Deformation analysisof rectangular composite flexible membrane of the photovoltaic space solar array

The thin flexible composite membrane stretched on the frame of space solar array should be capable of withstanding the mechanical loadings exerted on the structure during the delivery to orbit and deployment. Nonlinear analysis of the deflections of the orthotropic flexible membrane stretched over the rectangular frame cell and subjected to transverse loading is presented in this paper

Computational modelling of progressive failure of composite materials and structures including plasticity effects

The paper is concerned with the development and verification of the computational algorithm enabling the progressive failure simulation that takes into account plasticity effects in addition to the damage progression to be performed for composite materials and structures. The numerical approach is based on the combined elastoplastic damage model that accounts for the irreversible strains caused by plasticity effects and material properties degradation due to the damage initiation and development. The strain-driven implicit integration procedure is developed using equations of continuum damage mechanics, plasticity theory and includes the return mapping algorithm. A tangent operator that is consistent with the integration procedure is derived to ensure a computational efficiency of the Newton-Raphson method in the finite element analysis. The algorithm is implemented in ABAQUS as a user-defined subroutine. Prediction of the damage initiation in the laminated composite takes into account various failure mechanisms making use of Hashin’s failure criterion. The plasticity effects in composite material are modelled using the approach developed by C. T. Sun and J. L. Chen. The efficiency of the modelling approach and computational procedure is verified using the analysis of the progressive failure of composite laminates made of carbon fibre reinforced plastic and subjected to in-plane uniaxial tensile loading. It has been shown that the predicted results agree well with the experimental data

USING THE SPH METHOD FOR MODELING THE CRYSTALLIZATION PROCESS OF ALUMINUM ALLOYS

The purpose of the study was to obtain castings with increased mechanical properties by low-pressure casting using excess pressure on the crystallized casting. The simulation of the process of filling and crystallization of prototypes using the SPH method was carried out. The studies were carried out on a modernized low-pressure injection molding machine model U8261. Prototypes were obtained from AK7ch alloy, special attention is paid to interfacial interaction and intensification of the heat transfer process due to the application of excess pressure. Based on the data obtained, it was found that during crystallization under excessive pressure there is a supercooling effect that reduces the casting solidification time. The use of the SPH method for modeling foundry processes has shown a high level of reliability and requires further development.The purpose of the study was to obtain castings with increased mechanical properties by low-pressure casting using excess pressure on the crystallized casting. The simulation of the process of filling and crystallization of prototypes using the SPH method was carried out. The studies were carried out on a modernized low-pressure injection molding machine model U8261. Prototypes were obtained from AK7ch alloy, special attention is paid to interfacial interaction and intensification of the heat transfer process due to the application of excess pressure. Based on the data obtained, it was found that during crystallization under excessive pressure there is a supercooling effect that reduces the casting solidification time. The use of the SPH method for modeling foundry processes has shown a high level of reliability and requires further development

Predicting the crack path in a wedge under a concentrated tensile force by means of variational principle

Variational principle of brittle fracture mechanics is employed to predict the crack path in an infinite wedge under a concentrated tensile force. The weight function in basic equation of variational problem is assumed to be proportional to the maximum strain in the uncracked wedge. Obtained equation for solving the variational problem allowed predicting the crack path in general. The predicted crack path is in agreement with experimental results obtained in the case of the truncated wedge

Crystallographic parameters in geometrically and topologically close-packed superstructures

The structures of stoichiometric compositions AB, A2B, and A3B for structures, B19, L10 ,L12 , D019 , D022 , D023 , D024 , A15, C14, C15 and C36 have been investigated based on the analysis of diagrams in coordinates of space-filling coefficients [psi] on superstructural compression [delta][omega]/[omega]. On the basis of the analysis of the abovementioned diagrams, the equation [psi]=f0+f1([delta][omega]/[omega]) has been obtained, and coefficients f0 and f1 of the equation for the investigated structures have been determined. It has been established that values of coefficients f0 and f1 for Laves phases have higher values than for all other compounds

