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2- PRACTICAL CLASSES
STUDY OF THE FRICTION MACHINE SMTs-2.


Friction machine SMTs-2 is designed to study the processes of friction and wear in rolling friction with slip, in rolling friction without slip, and in sliding friction with or without lubrication. On fig. 3 is a schematic diagram of the SMC-2 machine when testing a disk-disk pair.
The lower test specimen 10 is driven by _the electric motor 12 through _a ^V _- belt _drive / with replaceable ­pulleys and gears Z ₀ - Zb _{_} _ ­the power of which sets the specified slip coefficient

where v1 and v2 are the linear velocities of the lower and upper samples, respectively ­.
The upper sample is pressed against the lower one by turning the balanced carriage 5 around the axis Z ₂ - Z _{3 by} spring mechanisms ­6. Load from readable on a scale 7 equipped with an ­adjusting device 8. The friction moment is measured by a ­contactless inductive moment meter 11 , and the rotational speed of ­the sample is measured by an electric meter 3 . machine, and an appropriate interchangeable tool is installed in its place . ­For tests in lubrication and in the presence of abrasive, the machine is equipped with removable chambers. The machine is protected from overloads by safety clutch 2.
The moment of friction can be recorded on a chart tape of an electronic potentiometer, placed together with a speed counter in a special desktop console. When working according to the disk-to-disk scheme on a machine, ­contact fatigue tests of samples can also be carried out, which are necessary for simulating the operation of gears, wheels and rails ­of railway transport, rolling bearings, etc.



drawing - 3.


Technical characteristics of the friction machine SMTs-2
Types of tested friction pairs disk - disk; disk - block; shaft - bushing.
Lead sample rotation frequency, s ^-1 5; 8.33; 16.66.
Slip coefficient, % 0; 10; 15; 20; 100.
Maximum load on samples, N:
with a closed circuit (rolling friction) 100 - 2000;
with an open circuit (sliding friction). . . 200 - 5000.
Load measurement error, % ±5.
Maximum friction moment, Nm 15.
Friction moment measurement error, % ±5.
Momentometer type. . . . electric.
Test in environments lubrication, abrasive.
Lab №1
COEFFICIENT OF METAL FRICTION
METHOD OF DETERMINATION

PURPOSE OF THE WORK: To study the method for determining the coefficient of friction of metals.

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 flat 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 is the normal load.