Showing papers on "Material flow published in 2008"
25 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an attempt has been made to understand the mechanism of friction stir weld formation and the role of the friction stir welding tool in it by understanding the material flow pattern in the weld produced in a special experiment.
Abstract: In this investigation an attempt has been made to understand the mechanism of friction stir weld formation and the role of friction stir welding tool in it. This has been done by understanding the material flow pattern in the weld produced in a special experiment, where the interaction of the friction stir welding tool with the base material is continuously increased. The results show that there are two different modes of material flow regimes involved in the friction stir weld formation; namely “pin-driven flow” and “shoulder-driven flow”. These material flow regimes merge together to form a defect-free weld. The etching contrast in these regimes gives rise to onion ring pattern in friction stir welds. In addition to that based on the material flow characteristics a mechanism of weld formation is proposed.
418 citations
TL;DR: This study analyzes an inventory system with traditional forward-oriented material flow as well as a reverse material flow supply chain and develops a closed-loop supply chain inventory model to maximize the joint profits.
165 citations
TL;DR: In this paper, the authors investigated the size effects on the material flow curve of thin sheet metals under hydraulic bulge testing conditions, where the ratio of the sheet thickness to the material grain size (N=t0/d) was used as a parameter to characterize the interactive effects between the specimen and the grain sizes at the micro-scales.
Abstract: Reliable material models are necessary for accurate analysis of micro-forming and micro-manufacturing processes. The grain-to-feature size ratio (d/Dc) in micro-forming processes is predicted to have a critical impact on the material behavior in addition to the well-known effect of the grain size (d) itself as manifested by the Hall–Petch relation. In this study, we investigated the “size effects” on the material flow curve of thin sheet metals under hydraulic bulge testing conditions. The ratio of the sheet thickness to the material grain size (N=t0/d) was used as a parameter to characterize the interactive effects between the specimen and the grain sizes at the micro-scales, while the ratio of the bulge die diameter to the sheet thickness (M=Dc/t0) was used to represent the effect of the feature size in the bulge test. Thin sheets of stainless steel 304 (SS304) with an initial thickness (t0) of 51 μm and three different grain sizes (d) of 9.3, 10.6, and 17 μm were tested using five bulge diameters (Dc) of 2.5, 5, 10, 20, and 100 mm. A systematic approach for determining the flow curve of thin sheet metals in bulge testing was discussed and presented. The results of the bulge tests at different scales showed a decrease in the material flow curve with decreasing N value from 5.5 to 3.0, and with decreasing M value from 1961 to 191. However, as M value was decreased further from 191 to 49, an inversed relation between the flow curve and M value was observed; that is, the flow curve was found to increase with decreasing M value from 191 to 49, a new observed phenomenon that has never been reported in any open literature. New material models, both qualitatively and quantitatively, were developed to explain the size effects on the material flow curve by using the N and M as the characteristic parameters of relative size between the grain, the specimen (i.e., sheet thickness), and the part feature (i.e., bulge diameter). The explanation and prediction of the flow curve behavior based on these models were shown to be in good agreement with the bulge test results in this study and in the literature.
126 citations
TL;DR: In this paper, a fully coupled thermo-mechanical model of the friction stir welding process is presented, which shows that the rotation of the shoulder can accelerate the material flow behavior near the top surface.
Abstract: This paper presents a new developed fully coupled thermo-mechanical model of the friction stir welding process. Results indicate that the rotation of the shoulder can accelerate the material flow behavior near the top surface. The material deformation and the temperature field can have relations with the microstructural evolution. The texture of the appearance of the friction stir welds can correlate well with the equivalent plastic strain distributions on the top surface. The temperature field in the friction stir welding process is approximately symmetric to the welding line. The material flows in different thicknesses are different. The shoulder can have a significant effect on material behaviors on the top surface, but this effect is greatly weakened when the material gets closer to the bottom surface of the welding plate.
102 citations
TL;DR: It is demonstrated that a dynamic model of an integrated supply chain can serve as a valuable quantitative tool that aids in such decision-making in the management of supply chain activities.
