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Abstract: Scanning white light interferometry (SWLI) is an increasingly popular method to measure the surface profile of miniature components. Although it is tolerant to step changes in profile, its capability to measure the large surface gradients that are characteristic of high‐aspect‐ratio surfaces is limited. This is in part due to the numerical aperture of the objective lens which restricts...
Abstract: In this paper, the effect of imposing continuity constraints in real and complex image correlation has been investigated. It is found that in regions where continuity can be assumed a second‐order spline expansion of the underlying deformation field provides a globally smooth estimate of the deformation field. In general, only an estimate of the deformation at the subinterval centres needs...
Abstract: A microscale three‐point bend experiment on wood has been carried out. The full 3D strain field of the microscale wood structure has been determined by use of digital volume correlation, based on reconstructed 3D image data acquired with synchrotron radiation micro‐computed tomography. The wood specimen, which measures 1.57 × 3.42 × 0.75 mm3, was scanned in different load states along the...
Abstract: This paper presents methods for vibration analysis using digital Fresnel holography. Methods are based on time averaging for forced oscillations and pulsed recording devoted to auto‐oscillations. The two methods are applied to a clarinet reed. In the forced oscillation regime, the reed is excited by an acoustic wave with controlled frequency and amplitude such that the reconstructed holograms...
Abstract: We demonstrate that polarisation‐sensitive optical coherence tomography (PS‐OCT) is suitable for mapping the stress distribution within materials in a contact‐free and non‐destructive way. In contrast to transmission photoelasticity measurements, the samples do not have to be transparent but can be of scattering nature. Denoising and analysis of fringe patterns in single PS‐OCT retardation...
Abstract: As an improvement of the intensity correlation used widely in conventional electronic speckle photography, we propose a new technique for displacement measurement based on correlating Stokes‐like parameters derivatives for transformed speckle patterns. The method is based on a Riesz transform of the intensity speckle pattern, which converts the original real‐valued signal into a complex...
Abstract: Digital image correlation techniques (DIC) are applied to sequences of optical images of argillaceous rock samples submitted to uniaxial compression at various saturation states at both the global centimetric scale of the samples and the local scale of their composite microstructure, made of a water‐sensitive clay matrix and other mineral inclusions with a typical size of 50 μm. Various...
Abstract: Heterogeneous dissipation in steel sheets due to cyclic loading is difficult to measure, especially in the transverse direction because of the high conductivity and low thickness of the sheets. The goal of this article is thus to develop an experimental protocol allowing for the dissipation field determination from infrared thermography. The protocol is based on a specific differential...
Abstract: The paper aims to highlight the advantages of using data supplied by digital image correlation (DIC) and infrared thermography (IRT) to study the thermomechanical behaviour of materials. It describes an experimental procedure for the determination of mechanical energy and heat sources involved locally during a heterogeneous tensile test. This procedure involves two complementary imaging...
Abstract: Digital image correlation (DIC) is used to monitor strain in a representative textile material and an historic tapestry. The validity of a ‘map function’ that allows 3D DIC displacement measurements to be obtained when the reference data are collected with a camera set‐up different from that of the deformed data is assessed. An experiment was devised to study the effects of DIC processing...
Abstract: Optical techniques are well suited for the measurement of microcomponents but give accurate results only when calibrated systems are used. This paper presents the development of a standard reference device whose in‐plane displacement is precisely reproducible when submitted to standard loadings. The reference device has been manufactured and tested by optical measuring systems. This reference...
Abstract: The purpose of this paper is to provide a comparison between embedding tests covered by the EN383 and ASTM D5764 standards, highlighting some difficulties regarding the application of the referred standards. These embedding tests are essential to evaluate the embedding strength of wood, which is required for the assessment of joints strength. The proposed comparison is based either on experimental...
Abstract: The response of three different cellular core types, suitable for manufacturing crashworthiness sandwich cellular structures, is investigated in this paper. A methodology is developed, comprising linear static and eigenvalue buckling analysis, as well as nonlinear material elastoplastic analysis. The methodology is used to study the structural response and failure process of open lattice...
Abstract: During a dynamic mechanical loading, we cannot use a phase‐shifting technique because the mechanical parameters evolve according to the time. This problem can be avoided by the development of algorithms which can extract the mechanical information from only one fringe pattern. In this way, we present two algorithms, the modulated phase correlation (MPC) and the polynomial modulated phase...
Abstract: With advancements in digital image processing and data acquisition, a separate branch of photoelasticity namely digital photoelasticity came into existence. Here, intensity information of the acquired image is used for the evaluation of whole‐field photoelastic parameters. Digital photoelasticity provides only wrapped phasemaps of isoclinics and isochromatics and they have to be unwrapped...
Abstract: This paper considers the main developments of RGB photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe...
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