Journal of Vibroengineering
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Numerical simulation and optimization for electromagnetic noises of permanent magnet synchronous motors in vehicles
Get PDFIn the paper, the numerical simulation is conducted on the motor electromagnetic force firstly. Radial force waves of the motor are the main reason for causing electromagnetic vibration and noise. Then, electromagnetic forces are mapped into a structural model for computing electromagnetic vibration. Computational results are compared with experimental results, so the correctness of the computational model is verified. Then, electromagnetic noises are computed according to the vibration data of the motor. Electromagnetic noises of the motor are axis-symmetric in plane X and plane Z. In plane Y, the electromagnetic noise of the motor is skew-symmetric relative to a 45° angle. In plane X and plane Z, the noise is caused by the vibration of the end cap, while noise in plane Y is caused by electromagnetic radial forces. In addition, the motor electromagnetic noise has an obvious directivity. The motor also has obvious peak noises at 300 Hz, 400 Hz, 500 Hz, 600 Hz, 900 Hz, 1200 Hz, 1500 Hz and 1800 Hz. Peak noises are corresponding to 6th, 8th, 10th, 12th, 18th, 24, 30th and 36th orders of the motor. Finally, modal participation factors of the motor within the analyzed frequency are computed. Results showed that modals at the 3rd, 5th, 12th and 15th orders of the motor have most obvious impacts on electromagnetic noises. In particular, the 3rd order modal shape obviously affects electromagnetic noises. The electromagnetic noise is reduced by applying reinforced bars and damping layer to these key modal shapes, especially the peak noise. The total noise of the original structure is 58 dB, while the total noise of the improved structure is 52.3 dB. Obviously, the total noise is reduced by 9.8 %
Impact of rotor eccentricity on electromagnetic vibration and noise of permanent magnet synchronous motor
Get PDFRotor eccentricity is a common fault in permanent magnet synchronous motors. Its effect on the vibration and noise is thoroughly investigated in this paper. The additional force harmonics due to static eccentricity and dynamic eccentricity are firstly derived with the rotational direction of force harmonics into consideration. A finite element model is built to calculate the force and two dimensional fast Fourier transform is employed to obtain the space and frequency orders under different types of eccentricity. Then, a multiphysics model is established to predict the vibration and acoustic noise under different eccentricity types and levels. Finally, the conclusions drawn from the analytical and simulation results are partly validated by experimental test. It is found that rotor eccentricity greatly intensifies the vibration and noise due to the induced force harmonics with lower space orders. Dominant vibration and noise peaks would transfer to the frequency band in the vicinity of the lower modal frequency when eccentricity occurs
Development of a finger like multi-joint articulated surgical retractor for use in endoscopic surgery
Get PDFThe authors have developed an articulated medical instrument which assists with the movement of and maintenance of the position of such as a lung during surgery to assist providing improved viewability and providing the necessary space required to work efficiently and effectively. Conventionally holding such as, a lung in a given position is achieved by arranging gauze in an appropriate configuration with the aid of a simple shaft like surgical instrument, however for various reasons the gauze requires constant replacement and rearrangement resulting in significant surgical inefficiency. By using an articulated mechanism that mimics the functionality of fingers, we have developed a surgical device that inherently provides greater mechanical stability and does not require the use of gauze, thus enabling more efficient surgery. The prototyping process was assisted with the use of 3D-CAD to simulate static and dynamic conditions and a 3D-printer to confirm the concept and then a working prototype was created. In order to validate the dynamic functionality of this surgical instrument, it was tested on a porcine lung which closely approximates human lungs by a clinical doctor of thoracic surgery. The result was that the developed prototype articulated mechanism was able to stably move and hold the lung in position during surgery thus confirming the dynamic efficacy of the mechanism
Numerical simulation on the impact of the bionic structure on aerodynamic noises of sidewindow regions in vehicles
Get PDFThe paper adopted a bionic hemispherical convex structure in the A pillar-rear view mirror regions according to actual requirements. Furthermore, impacts of the bionic structure on aerodynamic characteristics and noises in the region were studied. Friction resistance of airflows was greatly reduced, fluctuations and pulsation pressures of flow fields were also reduced, and characteristics of flow fields and sound fields were improved. The computational results were finally verified by the experimental test. Firstly, the aerodynamic lift force coefficient and drag force coefficient of the bionic model were computed, and they were obviously lower than those of the original model. The adhesive force between tires and ground during vehicle running was increased, and the danger degree of “waving” of high-speed vehicle running was weakened. In this way, stability of vehicle running could be improved. Secondly, flow fields of the bionic model were computed. Compared with the original model, an obvious vortex was behind the original model, while no vortexes were behind the bionic model. Therefore, convex structures of the bionic model had obvious impacts on flow fields behind the rear view mirror. Airflow separation situations were obvious improved at wheels, windshield and rear side windows of the bionic model. Due to blocking of convex structures of the A pillar and rear view mirror in the bionic model, airflows was hindered and obvious dragging phenomena were formed. Therefore, flow fields in the side window regions could be improved greatly. In addition, the flow field scope under the rear view mirror in the bionic model was also decreased. Ringed vortex structures appeared