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EN
In present paper we show results of ball-on-disk wear experiment of MoS2 film deposited on Ti6Al4V substrate. The ball material is aluminium oxide. The tests are performed for different surrounding temperature conditions: 20°C, 200°C and 350°C. It is shown that depth of the wear groove increases with increasing surrounding temperature. A finite element modelling approach is next developed to mimic the experimental observations of ball-on-disk wear process. It is based on the assumption of steady state condition developed during short time scale at contact region. The steady state results can next be applied to long time scale in which wear process is numerically simulated. Model results are compared with experimentally obtained wear groove and show satisfactory agreement.
PL
Artykuł prezentuje wyniki testu zużycia powłoki samosmarującej MoS2 nałożonej na podłoże wykonane z materiału Ti6AI4V. Powłoka obciążona jest kulką szafirową w ruchu rotacyjnym. Badania wykonano w trzech różnych temperaturach otoczenia: 20°C, 200°C oraz 350°C. Wykazano, że głębokość rowka zużyciowego wzrasta wraz ze wzrostem temperatury otoczenia. Zaproponowano model metody elementów skończonych za pomocą którego zasymulowany został proces zużycia warstwy. Punktem wyjścia dla tej części pracy było założenie stanu ustalonego, powstającego w obszarze kontaktu pomiędzy kulą a warstwą. Warunki odpowiadające temu stanowi przyjęto do matematycznego opisu procesu zużycia z wykorzystaniem równań Archarda. Na zakończenie eksperymentalny profil zużycia porównany został z wynikami otrzymanymi metodą elementów skończonych.
EN
In this paper, an exact analytical solution for the motion of fractionalized second grade fluid flows moving over accelerating plate under the influence of slip has been obtained. A coupled system of partial differential equations representing the equation of motion has been re-written in terms of fractional derivatives form by using the Caputo fractional operator. The Discrete Laplace transform method has been employed for computing the expressions for the velocity field […] and the corresponding shear stress […]. The obtained solutions for the velocity field and the shear stress have been written in terms of Wright generalized hypergeometric function pqψ and are expressed as a sum of the slip contribution and the corresponding no-slip contribution. In addition, the solutions for a fractionalized, ordinary second grade fluid and Newtonian fluid in the absence of slip effect have also been obtained as special case. Finally, the effect of different physical parameters has been demonstrated through graphical illustrations.
EN
The problem of mixed convection flow of a heat generating/absorbing fluid in the presence existence of Lorentz forces in a vertical micro circular subjected to a periodic sinusoidal temperature change at the surface has been studied taking the first-order slip and jump effects into consideration. The research analysis is carried out by considering a fully developed parallel flow and steady periodic regime. The governing equations, together with the constraint equations which arise from the definition of mean velocity and temperature, are written in a dimensionless form and mapped into equations in the complex domain. One obtains two independent boundary value problems, which provide the mean value and the oscillating term of the velocity and temperature distributions. These boundary value problems are solved analytically. A parametric study of some of the physical parameters involved in the problem is conducted. The results of this research revealed that the magnetic field has a damping impact on the flow and results in decreases in fluid velocity for both air and water. Furthermore, the presence of the heat generation parameter is seen to enhance the temperature distribution and this is reflected as an increase in the magnitude of the oscillation dimensionless velocity, whereas in the presence of heat absorption a reversed trend occurs.