99 citations
TL;DR: In this paper, a steady-state simulation of friction stir welding based on a prior computational method developed in [Bastier, A., Maitournam, M.H., Dang Van, K., Roger, F., 2006] is presented.
88 citations
TL;DR: In this paper, a model of material flow during friction stir welding is proposed for which the weld nugget forms as surface material extrudes from the retreating side into a plasticized zone surrounding the FSW pin.
85 citations
TL;DR: Several material flow metrics used to characterize system behavior that are derived from the ecological development of input-output techniques are concerns; most notable of these metrics are several measures of material cycling and a measure of the number of processes visited by material while in a system.
Abstract: This article, continuing with the themes of the companion article, expounds the capabilities of input-output techniques as applied to material flows in industrial systems. Material flows are the primary focus because of their role in directly linking natural and industrial systems and thereby being fundamental components of environmental issues in industrial economies. The specific topic in this article concerns several material flow metrics used to characterize system behavior that are derived from the ecological development of input-output techniques; most notable of these metrics are several measures of material cycling and a measure of the number of processes visited by material while in a system. These metrics are shown to be useful in analyzing the state of material flow systems. Further-more, the metrics are shown to be a central link in connecting input-output flow analysis to synthesis (i.e., the process of using measurements of system behavior to design changes to that system). By connecting the flow metrics to both environmental objectives and controllable aspects of flow models, changes to existing flow systems are synthesized to generate improved system behavior. To bring this pair of articles to a close, several limitations of input-output flow analysis are summarized with the goal of stimulating further interest and research.
70 citations
TL;DR: In this paper, a multi-method multi-scale comparative study of selected terrestrial transport modalities is presented, which is achieved by investigating the Italian transportation system by means of four different evaluation methods: material flow accounting (MFA), embodied energy analysis (EEA), exergy analysis (EXA), and emergy synthesis (ES).
62 citations
TL;DR: In this paper, a hardness-based flow stress and fracture model for machining AISI H13 tool steel was developed and implemented in a nonisothermal viscoplastic numerical model to simulate the influence of work material hardness on chip formation process.
58 citations
TL;DR: In this paper, the authors present an approach to packaging system assessment which considers the division manager's span of control, addresses the design of packaging and the corresponding logistics processes, and incorporates both cost and environmental impacts.
TL;DR: In this article, the use of material planning methods to control material flow to inventories of purchased items is studied, based on survey data from 153 manufacturing and 53 distribution companies, and the results show that the performance of applying a material planning method differs depending on where along the material flow they are applied, whether the inventory is located in manufacturing or in distribution operations and between companies of various sizes.
Abstract: This paper focuses on the use of material planning methods to control material flow to inventories of purchased items. The first sub-objective is to evaluate the perceived planning performance of material planning methods used to control material flows in different inventory types in manufacturing and distribution companies. The second sub-objective is to evaluate the difference in perceived planning performance depending on the way planning parameters are determined and the methods used. Five material planning methods are studied: the re-order point method, the fixed order interval method, run-out time planning, Kanban and MRP. Our analysis is based on survey data from 153 manufacturing and 53 distribution companies. Findings conclude that the use of material planning methods differs depending on where along the material flow they are applied, whether the inventory is located in manufacturing or in distribution operations and between companies of various sizes. The modes of applying a material planning method affect its perceived performance. In particular, the way of determining and the review frequency of safety stocks and lead times have great importance for the planning performance of MRP methods, while the determination and review of order points, review frequencies and run-out times were important for re-order point methods.
TL;DR: In this article, the authors investigated the material flow characteristics of buttjoints between AA6181-T4 Al alloy and high-strength DP600 steel using electron back-scattered diffraction (EBSD).