behind the rear view mirror in the bionic model. The ringed vortex structures were closely interlaced and then extended together backwards. Vortexes behind the rear view mirror in the original model were chaotic, where most of them were attached on the surface of side windows. In the original model, turbulent flows with certain strength were on the right upper corner of the side window region. In the bionic model, no turbulent flows were in the same regions. This result indicated that through using the bionic convex structures, airflows flowing through side windows could be combed and could move backwards towards upper and lower edges of the side windows. It could be predicted that pulsation pressures on the side window surface would surely decrease. Therefore, aerodynamic noises caused by pulsation pressures in side window regions would also be improved correspondingly. Especially in regions behind A pillar-rear view mirrors, the maximum noise reduction amplitude reached about 20 dB
Effect of density and Poisson’s ratio on thermal induced vibration of parallelogram plate
Get PDFThe present paper provides mathematical model for the study of natural (free) vibration of non homogeneous tapered parallelogram plate on clamped boundary condition. Here non homogeneity (in material) of the plate’s means that the density and Poisson’s ratio varies circularly and exponentially respectively. For tapered, we assumed that thickness of the plate varies linearly in one direction. Bi parabolic temperature (parabolic in ζ-direction and parabolic in ψ-direction) variation on the plate is being viewed. Rayleigh Ritz method is used to solve the model (governing differential equation of motion)
Sensitivity of beam-column element stiffness matrix to the crack parameters
Get PDFIn this article, a new cracked beam-column element stiffness matrix is proposed through static condensation method. Seven dimensionless coefficients are introduced and applied for a sensitivity analysis in different damage scenarios. The accuracy of this proposed stiffness matrix is verified, and compared to the other available methods. The variation of each stiffness component due to the conversion of crack parameters is assessed and shown in different graphs. This study reveals that cracking has a maximum stiffness reduction of 30 % in the beam-column elements with rectangular cross sections and the damaged elements remain stable until the crack depth is below 80 % of the section depth
Modeling and verification of response of RC columns strengthened in flexure with mechanically fastened FRP
Get PDFOne of the most important challenges exists in using of carbon fiber reinforced polymer(FRP) for strengthening of concrete members is the brittle behavior of RC members due to premature de-bonding of the layers. Mechanically fastened FRP (MF-FRP) systems are emerging as a promising method to prevent de-bonding of FRP strips and the prior brittle failure of strengthened RC members. The approach entails the use of fiber-reinforced polymer connected to the concrete substrate by means of steel anchors. In this research, a new anchor designed to delay de-bonding of FRP in reinforced concrete (RC) strengthened columns. Two reinforced concrete columns strengthened using the externally bonded conventional method and the new proposed method in comparison with unstrengthened RC column in the Laboratory. Specimens subjected to constant axial loading and cyclic lateral loading. Besides, numerical simulations performed using finite element models for nonlinear analyses of RC specimens: un-strengthened column; the column strengthened conventionally EB method and the column using new MF method
Analysis of selected acceleration signals measurements obtained during supervised service conditions – study of hitherto approach
Get PDFThe subject matter of the paper is an analysis of chosen results of acceleration signals measurements obtained from the prototype of the Rail Vehicle and Rail Track Monitoring System. This prototype of the monitoring system measures acceleration signals on designated elements of the electric multiple unit (EMU). These elements comprise components such as: bogie frames, wheels and bodies of railway vehicles. The analysis was prepared on the basis of rail vehicle journeys on sample sections of the Polish National Railways (PKP Polskie Linie Kolejowe S.A.) network. The products of measurements were converted to values of specific diagnostic parameters (statistical parameters), e.g. an amplitude (zero-peak), a root mean square, a kurtosis coefficient, an interquartile range. Comparing the values of diagnostic parameters with their permissible values allows the monitoring of distinctive dynamic behaviors of rail vehicles and track condition, as well as the temperature of the bearings of rail vehicle wheelsets. It also allows the determining of the condition of rail vehicle structure. The permissible values of certain diagnostics parameters could not be obtained from the literature. Therefore, this paper in part presents a way of obtaining these permissible values. The main intention of the analysis described here is to determine the usability of various diagnostic parameters and to identify the course of further research related to condition monitoring and diagnostics of rail vehicles and tracks
Aerodynamic response of micro rotary wings in wind perturbation
Get PDFOne high fidelity numerical method is extended to compute the unsteady aerodynamic loads when micro rotary wings suffer wind. The unsteady solutions are obtained by solving Navier-Stokes equations, where field velocity method is proposed to carry out the atmospheric perturbation. The convective terms are approximated by a high order WENO-Roe scheme, and time advance is performed by an implicit scheme of dual time stepping which can guarantee a degree of efficiency. Moving overset grids are used to facilitate the implement of rotational motion of rotary wings and relative movements between rotary wings, as well as the atmospheric perturbation. The results reveal that small atmospheric perturbation has an important impact on the flows of micro rotary wings under low Reynolds number. The response of thrust coefficient presents periodic fluctuation and its amplitude is proportional to that of wind disturbance, which provides the clue for active control research of rotary wing aircraft