The effects of the mechanical factors with applied loads on the tribological performance of refined,bleached and deodorised(RBD) palm stearin(PS) were studied using a four-ball tribotester.All the RBD PS results were ...The effects of the mechanical factors with applied loads on the tribological performance of refined,bleached and deodorised(RBD) palm stearin(PS) were studied using a four-ball tribotester.All the RBD PS results were simultaneously compared with the additive-free paraffinic mineral oil(PMO).The experiments were carried out using different loads with a constant speed in order to gain a better understanding of the mechanical processes that occurred during the experiment.For each experiment,the temperature was increased to 75 °C and was run for 1 h.In a mechanical system,lubricant plays an important role in reducing wear and friction.PS exists as a semi-solid at room temperature after the fractionation process from oil palm.Due to the increasing rate of pollution to the environment,vegetable oil was chosen as the test lubricant with regard to its biodegradability.Other advantages of vegetable oil are that it is more easily harvestable and non-toxic compared to petroleum-based oil,which made it a suitable candidate.From the experiment,RBD PS is found to have a better friction constraint reduction compared with additive-free PMO.展开更多
Tribology at cryogenic temperatures has attracted much attention since the 1950s with the acceleration of its applications in high-tech equipment such as cryogenic wind tunnels,liquid fuel rockets,space infrared teles...Tribology at cryogenic temperatures has attracted much attention since the 1950s with the acceleration of its applications in high-tech equipment such as cryogenic wind tunnels,liquid fuel rockets,space infrared telescopes,superconducting devices,and planetary exploration,which require solid lubrication for moving parts at low temperatures down to 4 K in cryogenic liquid,gaseous,or vacuum environments.Herein,the research progress regarding cryo-tribology is reviewed.The tribological properties and mechanisms of solid lubricants listed as carbon materials,molybdenum disulfide,polymers,and polymer-based composites with decreasing temperature are summarized.The friction coefficient increases with decreasing temperature induced by thermally activated processes.The mechanism of transfer film formation should be considered as a significant way to enhance the tribological properties of solid lubricants.In addition,applications of solid lubrication on moving parts under cryogenic conditions,such as spherical plain bearings and roller bearings,are introduced.The technology for tribological testing of materials and bearings at cryogenic temperatures is summarized,where the environmental control,motion and loading realization,as well as friction and wear measurement together in a low-temperature environment,result in the difficulties and challenges of the low-temperature tribotester.In particular,novel technologies and tribotesters have been developed for tribotests and tribological studies of solid lubricants,spherical plain bearings,and roller bearings,overcoming limitations regarding cooling in vacuum and resolution of friction measurement,among others,and concentrating on in-situ observation of friction interface.These not only promote a deep understanding of friction and wear mechanism at low temperatures,but also provide insights into the performance of moving parts or components in cryogenic applications.展开更多
Aluminum alloy sheets are used more and more to manufacture auto panels. Because the friction behavior is very complicated, it is necessary to study the friction during the aluminum sheet warm forming process. The aut...Aluminum alloy sheets are used more and more to manufacture auto panels. Because the friction behavior is very complicated, it is necessary to study the friction during the aluminum sheet warm forming process. The author has designed a new probe sensor based on an online tribotest method which directly measures friction coefficient in the forming process. Experiments of cup drawing have been conducted and the friction coefficients under different forming conditions have been measured. The results indicate that the forming parameters, such as forming temperature, blankholding force and lubrication status have great effect upon the friction coefficient.展开更多
