in the incremental condition showed more cheating than those in the entity condition. In Study 4, implicit theories were primed through a new manipulation, and the participants in the unstable condition (primed incremental theory showed more discrimination than those in the other three conditions. Taken together, the results of our four studies were consistent with our hypotheses.

  1. Annual Energy Balance Sheets 2001-2002

    2004-01-01

    During the year 2002 the primary supply of energy reached 629 TWh, which is 7.7 TWh less than 2001. The decrease originates mainly from the reduced electricity production from water power. Also the electricity production in nuclear power plants decreased by 4.5 TWh. If we were to look at the supplied energy for final consumption we will find a slightly rise by 1.8 TWh. The year 2002 was warmer than a 'normal' year and that consequently brings lower energy needs. Compared with 2001, 2002 was not warmer and a net electricity import of 5.4 TWh covered the energy needs. The energy use increased by 3.3 TWh between 2002 and 2001. The industry sector shows the largest rise by 2.9 TWh, nearly 2 per cent. Within that sector, energy from biomass fuel had a rise by 6.7 per cent. The household sector decreases its energy use by 2.7 per cent, and oil and electricity show the largest decrease. The proportionately high electricity price probably had a slowing down effect on the electricity use. The balance sheets of energy sources are showing the total supply and consumption of energy sources expressed in original units, i.e. units recorded in the primary statistics - mainly commercial units. The production of derived energy commodities is recorded on the supply - side of the balance sheets of energy sources, which is not the case in the energy balance sheets. The balance sheets of energy sources also include specifications of input--output and energy consumption in energy conversion industries. The energy balance sheets are based on primary data recorded in the balance sheets of energy sources, here expressed in a common energy unit, TJ. The production of derived energy is recorded in a second flow-step comprising energy turnover in energy conversion and is also specified in complementary input - output tables for energy conversion industries. The following items are shown in the energy balance sheets. 1.1 Inland supply of primary energy; 1.3 Import; 1.4 Export; 1.5 Changes in

  2. Average-case analysis of incremental topological ordering

    Ajwani, Deepak; Friedrich, Tobias

    2010-01-01

    Many applications like pointer analysis and incremental compilation require maintaining a topological ordering of the nodes of a directed acyclic graph (DAG) under dynamic updates. All known algorithms for this problem are either only analyzed for worst-case insertion sequences or only evaluated...... experimentally on random DAGs. We present the first average-case analysis of incremental topological ordering algorithms. We prove an expected runtime of under insertion of the edges of a complete DAG in a random order for the algorithms of Alpern et al. (1990) [4], Katriel and Bodlaender (2006) [18], and Pearce...

  3. Short-term load forecasting with increment regression tree

    Yang, Jingfei; Stenzel, Juergen [Darmstadt University of Techonology, Darmstadt 64283 (Germany)

    2006-06-15

    This paper presents a new regression tree method for short-term load forecasting. Both increment and non-increment tree are built according to the historical data to provide the data space partition and input variable selection. Support vector machine is employed to the samples of regression tree nodes for further fine regression. Results of different tree nodes are integrated through weighted average method to obtain the comprehensive forecasting result. The effectiveness of the proposed method is demonstrated through its application to an actual system. (author)

  4. Deglaciation of the Eurasian ice sheet complex

    Patton, Henry; Hubbard, Alun; Andreassen, Karin; Auriac, Amandine; Whitehouse, Pippa L.; Stroeven, Arjen P.; Shackleton, Calvin; Winsborrow, Monica; Heyman, Jakob; Hall, Adrian M.

    2017-08-01

    The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the EISC honouring these new constraints is conspicuously lacking. Here, we apply a first-order, thermomechanical ice sheet model, validated against a diverse suite of empirical data, to investigate the retreat of the EISC after 23 ka BP, directly extending the work of Patton et al. (2016) who modelled the build-up to its maximum extent. Retreat of the ice sheet complex was highly asynchronous, reflecting contrasting regional sensitivities to climate forcing, oceanic influence, and internal dynamics. Most rapid retreat was experienced across the Barents Sea sector after 17.8 ka BP when this marine-based ice sheet disintegrated at a rate of ∼670 gigatonnes per year (Gt a-1) through enhanced calving and interior dynamic thinning, driven by oceanic/atmospheric warming and exacerbated by eustatic sea-level rise. From 14.9 to 12.9 ka BP the EISC lost on average 750 Gt a-1, peaking at rates >3000 Gt a-1, roughly equally partitioned between surface melt and dynamic losses, and potentially contributing up to 2.5 m to global sea-level rise during Meltwater Pulse 1A. Independent glacio-isostatic modelling constrained by an extensive inventory of relative sea-level change corroborates our ice sheet loading history of the Barents Sea sector. Subglacial conditions were predominately temperate during deglaciation, with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network. Moreover, the maximum EISC and its isostatic footprint had a profound impact on the proglacial hydrological network, forming the Fleuve Manche mega-catchment which had an area of

  5. Floating Carpets and the Delamination of Elastic Sheets

    Wagner, Till J. W.

