Showing papers on "Material flow published in 2004"

Thermomechanical modelling of oblique cutting and experimental validation

Abstract: An analytical approach is used to model oblique cutting process. The material characteristics such as strain rate sensitivity, strain hardening and thermal softening are considered. The chip formation is supposed to occur mainly by shearing within a thin band called primary shear zone. The analysis is limited to stationary flow and the material flow within the primary shear zone is modelled by using a one-dimensional approach. Thermomechanical coupling and inertia effects are accounted for. The chip flow angle is determined by the assumption that the friction force on the tool face is collinear to the chip flow direction. At the chip–tool interface, the friction condition can be affected by the important heating induced by the large values of pressure and sliding velocity. In spite of the complexity of phenomena governing the friction law in machining, a reasonable assumption is to consider that the mean friction coefficient is primarily function of the average temperature at the tool–chip interface. Comparisons between model predictions and experimental results are performed for different values of cutting speed, undeformed chip thickness, normal cutting angle and inclination angle. A critical study is presented in order to show the influences of the input parameters of the model including the normal shear angle, the thickness of the primary shear zone and the pressure distribution at the tool–chip interface. The model permits to predict the cutting forces, the chip flow direction, the contact length between the chip and the tool and the temperature distribution at the tool–chip interface which has an important effect on tool wear.

Reducing uncertainty in European supply chains

Abstract: In this paper, we show that reducing supply chain uncertainty increases responsiveness and thereby benefits bottom line performance as assessed via total cycle time reduction. We term this effect as the uncertainty reduction principle. To enable uncertainty reduction we use the uncertainty circle to focus on the sources to be eliminated. We also show that these sources of uncertainty can react and magnify in a flywheel effect caused by poor supply chain management. A supply chain audit methodology is described for identifying and codifying uncertainty. The proposition advanced herein is that smooth material flow leads to and statistically correlates with uncertainty reduction. Examples are given of good real‐world supply chain practices thus identified and subsequently improved. Transferability of the uncertainty reduction principle is assured by establishing readily assimilated “best practice” guidelines via the study of “exemplar” operating characteristics.

Proposal of six indicators of material cycles for describing society's metabolism: from the viewpoint of material flow analysis

Abstract: The first essential step toward promoting material cycling (recycling) is to understand the current state of the material cycles in a society. However, the types of material cycles that we should document and the methods of their quantification are not standardized. In addition, an important factor in promoting material cycling is the establishment of the indicators that will enable objective measurement of the effectiveness of policies and actions. This paper categorizes the forms of material cycles that we should document, discusses their characteristics, and proposes six indicators of material cycles for describing society's metabolism. We reached the following conclusions: (1) the forms of material cycles fall into three types, according to differences in how they are quantitatively measured and how they contribute to the objectives of material cycling: reuse of used products, recovery of by-products (as material and heat), and recovery of used products (as material and heat). They should be considered separately in terms of measuring material cycles and in establishing indicators of material cycles; (2) six indicators for measuring the material cycles are proposed, on the basis of the types and objectives of material cycling: direct material input (DMI), use rate of recovered used products (URRUP), material use efficiency (MUE), material use time (MUT), recovery rate of used product (RRUP), and domestic processed output (DPO). They reflect the main points in life cycles of materials; (3) three practical problems in capturing material flows and calculating the indicators exist: to capture by-products and used products that are not captured in current statistics, to distinguish between by-products and used products, and to capture product stocks.

A New Decomposition Approach for Non-Cyclic Continuous Material Flow Lines with a Merging Flow of Material

Abstract: We extend the decomposition approaches for flow lines with unreliable machines and limited buffer capacity as proposed by Gershwin and refined by Dallery, David, and Xie and by Burman by incorporating a new building block in the decomposition. This new building block is a three-machine, one buffer system which models a merging flow of material. While previous decomposition approaches led to a decomposition of the original network into virtual two-machine lines, we now use both virtual two- and three-machine lines. This requires a new set of decomposition equations for the virtual machines of the two-machine lines that surround the new building block modelling the merge. We present these equations, show how to solve them in an algorithm and present numerical results for non-cyclic networks in order to determine production rate and inventory level estimates.

