Methods for calculation and experimental evaluation of nucleation and development of the fatigue damages in tin based babbitt and babbitt lining of plain bearings

Fatigue damage to babbitt layers of plain bearings is often manifested during operation. The goal of the study is to develop a model for accumulation of the fatigue damage and destruction of antifriction materials and layers of plain bearings. A generalized fatigue diagram of tin-based babbitts including the main stages of fatigue damage and a diagram of the fatigue damage development in the antifriction layer of plain bearings are presented. The generalized model of V. V. Bolotin for damage accumulation and destruction is modified with regard to antifriction materials containing rather large structural elements. An explicit (direct) modeling of damage processes appeared possible for such materials. The model describes dissipated accumulation of microcracks (interpreted as destruction of the elements of the material structure), initiation and development of a system of short cracks, initiation and development of macro-cracks up to the limit state of the object. The model suggests discretization of the volume into sections with constant levels of complex stress state and discretization of the time axis into the intervals (blocks of loading cycles). The problem of identifying the parameters of a multistage model of the fatigue damage accumulation in the alloy is solved proceeding from the analysis of the results of testing babbitt specimens. We used the simplest optimization procedure, i.e., the method of deformable polyhedron. The parameters of the power function in the dependence of the rate of microdamage accumulation on the level of stresses are obtained. The parameters of the initiation and development of the crack system in the babbitt layer are obtained from the analysis of experimental results of studying steel-babbitt samples. The problem of calculating the durability of antifriction babbitt layers required the development of a new software. The program is examined by comparing calculated and experimental values of the durability of fatigue-tested bearing specimens forced against a rotating shaft by varying cyclic load. The calculated values of the durability match the experimental which confirms the performance of the calculated model.

Theoretical research of the technology of finishing cylinders with antifriction materials

The article analyzes the research aimed at the use of various materials, additives and additives to oils. It is established that their application is mainly limited to the stages of operation, bench and operational running-in. The use of antifriction materials at the stage of processing the parts of internal combustion engines, limiting the resource, is small, despite the fact that such treatment reduces the running-in time and improves the finish of the friction surfaces. Theoretical calculation of the parameters of the working surface of the engine cylinder liner during their finishing using special antifriction materials showed a 2-fold increase in the bearing surface (from 0.2 to 0.4 of the nominal surface area at the level of the middle line of the profile) and a roughness of 0.27 μm, which is close to the values after the bench run-in. This proves the possibility of using this treatment in order to reduce the time of preparation of CNG and improve the characteristics of the surfaces to be worked. It is established that the finishing of engine cylinder liners with antifriction materials should be carried out at the contact pressure of the working tool (brass bars) on the surface of the sleeve 3 MPa, the speed of the working tool 5.5 m/s, the processing time of the sleeve 20 min. Finishing of sleeves with use of compositions TSK-B100 + SURM-KV, SURM-UO and RVS allows to reduce mechanical losses on friction in TsPG by 5-19% at the beginning of process of running in after processing in comparison with mechanical losses at the end of cold running in without finishing sleeves; to obtain the roughness parameters after finishing the same as after cold running in without additional processing of the sleeves; increase the bearing surface by 2 - 2.5 times (from 0.2 - 0.25 to 0.4 - 0.5 of the nominal surface area at the level of the middle line of the profile), which confirms the calculated data. The final treatment of sleeves with compositions based on antifriction materials TSK-B100 + SURM-KV, SURM-UO and RVS allows to provide values of parameters of a working surface of sleeves (reduction of roughness, increase of a basic surface) approaching their values after cold running in, therefore allows to increase contact loadings. in the connection "sleeve - piston ring" after this treatment and reduce the time of the bench run-in (to the values required for the attachment of other engine connections).

Creation of theoretical bases of tribotechnologies of running-in and restoration as means of effective increase of operational wear resistance of motor transport and mobile agricultural machinery

The bases for creation of theoretical bases of tribotechnologies of running-in and restoration of conjugations of details of systems and units of motor transport and mobile agricultural machinery are defined. The specifics of selective transfer on the surface of contacting parts of machines and creation of servito films, formation of coatings during running-in and restoration from antifriction materials, which are a part of additives in motor and transmission oil, are considered. A number of tribophysicochemical processes that occur in the conjugations of parts materials and how they affect the creation of tribotechnologies of running-in and restoration are clarified. The creation of tribotechnologies using geomodifiers is considered. It is proposed to build a single theory of tribotechnologies of running-in and recovery on the basis of the mechanism of triboplasm formation in the conjugations of parts of systems and units of machines. It is also proposed to add to this the thermofluctuation theory of S.M. Zhurkova taking into account the change of dilaton and compression bonds of atoms of materials of tribocouples of details with creation of local areas of deformations of compression and tension and zones of thermoplastic deformation.

POLYMER MATERIALS FOR ANTIFRICTION COATINGS (review)

An overview of polymeric materials of various structures used as antifriction materials is given. The experience of using various polymeric materials for the manufacture of antifriction coatings is considered. The advantages of thermosetting and thermoplastic polymers in comparison with metallic materials are revealed. Some compositions of carbon and organoplastics developed for plain bearings are described. A conclusion is made about the direction of research in the development of new binders for antifriction materials.

REINFORCED COMPOSITE SLIDING BEARINGS

The aim of the work is a design substantiation of sliding bearings with wedges made of new antifriction reinforced wood-metal materials having increased tribo-technical properties ensuring potentialities for their industrial use widening. The wear investigation of the materials offered was carried out according to the procedure providing for an abrasive impact at that besides wear-resistance the thermo-physical characteristics of samples under analysis were assessed. As a result of the investigation there was offered a structure of anti-friction materials combining in them modified wood and a metal filling agent made of different antifriction materials or special capsules filled with fusible materials and also wedges made by means of a joint coiling of a metal band or an element as tensile anti-friction springs and sized bands of veneer. The offered reinforced composite sliding bearings allow ensuring higher mechanical and tribo-technical characteristics to a considerable extent, optimizing a thermal working mode of sliding bearing wedges, increasing considerably their manufacturability and widening a sphere of industrial use by means of rational combining different wood types and metal composite constituents.