published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Digital heterodyne methods are employed in conjunction with periodic fringe projection to produce a fast automated surface relief measurement technique. A method of sampling the image with a solid state detector array which produces a moire fringe image free of the noise terms normally present with moire techniques is presented along with an extension to Whittaker-Shannon sampling theory to cover the moire aliasing phenomena. The limitations imposed on the surface slopes by the requirement that the properly moire sampled image spectra must be confined to a moire interval are given. Moire sampling allows an optical processing step (removal of the reference surface tilt), while classical nonaliased sampling produces the same information with respect to a tilted surface. General additive noise is analyzed as regards both integrating bucket and phase stepping algorithms and yields a signal to noise ratio dependent error with twice the frequency of the fringes for some algorithms. A phase averaging technique which eliminates these oscillatory errors as well as those caused by reference phase shift errors in all the algorithms is demonstrated. Both parallel and divergent geometries are discussed. The feasibility is experimentally demonstrated with results for the parallel case based on a system composed of commercially obtainable components.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

The objective of this study was to provide an optical technique allowing full-field in-plane deformation measurements at high temperature by using high-sensitivity moiré interferometry. This was achieved by a new approach of performing deformation measurements at high temperatures in a vacuum oven using an achromatic interferometer. The moiré system setup was designed with particular consideration for the stability, compactness, flexibility, and ease of control. A vacuum testing environment was provided to minimize the instability of the patterns by protecting the optical instruments from the thermal convection currents. Also, a preparation procedure for the high-temperature specimen grating was developed with the use of the plasma-etched technique. Gold was used as a metallic layer in this procedure. This method was demonstrated on a ceramic block, metal/matrix composite, and quartz. Thermal deformation of a quartz specimen was successfully measured in vacuum at 980 degrees Celsius, with the sensitivity of 417 nm per fringe. The stable and well-defined interference patterns confirmed the feasibility of the developments, including the high-temperature moiré system and high-temperature specimen grating. The moiré system was demonstrated to be vibration-insensitive. Also, the contrast of interference fringes at high temperature was enhanced by means of a spatial filter and a narrow band interference filter to minimize the background noise from the glow of the specimen and heater. The system was verified by a free thermal expansion test of an aluminum block. Good agreement demonstrated the validity of the optical design. The measurements of thermal deformation mismatch were performed on a graphite/epoxy composite, a metal/matrix composite equipped with an optical fiber, and a cutting tool bit. A high-resolution data-reduction technique was used to measure the Strain distribution of the cutting tool bit. / Ph. D.

A new hybrid method combining moire interferometry, high resolution data-reduction technique, two-dimensional datasmoothing method, and Finite Element Method (FEM) has been successfully developed. This hybrid method has been applied to residual strain analyses of composite panels, strain concentrations around optical fibers embedded in composites, and cruciform composite shear test. This hybrid method allows moire data to be collected with higher precision and accuracy by digitizing overexposed moire patterns (U & V fields) with appropriate carrier fringes. The resolution of the data is ± 20 nm. The data extracted from the moire patterns are interfaced to an FEM package through an automatic mesh generator. This mesh generator produces a nonuniform FEM mesh by connecting the digitized data points into triangles. The mesh, which uses digitized displacement data as boundary conditions, is then fed to and processed by a commercial FEM package. Due to the natural scatter of the displacement data digitized from moire patterns, the accuracy of strain values is significantly affected. A modified finite-element model with linear spring elements is introduced so data-smoothing can be done easily in two dimensional space. The results of the data smoothing are controlled by limiting the stretch of those springs to be less than the resolution of the experimental method. With the full-field hybrid method, the strain contours from moire interferometry can be easily obtained with good accuracy. If the properties of the material are known, the stress patterns can also be obtained. In addition, this method can be used to analyze any two-dimensional displacement data, including the grid method and holography. / Ph. D.

