CN111812025A - A kind of dynamic friction coefficient measuring device and measuring method - Google Patents

Abstract

The invention relates to a dynamic friction coefficient measuring device and a measuring method, wherein the measuring device comprises: the test block, the slide, work platform, U type spout, jacking device, transmission, fixing device, buffer, universal air level, data acquisition and analytic system. Work platform depends on the rigidity terrace and passes through universal air level leveling and be used for fixed jacking device, the jacking device passes through the transmission drive, connects U type spout one side and promotes it and remove along vertical direction, it is fixed through fixing device to arrange the slide of contact B material in the U type spout, acceleration sensor depends on the test block of contact A material. And measuring physical parameters of the test block in the initial sliding and gliding processes, calculating the static friction coefficient and establishing a functional relation between the dynamic friction coefficient of the two contact bodies and the relative sliding speed time course. The method can accurately and conveniently measure the static and dynamic friction coefficients based on test measurement, data acquisition and processing and formula regression.

Description

A kind of dynamic friction coefficient measuring device and measuring method

technical field

The invention belongs to the technical field of friction coefficient measurement, and in particular relates to a dynamic friction coefficient measurement device and a measurement method.

Background technique

The coefficient of friction refers to the ratio between the frictional resistance and the normal pressure between the contact surfaces of two objects, which is related to the roughness of the surface and has nothing to do with the size of the contact area. In engineering practice, static and dynamic friction coefficients are usually used to characterize the relative mechanical relationship between two contact surfaces. Studies have shown that the coefficient of kinetic friction is much more complex than the coefficient of static friction, which is usually not a definite value, but changes non-monotically with the relative sliding speed between the two contact bodies. This property significantly affects the mechanical behavior between the contacting bodies, and ignoring this property can lead to serious errors in test results. Most of the existing test equipment and methods do not consider the influence of sliding speed on the coefficient of kinetic friction, and most of them are carried out in a state of approximately uniform speed, or end quickly after the occurrence of relative sliding, and fail to fully consider the effect of sliding speed and its amplitude on the coefficient of kinetic friction. Mechanism and degree of influence. In scientific research experiments and precision engineering that need to accurately consider the change of friction coefficient, the existing testing equipment and methods are not comprehensive and perfect, and cannot meet the requirements of the precise parameters of this parameter. Considering the influence of speed on the friction coefficient, the invention proposes a dynamic friction coefficient measuring device and a measuring method.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention proposes a dynamic friction coefficient measuring device and a measuring method considering the influence of speed on the dynamic friction coefficient.

A dynamic friction coefficient measuring device, the measuring device includes a test block, a slideway, a working platform, a U-shaped chute, a jacking device, a transmission device, a fixing device, a buffer device, a universal level bubble and a data acquisition and analysis system, The working platform is attached to the rigid floor and is leveled by a universal level bubble and used to fix the jacking device. The slideway is fixed in the U-shaped chute by the fixing device. One side of the chute is connected and driven by a transmission device to lift the U-shaped chute to move in the vertical direction. The data acquisition and analysis system includes an acceleration sensor, an inclination sensor, a dynamic acquisition instrument and a computer terminal, and the acceleration sensor is fixed on the The upper part of the test block, the inclination sensor is fixed on the outer side of the middle part of the U-shaped chute, the acceleration sensor and the inclination sensor are respectively connected with the dynamic acquisition system through signal lines, the dynamic acquisition system is connected with the computer terminal, and the computer terminal is connected with the top. The lifting device is connected to control the lifting and lowering of the lifting device. The computer terminal controls the lifting device to stop when the acceleration sensor data is greater than zero. The buffer device is installed on the inner bottom of the U-shaped chute.

Further, the test block has no specified shape, the surface that the test block contacts with the slideway is the receiving side, and the material of the test block is any required material or has the same material with different surface features; the slideway is detachable. , the material of the slideway is any required material or has the same material with different surface features, and the contact surface between the slideway and the slider is flat.

