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A novel integrated data processing algorithm for vibration fault testing for electromechanical devices, energy systems and engineering structures, based on the spectral kurtosis and the nonstationary nonlinear higher order wavelet bispectrum (WB), is proposed and investigated. A novel adaptive systematic approach for identification of frequency ranges for the WB is also proposed, investigated and successfully experimentally validated. Experimental validation of the proposed data processing technology is performed, using measured data, related to non-faulty rolling bearings and bearings at an early fault stage. The high effectiveness of early bearing diagnostics by the proposed nonlinear data processing technology has been experimentally demonstrated, using the Fisher criterion and probability of correct identification. Important advantage of the proposed technology is that it could be employed for data processing and identification of electromechanical devices and structures with unknown a priori frequency characteristics. The technology is generic and, therefore, has a potential to cover multiple applications for electromechanical devices, energy systems and engineering structures. [ABSTRACT FROM AUTHOR]

In this article, the exact free vibration of porous functionally graded rotating blades is investigated. The nonlinear 3D dynamics of the blade is simulated using the geometrically exact fully intrinsic beam equations, and the corresponding cross-sectional properties of the FG beam are developed. The material properties of the functionally graded material blade are graded through the thickness using a power law distribution. Furthermore, it is assumed that due to the manufacturing process, a level of porosity exists in the material which in turn can affect the material properties of the blade. Two porosity models resembling the even and uneven distributions of porosity are considered. First, the obtained results for a functionally graded material rotating blade are compared with those reported in the literature, and a very good agreement is observed. Furthermore, the effect of various parameters on the vibration of the functionally graded material beam is investigated. It is obtained that the dynamics of the rotating blade is sensitive to the type of the porosity due to manufacturing flaws. Moreover, the numerical results show that the blade length to height ratio, power law index, rotating speed and porosity distribution model affect the dynamics of the beam significantly. [ABSTRACT FROM AUTHOR]

An increase in electric railway vehicles service velocity requires that correct interaction between the pantograph and the catenary is ensured. This implies the need for developing mathematical models of pantographs and catenaries and determining their parameters. The article presents a method to determine parameters of mechanical joints of a railway pantograph based on analysis of pantograph subassemblies in swinging motion. The experimental tests consisted in disassembling the pantograph and creating partial subassemblies which were then analysed with respect to their damped linear or angular oscillations. The simulation analysis required developing, in CAD, 3D models of individual pantograph parts and their subassemblies. Defined were joints between particular elements, which represent of real pantograph structure. The inertia parameters of the model were determined, based on structural characteristics and physical properties of materials, used for manufacturing individual pantograph elements, and then verified experimentally. The dissipative parameters of the mechanical joints were calculated iteratively. The model of complete pantograph assembly was also subject to verification and in this case, good convergence between simulation and experiment results was achieved. The obtained parameter values can be used in simulation models of other railway pantographs having a similar structure. [ABSTRACT FROM AUTHOR]

Summary: Time‐varying fault impulse amplitude and time‐varying fault impulse interval are the main challenges for rolling bearing fault diagnosis under variable speed conditions. In this paper, a vibration‐based rolling bearing fault characteristic frequency (FCF) estimation and novel diagnosis method under time‐varying rotational speeds are proposed, using the demodulation transform. First, the FCFs with weak amplitudes are estimated, using the optimization‐based demodulation transform, whose main concept is that with the optimal demodulation operator (DO), the time‐varying frequency component can be transformed into a constant one and the largest peak can be detected in the spectrum of the demodulated signal. Second, the rolling bearing is successfully diagnosed with hypothesis‐based demodulation transform, whose main concept is that the rotational frequency (RF)‐related DOs under different fault types are estimated, based on the estimated FCFs and the fault characteristic coefficients (FCCs). Then the RF‐related peak in the spectrum of the demodulated signal can be used to detect rolling bearing fault. The effectiveness of the proposed method is verified, using both simulated signal and measured vibration signal. Novel comparisons with the current methods demonstrate much better ability of the proposed method for diagnosis of rolling bearing under variable speed conditions. [ABSTRACT FROM AUTHOR]