Journal of Engineering and Thermal Sciences
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The stability of the tethered trailer and its control
Get PDFTethered trailer vehicle is a nonprofessional tractor that drags an unpowered vehicle with rope. In this paper, a nonlinear dynamic model of the tractor is developed. With the Dugoff’s tire model. A new nonlinear tethered tractor-trailer model is created to simulate critical parameters. A trailer front-wheel steering feedback control strategy is derived in order to improve stability and trajectory tracking feature the comparison of the simulation results for tension of the traction rope, the trajectory following resistance, and the handling stability clearly demonstrates the efficacy of the proposed control strategy
Research on flow-sound separation algorithm of aerodynamic noise based on immersed boundary method
Get PDFWith the development of theoretical models, numerical algorithms and available computational power, numerical aero-acoustics presents a huge prospect for solving the actual problems of aerodynamic noises. Under low Mach number, structures with a complicated geometric shapes were selected as the research objects to analyze their aerodynamic noises by means of flow-sound separation algorithm based on immersed boundary method. Firstly, the incompressible complicated flow field was solved on the basis of immersed boundary method, and the flow field parameters were obtained as the input values. Then, the linear compressible perturbation equation was solved to simulate generation and travel of acoustic waves. This method was used to predict the noise of flow past two circular cylinders in tandem arrangements and the aerodynamic noise of the rudimentary landing gear. The numerical simulation was then compared with the corresponding experiments, and results were consistent. That showed the algorithm proposed was feasible
Analysis of vibration reduction for brake judder based on vibration transmission path
Get PDFThis paper presents a technique for minimizing vibrations of the steering wheel from vibration transmission path based on the method of shift frequency vibration reduction. At first, a road experiment was conducted on a vehicle with brake judder. Transmission path and excitation frequency of the vibration were determined through analyzing the experimental data. Then, modal analysis on the whole structure of the steering wheel was carried out by the finite element method. In this way, its inherent frequencies and modes could be obtained. In order to verify the accuracy of the finite element model, the modal experiment was carried out and its results were compared with the simulated one. Sensitivity analysis and optimization design were carried out on the fixation support of the steering wheel by using Optistruct in Hyperworks. In this way, the inherent frequency of the whole structure could avoid the excitation frequency. Finally, an experimental verification was also carried out on the vehicle, and the results show that the vibration acceleration value of the steering wheel reached the allowable value. The technique for minimizing vibrations of the steering wheel is feasible in this paper
Bearing fault diagnosis based on active learning and random forest
Get PDFBearing plays an important role in rotating machineries and has received increasing attention in diagnosis of its faults accurately. This paper proposes a fault diagnosis approach exploiting active learning (AL) based on random forest (RF), which can perform accurate bearing fault diagnosis with most valuable samples. First, feature vectors are obtained by empirical mode decomposition (EMD) process for original vibration signals and selected as input of the system. Second, samples with highest uncertainty are selected through AL and added to the training set to train RF classifier. Finally, trained RF is employed to perform classification for bearing faults with testing set. Experimental results demonstrate that the proposed approach can effectively and accurately identify typical bearing faults
Dynamic analysis in a micro drilling process with ultrasonic vibration
Get PDFIn recent years, the processing technology of advanced machinery has toward precision, high-performance, and high-speed. Therefore micro-fabrication becomes more important such as the getting smaller aperture in the printed circuit board (PCB), it tends to be more severe due to vibration. The vibration has adverse effects to machining accuracy and surface roughness which will increase tool abrasion and further accelerate the destruction from material fatigue. There are many ways to produce perforations, such as laser micro-machining and micro-drilling. The industry still adopts micro drill piercing process due to the cost and technical considerations. In order to enhance the cutlery life and the quality of the drilling process, the cutting characteristic of bur is important. Hence, the vibration during drilling must be suppressed. This study is to investigate the dynamic analysis of a micro drill under ultrasonic vibration (50 kHz) excited with a piezoelectric-driven actuator experimentally and numerically by using finite element analysis. The results show that the vibration and the cutting forces are effectively reduced and thereby the cutting performance is improved when introduces ultrasonic vibrations during micro-drilling process
Research of dynamic effects in the process of operation of linear comparator
Get PDFTopicality of the problem is the fact that in the process of increasing the quality of line scale gage calibration vibrations have substantial influence. In order to assess vibration influence we need to solve a lot of science and engineering tasks. To accomplish mathematical analysis we confronted with a lot of difficulties in creating of the analytical model and in finding of the values of coefficients. For this solution we need to make thorough analysis of the means for line scale measurements, because most of the coefficients we could only find by making experimental measurements and processing of their results
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
Pharmacognostic study of Clematidis armandii the determination of index components
Get PDFObjective: to provide definite science bases for its accurate identification and quality control. Methods: comparative identification on the stem, petiole and leaf of the two original plants of Clematidis armandii Caulis was carried out by the classical paraffin technique. Explore the index component for identification of Clematidis armandii Caulis by TLC and establish the quantitative analysis method by HPLC. Results: the rattan stems of Clematidis armandii Caulis, originated from Clematis armandii Franch and Clematis montana Buch.-Ham., are similar. However, they can be differentiated from each other by the structure of vascular bundle. Moreover, the structure of petiole are entirely different. The characteristic spots of beta-sitosterol in Clematidis armandii Caulis from six different places were detected by TLC. HPLC is high accurate, good reproductive, the mass concentration of beta-sitosterol in Clematis armandii Franch. was 189.18-190.27 μg·g-1 and in Clematis montana Buch.-Ham. was 336.90-338.34 μg·g-1. Conclusion: the spots were apparent and effective separated, when we used trichloromethane-ethyl acetate (10:1) for development, 10 % vitriol ethanol to color, and detected under the UV light (365 nm). This could be the TLC identification condition of beta-sitosterol in Clematidis armandii Caulis. Calculated on dry product by HPLC, the beta-sitosterol in Clematidis armandii Caulis could not be less than 0.018 %
Design verification of stress and sag for 500 kV transmission line
Get PDFTransmission line stress directly affects the tower sag force structure and a safe distance from the safe operation of the transmission lines play a crucial role. Calculation method for the preparation of the design process were complied, simply enter transmission liner parameters can be automatically obtained stress and sag. According to a 500 kV transmission line tests carried out stress sag design verification, checking ground found stress design errors and were corrected to ensure the safety of the project. Calculation program can be developed for different voltage levels for line stress on cables sag design verification
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