Further, the rack of the jacking device is fixed on the working platform by bolts, and the jacking device transmits power by the transmission device through the wheel belt.

Further, the transmission device is driven by a motor, and drives the gear to rotate through the wheel belt, thereby driving the jacking device to lift in the vertical direction.

Further, the fixing device includes two, which are respectively arranged at the upper and lower ends of the U-shaped chute, and the fixing device can be adjusted by a hand wheel to adapt to slideways of different thicknesses and materials.

Further, the width of the U-shaped chute can ensure that the test block does not come into contact with both sides of the U-shaped chute at the initial position and during the sliding process.

A kind of dynamic friction coefficient determination method, described method comprises the following steps:

Step 1. Prepare the test block and slideway of the material required for the test;

Step 2. Build a basic test system consisting of a working platform, a jacking device, a transmission device and a U-shaped chute;

Step 3. Arrange the chute in the U-shaped chute and fix it with the fixing device, and arrange the buffer device at the bottom end of the U-shaped chute;

Step 4. Fix the acceleration sensor on the upper part of the test block, measure the total weight of the acceleration sensor and the test block with a balance, place the test block on the top of the U-shaped chute, and ensure that the lower surface of the test block is in close contact with the upper surface of the contact slideway. Arrange the inclination sensor on the outside of the middle of the U-shaped chute;

Step 5. Connect the acceleration sensor and the inclination sensor to the computer terminal through the dynamic acquisition system, and connect the jacking device to the computer terminal;

Step 6. Control the transmission through the computer terminal and pull the jacking device to ascend slowly, collect the acceleration time history a(t) collected by the acceleration sensor and the inclination data collected by the inclination sensor in real time, and the computer terminal controls the transmission at the moment when the test block starts to slide Stop the action. At this time, the inclination data collected by the inclination sensor is θ. The computer terminal performs fitting calculation according to the collected real-time data, and establishes the functional relationship between the kinetic friction coefficient of the test block and the relative sliding speed time history, and obtains the dynamic friction through the sliding speed time history. coefficient.

Further, the calculation method of the function of the kinetic friction coefficient and the relative sliding velocity time history in the step 6 is:

Step 6.1, the computer terminal will automatically judge the relative sliding start time t _i and the corresponding inclination angle θ according to the acceleration time course a(t), wherein the sliding start time t _i satisfies the following conditions,

a(t _i-1 )=0and a(t _i )≠0 (1)

The corresponding inclination angle θ at time t _i is recorded as:

θ=θ(t _i ) (2)

At time t _i , the inclination angle rotated by the slide lift is θ. When the acceleration begins to appear, it means that the test block starts to slide, and the slide lift stops. During this period, the slide angle also reaches θ from 0°. ;

Step 6.2. According to the principle of mechanical balance, the computer terminal calculates the static friction coefficient μ _s between the test block and the slideway when the test block starts to slide, namely:

μ _s = tan θ (3)

Step 6.3. The computer terminal obtains the correlation formula between the coefficient of kinetic friction and the coefficient of static friction:

According to Newton's second law, starting from the moment when the test block starts to slide, the kinetic friction coefficient μ _d between the test block and the slideway is calculated based on the acceleration time history data a(t) of the test block sliding process and the corresponding inclination angle θ at the test block sliding trigger moment ( t), that is:

There is the following correlation between the coefficient of dynamic friction μ _d and the coefficient of static friction μ _s :

In the formula, g is the acceleration of gravity, in m/s ² ; θ is the angle between the U-shaped chute and the horizontal table when the test block starts to slide; μ _d (t) is the coefficient of kinetic friction; μ _s (t) is Static friction coefficient when the test block starts to slide down; a(t) is the acceleration time history, in m/s ² ;

Step 6.4. Obtain the relationship between the kinetic friction coefficient, the static friction coefficient and the relative sliding velocity time history:

Numerical integration calculates the acceleration time history to obtain the relative sliding velocity time history V(t) of the two contact bodies of the test block and the slideway, namely:

In the time coordinate system, the relationship between the ratio of the kinetic friction coefficient and the static friction coefficient μ _d / μ _s and the relative sliding velocity time history V(t) of the two contact bodies of the test block and the slideway is established:

μ _d (t) = μ _s ·f(V(t)) (7)

Step 6.5, repeat steps 6.1-6.4, take the average value of multiple measurement results for parameter regression, and obtain the relationship between the kinetic friction coefficient, static friction coefficient and relative sliding velocity time history between the test block and the two contact bodies of the slideway, namely ,

in,

According to the feature of the function graph, the parameter regression is carried out on the measurement results by the numerical method, and the calculation formula of the sliding friction coefficient is obtained:

In the formula, a, b, c and d are parameters obtained by fitting, and the test data obtained by different materials or different surface characteristics of the same material are different.

Beneficial effects: The relationship between the relative sliding velocity time history and the coefficient of kinetic friction is established, and the values of the coefficients of static and dynamic friction of different materials can be calculated more accurately through experimental testing, data collection, formula fitting, and given parameters, that is, Said that, according to the obtained formula, given an exact speed V and a known static friction coefficient μ _s , and then the parameters a, b, c, d obtained by fitting are brought into the solution, and a certain definite value can be easily and accurately obtained. The coefficient of kinetic friction μ _d , in which the fitting parameter is the data measured by the test, and is obtained by fitting the exponential function in the software.

Description of drawings

Fig. 1 is the flow chart of the dynamic friction coefficient measuring method of the present invention;

Fig. 2 is the structural representation of the kinetic friction coefficient measuring device of the present invention;

Fig. 3 is the exploded view of the kinetic friction coefficient measuring device of the present invention;

Fig. 4 is the force analysis diagram of the dynamic friction coefficient measurement of the present invention;

Fig. 5 is the data fitting diagram of the concrete test block and the smooth steel plate slideway that the kinetic friction coefficient of the present invention is measured;

6 is a data fitting diagram of a concrete test block and a rough steel plate slideway measured by the coefficient of kinetic friction of the present invention;

Fig. 7 is the data fitting diagram of the mortar test block and the smooth steel plate slideway of the dynamic friction coefficient measurement of the present invention;

FIG. 8 is a data fitting diagram of a mortar test block and a rough steel plate slideway for the determination of the kinetic friction coefficient of the present invention.

In the figure: 1, test block; 2, slideway; 3, working platform; 4, U-shaped chute; 5, jacking device; 6, transmission device; 7, fixing device; 8, buffer device; 9, acceleration sensor ; 10. Inclination sensor; 11. Universal level bubble; 12. Dynamic acquisition instrument; 13. Computer terminal; 14. Signal line.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

A kinetic friction coefficient measuring device, the measuring device includes a test block 1, a slideway 2, a working platform 3, a U-shaped chute 4, a jacking device 5, a transmission device 6, a fixing device 7, a buffer device 8 and a data acquisition and Analysis system, in order to ensure the level and stability of the working platform 3, the working platform 3 is attached to the rigid floor and leveled by the universal level bubble 11 and used to fix the jacking device 5, and the rack of the jacking device 5 is fixed on the working platform 3 by bolts superior. The jacking device 5 is driven by the transmission device 6, and the transmission device 6 is driven by the motor, and drives the gear to rotate through the belt, so that the jacking device 5 is lifted in the vertical direction. The jacking device 5 is connected to one side of the U-shaped chute 4 and lifts it to move in the vertical direction. The sliding track 2 is arranged in the U-shaped chute 4 and is fixed by the fixing device 7. The data acquisition and analysis system includes an acceleration sensor 9, Inclination sensor 10, dynamic acquisition instrument 12 and computer terminal 13, the lifting device 5 is automatically controlled by the computer terminal 13 to lift and lower, the fixing device 7 is installed on the U-shaped chute 4, and one is placed at the upper and lower ends for fixing the chute 2 , the slideway is arranged in the U-shaped chute 4, and the buffer device 8 is installed at the bottom of the U-shaped chute 4 to prevent the test block 1 from hitting the bottom to cause damage and make it decelerate and stop. The acceleration sensor 9 is fixed on the test block 1. The inclination sensor 10 is fixed on the side table of the groove of the U-shaped chute 4, and is associated with the computer terminal 13 through a soft signal line 14. The inclination sensor 10 is arranged outside the middle of the U-shaped chute 4 . The acceleration sensor 9 and the inclination sensor 10 are connected to the dynamic acquisition system 12 via the signal line 14 , and are connected to the computer terminal 13 via the dynamic acquisition system 12 . The connection between the control system of the jacking device 5 and the computer terminal 13 is established. The computer terminal controls the jacking device to stop moving when the acceleration sensor data is greater than zero.

