Speckle noise reduction in full-field stress analysis by interferometric phase-stepping implementation of the photoelastic-coating method

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Full-field stress analysis by holographic phase-stepping implementation of the photoelastic-coating method

In this paper, we describe a system for polariscopic and holographic phase-shifting implementation of the photoelastic-coating method for a full-field stress analysis. The easiest way to build the combined system is to employ a laser light source. However, coherent illumination introduces a signal-dependent speckle noise which worsens the accurate phase estimation and unwrapping. To answer the question of how it affects the phase retrieval of isochromatics, isoclinics and isopachics, we modeled in the present paper the phase-shifting photoelastic measurement in the presence of speckle noise through the calculation of the complex amplitudes in a Mach-Zender interferometer combined with a circular polariscope and made denoising of simulated and experimental fringe patterns. The latter were recorded at pure tensile load for PhotoStress (R)-coated samples with a mechanical stress concentrator

Concrete face rockfill dam located on deformed foundation: stress-strain state

Concrete face rockfill dam (CFRD) located on soil foundation has a composite structure of the seepage control facility. It includes three elements: the dam concrete face, the seepage control cuttoff wall (CW) in the foundation and the concrete apron connecting them. There is an urgent task to study workability and stress-strain state (SSS) of the seepage control facility as a whole structure as well as each element separately. Method. The SSS analysis of an abstract dam with the aid of numerical modeling was conducted to solve this task. A 100 m high CFRD located on a 100 m thick foundation layer was considered. Analyses were conducted for several alternatives of foundation soils with deformation modulus from 40 to 5000 МPа. Results. The analyses showed that the SSS of the dam on the soil foundation drastically differs from the SSS of the dam on the rock foundation. The concrete face and the cuttoff wall are subject to considerable compressive longitudinal forces. Due to bending deformations in CW and the concrete apron, considerable tensile stresses may occur. Conclusions. A number of recommendations was formulated for providing strength of the elements of the composite seepage control facility of the dam on soil foundation. To provide strength of the concrete face it is necessary that the deformability of the dam soil be close to the foundation soil. To provide CW with strength, it is recommended use the material with rigidity of no more than by 2–3 times greater than the foundation soil rigidity. The most vulnerable element of the structure of the composite seepage control facility is the concrete apron. To avoid cracking in it, it should be cut by transversal joints to form separate slabs

Optical Properties of Charged Polymer with Nano-sized Zeolite Inclusions

The optical characteristics of photopolymer films doped with nanoparticles are studied. The investigated systems consist of a soft polymer matrix containing porous zeolite nanoparticles with concentrations varied in the range from 0wt.% to 7wt.%. 40μm thick layers are obtained by casting the photopolymer nanocomposite solution on glass substrates. The corona charging influence on the transmission spectra and on the surface and the effective refractive index of the dry layers is investigated

WORKING OUT OF MAIN EXEMPLARY EDUCATIONAL PROGRAMS FOR BACHELORS, MASTERS AND SPECIALISTS IN THE FIELD OF CONSTRUCTION

Introduction. The system of higher education in Russia is in the state of permanent transformation. During the recent period the aim of transformations has been adapting professional educational programs to the demands of community of professionals. The result of these transformations is approval of updated federal state educational standards, which obtained abbreviation “FSES 3++”. The essence of the standards updating is in establishing rules of accounting professional standards at development of professional educational programs. Starting from 2019 the training of personnel for construction industry will be fulfilled in compliance with FSES 3++. The training content of graduates is determined by educational organizations in compliance with exemplary main educational programs (EMEP). The article describes the experience of Federal educational methodical association in the system of higher education in an enlarged group of specialties and areas of training 08.00.00 Engineering and construction technology for development of EMEP. Materials and methods. In order to ensure the uniformity of the requirements for education of graduates of different profiles and qualifications, it was decided to develop EMEP for each of the main directions (profiles) of educational programs. As part of the development of EMEP, a methodology for formulating professional competencies based on an analysis of the requirements of professional standards was proposed and applied. Formulation of indicators of achievements in competencies was carried out in the form of a description of labour actions. Results. To date several draft EMEPs have been worked out for different directions and levels of education. A proven methodology for development of EMEP is used to compile EMEP for other areas. Conclusions. The process of harmonizing the educational and professional standards will permit not only solving the problem of professional orientation of educational programs, but also in this regard the task of ensuring quality of graduates training required by employers. For this purpose, EMEP should be developed separately according to the directions of educational programs and establish mandatory professional competencies. Such an approach to the development of EMEP also ensures the achievement of unity of the educational system as one of the requirements of the Federal Law “On Education in the Russian Federation”