    2011-07-22

    We investigate the deformation of a thin elastic sheet floating on a liquid surface and subject to a uniaxial compression. We show that at a critical compression the sheet delaminates from the liquid over a finite region forming a delamination "blister." This blistering regime adds to the wrinkling and localized folding regimes that have been studied previously. The transition from wrinkled to blistered states occurs when delamination becomes energetically favorable compared with wrinkling. We determine the initial blister size and the evolution of blister size with continuing compression before verifying our theoretical results with experiments at a macroscopic scale. © 2011 American Physical Society.

  6. Cost of Incremental Expansion of an Existing Family Medicine Residency Program.

    Ashkin, Evan A; Newton, Warren P; Toomey, Brian; Lingley, Ronald; Page, Cristen P

    2017-07-01

    Expanding residency training programs to address shortages in the primary care workforce is challenged by the present graduate medical education (GME) environment. The Medicare funding cap on new GME positions and reductions in the Health Resources and Services Administration (HRSA) Teaching Health Center (THC) GME program require innovative solutions to support primary care residency expansion. Sparse literature exists to assist in predicting the actual cost of incremental expansion of a family medicine residency program without federal or state GME support. In 2011 a collaboration to develop a community health center (CHC) academic medical partnership (CHAMP), was formed and created a THC as a training site for expansion of an existing family medicine residency program. The cost of expansion was a critical factor as no Federal GME funding or HRSA THC GME program support was available. Initial start-up costs were supported by a federal grant and local foundations. Careful financial analysis of the expansion has provided actual costs per resident of the incremental expansion of the residencyRESULTS: The CHAMP created a new THC and expanded the residency from eight to ten residents per year. The cost of expansion was approximately $72,000 per resident per year. The cost of incremental expansion of our residency program in the CHAMP model was more than 50% less than that of the recently reported cost of training in the HRSA THC GME program.

  7. Exploiting Outage and Error Probability of Cooperative Incremental Relaying in Underwater Wireless Sensor Networks

    Hina Nasir

    2016-07-01

    Full Text Available This paper embeds a bi-fold contribution for Underwater Wireless Sensor Networks (UWSNs; performance analysis of incremental relaying in terms of outage and error probability, and based on the analysis proposition of two new cooperative routing protocols. Subject to the first contribution, a three step procedure is carried out; a system model is presented, the number of available relays are determined, and based on cooperative incremental retransmission methodology, closed-form expressions for outage and error probability are derived. Subject to the second contribution, Adaptive Cooperation in Energy (ACE efficient depth based routing and Enhanced-ACE (E-ACE are presented. In the proposed model, feedback mechanism indicates success or failure of data transmission. If direct transmission is successful, there is no need for relaying by cooperative relay nodes. In case of failure, all the available relays retransmit the data one by one till the desired signal quality is achieved at destination. Simulation results show that the ACE and E-ACE significantly improves network performance, i.e., throughput, when compared with other incremental relaying protocols like Cooperative Automatic Repeat reQuest (CARQ. E-ACE and ACE achieve 69% and 63% more throughput respectively as compared to CARQ in hard underwater environment.

  8. Learning from Balance Sheet Visualization

    Tanlamai, Uthai; Soongswang, Oranuj

    2011-01-01

    This exploratory study examines alternative visuals and their effect on the level of learning of balance sheet users. Executive and regular classes of graduate students majoring in information technology in business were asked to evaluate the extent of acceptance and enhanced capability of these alternative visuals toward their learning…

  9. Off-Balance Sheet Financing.

    Adams, Matthew C.

    1998-01-01

    Examines off-balance sheet financing, the facilities use of outsourcing for selected needs, as a means of saving operational costs and using facility assets efficiently. Examples of using outside sources for energy supply and food services, as well as partnering with business for facility expansion are provided. Concluding comments address tax…

  10. Description and classification of uranium oxide hydrate sheet topologies

    Miller, M.L.; Burns, P.C.; Ewing, R.C.; Finch, R.J.

