Abstract: An elaborated mechanism for sheath flow forming includes flow cell, vacuum pool, sample pool, syringes, valves, and tubes. Firstly the sample is drawn into the sample inlet of flow cell through vacuum generated with one syringe. Then, the sample and buffer are driven to pass the flow cell to form sheath flow by other two syringes. To visualize and evaluate the sheath flow, black ink is used as sample, and optical imaging system is adopted to capture the formed sheath flow. Sheath flows with sample width of 21μm and 37μm in diameter are formed in a flow cell with micro-square hole of the size 0.2mm×0.2mm when the syringes run in different speed.
Abstract: This paper proposes a new method of motor fault analysis. Gershgorin Disk is proposed as a key technique for processing all the 3 stator phase currents. Gershgorin Disk is broadly applied to estimate sources with unknown signal numbers. This paper introduces the technique for motor fault analysis. The method is expected to provide a high accuracy method of fault analysis. The Gershgorin Disk is tested with a source of 3 sinusoidal stator phase currents under different conditions. There are 3 different motor conditions: healthy, stator fault, and rotor fault motor at full load condition. Based on experiments, the method can show differentiation of motor conditions with high accuracy. They seem also to be able to indicate fault severity levels by observing radii and center of among the disks.
Abstract: Vehicle under braking in turn condition can easily cause lateral instability because of the centrifugal force. In this paper, the defects of ABS control methods of the vehicle under braking in turn condition were analyzed, a braking force control strategy by the integrated control of ABS and yaw moment control for vehicle cornering is presented. Based on ABS, a yaw moment controller using fuzzy control theory is designed, by controlling yaw moment of vehicle and regulating slip rate of wheels, the dynamic regulation of yaw moment in vehicle braking is realized, therefore, vehicle braking stability on turning lane is improved. A simulation is performed with it during two different conditions: step input and sinusoidal input, the results showed that the transient and steady response based on presented method is better than that of ABS only, and the presented method can effectively control the yaw rate and side slip angle synchronously, achieve good transient and steady response, lighten the burden of the driver and improve vehicle yaw stability.
Abstract: This paper studied the relationship among the linear model of wheel/rail characteristic parameters, the contact angle difference, the equivalent conicity and roll angle. The standard and worn profiles of S1002CN, XP55 and LMA were matched with 60 kg/m rail separately. The results of the study show that the ratio of contact angle difference to equivalent conicity changes linearly along lateral wheelset displacement within 5mm. Taking rolling angle into consideration, the contact angle difference and equivalent conicity in nominal position (3mm) display a linear relationship. Just considering the contact angle difference and roll angle in the fitting formula for the wheel/rail linear model calculation, the quasi-linear calculation of the critical speed could be more accurate. Therefore, the wheel/rail linear model characteristic parameters roll angle and the contact angle difference in the nominal position have certain effect on vehicle dynamic performance like equivalent conicity.
Abstract: The noise of the test system in the vibration test,is an important factor affecting the test results.This paper first introduce the classification of the sources of noise in the vibration test system,and explain the ways of noise interference and how to reduce the noise interference.Then given the specific measures to reduce the noise in the vibration test system,which can improve the precision and reliability of results of vibration test system.The paper has a certain significance in reducing the vibration noise.
Abstract: Plate-shell structures, especially cylindrical shells and spherical shells, are widely used in engineering fields, such as aircraft and tanks, missiles, submarines, ships, hydraulic pumps, infusion pipelines and gas pipelines, and so on. These structures are usually in a fluid medium, which are related to the structure fluid-solid coupling and acoustic radiation field. As many experiments show that enclosed air in a thin walled structure, just like the violin, affects some modes of vibration significantly, air coupling between vibrating sides of the structure cannot be neglected. In order to explore the sound pressure distribution of vibrational frequencies, this paper, considering the material anisotropy, analyzes a typical complex shell structure of the violin by finite element method, including acoustic-structure coupling analysis and post-processing, especially sound pressure vibration frequency extraction. Finally, we get the conclusion that the distribution of sound pressure vibration frequency is similar to the normal distribution.
Abstract: When the front end of the supercavitating vehicles subjects to very large axial non-stationary random excitation at high speed motion under water, it is necessary to analyze dynamic responses of supercavitating vehicles under non-stationary random excitation. The dynamical equation of supercavitating vehicles is transformed into the form of state equations. The Simpson integration method is going to calculate the integral term of the general solution of state equation to improve the precise integration method. The explicit expression of dynamic responses of supercavitating vehicles is deduced, the means and variances of structural responses are calculated with operation laws of the first moment and second moment. Under different sailing speeds and different cone-cavitator angles dynamic responses of supercavitating vehicles are given by the examples, and the effectiveness of the method was demonstrated.
Abstract: Considering the encapsulation, tremendous working stress, complicated fault mechanism and process, an object-oriented architecture Prognostics and Health Management (PHM) system of Self-Propelled Gun is put forward to solve the difficulties in modern equipments’ maintenance decision and safeguard. The relative key techniques, such as fault characteristics extraction, system identification, data fusion among sensors, adaptive fault thresholds setting, intelligent fault inference mechanism and fault prediction mechanism are discussed in detail. Above functional modules compose the PHM system. Their mutual relationships and data flow are shown as architecture graph, which is the basis of PHM system establishment. Simulation verification experiments indicate that the proposed architecture can satisfy the requirements of standardization, hierarchy and evolvement, as well as reducing the maintenance cost and difficulties.
Abstract: The common requests of the meshless interpolating functions are researched, and its construction method and procedures using the moving least squares method are introduced. The point collocation method is adopted to discretize the Kirchhoff-Helmholtz boundary integral equations into equation groups that constrained by boundary conditions. Constrained equation groups are solved by matrix-division method finally. Therefore, the discrete numeric expression of acoustic radiating and transferring model is obtained. In the example, acoustic field is calculated by the acoustic radiating and transferring model that obtained through both BMLM and BEM, and the results are contrasted between the computational values and the true values. It shows that the interpolating functions of BMLM could be built more flexible. So the accuracy of interpolation and calculation by BMLM is higher.
Abstract: CFD developed rapidly in capability and practicality during past years. A lot of research works on numerical simulation of viscous flow field around ship were widely carried out in past decades. But the research of interference effect among the hull, rudder and propeller was rarely concerned. In this paper, based on an unsteady Reynolds Averaged Navier–Stokes method, the dynamic mesh methods(6DOF) are adopted to simulate straight line and oblique towing test of ship with twin propellers and twin rudders. And based on the simulation results, the interference coefficients, such as effective weak coefficient ωp, rudder’s effective longitudinal velocity uR, effective attack angle αR, rudder force’s modificatory factor αH for shiphandling derivational transverse force and its dimensionless distance to ship’s gravity point, are calculated. The computed results of this paper agree well with the experimental results carried out in the tower tank of ITTC. It shows that the methods on numerical calculation of Interference Coefficients between hull, rudder and propeller is successful.