检索结果-南通市图书馆

A new visco-elastic contact model of traveling wave ultrasonic motor with stator frictional layer

在线全文

学校读者我要写书评

暂无评论

Journal of Harbin Institute of Technology(New Series) 2007年第5期14卷 705-710页

作者：孙凤艳曲建俊吴培莲 Dept. of Mechanical Engineering Harbin Institute of Technology School of Material Science and Engineering Harbin Institute of Technology

A new contact model of traveling wave ultrasonic motor （TWUSM） with a visco-elastic stator frictional layer was presented. In this model, the initial boundaries were revised, and the rotor revolution speed could he calculated iteratively. This model was compared with compliant slider and rigid stator model. The results of motor characteristics simulations showed that the motors based on this model would gain bigger stall torque. Then the friction and wear characteristics of two models were analyzed. The motors based on this model had lower coefficient of friction and better wear resistance.

关键词： ultrasonic motor contact model frictional material

Elastoplastic contact Mechanics model of Rough Surface Based on Fractal Theory

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2017年第1期30卷 207-215页

作者： YUAN Yuan GAN Li LIU Kai YANG Xiaohui School of Mechanical and Precision Instrument Engineering Xi'an University of Technology School of Mechanical Engineering Xi'an Jiaotong University

Because the result of the MB fractal model contradicts with the classical contact mechanics, a revised elastoplastic contact model of a single asperity is developed based on fractal theory. The critical areas of a single asperity are scale dependent, with an increase in the contact load and contact area, a transition from elastic, elastoplastic to full plastic deformation takes place in this order. In considering the size distribution function, analytic expression between the total contact load and the real contact area on the contact surface is obtained. The elastic, elastoplastic and full plastic contact load are obtained by the critical elastic contact area of the biggest asperity and maximun contact area of a single asperity. The results show that a rough surface is firstly in elastic deformation. As the load increases, elastoplastic or full plastic deformation takes place. For constant characteristic length scale G, the slope of load-area relation is proportional to fractal dimension D. For constant fractal dimension D, the slope of load-area relation is inversely proportional to G. For constant D and G, the slope of load-area relation is inversely proportional to property of the material ~b, namely with the same load, the material of rough surface is softer, and the total contact area is larger. The contact mechanics model provides a foundation for study of the friction, wear and seal performance of rough surfaces.

关键词： rough surfaces asperities fractal theory contact model

Material characterization and inter/intra-particle validation for DEM simulation of urea coating process

在线全文

学校读者我要写书评

暂无评论

Particuology 2024年第5期88卷 32-48页

作者： Salma A.Nouh KuZilati KuShaari Lau Kok Keong Shafirah Samsuri Chemical Engineering Department Universiti Teknologi PETRONAS32610 Seri IskandarPerak Darul RidzuanMalaysia

Particle coating is a common operation in the controlled-release fertilizer (CRF) industry,where a coating layer is appliedto the urea cores.A discrete element method (DEM) computer simulation was applied to model the coating process for the urea granules using measured model *** accuracy of DEM input parameters for the coating material properties and the physical and mechanical characterizations of urea granules are crucial to the study of particle coating ***,to enhance the simulation accuracy,information on the material properties (urea granules) is *** this study,the elasticity parameters,shear modulus ,coefficient of restitution (CoR),and coefficient of rolling and static friction (CoRF) and (CoSF) of urea granules are estimated experimentally in addition to the physical *** sensitivity of the angle of repose of the urea bed was investigated at different coefficients of *** to the obtained experimental value of the angle of repose,values of 0.2 and 0.3 for CoRF and CoSF,respectively,were adjusted to obtain consistent urea granules’ motion for simulation and the ***,the spray droplet sizes and velocity distributions were estimated using the video-imaging process *** on this experimental characterization,elasticity parameters and spray properties were integrated into DEM simulation software as input data to perform numerical analysis of the coating process to compare simulation and experimental results,which show uniformity at three different pan speeds with a maximum deviation of 0.033 at 5 ***,consistency between DEM and experiment results was achieved in terms of average coating thickness (μm) of the selected samples and average intra-particle thickness variation ( CoV intra ).These results revealed that the coating film thickness is proportional to the rotation speed for the experiment and *** enhance the inter-particle coating uniformity,the effects of the

