Showing papers on "Material flow published in 2007"

A mixed-unit input-output model for environmental life-cycle assessment and material flow analysis.

Abstract: Materials flow analysis models have traditionally been used to track the production, use, and consumption of materials. Economic input-output modeling has been used for environmental systems analysis, with a primary benefit being the capability to estimate direct and indirect economic and environmental impacts across the entire supply chain of production in an economy. We combine these two types of models to create a mixed-unit input-output model that is able to bettertrack economic transactions and material flows throughout the economy associated with changes in production. A 13 by 13 economic input-output direct requirements matrix developed by the U.S. Bureau of Economic Analysis is augmented with material flow data derived from those published by the U.S. Geological Survey in the formulation of illustrative mixed-unit input-output models for lead and cadmium. The resulting model provides the capabilities of both material flow and input-output models, with detailed material tracking through entire supply chains in response to any monetary or material demand. Examples of these models are provided along with a discussion of uncertainty and extensions to these models.

The Waste Input-Output Approach to Materials Flow Analysis

Abstract: A general analytical model of materials flow analysis (MFA) incorporating physical waste input-output is proposed that is fully consistent with the mass balance principle. Exploiting the triangular nature of the matrix of input coefficients, which is obtained by rearranging the ordering of sectors according to degrees of fabrication, the material composition matrix is derived, which gives the material composition of products. A formal mathematical definition of materials (or the objects, the flow of which is to be accounted for by MFA) is also introduced, which excludes the occurrence of double accounting in economy-wide MFAs involving diverse inputs. By using the model, monetary input-output (IO) tables can easily be converted into a physical material flow account (or physical input-output tables [PIOT]) of an arbitrary number of materials, and the material composition of a product can be decomposed into its input origin. The first point represents substantial saving in the otherwise prohibitive cost that is associated with independent compilation of PIOT. The proposed methodology is applied to Japanese IO data for the flow of 11 base metals and their scrap (available as e-supplement on the JIE Web site).

Identification of Constitutive Material Model Parameters for High-Strain Rate Metal Cutting Conditions Using Evolutionary Computational Algorithms

Abstract: Advances in plasticity-based analytical modeling and finite element methods (FEM) based numerical modeling of metal cutting have resulted in capabilities of predicting the physical phenomena in metal cutting such as forces, temperatures, and stresses generated. However, accuracy and reliability of these predictions rely on a work material constitutive model describing the flow stress, at which work material starts to plastically deform. This paper presents a methodology to determine deformation behavior of work materials in high-strain rate metal cutting conditions and utilizes evolutionary computational methods in identifying constitutive model parameters. The Johnson–Cook (JC) constitutive model and cooperative particle swarm optimization (CPSO) method are combined to investigate the effects of high-strain rate dependency, thermal softening and strain rate-temperature coupling on the material flow stress. The methodology is applied in predicting JC constitutive model parameters, and the results are comp...

Revisiting the fundamentals of metal cutting by means of finite elements and ductile fracture mechanics

Abstract: This paper investigates Atkins’ idea that the modelling of metal cutting must include the significant work involved in the formation of new surfaces as well as the traditional components of plastic flow and friction. New finite element and algebraic calculations are presented together with specially designed orthogonal metal cutting experiments performed on lead specimens under laboratory-controlled conditions. Independent determinations of the mechanical properties of lead were made and comparisons are given between theoretical predictions and experimental results. Calculations cover a wide range of topics such as material flow, chip-compression factor, primary shear plane angle, cutting force and specific cutting pressure. It is shown that the choice of lead as workpiece material reveals important facts that would be obscured were the usual sort of workpiece metals to be cut. The paper demonstrates quantitatively that while material flow, chip formation and the distribution of the major field variables can be modelled successfully by traditional ‘plasticity and friction only’ analyses, the contribution of ductile fracture mechanics is essential for obtaining good estimates of cutting forces and of the specific cutting pressure.

Characterization of machining of AISI 1045 steel over a wide range of cutting speeds. Part 2: evaluation of flow stress models and interface friction distribution schemes

Abstract: To ensure that the simulation of the orthogonal metal-cutting process yields accurate results, the material and frictional behaviours during simulation have to be defined accurately. Flow stress models are used extensively in the simulations of deformation processes occurring at high strains, strain rates, and temperatures. In this work, the Johnson-Cook, Maekawa et al., Oxley, El-Magd et al., and Zerilli-Armstrong flow stress models are evaluated. AISI 1045 steel is used as the workpiece material because it is well characterized. First, the predictive capability of these flow stress models is compared with the published experimental data at high strain rates and the modelling errors are quantified. Different friction conditions along the tool rake face are also discussed. Then the friction conditions based on results of scanning electron microscopy-energy-dispersive X-ray analysis from Part 1 are implemented together with other friction models. The material flow stress models and friction conditi...

