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Dynamic coupled vibration analysis of a large wind turbine gearbox transmission system
Get PDFA lumped-parameter coupled nonlinear dynamic model for one large multi-stage wind turbine gearbox transmission system is established comprehensively including wind varying load, mesh stiffness, dynamic transmission error, gravity, and bearing nonlinear characteristics to obtain the gearbox dynamic response. The vibration differential equations of the drive-train are deduced through the Lagrange’s equation. On the basis of that, the dynamics of wind turbine gearbox is investigated by a Runge-Kutta numerical method that includes simultaneous internal and external excitations. The results show that the dynamic response of the partial component is mainly superposed by high-frequency component caused by the internal excitation and low-frequency component caused by the external excitation. In medium-speed stage and high-speed stage, the vibration amplitude has obvious fluctuation, and the multiple frequency and random frequency components become increasingly obvious with increasing rotational speed and eccentricity at gear and bearing positions. Axial vibrations of the system also have some fluctuation. The bearing has self-variable stiffness frequency, which should be avoided in engineering design stage. The study results provide a theoretical foundation for dynamical characteristics evaluation and dynamic optimization of a large wind turbine gearbox transmission system
Study on the analytical model of vibration source for metro train
Get PDFA novel analytical model of vibration source for metro train based on “coupled vehicle and track basic unit” is established in this paper. The dynamic vehicle-track equations are completed with the displacement compatibility and the force equilibrium, and the model takes into account the infinite track structure, whole vehicle, track irregularity and wheel-rail Hertz contact. The special feature of track structure model is the periodical system of discrete supported sleepers, which converts the infinite integral equation into the combination in the wave number-frequency domain and simplifies the calculation progress. The rail dynamic responses and the wheel-rail contact force can be calculated easily. A complete software package TMCVT is programmed. A calculated example is achieved using the program. Compared the theoretical calculated results and the field tested results ,the coincidence with each other proved the analytical dynamic model for metro train coupled with vehicle and track is correct
Integrating a verified vehicle-bridge system model into fatigue assessment of steel railway bridge
Get PDFEffectively evaluating the fatigue behavior of aging bridge structures is an urgent task for engineers and researchers, as more and more existing bridges approach the end of their service life. Determining the fatigue load effects due to moving trains is a key aspect of the available assessment frameworks (e.g., the S-N approach). In this paper, a vehicle-bridge system model is integrated into the fatigue assessment procedure employing S-N lines. The system model is used to obtain fatigue stresses generated by moving train loads. The integration is proven able to aid in effective prediction of fatigue damage and remaining fatigue life of railway bridges
Frequency domain analysis of multiple modules-offshore mobile platform
Get PDFMultiple modules-offshore platform is a typical dynamic network with flexible-rigid-fluid coupling. The determination of the motions of this system in response to environmental forces and structure control mechanisms is a complex procedure, which may include system nonlinearities and position-dependent environmental loads, as well as any motion control mechanisms. For a systematic parametric study, given the large number of possible combinations of environmental conditions, a time domain analysis would be prohibitively time-consuming. However, frequency domain evaluation of AQWA can provide a simple and fast tool to fulfill this requirement
Application review on underwater radiated noise measurement by using a vessel’s own towed array
Get PDFCompared with the traditional fixed test and auxiliary measurement ship, the measurement of the underwater radiated noise by using a vessel’s own towed array has many advantages, such as flexible, convenient, low cost, and so on. In this paper, the previous researches on this method are summarized. From the view of implementing this technique, the method has been divided into four aspects: towed array design, U-turn manoeuvre, underwater sound propagation and towed array signal processing. Overall, this technology is practical and feasible, and has a good application prospect. Next, combined with a large number of experiments, further study on the selected principle of the towed array and U-turn technical indicators will be done
Analysis on the dynamic characteristics of the dual-rotor structures of a certain aero-engine
