Development Of High-precision Static Friction Coefficient Tester And Study On Materials Tribological Properties

Static friction is one of the most parts of tribology.The study on static friction is highly significant to engineering applications and theoretical research.The pre-sliding of static friction is crucial when the accuracy is nanometer degree,extremely in the fields of positioning control,measurement,assembly and manufacturing.Furthermore,that the static friction of viscous-elastic material and the effect of dwell time on static friction is deserving of study.Good tools are prerequisite to the successful execution of a job.In order to do a comprehensive study on static friction,a stably,reliably and high precision static friction tester is necessary.In this paper,a high precision static friction tester was developed.Moreover,the detection of the critical moment at which initial relative motion takes place was of prime interest in this study.As well,the static friction coefficients of several materials were assessed by using the setup.The results of this study could be summarized as follow.(1)This static friction coefficient tester was high-precision and stable.The development provides a necessary setup to the static friction study.Several crutical technical problems were settled.?)Power part included stepping motor and LM linear module.The stepping motor could control rotate speed and the number of revolution precisely.The speed of minimum rotate is 1 rpm,which means,the linear velocity is 0.033mm/s.LM linear module could guarantee the straightness and smooth movement with smaller friction force.Both of them improved the precision of the tester.?)Static friction measurement part included linear guide rail and s-type pull-pressure sensor.The linear guide rail further ensured the straightness and smooth movement under the condition of smaller friction force.S-type pull-pressure sensor could measure the static friction precisely.The frequency of data collection is 100Hz.Four socket screw bolts were installed in the sleeve.Thus,the contact of sleeve and holder convert from surface contact to point contact.By this way,not only the precision of static friction measurement,but also the precision of gravitational loading system was improved significantly.?)The rigid connection of power part and static friction measurement part ensured the force transmit effectively and punctually.On the other hand,this type of connection could measure the maximum static friction accurately.The main parameters of the tester are as follow:a)normal load:1.8?100N;b)loading error<1%;c)spindle speed:1?100r/min;d)speed error<5%;e)linear velocity:0.033mm/s-3.300mm/s;f)precision of static friction measurement:0.05N;g)static friction measurement error ?0.5%;h)working temperature:0??400?.(2)From the detection of the critical moment at which initial relative motion takes place,we may draw the conclusion as follow:Before the maximum static friction coefficient,the samples are not absolutely still.Actually,micro-motion between two samples has happened.Studying further,it is found that the movement of the samples is not linear sliding immediately after the maximum static friction coefficient appears.On the contrary,the movement is nonlinear sliding in a long time.(3)The reliability study on the tester shows that the reliability of the setup is high.(4)After carrying on the static friction coefficient measurement of several type materials,it could be discovered that the static friction coefficient is related to the speed of samples relative movement and normal load.