CISM COURSES AND LECTURES

Transcription

1 CISM COURSES AND LECTURES Series Editors: The Rectors of CISM Sandor Kaliszky- Budapest Mahir Sayir - Zurich Wilhelm Schneider- Wien The Secretary General of CISM Giovanni Bianchi - Milan Executive Editor Carlo Tasso - Udine The series presents lecture notes, monographs, edited works and proceedings in the field of Mechanics, Engineering, Computer Science and Applied Mathematics. Purpose of the series is to make known in the international scientific and technical community resuits obtained in some of the activities organized by CISM, the International Centre for Mechanical Sciences.

2 INTERNATIONAL CENTRE FOR MECHANICAL SCIENCES COURSES AND LECTURES - No. 403 OPTICAL METHODS IN EXPERIMENTAL SOLID MECHANICS EDITED BY KARL-HANS LAERMANN BERGISCHE UNIVERSITY OF WUPPERTAL ~ Springer-Verlag Wien GmbH

3 This volume contains 266 illustrations This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction hy photocopying machine or similar means. and storage in data hanks hy Springer-Verlag Wien Originally published by Springer-Verlag Wien New York in 2000 SPIN In order.to make this volume available as economically and as rapidly as possible the authors' typescripts have been reproduced in their original forms. This method unfortunately has its typographical limitations hut it is hoped that they in no way distract the reader. ISBN ISBN (ebook) DOI /

4 PREFACE Recent developments and achievements in measurement techniques especially in optical and electro-optical methods like holography, shearography, speckle interferometry, grid-methods, modern modification of photoelasticity and photoviscoelasticity have opened new fields of applying experimental analysis in solid mechanics, in research as well as in industrial practice. Combined with computer techniques in digital image processing, data recording and data evaluation complex measuring systems can be realised nowadays with the possibility of far-reaching automation of the entire analysing processes. The sensitivity and the high resolving power of recording equipment requires thorough investigation of any effects on the precision and reliability of the measurements. Therefore it is necessary, to deal with the physics and the theories of the measurement methods in order to interpret the observed phenomena correctly. Furthermore proper algorithms must be available to evaluate the measured data to get the finally wanted infonnation, which generally do not coincide with the quantities taken from the measurements originally. This fact requires complementary scientific considerations of the theories concerning the problems to be analysed. At least the combination of experimental and mathematical/numerical procedures for evaluation and interpretation, known as "hybrid technique", demands additional contemplation. The lectures cover i. the theory and the physics of advanced optical measuring methods and problems of experimental performance, recent achievements in 2- and ]-dimensional linear/non-linear photoelasticity including photovisco-

5 elasticity, Moire- and grid-techniques, illfe1jerometric methods (holography. speckle inte1.ferometry, shearography): 11. the theory ( ~ digital f image processing and its pe1jomwnce. data-recording, -compression, -processing, -l'isuali:::ation: iii. mathematical and numerical procedures. il{formatics for emluation of measured, digiti:;,ed data. As the co-ordinator ( ~ the f CISM-course "Modem Optical Methods in Experimellfal Solid Mechanics.. and the editor ( ~ the f lecture notes I grate.fitlly thank the lecturers/autlwrsfor the e.fjectil'e co-operation and thorough re\ ising the manuscripts. the resident Rector. the General Secretary. the ChiefEditor. and explicitly the st(!ffmemhers ( ~ CISM f Secretariat.f(Jr support and excellent organisation ( ~ the f course. Many thanks to the Springer- Verlag.f(Jr publishing the lecture notes. Karl-Hans Laennann