EN
Experimental and numerical study on the mechanical performance of curved steel–concrete composite box girders is reported in this research. First, this research establishes a theoretical model for curved composite girders with 11° of freedoms (DOFs) for each node. The DOFs include the longitudinal displacement, transverse displacement, deflection, torsion angle, warping angle, and interface biaxial slip between steel and concrete. Based on the virtual work theorem, the equilibrium function, the stiffness matrix, the node displacement matrix and the external load matrix are proposed for the curved composite girders using the FE spatial discretization. Second, the authors conduct an experimental program on three large-scale curved composite girders with various interface shear connectors and central angles. The comparison between the developed finite beam element, the elaborate FE model and the test results indicates the developed finite beam element has an adequate level of accuracy in predicting the deflection, the torsion angle and the axial strain distribution of test specimens. Third, based on the developed finite beam element model, the effect of initial curvature, number of diaphragms, and the interface connector stiffness on the curved composite girder is examined. The simulation results showed that the initial curvature significantly contributes to the displacement and stress of composite girders. Applying more diaphragms can notably reduce the distortion angle and distortion displacement. The interface shear connector stiffness has a significant influence on the curved composite girder. With the increasing shear connector stiffness, the displacement and stress of curved composite girders decrease notably. Based on the parametric analyses, it is recommended to limit the central angle of simply supported composite girder below 45°, to apply an adequate number of diaphragms, and to design curved composite girders as fully shear connection specimens.
5
Content available remote Evolution of Goss texture in an Al–Cu–Mg alloy during cold rolling
EN
Evolution of Goss texture in an Al–Cu–Mg alloy during cold rolling was investigated by three-dimensional orientation distribution functions, electron back-scattered diffraction and transmission electron microscopy. The results showed that with increasing reduction from 23.7 to 80%, Goss textures gradually transformed into Brass texture through the activation of sole {111}<110> slip systems. When rolling reduction further increased from 80 to 86.3%, Goss texture rather than Brass started to rotate towards Copper and S components. The formation of Copper and S textures at these high reductions was attributed to the activation of {110}<110> and {001}<110> non-octahedral slip systems.
EN
The stretching sheets with variable thickness may occur in engineering applications more frequently than a flat sheet. Due to its various applications, in the present analysis we considered a three dimensional unsteady MHD nanofluid flow over a stretching sheet with a variable wall thickness in a porous medium. The effects of radiation, viscous dissipation and slip boundary conditions are considered. Buongiorno’s model is incorporated to study the combined effects of thermophoresis and Brownian motion. The dimensionless governing equations are solved by using MATLAB bvp4c package. The impact of various important flow parameters is presented and analysed through graphs and tables. It is interesting to note that all the three boundary layer thicknesses are diminished by slip parameters. Further, the unsteady parameter decreases the hydromagnetic boundary layer thickness.
EN
An analytical solution of an MHD free convective thermal diffusive flow of a viscous, incompressible, electrically conducting and heat-absorbing fluid past a infinite vertical permeable porous plate in the presence of radiation and chemical reaction is presented. The flow is considered under the influence of a magnetic field applied normal to the flow. The plate is assumed to move with a constant velocity in the direction of fluid flow in slip flow regime, while free stream velocity is assumed to follow the exponentially increasing small perturbation law. The velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number distributions are derived and have shown through graphs and tables by using the simple perturbation technique.
EN
Hydromagnetic flow of water based nanofluids over a nonlinearly stretching sheet in the presence of velocity slip, temperature jump, magnetic field, nonlinear thermal radiation, thermophoresis and Brownian motion has been studied. The article focuses on Cu water nanofluid and Ag water nanofluid. The similarity transformation technique is adopted to reduce the governing nonlinear partial differential equations into nonlinear ordinary differential equations and then they are solved numerically utilizing the Nachistem – Swigert shooting method along with the fourth order Runge Kutta integration technique. The influence of physical parameters on the flow, temperature and nanoparticle volume fraction are presented through graphs. Also the values of the skin friction coefficient at the wall and nondimensional rate of heat transfer are given in a tabular form. A comparative study with previous published results is also made.
