Optical methods in experimental solid mechanics (Q5934756)

These lectures of the International Centre for Mechanical Sciences are devoted to recent developments and achievements in measurement techniques, namely in optical and electro-optical methods. The broad set of the corresponding issues includes two- and three-dimensional linear and nonlinear photoelasticity, moire and grid techniques, interferometric methods (holography, speckle interferometry, shearography), theory of digital image processing and its performance, data-recording, -compression, -processing, and -visualization, and also mathematical and numerical procedures for evaluation of measured data. The book is divided into five lectures. Lecture 1 is devoted to hybrid techniques in experimental solid mechanics, i.e. to the combinations of measurement techniques with numerical methods for data evaluation based on advanced mathematical algorithms, which yield reliable knowledge of the actual state and real reactions of any kind of structures. The principle of hybrid techniques, including interconnections between real events and experimental and mathematical analyses, is applied to problems of nonlinear photoelasticity and photoviscoelasticity. Because the original experimental data do not give final necessary information, numerical procedures with the corresponding discretizations (boundary integral method, boundary element method and finite element method) are carried out for concrete problems. Lecture 2 describes recent developments in three-dimensional photoelasticity connected with new equipment which allows to obtain quickly separated isoclinic and isochromatic patterns and to plot optically isostatics for one-plane sliced model. By using two orthogonal gratings marked upon a plane measure base, it is shown how to determine the algebraic values of principal extensions for large and small strains with a good accuracy and on a whole field which can be of very small dimension. This optical method allows to extend the metrology in extensometry to domains badly adapted to use the electrical strain gage (e.g. joints, cracks, etc.). For dynamic events the local grating interrogation gives both the strains and rigid motions of the measurement base. Lecture 3 is devoted to the application of in-plane grid/moire technique and high sensitivity grating (moire) interferometry to the determination of in-plane displacement and strain fields. An overview of the phase methods of fringe pattern analysis is presented, and the interaction with FEM results referring to various concepts of hybrid experimental-numerical analysis is discussed. The numerous examples include local material constant determination, micromeasurements, residual stress analysis and monitoring of various engineering structures. The modern level of interferometric methods (holography, speckle photography, shearography) is presented in lecture 4. Beginning from fundamental priciples and techniques of these methods, the lecture describes their applications to fracture mechanics, vibrations, nondestructive testing, deformation analysis, etc. A detailed attention is paid to the principles of digital image processing and to the evaluation of measured data. Lecture 5 presents a description of digital processing and evaluation of fringe patterns. Firstly, the lecture discusses the intensity relations in optical metrology and a physical model of image content that contains the relevant disturbances in optical metrology. After that the main techniques for quantitative phase reconstruction are presented together with the commonly used image processing methods. Then, the reader can find an overview of modern approaches to automatic flaw detection based on knowledge-assisted and neural network techniques. Finally, modern software tools for digital processing of fringe patterns are presented. In total, this course of lectures successfully describes the modern level and technical possibilities of optical methods in experimental solid mechanics. The book can be very useful to students and engineers dealing with the corresponding areas.