The test block has no specified shape, the contact surface of the test block and the slideway is the receiving side, and the material of the test block is any required material or has the same material with different surface features; the slideway is detachable, and the slideway is detachable. The material is any required material or has the same material with different surface features, and the contact surface between the slideway and the slider is flat.

The rack of the jacking device is fixed on the working platform by bolts, and the jacking device transmits power by the transmission device through the wheel belt.

The transmission device is driven by the motor, and drives the gear to rotate through the wheel belt, thereby driving the jacking device to lift in the vertical direction.

The fixing device includes two, which are respectively arranged at the upper and lower ends of the U-shaped chute, and the fixing device can be adjusted by a hand wheel to adapt to the slideways of different thicknesses and materials.

The width of the U-shaped chute 4 is wide to ensure that the test block 1 does not contact both sides of the U-shaped chute 4 at the initial position and during the sliding process.

The following takes the concrete test block 1 and the smooth steel plate slideway 2 as examples to test the coefficient of kinetic friction:

Step 1, prepare the contact body is concrete material test block 1 and the contact body is the slideway 2 made of smooth steel plate.

Step 2, as shown in Figure 2, build a basic test system consisting of a working platform 3, a U-shaped chute 4, a jacking device 5, a transmission device 6 and other components.

In step 3, a smooth steel plate slideway 2 is arranged in the U-shaped chute 4 and fixed by a fixing device; a buffer device 8 is arranged at the bottom end of the U-shaped chute 4 .

Step 4, as shown in Figure 3, fix the acceleration sensor 9 on the upper part of the concrete test block 1, measure the total weight of the acceleration sensor and the test block with a balance, and then place it on the top of the U-shaped chute 4 to ensure that the concrete test block is 1 The surface is in close contact with the upper surface of the smooth steel plate slideway 2 ; the tilt sensor 10 is arranged outside the middle of the U-shaped slideway 4 .

Step 5, connect the acceleration sensor 9 and the inclination sensor 10 to the computer terminal 13 via the dynamic acquisition system 12. The connection between the control system of the jacking device 5 and the computer terminal 13 is established.

Step 6: Control the transmission through the computer terminal and pull the jacking device to ascend slowly, collect the acceleration time history a(t) collected by the acceleration sensor and the inclination data collected by the inclination sensor in real time, and the computer terminal controls the transmission at the moment when the test block starts to slide Stop the action. At this time, the inclination data collected by the inclination sensor is θ. The computer terminal performs fitting calculation according to the collected real-time data, and establishes the functional relationship between the kinetic friction coefficient of the test block and the relative sliding speed time history, and obtains the dynamic friction through the sliding speed time history. coefficient.