Moiré interferometry is a relatively new branch of photomechanics that utilizes a diffraction grating on the specimen to determine surface displacements. To date, it has been used primarily to determine in-plane displacements of the specimen surface. The objective of this work is to demonstrate that the technique is capable of determining out-of-plane displacements as well. A high-frequency phase grating on a specimen surface is illuminated by oblique beams; two diffracted beams are recorded by holographic interferometry. If the wavefront warpages of the two diffracted beams are characterized by fringe orders, Nₐ and N_b, it is demonstrated that the in-plane displacements are proportional to Nₐ - N_b, while out-of-plane displacements are proportional to Nₐ + N_b. Initially, these subtractive and additive parameters are determined numerically, and the resulting displacements are compared to displacements measured by well-accepted prior experimental methods. Excellent agreement with these proven methods is shown. Using this remarkably simple relationship between wavefront warpages, an experimental procedure is developed which is capable of simultaneously determining the in-plane and out-of-plane displacements of a specimen surface. The method requires only one photographic exposure of the deformed specimen, with displacement information being extracted through the use of optical filtering. The fact that the information required to yield these patterns can be obtained from a single photographic recording not only makes this an experimentally simple technique to use, but provides the capability of analyzing dynamic events as well. The sensitivity of measurements made by utilizing this technique are directly proportional to the frequency of the specimen grating. Therefore, it is desirable to obtain specimen gratings with frequencies on the order of 500-2000 lines/mm ( 12, 700 - 50,800 lines/in.). A technique is developed whereby high frequency moire gratings with highly reflective surfaces can be transferred to workpieces made from most engineering materials. Specimen gratings with frequencies as high as 2000 lines/mm (50,800 lines/in.) and exhibiting 10 percent diffraction efficiency in the first diffraction order have been applied to numerous specimens using simple laboratory techniques. / Ph. D.

Orientador: Inácio Maria Dal Fabbro / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-23T11:41:51Z (GMT). No. of bitstreams: 1 Gazzola_Jonathan_D.pdf: 4193064 bytes, checksum: cfa66521e595db19afcd4c8f16250515 (MD5) Previous issue date: 2013 / Resumo: A distribuição de tensões em corpos dá suporte à engenharia de projetos visando à melhoria da qualidade e segurança de produtos e atualmente são determinados por métodos analíticos e experimentais. A vantagem dos métodos experimentais em relação aos métodos analíticos está em analisar a distribuição de tensões e deformações independentemente das condições do material e de sua geometria. Entre os métodos experimentais, as técnicas ópticas que tem se demonstrado propícias são holografia, speckle interferométrico e as técnicas de moiré. As técnicas ópticas interferométricas permitem determinar campos de deslocamento, porém, quando combinados com métodos híbridos se tornam passíveis de determinação do componente de tensões e deformações específicas e são comumente conhecidas como técnicas fotomecânicas. As técnicas de moiré são conhecidas por sua habilidade em determinar topografia de objetos, porém, pesquisas recentes têm mostrado muito útil em determinar campo de deslocamento. A técnica de moiré é baseada na fenomenologia moiré, na qual, duas grades superpostas produzem franjas padrões e, por meio de tratamento de imagem adequado permite deduzir qualitativamente o mapa de distribuição de tensões e deformações. Os principais tipos de técnicas de moiré são de sombra e por phase-shifting e seu arranjo experimental consiste no uso de equipamentos de baixo custo, o que o torna altamente viável, frente às outras técnicas ópticas. A proposta deste trabalho de pesquisa se identifica em analisar o uso da técnica de moiré por phase-shifting para determinação de tensões e deformações de forma qualitativa e quantitativa a partir do campo de deslocamento determinado experimentalmente. Para validação, os resultados gerados pela técnica de moiré foram comparados com os resultados obtidos por ensaio experimental de extensometria elétrica e simulação computacional. Os resultados mostraram que qualitativamente, a técnica de moiré foi hábil em determinar campo de deslocamento, enquanto que, quantitativamente a técnica foi hábil em determinar campo de deslocamento, deformações e tensões / Abstract: Stress distribution in specimens supports the design engineering objectiving quality and insurance products improvement and actually are determined through analytical and experimental analyses. Analyzes of stress and strain distribution independently of material conditions and its geometry becomes advantage of experimental methods, in relation to analytical methods. Among experimental methods, optical techniques have demonstrated to be favorable are holography, interferometrical speckle and moiré techniques. Interferometrical optical techniques allow to determine displacement fields, but, when associated to hybrid methods, they become able to stress and strain components determination and they are usually named as photomechanical technique. Moiré technique is known for its hability to determine shape surface, but, researches have demonstrated to be usefull to determine displacement field. Moiré technique is based about moiré phenomenology, which, two superposed grids produces pattern fringes and, applying an adequated image treatment is possible to deduce qualitatively the stress and strain distribution mapping. The main kind of moiré technique are shadow and phase-shifting and its setup is based in use of low cost equipments, which becomes highly feasible, when compared to other optical techniques. This research work objectives to analyze the use of phase-shifting moiré technique to stress and strain determination qualitative and quantitatively using datas of displacement field determined experimentally. Results obtained through moiré technique were validated comparing results obtained through etectrical extensometry experimental tests and computational simulation. Results showed that qualitatively, moiré technique was able to determine displacement field, while quantitatively moiré was able to determine displacement, strain and stress / Doutorado / Maquinas Agricolas / Doutor em Engenharia Agrícola