Abstract: Friction-stir welding (FSW), considered to be the most significant development in metal joining in a decade, has been the subject of much scientific interest and industrial application. Developed and patented in 1991 at The Welding Institute (TWI) in the UK, the FSW joining process is based on extreme plastic deformation in the solid state and no associated bulk melting is involved. Its application has been guided by a pressing industrial need, successfully applied to the joining of Al alloys, and it appears to be a promising process for joining dissimilar alloys. In recent years, transportation systems have increasingly used light-weight materials, such as high strength steels, Al alloys and Mg alloys, to save energy and reduce pollution. The need to combine such different materials into a hybrid material system, e.g. car bodies and aircraft, is the force driving the development and improvement of welding techniques including FSW. Different concepts for tool materials have lead to increasing interest in FSW of steels as well as of steel-based dissimilar welds. Compared to fusion welding techniques, solid-state welding processes such as FSW have particular advantages for joining dissimilar materials with very different melting intervals and large differences in physical and mechanical properties. It has been shown that mild steels, stainless steels and high strength steels can be friction-stir welded to Al alloys and that the comparatively low heat input characteristic of the process reduces or even prevents the formation of brittle intermetallic phases. In FSW, the joint is created by frictional heating and associated stirring or forging action as the tool moves along the joint interface. Hence, tool geometry, welding parameters, joint design and the materials to be welded exert significant effects on the material flow pattern and temperature distribution. An understanding of the mechanical and thermal processes during FSW is needed for optimising process parameters and controlling the microstructure and properties of the joints. In particular, material flow and operating mechanisms during FSW are not fully characterised. These factors are, however, crucial to the optimisation of tool geometry and welding procedure that is necessary to obtain high structural efficiency welds. Thus, an increase in the number of approaches to investigating material flow during FSW has been observed in the literature. Reynolds et al. used a marker insert technique to provide a qualitative characterisation of material flow metallographically. They described FSW as an in-situ extrusion process where the tool shoulder, the pin, the backing plate, and the cold base material form an extrusion die, where the hot material is extruded around both sides of the pin (leading and trailing) into the cavity being vacated by the pin as it moves forward. Complex material movement has also been analysed in dissimilar joints and has been described as chaotic-dynamic, consisting of vortex-like and swirl features by Murr et al. Moreover, computational methods and tomography techniques appear to be helpful techniques for quantifying and visualising material flow. We investigated the material flow characteristics of buttjoints between AA6181-T4 Al alloy and high-strength DP600 steel. The investigations involved analyses by scanning electron microscopy (SEM) combined with electron back-scattered diffraction (EBSD). EBSD is a SEM add-on package that allows local crystallographic analysis of crystalline microstructure. EBSD has been widely used to investigate morphology, grain size distribution and crystallographic orientation (texture) of similar and dissimilar friction stir welds but so far has not been applied to material flow visualisation. EBSD shows great potential for grain characterisation (quantitative size, shape and aspect ratio) and provides important insight into the material flow analysis. Some microstructure features are also presented in order to correlate the microstructure and material movement with the welding process. C O M M U N IC A IO N S
TL;DR: In this paper, a rate-dependent constitutive model was used to investigate the role of extrusion of pin on transport of the material in friction stir welding, and the results indicated that the extrusion can affect the material flow near the shoulder-plate interface.
Abstract: Friction stir welding is a new solid state joining technology, which is suitable for joining some hard-to-weld materials, such as aluminum alloy, magnesium alloy, etc. The modeling of material flows can provide an efficient method for the investigation on the mechanism of friction stir welding. So, 3D material flows under different process parameters in the FSW process of 1018 steel are studied by using rate-dependent constitutive model. Numerical results indicate that the border of the shoulder can affect the material flow near the shoulder–plate interface. The mixture of the material in the lower half of the friction stir weld can benefit from the increase in the angular velocity or the decrease in the welding speed. But flaws may occur when the angular velocity is very high or the translational velocity is very small. When the angular velocity applied on the pin is small or the welding speed is high, the role of the extrusion of pin on transport of the material in FSW becomes more important. Swirl or vortex occurs in the tangent material flow and may be easier to be observed with the increase in the angular velocity of the pin.
TL;DR: The use of high-speed filming allows observing a sequence of frozen images focused on the chip formation area when machining steel in orthogonal turning tests is described in this article.
TL;DR: In this article, a 3D Finite Element (FE) model was developed to simulate the bending process, based on the experimental conditions, and the results showed that it is possible to adopt a two-step forming process, "bending" and "flow forming", to enable material flow along the mandrel in order to form a thin-wall cup component using two different profiles and adopting an axial roller movement.
