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Analysis of sliding electric contact characteristics in augmented railgun based on the combination of contact resistance and sliding friction coefficient

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Defence Technology（防务技术） 2020年第4期16卷 747-752页

作者： Chun-yan Zhu Bao-ming Li National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyChina

The contact resistance between the armature and rails is an important indicator of the contact characteristics in electromagnetic launches.As the contact resistance depends not only on the contact state but also on the contact stress and temperature,there are some limitations in analyzing the contact characteristics using only the contact resistance.In this paper,the contact characteristics of the augmented railgun are analyzed by the combination of contact resistance and sliding friction coefficient.Firstly,the theoretical calculation model of the contact resistance and friction coefficient of the augmented electromagnetic railgun is established.Then the contact resistance and friction coefficient are calculated by the measured values of the muzzle voltage,rail current and armature displacement.Finally,the contact characteristics are analyzed according to the features of the waveforms of the contact resistance and the friction coefficient,and the analysis conclusions are verified by experimental rail images.The results showed that:the aluminum melt film gradually formed on the contact surface reduces the contact resistance and the friction coefficient;the wear and erosion of the armature cause deterioration of the contact state;after the transition,the reliability of the sliding contact between the armature and rails decreases,resulting in an increase in contact resistance.

关键词： Augmented railgun contact resistance Friction coefficient contact characteristics

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Three-Dimensional Conjugate Tooth Surface Design and contact Analysis of Harmonic Drive with Double-Circular-Arc Tooth Profle

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Chinese Journal of Mechanical Engineering 2023年第5期36卷 248-265页

作者： Chaosheng Song Feihong Zhu Xinzi Li Xuesong Du State Key Laboratory of Mechanical Transmissions Chongqing UniversityChongqing 400030China

A three-dimensional conjugate tooth surface design method for Harmonic Drive with a double-circular-arc tooth profle is proposed. The radial deformation function of the fexspline (FS), obtained through Finite Element (FE) analysis, is incorporated into the kinematics model. By analyzing the FS tooth enveloping process, the optimization of the overlapping conjugate tooth profle is achieved. By utilizing the hobbing process, the three-dimensional machinable tooth surface of FS can be acquired. Utilizing the coning deformation of the FS, simulations are conducted to analyze the multi-section assembly and meshing motion of the machinable tooth surface. The FE method is utilized to analyze and compare the loaded contact characteristics. Results demonstrate that the proposed design method can achieve an internal gear pair consisting of a circular spline with a spur gear tooth surface and the FS with a machinable tooth surface. With the rated torque, approximately 24% of the FS teeth are engaged in meshing, and more than 4/5 of the tooth surface in the axial direction carries the load. The contact patterns, maximum contact pressure, and transmission error of the machinable tooth surface are 227.2%, 40.67%, and 71.24% of those on the spur gear tooth surface, respectively. It clearly demonstrates exceptional transmission performance.

关键词： Three-dimensional conjugate tooth surface Coning deformation Double-circular-arc tooth profle Harmonic Drive contact characteristics

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Spherical contact mechanical analysis of roller cone drill bits journal bearing

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Petroleum 2016年第2期2卷 208-214页

作者： Wei He Yang Chen Junchao He Weiling Xiong Tong Tang Hao OuYang School of Mechatronic Engineering Southwest Petroleum UniversityChengdu 610500China Sichuan Special Equipment Inspection Institute Chengdu 610061China

Fang contact model is introduced to analyze stress of the spherical fixed ring journal bearing.Developed calculation programs in the MATLAB software which are utilized to calculate the contact characteristics of roller cone drill bits spherical fixed ring journal bearing.In addition,effects of external load,radius clearance values,and material parameter on the mechanics performance were investigated.The results show that the value of external load has a direct pronounced effect on the contact characteristics of journal bearing.There is a significant positive correlation between contact pressure and external load,radius clearance value,and the Young's modulus of material.However,there is an evident negative correlation between contact radius of journal bearing and radius clearance value,and the Young's modulus of material.The smaller radius clearance value of journal bearing is,the more centralized contact region will be,so the corresponding contact pressure will be higher.From the perspective of reducing friction and wear,we need select the materials which have high strength and good toughness.Not only might this can improve the wear resistance,it also effectively decreases the contact pressure.In this case,we can prolong the service life of roller cone drill bits journal bearing.

关键词： Roller cone drill bits Journal bearing Spherical fixed ring contact characteristics

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