9
Content available remote Odporność na poślizg posadzek
EN
In the present study, we have investigated entropy generation on a magnetohydrodynamic fluid flow and heat transfer over a stretching cylinder with a porous medium in slip flow regime. A uniform heat source and radiation is also considered. Similarity transformation has been applied for making an ordinary differential equation from nonlinear governing partial differential equations. The numerical solution for the set of nonlinear ordinary differential equations has been obtained by using the fourth-order Runge-Kutta scheme together with the shooting method. The effects of pertinent parameters such as the magnetic field parameter, permeability parameter, slip parameter, Prandtl number and radiation parameter on the fluid velocity distribution, temperature distribution, entropy generation and Bejan number are discussed graphically.
EN
The paper presents research program of bond between glass fiber reinforced polymer bars and concrete in reference to the steel bars. Bond between the reinforcement and concrete is a crucial parameter governing a behaviour of reinforced concrete members and transferring of the internal forces from concrete to the reinforcement. The use of FRP bars as an equivalent reinforcement to steel in concrete structures has increased in recent years. The FRP bars are very different from steel, mainly due to much lower elasticity modulus and their anisotropic structure. Good performance of FRP reinforced concrete requires sufficient interfacial bond between bars and concrete. However, there are no specific standards referring to the surface preparation of these bars, that leads to variable bond behaviour of the composite reinforcement to the concrete. The objective of the study was to investigate the influence of variable parameters on the bond behaviour to concrete. The experimental program consisted of eighteen beam bond specimens varying in: bar diameter (12mm, 16mm, 18mm) and type of reinforcement (GFRP sand – coated and steel bars). Although the GFRP bars indicated good bond behaviour to concrete, the average bond strength was slightly lower than that of steel reinforcement of 16mm and 18 mm, while it was higher for the GFRP bars of 12mm diameter.
12
Content available remote System przeciwpoślizgowy MGS3 Knorr-Bremse
PL
Poniższa praca porusza zagadnienie ewolucji systemów przeciwpoślizgowych, opracowane przez firmę Knorr-Bremse i przeznaczone dla różnego typu pojazdów szynowych na przestrzeni ostatnich kilkudziesięciu lat. Pierwsza część dotyczy wprowadzenia w zagadnienie poślizgu na styku koło-szyna w pojazdach szynowych wraz zjego skutkami. Przedstawione zostają główne wymagania wynikające z norm, które system przeciwpoślizgowy powinien spełniać. Następnie przechodzimy do systemu przeciwpoślizgowego MGS2 (drugiej generacji) - powszechnie stosowanego w pojazdach szynowych na całym świecie, zasadę jego działania oraz kluczowe zagadnienia brane pod uwagę przy zastosowaniu systemu w różnych typach pojazdów szynowych. Ostatnia część wprowadza w system MGS3 - najnowszą, trzecią generację systemu przeciwpoślizgowego.
EN
The following paper deals with the evolution of the Knorr-Bremse anti-skid systems designed for various types of rail vehicles over the past several decades. The first part introduces phenomenon of slip on wheel-rail contact point in railway vehicles and shows its consequences. The main requirements for wheelspin protection system implicated by several leaflets have been listed. Afterwards document moves on to MGS2 system (second generation) - commonly used in railway vehicles over the whole world. The principle of its operation and main key issues being considered during application in various types of vehicles have been described. The last part introduces MGS3 system-the newest, third generation of wheelspin protection system.
EN
An analysis is presented to describe the hydromagnetic mixed convection flow of an electrically conducting micropolar fluid past a vertical plate through a porous medium with radiation and slip flow regime. A uniform magnetic field has been considered in the study which absorbs the micropolar fluid with a varying suction velocity and acts perpendicular to the porous surface of the above plate. The governing non-linear partial differential equations have been transformed into linear partial differential equations, which are solved numerically by applying the explicit finite difference method. The numerical results are presented graphically in the form of velocity, micro-rotation, concentration and temperature profiles, the skin-friction coefficient, the couple stress coefficient, the rate of heat and mass transfers at the wall for different material parameters.