TL;DR: In this paper, the authors used the discrete element method (DEM) where each particle is tracked for its position, velocity, and acceleration, and the typical shift from mass flow to funnel flow depending on the hopper angle was successfully simulated.
Abstract: Flow characteristics of material in hoppers, silos, and bins are critical issues for operational stability as well as structural integrity of these units. In this work, flow of noncohesive particles in hopper is studied using the discrete element method (DEM) where each particle is tracked for its position, velocity, and acceleration. Material properties tend to alter during hopper flow due to compaction, expansion, and segregation. These features are difficult to model with a continuum approach. In the first part, material flow patterns are correlated with hopper angle and hopper opening, the two main design parameters. The typical shift from mass flow to funnel flow depending on the hopper angle was successfully simulated. In the second part, the discharge rate of material was quantitatively analyzed as function of hopper design parameters. Beverloo model 1 was tested on these simulated flow rates and it was shown that the simulated flow rates follow the model for this specific granular system. However,...
TL;DR: In this paper, the authors track material flow in FSW between 1mm thick sheets in aluminium alloys AA 5182-H111 and AA 6016-T4, currently used in automotive industry.
Abstract: Friction stir welding (FSW) is a solid-state joining technique initially developed for aluminium alloys. The heat generated by a rotating tool softens the material in the vicinity of the tool. The material undergoes intense plastic deformation following quite complex paths around the tool, depending on the tool geometry, process parameters and material to be welded. The comprehension of the material flow is essential to prevent voids and other internal defects which may form during welding. Several techniques have been used for tracking material flow during FSW such as metallography, the use of a marker material as a tracer or the flow visualization by FSW of dissimilar materials or even the X-ray and computer tomography. Some of these techniques are useless in the analysis of welds in homogenous materials or welds between materials of the same group. The aim of this investigation is tracking the material flow in FSW between 1mm thick sheets in aluminium alloys AA 5182-H111 and AA 6016-T4, currently used in automotive industry.
TL;DR: In this paper, the flow behavior in friction stir processing of metals is investigated by tracking the motion of discrete particles and grid deformation in a plasticine workpiece, where the forward motion of the tool is stopped nearly instantaneously to freeze the flow of material around the tool.
TL;DR: In this paper, an energy and material flow model of hydrogen production via steam reforming of methane in the U.S. Chemical Industry is presented. But the model is not suitable for the analysis of large-scale hydrogen production.
TL;DR: In this paper, an energy and material flow analysis (EMFA) is applied to the case of the manufacture of roof tiles in a ceramic industry, where a computational tool, Umberto, was used for the analysis.
TL;DR: In this paper, the results of both an experimental and a numerical campaign focused on the analysis of the occurring material flow in the FSW of T joints of aluminum alloys are presented.
Abstract: In the paper the authors present the results of both an experimental and a numerical campaign focused on the analysis of the occurring material flow in the FSW of T joints of aluminum alloys. In particular to investigate the metal flow experimental tests and observations has been developed utilizing a thin foil of copper as marker placed between the skin and the stringer. In this way, the actual metal flow occurring during the FSW of T-joints has been highlighted together with the real bonding surface. The acquired information is definitively useful in order to choose effective set of process parameters, improving the process mechanics and avoiding the insurgence of defects.
TL;DR: In this paper, the geometry of a conical tool as well as welding parameters for the friction stir welding of thin plates of a given material are defined based on a concept that the tool geometry and process parameters must satisfy four heuristics: a thermal condition and rules relevant to volume, surface and material flow.
Abstract: The friction stir welding is a solid state welding process which has been successfully applied for industrial parts. The process development has been supported by experimental and theoretical studies related to weld outcome, material flow and tool geometry. In this study, we propose a new methodology to define the geometry of a conical tool as well as welding parameters for the friction stir welding of thin plates of a given material. This is based on a concept that the tool geometry and process parameters must satisfy four heuristics: a thermal condition and rules relevant to volume, surface and material flow. This all should tend to ensure that the matter reaches an appropriate processing temperature and remains confined to the tool zone without any loss to the surroundings. A calculation algorithm that integrates a basic thermal model, tool geometry and process kinematics is proposed. The methodology and details of tool design are further discussed in relation with the definition of a process window. Experimental investigations on Al 2017-T4 alloys by using a shouldered unthreaded conical tool are presented in support of the model. The outcome of the model and experimental studies is further substantiated by using the published results.
