O’zbekistоn respublikasi оliy va o’rta maxsus ta`lim vazirligi

Rice. 1.

Determination of the friction force of materials.
Between the 2nd test specimen (see Fig. 1) the 1st ball of hard material is placed. The geometric shape of the ball is clear, the surface roughness is minimal ( ). The sample is given N downloads. In order to make it convenient to turn the barrel along its axis, it was compressed to 3rd gear. A hole is made in the frame for attaching a dynamometer. A dynamometer hook is attached to the hole and the friction force F rotating the drum is measured.
REQUIRED TOOLS AND EQUIPMENT: Samples, sample stand, ball, dynamometer, weights.
OPERATING PROCEDURE:
1. Install the sample on the stand.
2. Place the weight on the sample, placing a special clamp between the samples.
3. Using a dynamometer (or weights), measure the force that can turn the drum.
4. Substitute the obtained value into the formula and determine the coefficient of friction.
Conduct an experiment with and without lubrication, compare the results and write a conclusion.
Lab №2

COEFFICIENT OF FRICTION OF NON-METALLIC MATERIALS

METHOD OF DETERMINATION

PURPOSE OF THE WORK: To study the method for determining the coefficient of friction of non-metallic materials.

THEORETICAL DATA: The friction process is the result of two interrelated processes: the deformation of microheterogeneities in the contact and the molecular interaction of materials on a clean contact surface.

The force of molecular motion on the surface of precise contact counteracts the mutual motion of the surfaces and creates a friction force.
According to the molecular mechanical theory, the coefficient of additional friction is determined by the following formula:

Here, F is the force of additional friction;

N - normal load.
Determination of the friction force of materials.

Between the 2nd test specimen (see Fig. 1) the 1st rod of solid material is installed. The geometric shape of the sokka is clear, the surface roughness is minimal. The sample is given N downloads. In order for the barrel to turn easily, it is compressed to 3rd gear. A hole is made in the frame for attaching a dynamometer. A dynamometer hook is attached to the hole and the friction force F rotating the drum is measured.

REQUIRED TOOLS AND EQUIPMENT: Specimens, sample stand, sledgehammer, dynamometer, weights.

OPERATING PROCEDURE:
1. Install the sample on the stand.
2. Place the weight on the sample, placing a special clamp between the samples.
3. Using a dynamometer (or weights), measure the force that can turn the drum.
4. Substitute the obtained value into the formula and determine the coefficient of friction.
Conduct an experiment with and without lubrication, compare the results and write a conclusion.
Lab №3
DETERMINATION OF THE COEFFICIENT OF FRICTION OF A FIBER BETWEEN A PAIR
PURPOSE OF THE WORK: To study the method for determining the coefficient of friction of materials with fiber in textile machines.

THEORETICAL DATA: The friction process is the result of two interrelated processes: the deformation of microheterogeneities in the contact and the molecular interaction of materials on a clean contact surface.

The force of molecular interaction on the surface of a point contact resists the movement of the surfaces and creates a friction force.
According to the molecular mechanical theory, the coefficient of additional friction is determined by the following formula:

Here, F is the force of additional friction;

N - normal load.

DETERMINATION OF THE FRICTION FORCE OF MATERIALS.

1. Choose a working pair of friction (Fig. 2).
2. Place the fiber under test between them.
3. Determine the force that moves the fiber under study by placing N weights and hanging the dynamometer or weights.
3. Substitute the obtained values into the formula and determine the coefficient of friction.
Repeat the experiment to determine and compare the coefficient of friction.