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Prospects of Decreasing Power Losses in a Hydrostatic Thrust Bearing
PublikacjaIn numerous machines, axial load is carried by tilting pad thrust bearings known since the beginning of 20th century. These bearings are commonly bath lubricated, which is simple, does not require any additional pumps, and, due to this, such systems are highly reliable. In a contemporary technology, however, minimization of friction losses became an important goal of machinery improvement. Calculations based on elementary rules...
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INFLUENCE OF TIME ON THE BEARING CAPACITY OF PRECAST PILES
PublikacjaOne of the most popular types of foundations in layered subsoil with very differentiated soil shear strengths are precast piles. One of the reasons is a fact that we can well control the driving process during the installation of these piles. The principles of the assessment of bearing capacity and settlements of the piles given by Eurocode 7, concentrate on two main methods, i.e. Static Pile Load Tests (SPLT) and Dynamic Driving...
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Use of Neural Networks in Diagnostics of Rolling-Element Bearing of the Induction Motor
PublikacjaBearing defect is statistically the most frequent cause of an induction motor fault. The research described in the paper utilized the phenomenon of the current change in the induction motor with bearing defect. Methods based on the analysis of the supplying current are particularly useful when it is impossible to install diagnostic devices directly on the motor. The presented method of rolling-element bearing diagnostics used indirect...
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Experimental comparison of the transition speed of a hydrodynamic journal bearing lubricated with oil and magnetorheological fluid
PublikacjaA journal bearing test bench is used to find the transition speed between the hydrodynamic and mixed lubrication regimes for a modified magnetorheological (MR) fluid. It is shown that the transition speed of the bearing can be reduced by applying a local magnetic field near minimum film when it is lubricated with the MR fluid, and that this will only marginally increase friction. The lubricating performance of the MR fluid is compared...
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ANALYSIS OF BRACE STIFFNESS INFLUENCE ON STABILITY OF THE TRUSS
PublikacjaThe paper is devoted to the numerical and experimental research of stability of a truss with side elastic supports at the top chord. The structure is a model of a real roof truss scaled by factor ¼. The linear buckling analysis and non-linear static analysis were carried out. The buckling length factor for the compressed top chord was calculated and the limit load for the imperfect truss shell model with respect to brace stiffness...
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Reducing common mode voltage and bearing currents in quasi - resonant DC - link inverter
PublikacjaIn the paper, a concept of separation of an inverter-fed induction motor drive from its mains supply by two transistor switches inserted in the dc-link circuit is reexamined based on the proposed parallel quasi-resonant dc-link inverter (PQRDCLI). The objective of the paper is to show an advantage of the proposed topology in limiting high frequency common mode voltage and bearing currents. In the laboratory setup, an induction...
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Running characteristics of aerodynamic bearing with self-lifting capability at low rotational speed
PublikacjaAn aerodynamic journal bearing that is capable of self-generating squeeze-film pressure is presented and its dynamic characteristics investigated numerically and experimentally. A numerical method based on a time marching static model was applied to assess the orbit trajectory path of the rotor upon a perturbation. Experimental results were obtained to validate the effect of the self- generated squeeze-film pressure on the stability...
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ANALYSIS OF THE LOAD-CARRYING CAPACITY OF A HYDRODYNAMIC WATER-LUBRICATED BEARING IN A HYDROELECTRIC POwER PLANT
PublikacjaThe paper presents an analysis of the load-carrying capacity of a historic hydrodynamic water-lubricated radial bearing of an unconventional segment design installed in the Braniewo Hydroelectric Power Plant. The aim of the calculations was to determine whether the bearing operates in the conditions of hydrodynamic or mixed lubrication, as well as to establish the optimal geometry of the axial grooves allowing for the highest load-carrying...
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Bearing capacity of working platform using distinct layout optimization method
PublikacjaBearing capacity of the working platforms from sandy soil resting on NC and OC clays was analyzed using LimitState GEO program. Different failure modes are considered using distinct layout optimization (DLO) method, which forms the upper bound solution of limit state analysis. Different mechanisms of failure were observed as a function of the platform thickness, angle of internal friction of the platform material and undrained...
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Current-based higher-order spectral covariance as a bearing diagnostic feature for induction motors
PublikacjaConducting the diagnosis of induction motors remotely by analyzing the supply current is an attractive prospect with the lack of access to the engine. Currently, there is no solution, based on analysis of the current, the credibility of which would allow its use in industry. The statistics of bearing failures in induction motors indicate that they constitute more than 40% of induction motor damage, therefore, bearing diagnosis...