Materials count : the case for material flows analysis

Abstract: The rising population and industrial growth place increasing strains on a variety of material and energy resources. Understanding how to make the most economically and environmentally efficient use of materials will require an understanding of the flow of materials from the time a material is extracted through processing, manufacturing, use, and its ultimate destination as a waste or reusable resource. Materials Count examines the usefulness of creating and maintaining material flow accounts for developing sound public policy, evaluates the technical basis for material flows analysis, assesses the current state of material flows information, and discusses who should have institutional responsibility for collecting, maintaining, and providing access to additional data for material flow accounts.

Plastic fans having improved fan ring weld line strength

Abstract: Injection molded ring fan embodiments and methods for making them. The methods influence material flow during the injection molding process such that a major portion of the materials flowing in opposite directions in the outer rings preferably flow past one another, intermix in a swirling relationship, and/or collide at an angle relative to one another. This results in better material mixing or integration of the flow fronts. In one embodiment, the thickness of the outer ring varies in different portions between adjacent fan blades.

Heat source models in simulation of heat flow in friction stir welding

Abstract: The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in friction stir welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms. The convective heat transfer due to the material flow affects the temperature fields. Models presented previously in the literature allow the heat to flow through the probe volume, and the majority neglects the influence of the contact condition as the sliding condition is assumed. In this work, a number of cases is established. Each case represents a combination of a contact condition, i.e. sliding and sticking, and a stage of refinement regarding the heat source distribution. In the most detailed models, the heat flow is forced around the probe volume by prescribing a velocity field in shear layers at the tool/work piece interface. This results in a nonsymmetrical temperature field that depends not only on the total heat generation, tool/work piece geometry and thermal properties, but also on the contact condition, the tool’s rotational speed and the assumed shear layer thicknesses. The models are implemented in FEMLAB and configured in terms of the heat source as: shoulder contribution only; shoulder and probe contribution, the latter as a volume heat source distributed in the probe volume; and shoulder and probe contribution distributed at the contact interface, i.e. as a surface flux in the case of sliding and as a volume flux in the shear layers in the case of sticking.

Material flow analysis and integration of watersheds and drainage systems: I. Simulation and application to ammonium management in Bahr El-Baqar drainage system

Abstract: This paper is aimed at developing a systematic and generally applicable methodology for material flow analysis in drainage systems and watersheds. In particular, this research has focused on developing a mathematical framework and application for the management of nitrogenous species (primarily ammonium ions). Nitrogen compounds are among the most important species contributing to ecological cycles. Indeed, the environmental and biological aspects of water systems and their surrounding systems are highly impacted by nitrogen compounds as they contribute to the quality, nutrition, and toxicity of these systems. A material flow model was developed to deal primarily with the water phase while including pertinent information on the solid and air phases as they interface with the water medium. Both spatial and discrete temporal dimensions were included to account for nitrogen flow and transformation. The model includes the various environmental phenomena that influence the fate and transport of targeted species (e.g., volatilization, precipitation, sedimentation, uptake by biota, adsorption, chemical and biochemical reactions, etc.). Furthermore, the model includes material flow analysis operators (or transfer functions) that characterize the system inputs and outputs as they relate to the surroundings. The aforementioned material flow analysis tools were combined in a computer-aided modeling platform to provide a complete material flow analysis and yield useful insights on the transport and fate of targeted species. The simulation results shed light on the system performance. Actual data for an Egyptian drainage system (Bahr El-Baqar) along with the outfall to Lake Manzala were used to illustrate the usefulness and applicability of the developed model. Comparison with the measured data confirmed the validity and fidelity of the model.

Data defects in material flow networks—classification and approaches

Abstract: First the basics of ecobalancing are briefly explained. In this connection the main focus is set on material flow networks. In the software tool Umberto®, material flow networks are used to model material flows, which are necessary for creation of inventory analysis. Furthermore, data defects in material flow networks are classified, and causes and consequences of these data defects are pointed out. Afterward, possible solutions with their benefits and drawbacks are proposed. A case study (life-cycle assessment of a coating material) shows both data defects and some solution attempts. Finally a short outlook outlines some other approaches, which should be investigated in future work.