关键词： contact model Discrete element method Urea fertilizer Coating process

Frictional characteristics of sheet metals with superimposed ultrasonic vibrations

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Central South University 2018年第8期25卷 1879-1887页

作者： CAO Miao-yan LI Jian-chao LIU Yan-yang YUAN Ya-ning ZHAO Chang-cai DONG Guo-jiang National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan UniversityQinhuangdao 066004China Chinese Academy of Agricultural Mechanization Sciences Beijing 100083China Key Laboratory of Advanced Forging&Stamping Technology and Science of Ministry of Education of China Yanshan UniversityQinhuangdao 066004China College of Vehicles and Energy Yanshan UniversityQinhuangdao 066004China

The forming performance of sheet metals in the deep-drawing process with ultrasonic vibrations can be improved by the surface effect between the sheet metal and the die.A sheet metal friction test with ultrasonic vibrations is performed to explore the cause of the surface *** frictional characteristics are investigated,and the corresponding friction expressions are established based on the contact mechanics and the elastic–plastic contact model for rough *** is caused by the elastic–plastic deformation of contacting asperities under normal *** actual contacting region between two surfaces increases with normal loads,whereas the normal distance *** normal distance between the contacting surfaces is changed,asperities generate a tangential deformation with ultrasonic vibrations,and the friction coefficient is eventually *** vibrations are applied on a 40Cr steel punch at the frequency of 20 kHz and the amplitude of 4.2μ*** the friction tests,the punch is perpendicular to the surface of the magnesium alloy AZ31B sheet metals and is sliding with a relative velocity of 1 mm/*** test results show that the friction coefficient is decreased by approximately 40%and the theoretical values are in accordance with the test values;Ultrasonic vibrations can clearly reduce wear and improve the surface quality of parts.

关键词： friction ultrasonic vibrations sheet metals contact model

A noncontact robot demonstration method with human supervision

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2021年第11期64卷 2360-2372页

作者： ZHANG Qi XIE ZongWu LIU Yang State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China

The widely used kinesthetic demonstration method of dragging robotic manipulators cannot obtain reliable information for autonomous robot manipulation because an additional external force rather than pure contact force will be reflected on the force sensor in end-constrained manipulation tasks. Therefore, a noncontact robot demonstration method with human supervision is proposed to avoid external influence. A human demonstrator sends motion commands by mouse and observes force data reflected in a monitor to protect the robotic manipulator. Simultaneously, the human demonstrator supervises the positionorientation relationship between the end-effector and the manipulated object. The wrench insertion task is adopted to illustrate the advantage of the proposed method. A contact model is established according to demonstration data acquired from the proposed demonstration method, and an orientation adjustment strategy is verified. The strategy verification experiment illustrates not only the effectiveness of the simplified contact model and corresponding strategy but also the advantage of the proposed demonstration method.

关键词： Robot demonstration contact model orientation adjustment

Landslide dynamic process and parameter sensitivity analysis by discrete element method: the case of Turnoff Creek rock avalanche

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2020年第7期17卷 1581-1595页

作者： An Hui-cong Ouyang Chao-jun Zhao Chuan Zhao Wei Key Laboratory of Mountain Hazards and Earth Surface Processes Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu610041China CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing100101China University of Chinese Academy of Sciences Beijing100049China Sichuan Academy of Water Conservancy Chengdu610072China

The great diversity and complexity of geological hazards in terms of flowing materials,environment,triggering mechanisms and physical processes during the flow bring great difficulties to the numerical parameter selection for the discrete element *** order to identity the significance of individual parameters on the landslides dynamic process and provide valuable contribution to the runout analysis of similar landslide,the dynamic process and associated microscopic mechanism of the Turnoff Creek rock avalanche in Canada are *** present numerical results are compared with the field survey data and the results of depth-integrated continuum *** final deposit range matches well with the field survey *** is illustrated that the discrete element method is robust and feasible to capture the dynamic characteristics of large rock avalanche over a complex ***,a new method to assess the landslide hazard level based on the discrete element method is *** to the parameter sensitivity analysis,it is demonstrated that the basal friction coefficient and bond strength are essential to the final deposit while rolling coefficient and restitution coefficient have little effects on it.

