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EN
Failure analysis of a laminated composite beam subjected to uniformly distributed load and thermal load is studied for different boundary conditions and fiber orientation angles, based on first ply failure load. Three different boundary conditions are studied: simply supported, fixed-fixed and fixed-free. The strength ratio is computed and compared for different failure theories. The effect of fiber orientation angle and aspect ratio on the strength ratio based on first ply failure load is presented in the paper. The strength ratio and transverse deflection are determined for Graphite/Epoxy and Glass/Epoxy composite and their hybrid combinations to find out the optimum hybrid composite beam with minimum weight, deflection and cost. The problem is solved in MATLAB platform. The mode of failure of the composite beam is determined by using maximum stress theory.
EN
In this paper, nanofluids were prepared based on gold nanorods in basic fluid, water, by single-stage chemical reduction and in different volume fractions and the used gold nanorods were synthesized by seed-mediated growth method in different dimensional ratios. The properties of the prepared nanoparticles, including crystalline size, aspect ratio, surface properties, nanoparticle purity, shape and morphology of nanostructures were investigated using x-ray diffraction, UV-vis spectroscopy, FT-IR, and transmitted electron microscopy. The effect of changing parameters of Nano rod dimensions, changes in Nano rod volume fraction in water and also the effect of temperature on the nanofluid thermal conductivity coefficient were investigated using transient hot wire method. The results showed that reducing the aspect ratio, increasing the volume fraction and increasing the temperature increase the thermal conductivity. In fact, results show that an increase in the nanorods aspect ratio with a constant volume fraction of 1:50 of gold in water nanorod and at room temperature leads to a decrease in the thermal conductivity of the nanofluid. Also, increasing the two parameters of volume fraction and temperature significantly increases the thermal conductivity coefficient.
EN
To transport of the air in the pipeline, an analytical model is developed that takes into account the gas velocity, its kinematic and dynamic characteristics - density, viscosity depending on the pressure in a given space of the pipeline. The analytical model makes it possible to calculate the coefficient of friction of gas transportation in the pipeline at intervals of the absolute pressure from 220 to 2 kPa and M < 1 Mach numbers, depending on the diameter and length of the pipeline and physical and technological characteristics of the gas. The K1* aspect ratio is proposed, which characterizes in time the ratio of the dynamic force of movement of gas to the static pressure related to the diameter of the pipeline. The coefficient of air friction was modeled according to the vacuum pressure as a parameter of density and air flow. Air flow was taken from 1.917·10-3 m 3/s to 44.5·10-3 m 3/s respectively, diameters from 0.030 to 0.070 m and Mach number was M = 0.005-0.13. At the vacuum and excess pressures with increasing of Reynolds number and decreasing of Mach number the gas friction coefficient increased linearly. According to the simulation results as the pressure loss and the diameter of the pipeline are increased the friction coefficient increased as well. Analogically, at the vacuum metric pressure when the pressure loss and the diameter of the pipeline are increased the friction coefficient increased. At the pipeline internal diameters of 22, 30, 36 mm accordingly for pressure losses from 2 to 14 kPa the coefficient of air friction varies from 0.006 to 54.527 respectively.
EN
The basic dimensions and the mass of common beech nuts and seeds from five nut batches, harvested from tree stands in northern Poland, were determined. Environmental conditions had a greater influence on seed plumpness than the age of tree stands. The results of measurements were analyzed statistically by analysis of variance, correlation analysis and linear regression analysis. Despite differences in their plumpness, nuts were characterized by nearly identical cross-sections which resembled an equilateral triangle. The thickness of nuts and seeds was highly correlated with their mass, and this information can facilitate seed husking and separation into mass categories. Before and after husking, seeds should be separated with the use of a mesh screen with longitudinal openings. Medium-sized (most numerous) seeds were separated into the following plumpness categories using a screen separator with ≠6 mm and ≠7 mm openings: 84% of moderately plump seeds, 3% of seeds with reduced plumpness, and 13% of plump seeds.