Method and device for separating a flow of crops

Abstract: A flow of crops, which contains useful material and waste material, is separated in a crop machine into a useful material flow and a waste material flow, in which, respectively, the useful material or the waste material is concentrated. A first step separates the flow of crops with a first selectivity into a pre-cleaned flow, which contains a substantial portion of the useful material and a remaining portion of the waste material, and a first waste material flow, which contains a substantial portion of the waste material and a remaining portion of the useful material. A second step separates the pre-cleaned flow with a selectivity dependent on its flow rate into the useful material flow and a second waste material flow, which contains a substantial portion of waste material and a remaining portion of the useful material. A quantity combined from the amount of the useful material into the waste material flow is detected continuously, and the first selectivity is regulated based on this quantity, independently from the flow rate of the flow of crops (S3, S4).

Material Flow Accounting for Metals in Japan

Abstract: Planning transition from conventional mass production, mass consumption, and mass disposal society to JUNKANGATA-SHAKAI (recycling-oriented society), requires detailed and accurate information concerning material flows, especially from the viewpoint of dematerialization. However, as is well known, it is nearly impossible to observe every material flow directly. Hence, the importance of Material Flow Accounting model has increased. In this study, a Material Flow Accounting model using input-output technique is developed for Japanese metal flows. Since the model uses the Input-Output framework, it can be easily integrated with the MIOT (Monetary Input-Output Table) for further simulation. However, the scope of this study is limited to static framework, because the primal goal is accuracy. The data for year 2000 is organized with the developed framework, and gives the following results. Firstly, scraps play significant roles already. Second, non-ferrous metals can be grouped into two types. The first group's destination is mainly construction and machinery and these non-ferrous metals show the similar pattern of destination as iron. This indicates that the flows can be roughly predicted from the iron flows. The other group shows no uniform trend so that the flows are more difficult to predict than the first group.

Microstructure, material flow and tensile properties of A356 alloy thixoformed parts

Abstract: The present work examines microstructure, tensile properties and quality (porosity level) of two thixoformed products, namely an assembly of three cylindrical rods from which tensile samples were machined out, and a cup-shaped part. The material is an A356 aluminium alloy and the microstructural conditioning was carried out by the deformation - recrystallization technique. Additionally, the microstructures of an A356 ingot produced by the magnetic stirring process was also investigated. Results showed that solid fraction and soaking time in the semi-solid state determine the thixoforming forces, that very low porosity levels can be achieved and minimized by the maintenance of high pressures during solidification, and that the material flow during injection in the mould is relatively homogeneous, except for the material conditioned by magnetic stirring. Physical simulation experiments of the thixoforming process (rods) showed a strong correlation between liquid segregation and porosity level. Finally, the tensile properties were shown to be much higher that those of permanent cast samples.

Mapping flows - An analysis of the information flows within the integrated supply chain

Abstract: Information sharing is an important factor for cooperating within an integrated supply chain. This paper presents a methodology for mapping information flows in an integrated supply chain and a case study, using the mapping methodology, from two Swedish multinational organizations. Eight cases where used in a retro perspective way to map, describe and analyze the information flow, which supports the physical material flow, from receiving an order to the point of delivery. This paper also describes two types of information flows: Direct information and indirect information. The case study presented in this paper focus on the direct information. The present study indicates the importance of an integrated, updated and smoothly operating information system. The complexity and the performance of the information flow and the physical material flow within each case where also analyzed from three main perspectives: 1) the right information, 2) at the right time, 3) to the right place. Over 30 semi-structured interviews have been made to map and describe the information and physical material flow. Key personnel involved in the process from order to point of delivery where interviewed. One conclusion of the study is that three types of disturbances was domination the cases: 1) Procedures to handle changes in an order from a customer, 2) lack of information within the internal supply chain, and 3) Procedures to handle information about delays in internal production or wrong material delivered.

