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Superplasticity is the ability of polycrystalline materials under certain conditions to exhibit extreme tensile elongation in a nearly homogeneous/isotropic manner. Historically, this phenomenon was discovered and systematically studied by metallurgists and physicists. They, along with practising engineers, used materials in the superplastic state for materials forming applications. Metallurgists concluded that they had the necessary information on superplasticity and so theoretical studies focussed mostly on understanding the physical and metallurgi­ cal properties of superplastic materials. Practical applications, in contrast, were led by empirical approaches, rules of thumb and creative design. It has become clear that mathematical models of superplastic deformation as well as analyses for metal working processes that exploit the superplastic state are not adequate. A systematic approach based on the methods of mechanics of solids is likely to prove useful in improving the situation. The present book aims at the following. 1. Outline briefly the techniques of mechanics of solids, particularly as it applies to strain rate sensitive materials. 2. Assess the present level of investigations on the mechanical behaviour of superplastics. 3. Formulate the main issues and challenges in mechanics ofsuperplasticity. 4. Analyse the mathematical models/constitutive equations for superplastic flow from the viewpoint of mechanics. 5. Review the models of superplastic metal working processes. 6. Indicate with examples new results that may be obtained using the methods of mechanics of solids.

Inhaltsverzeichnis

Frontmatter

Introduction

Abstract
In the last three decades, many reviews on superplasticity have appeared. Some of these discuss all the main features of the phenomenon and its applications (see, e.g., monographs [1–7], reviews [8–15] and proceedings [16–23]), while others consider specific aspects, e.g., applications of superplasticity, development of new technological processes of metal working, mathematical modelling of the technological processes, properties of some superplastic materials, micromechanisms of deformation, etc. [24–31]. A recent book [6] as well as the five earlier publications [1–5] contain a comprehensive description of the metallurgical aspects of superplasticity and so there is no need to restate them in detail in the present volume. Reports on the various aspects of finite element modelling have also been published recently (see, e.g., [29–31]). Therefore, these aspects as well are not considered here in detail.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

1. Phenomenology of Superplastic Flow

Abstract
In this chapter, the phenomenology of superplastic flow is discussed. Full expositions are available in [1–6]. Other reviews consider this aspect to varying extent [7–15]. Attention is focussed here on recent results and comments are offered on the present level of understanding.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

2. Mechanics of Solids

Abstract
There is no unique definition for ‘mechanics’. Many regard it as an elementary branch of physics dealing with the motion and equilibrium of rigid bodies (the so-called classical dynamics) that forms the basis of many engineering disciplines. But, the term is also included in some highly specialised subjects, e.g., fluid mechanics, statistical mechanics, quantum mechanics. In this book, mechanics of solids is used to describe the macrobehaviour of superplastics. Hence, in this book unless otherwise stated ‘mechanics’ stands for ‘mechanics of solids’.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

3. Constitutive Equations for Superplastics

Abstract
Most of the constitutive equations (CE) for superplastics found in the literature [284–294] are written in scalar form in terms of infinitesimally small strains. A review of such scalar CEs is made first. Some problems associated with generalising such scalar CEs for non-uniform stress-strain state [295–300] are discussed next. Finally, attention is paid to the interpretation of experimental results obtained under conditions of a non-uniform stress-strain state (e.g., torsion, superplastic forming of thin sheet materials [301–303]). An examination of the physical validity/relevance of the models is beyond the scope of the present book.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

4. Boundary Value Problems in Theory of Superplastic Metalworking

Abstract
Boundary Value Problems (BPs) in mechanics of superplasticity are not well developed. Inadequacies in the development of the constitutive equations for superplastics are examined below using simple examples.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

5. Mathematical Modelling of Superplastic Metalworking Processes

Abstract
Superplastic metal working processes have been modelled mostly based on semiempirical approaches and using simplifying assumptions [461–466]. In this chapter, such models known in the literature are reviewed. Attention is focussed on presenting the ideas from the viewpoint of mechanics of solids. The merits and limitations of these analyses are discussed with a view to improving them in the future. A comprehensive review of the industrial applications of superplasticity is beyond the scope of this book.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

6. Problems and Perspectives

Abstract
In this chapter, some problems of and perspectives on investigations in superplasticity are presented. As elsewhere in the book, only aspects of phenomenology and mechanics are considered.
K. A. Padmanabhan, R. A. Vasin, F. U. Enikeev

Backmatter

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