The phenomenon of occurrence of a hydrodynamic oil film on the bearing system is analyzed. A theoretical model of the radial slide bearing system that takes into account the normal and static ...stresses as well as the deformations is proposed. The values of stress and deformation in the contact area are established. They are compared with the values obtained using the Hertz model. Moreover, the results of the analysis of the bearing system in thermodynamic equilibrium are presented. In this case, the journal and the bushing are separated by an oil layer.
In this paper, the reactive diffusion in Ni80C20r?Ti ternary system is discussed at 1173K. The diffusion couple was prepared and annealed for 100 h. The two intermetallic phases and two two-phase ...zones occurred, namely: Ti2Ni, TiNi, TiNi+Cr, and TiNi3+Cr. Based on the experimental results (molar fractions, thicknesses of the intermetallic phases), the intrinsic diffusion coefficients of all components in each phase were numerically approximated. The Wagner method was used in the pure intermetallic phases. In the two phase zones the approximation was based on the generalized Darken and Wagner methods. The presented methods allowed for determination of the effective diffusion coefficients in each presented phase.
In the present work, a performance of ASTM A439 Austenitic Ductile Iron type D5S at high temperature in the oxidizing environment was investigated. The obtained results revealed that exposure at ...temperatures 800?C, 850?C, and 900?C resulted in relatively high mass gain and an extensive oxide scale spallation from the samples? surfaces during cooling. However, the material exposed at 950?C revealed a better oxidation resistance and no oxide scale spallation. The material exposed at 1000?C showed the best oxidation resistance among the studied samples. The surfaces and cross-sectional investigation revealed that the material exposed at 950?C formed mostly Ni/Cr/Mn-mixed protective oxide scale and local formation of Fe-rich nodules. In comparison with the sample exposed at 1000?C, a smaller amount of Fe-rich nodules per area unit was observed and most of the surface was covered by Ni/Cr/Mn-mixed protective scale. The latter was explained by the change in the calculated diffusion coefficients in the alloy for Ni and Fe, namely up to 900?C the diffusion coefficient for Fe was much higher than for Ni, while above 900?C the diffusion coefficient for Ni becomes higher than for Fe. This phenomenon was correlated with a phase transformation from ?-Fe into ?-Fe resulting in the diffusion coefficient change.
Virus removal can be successfully achieved based on an electrostatic adsorption mechanism. The key requirement for this process is to develop filter materials that can be produced by low-cost ...technologies and are suitable in large-scale production for real applications. In this study, we report development of spray-dried alumina granules modified with copper (oxide) nanoparticles and critically assess the effect of copper oxidation state on virus removal capacity. Using plate-shaped alumina as a support material resulted in porous structure, which in turn ensured prolonged contact time of contaminated water with the material. Subsequently, copper (oxide) nanoparticles provided a large number of adsorption sites. Flow experiments revealed that copper(I) oxide and metallic copper were the active phases in virus removal and 99.9% of MS2 bacteriophages could be removed. However, almost no virus removal was observed in the presence of copper(II) oxide. Contrasting virus removal characteristics are associated with the different surface charge of copper species, as determined by zeta potential measurements.
The problem of damping torsional vibrations of the crankshaft of a multi-cylinder engine is very important from the point of view of the durability and operational reliability of the drive unit. Over ...the years, attempts have been made to eliminate these vibrations and the phenomena accompanying them using various methods. One of the methods that effectively increases the durability and reliability of the drive unit is the use of a torsional vibration damper. The torsional vibration damper is designed and selected individually for a given drive system. A well-selected damper reduces the amplitude of the torsional vibrations of the shaft in the entire operating speed range of the engine. This paper proposes a thermo-hydrodynamic model of a viscous torsional vibration damper that enables the determination of the correct operating temperature range of the damper. The input parameters for the model, in particular the angular velocities of the damper elements as well as the geometric and mass dimensions of the damper were determined on a test stand equipped with a six-cylinder diesel engine equipped with a factory torsional vibration damper. The damper surface operating temperatures used in model verification were measured with a laser pyrometer. The presented comparative analysis of the results obtained numerically (theoretically) and the results obtained experimentally allow us to conclude that the proposed damper model gives an appropriate approximation to reality and can be used in the process of selecting a damper for the drive unit.
