Papers by Keyword: Vibration Analysis (VA)

Abstract: In this paper, a new solution method is proposed for determining the natural frequency of a given mode for a finite-length circular cylindrical thin shell with a circumferential part-through crack. The governing equation of the cracked cylindrical shell is derived by integrating the line-spring model with the classical thin shell theory. The proposed method calculates the natural frequency from an initial trial to satisfy both the governing equations and appropriate boundary conditions through an optimization process. The initial trial is proposed to satisfy the governing equations by using the beam modal function to determine the modal wavenumbers and mode shapes of cylindrical shells in the axial direction, assuming the flexural mode shapes of cylindrical shells in the axial direction to be of the same form as that of a flexural vibration beam with the same boundary conditions. Four representative sets of boundary conditions are considered: simply supported (SS-SS), clamped-clamped (C-C), clamped-simply supported (C-SS), and clamped-free (C-F). Compared with the finite element (FE) method, the proposed solution method is verified to provide an accurate and efficient way to calculate the dynamic characteristics of both intact and cracked cylindrical shells.

Abstract: This paper presents a comparison of different measurement techniques for condition monitoring of electric motors. Results are presented for vibration, acoustic and thermal analysis. Vibration signals were measured by piezoelectric accelerometers, acoustic by microphones and temperature data was collected by an infrared camera. Two induction motor cases were examined – healthy motor case and combination of static eccentricity with soft foot case. Vibration monitoring is a well known technique used in condition monitoring and in this work vibration measurements were used as a reference signal for assessment of the value of acoustic and thermal measurements. As presented in result section both acoustic analyses as well as thermal images appear as valuable techniques for condition monitoring of electric motors. All the measurements where conducted in an industrial environment.

Abstract: Vibration analysis(VA) is a very important method in the industry inspection application. Based on ISO10816, the severity level, certainty rating, the total risk rating matrix and the risk assessment index were proposed in the paper. Based on the testing samplings in a certain company and the assessment system established above, the VA analysis can be conducted and it is a good method for applying the predictive maintenance in the plant.

Abstract: The swashplate rod is a key component of helicopter control system. The vibration environment of helicopter is quite complex. The natural frequency of the swashplate rod is generally low. So resonance occurs easily. Resonance could reduce control precision or even damage the whole control system. Established dynamic and mathematical model of swashplate rod. Analyzed the vibration characteristics. Obtained the natural frequency and vibration mode function of the rod. In the compression, tension and free state, the natural frequency of the rod is basically the same. Made flight experiment with a developing helicopter as object. Measured the load of the swashplate rod in flight conditions. Make Fourier analysis to the load. Obtained the frequencies of the load on the rod. The frequencies coincide with 1 and 2 times of the rotor speed.

Abstract: The objective is to provide a method about equipment condition monitoring and fault diagnosis. The method could indicate equipment operating parameters, working conditions and specific status. We used CDMS system monitoring mine hoist key parts of the vibration velocity, introduces the vibration sensor reasonable decorate, in the time domain analysis of speed amplitude values, in frequency domain speed spectrum analysis, according to the monitoring signal analysis processing results, give the diagnostic conclusions that the gear of second shaft have uniform force, and a little corrosion, peel and eccentric, puts forward that we should strengthen vibration monitoring about the second shaft of speed reducer, Observe reducer wear trend using the iron spectral analysis, Supervise lubricating oil quality, change oil when necessary.

Abstract: Comprehensive meshing stiffness and single tooth meshing stiffness are calculated by tooth contact analysis and load tooth contact analysis program. The corner meshing impact model is proposed. Nonlinear dynamic model of helical gear transmission system is established in this paper considering time-varying meshing stiffness excitation, transmission error excitation, corner meshing impact excitation, and the backlash excitation. Take the ship’s helical gear transmission system as an example, the mesh impact force is derived and the primary factors that produce noises are discussed. The effects which the mesh impact brings to vibration characteristics of the gear dynamic system are concluded. Meshing impact has an inevitable effect on the vibration of the dynamic system. Impact excitation costs 8.5% in maximum of vibration acceleration response, 31% in maximum of instantaneous acceleration, and 4.9% in maximum of spectral component amplitude.

Abstract: A new driven pattern is proposed in this paper, which is based on laser shock wave and outstand in high energy efficiency, remote control, wireless and directionality. We describe the working principle of the laser shock wave driven pattern in detail. Furthermore, by a copper irradiated cantilever beam, the vibration state driven in different laser conditions is investigated with simulation and experiment, corresponding numeral analysis is performed to assess the driven effect.

Abstract: Wind power industry enormously expanded during the last several years. However, wind turbines are subjected to different sorts of failures, which lead to the increasement of the cost. The wind turbine gearbox is the most critical component in terms of high failure rates and long time to repair. This paper described common failures and root causes of wind turbine gearboxes. Then it focused on fault diagnosis and monitoring techniques for the wind turbine gearbox. The challenges and future research directions were presented, and the simulator rig of wind turbine gearbox was designed to develop condition monitoring and fault diagnosis techniques for wind turbine gearbox.

Abstract: This paper introduces a FEA method for vibration characteristics analysis of an aero-engine shrouded turbine blade and makes an actual modal analysis of this shrouded blade based on this method in UG software environment. The first six natural frequencies and mode shapes of this shrouded blade are calculated. And also, the dynamic characteristics of the shrouded turbine blade are discussed in detail according to the analysis results. The FEA method and the vibration characteristics analysis results in the paper can be used for optimal design and vibration safety verification of this aero-engine shrouded turbine blade.

Abstract: This paper presents a FEA method for vibration characteristics analysis of aero-engine compressor disc. An actual modal analysis of a certain aero-engine compressor disc is made based on this method. The first ten natural frequencies and modes of this compressor disc in fully constrained boundary condition and in free vibration condition are obtained respectively. And also, the vibration characteristics of each natural mode and its effect on compressor disc and other accessories are analyzed in depth. The analysis process and results presented in this paper can be references for further study on optimal design and vibration safety verification for this aero-engine compressor disc.