PL
Sprawdzono, czy badanie równowagi na platformie dynamometrycznej pozwoli na różnicowanie wyników badań w grupie osób młodszych i starszych, użytkujących obuwie ochronne o różnej konstrukcji. Wykazano, że noszenie obuwia ochronnego z cholewką i usztywnieniem wokół stawu skokowo-goleniowego wpływa na poprawę równowagi statycznej i dynamicznej u osób starszych.
EN
It was determined whether balance tests conducted on a dynamometric platform reveal differences between younger and older subjects wearing protective footwear differing in terms of shoe collar height and heel support. It was showed that the protective footwear with a high collar and ankle support improved both static and dynamic balance in older persons.
EN
In this study, the influence of temperature and wall slip conditions on the unsteady flow of a viscous, incompressible and electrically conducting nanofluid squeezed between two parallel disks in the presence of an applied magnetic field is investigated numerically. Using the similarity transformation, the governing coupled partial differential equations are transformed into similarity non-linear ordinary differential equations which are solved numerically using the Nachtsheim and Swigert shooting iteration technique together with the sixth order Runge-Kutta integration scheme. The effects of various emerging parameters on the flow characteristics are determined and discussed in detail. To check the reliability of the method, the numerical results for the skin friction coefficient and Nusselt number in the absence of slip conditions are compared with the results reported by the predecessors and an excellent agreement is observed between the two sets of results.
17
Content available remote Simulation model of wheel slip and slide protection systems for rail vehicles
EN
A simplified model of a rail vehicle - electric locomotive, with particular emphasis on wheelrail cooperation model, is presented. The principles of detecting the slip and algorithms that detect and eliminate the slip, both during acceleration and braking using dump valves are presented. Two anti-slip system simulation models, implemented in Matlab Simulink are described taking into account each subsystem model. The following models of hardware and software subsystems are described: the rotational speed sensors, the dumping valves and the subsystem determining the reference speed. The study program, simulation results, analysis and conclusions are presented.
PL
Przedstawiono uproszczony model pojazdu szynowego – lokomotywy elektrycznej, ze szczególnym uwzględnieniem modelu współpracy koła z szyną. Zaprezentowano zasady wykrywania poślizgu oraz opisano algorytmy wykrywania i likwidacji poślizgu, zarówno przy rozruchu, jak i przy hamowaniu z udziałem zaworów upustowych. Opisano modele symulacyjne obu układów przeciwpoślizgowych zaimplementowane w środowisku Matlab Simulink® z uwzględnieniem modeli poszczególnych podsystemów. Nakreślono modele podsystemów sprzętowych: model czujników obrotowo-impulsowych i zaworów upustowych oraz modele podsystemów programowych: podsystemu wyznaczania prędkości referencyjnej. Opisano program prób i badań obu układów. Przedstawiono wyniki badań symulacyjnych oraz analizę eksperymentów symulacyjnych wraz z wnioskami.
PL
W artykule omówiony został wpływ drgań drogowych na propagację wzdłuż czynnej powierzchni poślizgu i stateczność nasypów na terenach osuwiskowych. Układ warstw geologicznych wraz z ich zawodnieniem oraz gęsta sieć zabudowy, z liczną infrastruktury drogową przecinającą zbocza i naruszającą naturalny odpływ wód opadowych zwiększa ryzyko powstania ruchów masowych. Wystąpienie czynnego osuwiska wzdłuż konstrukcji nasypu drogowego wiąże się z awarią nawierzchni. Powoduje to konieczność wprowadzenia ograniczenia w prędkościach poruszających się pojazdów i znaczne utrudnienia w transporcie samochodowym. Zmiana częstotliwości wystąpienia obciążenia w może wpływać na propagację deformacji wzdłuż czynnej powierzchni poślizgu. Wskaźnik stateczności od obciążeń zmiennych, wyznaczono w oparciu o metodę względnego naprężenia stycznego. Obliczenia wykonano w programie MIDAS GTS NX®. Rezultaty obliczeń posłużyły do sformułowania wstępnego wniosku, o wpływie częstotliwości obciążenia na zmianę dynamicznego wskaźnika stateczności.
