The Application of Laser Speckle Interferometry to Measure Strain at Elevated Temperatures and Various Loading Rates


Book Description

This report investigates the application of speckle interferometry for the measurement of strain when a material is subjected to various loading rates and elevated temperature conditions. The Medium Strain Rate Facility at the U.S. Army Materials Technology Laboratory was used to conduct uniaxial tension tests at strain rates of .00001/sec to .1/sec, temperatures up to 250 deg F and heating rates of 250 deg F/sec. Strain was measured by laser speckle interferometry technique and strain gages, the results of both methods were compared. Laser speckle interferometry was also used for the measurement of strain at large deformation, i.e., necking region of tensile specimens. The laser speckle interferometry results are in agreement with strain gage results at strain rates up to .1/sec for temperatures up to 250 deg F. This investigation also indicated laser speckle interferometry would be an excellent noncontact localized strain measuring device for adverse conditions if the following drawbacks were overcome. When using the ruby laser system, only one stress-strain data point can be obtained, the present system is not suited for strain rates over .1/sec and no results can be obtained if the specimen is heated to a point that it begins to emit intense red light. The shortcomings of laser speckle interferometry could be overcome by using another laser and data acquisition system. Keywords: Interferometry, Strain rate, Deformation temperature, Tension, Stress/strain relations, Speckle lasers.




A Study of the Parameters Associated with Employing Laser Speckle Correlation Fringes to Measure In-plane Strain


Book Description

"Basic experimental parameters associated with using laser speckle correlation fringes to measure in-plane strain have been investigated. Equations and inequalities are derived which provide bounding numbers for many of the physical parameters. The feasibility of employing this technique for obtaining in-plane strain data in a microscopic region is shown. This suggests that it may be applicable for studying strain distributions in the vicinity of either a crack or an interference fit fastener." -- Abstract.




Research in Progress


Book Description







Holographic and Speckle Interferometry


Book Description

Holographic and speckle interferometry are optical techniques which use lasers to make non-contracting field view measurements at a sensitivity of the wavelength of light on optically rough (i.e. non-mirrored) surfaces. They may be used to measure static or dynamic displacements, the shape of objects, and refractive index variations of transparent media. As such, these techniques have been applied to the solution of a wide range of problems in strain and vibrational analysis, non-destructive testing (NDT), component inspection and design analysis and fluid flow visualisation. This book provides a self-contained, unified, theoretical analysis of the basic principles and associated opto-electronic techniques (for example Electronic Speckle Pattern Interferometry). In addition, a detailed discussion of experimental design and practical application to the solution of physical problems is presented. In this new edition, the authors have taken the opportunity to include a much more coherent description of more than twenty individual case studies that are representative of the main uses to which the techniques are put. The Bibliography has also been brought up to date.




Scientific and Technical Aerospace Reports


Book Description

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.




Basics of Interferometry


Book Description

This book is for those who have some knowledge of optics, but little or no previous experience in interferometry. Accordingly, the carefully designed presentation helps readers easily find and assimilate the interferometric techniques they need for precision measurements. Mathematics is held to a minimum, and the topics covered are also summarized in capsule overviews at the beginning and end of each chapter. Each chapter also contains a set of worked problems that give a feel for numbers. The first five chapters present a clear tutorial review of fundamentals. Chapters six and seven discuss the types of lasers and photodetectors used in interferometry. The next eight chapters describe key applications of interferometry: measurements of length, optical testing, studies of refractive index fields, interference microscopy, holographic and speckle interferometry, interferometric sensors, interference spectroscopy, and Fourier-transform spectroscopy. The final chapter offers suggestions on choosing and setting up an interferometer.




Speckle Metrology


Book Description

This practical reference offers state-of-the-art coverage of speckle metrology and its value as a measuring technique in industry.;Examing every important aspect of the field, Speckle Metrology: surveys the origin of speckle displacement and decorrelation; presents procedures for deformation analysis and shape measurement of rough objects; explains particle image velocimetry (PIV), the processing of PIV records, and the design requirements of PIV equipment; discusses the applications of white light speckle methods and the production of artificial speckles; describes the measurement of surface roughness with laser speckles and polychromatic speckles; illustrates semiautomatic and automatic methods for the analysis of Young's fringes; calculates the variation of Young's fringes with the change in the microrelief of the rough surface; and explicates hololenses for imaging and provides design details with aberration corrections for hololense systems.;With over 1500 literature citations, tables, figures and display equations, Speckle Metrology is a resource for students and professionals in the fields of optical, mechanical, electrical and electronics engineering; applied physics; and stress analysis.




Interferometry in Speckle Light


Book Description

These proceedings reflect the work presented at the conference "Interferometry in Speckle Light: Theory and Applications", held at the Ecole Polytechnique Federale de Lausanne, (EPFL), the Swiss Federal Institute of Technology in Lausanne, Switzerland. The event took place from September 25 to September 28, 2000. Thanks to the diligence of the authors, this book has been published just in time for the conference. Writing this preface in July, in anticipation of the conference, we have tried to envisage how this book will benefit the quality of discourse between authors and attendees. "Interferometry in Speckle Light: Theory and Applications" results from a bottom-up approach and is original in several ways. This conference is not part of a series; on the contrary, it is a single event. The idea of gathering scientists and engineers for a general discussion on the theory and the practice of interferometry, involving rough, non-optically polished objects, was "in the air". An opportunity of this sort was not provided by any of the conferences scheduled when the present one was conceived. For this reason, it was easy to convince a small number of renowned researchers, all of them active in the field of holographic and speckle interferometry, to organize a conference. To be specific, they are the people listed below as members of the scientific and local committees. At the same time, a particular circumstance, namely the retirement of Professor L. Pflug, helped to detennine the location of the meeting.