Pericles S. Theocaris – författare

Moiré Fringes in Strain Analysis provides a comprehensive description of the entire spectrum of techniques and methods using the moiré fringe phenomenon for the measurement of strains in engineering structures and in deformed bodies. This book presents several examples of applications of each technique to particular metrological problems. Organized into 12 chapters, this book begins with an overview of the interference fringes between two beams of monochromatic light. This text then discusses the theory of moiré patterns developed by various types of gratings based on the indicial representation method. Other chapters consider the experimental and theoretical investigation of the properties of moiré fringes that was primarily confined to moiré fringes formed by the interference of two-line gratings. This book discusses as well the major requisite for the application of moiré methods in the field of strain analysis. The final chapter deals with the advantages of the moiré methods. This book is a valuable resource for engineers, students and researchers.

Moiré Fringes in Strain Analysis provides a comprehensive coverage of the measurement of strains in deformed bodies and engineering structures. The title details the methods and techniques in strain analysis using the moiré fringe phenomenon. The text first covers the general theory, and then proceeds to tackling the moiré patterns. Next the selection deals with the applications of line gratings to two-dimensional strain measurement. The text also talks about surface topology by moiré patterns, along with the applications of moiré methods to dynamic problems and curved surfaces. The ninth chapter discusses moiré extensometers, while the tenth chapter tackles the precision and influence of grating defects. The remaining chapters detail the technological information on reproduction techniques of gratings and the evaluation of moiré methods. The book will be of great use to students, practitioners, and researchers of materials engineering and pure and applied mathematics.

Photoelasticity as an experimental method for analyzing stress fields in mechanics was developed in the early thirties by the pioneering works of Mesnager in France and Coker and Filon in England. Almost concurrently, Föppl, Mesmer, and Oppel in Germany contributed significantly to what turned out to be an amazing development. Indeed, in the fifties and sixties a tremendous number of scientific papers and monographs appeared, all over the world, dealing with various aspects of the method and its applications in experimental stress analysis. All of these contributions were based on the so-called Neumann-Maxwell stress-opticallaw; they were developed by means of the classical methods of vector analysis and analytic geometry, using the conventionallight-vector concept. This way of treating problems of mechanics by photoelasticity indicated many shortcomings and drawbacks of this classical method, especially when three-dimensional problems of elasticity had to be treated and when complicated load and geometry situations existed. Meanwhile, the idea of using the Poincare sphere for representing any polarization profile in photoelastic applications was introduced by Robert in France and Aben in the USSR, in order to deal with problems of polarization oflight passing through aseries of optical elements (retarders andjor rotators). Although the Poincare-sphere presentation of any polarization profile con­ stitutes a powerful and elegant method, it exhibits the difficulty of requiring manipulations in three-dimensional space, on the surface of the unit sphere. However, other graphical methods have been developed to bypass this difficulty.

The increasing use of advanced composite materials in modem structures of high performance calls for a detailed knowledge of their properties. On the other hand, these materials possessing intense anisotropy, and in some cases non homogeneity, require complicated theories based on homogeneous anisotropic elasticity. Typically, such materials either involve fiber-reinforced composites, which are stacked in layers and form laminates, or particulate composites, containing a second phase in powder form. However, each case must be separately analyzed in terms of the particular characteristics of the materials involved and the process of preparation of the com­ posite systems. Composite materials consisting of more than one destinct phase are in general use in modem industrial applications. Machine parts, structural components and others may be manufactured from such materials. Epoxy resins are suitable matrices for this class of materials. This is due not only to their general-properties such as linear mechanical behavior, transparency, etc., but also to the possibility of modifying their mechanical and optical properties in a very wide range by using suitable modifiers. Their rheological behavior, as well as their dynamic properties have been extensively investigated.

The increasing use of advanced composite materials in modem structures of high performance calls for a detailed knowledge of their properties. On the other hand, these materials possessing intense anisotropy, and in some cases non homogeneity, require complicated theories based on homogeneous anisotropic elasticity. Typically, such materials either involve fiber-reinforced composites, which are stacked in layers and form laminates, or particulate composites, containing a second phase in powder form. However, each case must be separately analyzed in terms of the particular characteristics of the materials involved and the process of preparation of the com­ posite systems. Composite materials consisting of more than one destinct phase are in general use in modem industrial applications. Machine parts, structural components and others may be manufactured from such materials. Epoxy resins are suitable matrices for this class of materials. This is due not only to their general-properties such as linear mechanical behavior, transparency, etc., but also to the possibility of modifying their mechanical and optical properties in a very wide range by using suitable modifiers. Their rheological behavior, as well as their dynamic properties have been extensively investigated.

Photoelasticity as an experimental method for analyzing stress fields in mechanics was developed in the early thirties by the pioneering works of Mesnager in France and Coker and Filon in England. Almost concurrently, Föppl, Mesmer, and Oppel in Germany contributed significantly to what turned out to be an amazing development. Indeed, in the fifties and sixties a tremendous number of scientific papers and monographs appeared, all over the world, dealing with various aspects of the method and its applications in experimental stress analysis. All of these contributions were based on the so-called Neumann-Maxwell stress-opticallaw; they were developed by means of the classical methods of vector analysis and analytic geometry, using the conventionallight-vector concept. This way of treating problems of mechanics by photoelasticity indicated many shortcomings and drawbacks of this classical method, especially when three-dimensional problems of elasticity had to be treated and when complicated load and geometry situations existed. Meanwhile, the idea of using the Poincare sphere for representing any polarization profile in photoelastic applications was introduced by Robert in France and Aben in the USSR, in order to deal with problems of polarization oflight passing through aseries of optical elements (retarders andjor rotators). Although the Poincare-sphere presentation of any polarization profile con­ stitutes a powerful and elegant method, it exhibits the difficulty of requiring manipulations in three-dimensional space, on the surface of the unit sphere. However, other graphical methods have been developed to bypass this difficulty.

Proceedings of First USA-Greece Symposium on Mixed Mode Crack Propagation, Athens, Greece, 18-22 August, 1980

When we first approached some colleagues allover the world to sound them about a volume dedicated to Professor John Xanthakis on the occasion of completing twenty-five years of scientific activities as fellow of the National Academy of Athens, any possible doubts as to the feasibility of the project were quickly dispelled by their warm and encouraging response. In a short time 50 authors from 15 countries, coming from a wide range of Professor Xanthakis'' immediate colleagues, pupils and friends joined to produce the 36 contributions included in this volume. Some of those who where originally approached found themselves un­ able to contribute, because of the time-limit necessarily imposed. Happi­ ly, they were only few in number, and we should like to record our grat­ itude to them for their good wishes for the success of the venture. Their warm words were among the many sources of inspiring encouragement extended to us.