Obtaining the best operating parameters of the internal combustion engine has focused the attention of designers and researchers since the first years of its creation. Initial research focused on ...increasing engine power and overall efficiency. As time passed, these aspirations became more sophisticated and began to concern other operating parameters of the drive unit. The basic problem, however, remained the improvement of filling the cylinder with the working medium. Turbocharger charging consists in using the energy of the exhaust gases to drive a turbine placed on a common shaft with a compressor supplying air under increased pressure to the cylinders. Over time, the turbocharger became one of the key elements and its technical condition began to play a key role in the operation and performance of modern drive units. Like every element, the turbocharger itself is not without its faults. This procedure is known among manufacturers who, when designing power units and their assemblies, pay special attention to the essence of turbocharger construction. Since it is impossible to predict all the phenomena accompanying a working turbocharger at the design stage, the authors of this paper conducted bench tests of a selected batch of turbochargers, focusing mainly on the vibration measurements of the turbocharger rotating assembly. At the same time, we present a dynamic model of the mentioned system based on the analyses resulting from the solutions of the equations of a numerical model. In order to give the research a practical aspect, the results of the theoretical research were compared with the results of bench tests. It has been shown that the basic problem is to guarantee the correct operating parameters of the bearings in the position of static and dynamic equilibrium. Obtaining such operating parameters requires finding a compromise solution, e.g., between the maximum temperature in oil films and the amplitudes of vibration accelerations in bearing nodes. The research results presented in the article can be used as a field for further discussion in the field of research on the reliability of turbochargers and be helpful in the design process in order to avoid design errors and reduce production costs.
Spiroid gears are used to transfer heavy loads with a significant reduction in input speed. Like most toothed gears, they are lubricated with oil whose physical properties change with temperature ...fluctuations, affecting the durability and reliability of the gear. Bearing this in mind, gear designers plan systems for measuring oil temperature during gear operation at the design stage. The authors of this paper are of the opinion that, in the case of spiroid gears, it may be insufficient to measure only oil temperature during gear operation. It seems that the working temperature of a pair of mating wheels has a decisive impact on the durability and reliability of the gear. The measurement of oil temperature in a tested gear should be treated as a supplementary measurement with the measurement of temperature on the toothed wheels as the basic measurement. Taking into consideration the above, an innovative test bench was designed and built, making it possible to observe how working parameters of the gear (torque and rotational speed) affect the temperature of the lubricating oil, but most of all, the working temperature of the pair of mating wheels. This paper presents, among others, the results of research on the impact of the rotational speed of the input shaft and load on the distribution of temperature on the toothed rim of the face gear.
Flower-like copper sulfides nanostructures were synthesized via the solvothermal route. The structural, optical and electrochemical properties of the synthesized materials were characterized by means ...of X-ray diffraction (XRD), scanning electron microscopy, ultraviolet–visible spectrometry and Fourier transform infrared spectroscopy (FTIR). Thermal behavior of the obtained flower-like materials was analyzed by TG, XRD and FTIR in situ measurements, over the temperature range of 25–800 °C. It was found that both shape and phase composition remain stable until the temperature reaches 200 °C. Phase transformation mechanism was discussed. During annealing, mixture of CuS and Cu
1.8
S is converted to copper sulfide hydroxides (200–500 °C) and further to CuO (700 °C and higher). Nevertheless, hierarchically porous structure is stable only to 200 °C. Applying higher temperatures affects the solubility of the material and inflicts structural damage, resulting in the formation of dense oval particles with size of 20 to 200 nm.
Polymer fiber composites are increasingly being used in many industries, including the defense industry. However, for protective applications, in addition to high specific strength and stiffness, ...polymer composites are also required to have a high energy absorption capacity. To improve the performance of fiber-reinforced composites, many researchers have modified them using multiple methods, such as the introduction of nanofillers into the polymer matrix, the modification of fibers with nanofillers, the impregnation of fabrics using a shear thickening fluid (STF) or a shear thickening gel (STG), or a combination of these techniques. In addition, the physical structures of composites have been modified through reinforcement hybridization; the appropriate design of roving, weave, and cross-orientation of fabric layers; and the development of 3D structures. This review focuses on the effects of modifying composites on their impact energy absorption capacity and other mechanical properties. It highlights the technologies used and their effectiveness for the three main fiber types: glass, carbon, and aramid. In addition, basic design considerations related to fabric selection and orientation are indicated. Evaluation of the literature data showed that the highest energy absorption capacities are obtained by using an STF or STG and an appropriate fiber reinforcement structure, while modifications using nanomaterials allow other strength parameters to be improved, such as flexural strength, tensile strength, or shear strength.
Radial slide bearings are typically used in turbochargers (among other applications), owing to their simple design and advantages, such as good heat dissipation from the working zone, high stability ...of operation and low resistance to motion. The current research is both experimental and theoretical. In a state of static equilibrium, the operation of a bearing can be described using a system of five coupled differential equations. The bearing’s operating parameters are related to the type of oil used. Two types of oil, VG46 and VG68, were used for testing. In accordance with the applicable standard, the tolerance of kinematic viscosity of oils is ±10%. The results imply a significant influence of the oil class and viscosity tolerance on the resistance to motion caused by internal friction forces in the oil. In conclusion, it seems advisable that the calculation procedures currently in use should include the slide bearing design optimisation by taking the resistance to motion in the bearing into account.
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