For tribological investigations of automotive brakes, both full and reduced scale brake dynamometers are used. Full scale brake dynamometers test the entire brake system, including caliper, brake pad, brake disk, whee...For tribological investigations of automotive brakes, both full and reduced scale brake dynamometers are used. Full scale brake dynamometers test the entire brake system, including caliper, brake pad, brake disk, wheel suspension, etc. The AUT （automated universal tribotester） is a reduced scale brake dynamometer with a pin on disk test configuration. A brake pad specimen is used as the pin and a brake disk is used as the counter body. Compared to full scale brake dynamometers, the AUT encounters fewer influences from the test systems themselves. The AUT was developed at the Institute of Dynamics and Vibrations in Braunschweig. It can be used for high frequency analyses of the coefficient of friction, and investigations of the boundary layer between brake pad and disk, along with the associated NVH behaviors. A digital camera and two laser triangulation sensors are used for optical investigations of the brake pad and brake disk [1, 2]. The focus of this paper is the development of a new control feature of the AUT. The AUT employs a compactRIO from National Instruments as its measurement and control device. The velocity and position control loops are implemented in the compactRIO＇s FPGA along with high frequency synchronous measurement data acquisition. Its real-time controller coordinates the measurement and the storage of measured data. The test device has three degrees of freedom： normal load, sliding speed, and temperature, all of which can be defined by the user for each brake application. New control strategies based on the friction force as a feedback parameter allow for the implementation of new features. In this paper, the realization of measurements with constant friction power throughout the friction procedure will be shown. This new degree of freedom in the friction measurements enables investigations to be carried out in which it is necessary to bring a specific energy in the friction process. In this paper, a p-controller on the real-time system calculates the required set point for the position control loop. The new feature is verified through a benchmark test [6]. Based on the control loop with the friction force as the feedback parameter, it is also possible to emulate in-stop brakes with virtual inertia. In this way, many other types of full scale brake dynamometers can be simulated. The long-term aim is the identification of the influence of test devices on the test results.展开更多
为了能够比较真实地模拟微机电器件侧面摩擦副之间的摩擦磨损状况,进而对M EM S器件的摩擦学规律进行研究,设计了一种基于单晶硅材料的片上微摩擦测试机构。利用微机械体硅工艺及键合技术,把系统中的测试机构、加载机构以及力传感器集...为了能够比较真实地模拟微机电器件侧面摩擦副之间的摩擦磨损状况,进而对M EM S器件的摩擦学规律进行研究,设计了一种基于单晶硅材料的片上微摩擦测试机构。利用微机械体硅工艺及键合技术,把系统中的测试机构、加载机构以及力传感器集成在一个单一的芯片上。对结构的临界驱动电压、静态摩擦力及正压力进行了理论推导。最后,在显微镜下对该机构的静态摩擦因数进行了测试。测试结果表明:随着施加在摩擦副上的正压力的增加,摩擦因数相应减小。展开更多
基金Project supported by the Research University Grant from Universiti Teknologi Malaysia (No. 00J02)the Fundamental Research Grant Scheme from the Ministry of Higher Education (MOHE) (No. 78604)the E-Science Grant from the Ministry of Science,Technology and Innovation of Malaysia (No. 79396)
文摘The effects of the mechanical factors with applied loads on the tribological performance of refined,bleached and deodorised(RBD) palm stearin(PS) were studied using a four-ball tribotester.All the RBD PS results were simultaneously compared with the additive-free paraffinic mineral oil(PMO).The experiments were carried out using different loads with a constant speed in order to gain a better understanding of the mechanical processes that occurred during the experiment.For each experiment,the temperature was increased to 75 °C and was run for 1 h.In a mechanical system,lubricant plays an important role in reducing wear and friction.PS exists as a semi-solid at room temperature after the fractionation process from oil palm.Due to the increasing rate of pollution to the environment,vegetable oil was chosen as the test lubricant with regard to its biodegradability.Other advantages of vegetable oil are that it is more easily harvestable and non-toxic compared to petroleum-based oil,which made it a suitable candidate.From the experiment,RBD PS is found to have a better friction constraint reduction compared with additive-free PMO.