    1996-01-01

    The uranyl oxide hydrates (UOH) are important corrosion products of uraninite and UO 2 in spent nuclear fuel under oxidizing conditions. However, the systematics of the crystal chemistry, thermodynamic parameters, and solubilities of this mineral group are poorly understood. With the exception of the synthetic UO 2 (OH) 2 polymorphs, all UOH crystal structures are based on sheets of edge-sharing 5 and 4-coordinated uranyl dipyramids. This structural similarity suggests that it is possible to develop a model by which to estimate the thermodynamic behavior of UOHs from data on structural endmember phases. Toward this end, a method of quantitatively describing all known UOH sheets has been developed. Only four structural unit chains are required to construct the uranyl oxide hydrate sheets (as well as the structurally similar U 3 O 8 sheets). The H-chain is restricted to α-UO 2 (OH) 2 and is made up of hexagonally coordinated uranyl ions sharing opposing edges. The arrowhead chain composed of pentagonal dipyramids sharing edges and alternating with trigonal vacancies is present in all other UOH sheets. These arrowhead chains are directed and can occur in both an Up-arrow and Down-arrow sense within a single sheet. The P-chain consists of edge-sharing pentagonal dipyramids forming a zigzag chain. The P-chain is flanked on both sides by arrowhead chains of the same sense. The remaining structural unit is a discontinuous chain of rhombic dipyramids. This R-chain is produced when nested adjacent Up-arrow and Down-arrow arrowhead chains are translated by a diagonal shift. This chain occurs in sheets which contain only 4-coordinate uranyl ion and those containing both 4- and 5-coordinate uranyl ions

  11. Collective epithelial cell sheet adhesion and migration on polyelectrolyte multilayers with uniform and gradients of compliance

    Martinez, Jessica S.; Schlenoff, Joseph B.; Keller, Thomas C.S.

    2016-01-01

    Polyelectrolyte multilayers (PEMUs) are tunable thin films that could serve as coatings for biomedical implants. PEMUs built layer by layer with the polyanion poly(acrylic acid) (PAA) modified with a photosensitive 4-(2-hydroxyethoxy) benzophenone (PAABp) group and the polycation poly(allylamine hydrochloride) (PAH) are mechanically tunable by UV irradiation, which forms covalent bonds between the layers and increases PEMU stiffness. PAH-terminated PEMUs (PAH-PEMUs) that were uncrosslinked, UV-crosslinked to a uniform stiffness, or UV-crosslinked with an edge mask or through a neutral density optical gradient filter to form continuous compliance gradients were used to investigate how differences in PEMU stiffness affect the adhesion and migration of epithelial cell sheets from scales of the fish Poecilia sphenops (Black Molly) and Carassius auratus (Comet Goldfish). During the progressive collective cell migration, the edge cells (also known as ‘leader’ cells) in the sheets on softer uncrosslinked PEMUs and less crosslinked regions of the gradient formed more actin filaments and vinculin-containing adherens junctions and focal adhesions than formed in the sheet cells on stiffer PEMUs or glass. During sheet migration, the ratio of edge cell to internal cell (also known as ‘follower’ cells) motilities were greater on the softer PEMUs than on the stiffer PEMUs or glass, causing tension to develop across the sheet and periods of retraction, during which the edge cells lost adhesion to the substrate and regions of the sheet retracted toward the more adherent internal cell region. These retraction events were inhibited by the myosin II inhibitor Blebbistatin, which reduced the motility velocity ratios to those for sheets on the stiffer PEMUs. Blebbistatin also caused disassembly of actin filaments, reorganization of focal adhesions, increased cell spreading at the leading edge, as well as loss of edge cell-cell connections in epithelial cell sheets on all

  12. Collective epithelial cell sheet adhesion and migration on polyelectrolyte multilayers with uniform and gradients of compliance

    Martinez, Jessica S. [Department of Biological Science, Florida State University, Tallahassee, FL 32306 (United States); Schlenoff, Joseph B. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); Keller, Thomas C.S., E-mail: tkeller@bio.fsu.edu [Department of Biological Science, Florida State University, Tallahassee, FL 32306 (United States)

    2016-08-01

    Polyelectrolyte multilayers (PEMUs) are tunable thin films that could serve as coatings for biomedical implants. PEMUs built layer by layer with the polyanion poly(acrylic acid) (PAA) modified with a photosensitive 4-(2-hydroxyethoxy) benzophenone (PAABp) group and the polycation poly(allylamine hydrochloride) (PAH) are mechanically tunable by UV irradiation, which forms covalent bonds between the layers and increases PEMU stiffness. PAH-terminated PEMUs (PAH-PEMUs) that were uncrosslinked, UV-crosslinked to a uniform stiffness, or UV-crosslinked with an edge mask or through a neutral density optical gradient filter to form continuous compliance gradients were used to investigate how differences in PEMU stiffness affect the adhesion and migration of epithelial cell sheets from scales of the fish Poecilia sphenops (Black Molly) and Carassius auratus (Comet Goldfish). During the progressive collective cell migration, the edge cells (also known as ‘leader’ cells) in the sheets on softer uncrosslinked PEMUs and less crosslinked regions of the gradient formed more actin filaments and vinculin-containing adherens junctions and focal adhesions than formed in the sheet cells on stiffer PEMUs or glass. During sheet migration, the ratio of edge cell to internal cell (also known as ‘follower’ cells) motilities were greater on the softer PEMUs than on the stiffer PEMUs or glass, causing tension to develop across the sheet and periods of retraction, during which the edge cells lost adhesion to the substrate and regions of the sheet retracted toward the more adherent internal cell region. These retraction events were inhibited by the myosin II inhibitor Blebbistatin, which reduced the motility velocity ratios to those for sheets on the stiffer PEMUs. Blebbistatin also caused disassembly of actin filaments, reorganization of focal adhesions, increased cell spreading at the leading edge, as well as loss of edge cell-cell connections in epithelial cell sheets on all