Recovery Planning in Closed Loop Supply Chains: An Activity Analysis Based Approach

Abstract: Due to the latest developments in European environmental legislation, supply chains in most major industrial branches have to be closed and producers will be responsible for collecting, sorting and recovery of discarded products at the end of their service life. Therefore, a close cooperation with recovery companies and their integration in producers supply chains, e.g. as suppliers of spare parts and secondary raw materials, will be necessary. A cost-efficient management of material flows between suppliers, producers, customers and recovery companies requires an integrated information management as well as advanced planning systems between all members of the supply chain. The paper focuses on the design and implementation of a decision support system for electronic scrap recovery companies in closed loop supply chains. This requires an efficient provision of relevant information, so that at the beginning of this paper a concept for the inter-organizational information management is presented. Then, based on detailed empirical analysis of disassembly and bulk recycling processes, an activity analysis based material flow model will be developed and the required capacity of the disassembly and recycling processes will be determined. Due to high uncertainties in the amount, composition and quality of the delivered electronic scrap, the long term capacity planning has to be supplemented by a detailed short term planning at regular intervals. The decision support system has been implemented in a major German electronic scrap recovery company and validated by real data.

Device and method for controlling fuel cell system and fuel cell system

Abstract: A fuel cell system has a fuel cell generating power using a fuel gas and an oxidizing agent gas serving as materials of the system and a material supply section supplying the materials to the fuel cell. The power generated by the fuel cell is extracted to a load. A device for controlling the fuel cell system has: a material flow calculation section calculating a material flow supplied to the fuel cell so as to cause the fuel cell to generate the power of a required power generation amount; a material reduction limit detection section calculating a limit for reducing the material flow, based on a power generation state of the fuel cell; and a material flow change section controlling the material supply section so as to change the material flow calculated by the material flow calculation section to the limit calculated by the material reduction limit detection section.

Analytical and numerical investigations into belt conveyor transfers

Abstract: The mining industry is an immense field with granular flows (e.g. coal) occurring in numerous areas. Accordingly there are a significant number of problems that arise, with a great number requiring solutions that are difficult to achieve by conventional industrial means. The modelling of granular flow using the numerical technique known as Distinct Element Method (DEM) has great potential in industry, particularly for solving transfer point problems. The advantage of DEM for transfer applications is that an entire system can be simulated using the single numerical technique, as opposed to the existing situation where a myriad of design techniques are required (e.g. analytical solution for one component and graphical solution for another). DEM involves solving the equations of motion for the trajectory/rotation/orientation of each particle and modelling each collision between particles and between particles and boundary objects. The research presented a comprehensive overview of all of the available analytical processes available to design chute system components, such as material trajectory calculations, impact plate models, and gravity flow chute aspects. To the author’s knowledge, this was the first such review in the literature. A detailed comparison between the most common analytical design methods was conducted, recommendations for which method to use were established, and areas of weakness and further study were identified. It was found that: most areas apart from the prediction of the initial material discharge and trajectory were lacking in design method; often the few available design methods for chute components, such as impact plates and gravity flow chutes, were lengthy and often difficult to implement. A computer code was developed during the course of the research to simulate bulk material using the Distinct Element Method (DEM). A background into DEM and its application to modelling material flow at transfer points was presented. One major drawback found in the recent transfer studies was the lack of quantification of the velocity distributions obtained using the DEM against existing analytical design theories. Contour coloured particulate simulations have also been recently produced by a number of companies (e.g. Overland Conveyor Company Inc.) however the flow

An investigation of the unstable region for dense phase conveying in sliding bed flow

Abstract: For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem.

Feasibility of High Speed Furnace Drawing of Optical Fibers

Abstract: The domain of operating conditions, in which the optical fiber-drawing process is successful, is an important consideration. Such a domain is mainly determined by the stresses acting on the fiber and by the stability of the process. This paper considers an electrical resistance furnace for fiber drawing and examines conditions for process feasibility. In actual practice, it is known that only certain ranges of furnace temperature and draw speed lead to successful fiber drawing. The results obtained here show that the length of the heated zone and the furnace temperature distribution are other important parameters that can be varied to obtain a feasible process. Physical behavior close to the boundary of the feasible domain is also studied. It is found that the iterative scheme for neck-down profile determination diverges rapidly when the draw temperature is lower than that at the acceptable domain boundary due to the lack of material flow. However, the divergence rate becomes much smaller as the temperature is brought close to the domain boundary. Additional information on the profile determination as one approaches the acceptable region is obtained. It is found that it is computationally expensive and time-consuming to locate the exact boundary of the feasible drawing domain. From the results obtained, along with practical considerations of material rupture, defect concentration, and flow instability, an optimum design of a fiber-drawing system can be obtained for the best fiber quality.

