Continuous materials processing, as contrasted with batch processing, is discussed. There is growing interest in continuous processes because of higher production rates and lower costs. A wide range of processes can be considered for continuous processing. These include hot and cold rolling, extrusion, wire and fiber drawing, heat treatment of moving materials, and deposition on continuously moving surfaces.
The problem is time dependent at the start of the process, but generally approaches steady-state conditions as time elapses. Both situations are of practical interest. Fluctuations and instabilities can also lead to time dependence. Of particular interest is the thermal field in the moving material, since the resulting thermal stress and microstructure are determined by the temperature distribution. The temperature rise or decay with distance is also critical in designing the system to maintain temperatures above certain values, such as the recrystallization temperature for hot rolling.
Though a convective heat transfer coefficient, obtained from empirical data and correlations, may be employed at the surface, the problem is actually a conjugate one and both the fluid flow and the thermal field in the solid have to be considered. Though boundary-layer assumptions are valid in some cases, solution of the full elliptic equations is generally needed for a realistic simulation.
Buoyancy effects are important in many circumstances and an additional forced flow, in an extensive environment or in a channel, may be employed to enhance the heat transfer. Experiments are used to validate the analytical and numerical models, to provide physical insight into the basic mechanisms, and to provide realistic and practical operating conditions.
Materials Processing and Manufacturing | Materials Science and Engineering
The basic formulation, solution strategies, and typical results are presented on this materials processing technique. The relevance of such results in the operation, control, design, and optimization of practical continuous manufacturing processes is discussed. The processing of polymers, which include a wide range of materials such as plastics, food, rubber, resins, silicones, and biopolymers, is discussed.
Because of the extensive use of these materials, many important processing techniques are available and are widely used to manufacture products for many different applications. Substantial literature exists on the fundamental aspects involved in polymer processing and on the design and operation of the relevant systems. The focus here is on the three major processes of extrusion, injection molding, and thermoforming. Extrusion is considered in significant detail in order to discuss the characteristics of the materials involved, major concerns, requirements and constraints, process modeling, and typical simulation and experimental results that may be used for the control, design, and optimization of the processes.
Extrusion also serves as the feeding mechanism in several injection molding systems. The discussions on phase change, transport phenomena in polymers, and channel flow can also be applied to injection molding processes.
Materials Processing and Manufacturing
Thermoforming is a very different process, since it depends on forming and shaping after adequately heating the plastic beyond the glass transition temperature. A few examples are given to illustrate this process as well as other similar ones. The discussion is focused on the chemical vapor deposition process for the fabrication of thin films for materials such as silicon, titanium nitride, and gallium nitride. The different types of reactors, modeling of the flow, heat and mass transfer, and chemical reactions are considered in detail.
Numerical and experimental results are presented for a variety of conditions and geometries. Of particular interest are the deposition rate and the quality of the deposited film. The chemistry is a critical component in these processes and, though the chemical pathways, chemical kinetics, and properties are known to a fair degree of accuracy for some important materials, the information available for other materials is often quite limited.
The modeling of the transport processes without the chemical reactions is relatively straightforward, but the inclusion of chemical reactions generally makes the simulation much more complicated and difficult. Experimental data are available for materials like silicon due to their extensive use, but the data for the wide variety of materials of current and future interest are somewhat limited. Though the focus is on CVD systems, similar considerations arise in other fabrication techniques, such as flame synthesis of various materials. The basic considerations of quality versus production rate are common to all these processes.
The link between the product characteristics and the operating conditions is an important one and the needed future effort is discussed.
The approaches presented here may be extended, with suitable modifications, to other processes and applications. This chapter discusses the fabrication of optical fibers, focusing on the drawing, cooling, and coating of fibers.
- Book Description.
- Advanced Materials Processing and Manufacturing!
- Importance of the three-dimensional modeling in materials processing?
The basic transport mechanisms that arise are discussed, along with results from analytical, numerical, and experimental studies. Starting with the fabrication of the preform, this chapter discusses the thermal transport in the draw furnace and the flow in silica glass. Of particular interest are the neck-down profile, defects generated during the process, feasibility of the process, and possible optimization of the process. The consideration is also extended to hollow, microstructured, and doped fibers that are of interest in different applications.
Numerical solution: Some finite difference methods. Numerical solution: Some finite element methods. Example: Glass refining. Example: Fiber spinning. Example: Alloy solidification. Example: Microwave heating of ceramics. Example: Combustion synthesis of refractory materials. Example: Binder removal from shaped powder compacts.
Example: Flow of a solid-liquid suspension.
Back Matter Pages About this book Introduction This is a book about mathematical modelling. It focuses on the modelling of the preparation of materials. Materials are important, of course, in an economic sense: the "goods" of goods-and-services are made of materials. This provides a strong incentive to produce good materials and to improve existing materials.
AB - In this article, a constitutive model for quench-hardenable boron steel is presented. Plasticity and fracture modeling of quench-hardenable boron steel with tailored properties Tom Eller, L Greve, M. Abstract In this article, a constitutive model for quench-hardenable boron steel is presented. Fingerprint Boron. Constitutive models. Bending tests. Strain rate.