6 CONTENTS Preface Page I. HYBRID TECHNIQUES IN EXPERIMENTAL SOLID MECHANICS by K-H. Laermann _ 1. INTRODUCTION 2 I.1 Roll and importance of optical methods in experimental Mechanics 1.2 Influence and effect on safety and reliability of structures 1.3 Presumption of applicability in industrial practice 2. PRINCIPLE OF HYBRID TECHNIQUES 7 3. NON-LINEAR PHOTOELASTICITY _ I N on-1 in ear stress-strain relations 3.2 Non-linear relation between stress state and birefringence 3. 3 Iterative discrete solution 3.4 Determination of material response 3.5 Examples of application 4. PHOTO VISCOELASTICITY. _ Preliminary remarks 4.2 Basic relations between the stress tensor and the refraction tensor 4.3 Determination of the optical relaxation function 4.4 Solution of the VOLTERRA's integral equation 5. EVALUATION OF PHOTOELASTICIVISCOELASTIC MEASUREMENTS BY MEANS OF BOUNDARY-ELEMENT METHOD I Mathematical basis 5. 2 Plane plates with inclusions 5. 3 Application to two-dimensional photoelasticity 5.4 Elastic/viscoelastic response of material 6. ANALYSIS OF 3-D-STRESS-STRAIN STATES BY MEANS OF DISCRETE BOUNDARY-INTEGRAL Determination of the surface displacement 6.2 Mathematical basis The reduction procedure Example of application 7. ANALYSIS OF 3-D-STRESS-STRAIN STATES BY COMBINING ESPI WITH FEM I Determination of surface displacements by ESPI

7 7.2 Evaluation of the experimental data by means of FEM 7.3 Example of application 8. REMARKS GENERALLY TO CONSIDER IN PERFORMING EXPERIMENTAL MECHANICS Multidisciplinary character of experimental mechanics 8.2 Necessity of advanced theories of mechanical problems 8.3 Inverse problems in final evaluation 8.4 Transfer problems related to measuring systems 9. REFERENCES 70 II. RECENT DEVELOPMENTS IN 3-D-PHOTOELASTICITY AND GRATING STRAIN MEASUREMENT by A. Lagarde _ I. THREE DIMENSIONAL PHOTOELASTICITY Present practice and new possible way 1.2 Propagation of the light wave through photoelastic medium The classical scheme ABEN schematisation Hypothesis for a thin slice Discrete analysis into thin slices 1.3 Whole-field analysis with a plane polariscope 1.4 Whole-field optical slicing method Method on the contrast measurement of one recording intensity field Method based on the variance measurement of the combination of three recording intensity fields 1.5 Separation of isoclinic and isochromatic patterns of the slice. Isostatics plotting 1.6 Conclusion and perspectives 1. 7 References 2. GRATING STRAIN MEASUREMENT Introduction 2.2 Local strain measurement Recall: Description on the move of a continuous medium Principle of the method Grating realisation Measurement by optical diffraction Measurement by spectral analysis 2.3 Improvement of the accuracy The tools of the accuracy The phase shifting method The spectral interpolation method The device 2.4 Holo-grating analysis

8 2.4.1 Holo-grating recording Holo-grating reconstruction Application to the ductile fracture 2.5 Local strain measurement in dynamic Diffraction in oblique incidence Principle of the method Implementation Experimental tests Hopkinson bar investigation 2.6 Local strain measurement on cylindrical specimen 2. 7 Conclusion and perspectives 2. 8 References III. AUTOMATED IN-PLANE MOIRE TECHNIQUES AND GRATING INTERFEROMETRY by M. Kujawinska_ _..._.. _... _.. _... _ l. THE BASIC RULES IN FULL-FIELD GRID TECHNIQUES I Basic grid moire technique 1.2 Fixed grid method 1.3 Principles of grid theory Formation of moire in incoherent light Interferometric techniques 2. GRID (GRATING) TECHNOLOGY Amplitude grids 2.2 Phase gratings 3. PRINCIPLES OF AUTOMATIC ANALYSIS OF RESULTS I Introduction 3.2 Fringe pattern analysis Phase shifting methods Fourier transform method 3.3 Phase unwrapping 3.4 Calculation of strain fields 4. THE MOIRE FRINGE METHOD Physical superimposition of gratings 4.2 Projected superimposition 4.3 Double exposures and moire photography 5. GRATING (MOIRE) INTERFEROMETRY I Introduction 5,2 Principle of grating interferometer 5.3 Grating interferometer systems The laboratory system (LGI) The workshop portable system Fibre optics grating interferometer sensor (FOS) Waveguide grating microinterferometer (WGI) 5.4 Engineering features of automated grating interterometers

