In order to promote the development of the new dry ice powder pneumatic rock breaking technology and the safety and environmental pollution assessment of the application site, this paper measures the vibration and noi...
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In order to promote the development of the new dry ice powder pneumatic rock breaking technology and the safety and environmental pollution assessment of the application site, this paper measures the vibration and noise generated by the dry ice powder pneumatic rock breaking process and extracts the vibration through the Hilbert-Huang transform analysis method. The test results show that (1) the noise measurement found that the noise propagation is directional. The pre-splitting of the first shot makes the second shot of the noise spread more quickly and the sound pressure level is higher. (2) Compared with the Fourier transform, HHT transform is a better tool to extract the characteristics of vibration waveform. (3) When the focal distance is 7 m, the distribution of energy in frequency is scattered, and the damage of vibration to buildings can be considered more comprehensively through the distribution of energy in time and frequency.
The existing methods for transformer core-loosening fault diagnosis primarily focus on fundamental frequency analysis, neglecting higher-frequency components, which limits early detection accuracy. This study proposes...
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The existing methods for transformer core-loosening fault diagnosis primarily focus on fundamental frequency analysis, neglecting higher-frequency components, which limits early detection accuracy. This study proposes a comprehensive approach integrating full-band vibration analysis, including high-order harmonics, to enhance diagnostic precision. A theoretical model coupling magnetostriction and thermodynamics was developed, combined with empirical mode decomposition (EMD) and Pearson's correlation coefficient for fault characterization. A 10 kV transformer core vibration test platform was constructed, capturing signals under normal, partially loose, and completely loose states. The simulation results aligned with the experimental data, showing vibration accelerations of 0.01 m/s2 (Phase A) and 0.023 m/s2 (Phase B). A multi-physics coupling model incorporating Young's modulus variations simulated core loosening, revealing increased high-frequency components (up to 1000 Hz) and vibration amplitudes (0.2757 m/s2 for complete loosening). The joint EMD-Pearson method quantified fault severity, yielding correlation values of 0.0007 (normal), 0.0044 (partial loosening), and 0.0116 (complete loosening), demonstrating a clear positive correlation with fault progression. Experimental validation confirmed the model's reliability, with the simulations matching the test results. This approach addresses the limitations of traditional methods by incorporating high-frequency analysis and multi-physics modeling, significantly improving early fault detection accuracy and providing a quantifiable diagnostic framework for transformer core health monitoring.
In this paper, a thin viscoelastic plate with attached masses, which are widely used in modern engineering and construction is considered. The natural and forced linear vibrations of round viscoelastic plates with att...
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In this paper, a thin viscoelastic plate with attached masses, which are widely used in modern engineering and construction is considered. The natural and forced linear vibrations of round viscoelastic plates with attached concentrated masses is investigated. To obtain the equations of motion of the mechanical system, the plate equation with operator coefficients and generalized Dirac functions is used. The problem is reduced to the joint solution of integro-differential equations in partial derivatives and the system of ordinary integro-differential equations of the corresponding dimension. To solve the obtained systems of integro-differential equations, the method of separation of variables, the freezing method, the methods of ordinary differential equations, the Gauss method and the Mueller method are applied. The analytical solution of the problem of linear vibrations of circular viscoelastic plates of constant cross-section with attached concentrated masses is obtained. On the basis of numerical results it is established that point attachment of masses leads to a decrease of real and imaginary parts of the natural frequencies up to 20%. It is found that by attaching masses to the plate the number of frequencies will not change. In the case when the mass is attached to the plate with massless elements, then the number of frequencies increases, while the first frequency decreases.
The vibration of high voltage circuit breakers is superimposed by the impact vibration generated by the action of its components. When the operating states of the components change, the vibration waveform will be dist...
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The vibration of high voltage circuit breakers is superimposed by the impact vibration generated by the action of its components. When the operating states of the components change, the vibration waveform will be distorted. To extract the state information contained in the vibration signals, in this paper we propose a new method for the mechanical fault identification of circuit breakers based on the joint analysis of time-frequency domain features. Firstly, a new time-reference-distance algorithm (TRD) which employs feature space to grab information is proposed to get the time-domain features in detail. The feature space is constructed by the kurtosis, crest factor, and peak divergence degree of the time-domain waveform. Further, we propose another new algorithm, the shape entropy algorithm (SE), to extract the frequency-domain features. Through converting the power spectrum of the vibration signals to polar coordinates via the divergence factor, the SE features are then obtained by combining with the information entropy formula. Finally, the TRD and SE features are combined and input into the support vector machine (SVM) model for fault identification. The test results verify the efficiency of the methodology and the identification process takes less time. It has a practical application value.
The problem of active damping of cylindrical shell vibrations with free boundary conditions is considered. The shell is supported by rings. An example of the identification of the source and damping of bending vibrati...
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The problem of active damping of cylindrical shell vibrations with free boundary conditions is considered. The shell is supported by rings. An example of the identification of the source and damping of bending vibrations of a shell is presented.
Electro-hydraulic vibration equipment(EHVE)is widely used in vibration environment simulation tests,such as vehicles,weapons,ships,aerospace,nuclear industries and seismic waves replication,etc.,due to its large outpu...
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Electro-hydraulic vibration equipment(EHVE)is widely used in vibration environment simulation tests,such as vehicles,weapons,ships,aerospace,nuclear industries and seismic waves replication,etc.,due to its large output power,displacement and thrust,as well as good workload adaptation and multi-controllable *** on the domestic and overseas development of high-frequency EHVE,dividing them into servo-valve controlled vibration equipment and rotary-valve controlled vibration *** research status and progress of high-frequency electro-hydraulic vibration control technology(EHVCT)are discussed,from the perspective of vibration waveform control and vibration *** problems of current electro-hydraulic vibration system bandwidth and waveform distortion control,stability control,offset control and complex vibration waveform generation in high-frequency vibration conditions are pointed *** the existing rotary-valve controlled high-frequency electro-hydraulic vibration method,a new twin-valve independently controlled high-frequency electro-hydraulic vibration method is proposed to break through the limitations of current electro-hydraulic vibration technology in terms of system frequency bandwidth and waveform *** new method can realize independent adjustment and control of vibration waveform frequency,amplitude and offset under high-frequency vibration conditions,and provide a new idea for accurate simulation of high-frequency vibration waveform.
With ability of full-field phase distribution obtained from one grating image by the sampling moire method, it has potential applications in the dynamic measurement. On the basis of introduction to the basic principle...
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ISBN:
(纸本)9783037855072
With ability of full-field phase distribution obtained from one grating image by the sampling moire method, it has potential applications in the dynamic measurement. On the basis of introduction to the basic principle, the sampling moire method is utilized to characterize the vibration parameters of a shaking stage. A piece of paper with black and white grid lines is pasted on the surface of the measured object as an optical non-contact displacement sensor. Experiment images are recorded by a CCD camera during the translational experiments and vibration experiments. The translation experimental results show that the sampling moire method has a high measurement accuracy of less than 0.12% of the grating pitch. The vibration experimental results are consistent with the theoretical values. Experimental errors are discussed finally.
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