The calculation method of the function of the kinetic friction coefficient and the relative sliding velocity time history in the step 6 is:

Step 6.1. Control the transmission device 6 and pull the jacking device 5 through the computer terminal 13, during which the acceleration data a(t) and the inclination data are collected in real time, and the computer terminal 13 will automatically judge the relative sliding start according to the acceleration time course a(t). Time t _i and the corresponding inclination angle θ. Among them, time t _i satisfies the following conditions,

a(t _i-1 )=0and a(t _i )≠0 (1)

In the formula, it is expressed that the acceleration value appears at the time t _i , and the acceleration value is 0 at the time before this time, that is, the time t _i-1 . The corresponding inclination angle θ at time t _i is recorded as:

θ=θ(t _i ) (2)

In the formula, at time t _i , the inclination angle at which the chute lift occurs is θ. When the acceleration begins to appear, it also means that the test block starts to slide, and the slide lift stops, during which the angle also reaches θ from 0°.

Step 6.2, the computer terminal calculates the static friction coefficient μ _s between the slider and the slide according to the angle θ corresponding to the slide when the relative sliding occurs, and according to the mechanical balance principle mg sinθ = μ _s mg cosθ shown in Figure 4 ,which is:

μ _s = tan θ (3)

It can be seen from the formula that a unique angle determines a unique static friction coefficient μ _s . Here below the average is taken for accurate multiple measurements.

Step 6.3, the computer terminal calculates and obtains the correlation formula between the coefficient of kinetic friction and the coefficient of static friction:

According to Newton's second law, starting from the moment when the test block starts to slide, the kinetic friction coefficient μ _d between the test block and the slideway is calculated based on the acceleration time history data a(t) of the test block sliding process and the corresponding inclination angle θ at the test block sliding trigger moment ( t), that is:

The determined angle θ determines the parameters of the formula, a(t) begins to appear data after time t _i , which is also a history curve about time, and μ _d (t) is also a history curve about time, in order to ensure the accuracy of the data , and also average the curves below.

There is the following correlation between the coefficient of dynamic friction μ _d and the coefficient of static friction μ _s :

In the formula, g is the acceleration of gravity, in m/s ² ; θ is the angle between the U-shaped chute and the horizontal table when the test block starts to slide; μ _d (t) is the coefficient of kinetic friction; μ _s (t) is Static friction coefficient when the test block starts to slide down; a(t) is the acceleration time history, in m/s ² ;

Step 6.4. Obtain the relationship between the kinetic friction coefficient, the static friction coefficient and the relative sliding velocity time history:

Considering the practical application, the relative velocity of the contact body is easier to calculate or measure, and it is also more convenient in practical application. Therefore, the velocity time history of the two contact bodies can be obtained by numerical integration of the acceleration time history, and the relative sliding velocity time history V(t) of the two contact bodies of the test block and the slideway can be obtained by numerical integration calculation of the acceleration time history, namely:

In the time coordinate system, the relationship between the ratio of the kinetic friction coefficient and the static friction coefficient μ _d / μ _s and the relative sliding velocity time history V(t) of the two contact bodies of the test block and the slideway is established:

μ _d (t) = μ _s ·f(V(t)) (7)

That is to say, there is a certain relationship between the dynamic and static friction coefficients and the speed.

Step 6.5. In order to make the obtained data more accurate, the method of removing the average value is used for multiple measurements. Repeat steps 6.1-6.4, and take the average value of the multiple measurement results to obtain the coefficient of kinetic friction between the two contact bodies of the test block and the slideway. The relationship between the coefficient of static friction and the relative sliding velocity, namely,

in,

的值，According to the measured data, a μ _d curve can be directly obtained each time, and then each μ _d curve is added and averaged to obtain a

the value of ,

The integrals of many a _i (t) curves are added and averaged to obtain an averaged speed curve,

According to the test results, plot the relationship between _μd / _μs and speed V, as shown in Figure 5, Figure 6, Figure 7, and Figure 8.

