A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Fringe projection techniques: Whither we are?

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.

A review on basalt fibre and its composites

http://eia.udg.es/~qsalvi/papers/2010-PR.pdf

A state of the art in structured light patterns for surface profilometry

Over the years, the building envelope has evolved from a protective barrier element to a complex filter system capable of optimizing the interactions between the external and internal environments. An efficient envelope reacts flexibly to variable external conditions, minimizing heat losses in the winter season. Therefore, insulating materials play a fundamental role in building’s thermal performance. In this scenario, Additive Manufacturing represents an emerging and promising solution for the construction sector. Three-dimensional printing allows the creation of custom geometries, reduces material waste, and automates the construction process. This work aims to compare the thermal performance of a PLA (polylactic acid) 3D-printed block with an internal honeycomb structure whose air cavities are filled with natural and recyclable waste-insulating materials. The selected air cavity filling materials are (i) wood sawdust, (ii) sheep’s wool, and (iii) hemp. The thermal behavior of the block with the different filling materials was experimentally tested via Heat Flow Meter (HFM) method in a controlled environment (Hot Box). The results showed that the introduction of waste material significantly improved the thermal performance of the 3D-printed block compared to the case of air cavities. A thermal transmittance (U-value) reduction of up to 57% was obtained. Moreover, the sheep’s wool showed the best performance, with a U-value equal to 0.53 ± 0.02 W/m2K, i.e., 18.5% less than the wood sawdust and 19.7% less than hemp.

/pdf/on-the-use-of-waste-materials-for-thermal-improvement-of-3d-1z1r54va.pdf

On the Use of Waste Materials for Thermal Improvement of 3D-Printed Block—An Experimental Comparison

Today, the vibration analysis of laminated structures represents an important field in engineering metrology. The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. However to perform full-field, non-contact, and real-time measurement, optical methods are a preferable choice.
Recently, interesting results have been obtained by Electronic Speckle Pattern Interferometry (ESPI). In this paper, we report an alternative electro-optical system based on local digital speckle correlation. This new method permits the development of an instrument that is cheap, safe and easy to use. We employ the proposed method to investigate the vibration characteristics of piezoceramic/nickel-alloy laminated plate. The circular membrane is a composite made of a nickel alloy disk with thickness 0.1 mm and diameter 30 mm, to which a piezoceramic disk, with the same thickness and a smaller diameter (24 mm) is bonded. A brief analysis of the technique and some experimental results are presented. Finally, the numerical finite element calculation is also performed, and the results are compared with the electro-optical measurements.

Vibration analysis of layered structures by digital local correlation of laser speckle

A system for the sampling of inhalable airborne particles.

An interferometric technique based on the use of a diffraction grating is used to recover the intensity distribution across a spatially incoherent planar source. Information about the source profile is obtained through measurements of visibility and position of the fringe pattern at transverse planes beyond the grating. Such quantities are shown to be independent of the wavelength of the radiation, so that broadband sources can be analysed without any spectral filtering. Experimental results are given.

/pdf/experimental-determination-of-the-intensity-distribution-el1sfty5l3.pdf

Experimental determination of the intensity distribution across a source with a grating interferometer

In this paper we present an unwrapping weighted algorithm to analyze phase maps obtained by fringe projection 3-D profilometry. 
Phase unwrapping is a critical step in any phase measurement technique in which the height of an object is obtained from phase data. Indeed, when a complex object is measured, abrupt and irregular changes in the measured surface may result in local shadows. In shadow areas the observed phase data are uncertain or misleading. These zones yield “lacunae”, in the reconstruction of the 3D model.
In this work we propose a new phase unwrapping method able to mitigate the “lacunae” problem by interpolation of phase data.
The case of an image containing regions without phase information is treated, in our algorithm in the following manner: (a) phase inconsistencies are handled by excluding invalid pixels from the unwrapping process though the assignment of zero-valued weights; (b) an unwrapped phase map is obtained by an algorithm based on robust, path-independent method of phase unwrapping; (c) the lacks (zones of phase inconsistencies) are eliminated by means of an suitable procedure of interpolation; (d) a rewrapping procedure is used to obtain wrapped phase map without initial inconsistencies; (e) a new unwrapped phase map is obtained by the same algorithm used in step-b but with weights different from zero. The robustness of the proposed phase-unwrapping method is then tested computationally and experimentally and its enhancement is proven through the simulation and experimental results.

Domenica Paoletti

Papers

On the Use of Waste Materials for Thermal Improvement of 3D-Printed Block—An Experimental Comparison

Vibration analysis of layered structures by digital local correlation of laser speckle

A system for the sampling of inhalable airborne particles.

Experimental determination of the intensity distribution across a source with a grating interferometer

Unwrapping weighted algorithm in fringe projection 3D profilometry