| Friction at high temperature is widely existed in aspects of life and production,so it is of great significance to study behavior mechanism of tribology.In order to research the phenomena and mechanism of friction and wear at high temperatures,to evaluate the influence of materials,working environment and other factors on friction and wear interface correctly,the high temperature friction and wear tester is an indispensable testing equipment.Based on the demand for interfacial friction and wear experiment of ultra-high strength steel at high temperatures,we design a simple and low-cost high temperature friction tester which can simulate relative rotational motion of pin-on-disk.The main work of the paper is:(1)According to the requirements of high temperature friction test and parameters that need to be measured,the overall scheme of the test machine was designed.And combing the relationships among the component,the working principle of the experimental machine is introduced.The friction test machine can simulate the following working conditions:spindle speed 0~200 r/min;load range 0~60 N;heating temperature at room temperature to 1000 ?;friction coefficient can be measured at0.01~2;die diameter 1~15 mm;heating sample thickness:0.5~10 mm.(2)The tester mechanical structural system has carried on detailed designs,including the rotational structure of sample disk,the structure of the mold pin lift loading,heating and ventilation system.We completed the 3D modelings and corresponding assembly of testing machine parts through solidworks.According to the3 D model of testing machine structure,its working process and principle are introduced.The control system of the test machine is also designed,including motion control and data acquisition.Siemens PLC is used to control the servo system for load loading and pin-on-plate rotation of the tester,it also can control heating temperature of specimen through the high frequency induction heater.A accurate three-dimensional force sensors is used to measure the friction force and loading force,meanwhile the thermometer measures real-time temperature of the heating sample.The force and temperature value are fed back to the PLC,which constitute a closed-loop PID control system.(3)The behavior characteristics of high strength steel frictional interface at high temperatures are researched by self-developed testing machine.From the macroscopic and microscopic understanding and analysis of high temperature tribologicalmechanism of the contact interface,the results are as follows:in a certain range,the friction coefficient decreases with the increase of load or speed,and the low speed is not conducive to the stability of the friction coefficient.With the increase of temperature,the friction coefficient increases first and then decreases gradually,but the coefficient increases significantly compared with the normal temperature;the friction interface damage form are mainly furrows and extrusion spalling at 500 ?.The main wear mechanisms are oxidation wear and abrasive wear,and the wear quantity is gradually increasing with the increase of load or rotational speed;different temperature has an enormous influence on the physical properties of the sample material,which result in changes of wear mechanism on interface.As the temperature increases,the wear mechanism gradually changes from abrasive wear to viscous wear,and the surface of the sample is badly worn;under the condition of graphite powder lubrication,a smaller friction coefficient can be obtained.In a short time,the microsurface of high-strength steel and die steel is relatively flat and smooth,and the wear mass loss reduced comparing the condition of dry friction. |
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