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Effect of manufacturing errors of the pad sliding surface on the performance of the hydrodynamic thrust bearing
PublikacjaIn the present study, investigation of the effect of manufacturing errors on the performance of large tilting pad thrust bearings has been performed, following a CFD-based Thermohydrodynamic analysis of a single pad. A 3D model has been generated, including the pad, the lubricant film and the corresponding part of the collar. The pad has been assumed to be deformed about the pivot point, due to thrust loading. Manufacturing errors...
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THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THIN-WALLED BEARING SHELL’S DESIGN PARAMETERS AND ASSEMBLY CONDITIONS ON THE HOLDING TORQUE INSIDE A HOUSING BORE OF A CONNECTING ROD
PublikacjaThe aim of the work was the experimental and theoretical evaluation of the influence of the most important parameters determining the holding torque of a thin-walled bearing shell inside a housing bore of a connecting rod. The main investigated parameters were defned by authors experience in this feld. In the frst stage of research, a special test stand was designed in order to allow measuring the real values of the friction torque...
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Analysis of the influence of geometrical imperfections on the equivalent load stabilizing roof truss with lateral bracing system
PublikacjaThe paper is focused on the numerical analysis of the stability and load bearing capacity of a flat steel truss. The structure was supported by elastic lateral braces. The translational and rotational brace stiffness was taken into account. The linear buckling analysis were performed for the beam and shell model of the truss. The nonlinear static analysis were conducted for the structure initial geometric imperfections. As a result...
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STABILITY ANALYSIS OF A TRUSS WITH SLOPING ELASTIC BRACES
PublikacjaSteel trusses have a much greater strength and stiffness in their plane than out of their plane, and therefore should be braced against lateral deflection and twisting. Such elements like purlins apart from bearing vertical load are part of bracing that stabilize roof trusses against distortional buckling. The stability of trusses with elastic bracing was investigated in an experimental research. Braces situated at some angle measured...
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Common-Mode Voltage and Bearing Currents in PWM Inverters: Causes, Effects and Prevention
PublikacjaIn modern induction motor drives an increase of transistors' switching frequency and a decrease of switching times are the sources of some serious problems. The high dv/dt and the common mode voltage generated by the inverter PWM control results in the appearances of bearing currents, shaft voltages, motor terminal overvoltages, the decrease of motor efficiency, and electromagnetic interference. The aspects of common mode (CM)...
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Improvement of the thrust bearing calculation considering the convectional heating within the space between the pads
PublikacjaA modern thrust bearing calculation tool should consider not only the oil film between pad and rotating collar but also the space between the pads. The oil flow in the space has a significant influence on the oil film inlet temperature, the convectional cooling of pad and collar and should be included in the bearing calculation methods. The authors use a tool developed at Clausthal University of Technology in cooperation with the...
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Application of the Optimization Methods to the Search of Marine Propulsion Shafting Global Equilibrium in Running Condition
PublikacjaFull film hydrodynamic lubrication of marine propulsion shafting journal bearings in running condition is discussed. Considerable computational difficulties in non-linear determining the quasi-static equilibrium of the shafting are highlighted. The approach using two optimization methods (the particle swarm method and the interior point method) in combination with the specially developed relaxation technique is proposed to overcome...
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The buckling analysis of a cold-formed steel C-sectional column resting on an elastic foundation
PublikacjaThe paper is focused on stability analysis of different models of steel cold-formed C-section column. The analysed element may be applied as a primary load-bearing member in steel trusses or silo columns. The column can be used as a support for a wall of roof plates made of corrugated sheets. The wall sheeting that restrains the column against buckling may be considered as an elastic foundation. Due to the design solutions the...
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Motor bearing diagnostics performed by means of laser vibrometer
PublikacjaDamage of bearings is the most common cause of failures in squirrel-cage induction motors. That is why the issues connected with diagnostics of bearings are so important. The equipment employed for bearing diagnostics usually makes use of vibrations as the criterion for technical condition of the bearings. This paper presents exemplary results of the research conducted on bearings with artificially introduced damage. A scanning...
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Bearing capacity of the working platform with kinematic method
PublikacjaBearing capacity of the working platform for heavy tracks was analysed using Distinct Layout Optimization (DLO) method. The platform layer constructed from cohesionless soils is resting on weak cohesive subgrade. Different thickness of the platform, its effective angle of internal friction and undrained shear strength of the soft soil were taken into consideration. Kinematic method permits different failure mechanisms to be analyzed....
