Ventilation system analysis for underground mines has remained mostly unchanged since the Atkinson method was made popular by Mc Elroy in 1935. Data available to ventilation technicians and engineers is typically limi...Ventilation system analysis for underground mines has remained mostly unchanged since the Atkinson method was made popular by Mc Elroy in 1935. Data available to ventilation technicians and engineers is typically limited to the quantity of air moving through any given heading. Because computer-aided modelling, simulation, and ventilation system design tools have improved, it is now important to ensure that developed models have the most accurate information possible. This paper presents a new technique for estimating underground drift friction factors that works by processing 3 D point cloud data obtained by using a mobile Li DAR. Presented are field results that compare the proposed approach with previously published algorithms, as well as with manually acquired measurements.展开更多
As the power transmission system of an aircraft,a hydraulic pipeline system is equivalent to the " blood vessel" of the aircraft. With the development of aircraft hydraulic system to high pressure,high speed...As the power transmission system of an aircraft,a hydraulic pipeline system is equivalent to the " blood vessel" of the aircraft. With the development of aircraft hydraulic system to high pressure,high speed and high power ratio,the fluid-structure interaction vibration mechanism of hydraulic pipeline is more complex and the influence of friction coupling on vibration cannot be ignored. The fluid-structure interaction of hydraulic pipeline will lead to system vibration,lower reliability of system operation and even pipeline rupture. Taking a hydraulic pipeline of C919 aircraft wingtip as the research object,a 14-equation model of fluid-structure interaction vibration considering friction coupling effect is established in this paper. The effects of friction and fluid parameters on the pipeline fluid-structure interaction vibration characteristics are studied and verified by experiments. The research results will provide theoretical guidance for the analysis of the pipeline fluid-structure interaction vibration and have important theoretical significance and great engineering value for promoting the localization process of large aircraft.展开更多
Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinf...Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.展开更多
A series of functionalized ionic liquids （ILs） containing ester-group were synthesized and their tribological prop- erties as lubricants for steel-steel contact were studied and compared with a non-functionalized io...A series of functionalized ionic liquids （ILs） containing ester-group were synthesized and their tribological prop- erties as lubricants for steel-steel contact were studied and compared with a non-functionalized ionic liquid and perfluo- ropolyethers （PFPE）. The morphology and chemical composition of the worn scars were analyzed by scanning electron mi- croscopy and X-ray photoelectron spectroscopy, respectively, and the possible lubrication mechanism of ILs was discussed. As a result, all ILs demonstrated a better lubricity and a much higher load-carrying capacity than PFPE used as lubricants for the steel-steel tribomates system. The functionalized ILs with ester-group showed slightly worse friction reducing abil- ity than their nonfunctionalized counterparts at relatively lower loads owing to their higher viscosity, but then exhibited better antiwear ability because the ester group they contained had not only physical but also strong chemical reactions with the freshly exposed steel surface and formed chemical adsorption boundary films on the worn surface during friction pro- cess. Under high loads, some triboehemical reactions took place between the active elements, such as fluorine which were released from the ILs, and fresh metal surfaces of rubbing pairs to form the admixture reaction films, which were mainly composed of ferric fluoride mixed with ferric oxide, leading to lower friction coefficients and good wear resistance.展开更多
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 non...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.展开更多
基金supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) under grant CRDPJ 44580412Barrick Gold Corporation and Peck Tech Consulting Ltd
文摘Ventilation system analysis for underground mines has remained mostly unchanged since the Atkinson method was made popular by Mc Elroy in 1935. Data available to ventilation technicians and engineers is typically limited to the quantity of air moving through any given heading. Because computer-aided modelling, simulation, and ventilation system design tools have improved, it is now important to ensure that developed models have the most accurate information possible. This paper presents a new technique for estimating underground drift friction factors that works by processing 3 D point cloud data obtained by using a mobile Li DAR. Presented are field results that compare the proposed approach with previously published algorithms, as well as with manually acquired measurements.
基金Supported by the National Key Basic Research Program of China(No.2014CB046405)
文摘As the power transmission system of an aircraft,a hydraulic pipeline system is equivalent to the " blood vessel" of the aircraft. With the development of aircraft hydraulic system to high pressure,high speed and high power ratio,the fluid-structure interaction vibration mechanism of hydraulic pipeline is more complex and the influence of friction coupling on vibration cannot be ignored. The fluid-structure interaction of hydraulic pipeline will lead to system vibration,lower reliability of system operation and even pipeline rupture. Taking a hydraulic pipeline of C919 aircraft wingtip as the research object,a 14-equation model of fluid-structure interaction vibration considering friction coupling effect is established in this paper. The effects of friction and fluid parameters on the pipeline fluid-structure interaction vibration characteristics are studied and verified by experiments. The research results will provide theoretical guidance for the analysis of the pipeline fluid-structure interaction vibration and have important theoretical significance and great engineering value for promoting the localization process of large aircraft.
基金Project(51165022)supported by the National Natural Science Foundation of ChinaProject(20122117)supported by the Lanzhou Science and Technology Bureau Foundation,ChinaProject(1310RJZA036)supported by the Natural Science Foundation of Gansu Province,China
文摘Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.
基金the Natural Science Foundation Project of CQ CSTC, 2010BB0201
文摘A series of functionalized ionic liquids （ILs） containing ester-group were synthesized and their tribological prop- erties as lubricants for steel-steel contact were studied and compared with a non-functionalized ionic liquid and perfluo- ropolyethers （PFPE）. The morphology and chemical composition of the worn scars were analyzed by scanning electron mi- croscopy and X-ray photoelectron spectroscopy, respectively, and the possible lubrication mechanism of ILs was discussed. As a result, all ILs demonstrated a better lubricity and a much higher load-carrying capacity than PFPE used as lubricants for the steel-steel tribomates system. The functionalized ILs with ester-group showed slightly worse friction reducing abil- ity than their nonfunctionalized counterparts at relatively lower loads owing to their higher viscosity, but then exhibited better antiwear ability because the ester group they contained had not only physical but also strong chemical reactions with the freshly exposed steel surface and formed chemical adsorption boundary films on the worn surface during friction pro- cess. Under high loads, some triboehemical reactions took place between the active elements, such as fluorine which were released from the ILs, and fresh metal surfaces of rubbing pairs to form the admixture reaction films, which were mainly composed of ferric fluoride mixed with ferric oxide, leading to lower friction coefficients and good wear resistance.
基金the National Natural Science Foundation of China (Grant Nos. 50975056 and 11072066)the Scientific Research Foundation of Harbin Institute of Technology at Weihai (Grant No. HIT(WH)XB201120)the Fundamental Research Funds for the Central Universities (Grant No. HIT.NSRIF.2013122)
文摘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.