Material behaviors and mechanical features in friction stir welding process

Abstract: This paper presents the 3D material flows and mechanical features under different process parameters by using the finite element method based on solid mechanics. Experimental results are also given to study the effect of process parameters on joining properties of the friction stir welds. Numerical results indicate that the tangent flow constitutes the major part in the material flow. The shoulder can accelerate the material flow on the top half of the friction stir weld. The distribution of the equivalent plastic strain can correlate well with the microstructure zones. Increasing the angular velocity of the pin, the material in the nugget zone can be more fully mixed, which improves the joining quality of the two welding plates. The increase of speeds, including the rotational speed and the translational speed, can both accelerate the material flow, especially in front of the pin on the retreating side where the fastest material flow occurs. The contact pressure on the pin-plate interface is decreased with the increase of the angular velocity.

Fluidized bed gasification system

Abstract: A fluidized bed gasification system is provided in which bed material and raw material are passed throughout a fluidized bed gasification furnace so that raw material is gasified with higher gasification efficiency to improve gasification productivity. A heat-resistant partition 32 for regulation of bed material flow is arranged between positions I and II of a downcomer 12 of a separator 8 and of a supply flow passage 25 in plane of a fluidized bed gasification furnace 2. As a result, the bed material introduced via the downcomer 12 is directed to a supply flow passage 25 through a circuitous flow passage 33 throughout the fluidized bed gasification furnace 2 defined by the heat-resistant partition 32.

Microstructure analysis of aluminum extrusion: grain size distribution in AA6060, AA6082 and AA7075 alloys

Abstract: Microstructure and material flow of aluminum alloys have a significant influence on the mechanical properties and surface quality. In extrusion of aluminum billets at high temperatures the microstructure is dependent on the alloy and the forming and temperature history. A prediction of grain size and precipitation is of increasing importance in order to design the process by adjustment of parameters such as punch speed, temperatures, and quenching. To give references for microstructure prediction based on material flow, and with it strain and strain rate history, this paper deals with the microstructure during the extrusion process of AA6060, AA6082, and AA7075 alloys. Billets have been partly extruded to axisymmetric round profiles and the microstructure of the press rests consisting of the billet rests in container and die has been considered. Furthermore, these rests have been analyzed to show the material flow, dynamic and static recrystallization based on macro etchings and visible microstructure under different conditions, e.g. as in the area of high strain rate near the container wall, or in dead zones [1]. To allow an accurate simulation of the extrusion process, punch force and temperature conditions during the tests have been measured and are presented in this paper, too.

Effect of rotational material flow on temperature distribution in friction stir welds

Abstract: A finite element pseudosteady state thermal model takes the mechanical power as input data while distributing the total power input between surface and volume heat sources. A simple model for the material flow around the tool has been developed in order to take heat convection into account based on the shape of the thermomechanically affected zone. The model is assessed for a large number of different welding parameters. Special attention is given to the type of contact at the tool/workpiece interface, i.e. sliding, sticking or both and at the workpiece backing plate interface. The rotational material flow creates asymmetry in the temperature distribution between the two sides of the weld.

A novel approach to fabricate uni-directional and branching slender structures using laser-based direct metal deposition

Abstract: The slender structures are identified by a distinctive morphology and large aspect ratio. Contrary to most of the common products, the fabrication of slender structures is usually based on forming operations. For complex shapes; however, machining may be required. Characteristic of machining for a slender structure; however, is the very small ratio of sustained material with respect to the machined material. This paper describes a novel approach to fabricate slender structures using laser-based direct metal deposition (LBDMD) in a layer-by-layer fashion such that the thickness of each layer is infinitesimally small. The existing additive layer-by-layer deposition is guided by 2 1 2 axis movement and is characterized by intermittent steps. The proposed method, on the contrary, is similar to continuous casting such that the layer thickness can be considered infinitesimally small. The paper develops a framework for fabrication of slender structures using LBDMD. An algorithm based on geometric reasoning is proposed. Simulations based on Volume Of Fluid (VOF) method and a set of experiments are performed to determine and control various key process parameters. Simulations and experiments performed to determine the a relationship between the material flow rate and corresponding body forces that act on the molten pool as the inclination of substrate changes. A range of complex geometries that are based on linear as well as nonlinear spatial trajectories are fabricated. The fabricated geometries offer different inclinations as well as material flow rate; hence, support the applicability of proposed method.