According to the feature of the function graph, the parameter regression is carried out on the measurement results by the numerical method, and the calculation formula of the sliding friction coefficient is obtained:

与V(t)之间的关系式。由实施例中，试验实测的数据，在软件中，运用指数型函数拟合，得到拟合式。In the formula, a, b, c and d are the parameters obtained by regression fitting, and the experimental data obtained from different materials or different surface characteristics of the same material are different. Equation (13) is used to express the final

relationship with V(t). From the data measured in the test in the embodiment, in the software, the exponential function is used to fit, and the fitting formula is obtained.

The parameters in the table below are the formula parameters obtained by fitting the measured data of FIG. 5 , FIG. 6 , FIG. 7 , and FIG. 8 in this embodiment.

For a given contact body, according to the regression formula, for the measured static friction coefficient μ _s and the relative sliding velocity time history V(t), the parameters a, b, c, and d are given in the table and brought into the solution, which can be easily and accurately obtained. The time history μ _d (t) of the coefficient of kinetic friction can be obtained.

Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention should also belong to the present invention. The scope of protection of the invention.

Claims (8)

1. A dynamic friction coefficient measuring device comprises a test block, a slide way, a working platform, a U-shaped chute, a jacking device, a transmission device, a fixing device, a buffering device, a universal air level and a data acquisition and analysis system, and is characterized in that the working platform is attached to a rigid terrace and is leveled by the universal air level and used for fixing the jacking device, the slide way is fixed in the U-shaped chute by the fixing device, the jacking device is connected with one side of the U-shaped chute and is driven by the transmission device to lift the U-shaped chute to move along the vertical direction, the data acquisition and analysis system comprises an acceleration sensor, an inclination angle sensor, a dynamic acquisition instrument and a computer terminal, the acceleration sensor is fixed on the upper part of the test block, the inclination angle sensor is fixed on the outer side of the middle part of the U-shaped chute, and the acceleration sensor and the inclination angle sensor are respectively connected with the dynamic acquisition, the dynamic acquisition system is connected with the computer terminal, the computer terminal is connected with the jacking device to control the jacking device to lift, the computer terminal receives the acceleration sensor data and controls the jacking device to stop when the data start to be larger than zero, and the buffer device is installed at the bottom of the inner side of the U-shaped sliding groove.

2. The dynamic friction coefficient measuring apparatus according to claim 1, wherein: the test block has no designated shape, the surface of the test block, which is in contact with the slideway, is a receiving side surface, and the test block is made of any required material or has the same material with different surface characteristics; the slide can be dismantled, and the material of slide is any required material or has the different surface characteristics of same material, the slide is the plane with the contact surface of slider.

3. The dynamic friction coefficient measuring apparatus according to claim 1, wherein: the rack of the jacking device is fixed on the working platform through a bolt, and the jacking device is driven by a transmission device through a wheel belt.

4. The dynamic friction coefficient measuring apparatus according to claim 1, wherein: the transmission device is driven by a motor, and the gear is driven to rotate through a belt wheel, so that the jacking device is driven to lift along the vertical direction.

5. The dynamic friction coefficient measuring apparatus according to claim 1, wherein: the fixing devices comprise two fixing devices which are respectively arranged at the upper end and the lower end of the U-shaped sliding groove, and the fixing devices can be adjusted through hand wheels to adapt to sliding ways with different thicknesses and materials.

6. The dynamic friction coefficient measuring apparatus according to claim 1, wherein: the width of the U-shaped sliding groove can ensure that the test block is not contacted with both sides of the U-shaped sliding groove at the initial position and in the gliding process.

