In this work, characteristics of various BALL BEARING parameters are studied under different loads androtational speeds. By using Dimensional Analysis (DA), dimensionless parameters are computed which providessolution for a group of parameters. This analysis can be accomplished by using the Buckingham π-theorem. DAleads to reduction of the number of independent parameters involved in a problem. These independent parametersget expressed as dimensionless groups. These dimensionless groups are always ratios of important physicalquantities involved in the problem of interest. In modeling and experimentation, its main function is to reduce theamount of independent variables, simplify the solution, and generalize the results. It becomes an effective method, especially if a complete mathematical model of the investigated process is not known. Moreover, in the presentwork the Buckingham π-theorem is applied to find the influencing parameter π 5 by using the Taguchi method.

In recent years, with the advent of the Fourth Industrial Revolution concepts and the development of artificial intelligence technologies, new approaches such as the digital twin have been introduced. In a digital twin, a virtual counterpart of the physical system during its whole life is created, with abilities such as analyzing, evaluating, optimizing, and predicting. The first step in creating a digital twin model is to construct a (multi) digital health indicator that describes different aspects of the physical component state during the whole life of the component. In this research, a new method for constructing health indicators based on vibration measurement and a deep learning model has been introduced. For this purpose, the Continuous Wavelet Transform was used to convert the raw vibration signals into two-dimension images; Then, the deep learning model was used to extract features from the images and the health indicator is constructed based on the differences of the images in normal and failure stages. In this article, various Autoencoder architectures are discussed, and it is demonstrated that the Convolutional Autoencoder has better performance in terms of detecting incipient faults. The performance of the proposed model is evaluated by the vibration data of the BEARING, and the constructed health indicator exhibited a monotonically increasing degradation trend and had good performance in terms of detecting incipient faults.

Fault detection of BALL BEARINGs by the complex and non-stationary vibration signals with noise is very difficult, especially at the early stages. Also, many failure mechanisms and various adverse operating conditions in BALL BEARINGs involve significant nonlinear dynamical properties. The quality of chaotic vibration of BALL BEARINGs is studied by the reconstructed phase space. The phase space demonstrates different chaotic vibration of BALL BEARING for different healthy/faulty conditions. But, to easily use of this procedure in the BALL BEARING fault detection, the chaotic behavior of vibration signal is quantified by a set of new features. The new set of features based on chaotic behavior, including the largest Lyapunov exponent, approximate entropy and correlation dimension are extracted to acquire more fault characteristic information. The effectiveness of the new features based on chaotic vibrations in the BALL BEARING fault detection is demonstrated by the experimental data sets. The proposed approach can reliably recognize different fault types and have more accurate results. Also, the performance of the new procedure is robust to the variation of load values and shows good generalization capability for various load values.

The development of special grease makes it possible for angular contact BALL BEARINGs to operate at high speed and temperature, so, it become necessary to investigate thermal-fluid characteristics inside high-speed angular contact BALL BEARING lubricated with grease. In this paper, a simulation model for angular contact BALL BEARING was established with CFD software Fluent, the heat-fluid-solid coupling method was used to analyze the distribution and flow of grease, heat transfer, and temperature field inside the BEARING chamber. The results show that, grease distribution inside BEARING chamber was very inhomogeneous, most of grease was distributed on the both sides of the rolling elements along outer raceway and its flow velocity was very low, only a little grease was adhered on the surface of roll-ing elements, cage, and inner ring, its flow velocity was high; grease distribution inside BEARING chamber becomes more inhomoge-neous with the increase of BEARING speed; in BEARING heat transfer conduction was dom-inant and grease plays a key role, convec-tion of air and grease was insignificant; affected by heat transfer condition the temperature rise of BEARING components was obviously different, rolling elements have the highest temperature, the tempera-ture of inner ring was slightly lower than that of rolling elements, temperature of outer ring was the lowest. BEARING tempera-ture experiment was conducted on self-made test rig and verified the validity and accuracy of numerical simulation. The results of this study will provide some reference for lubrication design and thermal analysis of high speed angular contact BALL BEARING lubricated with grease.

Empirical mode decomposition (EMD) is one of the new methods for decomposing a signal into its constituent components. The existence of multiple error sources has led to activities to eliminate or mitigate their effects. In this research, one of the major problems of EMD for the separation of noise-polluted signals, namely, mode mixing problem has been studied. To solve this problem, bandwidth EMD has been used, which enhances the EMD method and processes speed and greatly prevents mode mixing problem. Also, among the available methods to extract the instantaneous properties, the proper pair of instantaneous properties identification and signal normalization method is presented by an example. To investigate the efficiency of the bandwidth EMD method, using the optimal method of extracting the instantaneous properties, the experimental data of a faulty BEARING have been studied and the instantaneous properties of both EMD method and the bandwidth EMD method have been extracted. Using the coefficient of variation criterion, it is shown that the bandwidth EMD method has a higher resolution and better results than EMD method. Finally, using information of decomposed white noise by EMD, the noise isolation quality of the original data is examined, which indicates a better decomposition of the results of the bandwidth EMD method.

In this research, the life expectancy of BALL BEARINGs in industrial applications is estimated based on known parameters. The overall mathematical calculation of such behavior is based on the theory of Lundberg and Palmgren. The proposed life estimation equation however lacks certain points to make it qualified as universal. A firm conclusion therefore could not be obtained on the basis of this equation alone, particularly when different operating conditions are involved.  One such example is the life of BALL BEARINGs while operating in clean lubricant environment, which is approximately up to 20 times longer than the calculated life based on the previously prescribed equations.  On the other hand, active life under contaminated lubricants is nearly close to one-tenth of the calculated life originally thought to be correct.

Eddy current dynamometers are one of the most important equipment of internal combustion engine test cells in powertrain companies. Failure of rolling element BEARINGs in these assets is a common reason for downtime hours of engine test beds. Insufficient information in this field not only imposes unwanted expenses, but also would result in wrong engine testing data. The purpose of this article is the identification and classification of rolling element BEARINGs failure modes in the eddy current dynamometers. This is an essential research for choosing an appropriate maintenance plan in engine testing laboratories. More than 30 faulty BALL BEARINGs of different eddy current dynamometers are collected to study different modes in which the BEARINGs actually fail to operate properly. In addition, metallurgical studies have been applied on the failed parts to specify possible root causes of failure. The dynamometers whose BEARINGs are under study have been employed in different engine testing procedures that an eddy current dynamometer is capable of performing e.g. endurance tests, over-speed tests, etc. so that a diversified collection of modes is available which would happen in any eddy current dynamometer. The recognized cases are then classified to prepare a practical basis for condition monitoring of dynamometers using vibration analysis or other methods.