The objective of this research was to provide means for the experimental analysis of deformations encountered in micromechanics. Whole field contour maps of U and V displacements in a microscopic field of view were desired. Since displacements within a small field can be very small even when strains are large, ultra-high sensitivity is required. The specific objective was displacement sensitivity of 50 nm per fringe contour, which corresponds to that of moire with 20,000 lines per mm, in combination with spatial resolution of the optical microscope (2-5 μm). The objective was achieved by the following developments. First, the basic sensitivity of moire interferometry was increased beyond the previously conceived theoretical limit. This was accomplished by creating the virtual reference grating inside a refractive medium instead of air, thus shortening the wavelength of light. A very compact four beam moire interferometer in a refractive medium was developed for microscopic viewing, which produced a basic sensitivity of 208 nm per fringe order. Its configuration made it inherently stable and relatively insensitive to environmental disturbances. An optical microscope was employed as the image recording system to obtain the desired spatial resolution. Secondly, a fringe multiplication scheme was implemented. Here, an automatic fringe shifting and fringe sharpening scheme was developed, wherein very thin fringe contours of order N* = βN were produced, where N is the fringe order in the basic moire pattern and β is a fringe multiplication factor. A factor of 12 was achieved, providing a sensitivity of 17 nm per fringe contour. This corresponds to moire with 57,600 lines per mm (1,463,000 lines per in.), which exceeds the sensitivity objective. The mechanical and electronic systems implemented here are remarkably robust and quick. The method was demonstrated with three practical applications: interface strains in a thick 0°/90° graphite/epoxy composite, fiber/matrix deformations of metal/matrix composites, and thermal deformation around a solder joint in a microelectronic subassembly. / Ph. D.

Techniques for shear property measurements for composite and isotropic materials were investigated. A new strain gage called the shear gage was conceived, designed, and tested for routine shear characterization on notched shear specimens. The shear gage integrates the shear strain in the entire test section of the losipescu and compact shear specimens. The result was consistent and accurate determination of the shear stress/strain response of materials. Prior knowledge of material properties or shear strain distributions were not required. Deficiencies in the losipescu shear test were automatically compensated when shear gages were placed on the two faces of the specimen. The shear gages were tested on composite and isotropic materials and produced higher accuracy and consistency than could be produced using current technology. Moir© interferometry was used to evaluate the ability of the shear gage to measure the average shear strains. The results from the evaluation program confirmed the attributes of the concept. / Ph. D.

This paper presents the theory and results of three Moire methods 1) the incoherent projection Moire method, 2) the electronic phase detection method, and 3) the fringe multiplication method. It is proposed that these three methods be used together in a system to measure out-of-plane displacements of large diffusely reflecting surfaces. The operation of the system is divided into two processes. The first process records an incoherent moire pattern which contains the out-of-plane displacement information. The second process uses a transduced coherent image of the pattern produced in the first process to optically generate a quantitative result with variable sensitivity. The coherent processing is a technique that uses the fringe multiplication method with the electronic phase-detection method. The result is the quantitative, out-of-plane displacement measurement with sensitivity enhancement that can be altered during coherent processing of the Moire fringe pattern. / Master of Science