9 6. MATERIAL ENGINEERING AND MICRO-MECHANICS 6.1 Introduction 6.2 Local approach to material engineering 6.3 Microelements testing 6.4 Electronic chips and packages studies 6.5 Mechanical/material joint testing 7. HYBRID METHODS OF RESIDUAL STRESS ANALYSIS 7.1 Introduction 7. 2 Objects of measurements Railway rail Laser beam weldment 7.3 Experimental set-up and procedure 7.4 Experimental results and discussion Residual strain determination for railway rails Residual stress determination in laser beam weld 7.5 Conclusions 8. CONCLUSIONS AND FUTURE POTENTIALS_ 8.1 Moire in relation to other methods 8.2 Direction of development and future potentials 9. REFERENCES _.... IV. INTERFEROMETRIC METHODS by W. Jiiptner _ 197 I. INTRODUCTION.. _ I.I Historical remarks 1.2 Properties of electromagnetic waves 1.3 Interference of waves I.4 Diffraction of light I. 5 References _.... _ HOLOGRAPHIC INTERFEROMETRY Holography Fundamentals of holography Amplitude and phase holograms Types of holograms Stability requirements for recording holograms 2.2 Holographic interferometry Fundamentals of holographic interferometry Evaluation of interference pattern 2.3 Application of holographic interferometry Non-destructive evaluation by holographic interferometry Fracture mechanics Vibration analysis 2.4 References!

10 3. DIGITAL HOLOGRAPHY Fundamentals of digital holography Principle of digital holography Recording of digital holograms Reconstruction of digital holograms Elimination of the zero-order diffraction wave 3.2 Application of digital holography Light-in-flight measurements Deformation measurement Shape measurement Non-destructive evaluation 3.4 References 4. SPECKLE PHOTOGRAPHY Fundamentals of speckles Origin of speckles Statistics of speckles Size of speckles 4.2 Speckie photography Principles of speckle photography Speckle photography with spatial filtering 4.3 Digital speckle photography (DSP) Principle of digital speckle photography Application of DSP: Deformation of a weld seam 4.4 References 5. ELECTRONIC (DIGITAL) SPECKLE INTERFEROMETRY Fundamentals of ESPI 5.2 Application of ESPI methods Deformation analysis of small components Vibration analysis of small membranes 5. 3 References 6. DIGITAL SPECKLE SHEARING INTERFEROMETRY Fundamentals of shearography 6.2 Applications of shearography Deformation measurements Non-destructive testing 6. 3 References V. DIGITAL PROCESSING AND EVALUATION OF FRINGE PATTERNS IN OPTICAL METROLOGY by W. Osten I. INTRODUCTION INTENSITY MODELS; DISTURBANCES AND SIMULATIONS Intensity relations in optical metrology

11 2.2 Modelling of the image formation process in holographic interferometry 2.3 Computer simulation of holographic interference pattern 3. TECHNIQUES FOR DIGITAL PHASE RECONSTRUCTION Methods for pre-processing of fringe pattern Smoothing of time dependent electronic noise Smoothing of speckle noise Shading correction 3.2 Methods for automatic phase measurement Fringe tracking or skeleton method Fourier-transform method Carrier-frequency method Phase-sampling method 3.3 Method for post-processing of fringe pattern Segmentation of fringe pattern The numbering of fringe pattern The fringe counting problem Methods of fringe numbering Unwrapping of mod27t - phase distributions Absolute phase measurement 4. MEASTJREMENT OF 3D-DISPLACEMENT FIELDS Planning of the experiment Basic relations Valuable a-priori knowledge Interferometer design The influence of sensitivity 4.2 Acquisition of the data Shape measurement by projected fringe technique Shape measurement by holography Shape measurement by digital holography 4.3 Evaluation of the data 4.4 Displacement calculation and data presentation 5. TECHNIQUES FOR THE QUALITATIVE EVALUATION OF FRINGE PATTERN _.. _ The technology of HNDT 5.2 Evaluation with neural networks 5.3 Evaluation with knowledge based systems 5.4 Material fault recognition in HNDT using recognition by synthesis 6. MODERN SOFTWARE SYSTEMS FOR DIGITAL PROCESS FRINGE PATTERN The simulation mode 6.2 The processing mode 6.3 The tool box 6.4 The Fringe Processor shell 7. LITERATURE _