5
Content available remote Performance of hydrodynamic journal bearing operating under transient wear
EN
The paper deals with a theoretical study concerning the effect of transient wear on the performance of hydrodynamic journal bearing . The eccentricity ratios are considered 0.3, 0.6 and for varying wear depth from 0.1 to 0.5 for the analysis of purpose. The Reynolds equations governing the flow of lubricant in the clearance space of a hydrodynamic journal bearing system with varying wear depth has been numerically solved using Galerkin’s FEM. The regime is assumed to be isothermal. The positive pressure zone is established using Reynolds boundary condition through iteratively. The various performance parameters which include static, dynamic and stability terms of worn journal bearing are presented with respect to relative wear depth. The journal centre motion trajectories are also obtained by numerically integrated linear and non-linear equation of motion using fourth order Runga-Kutta method. For this a computer program in Matlab was developed based on analysis to draw the linear and non linear motion trajectories and in order to validate the developed program, the numerically simulated results computed from the present study are compared with the already published results in literature. For analysis purpose the initial values of velocities and displacement are taken as ¯˙X = ¯˙Z = 0:0 and ¯x and ¯z = 0:005. The results help in predicting bearing life for smooth operation.
EN
This paper is concerned with the mechanical response of a single-walled carbon nanotube. Euler-Bernoulli’s beam theory and Hamilton’s principle are employed to derive the set of governing differential equations. An efficient variational method is used to determine the solution of the problem and Legendre’s polynomials are used to define basis functions. Significance of using these polynomials is their orthonormal property as these shape functions convert mass and stiffness matrices either to zero or one. The impact of various parameters such as length, temperature and elastic medium on the buckling load is observed and the results are furnished in a uniform manner. The degree of accuracy of the obtained results is verified with the available literature, hence illustrates the validity of the applied method. Current findings show the usage of nanostructures in vast range of engineering applications. It is worth mentioning that completely new results are obtained that are in validation with the existing results reported in literature.
EN
Effects of structural parameters on the vibration of a tapered non-homogeneous rectangular plate with different combinations of boundary conditions are discussed. Tapering in the plate is assumed to be sinusoidal in the x-direction. Here, temperature variation and non-homogeneity in the plate material are also considered sinusoidal in the x-direction. The Rayleigh-Ritz method is used to calculate the frequency parameter for the first two modes of vibration for different values of the structural parameters, i.e. the taper parameter, thermal gradient, aspect ratio and non-homogeneity constant. Results are obtained for three boundary conditions, i.e. clamped boundary (C-C-C-C), simply supported boundary (SS-SS-SS-SS) and clamped-simply supported boundary (CSS-C-SS). Numerical values of the frequency parameter are given in a compact tabular form.
8
Content available Densification behaviour of carob powder
EN
The behaviour of carob (Ceratonia siliqua L.) powder relevant to its densification at low pressure was determined given different equipment aspect ratios (0.5, 1.0 and 1.5) and varying rates of deformation (5.5, 10 and 14.5 mm min-1). The effects of both parameters were examined through the analysis of variance and trends were fitted to observed mechanical responses using standard regression technique. Both aspect ratio and the time rate of deformation had highly significant effects on the material’s response to load. Strain rate and specific power requirement were power functions of the equipment’s aspect ratio, at all rates of deformation. These findings furnish insights on mechanical response in compressed food powders which are applicable in modelling related food handling and processing systems.
9
Content available remote Cyclic testing of steel frames infilled with concrete sandwich panels
EN
In-plane seismic behaviour of concrete sandwich panel-infilled steel frame (CSP-ISF) was experimentally and numerically investigated. Four large-scale, single bay and single story steel frame specimens were tested under reversed cyclic lateral loading. Three infilled frames with different aspect ratios along with one bare frame were considered. It was found that addition of sandwich panels leads to considerable increase in the lateral stiffness and strength, ductility, energy dissipation capacity as well as equivalent viscous damping ratio of the steel frames. Furthermore, the maximum shear capacity of CSP-ISF specimens was validated by analytical approaches which showed good agreement with experimental results. Based on the present experiments, structural performance levels required for Performance-based Analysis are also proposed for concrete sandwich panel used as infill walls. Finally, a numerical model is presented to analyze the nonlinear behaviour of CSP-ISFs.
EN
Buckling of thin-walled and load-bearing elements of a structure can have devastating consequences. Hence, buckling checks are an integral part of strength analysis of structures. The buckling problem of thin rectangular plates subjected to in-plane compressive and/or shear loading is of great importance in building, bridge, aerospace, marine, and shipbuilding industries. When buckling occurs, thin plates undergo large out-of-plane deflections, which in turn results in the development of large bending stresses and eventually complete failure of the structure. This paper deals with the buckling stability assessment of uniaxially-compressed plates with different support conditions within the framework of classical plate theory. The main objective of this research is to explore some uncovered aspects of buckling stability of plates by considering the effects of support conditions, aspect ratio, and slenderness ratio, which will consequently result in efficient design of such thin-walled structures. To this end, in addition to validation of the numerical simulation, some case studies have been performed in order to gain a better understanding of different aspects of buckling stability of such thin-walled structures.
