Papers by Author: L. Zhou

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Authors: Hong Bo Wang, Ying Xue Yao, L. Zhou
Abstract: A viscometer based on velocity attenuation of rotating cylinder is presented in the paper. A solid rotor motor drives the cylinder immersed in liquid in a cup to a scheduled velocity. The electricity supply of the motor is cut, the velocity of the cylinder with rotor of the motor attenuates with time because of viscous torque and other resistance torque. The velocity is measured by optical encoder. Viscosity of the fluid was calculated by a computer. Experiments are carried out and results show that deviation of viscosity beyond 1000 mPa•s are below 3%. The viscometer can be used in measurement of viscosity beyond 1000 mPa•s in industry.
Authors: L. Zhou, Yong Ze Guo, Z.R. Liao, X.R. Liang, G.Q. Pan
Abstract: Comparing advantages and disadvantages of Oliver-Pharr method, microhardness method and indentation energy method, this article propses the improvement of indentation energy method. The improvement of indentation energy method mainly takes the calculation of energy and pile-up and sink-in phenomenon into account. Using Abaqus to simulate the indentation of aluminum with Vicker indenter, process and analyse data from simulation . By comparing different methods of hardness calculation , analyse the effect of improvement of hardness calculation.
Authors: Qiang Liu, Ying Xue Yao, L. Zhou
Abstract: Nano-hardness test device has the ability to make the load-displacement measurement with sub-nanometer indentation depth sensitivity, and the nanohardness of the material can be got from the load-displacement curve by Oliver-Pharr method. In order to measure the small displacement accurately, we designed a capacitive displacement measuring system. This capacitance micrometer has a resolution of 0.1nm, and is suitable for our nano-hardness test device.
Authors: L. Zhou, Qiang Liu, Ying Xue Yao
Abstract: A piezoelectric ceramic power supply with self-feedback adjustment was developed according to piezoelectric ceramic driver’s characteristic. It uses multi dc voltages connected in series as the high voltage supply circuit, and has many advantages, such as small ripple, high precision, high driving capability, quick response and so on.
Authors: L. Zhou, H.B. Zhang, Qiang Liu
Abstract: In order to meet the demands for high precise micro-displacement testing, a differential capacitive displacement sensor based on RC multi-oscillating circuit was designed. It has two couples of polar plates, and gets the displacement by testing frequency through the multi-oscillating circuit. This capacitive sensor has many advantages such as simple structure and testing circuit, high resolution and good stability.
Authors: L. Zhou, H.B. Zhang, Qiang Liu
Abstract: For the measurement of ultra smooth surface topography, a surface image scanning device measurement head mechanism based on the principle of atomic force microscope (AFM) was designed. It uses coarse adjustment, semi-delicate adjustment, delicate adjustment triple-stage adjustment mechanism, and tests the atomic force between the sample and the probe by using laser generator, position sensitive detector (PSD), cantilever and probe. This mechanism has high setting accuracy and resetting accuracy, combined with two-dimension movable table, can scan the surface topography of samples.
Authors: H.B. Zhang, L. Zhou, Ying Xue Yao
Abstract: For rigid rotor that widely applied in gyroscopes, high precision dynamic balance is very important. The paper introduces a dynamic balance method for drum-shape gyroscope rotor: the rotor is supported by gas bearing; detecting the displacement of three points on the drum-shape rotor’s end-plane, obtaining its normal direction. Then according to geometrical relation of geometric axis and polar inertia axis, the dynamic trace of the rotor can be obtained, and the rotor’s mass imbalance is calculated. Experiment result shows that the method has high balance accuracy, particularly suit for high-speed gyroscope rotor whose mass imbalance is small.
Authors: L. Zhou, Ying Xue Yao, Qiang Liu
Abstract: Aiming at the influence law of indenter tip radius to indentation hardness, testing on the hardness of single-crystal silicon was carried out based on nanoindentation technique. Two kinds of Berkovich indenter with radius 40nm and 60nm separately were used in this experiment. According to the load-depth curve, the hardness of single-crystal silicon was achieved by Oliver-Pharr method. Experimental results are presented which show that indenter tip radius influence the hardness, the hardness value increases and the indentation size effect becomes obvious with the increasing of tip radius under same indentation depth.
Authors: Ying Xue Yao, Dong Li Qin, L. Zhou
Abstract: The influence of parameters to load performances of a high-speed externally pressurized spherical gas bearing compensated by two-rows of orifices has been studied numerically based on finite element method (FEM). Reynolds equation governing the flow field in the clearance space in spherical coordinates system is transformed into a analogous style in Descartesian coordinates by parameter substitution, and Galerkin weighted residual method is applied to reduce the order of derivatives of the transformed equation. Pressure distribution on the gas-film is obtained by solving of the equation. On the basis of theories, influences of rotating speed, nominal gas-film thickness and supplying pressure to load carrying capacity and stiffness are analyzed. Comparison of performances between hydrostatic and hybrid state of the bearing has also presented.
Authors: H.B. Zhang, L. Zhou, Ying Xue Yao, Dong Li Qin
Abstract: Because of many advantages that other kinds of bearings can not match, for example high precision and high speed, gas lubricated bearing has been used widely in areas such as ultra-precision machine tool and inertia apparatus. The paper introduced an orifice restrictor externally pressurized spherical gas bearing, which is easily shaped and has bigger stiffness in both axial and radial directions. The paper also introduced a bearing force calculation model based on finite partition of the bearing, in which the influence of the uniform pressure slot also considered.
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