Superplastic Flow

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.

Outlines briefly the techniques of mechanics of solids Assesses the present level of investigations on the mechani- cal behaviour of superplastics Formulates the main issues and challenges in the mechanics of superplasticity Analyses the constitutive equations for superplastic flow Reviews the models of superplastic metal working processes Dndicates with examples possible new results Includes supplementary material: sn.pub/extras

Texte du rabat
The present book aims at the following: - To outline briefly the techniques of mechanics of solids, particularly as it applies to strain rate sensitive materials, - to assess the present level of investigations on the mechanical behaviour of superplastics, - to formulate the main issues and challenges in mechanics of superplasticity, - to analyse the mathematical models/constitutive equations for superplastic flow from the viewpoint of mechanics, - to review the models of superplastic metal working processes, - to indicate with examples possible new results that can be obtained using the methods of mechanics of solids. It is intended for a variety of readers who may be interested in the phenomenon of superplasticity for different reasons: materials scientists and physicists working in educational institutions and R&D units, those who wish to work on the applications of superplasticity, engineers in industry, students at senior undergraduate and postgraduate levels and those who wish to understand the phenomenology and mechanics of superplasticity without involvement in actual research. A reader who has exposure to standard differential and integral calculus and elementary tensor calculus at a level taught to senior undergraduate students at a technical university should have no difficulty in following the treatments. The analytical procedures are explained in an Appendix with simple examples.

Contenu
1 Phenomenology of Superplastic Flow.- 1.1 Historical.- 1.2 Mechanical Behaviour of Superplastics.- 1.3 Strain Rate Sensitivity of Superplastic Flow.- 1.4 Superplasticity from the Point of View of Mechanics.- 2 Mechanics of Solids.- 2.1 The Subject.- 2.2. Basic Concepts.- 2.3 General Laws and Boundary Value Problems.- 2.4 Mathematical Models of Materials.- 2.5 Experiments in Mechanics.- 3 Constitutive Equations for Superplastics.- 3.1 Basic Requirements of Constitutive Equations.- 3.2 Phenomenological Constitutive Equations.- 3.3 Physical Constitutive Equations.- 3.4 Construction of Constitutive Equations.- 3.5. Constitutive Equations in Tensor Form.- 3.6 Material Constants from Technological Tests.- 4 Boundary Value Problems in Theory of Superplastic Metalworking.- 4.1 General Formulation of the Boundary Value Problem for Metalworking Processes.- 4.2 Model Boundary Value Problems in Mechanics of Superplasticity.- 4.3 Numerical Solving of Boundary Value Problems in Superplasticity.- 5 Mathematical Modelling of Superplastic Metalworking Processes.- 5.1 Modelling of Superplastic Bulk Forming Processes.- 5.2 Modelling of Sheet Metal Processes.- 5.3 Deformation Processing of Materials.- 6 Problems and Perspectives.- 6.1. Influence of Strain History on Evolution of Structure.- 6.2. Constitutive Equations Including Structural Parameters.- 6.3. The Concept of Database 'TMTStructureProperties'.- 6.4. Challenges in Mechanics of Superplasticity.- Appendix A: Finite Strain Kinematics of Solids.- A.1 Basic Concepts.- A.2 Theory of Deformations.- A.2.1 Strain Tensors.- A.2.2 Geometrical Sense of Strain Tensor Components.- A.2.3 Method of Determining the Principal Components of a Strain Tensor.- A.2.4 Volumetric and Deviatoric Parts of Strain Tensors.- A.3 Strain RateTensor.- A.3.1 Covariant Components of Strain Tensor.- A.3.2 Distortion and Spin Tensors.- A.3.3 Strain Rate Tensor Invariants.- A.3.4 Volumetric and Deviatoric Parts of the Strain Rate Tensor.- A.3.5 On Some Scalar Characteristics of a Deformed State.- Appendix B: Kinematics of Some Simple Deformation Modes.- B.1 Tension/Compression of a Cylindrical Rod.- B.2 Simple Shear.- B.3 Pure Shear.- B.4 Bulging of a Sphere.- B.5 Finite Strain Kinematics under Combined Loading of a Cylindrical Rod by Axial Force and Torque.- Appendix C: On Dimensional Analysis.- C.1 Basic Concepts.- C.2 Viscous Flow.- C.3 Non-Newtonian Flow.- C.4 Superplastic Flow.- C.5 Dimensionless Parameters for the Boundary Value Problem of Superplasticity.- C.6 Physical Modelling of Superplastics.- Appendix D: Group Properties of Thermoviscoplasticity.- D.1 About Single-Parameter Groups of Transforms.- D.2 Applications of Group Methods in Superplasticity.- References.