EN
In this paper, a fused-silica transmission grating used as a three-port beam splitter is designed by using the rigorous coupled-wave analysis, which is based on the sandwiched grating structure at the wavelength of 800 nm under normal incidence. Firstly, it is feasible to realize such a grating with the prescribed grating duty cycle and grating period. Next, high efficiency can be also achieved for both TE and TM polarizations. Moreover, the aspect ratio of the grating depth to the ridge width can be improved, which is significant for practical applications. At last, the three-port beam splitter is designed with a covering layer on the surface, which can extend its life service.
12
Content available Thermal effect on damaged stay-cables
EN
Cables may suffer severe damage in cable-stayed bridges, leading to cable relaxation and tension loss. Such a damage effect merges in the sag augmentation or tension tightened by the thermal effect. This paper is intended to investigate the static response of damaged cables coupled with the thermal effect. With the introduction of three damage parameters such as damage position, damage degree and damage range as well as temperature parameter, the dimensionless governing equations for cables are derived and the numerical method is employed to solve the nonlinear equations. The static behavior of damaged cables due to the thermal coupling effect is analyzed, and the way to remove the thermal effect is given. It shows that the aspect ratio is the major factor is the deflection of the mid-span and horizontal force in the cable, whereas the angle inclination is the next important parameter. Cables with the natural length close to the chord distance reveal the highest sensitivity to temperature, whereas pre-tensioned and non-pre-tensioned cables are less sensitive to the thermal effect. It further demonstrates that with more damage included, the sensitive scope of the variation coefficient of the axial force with aspect ratio and temperature changes dramatically.
EN
The paper presents analyses of the mean wind pressure coefficient distribution on the surfaces of circular cylinders. The experiment was performed in a boundary layer wind tunnel in the Wind Engineering Laboratory in Cracow, Poland. Three models were examined in the wind tunnel. The influence of the aspect ratio and wind parameters (mean wind speed profile, turbulence intensity profile, power spectral density functions) on the mean wind pressure coefficient distribution and its standard deviation was considered during the tests.
PL
Zastosowanie laserowego skanera 3D pozwala na bezdotykowy pomiar i odwzorowanie powierzchni a następnie obliczenie współczynników charakteryzujących właściwości geometryczne. Dodatkową korzyścią z zastosowania bezdotykowego pomiaru geometrii za pomocą skanera 3D jest możliwość pomiaru produktów o delikatnej strukturze zewnętrznej i wrażliwych na uszkodzenia mechaniczne. Celem pracy było określenie podstawowych cech geometrycznych pieczywa typu "bułka ziarnista", wykonanie pomiarów pola powierzchni, objętości oraz określenie podstawowych jego właściwości fizycznych - masy i gęstości. Średnie pole powierzchni obliczone na podstawie modelu cyfrowego w przypadku gdy skanowany model bułki posiadał na swojej powierzchni otwory oraz gdy otwory w modelu zostały wypełnione nie różniły się istotnie. Istotne różnice wystąpiły gdy pole powierzchni i objętość bułek była obliczana ze wzorów. Obliczono również współczynniki kształtu dla badanej serii bułek.
EN
3D laser scanner application allows non-contact measurement and mapping of surfaces and calculation of the factors characterizing geometric features. An additional benefit of using noncontact measurement of geometry using the 3D scanner is the ability to measure the products of fine texture and sensitive to external mechanical damage. The aim of this paper was to determine the basic geometric features of grain bread rolls, the measurements of surface area and volume and determine its basic physical properties - mass and density. The average surface area calculated on the basis of a digital model in case when the scanned model of a bread roll had holes in its surface, and in case when the holes were filled in the model, did not differ significantly. Significant differences occurred when the surface area and volume of bread rolls was calculated from the formulas. The aspect ratios for the series of bread rolls were estimated.
EN
Three-dimensional dispersion of a passive solute in a couple stress fluid through a channel of rectangular cross section is studied using the generalized miscible dispersion theory of Gill and Sankarasubramanian (1970) and Doshi et al. (1978). The effects of couple stress on the velocity and thereby the convective and dispersion coefficients are discussed. The time-dependent dispersion coefficient and mean concentration distribution are computed and the results are represented graphically for various values of the aspect ratio and couple-stress.