TL;DR: In this paper, a 3D simulation of a Mannesmann tube piercing is performed using the finite element software Forge 2005 and the sensitivity of the simulation results to numerical methods and physical parameters is discussed.
Abstract: A 3D simulation of Mannesmann tube piercing is performed using the finite element software Forge 2005®. The sensitivity of the simulation results to numerical methods and physical parameters is discussed. Advanced numerical schemes and refined time discretizations are required to obtain correct descriptions of the material flow. In this study, one concentrates on the stress state and damage development before the material comes in contact with the plug. Indeed, the crack is to appear prior to the action of the plug. The description of the material behaviour is found to be a key information to predict the crack development. Predictions based on a modified Lemaitre damage law and a normalised Latham and Cockroft criterion are compared.
TL;DR: In this paper, the authors describe the application of economy-wide material flow accounting and analysis to the economy of the Czech Republic for 1990-2002, showing a decrease of material intensity and decoupling of the economic growth from environmental pressure.
Abstract: Material and energy flows (together with human appropriation of land) are considered the key cause of environmental problems. This paper describes the application of economy-wide material flow accounting and analysis to the economy of the Czech Republic for 1990-2002. The results show a decrease of material intensity and decoupling of the economic growth from environmental pressure. The second part of the paper treats an important issue of uncertainties related to economy-wide material flow indicators in the Czech Republic. The results point out that the high uncertainties related to some material flow indicators may be an obstacle to their applicability.
TL;DR: A branch-and-bound procedure is developed by using the special material flow property of the balanced unidirectional cyclic layout problem (BUCLP) and a dynamic programming algorithm is proposed, which provides optimum solutions for instances with up to 20 workstations due to memory limitations.
01 Jan 2008
TL;DR: In this paper, a global thermal model us- ing the temperature dependent heat source and a local material flow and heat generation model allowing for detailed investigation of dierent contact conditions is presented.
Abstract: Two Friction stir welding mod- els are presented - a global thermal model us- ing the temperature dependent heat source and a local material flow and heat generation model allowing for detailed investigation of dierent contact conditions. The two models are coupled into a larger local-global model. The flow model includes frictional dissipa- tion from the contact between the workpiece and the tool as well as plastic dissipation.
TL;DR: In this paper, a simulation-based optimization method is used to optimize inhomogeneous wall thicknesses in composite profiles, where the insertion of reinforcement elements into the base material flow, especially within the small ratio between profile thickness and the reinforcement diameter, can lead to significant local disturbances inside the die.
Abstract: The decrease of the bearing length in extrusion processes results in increasing of the material flow and offers, through this, the possibility for manipulation and optimization. This paper presents a simulation based optimization technique which uses this effect for optimizing the material flow in direct extrusion processes. Firstly, the method is used in a multi-extrusion process with equal pitch circle profiles, then in an extrusion process of an asymmetric profile. Furthermore, a composite extrusion process is analyzed where endless wires of high strength steel are embedded in a base material of aluminum. The insertion of reinforcement elements into the base material flow, especially within the small ratio between profile thickness and the reinforcement diameter, can lead to significant local disturbances inside the die, which result in undesirable profile defects. Hence, the simulation-based optimization method is especially used to optimize inhomogeneous wall thicknesses in composite profiles.
TL;DR: In this paper, the authors propose new concepts in the domain of material flow and device control like function-oriented modularization and intelligent multi-agent-systems offer the possibility to employ changeable and automated material flow systems in dynamic production structures.
Abstract: Logistics Journal : referierte Veroffentlichungen, Vol. 2008, Iss. April - Today’s material flow systems for mass customization or dynamic productions are usually realized with manual transportation systems. However new concepts in the domain of material flow and device control like function-oriented modularization and intelligent multi-agent-systems offer the possibility to employ changeable and automated material flow systems in dynamic production structures. These systems need the ability to react on unplanned and unexpected events autonomously.