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Hydrogen evolution reaction catalyzed by Co-based metal-organic frameworks and their derivatives
PublikacjaIn this study, Co-bearing Metal-Organic Frameworks (MOFs) are grown via a facile solvothermal process on the surface of two kinds of conductive substrates – titanium dioxide nanotubes (TiO2NT) and fluorine-doped tin oxide (FTO) glass and tested as electrodes in the electrochemical hydrogen evolution reaction (HER). The materials derived from three organic linkers - terephthalic acid (Co-BDC), 2-aminoterephthalic acid (Co-BDCNH2),...
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Search for the most useful geometry of an acoustic journal bearing
PublikacjaComputer simulations of a number of journal bearing’s geometries utilising acoustic levitation were carried out. The choice of the best geometry depended on the ability of a deformed shape, created by piezo-electric elements, to facilitate squeeze film ultrasonic levitation, and also to create three evenly distributed diverging aerodynamic gaps. Deformations of analysed variants of the bearing’s shape were generated by numerical...
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Estimation of Screw Displacement Pile-Bearing Capacity Based on Drilling Resistances
PublikacjaThis article presents an engineering, empiricalmethod of estimating the bearing capacity and settlementcharacteristics Q-s of screw displacement piles andcolumns, based on soil resistance encountered during thedrilling to form piles/columns in the ground. The methodwas developed on the basis of correlation analyses of thetest results of 24 piles made during the “DPDT-Auger”research project (Krasiński et al., 2022a). In the proposedmethod,...
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Biocompatibility and Bioactivity of Load-Bearing Metallic Implants
PublikacjaThe main objective of here presented research is to develop the titanium (Ti) alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants, e.g. hip joint and knee joint endoprosthesis. The development of such materials is performed through: modeling the material behaviour in biological environment in long time and developing of new procedures for such evaluation;...
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Comparison of induction motor bearing diagnostic test results through vibration and stator current measurement
PublikacjaThe paper discusses results of tests performed by authors, related to the angine bearings diagnostic using vibration and stator current measurements. The paper contains the description of an automatic measurement system, developed for measurement of those harmonics and processing that to obtain bearing diagnostic information. System was tested on objects with intentionally made defects in bearings, results of this test was also...
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Impact of Spatial Noise Correlation on Bearing Accuracy in DIFAR Systems
PublikacjaDIFAR type underwater passive systems are one of the more commonly used tools for detecting submarines. At the design stage, which usually uses computer simulations, it is necessary to generate acoustic noise of the sea. It has been shown that correlating noise significantly reduces these errors compared to the assumption that noise is uncorrelated. In addition, bearing errors have been shown to be the same in systems with a commonly...
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Evaluation of expanded uncertainty of instantaneous power measurement in a bearing diagnostic system.
PublikacjaThe paper presents the issues concerning the estimation of the expanded uncertainty in the system for the diagnosis of rolling bearings, consisting of transducers: voltage and current voltage, which is used for diagnostic bearing motors method based on the measurement and analysis of the instantaneous power signal consumed by the induction motor. It presents the methodology for assessing the measurement uncertainty and presents...
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Shear fracture of longitudinally reinforced concrete beams under bending using Digital Image Correlation and FE simulations with concrete micro-structure based on X-ray micro-computed tomography images
PublikacjaThe paper presents experimental and numerical investigations of the shear fracture in rectangular concrete beams longitudinally reinforced with steel or basalt bar under quasi-static three point bending. Shear fracture process zone formation and development on the surface of beams was investigated by Digital Image Correlation (DIC) whereas thorough analyses of 3D material micro-structure, air voids, width and curvature of shear...
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The use of GFRP tubes as load-bearing jackets in concrete-composite columns
PublikacjaThe paper presents the fields of applications of polymer composites in building structures. The use of composite glass fibre tubes is discussed in more detail. The laboratory methods used to test the mechanical properties of these pipes are presented. An original research program is presented, including six concrete-filled glass fibre tubes. The cylinders and columns made in this way were tested for their axial load capacity. Conclusions...
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Influence of an applied bearing system on behaviour of multi-span footbridge
PublikacjaThe cycle overpass in Gdynia is a box structure over 300 metres long, 10-span. It was opened for bicycle traffic in the second half of 2013. At the end of its construction, there was failure due to excessive horizontal displacement of the system. A number of bearings exceeded the range of permissible transverse shifts thus it was necessary to temporarily protect the spans from slipping. The FEM analysis of the original solution...