7. The measuring method using a dynamic friction coefficient measuring apparatus according to any one of claims 1 to 6, characterized by comprising the steps of:

step 1, preparing a test block and a slideway which are made of materials required by testing;

step 2, building a basic test system consisting of a working platform, a jacking device, a transmission device and a U-shaped sliding chute;

step 3, arranging a slide way in the U-shaped chute, fixing the slide way through a fixing device, and arranging a buffer device at the bottom end of the U-shaped chute;

step 4, fixing the acceleration sensor on the upper part of the test block, measuring the total weight of the acceleration sensor and the test block by using a balance, placing the test block on the top of the U-shaped chute, ensuring that the lower surface of the test block is closely contacted with the upper surface of the contact slideway during the test block is placed on the top of the U-shaped chute, and arranging the inclination angle sensor on the outer side of the middle part of the U-shaped chute;

step 5, connecting the acceleration sensor and the tilt sensor with a computer terminal through a dynamic acquisition system, and connecting the jacking device with the computer terminal;

and 6, controlling the transmission device and drawing the jacking device to slowly rise through the computer terminal, acquiring the acceleration time course a (t) acquired by the acceleration sensor and the inclination angle data acquired by the inclination angle sensor in real time, controlling the transmission device to stop acting at the moment when the test block starts to slide, wherein the inclination angle data acquired by the inclination angle sensor is theta, performing fitting calculation through the computer terminal according to the acquired real-time data, establishing a functional relation between the dynamic friction coefficient of the test block and the relative sliding speed time course, and acquiring the dynamic friction coefficient through the sliding speed time course.

8. The method of claim 7, wherein the function of the kinetic friction coefficient and the relative sliding speed time course in step 6 is calculated by:

step 6.1, the computer terminal automatically judges the relative sliding starting time t according to the acceleration time course a (t)_iAnd a corresponding inclination angle theta, wherein the slip start time t_iThe following conditions are satisfied,

a(t_i-1)＝0 and a(t_i)≠0 (1)

t_ithe time-corresponding inclination angle θ is recorded as:

θ＝θ(t_i) (2)

at t_iAt the moment, the inclination angle of the lifting rotation of the slide way is theta, when the acceleration begins to appear, the test block begins to slide, the lifting of the slide way is stopped, and the angle of the slide way also reaches theta from 0 degrees in the period;

6.2, the computer terminal calculates the sliding time of the test block and the static friction coefficient mu between the test block and the slideway according to the mechanical balance principle_sNamely:

μ_s＝tanθ (3)

6.3, the computer terminal obtains the correlation between the dynamic friction coefficient and the static friction coefficient:

according to Newton's second law, starting from the moment when the test block starts to slide down, calculating the dynamic friction coefficient mu between the test block and the slideway based on the acceleration time course data a (t) in the process of sliding down the test block and the corresponding inclination angle theta of the slide triggering moment of the test block_d(t), namely:

coefficient of dynamic friction mu_dCoefficient of static friction mu_sThere is a relationship betweenLinking type:

wherein g is the acceleration of gravity in m/s²(ii) a Theta is an included angle between the U-shaped chute and the horizontal workbench at the moment when the test block starts to slide; mu.s_d(t) is the coefficient of dynamic friction; mu.s_s(t) is the static friction coefficient of the test block at the moment of starting to slide down; a (t) is acceleration time course in m/s²；

6.4, obtaining the correlation among the dynamic friction coefficient, the static friction coefficient and the relative sliding speed time interval:

and (3) calculating the acceleration time course through numerical integration to obtain a relative sliding speed time course V (t) of the two contact bodies of the test block and the slideway, namely:

establishing the ratio mu between the dynamic friction coefficient and the static friction coefficient in a time coordinate system_d/μ_sAnd the correlation between the relative sliding speed time interval V (t) of the two contact bodies of the test block and the slideway:

μ_d(t)＝μ_s·f(V(t)) (7)

step 6.5, repeating the steps 6.1-6.4, taking the average value of the multiple measurement results to carry out parameter regression, obtaining the relation between the dynamic friction coefficient, the static friction coefficient and the relative sliding speed time course between the test block and the two contact bodies of the slide way, namely,

wherein,

according to the characteristics of the function graph, parameter regression is carried out on the measurement result through a numerical method, and a sliding friction coefficient calculation formula is obtained:

where a, b, c and d are parameters obtained by fitting, different materials or different surface characteristics of the same material give different experimental data.

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