Alliages A Memoire De Forme

Les alliages à mémoire de forme sont des matériaux uniques qui ont la propriété de se souvenir des traitements thermomécaniques subis (traction, torsion, flexion, etc.). Ils sont très utilisés dans l'industrie biomédicale, l'aéronautique ou le nucléaire. Cet ouvrage traite de leur compréhension physique et mécanique, et de leur utilisation, en se concentrant principalement sur la nature de la transformation martensitique, expliquée à travers les théorèmes de Ball et James. Les modèles macroscopiques à variables internes donnent les clés pour le calcul des structures en alliage à mémoire de forme, particulièrement utile pour l’utilisation industrielle de ces matériaux. Professeur à l’Ecole nationale supérieure de mécanique et des microtechniques de Besançon, Christian Lexcellent mène des recherches depuis plus de 20 ans sur les alliages à mémoire de forme. Ses enseignements portent sur le comportement linéaire et non-linéaire des matériaux.

The book is mainly devoted to the thermomechanical behavior of materials during solid-solid phase transformations. The physical mechanisms including diffusion, martensitic transformation and plasticity are described from material science point of view. The global behaviour is deduced from methods of classical as well as irreversible thermodynamics and continuum and micro mechanics. Mainly metals, both non ferrous and ferrous alloys but also geological problems are dealt with. Special attention is given to transformation induced plasticity and shape memory alloys. Three chapters are concerned with practical applications (heat treatment, smart structures, residual stresses).

This book investigates collisions occurring in the motion of solids, in the motion of fluids but also in the motion of pedestrians in crowds. The duration of these presented collisions is short compared to the whole duration of the motion: they are assumed instantaneous. The innovative concept demonstrated in this book is that a system made of two solids, is deformable because their relative position changes. The definition of the velocities of deformation of the system introduced in the classical developments of mechanics, the principle of the virtual work and the laws of thermodynamics, allows a large range of applications such as crowd motions, debris flow motions, and shape memory alloys motions. The set of the applications is even larger: social sciences and mechanics are unified to predict the motion of crowds with application to transport management and to evacuation of theaters management.

This book offers an essential introduction to the linear and non-linear behavior of solid materials, and to the concepts of deformation, displacement and stress, within the context of continuum mechanics and thermodynamics. To illustrate the fundamental principles, the book starts with an overview of solid mechanics, experimental methods, classes of material behaviors, and the thermodynamic modeling framework. It then explores linear elastic behavior, thermoelasticity, plasticity, viscoplasticity, fracture mechanics and damage behavior. The last part of the book is devoted to conventional and magnetic shape memory alloys, which may be used as actuators or sensors in adaptive structures. Given its range of coverage, the book will be especially valuable for students of engineering courses in Mechanics. Further, it includes a wealth of examples and exercises, making it accessible to the widest possible audience.

The aim of this book is to understand and describe the martensitic phase transformation and the process of martensite platelet reorientation. These two key elements enable the author to introduce the main features associated with the behavior of shape-memory alloys (SMAs), i.e. the one-way shape-memory effect, pseudo-elasticity, training and recovery. Attention is paid in particular to the thermodynamical frame for solid materials modeling at the macroscopic scale and its applications, as well as to the particular use of such alloys – the simplified calculations for the bending of bars and their torsion. Other chapters are devoted to key topics such as the use of the “crystallographical theory of martensite” for SMA modeling, phenomenological and statistical investigations of SMAs, magneto-thermo-mechanical behavior of magnetic SMAs and the fracture mechanics of SMAs. Case studies are provided on the dimensioning of SMA elements offering the reader an additional useful framework on the subject. Contents 1. Some General Points about SMAs. 2. The World of Shape-memory Alloys. 3. Martensitic Transformation. 4. Thermodynamic Framework for the Modeling of Solid Materials. 5. Use of the “CTM” to Model SMAs. 6. Phenomenological and Statistical Approaches for SMAs. 7. Macroscopic Models with Internal Variables. 8. Design of SMA Elements: Case Studies. 9. Behavior of Magnetic SMAs. 10. Fracture Mechanics of SMAs. 11. General Conclusion. Appendix 1. Intrinsic Properties of Rotation Matrices. Appendix 2. “Twinning Equation” Demonstration. Appendix 3. Calculation of the Parameters a, n and Q from the “Twinning” Equation. Appendix 4. “Twinned” Austenite/Martensite Equation. About the Authors Christian Lexcellent is Emeritus Professor at the École National Supérieure de Mécanique et des Microtechniques de Besançon and a researcher in the Department of Applied Mechanics at FEMTO-ST in France. He is a specialist in the mechanics of materials and phase transition and has taught in the subjects of mechanics of continuum media and shape memory alloys. He is also a member of the International Committee of ESOMAT.