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Centrally Pivoted Tilting Pad Thrust Bearing with Carbon-Based Coated Collar—Experimental Results of Low- and Medium-Speed Operation
PublikacjaExperimental results of the research on a tilting pad thrust bearing with symmetrical pad support in the conditions of high loads and low speeds are presented in the paper. As described in the literature review, experimental results of tilting pad bearings at low speed/high load regime and transient conditions are rare. Unusual material selection - steel pad against a DLC-type coating on the collar was utilized. Such material combination...
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EVALUATING THE INFLUENCE OF BENDING STRESS ON A 1H18N9 STEEL SHAFT WEAR PROCESS IN A WATER LUBRICATED SLIDING BEARING WITH A RUBBER BUSHING
PublikacjaThe issue of excessive wear of shaft journals co-working with a rubber bearing has been unexplained so far. Premature and sometimes very intensive wear of ship sliding bearings in water conditions is the reason for carry out very expensive and more frequent than expected repairs. The authors (E. Piątkowska, W. Litwin) made an attempt to find a case that influences the value of this wear described in the paper “Attempt at Evaluating...
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A facile approach to fabricate load-bearing porous polymer scaffolds for bone tissue engineering
PublikacjaBiodegradable porous scaffolds with oriented interconnected pores and high mechanical are load-bearing biomaterials for bone tissue engineering. Herein, we report a simple, non-toxic, and cost-effective method to fabricate high-strength porous biodegradable scaffolds, composed of a polymer matrix of polycaprolactone (PCL) and water-soluble poly (ethylene oxide) (PEO) as a sacrificial material by integrating annealing treatment,...
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Structural properties of foil bearings: a closed-form solution validated with finite element analysis
PublikacjaFluid film thickness in a compliant foil bearing is greatly influenced by the deflection of the bearing structure. Therefore, in order to properly model performance of a foil bearing, it is mandatory that the deflection of the compliant bearing structure due to the generated hydrodynamic pressure is determined accurately. This article proposes an easy-to-use two-dimensional model, which takes into account detailed geometry of the...
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Novel Nonlinear High Order Technologies for Damage Diagnosis of Complex Assets
PublikacjaFor the first time worldwide, innovative techniques, generic non-linear higher-order unnormalized cross-correlations of spectral moduli, for the diagnosis of complex assets, are proposed. The normalization of the proposed techniques is based on the absolute central moments, that have been proposed and widely investigated in mathematical works. The existing higher-order, crosscovariances of complex spectral components are not sufficiently...
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Evaluation of bearing and journal damage in MAN 9L40-54 engines installed on M/V STENA SCANDINAVICA ferry
PublikacjaThe following report was requested by Remontowa Shiprepair Yard (RSY) S.A. in Gdansk ´ (contract no. 4/2018/EX/U, dated 13.02.2018) and prepared based on the materials received from RSY, two on-board inspections and the participation of the contractors in three conferences with RSY representativesi. The goal of the analysis performed by the experts of Gdansk University of Technology was ´ to determine the character of the bearing...
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Chapter 2: Modelling and analysis of rotor with magnetic bearing system
PublikacjaThe paper is concerned with rotor magnetic bearing system modelling. Such system is a relatively complex electromechanical system and can be considered as typical mechatronic one. The port-based modelling of physical systems has been used to obtain discrete-continuous model of considered system. Proposed approach enables to obtain reduced low-order lumped parameter representation of the system including gyroscopic interactions....
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Selected problems of experimental investigation of dynamically loaded journal bearings
PublikacjaIn the paper some problems concerning relations between external bearing loadings and critical lining stresses are described for test stand with rotating load vector. According to the standard ISO 7905/1 this type of test stand, for dynamically loaded slide bearing, is recommended as a basic research unit for material testing in a complete bearing unit. The lining stress calculation results occurred being dependent on applied calculation...
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Experimental Research on Insufficient Water Lubrication of Marine Stern Tube Journal Bearing with Elastic Polymer Bush
PublikacjaWater-lubricated bearings with polymer bushes are steadily gaining popularity due to their advantages, including environmental friendliness, relatively simple construction and long-term operation. Nevertheless, in practice instances of damage to such bearings occur due to insufficient or absent flow of the lubricating agent. In this study, experimental tests established that elastic polymer bush bearing is capable of operating...