关键词： Discrete element method contact model Numerical modeling Rock avalanche Geological hazard assessment Parameter analysis

contact Analysis and modeling of Standing Wave Linear Ultrasonic Motor

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2011年第6期26卷 1235-1242页

作者：时运来 State Key Laboratory of Mechanics and Control of Mechanical Structure Nanjing University of Aeronautics & Astronautics Digital Manufacturing Equipment and Technology National Key Laboratory Huazhong University of Science and Technology

A contact model for describing the contact mechanics between the stator and slider of the standing wave linear ultrasonic motor was presented. The proposed model starts from the assumption that the vibration characteristics of the stator is not affected by the contact process. A modified friction models was used to analyze the contact problems. Firstly, the dynamic normal contact force, interface friction force, and steady-state characteristics were analyzed. Secondly, the influences of the contact layer material, the dynamic characteristics of the stator, and the pre-load on motor performance were simulated. Finally, to validate the contact model, a linear ultrasonic motor based on in-plane modes was used as an example. The corresponding results show that a set of simulation of motor performances based on the proposed contact mechanism is in good agreement with experimental results. This model is helpful to understanding the operation principle of the standing wave linear motor and thus contributes to the design of these types of motor.

关键词： standing wave linear ultrasonic motor intermittent contact contact model

Wear analysis of revolute joints with clearance in multibody systems

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2013年第8期56卷 1581-1590页

作者： BAI ZhengFeng ZHAO Yang WANG XingGui Department of Mechanical Engineering Harbin Institute of Technology (Weihai) Department of Astronautic Engineering Harbin Institute of Technology

In this work, the prediction of wear for revolute joint with clearance in multibody systems is investigated using a computational methodology. The contact model in clearance joint is established using a new hybrid nonlinear contact force model and the friction effect is considered by using a modified Coulomb friction model. The dynamics model of multibody system with clearance is established using dynamic segmentation modeling method and the computational process for wear analysis of clearance joint in multibody systems is presented. The main computational process for wear analysis of clearance joint includes two steps, which are dynamics analysis and wear analysis. The dynamics simulation of multibody system with revolute clearance joint is carried out and the contact forces are drawn and used to calculate the wear amount of revolute clearance joint based on the Archard's wear model. Finally, a four-bar multibody mechanical system with revolute clearance joint is used as numerical example application to perform the simulation and show the dynamics responses and wear characteristics of multibody systems with revolute clearance joint. The main results of this work indicate that the contact between the joint elements is wider and more frequent in some specific regions and the wear phenomenon is not regular around the joint surface, which causes the clearance size increase non-regularly after clearance joint wear. This work presents an effective method to predict wear of revolute joint with clearance in multibody systems.

关键词： clearance joint contact model friction force wear multibody system

Discrete Element Simulation of Collision-Rich Dynamics of Wet Granular Flows Down an Inclined Channel

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2008年第S1期13卷 90-95页

作者：张慰慈谢尚贤杨馥菱陈俊杉 Department of Civil Engineering Taiwan University Department of Mechanical Engineering Taiwan University

This paper proposes a numerical scheme that employs the discrete element method (DEM) to simulate the motion of a wet granular flow down an inclined channel. To account for the liquid influences on the dynamics between paired particles, this paper presents a wet soft-sphere contact model with liquid-modified parameters. The developed scheme takes full advantage of DEM and avoids the expensive simulation of the solid-liquid interactions with conventional Navier-Stokes equation solver. This wet contact model has been implemented in an in-housed parallel discrete objects simulation system — KNIGHT and ANNE/IRIS to compute the dynamic behaviors of both dry and wet granular particles flowing down an inclined channel.

关键词： discrete element method wet granular flow contact model interaction model