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Improved aerodynamic optimization for the design of wind turbine blades
Get PDFA wind turbine rotor converts the kinetic energy of wind to drive a generator which in turn yields electricity. The aerodynamic analysis and the optimization of design parameters for the wind turbine blades are key techniques in the early stage of the development of wind turbine blades. In this study a computational procedure using artificial neural network and numerical optimization techniques was developed for three-dimensional blades design of a wind turbine. The procedure was applied for improving a previously studied wind turbine rotor design. Results showed that the aerodynamic performance of the new blade has remarkable improvement after optimization
Application of incremental polymeric scales for high precision piezoelectric angular positioning system
Get PDFA high precision piezoelectric rotational stage with low-cost incremental polymeric scales is proposed and investigated in this work. For avoiding datum plane surface errors caused by application of additional bearings to support the rotational part, the latter one contacts with a stationary piezoelectric disc, which oscillates in travelling wave mode, at three specific points via contacting ring. The resolution of rotation is determined only by geometrical errors of external surface of the piezoelectric disc and can be easily achieved to be in the range of 1 µm. Low-cost polymeric scales are applied to measure angular displacement by means of moiré fringes. Peculiarities of scales fabrication are defined taking into consideration the final accuracy of the device
Research on the performance of buffer for landing gear based on the drop test
Get PDFBased on the drop test of the articulated main landing gear of Seagull 300 light multifunctional amphibious airplane, a further study has been conducted to establish buffer performance under different air chamber pressures and attitude angles. Through comparative analysis of the test results, the influencing rule of air chamber pressure and attitude angle on the buffer performance parameters (system capacity, vertical load, buffer compression, system efficiency and buffer efficiency) was obtained. The results demonstrate that air chamber pressure has a significant effect on the buffer system efficiency, while the attitude angle influences the system capacity a lot. With air chamber pressure increasing system efficiency decreases first, then gradually increases after reaching its minimum at 2.15 MPa and decreases at last after reaching its maximum at 2.7 MPa. Buffer efficiency decreases first and then increases after reaching its minimum at 2.2 MPa. When the attitude angle is between 3 and 12 degrees, the smaller the attitude angle, the more energy the system absorbs and the better the buffer performance is. The rate of change of performance parameters varies linearly with attitude angle. With the increase of angle, system capacity, maximum vertical load and system efficiency increase, and the change rate of buffer compression decreases correspondingly. The rate of change of system efficiency has the fastest growth
Geometry optimization of double wishbone suspension system via genetic algorithm for handling improvement
Get PDFMotion control, stability maintenance and ride comfort improvement are fundamental issues in design of suspension systems in off-road vehicles. In this paper, a double wishbone (DW) suspension system, mostly used in off-road vehicles, is modeled using ADAMS software. Geometric parameters of suspension system are optimized using genetic algorithm (GA) in a way that ride comfort, handling and stability of vehicle are improved. Simulation results of suspension system and variations of geometric parameters due to road roughness and different steering angles are presented in ADAMS and effects of optimization of suspension system during various driving maneuvers in both optimized and non-optimized conditions are compared. Simulation results indicate that the type of suspension system and geometric parameters have significant effect on vehicle performance
Effective reduction of stiffness at peak frequency in hydraulic engine mounts by using magneto-rheological fluids
Get PDFHydraulic engine mounts are generally used in aerospace and automotive applications for the purpose of cabin noise and vibration reduction. By careful selection of hydraulic mount design parameters, at a certain frequency, namely the notch frequency, the dynamic stiffness will be smaller than the static stiffness and cabin vibration and noise reduction is provided at that frequency. Literature review indicates that in all previous designs of hydraulic engine mounts the dynamic stiffness increases after the notch frequency. This phenomenon undesirable because of the increase in the force transmitted to the cabin. This paper proposes a new hydraulic engine mount that uses two working fluids. The new design has two notch frequencies and two peak frequencies. In this study, effective reduction of the peak frequencies has been demonstrated by using a controllable fluid as one of the working fluids and a non-controllable fluid as the second working fluid. As a result, one can obtain a hydraulic engine mount design with only one notch frequency but having no peak frequency. The new hydraulic engine mount design and its mathematical model are presented in detail and some discussions on the simulation results are provided
A study of selected properties in high dispersion padding welds produced in machine elements