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Mathemathical model of radial passive magnetic bearing
PublikacjaIn the article mathematical radial model of passive magnetic bearings to ocean engineering units has been presented. The units application in underwater thrusters should increase propulsion systems durability and gives lower maintenance costs. The rotor of electric motor is hanging in magnetic field taken from radial passive magnetic bearings. However axial direction maintenance must be controlled with electromagnets and their...
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Experimental investigation into surface texture effect on journal bearings performance
PublikacjaThe aim of this study was to analyse the performance of journal bearings with specially created dimples on the sliding surface and operating under various conditions. The texture was created on the bearing surface that co-acted with the smooth journal; moreover, the variation of the textured surface of the journal mating with the smooth bearing was tested, and the results were compared to those obtained with the standard smooth...
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Experimental research on marine oil-lubricated stern tube bearing
PublikacjaBearings of propeller shafts are very crucial elements of the propulsion system of each of the ships. The safety of shipping depends on their durability and reliability. The new legal restrictions mean that today we are looking for environmentally friendly solutions. That is why water-lubricated bearings are becoming more and more popular. So, will oil-lubricated shaft bearings belong to the past? The bearing with a white metal...
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Tilting pad thrust bearing with novel material selection - experimental comparison of low and medium speed operation
PublikacjaThe advances in material engineering led to the development of hard carbon based coatings applied in numerous applications in order to prevent or minimize wear of the parts in contact. With Triondur® coatings, the bearing company Schaeffler has succeeded in halving the friction losses in the valve trains of passenger cars. The coatings are optimized for high abrasive wear protection and low sliding friction moments. Altogether...
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Fatigue resistance investigation of the IC engine MB11 bearings, working under conditions of dynamic unidirectional loadings
PublikacjaThe slide bearing material MB11 fatigue resistance has been investigated with the application of SMOK - test stand in which dynamic unidirectional loadings to the test bearing is generated. Slide bearing layer consists of the bronze MB11 ( Cu Pb22 Sn 3 ) sintered to the steel shell. Each of the tested bearing has been subject to the standard 20-hour test, under conditions of the full fluid lubrication. Methodology of the experiments,...
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Reliability model of slide bearings with particular attention given to lubricating oil
PublikacjaThe paper presents the slide bearing with circulating lubrication as a system of series three-element structure, where lubricating oil is the weakest link. In accordance with the Pierce statement that ''strength of chain is the strength of its weakest link'', a bearing reliability model has been developed. It allows to use the lubricating oil to evaluate the probability of correct working of the whole slide bearing, i.e. the reliability....
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Ecological bearing systems for water turbines – research and development at Gdansk University of Technology
PublikacjaIncreasing requirements for environmental protection make it necessary to introduce new materials and designs. Hydroelectric power plants operating in direct contact with water reservoirs and rivers are potentially endangering water cleanliness, hence they should also be modernized in the way minimizing the environmental hazards. A lot of progress in this field has been achieved in last decades, but still there is much work to...
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Mechanical and structural investigations of wings of selected insect species
PublikacjaThis paper presents research and measurements leading to obtaining the Young’s modulus of wing bearing structures of selected insect species. A small testing machine intended for three-point bending and equipped with instruments registering low forces was constructed for the needs of the experiment. The machine was used to perform numerous bending tests of wings of three species of insects (obtained from a breeding farm): Attacus...
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Application of the fluid–structure interaction technique for the analysis of hydrodynamic lubrication problems.
PublikacjaFluid–structure interaction technique seems to be one of the most promising possibilities for theoretical analysis of lubrication problems. It allows coupling of different physical fields in one computational task, taking into account the interaction between them. In this article, two sets of fluid–structure interaction analyses focusing on the bearing performance evaluation are presented. One analysis was applied to a water-lubricated...
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Influence of local bush wear on water lubricated sliding bearing load carrying capacity
PublikacjaOne of main problems concerning water-lubricated bearings is their durability. There are known cases of bearings with life time measured in decades, and some, whose refurbishment was necessary just days after start-up. Obtaining stable fluid film friction plays key role in the durability of these bearings. Unfortunately, their load-carrying capacity is limited due to water's low-viscosity. The conducted experimental...
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An electric ring thruster as auxiliary manoeuvring propulsion system for watercraft - construction analysis
PublikacjaThe reported project aimed at examining properties and purposefulness of use of modern electromagneticbearings for a screw propeller in a prototype version of a synchronous ring motor with rare earths magnets.Bearings of this type generate electromagnetic forces which keep the rotor in a state of levitation. Therotating machine with magnetic bearings can work in any environment which reveals diamagnetic properties(air, vacuum,...