  13. Volatilities, Traded Volumes, and Price Increments in Derivative Securities

    Kim, Kyungsik; Lim, Gyuchang; Kim, Soo Yong; Scalas, Enrico

    2007-03-01

    We apply the detrended fluctuation analysis (DFA) to the statistics of the Korean treasury bond (KTB) futures from which the logarithmic increments, volatilities, and traded volumes are estimated over a specific time lag. For our case, the logarithmic increment of futures prices has no long-memory property, while the volatility and the traded volume exhibit the existence of long-memory property. To analyze and calculate whether the volatility clustering is due to the inherent higher-order correlation not detected by applying directly the DFA to logarithmic increments of the KTB futures, it is of importance to shuffle the original tick data of futures prices and to generate the geometric Brownian random walk with the same mean and standard deviation. It is really shown from comparing the three tick data that the higher-order correlation inherent in logarithmic increments makes the volatility clustering. Particularly, the result of the DFA on volatilities and traded volumes may be supported the hypothesis of price changes.

  14. Playing by the rules? Analysing incremental urban developments

    Karnenbeek, van Lilian; Janssen-Jansen, Leonie

    2018-01-01

    Current urban developments are often considered outdated and static, and the argument follows that they should become more adaptive. In this paper, we argue that existing urban development are already adaptive and incremental. Given this flexibility in urban development, understanding changes in the

  15. Size, Stability and Incremental Budgeting Outcomes in Public Universities.

    Schick, Allen G.; Hills, Frederick S.

    1982-01-01

    Examined the influence of relative size in the analysis of total dollar and workforce budgets, and changes in total dollar and workforce budgets when correlational/regression methods are used. Data suggested that size dominates the analysis of total budgets, and is not a factor when discretionary dollar increments are analyzed. (JAC)

  16. The National Institute of Education and Incremental Budgeting.

    Hastings, Anne H.

    1979-01-01

    The National Institute of Education's (NIE) history demonstrates that the relevant criteria for characterizing budgeting as incremental are not the predictability and stability of appropriations but the conditions of complexity, limited information, multiple factors, and imperfect agreement on ends; NIE's appropriations were dominated by political…

  17. Generation of Referring Expressions: Assessing the Incremental Algorithm

    van Deemter, Kees; Gatt, Albert; van der Sluis, Ielka; Power, Richard

    2012-01-01

    A substantial amount of recent work in natural language generation has focused on the generation of "one-shot" referring expressions whose only aim is to identify a target referent. Dale and Reiter's Incremental Algorithm (IA) is often thought to be the best algorithm for maximizing the similarity to referring expressions produced by people. We…

  18. Object class hierarchy for an incremental hypertext editor

    A. Colesnicov

    1995-02-01

    Full Text Available The object class hierarchy design is considered due to a hypertext editor implementation. The following basic classes were selected: the editor's coordinate system, the memory manager, the text buffer executing basic editing operations, the inherited hypertext buffer, the edit window, the multi-window shell. Special hypertext editing features, the incremental hypertext creation support and further generalizations are discussed.

  19. Bipower variation for Gaussian processes with stationary increments

    Barndorff-Nielsen, Ole Eiler; Corcuera, José Manuel; Podolskij, Mark

    2009-01-01

    Convergence in probability and central limit laws of bipower variation for Gaussian processes with stationary increments and for integrals with respect to such processes are derived. The main tools of the proofs are some recent powerful techniques of Wiener/Itô/Malliavin calculus for establishing...

  20. Identifying the Academic Rising Stars via Pairwise Citation Increment Ranking

    Zhang, Chuxu; Liu, Chuang; Yu, Lu; Zhang, Zi-Ke; Zhou, Tao

    2017-01-01

    success academic careers. In this work, given a set of young researchers who have published the first first-author paper recently, we solve the problem of how to effectively predict the top k% researchers who achieve the highest citation increment in Δt