Get PDFThis paper presents selected laboratory research results concerning the production of high dispersion padding welds that were made from Castolin EnDOtec DO390N P pulverized nanowire on acid resistant 0Hl8N9 steel using laser technology. The analysis of the microstructure showed a high dispersion of the micro- and nano-structure where the phase particles of large volume carbide (MC), M23(BC) boron carbides, and M2B borides are distributed in the fine-grained iron matrix. The study found extensive differentiation of chemical composition in the micro-areas and extensive non-homogeneity of the microstructure due to repeated laser melting of the padding weld layer. Its surface hardness was 68-72 HRC and the cross-sectional microhardness was as high as 990 - ll00 HV0, l
Modifying the brake drum geometry to avoid self-excited vibrations and noise
Get PDFA squealing noise of 50 dB was measured on a vehicle homologation test at around 900 Hz on the existing brake drum design, mounted on the rear axle of the mid-sized passenger automobile. Therefore, analysis of eigenfrequencies of the original drum design was performed using the impact hammer test and numerical analysis. It was established that a critical mode shape 0/2 exists at around 900 Hz, exactly where the squeal noise was recorded at the brake road noise evaluation vehicle test. The analysis was carried out with the intention to eliminate the possibility of the squealing noise by increasing the critical mode above 900 Hz. The relation between different brake drum modifications parameters and the eigenfrequencies was determined and the best solution was obtained. The first eigenfrequency of the proposed drum design was increased by 58 Hz and the difference between the in-plane and out-of plane mode shape was sufficient. We can conclude that the modified drum design will not have squeal issues at 900 Hz as there are no eigenfrequencies of the brake drum in that range and therefore the problem of the loud brake is solved
ANN prediction and RSM optimization of cutting process parameters in boring operations using impact dampers
Get PDFThe cantilever shape of the boring bar induces chatter vibrations in boring operations. Chatter vibrations consequently lead to increase in tool wear. Present work focuses on the prediction and optimization of cutting process parameters using ANN and RSM methods for phosphor bronze damping material attached to the boring tool. All-geared head lathe with temperature measurement setup was used to conduct experiments for various levels of cutting speed, depth of cut and position of damper from the cutting edge. Tool wear was measured using profilometer, while the temperature and tool wear were accurately predicted using the developed ANN model. The minimum value of temperature of 2800 C and tool wear of 0.13 mm were obtained by using Response Surface Methodology for the following input conditions: cutting speed of 300 rpm, depth of cut of 0.25 mm and damper position of 65 mm from the cutting edge
Nonlinear free vibration analysis of the functionally graded beams
Get PDFNonlinear natural oscillations of beams made from functionally graded material (FGM) are studied in this paper. The equation of motion is derived according to the EulerBernoulli beam theory and von Karman geometric nonlinearity. Subsequently, Galerkin’s solution technique is applied to obtain the corresponding ordinary differential equation (ODE) for the FGM beam. This equation represents a kind of a nonlinear ODE containing quadratic and cubic nonlinear terms. This nonlinear equation is then solved by means of three efficient approaches. Homotopy perturbation method is applied at the first stage and the corresponding frequency-amplitude relationship is obtained. Frequency-amplitude formulation and Harmonic balance method are then employed and the consequent frequency responses are determined. In addition, Parameter Expansion Method is utilized for evaluating the nonlinear vibration of the system. A parametric study is then conducted to evaluate the influence of the geometrical and mechanical properties of the FGM beam on its frequency responses. Different types of material properties and boundary conditions are taken into account and frequency responses of the system are evaluated for different gradient indexes. The frequency ratio (nonlinear to linear natural frequency) is obtained in terms of the initial amplitude and compared for different materials and end conditions
Fault diagnosis of main engine journal bearing based on vibration analysis using Fisher linear discriminant, K-nearest neighbor and support vector machine
Get PDFVibration technique in a machine condition monitoring provides useful reliable information, bringing significant cost benefits to industry. By comparing the signals of a machine running in normal and faulty conditions, detection of defected journal bearings is possible. This paper presents fault diagnosis of a journal bearing based on vibration analysis using three classifiers: Fisher Linear Discriminant (FLD), K-Nearest Neighbor (KNN) and Support Vector Machine (SVM). The frequency-domain vibration signals of an internal combustion engine with intact and defective main journal bearings were obtained. 30 features were extracted by using statistical and vibration parameters. These features were used as inputs to the classifiers. Two different solution methods - variable K value and RBF kernel width (σ) were applied for FLD, KNN and SVM, respectively, in order to achieve the best accuracy. Finally, performance of the three classifiers was calculated in journal bearing fault diagnosis. The results demonstrated that the performance of SVM was significantly better in comparison to FLD and KNN. Also the results confirmed the potential of this procedure in fault diagnosis of journal bearings