A study on the spatial distribution of nitrogen and phosphorus balance, and regional nitrogen flow through crop production.

Abstract: The spatial distribution patterns of the nitrogen and phosphorus input/intake amounts in crop production within two small basins are examined, based upon a cropping unit distribution map that is obtained from remote sensing data analysis. Firstly, we examine the availability and suitability of approaches to the spatial distribution analysis of cultivation patterns classified from material flow characteristics of crop production using seasonal remote-sensing data. Secondly, material flow units in crop production are grouped according to the cultivation patterns obtained from the remote-sensing data analysis. Consequently, the spatial patterns of the amounts of both nitrogen and phosphorus inputs/intakes through crop production on farmland are examined and their spatial distribution maps are prepared according to the material flow units. In addition, we developed a nitrogen flow and runoff model and the model is simulated based on the examination of the results of spatial distribution patterns of the material flow units. The annual nitrogen runoff from small catchments, where various crops are cultivated, varies from 2.7 kg ha−1 year−1 to 108 kg ha−1 year−1 and the annual balanced losses of nitrogen in small catchments varied from −30 kg ha−1 year−1 to 101 kg ha−1 year−1. Also, the monthly changes in soil nitrogen of each material flow unit is estimated at −55 kg ha−1 as a maximum decrease and 114 kg ha−1 as a maximum increase. These results indicate that the spatial distribution patterns of nutrient input and intake through agricultural activities should be considered when analyzing the material flows and nutritient movement in soil–water systems in rural areas for watershed environmental control and regional agricultural management.

Non‐Dimensional Characterization of the Friction Stir/Spot Welding Process Using a Simple Couette Flow Model Part I: Constant Property Bingham Plastic Solution

Abstract: A simplified model for the material flow created during a friction stir/spot welding process has been developed using a boundary driven cylindrical Couette flow model with a specified heat flux at the inner cylinder for a Bingham plastic material. Non‐dimensionalization of the constant property governing equations identified three parameters that influence the velocity and temperature fields. Analytic solutions to these equations are presented and some representative results from a parametric study (parameters chosen and varied over ranges expected for the welding of a wide variety of metals) are discussed. The results also provide an expression for the critical radius (location of vanishing material velocity) as functions of the relevant non‐dimensional parameters. A final study was conducted in which values for the non‐dimensional heat flux parameter were chosen to produce peak dimensional temperatures on the order of 80% of the melting temperature for a typical 2000 series aluminum. Under these conditi...

Tri-flow head assembly

Abstract: A head assembly for presenting a three layer material flow includes primary and secondary housings for presenting a first interior layer and a second intermediate layer of the three layer flow. A downstream melt distributor melds the first and second material layers into a combined material flow for deposit of a third exterior layer about the combined flow. The melt distributor includes a sinuous channel for directing the material of the outer layer into points of discharge about the combined material flow. A scroll-like distributor communicates with the discharge points for directing the third material into an annular path about the combined flow, and a subsequent melding of the third material with the combined flow. The resulting three layer flow is directed to a downstream die assembly.

Material flow analysis in closed-loop supply chains: modelling of packaging waste recycling at different hierarchical levels

Abstract: Due to recent trends in environmental legislation, closed-loop systems are becoming increasingly important not only for countries and regions, but also for firms that have to fulfill product responsibilities. Therefore, Supply Chain Management (SCM) has to be extended to Closed-Loop Supply Chain Management (CLSCM). As a quantitative basis, Material Flow Analysis helps to structure the complex cyclic network and to map several processes. The article describes an approach to the modelling of cyclic systems at different hierarchical levels, using the packaging recycling system as an example. It gradually refines a general closed-loop framework into material flow charts (top down procedure). Additionally, it offers elementary models for building up transformation networks (bottom-up procedure). These building blocks are distinguished by transformation type and process flexibility and can be linked directly to optimising operations research models.