16
Content available remote Informacyjny opis wpływu wirującego pola magnetycznego na układ dyspersyjny
PL
W pracy przedstawiono wyniki badań wpływu wirującego pola magnetycznego na kształt pęcherzy wznoszących się w różnego typu płynach. Zaprezentowano nowe podejście do opisu zmian kształtu pęcherzy, sformułowane na podstawie entropii informacji.
EN
A deformation of air bubbles rising in liquids under he action of rotating magnetic field was studied. A new approach in description of bubbles aspect ratio by means of differential entropy is presented.
17
Content available remote Axially symmetric vibrations of finite composite poroelastic cylinders
EN
Axially symmetric vibrations of a finite composite poroelastic circular cylinder are investigated employing Biot's theory of wave propagation in poroelastic media. The composite poroelastic cylinder consists of two poroelastic cylinders of different materials bonded at the plane ends. Frequency equations for such vibrations are derived both for pervious and impervious surfaces. Let the finite composite poroelastic cylinder be homogeneous and isotropic and the boundaries free from stress. Non-dimensional phase velocity for propagating modes is computed as a function of ratio of length of cylinders in the absence of dissipation. The results are presented graphically for two types of composite poroelastic cylinders and then discussed. In general, the phase velocity of composite cylinder-I is higher than that of composite cylinder-II both for a pervious and an impervious surface.
EN
Masonry is a complex composite material with non-linear material properties, which make the numerical investigation of its structural behaviour a difficult task. In this paper, a micro non-linear model created using a general purpose finite element code, is discussed with respect to its ability to simulate the in-plane behaviour of unreinforced masonry walls. That is, the capability of model in predicting the cracking, crushing, and sliding phenomena, as well as the global-orthotropic behaviour of previously tested masonry walls are examined. The model is then used within a parametric study to investigate the effect of different aspect ratios, vertical and horizontal post-tensioning as well as the effect of head joints on the capacity of the masonry walls. It will be shown that, while enhancing the lateral in-plane strength of the masonry walls, vertical post-tensioning can also reduce their ductility. On the contrary, horizontal post-tensioning can cause a small reduction in the initial stiffness and yielding shear force of the masonry walls, but increases their integrity, thereby preventing them from sliding and shear failure. Furthermore, it will be shown that, in spite of having a significant influence on local behaviour, head joints do not influence the global behaviour of the masonry walls.
PL
Mur jest złożonym materiałem kompozytowym o nieliniowych właściwościach, które powodują to, że ich analiza numeryczna jest złożonym i trudnym zadaniem. W artykule przedstawiono nieliniowy mikro-model stworzony przy użyciu uniwersalnego kodu elementów skończonych służący symulacji zachowania się niewzmocnionego muru w jego płaszczyźnie. Zbadano zdolność modelu do przewidywania występowania takich zjawisk jak pękanie, kruszenie, poślizg, tak jak we wcześniejszych badaniach ortotropowego zachowania się murów. Następnie model użyty został do badań parametrycznych wpływu pionowego i poziomego sprężania oraz wpływu kotew czołowych na nośność murów.
EN
When a fluid flows through a pipe line, the velocity and temperature distribution across the pipe cross section is required to be determined in order to properly utilize the fluid and its associated energy in a process plant. In the present paper, a variational method has been used to determine this distribution in a pipeline of rectangular as well as square cross section under laminar condition. The mathematical equations have been developed describing the velocity and temperature distributions under two cases. In the first case, the heat flow rate is taken to be uniform along the axial direction and in the second case, the wall temperature has been taken to be uniform. In both the cases, the velocity and temperature distribution curves have been drawn from the mathematical equations derived. The distribution curves are presented for a variety of thermal boundary conditions around the periphery of the duct cross section.
PL
Stałe zapotrzebowanie na zminiaturyzowane i funkcjonalne urządzenia elektroniczne wymaga stosowania wysokozaawansowanych technik ich wytwarzania. Bezpośrednio wiąże się to z koniecznością miniaturyzacji obwodów płytek drukowanych. Największą trudność w wytwarzaniu wysokozaawansowanych płytek drukowanych stanowi metalizacja mikrootworów nieprzelotowych oraz otworów przelotowych o dużym współczynniku kształtu. Aby temu sprostać opracowana została technika osadzania miedzi przy zastosowaniu metody impulsowej.
EN
The still demand of miniaturized and much more functional electronic devices requires using of high-tech technologies of manufacturing. Directly it is connected with necessary to minimize of Printed Circuit Boards. The most difficulties in manufacturing of High-Tech Printed Circuit Boards create metallization process of blind microvias and high aspect ratio through holes. To match this, the technique of copper deposition with using of pulse method was elaborated.
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