STUDY OF GROUND PORK THAWING DYNAMICS USING MAGNETIC RESONANCE IMAGING

Visualization of changes in shape and size of the frozen residue during the thawing of ground pork is implemented using magnetic resonance imaging. A technique has been developed to study the displacement of thawing front line without damage to integrity of the object being thawed. It has been established that the melting of bound water crystals outran the melting of free water crystals in meat. A mathematical model that adequately describes the experimental data obtained in the analysis of tomograms is proposed. Tomograms are an important information source for studying the patterns of heat and mass transfer during the thawing of frozen foods.Visualization of changes in shape and size of the frozen residue during the thawing of ground pork is implemented using magnetic resonance imaging. A technique has been developed to study the displacement of thawing front line without damage to integrity of the object being thawed. It has been established that the melting of bound water crystals outran the melting of free water crystals in meat. A mathematical model that adequately describes the experimental data obtained in the analysis of tomograms is proposed. Tomograms are an important information source for studying the patterns of heat and mass transfer during the thawing of frozen foods

Selection of Temperature regimes for conditioning and flotation of diamond-bearing kimberlite with compound collectors

The condition for stable fixation of a collector on the surface of diamonds and their flotation is the use of collectors of the optimal fractional composition and the choice of the optimum temperature regime of the process. To determine the parameters of the diamond flotation regime, the regularities of the phase transitions of asphaltene-tar fractions at increasing temperature and diluting F-5 with technical diesel fraction were established. It was demonstrated that increasing the collector temperature leads to the transfer of asphaltenetar fractions to a dissolved and finely dispersed state. To an even greater extent, dissolving asphaltene-tar fractions is facilitated by the addition of medium- and low-molecular weight fractions of oil, for instance, a technical diesel fraction. It was revealed that the KM-10, KM-14, and KM-18 reagents, being compounds of F-5 fuel oil with technical diesel fraction (10–18 % DF), were characterized by optimal viscosity and ability to displace aqueous phase from a diamond surface, thus ensuring stable hydrophobization and high floatability of diamonds. The optimal temperature regime has been selected, which involved maintaining the temperature at the stage of conditioning with the collector at +30–40 °С, at which the maximum selective fixation of compound collectors on the diamond surface, characterized by the value of the limiting wetting angle, was achieved. The flotation tests have confirmed that the best results are achieved at a temperature of +30–40 °С at the conditioning stage and +14–24 °С at the flotation stage. At +24 °С, the best results were obtained for the relatively less diluted KM-10 and KM-14 fuel oils obtained by diluting F-5 fuel oil with a technical diesel fraction at the diluent volume fractions of 10 and 14 %. The diamond recovery achieved in the flotation tests was 3.8–4.5 % higher than when using the traditional collector, F-5 fuel oil. At +14 °С, the highly diluted fuel oil, KM-18 with a volume fraction of 18 % of the technical diesel fraction, demonstrated better collecting abilities. The optimal compositions of the collector and the regimes of feed preparation and flotation were tested at a foam separation unit. The tests showed that it is possible to increase diamond recovery into concentrate by 2.3–4.5 %. The recommendations are provided on the use of thermal conditioning in the foam separation cycle and maintaining the conditioning medium temperature at +30–40 °С and the foam separation temperature at +14–24 °С

Data gathering, surveillance and human rights: recasting the debate

The nature and depth of internet surveillance has been revealed to be very different from what had previously been publically acknowledged or politically debated. There are critical ways in which the current debate is miscast, misleading and confused. Privacy is portrayed as an individual right, in opposition to a collective need for security. Data gathering and surveillance are portrayed as having an impact only on this individual right to privacy, rather than on a broad spectrum of rights, including freedom of expression, of assembly and association, the prohibition of discrimination and more. The gathering and surveillance of ‘content’ is intrinsically more intrusive than that of ‘communications’ data or ‘metadata’. The impact of data gathering and surveillance is often portrayed as happening only at when data are examined by humans rather than when gathered, or when examined algorithmically. Commercial and governmental data gathering and surveillance are treated as separate and different, rather than intrinsically and inextricably linked. This miscasting has critical implications. When the debate is recast taking into account these misunderstandings, the bar for the justification of surveillance is raised and a new balance needs to be found, in political debate, in law, and in decision-making on the ground