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Publications:Books:Handbook:Preface
Preface
In the past few years, the analysis of metal forming has advanced greatly. Progress in the application of limit analysis (upper- and lower-bound solutions) to metal-forming processes is documented in two other books by this author entitled Metal Forming: Processes and Analysis (Krieger, 1979 and McGraw-Hill, 1968) and Metal Forming: The Application of Limit Analysis (Marcel Dekker, 1980). The first book provides detailed derivations of solutions to selected metal-forming processes, and the second focuses on the technique of limit analysis itself.
The vast advance of knowledge based on analysis has helped the ongoing transition in the application of metal-forming processes from an art to a science. However, the mathematical approach in the two books mentioned above left a gap that required further exposition with regard to the needs of (1) the practicing engineer and (2) the student of engineering with more interest in application of existing know-how, rather than how it was obtained or how it can lead to new horizons. Thus, a need for the present book, which is descriptive, has arisen. In this book a collection of metal-forming processes is presented. The characteristics of each process are viewed and insight gained by studying the modes of deformation in the workpiece and the external forces. From there the toot design, its geometrical parameters, and their effects on processing are discussed. The book covers only lightly the design of the machines and their operation.
The bulk of the material is based on studies by limit analysis, and Chapter I therefore covers the basic concepts at the level advisable for the understanding of the derivations and fundamentals on which the rest of the material is based. The manner in which the basic concepts are covered has evolved gradually. The focus on the process and disciplines other than limit analysis is also presented.
The distinct topics of each chapter cover specifically a class of processing methods (rolling, extrusion, forging), a phenomenon (friction, pressure-induced ductility), or a concept (soft tooling, metalworking under pressure). The book is intended to provide insight and understanding of metal forming through the introduction of most common and new processes and of related phenomena and concepts. The book is not an encyclopedia of all present-day equipment available. It is, however, intended, through emphasis on mastery of the principles, to make the engineer capable of understanding processes not covered in the book and to learn new developments during his career. Thus, on many occasions the book covers processes that are presently in their laboratory or conception stages, and some of these may never be used in production.
The treatment in this book is quantitative. Flow patterns are described through velocity fields given by mathematical expressions. Forces are given by explicit mathematical expressions providing quantitatively the dependence of forming forces on the independent parameters of the processes, including material properties, die geometry, reductions, and so on. Interpretation of the mathematical expressions is provided graphically and verbally. Lengthy mathematical derivations of the results presented in this book are omitted. Only minimal presentations of the simplest derivations and of solutions are provided. For more complex exercises the reader should refer to the derivations presented in the two books mentioned above and the numerous papers cited in them.
The processes themselves constitute the focus of this book. With the aid of the mathematical expressions, the graphs, and the exposure to the basic concepts, insight is provided into the processes and how to control them.
The majority of the explicit mathematical relations, and their graphical interpretations in this book are handled in a dimensionless form, which applies equally well in any unit system. Thus the transition to the SI unit system has little effect on the treatment. However, when experimental data are presented, discussed, or compared with analytical expressions, the unit system matters. In general, in this book data from referenced literature are presented in the original units. Sometimes an extra column in the new unit system is added to a table.
A word about the new (SI) system and the old (metric) system will be in order here. In the conventional metric system a gram of mass is pulled to earth by one gram force, and thus it weighs one gram. For engineering problems, and therefore for engineers, the measurement of force in grams (and kilograms) makes sense and is attractive.
In the newly adopted SI system force is measured in newtons. The relation between the units in the two systems is given by (number of newtons) º g ´ (number of kg force), where g, the gravitational acceleration, measures 9.81 m/sec2. In the days before the pocket calculator it was permissible to approximate g by the factor 10. Thus, one kilogram mass, weighing one kilogram in the metric system, weighs about 10 newtons in the new SI system. In this book the old metric system is accepted. When it is used, the reader can easily translate kilograms of force (denoted kg) to newtons by multiplying the metric quantity by 10 (or 9.81, to be precise).
Lectures on specific topics of this text have been recorded on magnetic tape and synchronized with 35-mm slides. Each of these audiovisual programs not only constitutes a part of the classroom presentation for a course in metal forming, but is also broad enough in its coverage to be of potential interest to the industrial metal-forming community. Several movies are available, together with displays and transparent plastic models for process simulation. Also available is a booklet with descriptions of proposed laboratory experiments. Laboratory sessions include actual tests on metal-forming equipment with process-simulation tools and the running of computer simulation programs. A description of the entire package is available on request from the author. An answer booklet to the Problems to assist teaching of this course is available from the author.
B. AVITZUR
Bethlehem, Pennsylvania
March 1983[ top ]
Last Modified:
Friday, 19-Dec-1997 21:12:18 EST
Copyright 1997 Betzalel Avitzur. All rights reserved.
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