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.
By analysing and comparing the existing solutions of universal gear reducers with helical gears of the leading manufacturers, it can be noticed the effort to increase the load capacity of the gear ...reducer within the same axis height. In this way, the manufacturers can offer smaller (cheaper) gear reducers, as well as to simultaneously increase the values of the largest gear ratios. This concept enables the offer of lower-stage (cheaper) gear reducers with higher gear ratios in certain segments of gear ratios. By these efforts, it is reached the maximum, but the further increase is possible only by changing the current concept of universal gear drives. Within this paper, it is given an overview and analysis of one of the possible new conceptual solutions of modern universal motor gear reducer.
The aim of the research presented in this paper is to examine the accuracy (to what extent the 3D print fits to the 3D model) and the precision (which establishes the consistency of the measurements) ...for small-sized plastic parts printed on Zortrax M200 3D printer. One of the goals of the research is to find out how much the thickness of a wall (or of a bolt) can be reduced as it still to keep its stiffness and dimensional precision. A proper method for designing part couples was targeted. In order for a part to be correctly assembled with its pair, the deviation of the physical dimensions was taken into account. Also, the results of the experimental work on the capabilities and limitations of printing technology using this printer are presented in this paper. Several parameters such as surface quality and strength, layer shifting or misalignment are closely studied.
Today, for almost all products, the appearance is very important. Thus, for example, the appearance of universal gear reducers was not given so much attention, but today there are many very ...interesting solutions of shape, colour and graphic design. It should have in mind that universal gear reducers have much complex construction comparing them with special gear reducers. In the same time, they have to provide different positions and way of mounting and different speeds with different powers (torques) at the output shaft. Particularly, it should be noticed, that within all universal gear reducers single-stage gear units are nowadays increasingly used because their gear ratio values are increased (values of gear ratio can go up to 15) so that these reducers largely cover most of the two-stage gear reducers with their gear ratio values, so thereby their exploitation is significantly increased. Single-stage gear reducers are very simple products, and today there is a large number of manufacturers of such product. However, their mounting dimensions and way of mounting are not defined by a standard, so there is a variety of units with different dimensions and way of mounting. Although, most manufacturers look up to dimensions of leading manufacturers (usually SEW) in order to ensure greater exchangeability of their gear units. It is interesting to note, that most manufacturers tend to adopt the design of housing that will be substantially different from competing solutions. The reason is probably to avoid the possibility of being accused of copying someone else’s solution. However, there are manufacturers that retain almost identical housing design as a competing solution (probably they bought the licence or the solution is copied without permission). This paper considers only the design solutions of single-stage gear reducer in order to indicate the expected directions of their further development.
Ball bearings can be found in all machines with rotary movement. Dynamic behavior analysis of ball bearings is a phenomenon that has been studied for many years. Previous studies on the dynamic ...behavior of ball bearings are based on describing the state of ball bearings using mathematical models. In addition to mathematical description, computers simulations based on finite element methods are also applied. This paper presents study of the dynamic behavior of ball bearings using artificial neural networks. Artificial neural network models are able to predict the amplitude of vibration that will generate the analyzed bearings depending on the lubrication. In this way, by the application of artificial neural networks bearing dynamic behavior can be predicted depending on the geometric parameters and lubrication.
The basic parameters of the universal gear drives, except the axis height, are not defined by the standard, so the manufacturers of universal gear reducers can define them in their way. Most of the ...manufacturers followed the parameter values of universal gear reducers of leading world producers in order to ensure their interchangeability and the better positioning of their gear units at the market. This paper deals with the analysis of the influence of the gear pair teeth number on the size of the module, as well as on the load carrying capacity of single-stage universal gear units. For defined gear ratio values, different combinations of teeth number of pinion and driven gear were selected. Further, it was made calculation of the basic geometric dimensions of the gear pair, as well as the load capacity.
We investigated the effects of cell therapy on local mechanical dyssynchrony (LMD) in patients with nonischemic dilated cardiomyopathy (NICM). We analyzed electromechanical data of 30 NICM patients ...undergoing CD34+ cell transplantation. All patients underwent bone marrow stimulation; CD34+ cells were collected by apheresis and injected transendocardially. At baseline and at 6 months after therapy, we performed electromechanical mapping and measured unipolar voltage (UV) and LMD at cell injection sites. LMD was defined as a temporal difference between global and segmental peak systolic displacement normalized to the average duration of the RR interval. Favorable clinical response was defined as increase in the left ventricular ejection fraction (LVEF) ≥5% between baseline and 6 months. Using paired electromechanical point-by-point analysis, we were able to identify 233 sites of CD34+ cell injections in 30 patients. We found no overall differences in local UV between baseline and 6 months (10.7 ± 4.1 mV vs 10.0 ± 3.6 mV, P = 0.42). In contrast, LMD decreased significantly (17 ± 17% at baseline vs 13 ± 12% at 6 months, P = 0.00007). Favorable clinical response at 6 months was found in 19 (63%) patients (group A), and 11 (37%) patients did not respond to cell therapy (group B). At baseline, the two groups did not differ in age, gender, LVEF, or N terminal-pro brain natriuretic peptide (NT-proBNP) levels. Similarly, we found no differences in baseline UV (9.5 ± 2.9 mV in group A vs 8.6 ± 2.4 mV in group B, P = 0.41) or LMD at cell injection sites (17 ± 19% vs 16 ± 14%, P = 0.64). In contrast, at 6 months, we found higher UV in group A (10.0 ± 3.1 mV vs 7.4 ± 1.9 mV in group B, P = 0.04). Furthermore, when compared with group B, patients in group A displayed a significantly lower LMD (11 ± 12% vs 16 ± 10%, P = 0.002). Thus, it appears that favorable clinical effects of cell therapy in NICM patients may be associated with a decrease of LMD at cell injection sites.
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