Appropriate lubrication of the rolling bearing is needed to lower the friction between the surfaces in mutual contact and their wear. A lubricant should completely separate the rolling elements from the raceways. The values that affect the efficiency and regimes of lubrication are analyzed in the paper, after which it is introduced a lubrication regime coefficient. This coefficient makes it possible to choose in a simple and fast manner an optimum combination of rolling bearing and lubricant based on the known shaft speed, external load, and rolling bearing operating temperature. For certain bearings with radial contact and certain lubricants, the lubrication regime dependence on the shaft speed and contact load is shown.
A considerable slide exists between the flanks of worm and gear during the work, which results in flank wear and considerable loss of energy. The energy is, thereby, converted into heat, which leads to the warming-up of gear drive, compromising its correct operation, and to scuffing in critical cases. Oil temperature has an important role in thermal stability. Viscosity depends on temperature. Viscosity significantly affects the processes in the contact zone, i.e. the energy losses, and hence the temperature. Optimal lubrication can be provided only in the relevant field of temperatures. The paper presents experimental and theoretical research on the effect of temperatures and thermal stability of a worm and gear set with a gear made of sintered steel Fe1.5Cr0.2Mo on their ability and appearance of boundary conditions
Worm gear transmissions have number of advantages over other types of transmission, allowing them a wide scope of applications for the transfer of power and movement. One of the important advantages of this transmission is the possibility of obtaining a large transmission ratio. The lack of worm gear transmission means a relatively low efficiency, especially for the extreme operating conditions primarily related to the high frequency of rotation. Between the flanks of worm and worm gears there is considerable slippage, which results in wear at the worm gear flank and considerable significant power losses that are converted into heat. The amount of energy that is converted into heat to a large extent is determined by the friction coefficient between the flanks. It is therefore very important to take into consideration the process of tribo-system mesh of flanks and lubricant. The paper presents FEM calculated distribution of transmission temperature based on the data about power losses obtained analytically. The resulting temperature distribution is compared to the experimental research.
Air-cooled condensers in thermal power plants have recently become increasingly popular. Besides all the advantages they have, like no demands for water supply on the plant site and no need for taking care of environmental regulations, they also have some serious disadvantages. One of the biggest disadvantages air-cooled condensers do have is precisely the nature of the Earth?s atmosphere being their low temperature reservoir. Low density and low heat capacity of the air as the cooling medium combined with extremely stochastic behavior of the atmosphere itself put some serious challenges in front of the air-cooled condenser?s proper and steady functioning. In this paper, the operating parameters of the air-cooled condenser in the chosen thermal power plant were investigated to gain a clearer insight into the influence of the atmospheric changes on its entropy generation and consequently on its efficiency. Also, the acquired results were further proposed as a starting point for potential optimization of the process inside the device.
The reliability study is the most important part of the engineering design process, as it is the basis of analysis and assessment of future product performance in exploitation. Since performance cannot be predicted with absolute certainty, the application of reliability theory includes probability theory and unreliability modeling. The proposed approach has been applied to assess the reliability of gear planetary power transmissions. The assessment of system reliability was determined on the basis of the block diagram method, as a function of the reliability of individual components, calculated by statistical analysis. Using the Weibull model, the reliability of the planetary gear was defined on the basis of the probability of failure of the gear teeth and the results were interpreted to assess the reliability of the component and the entire planetary train. For a more precise assessment of reliability and to avoid modeling every failure and mode of occurrence, a competitive risk model was developed. The reliability assessment study was conducted with a “bottom-up” approach. Reliability has been assessed, for instantaneous, estimated and assigned failures rate of planetary train and component.
Simple cycloid drive is a type of high-sensitive gear train, by which it is possible to realize high transmission ratios in single-stage. Their advantage is also reflected in the compactness and simplicity of production, as well as achieving greater efficiency compared to conventional planetary drive train. In this paper, the basic equations for obtaining the transmission ratios, torque and efficiency of simple cycloid drive with stepped planets are shown. The dependence between basic transmission ratio and basic efficiency was also examined to find the optimum value of the transmission ratio and determine the point at which the self-locking occurs.
The deep groove ball bearing is one of the most important components of the rotary motion system and is the research subject in this paper. After factory assembly, new ball bearings need to pass quality control. The conventional approach relies on measuring the vibration amplitudes for each unit and sorting them into classes according to the vibration level. In this paper, based on experimental research, models are created to predict the vibration class and analyze the dynamic behavior of new ball bearings. The models are based on artificial neural networks. A feedforward multilayer perceptron (MLP) was applied, and a backpropagation learning algorithm was used. A specific method of training groups of artificial neural networks was applied, where each network provided an answer to the input within the group, and the final answer was the mean value of the answers of all networks in the group. The models achieved a prediction accuracy of over 90%. The main aim of the research was to construct models that are able to predict the vibration class of a new ball bearing based on the geometric parameters of the bearing rings. The models are also applied to analyze the influence of surface roughness of the raceways and the internal radial clearance on bearing vibrations.
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