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Über dieses Buch

It is the objective of the series IIMaterials Research and Engineeringll to publish information on technical facts and pro­ cesses together with specific scientific models and theories. Fundamental considerations assist in the recognition of the origin of properties and the roots of processes. By providing a higher level of understanding, such considerations form the basis for further improving the quality of both traditional and future engineering materials, as well as the efficiency of industrial operations. In a more general sense, theory helps to integrate facts into a framework which ties relations between physical equilibria and mechanisms on the one hand, product development and econo­ mical competition on the other. Aspects of environmental compati­ bili ty, conservation of resources and of socio-cul tural inter­ action form the final horizon - a subject treated in the first ll volume of this series, IIMaterials in World Perspective . The four authors of the present book endeavor to present a comprehensive picture of process modelling in the important field of metal forming and thermomechanical treatment. The reader will be introduced to the rapidly-growing new field of application of computer-aided numerical methods to the quanti­ tative simulation of complex technical processes. Extensive use is made of the state of scientific knowledge related to materials behavior under mechanical stress and thermal treat­ ment.

Inhaltsverzeichnis

Frontmatter

1. Preface

Abstract
The expression “process model” as used here refers to a mathematical model which has been developed to a level at which it can quantiatively describe the essential characteristics of a process and which, when implemented as a computer program, permits the stepwise simulation of the process. The practical aim of a computer process model is always the generation of quantitative statements concerning the process in question, whereby these should be faster, cheaper or more extensive than can be obtained by laboratory experiments or tests during actual fabrication.
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

2. Mathematical Modelling

Abstract
At the very heart of metal forming analysis is the theory of plasticity. Initially proposed last century by Tresca and Mohr, it reached a stabilized form in the twenties as a result of work done by von Mises and Hencky. In the early sixties it was completed for infinitesimal analysis [2.1]. A brief description of this theory follows in section 2.2. The theory for large deformations is still being developed today.
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

3. Physical Modelling

Abstract
Modelling laws permit the transfer of information obtained from model tests to the full-scale component, which may differ from the model in terms of size, material, physical characteristics or boundary conditions. For a long time, model tests were a decisive aid to the engineer when designing complex structures and machines, particularly for aircraft and ships. The development of modern computer technology and computer simulation has reduced the importance of the model technique.
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

4. Modelling of Forging

Abstract
The forging operation can be seen as a system with a large number of interacting variables. Furthermore, these variables can have a rather large field of values which they can span when the die and workpiece temperatures and resulting contact times for conventional forging, hot-die forging and isothermal forging are rather different. The selection of the optimum conditions during isothermal forging is not simple. In conventional and hot-die forging, the problem is even more complex due to the heat transfer phenomena between billet and die.
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

5. Modelling of Rolling

Abstract
Warm or cold roll forming is a deformation process used for economic production of profiles, not only for structural purposes (e.g. angles, T-bars, channel sections etc.) but also for precision work, such as for turbine blades. For simple standard profiles, there are guidelines available and experimental findings for roll pass design and for working out the roll pass schedule from the starting pass to the finished section [5.1]. Flat rolling, too, has also been the subject of detailed investigation [5.2]. However, for designing complicated special profiles, the rolling tools are, as a rule, designed empirically. There are two reasons for this:
1.
Roll forming is an experience-based technology, whereby improvements and developments have come about principally through a pragmatic approach by trial-and-error methods.
 
2.
Although numerous publications deal with lateral spread of the material within the roll gap, pre-determination of spread behavior during roll forming gives rise to considerable problems and is possible to a sufficient degree of accuracy only for special cases by the application of lateral spread formulae [5.3–5.6] or calculations on the basis of plasticity theory [5.7–5.9]. As lateral spread is influenced by many parameters [5.10] — geometry, friction, temperature, microstructure, yield stress — for new materials, there is no alternative but to determine lateral spread by experiment.
 
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

6. Modelling of Drawing

Abstract
In an attempt to reduce costs, increasing attention is being paid to the drawing of section rods from round bar in a minimum possible number of steps. However, a direct theoretical approach to this problem has been only partially attempted in the past [6.1] due to the difficulty in applying simple techniques to represent the deformation pattern even in the relatively simple section analyzed in this chapter. The analysis of the deformation process from a round bar to a square rod with different corner radii was chosen as a first step towards the study of more complicated shape drawing [6.2, 6.3].
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

7. Modelling of Thermomechanical Treatment

Abstract
According to the traditional meaning, thermomechanical treatments are combinations of heat treatments and plastic deformations which may or may not be simultaneous and which aim at controlling material properties that could not be obtained otherwise. To a certain extent, the deformation aspects of this concept have been dealt with in Chapter 4.3.4, when deformation and heat transfer analyses were made in parallel. It was shown then how a deformation can be modelled at any temperature with a variety of heat transfer boundary conditions. That chapter therefore covered the mechanical aspects during a thermomechanical treatment.
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

8. Outlook

Abstract
The examples in this book show that process models, in conjunction with the present generation of computers, can already supply solutions to many problems in manufacturing technology. In some cases, this can be achieved more economically than with tests in the laboratory or in production facilities. With process models, localized predictions can be made of temperatures, stresses and deformations in the workpiece or tool, which cannot be achieved with the most modern measuring techniques.
Claudio R. Böer, Nuno M. R. S. Rebelo, Hans A. B. Rydstad, Günther Schröder

Backmatter

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