RU2340886C1 - Device for determining coefficient of friction - Google Patents

Abstract

FIELD: physics; measurements.

SUBSTANCE: present invention pertains to the agricultural machinery industry, and particularly to methods of investigating coefficient of friction of materials. The device for determining coefficient of friction contains a sample, placed on the analysed surface, joined to a load by a thread, as well as two sensors for switching on and off an electronic stopwatch, placed at the beginning and at the end of the meter long section, respectively. The sample is fixed on a frame, rigidly joined to a horizontal draw-bar, the second end of which is hinged to the frame. The mass of the draw-bar is considerably less than the mass of the sample with the frame. The analysed surface is cylindrical, and is rigidly joined to a pulley of equal radius. The thread with the load is wound around the pulley.

EFFECT: increased accuracy of determining coefficient of friction with reduction of dimensions of the stand at the same time.

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Description

The invention relates to the field of agricultural engineering, and in particular to methods for studying the coefficients of friction of materials.

A device for determining the coefficient of friction, containing a sample located on the studied horizontal surface and using a thread thrown over the block associated with the load [1].

The disadvantage of this device is the low accuracy of the results obtained on it.

Closest to the proposed device for determining the coefficient of friction is a device containing a sample located on the studied horizontal surface and using a thread thrown over a block connected with the load, as well as an on and off sensor for stopping the electric stopwatch, installed respectively at the beginning and end of the meter section [2].

The disadvantage of this device is the low accuracy of the results, since they do not take into account the inertial and frictional characteristics of the unit. In addition, this device is cumbersome, since the length of the investigated surface must be no less than the path of the load.

The objective of the present invention is to improve the accuracy of determining the coefficient of friction while reducing the dimensions of the device.

The problem is achieved in that in the device for determining the coefficient of friction, containing a sample located on the test surface, a thread connected to the load, as well as an on-off sensor and an electric stopwatch off sensor installed respectively at the beginning and end of the meter section, the sample is fixed in the carriage, rigidly connected to a horizontal leash, the second end of which is pivotally connected to the frame, and the mass of the leash is much less than the mass of the sample with the carriage, and the surface under investigation is made in the form e cylinder rigidly connected to a pulley of equal radius, while the thread with the load is wound on a pulley.

Figure 1 shows a diagram of a device for implementing the method for determining the coefficient of friction, figure 2 - view a in figure 1.

The device for determining the coefficient of friction (Fig. 1) includes a sample 1, which is secured with a fastener 2 in the carriage 3. The carriage 3 is rigidly connected to the lead 4, the mass of which is much less than the mass of the sample 1 with the carriage 3. The second end of the lead 4 is pivotally connected to stand frame (not shown). Sample 1 lies on the test surface (figure 2), which is made in the form of a cylinder 5. The cylinder 5 is rigidly connected to a pulley 6, on which the thread 7 is wound with a load 8. The device also includes an electric stopwatch 9 to which, through wiring, are connected switch-on sensor 10 and switch-off sensor 11, installed respectively at the beginning and at the end of the meter section S.

The proposed device operates as follows.

Under the weight of the load 8, the pulley 6, and with it the cylinder 5 are rotationally driven. In this case, between the sample 1 and the cylinder 5 there is a friction force, the magnitude of which will depend on the time the load falls. It is fixed on the meter section using sensors 10 and 11, as well as the electric stopwatch 9. Then, the friction coefficient is determined by the formula

where M is the mass of the cargo, kg;

m is the mass of the sample, kg;

I - the total moment of inertia of the cylinder of friction and pulley, kg · m ² ;

S - movement of cargo, m (S = 1 m);

t is the time of movement of the cargo along the path S, s;

g is the acceleration of gravity, m / s ² ,

R is the radius of the friction cylinder, equal to the radius of the pulley, m

Moreover, the fixation of the sample 1 using the carriage 3 and pivotally connected to the frame of the horizontal leash 4 allows you to ensure free pressure of the sample 1 on the cylinder 5, under the action of gravity. Moreover, since the mass of the leash 4 is significantly less than the total mass of sample 1 and carriage 3, it can be neglected in the calculations.

Information sources

1. Sablikov M.V. Agreecultural machines. Agreecultural equipment. Part II / M.V.Sablikov. - M .: Kolos, 1968, p. 7.

2. RU No. 2300755, CL G01N 19/02, 2007 - a prototype.

Claims (1)

A device for determining the coefficient of friction, containing a sample located on the test surface, a thread connected to the load, and an on-off sensor and an off timer for the electric stopwatch, installed respectively at the beginning and end of the meter section, characterized in that the sample is mounted in a carriage rigidly connected to a horizontal a leash, the second end of which is pivotally connected to the frame, and the mass of the leash is much less than the mass of the sample with the carriage, and the test surface is made in the form of a cylinder, rigidly with union of a pulley of equal radius, the thread is wound on with the load sheave.

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