Papers by Author: Zhi Li Sun

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Authors: Yu Tao Yan, Mai Yang, Zhi Li Sun, Li Fang Liu
Abstract: The formation and lubrication mechanism of boundary lubricating film were discussed. The boundary lubricating film includes adsorption film and chemical reaction film, and has respective temperature operating range. The adsorption film adsorbed in metal surface by Van-der Wads, and the parenchyma is the external friction between adsorption molecule layers. The chemical reaction film is made by the reaction between metal and extreme pressure additive in base oil, and the anti-wear capability is realized by the low-melting point eutectic alloy. The temperature is regarded as a judge criterion for failure of boundary lubrication. The failure model for boundary lubricating film is established. According to the failure model, the failure criterion proposed is effective by analysis of the spiral bevel gear using the finite element method. These results provide a basis for the application of boundary lubrication.
Authors: Yu Tao Yan, Zhi Li Sun, Guang Wei Hu
Abstract: The wear experimental project on main influencing factor with load, sliding speed, surface hardness and lubrication was instituted by the uniform design, the wear properties were investigated on a MMW-1 friction and wear tester. The predication formula for wear rate was defined. The wear rate predication model was established by the partial least squares based on the test data, the influencing degree on the main influencing factors was analyzed, the results show the influence on wear rate from big to small is in turn load, lubrication, surface hardness and sliding speed. The lubrication property improved is a handy valid path to decrease the wear rate. The check results show that it is a valid method by partial least squares to establish wear predication model based on test data.
Authors: Dong Tao Xu, Zhi Li Sun, Yong Ying Du
Abstract: Aimed at three-translational parallel mechanism, the velocity Jacobian matrix is formulated on the basis of analytical method, so the velocity and acceleration of the moving platform is calculated. Then the velocity and acceleration formulas of all components’ centroids are deduced based on the vector method. The above formulas are very simple and easy to solve. Kinematic simulation is carried out by ADAMS virtual prototyping software. The operating data is obtained, it verifies the correctness of the theoretical calculation.
Authors: Shi Chao Xiu, Shi Qiang Gao, Zhi Li Sun
Abstract: Hybrid journal bearings are used in the high and super high speed cases mainly, such as the super-high speed spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of the bearing is a major reason to lower the accuracy of the main shaft system and limit the bearings working speed higher, as a result, restrict the bearing applications. In this paper, the thermal properties and the heat mechanism of such bearings are analyzed. The mathematical model of hybrid journal bearing is established to analyze the mechanism of generating heat. In addition, the temperature field distribution for the certain hybrid journal bearing at speed of 10000 rpm is studied by means of software ANSYS considering the heat transfer characters between fluid and solid. An improved measure about temperature rise of hybrid journal bearing is presented.
Authors: Cui Ling Li, Dan Dan Jia, Zhi Li Sun
Abstract: Most current common cause failure models are static models in which failure rate is assumed constant. The assumption is unrealistic in numerous situations, especially for mechanical systems. Based on the idea of shock models, this paper modifies unreasonable assumptions in conventional models and describes common cause failure process with non-homogeneous Poisson process, power-exponential process. A dynamic model is obtained. The parameters are estimated with neural network. The model presented in this paper, which is based on time-related power-exponential failure rate like bathtub curve, has more advantages and wider application than the model based on constant failure rate. Examples are given to illustrate its feasibility and precision of computation.
Authors: Zhi Li Sun, Yun Feng Zhang, Yu Tao Yan
Abstract: The wear volume is obtained by means of experiment and the wear random process model is established according to the result. The Carbon steel material is used and the samples are grouped five after surface treatment, each group tests six times under the same condition. The wear volume under each wear time shows big dispersion. The additional study indicates that the sample has the large wear volume is in the serious wear state from the beginning, and the wear of running-in phase is inflected by the work velocity and the state condition of the surface of the samples. The wear process which the mean value is a constant and the standard deviation is different is a normal process generally, it is a stationary normal process if the standard deviation has no relation to the start of the wear time, or a Wiener process if the standard deviation is liner with the wear time, it is valuable to forecast the wear reliability.
Authors: Dong Tao Xu, Zhi Li Sun, Jia Lian Shi
Abstract: This paper presents a novel, precision, maneuverable, 3-DOF translational parallel mechanism. The mechanism’s important feature is that all of the kinematic joints are the revolute joints. The paper derives the mechanism’s kinematic forward solution and inverse solution by using of coordinate transformation elimination method and vector method, and establishes proper kinematic modeling. Kinematic simulation is carried out by ADAMS virtual prototyping software. The operating data is obtained, it verifies the correctness of solving the forward and inverse solution, and solve the question of choices for many results during the theoretical solution. This technique can provide a useful tool in the design of kinematic trajectory of the parallel mechanism’s end-effector and the kinematic analysis of other parallel mechanism.
Authors: Qiang Yang, Zhi Li Sun, Yan Yan Shi, Dan Dan Jia, Yu Tao Yan
Abstract: Five-axis CNC machine tool is the top product of numerically controlled machine tool. Kinmatic accuracy is an important index to evaluate the quality of mechanism. Kinematic accuracy analysis of the Five-axis machine tool in previous study ignores the randomness of each input error component, so the conclusions are imprecise. Using the homogeneous transformation, inverse kinematics of VMC650 Five-axis machine tool is calculated. Based on Multi-body System Theory, error model of the machine tool is presented. Considering the randomness of every input error components, applying the Monte Carlo method, math model of kinematic reliability of the mechanism is deduced. The calculation method of kinematics reliability are put forward applying point evaluation and track evaluation. Kinematic reliability analysis provides some theoretical reference for improving the machining accuracy and operation life of machine tool.
Authors: Qiang Yang, Zhi Li Sun, Dong Liang Lei, Peng Zhou
Abstract: Kinematic accuracy is an important index to evaluate the quality of mechanisms. Kinematic reliability is a significant standard to examine dynamic kinematic accuracy of mechanisms. Having deduced inverse kinematics and calculated model for position errors of Delta mechanism, kinematic reliability of the mechanism is calculated considering the randomness of every error components. Analytic method sensitivity analysis is adopted to describe contribution of the randomness of each error component to kinematic reliability of the mechanism, and the calculating approach is exactly given that the sensitivity analysis which is for getting the error contributions to reliability of which the position errors during movement is in the range of allowable accuracy at any time. Kinematic reliability and its sensitivity analysis can search key factor influencing kinematic accuracy, which can provide the foundation for error compensate and accuracy assurance technology of the mechanism.
Authors: Yu Tao Yan, Zhi Li Sun, Qiang Yang, Yan Zhong Wang
Abstract: The spiral bevel gears of attack helicopter transmission systems are taken as an object in this paper. The numerical analysis model for starved elastohydrodynamic lubrication (SEHL) of spiral bevel gears is established on the basis of the analysis of load tooth contacts analysis and SEHL in elliptical contacts. The SEHL characteristics of spiral bevel gears are also analyzed. The results are as follows: during the course of a gear-tooth meshing cycle of the spiral bevel gear, the extremum of minimal film thickness and maximal film pressure occurs near midpoint of the path of contact, and leans to dedendum. The minimal value of the minimal film thickness is 0.39 um, and the maximal value of the maximal film pressure is 0.69 GPa. The value of minimal film thickness gradually increases with the increasing of meshing point velocity. When the velocity of meshing point exceeds 110 m/s, the increase became tardiness. As the load of meshing point increases, the value of minimal film thickness gently diminishes.
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