Get PDFA finite element model was constructed for a dual-rotor structure based on a certain aero-engine in this paper. Its dynamic characteristics was calculated and analyzed with the finite element software ANSYS. The characteristics were contrasted and analyzed for the dual-rotor structure with four bearings or five bearings. The influence was discussed and analyzed about the change of bearing’s stiffness to dynamic characteristics. The main conclusion was concluded as following: the low-pressure rotor vibrated in the first bending mode for the first and second modal shape; the critical speed gradually increased as the stiffness, it behaved obviously during a certain range of the stiffness, and meanwhile some modal shape would disappeared
Numerical prediction of temperature effect on propagation of rubbing acoustic emission waves in a thin-walled cylinder structure
Get PDFTemperature field has serious effects on the accuracy of rubbing acoustic emission (AE) source localization in a thin-walled cylinder structure, but it is difficult to explore the functioning mechanism through experiments. This paper aims to propose a thermos-elastic coupling simulation procedure to reveal the effect of the uniform temperature and non-uniform temperature field on the propagation characteristics of AE waves. To obtain the behaviors of guiding wave in the thin-walled cylinder, an efficient numerical simulation tool for AE wave propagation modeling is explored. The numerical results of AE propagation in a plate are compared with the experimental data. Then the semi-analytical finite element method is introduced to calculate the characteristics of multi-modal and dispersion. To remove the unwanted reflections from boundaries generated by the numerical simulation, a methodology combined with the infinite element and Rayleigh damping is presented. Consequently, several AE wave propagation simulations are carried out respectively, including the model with the uniform temperature in a range of 20-700 °C, and the non-uniform temperature field with the temperature of the central region, 649 °C. On the basis of the modeling and evaluation results, both the peak-to-peak amplitude and arrival time versus temperatures are summarized and analyzed. The validation results demonstrate that the proposed approach could be used efficiently to research rubbing AE source localization applications with a high degree of accuracy
Application of alpha-stable distribution approach for local damage detection in rotating machines
Get PDFIn this paper a novel method for informative frequency band selection for local damage detection is presented. Local damage in bearings/gearbox provides specific vibration signature, i.e. train of impulses with cycle related to fault frequency. The proposed approach is based on the α-stable distribution, which is an extension of the Gaussian one. The choice of this distribution is motivated by its superiority towards other distributions when modeling impulsive data. We introduce here the new selector (to select informative frequency band) which is based on the stability parameter α. Moreover we propose also the new time-frequency maps based on the measures of dependence adequate for α-stable distribution, namely autocodifference and autocovariation maps. The introduced methodology is illustrated by analysis of simulated and real vibration signals from heavy-duty rotating machinery. The results prove that proposed approach allows detection of multiple damages in signal and location of informative frequency band related to these damages. Moreover the analyzed examples indicate the α-stable distribution approach for some cases can give better results in contrast to the classical methodology based on the spectral kurtosis
Review of damage problems of the soft substrate interlayer film
Get PDFThis paper reviews the research progress of soft substrate interlayer film, including the applications and the preparation methods of the soft substrate interlayer film, the testing means of the films’ structure and composition and the researches of the film damage, especially the dynamic damage. As well as the future research directions and applications are put forward
Carrying capacity analysis and optimizing of hydrostatic slider bearings under inertial force and vibration impact using finite difference method (FDM)
Get PDFAccuracy of machine tool with a gantry frame is reduced due to the vibration caused by inertial force impact. Hydrostatic slider bearings are considered as key structures of machine tools, which play an important role in improving impact and vibration resistance ability as dynamic performance. In this work, an incline model which combines bending deformation with linear displacement is simulated using working conditions of the straddle carrier under inertial force impact as an imitation of vibration amplitude. Using finite difference method (FDM), numerical solution of pressure distribution in oil pad can be determined by solving the Reynolds equation. Relationship between carrying capability and incline extent can be determined by analyzing the resolution of the Reynolds equation. A new type of oil pad size optimizing process is propose in this work, which is carried out based on the analysis of the analyzing result to enhance the inertial force resistance ability. Finally, impact resistance capacity of machine tool can be improved by sacrificing oil film thickness