Holographic Recording in Charged Photopolymerisable Nanocomposites

Self – processing photopolymers have a large number of different applications due to their versatile properties as holographic recording materials. A significant effort has been directed towards the development of photopolymers for holographic data storage [1, 2], holographic sensors [3], holographic optical elements [4] and display holograms [5]. The Centre for Industrial and Engineering Optics has been developing acrylamide based photopolymers for the last decade [6-8]. The main parameters requiring improvement in these types of photopolymers are their dynamic range and their mechanical stability during the holographic recording. Recently we have successfully used zeolite nanoparticles as dopants in order to increase the dynamic range and lower the shrinkage in acrylamide-based photopolymers [9]. The advantages of using zeolite nanoparticles in colloidal form are their stability in water suspension: they have the same pH as the photopolymer and can be synthesized with different shape, size and chemical composition. Depending on the chemical composition and types of the structure, the zeolites will exhibit variable refractive index. Among the different types of zeolite nanoparticles used for doping of photopolymers, the pure silica MFI (Si-MFI) has shown the best results [9]. Having in mind that the zeolites are negatively surface charged it is expected to be an appropriate dopant for photopolymers [10]. We studied the effect of the charging of the photosensitive layers on their holographic recording properties. The charging was achieved by exposure to corona discharge. Different types of charges – positive and negative were deposited on the layer surfaces. It was observed that their presence influences the diffraction efficiency of recording

Projection moire measurement of glass specimens retrofitted with safety film

Protection of buildings and critical public infrastructure against blast load has been recently improved by retrofitting glass windows with a safety film. As the exact physical mechanisms of the interaction between glass and safety film are not quite well understood, intensive research is conducted on the properties of this assembly. The loadings on the glass/film assembly are typically dynamic (blast, wind pressure, impact), so the lab tests are done on a drop weight set-up, where a mass is falling on a retrofitted glass plate. In this work, the drop weight setup was combined with pattern projection (moire) technique to study the time history of the out-of-plane deformations of the glass/film assembly. The fringe pattern, projected on the back side of the specimen, was generated by means of a sinusoidal phase grating under divergent high intensity infrared illumination. The whole process was recorded with a high speed camera. Local routines based on fast Fourier transform were used to process the captured images, and to extract the phase. The exact out-of-plane displacements were calculated by means of calibration based on previous shape measurements of several different objects with known dimensions

SEISMIC STABILITY OF THE MOORING WALL ACCORDING TO THE RESULTS OF NUMERICAL SIMULATION

Introduction. New building codes provide for a significant increase in the magnitude of seismic loads that should be perceived by hydraulic structures. In this regard, even in areas with low seismic activity, there may be a problem of ensuring the seismic stability of hydraulic structures. This is particularly acute in berthing facilities. As a rule, they are not so massive to withstand seismic loads. The issue of seismic stability of berthing facilities has not yet been properly considered. The results of numerical simulation of the seismic stability of the mooring-dividing wall during a 7-point earthquake are considered. A structure about 24 m high located on a non-rock base was investigated. Materials and methods. The seismic stability of the mooring structure was estimated by calculating its stress-strain state under the action of seismic forces. Calculations were carried out by the finite element method. Seismic loads on the structure were determined in two ways — by linear-spectral theory and by dynamic theory. For the calculation of seismic loads, 30 lower frequencies and the natural mode of the structure were determined together with an array of its base. When calculating according to the dynamic theory, the seismic effect was specified in the form of an accelerogram adopted for similar conditions. The direction of seismic impact was assumed horizontal. Results. According to the dynamic theory, seismic loads turned out to be lower than according to linear-spectral theory. However, the results of the calculation of the stress-strain state of the mooring structure were close. It was found that the seismic forces on the mooring wall will reach about a quarter of the weight of the structure. Under the influence of such forces, the mooring wall will lose its stability. Conclusions. To ensure seismic stability, it is recommended to combine the mooring wall and the base plate into a single monolithic structure, as well as to strengthen the lower part of the structure and facilitate the upper one

Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones

Bulk samples of carbon multilayer nanotubes with the structure of nested cones (fishbone structure) suitable for transport measurements, were prepared by compressing under high pressure (~25 kbar) a nanotube precursor synthesized through thermal decomposition of polyethylene catalyzed by nickel. The structure of the initial nanotube material was studied using high-resolution transmission electron microscopy. In the low-temperature range (4.2 - 100 K) the electric resistance of the samples changes according to the law ln \rho ~ (T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in the magnetic field and linear in the reciprocal temperature. The measurements have been interpreted in terms of two-dimensional variable-range hopping conductivity. It is suggested that the space between the inside and outside walls of nanotubes acts as a two-dimensional conducting medium. Estimates suggest a high value of the density of electron states at the Fermi level of about 5 10^{21} eV^{-1} cm^{-3}.Comment: 8 pages, 4 figures. EM photographic images on figures 1a, 1b, 1c attached as JPG files. For correspondence mail to [email protected]

Trends in development of dynamic holographic displays

Creation of a dynamic 3-D display based on holography, in which a 3-D scene is encoded in terms of optical diffraction, transformed into the fringe patterns of the hologram that is further converted into a signal for a spatial light modulator (SLM) and displayed in real time, is an extremely challenging enterprise. There are various approaches targeted to solve associated problems