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February 6, 2012
 


Alexander A. DMITROVICH
Alexander A. DMITROVICH
Head of the Research Laboratory

RESEARCH LABORATORY OF FRICTIONAL AND ANTIFRICTIONAL MATERIALS

          Main problems of the laboratory are the following:


  • development of experimental and theoretical works in the field of production of new powder materials of a tribotechnical purpose and perfection of existing ones; methods of their diagnostics;
  • development of effective technological processes of production of frictional and antifrictional materials and products thereof by powder metallurgy methods;
  • fundamental investigations of processes of friction and wear of materials of a tribotechnical purpose;
  • investigation of properties of the surface, development of new methods and means of its diagnostics;
  • development of new methods of testing materials and means of their realization; carrying out friction and wear tests by traditional and new methods;
  • patenting of innovations in the field of materials of a tribotechnical purpose and technologies of their production in our country and abroad.

FRICTIONAL MATERIALS

         Different frictional compositions being designed for use in different conditions of friction in a wide range of velocities and loads; in both wet conditions and in dry ones; have been developed in the laboratory. The emphasis is placed on the decrease of product cost and production of ecologically pure frictional materials. Developed powder frictional materials on the base of copper and iron do not contain asbestos; in addition, by-products and wastes of different kinds of production (i.e. production of ball bearings) are widely used in their compound.

          The output of pilot and industrial batches of products as disks with the diameter up to 600mm, sectors and blocks with the thickness of an active layer from 0,5mm up to 30mm,is set up on the pilot plant according to developed technologies.


Frictional materials operating without lubricant
Frictional materials operating without lubricant
  • friction coefficient - 0,3…0,6;
  • wear-out rate - 20 um/km
  • initial sliding velocity 10<50≤m/s;
  • maximum load Ð - 2,0 MPa
Frictional materials operating in oil
Frictional materials operating in oil
  • friction coefficient - 0,04 … 0,14;
  • wear-out rate - 2…5 um/km
  • initial sliding velocity - V≤50 m/s;
  • maximum load Ð≤4,0 ÌÏà;




ANTIFRICTIONAL MATERIALS

         Powder compositions on the base of iron-graphite-copper with additives of a molybdenum disulphide and other solid lubricants have high antifrictional properties while operating in friction centers. A preliminary impregnation of porous parts by liquid oils with the following installation in friction centers and units requiring a periodical lubrication, permits to reduce maintenance costs, and in certain cases, to liquidate them completely with a guarantee of the presence of liquid lubricants in friction centers for whole service live of the construction.

          The main direction of a research work is the improvement of antifrictional properties of powder bronzes due to additives of solid lubricants in their compound and optimization of their porosity, as well as substitution of bronze castings by powder materials on the base of iron in friction centers. In the first place provided is the increase of a carrying capacity of powder materials, in the second place, economies of raw materials being in short supply while achieving a carrying capacity of bronze castings.

Stator of the pump of steering hydraulic booster
Stator of the pump of steering hydraulic booster

The use of a developed powder material to produce stators of pumps of steering hydraulic booster provides the increase of their service life 1,5-2 times to compare with the stator from SH-15 steel.
Inserts of trolleybus current collector
Inserts of trolleybus current collector

Due to a low bulk density of the powder being used as main component of SH-15 steel it is possible to add up to 40 vol.% graphite, as lubricant and current conductive element.

Insert life:

  • in dry weather 700 - 1000km
  • in rainy weather 300 - 400km.

They differ in a smooth passage of elements of contact mains
Powder plain bearings
Powder plain bearings

  • porosity - 10-25%;
  • coefficient of friction in oil - 0,004-0,02;
  • coefficient of friction at a bounded lubrication - 0,008-0,03
  • limiting load - up to 10 MPa at sliding velocity up to 4 m/s


TRIBOTECHNICAL TESTS OF MATERIALS

         Tribotechnical tests of materials are carrying out in a wide range of velocities and loads using traditional and original methods in conditions of friction with lubrication, without lubrication and in vaccuum. The laboratory has a friction machine for tests under different schemes and in different conditions. Tests are carrying out by schemes "shaft-bush", "shaft-shaft", "finger plane", "sphere-plane". Three inertial stands enable to carry out tests of frictional materials in conditions maximally approximate to real friction centers (frictional coupling; brakes; clutches and etc.). Laboratory research workers have experience in the development of methods of tribotechnical tests and means of their realization.
Friction machine like ÀÅ-5
Friction machine like ÀÅ-5
  • Scheme of tests - "plane - three finger samples";
  • Linear speed from 1 up to 11 m/s.;
  • Load - up to 5000 Í.

Controlled parameters: frictional torque, temperature, and inspection of a surface state with the use of Kelvin sensor.
Friction machine like ÌÒ-3
Friction machine like ÌÒ-3
  • Scheme of tests "plane - finger", "plane - sphere";
  • Rotational speed of the shaft - 350 - 5000 min-1;
  • Load - up to 500Í.

Controlled parameters: frictional torque, temperature, and inspection of a surface state with the use of Kelvin sensor. Recording and control are completely automated.

Friction machine like MT-1
Friction machine like ÌÒ-1
  • Scheme of tests "shaft-bush", "shaft-shaft", "shaft-insert";
  • Rotational speed - 75 - 1500 min-1;
  • Load - up to 5000 Í

Controlled parameters: frictional torque, temperature, and visual inspection of the surface
Inertial stand like IM-58
Inertial stand like ÈÌ-58
  • Scheme of tests "plane-plane";
  • Starting speed 4 - 20 m/s;
  • Specific load 0,4 - 4,0 MPa;
  • Maximum operation 54,5 kJ

Tests are carrying out with lubrication and without it.



INVESTIGATION OF THE MATERIAL SURFACE

         Principally new methods and devices permitting to control the state of a thin surface layer of the material, in recording changes of the work of an electron exit, have been developed in the laboratory. The monitoring of changes of the work of an electron exit is realized by measurement of the contact potential difference between an investigated surface and a surface of a standard sample. This method monitoring changes of the work of an electron exit permits to carry out investiga-tions both continuously during a friction process and by scheme of a Kelvin scanning probe. Series of Kelvin sensors have been developed. These sensors enable to record the signal in the range 1V in error by 5%.

         The equipment monitoring the topology of the work of an electron exit of the surface of investigated materials has been developed and produced in the laboratory. Control of the scanning system and recording of values are completely automated. Results are presented as three-dimensional plot.

Topology of the work of an electron exit of a steel sample after a point load by a ball of 10 mm.
Topology of the work of an electron exit of a steel sample after a point load by a ball of 10 mm.
Technical performance of the equipment:
  • monitoring of the topology of the work of an electron exit of the investigated surface;
  • measurement of the thickness of investigated films and coatings;
  • investigation of the kinetics of adsorption;
  • measurement of the surface stress and registration of the surface inhomogeneity.
Equipment monitoring the topology of the work of an electron exit
Equipment monitoring the topology of the work of an electron exit
Main technical data:
Overall dimensions - 1200õ600õ600 mm;
Weight - 70 kg;
Power consumption - 0,45 kW;
Size of an operation zone - 170õ170 mm;
Displacement speed - up to 50 mm/s;
Range of measurement of the potential 2.5 V;
Measurement error - 5%;
Surface of the standard sample - 0,5 mm2
Accuracy of positioning 0,05 mm
Resolution of the sensor in a horizontal plane 0,05 mm