SU864068A1 - Method of determining sliding friction coefficient - Google Patents

Description

(54) METHOD FOR DETERMINING COEFFICIENT

t

The invention relates to the study of the tribological properties of materials.

A known method for determining the friction slip coefficient, which connects the samples along their flat test surfaces, forms the test joint, sets the test joint in a horizontal plane, and moves the upper sample along the surface of the lower sample U.

The disadvantage of this method is the low accuracy of the measurements, due to the use of elastic elements with strain gauges as well as the secondary amplifying and recording equipment as a force meter.

The purpose of the invention is to improve the measurement accuracy.

This goal is achieved by the fact that a circular pattern in a horizontal plane is reported to the lower sample, and the radii of the trajectories of the absolute motion of the upper and lower samples are measured and. The angular-frequency of movement of the lower sample, and the coefficient of slip are slip-; Friction rides

Neither and the speed of relative motion is determined by the formulas

., V-CU / RW.

where f is the coefficient of friction slip;

V is the speed of relative motion

r and R are the radii of the trajectories of the absolute motion of the upper and lower sample, respectively;

15

g is the acceleration of free fall; UJ is the angular frequency of movement of the lower sample.

The drawing shows a diagram of the device, explaining the implementation of the proposed method.

The device comprises a platform 1, horizontally suspended on flexible suspensions 2 and kinematically connected with an inertia vibrating feeder with a variable speed (not shown in the diagram). Platform 1 is designed to secure the bottom of the sample 3 on it, the working surface of which in the process of testing 30 is in contact with the working surface

the upper sample 4, which lies loosely on the lower sample 3. Above the upper sample 4, a transparent plate 5 with a scale for measuring the radii of the trajectories of the absolute circular motion of the upper 4 and lower 3 samples is fixed relative to the platform 1.

The method is implemented as follows.

On the platform 1, the lower sample 3 is fixed, on the working surface of which the upper sample 4 is installed, which lies loosely on it. Platform 1 is informed by an inertial vibration exciter, a circular translational motion in a horizontal plane with a frequency w. The radii of trajectories are recorded using a transparent plate 5 with a scale absolute circular motion of the upper 4 and lower 3 samples. Using the V UTjR ratios, the slip velocity V and the slip friction coefficient% are calculated. When this method is implemented, the ratio between the radii of the paths of the absolute circular motion of the lower sample 3 and the upper sample 4 is fulfilled. If, then the relative movement of the samples takes place and the value of f determined by formula (1) corresponds to sliding friction. If R g, samples 3 and 4 are in relative quiescence. This makes it possible to use the proposed method to determine the value of the coefficient of friction fp, corresponding to the value of the force of restfulness. To this end, the platform 1 is set to circular motion with such a frequency (l and amplitude R, so that the condition K is fulfilled. Then reduce the frequency and or amplitude R until the radius of the trajectory of the upper sample 4 is equal to the radius of the trajectory of the lower sample 3 The value of f calculated by the formula f corresponds to the value of fo when moving from sliding to rest.

Similarly, one can determine the value of fg in the transition from quiescence to,: slip. For this, platform 1 is assigned a circular translational motion with such a frequency and an amplitude R., so that the condition R g;

Then the frequency lU is increased until the condition R7 is fulfilled. Substitute this limit value in the formula and the value of f is determined.

c The proposed method is specifically used in studies of the frictional properties of materials at elevated and lowered temperatures, when the use of strain gauges combined with elastic elements is associated with the appearance of additional errors or leads to a considerable complication of experimental facilities.

Claims (1)

Invention Formula The method of determining the coefficient of friction slip, which consists in that the samples are mated along their flat test surfaces, forming the test joint, the test joint is placed in a horizontal plane, the upper sample is moved along the surface of the lower sample, characterized in that, in order to improve the measurement accuracy, a circular progressive motion in the horizontal plane, the radii of the trajectories of the absolute movement of the upper and lower samples and the angular frequency of the movement of the lower sample are measured, and the coefficient of sliding friction and speed of relative movement are determined by the formulas where f slip friction coefficient t V is the speed of relative motion; the radii of the trajectory of the absolute and the R motion of the upper and lower samples, respectively; acceleration of free fall; g W - the angular frequency of movement of the lower, the sample, o Sources of information,   taken into consideration at the examination 1. GM Bartenev. Lavrentyev V.V. Friction and wear of polymers. Chemistry 1972, p. 217 (prototype) Z "