Combining economic and environmental dimensions: Value chain analysis of UK aluminium flows

Abstract: This paper presents the methodology of value chain analysis developed for a study which combined a material flow analysis of the UK aluminium sector with a consideration of the economic dimension of those material flows, in order to shed light on concepts such as resource productivity and dematerialisation of the economy. The methodology is used in this paper to map the current value chain of aluminium flows through the UK; to examine the residual outputs generated by this industry and the value of applying industrial ecology principles; to contrast the environmental impacts of different categories of materials with their values; and to discuss the findings in terms of the global environmental burden, specifically greenhouse gas emissions, of this sector of the economy, with particular attention paid to international trade aspects. It was found that the majority – over three quarters – of total greenhouse gas emissions associated with UK aluminium production and use (defined as domestic production plus net imports), actually come from domestic production. The findings show that value chain analysis is a robust methodology for exploring various aspects of the economy-environment interface, and a useful complement to material flow or life cycle analyses, with a potentially very widespread applicability. The value chain analysis also provides a framework for coherent and integrated responses by industry as well as policy-makers, through its focus on linkages within different stages and actors in a chain and on the potential for systemic efficiencies.

A study on X party material flow: the theory and applications

Abstract: A thorough study of X party material flow (XPMF), its theory and its applications is conducted in this research. The X material flow concept is an extension of the material flow (MF) theory. To further elucidate that XPMF is one type of MF service model with PMF (party, material, flow) fractal structure and the characteristics of XPMF, we develop the three-pyramid synergetic operational model of XPMF. Through the analysis of several cases, we believe that OIR (Objective relational grade, Information sharing grade, and Resource complementary grade) is the set of order parameters that control and determine the formation of XPMF new structure and its degree of being ordered. Therefore it reveals the mechanism of XPMF formation and evolution. We also provide the principles and the methods for XPMF control.

Calculating Method for Influence of Material Flow on Energy Consumption in Steel Manufacturing Process

Abstract: From the viewpoint of systems energy conservation, the influences of material flow on its energy consumption in a steel manufacturing process is an important subject. The quantitative analysis of the relationship between material flow and the energy intensity is useful to save energy in steel industry. Based on the concept of standard material flow diagram, all possible situations of ferric material flow in steel manufacturing process are analyzed. The expressions of the influence of material flow deviated from standard material flow diagram on energy consumption are put forward.

Supply chain coordination : studies on planning and information sharing mechanisms

Abstract: Supply chain information flow significantly influences material flow behaviour To improve supply chain performance, efficient information sharing practices are largely recommended However limited knowledge exists on how companies should choose their supply chain planning approaches and the extent to which information is required Additionally, current literature does not give answers to the question of which situations, or during which supply chain phase, vendor managed inventory, VMI is an efficient replenishment mechanism This research treats the selection of coordination mechanisms, especially supply chain planning and VMI, for manufacturing companies The coordination theory is applied to provide a theoretical basis to consider how companies can jointly manage business processes across the supply chain The research questions are (1) how to select operational coordination mechanisms to match demand and supply in manufacturing companies, and (2), how reach the balance between information flow and material flow by the use of chosen mechanism The thesis consists of six studies, which contain three empirical case studies and three studies where both modeling and case study research approaches are used The studies are reported as six research papers A framework on selecting the supply chain coordination mechanism is developed based on literature findings The framework suggests that the selection should take place according to the match between execution flexibility and information abundance Information sharing should target on providing accurate and good-quality information for the decision-makers Flexible operations should be supported with frequent planning practices that capture information quickly If execution flexibility is low, it needs to be supported with more stable planning This framework is used as a tool to analyse the results from papers Two main reasons for the imbalance between material flow and information flow was identified Frequent plan updates according to demand changes, varying planning prosesses and horizons caused planning nervousness This phenomenon caused bullwhip and large volume changes at the supplier The other reason was lack of planning capability, inadequate information or inability to use shared information Planning nervousness can be reduced with stabilising planning and synchronising information sharing between supply chain players The suitability of VMI was measured with supplier's reaction time The time benefit for the supplier is dependent on the delays caused by order batching It was observed that suppliers' long production planning horizon and infrequent production makes benefiting from VMI more challenging for manufacturers Improving the quality of shared VMI information takes place by offering the right information and improving downstream planning; Toimitusketjun tietovirta vaikuttaa oleellisesti materiaalivirran toimintaan Toimitusketjun tehostamiseksi on esitetty laajaa ja lapi ketjun ulottuvaa kysynta- ja muun operatiivisen tiedon jakamista…