基金supported by National Natural Science Foundation of China(Grant Nos.51935006,52225502)。
文摘Tribology at cryogenic temperatures has attracted much attention since the 1950s with the acceleration of its applications in high-tech equipment such as cryogenic wind tunnels,liquid fuel rockets,space infrared telescopes,superconducting devices,and planetary exploration,which require solid lubrication for moving parts at low temperatures down to 4 K in cryogenic liquid,gaseous,or vacuum environments.Herein,the research progress regarding cryo-tribology is reviewed.The tribological properties and mechanisms of solid lubricants listed as carbon materials,molybdenum disulfide,polymers,and polymer-based composites with decreasing temperature are summarized.The friction coefficient increases with decreasing temperature induced by thermally activated processes.The mechanism of transfer film formation should be considered as a significant way to enhance the tribological properties of solid lubricants.In addition,applications of solid lubrication on moving parts under cryogenic conditions,such as spherical plain bearings and roller bearings,are introduced.The technology for tribological testing of materials and bearings at cryogenic temperatures is summarized,where the environmental control,motion and loading realization,as well as friction and wear measurement together in a low-temperature environment,result in the difficulties and challenges of the low-temperature tribotester.In particular,novel technologies and tribotesters have been developed for tribotests and tribological studies of solid lubricants,spherical plain bearings,and roller bearings,overcoming limitations regarding cooling in vacuum and resolution of friction measurement,among others,and concentrating on in-situ observation of friction interface.These not only promote a deep understanding of friction and wear mechanism at low temperatures,but also provide insights into the performance of moving parts or components in cryogenic applications.
基金Sponsored by General Motor Corporation of U.S.A.
文摘Aluminum alloy sheets are used more and more to manufacture auto panels. Because the friction behavior is very complicated, it is necessary to study the friction during the aluminum sheet warm forming process. The author has designed a new probe sensor based on an online tribotest method which directly measures friction coefficient in the forming process. Experiments of cup drawing have been conducted and the friction coefficients under different forming conditions have been measured. The results indicate that the forming parameters, such as forming temperature, blankholding force and lubrication status have great effect upon the friction coefficient.
文摘For tribological investigations of automotive brakes, both full and reduced scale brake dynamometers are used. Full scale brake dynamometers test the entire brake system, including caliper, brake pad, brake disk, wheel suspension, etc. The AUT （automated universal tribotester） is a reduced scale brake dynamometer with a pin on disk test configuration. A brake pad specimen is used as the pin and a brake disk is used as the counter body. Compared to full scale brake dynamometers, the AUT encounters fewer influences from the test systems themselves. The AUT was developed at the Institute of Dynamics and Vibrations in Braunschweig. It can be used for high frequency analyses of the coefficient of friction, and investigations of the boundary layer between brake pad and disk, along with the associated NVH behaviors. A digital camera and two laser triangulation sensors are used for optical investigations of the brake pad and brake disk [1, 2]. The focus of this paper is the development of a new control feature of the AUT. The AUT employs a compactRIO from National Instruments as its measurement and control device. The velocity and position control loops are implemented in the compactRIO＇s FPGA along with high frequency synchronous measurement data acquisition. Its real-time controller coordinates the measurement and the storage of measured data. The test device has three degrees of freedom： normal load, sliding speed, and temperature, all of which can be defined by the user for each brake application. New control strategies based on the friction force as a feedback parameter allow for the implementation of new features. In this paper, the realization of measurements with constant friction power throughout the friction procedure will be shown. This new degree of freedom in the friction measurements enables investigations to be carried out in which it is necessary to bring a specific energy in the friction process. In this paper, a p-controller on the real-time system calculates the required set point for the position control loop. The new feature is verified through a benchmark test [6]. Based on the control loop with the friction force as the feedback parameter, it is also possible to emulate in-stop brakes with virtual inertia. In this way, many other types of full scale brake dynamometers can be simulated. The long-term aim is the identification of the influence of test devices on the test results.
文摘为了能够比较真实地模拟微机电器件侧面摩擦副之间的摩擦磨损状况,进而对M EM S器件的摩擦学规律进行研究,设计了一种基于单晶硅材料的片上微摩擦测试机构。利用微机械体硅工艺及键合技术,把系统中的测试机构、加载机构以及力传感器集成在一个单一的芯片上。对结构的临界驱动电压、静态摩擦力及正压力进行了理论推导。最后,在显微镜下对该机构的静态摩擦因数进行了测试。测试结果表明:随着施加在摩擦副上的正压力的增加,摩擦因数相应减小。