EN
Paper discussed the influence of road vibrations on propagation deformations along the active slip surface and embankment stability in landslide areas. The layout of the geotechnical layers with their saturation and a dense network buildings with a large count of infrastructure of road crossing slopes and detrimental to the natural drainage of rain water increases the risk of mass movements. The occurrence of active landslides along the road embankment construction is associated with the failure of the road surface. This makes it necessary introduction of restrictions on speed moving vehicles, and causes significant difficulties in road transport. Changing the frequency of the load can affect the propagation of active deformation along the slip surface. Index of stability coming from variables loads were determined based on the method of relative shear stress. The calculations were made in the program MIDAS GTS NX®. The results of the calculations used to the provisional conclusion on the impact of the frequency of load change on the dynamic indicator of stability.
EN
The aim of this paper is to present an assessment of the slip influence on the deflection of the steel plate-concrete composite beams, which are a new type of a design concept. The proposed method is based on the procedure included in the PN-EN 1992-1-1, which has been modified with taking into consideration interface slip. The theoretical analysis was verified by experimental studies.
PL
Konstrukcje zespolone od wielu lat z sukcesem są stosowane w budownictwie, a ich ciągły rozwój wynika z racjonalnego wykorzystania cech podstawowych materiałów stosowanych w budownictwie – betonu i stali. Ciągłe poszukiwania coraz to lepszych rozwiązań doprowadziły do powstania nowej koncepcji konstrukcyjnej – belek zespolonych typu stalowa blacha-beton. Wywodzi się ona z klasycznych konstrukcji zespolonych, ale czerpie również inspirację z metod wzmacniania żelbetowych belek za pomocą przyklejanych stalowych płaskowników. Pomysł nowego rozwiązania konstrukcyjnego zakłada zastąpienie części stalowej klasycznej konstrukcji zespolonej, która najczęściej była konstruowana w formie dwuteownika lub blachownicy, przez stalową blachę zespoloną z betonem za pomocą łączników (SPCC – steel plate-concrete composite). Przyczepność między tymi częściami składowymi belki zapewniają łączniki wiotkie w postaci sworzni. Badania doświadczalne konstrukcji zespolonych typu stalowa blacha-beton wykazały, że zastosowanie procedur zaproponowanych w normach nie pozwala na poprawne obliczenie ugięć tego typu konstrukcji. Wynika to z hybrydowego charakteru pracy tego typu elementów, które łączą cechy typowych konstrukcji żelbetowych i zespolonych. Niedoszacowanie ugięć spowodowane jest w głównej mierze nieuwzględnieniem podatności łączników wiotkich, co powoduje pominięcie wpływu poślizgu w płaszczyźnie zespolenia na sztywność elementu, a w konsekwencji na ugięcia.
PL
W artykule omówiono kontakt styczny dla walców parabolicznych. Przedstawiono rozwiązanie kontaktu stycznego z uwzględnieniem częściowych poślizgów dla znanego rozkładu naprężeń normalnych i znanej wielkości strefy styku. Prezentowane podejście jest odmienne, niż w rozwiązaniu klasycznym, w którym stosuje się teorię Hertza. Problem częściowych poślizgów sprowadza się do równań całkowych rozwiązywanych numerycznie. Przedstawione wyniki są porównywalne z klasycznym rozwiązaniem dla styku gładkich walców parabolicznych.
EN
This paper discusses tangential contact between rough parabolic cylinders. It provides a general solution to the problem of tangential contact, taking into account partial slip for a known distribution of normal stress and a known contact area. The approach differs from the classical solution, in which the Hertz theory is used. The partial slip problem was reduced to integral equations solved numerically. The results are similar to those of the classical solution for smooth parabolic cylinders.
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