Selective shield/material flow mechanism

Abstract: An apparatus and method for plating a workpiece. The apparatus comprises, generally, an anode, a cathode, and a selective anode shield/material flow assembly. In use, both the anode and the cathode are immersed in a solution, and the cathode is used to support the workpiece. During an electroplating process, the anode and the cathode generate an electric field emanating from the anode towards the cathode, to generate a corresponding current to deposit an electroplating material on the workpiece. The selective shield/material flow assembly is located between the anode and the cathode, and forms a multitude of adjustable openings. These opening have sizes that are adjustable during the electroplating process for selectively and controllably adjusting the amount of electric flux passing through the selective shield/material flow assembly and the distribution of the electroplating material on the workpiece. The selective shield/material flow assembly can also be used with an electroless plating system. At least one selective shield material flow mechanism is used in a selective shield material flow assembly.

Modeling and Analysis of Markovian Continuous Flow Production Systems with a Finite Buffer: A General Methodology and Applications

Abstract: Fluid flow models are used in performance evaluation of production, computer, and telecommunication systems. In order to develop a methodology to analyze general Markovian continuous material flow production systems with a finite buffer, a general single-buffer fluid flow system is modelled as a continuous time, continuous-discrete state space stochastic process and the steady state distribution is determined. Various performance measures such as the production rate and the expected buffer level are determined from the steady-state distributions. The flexibility of this methodology allows analysis of a wide range of models by specifying only the transition rates and the flow rates associated with the discrete states of each stage. Therefore the method is proposed as a tool for performance evaluation of general Markovian continuous flow systems with a finite buffer. The solution methodology is illustrated by analyzing a production system where each machine has multiple up and down states associated with their quality characteristics in detail. Then four different models: a model with multiple unreliable machines in parallel in each stage, a model with a merge-type structure, and a model with phase-type failure and repair-time distributions, and a model with multiple unreliable machines in series in each stage are analyzed by using the same methodology.

The Concept of Closed-loop Supply Chain Integration Through Agents-based System

Abstract: Closed-loop supply chains CLSC) concept is response to a challenge that more and more supply chains meet namely need to include a return flow of materials in they planning and coordination structure. Following paper presents on-going project regarding the application of agent-based systems for supply-chain synchronized production planning including management of raw materials flow as well as flow of returned by customer obsolete products and defected semi-products and products that are refused by quality control within the factory. Authors discuss the main problems that appear by synchronized material flow planning in CLSC. The model for integration of closed-loop supply chain through an agent-based system is proposed.

Material flow determination for radial flexible profile ring rolling

Abstract: Regarding the increasing demand on annular components with complex geometries, a flexible process has been developed at the IBF to profile sleeve shaped rings. Unlike processes using grooved tools, here diverse contours can be realized on the inner surface using one “universal” tool. By extending the tool kinematics and developing an adequate forming strategy the general feasibility of the process has been shown on a bench scaled model ring rolling rig using a wax based model material. Parameters such as ring/tool geometry and roller feed strategy were detected as having an effect on material flow resistance in the rolling and transverse directions. Expressing them by geometric ratios, the material flow distribution could be determined in numerous experiments and quantified by a newly-defined extension coefficient with a certainty of 95%. This achievement enables us to predict the material flow in axial and tangential directions to manufacture complex geometries reproducibly.

Material flow of used PCs in Japan

Abstract: We estimated the material flow of used PCs in Japan, both before and after the enforcement of a household PC recycling system, by minimizing the errors in material flow data. The number of PCs reused in the country and the number exported as secondhand were also estimated.

Material-Guiding Device

Abstract: A material-guiding device in a mower-conditioner surrounds an upper front region of a crop processing rotor and is composed of an upstream-situated portion and a downstream-situated portion. The downstream-situated portion is adjustable relative to the upstream situated portion and is connected thereto such that the adjustment of the upstream-situated portion simultaneously leads to an adjustment of the downstream-situated portion, such that an adjustable angle α present between the two portions is maintained and thus a uniform material flow is enabled.

Impact of Information Technology on Supply Chain Management

Abstract: Information is said to be the glue that holds supply chains together. As a key infrastructure, Web-based technologies continue to have significant impact on supply chain strategies. On the coordination side, the Web provides a virtually free platform for enhancing transparency, eliminating information delays and distortions, and significantly reducing transaction costs. One should note, however, that, although information flow has accelerated considerably, material flow has not gained much speed. This phenomenon makes the coordination of material, information, and cash flows even more crucial for effective supply chain coordination. On the design side, current technology does not yet permit dynamic supply chain design in response to changing business environment. The adoption of Web Services represents a significant step in that direction.