METHOD OF DETERMINING THE SURFACE TENSION AND SURFACE ENERGY OF TRIBOLOGICAL WEAR PARTICLES

Surface tension of friction wear product material is linked with unit mechanical work of newly-formed surfaces of solids. A definition of surface energy also addresses the thermal effect, which is indirectly connected with wear. Physical differences between the development of liquids and solids surfaces are discussed. Both of the quantities defined are described in analytical terms and their value is determined for a selected example of experimental testing. The discussion is based on the first law of thermodynamics using the concept of specific enthalpy of wear products. Boundaries of an area in space where mechanical energy is dissipated and dimensions of a wear particle being formed are taken into account. Mechanical and thermal parts of the energy balance are differentiated.

Testing oil for wear products presence as diagnostic method of operational state of marine gearbox unit

The article discusses the results of determining the concentration of wear products in oil of marine diesel gearbox units on fishing vessels in order to use them for in-place diagnostics without dismantling. It was stated that the ultimate goal of diagnostics of wear products consists of identifying the increased wear rate, taking appropriate measures and predicting a possible accident. There has been brought the statistics for several years of monitoring different gearbox types: TKG2-0350 unit of Atlantic-335 type ships, SL2×3000 unit of Horizont type ships, gearbox of Atlantic-488 type ship, main gearbox of Kiev type ship, gearbox of Alpinist type ship. A formula for theoretical determination of the wear product concentration in lubricating oil is given, and a curve of the changing concentration of wear products has been illustrated. Conclusions are made about the information content and reliability of using the wear product concentration as a diagnostic parameter to determine the technical condition of the gearbox. The main reasons for the low information content of the method for determining the wear products in oil are provided. High metal concentrations in wear products in lubricating oil do not necessarily confirm the fact of accidental wear of gearbox parts. Instead of disassembling the gearbox, which leads to decreasing its resources, it is necessary to carry out diagnostics using various methods. It is recommended to analyze the wear degree of gearbox parts at least twice a year (after every six months of operation). There have been offered the reliable ways for improving the wear product diagnostic method.

ANALYSIS OF THE RANGE OF THE SPECIFIC HEAT OF TRIBOLOGICAL WEAR PRODUCTS

This paper continues a discussion of specific heat cp’ of wear product material at the time of the products’ generation which was initiated in [L. 2]. The very high values of this quantity found on the basis of the laws of mass and energy conservation have inspired further analyses to possibly validate the results. System quantities C and D [L. 2] have played central roles in earlier modelling of the friction and wear of solids. They are determined for a certain range of the temperature of a macroscopic contact of solids Θ and serve the purpose of a merely approximate estimation of minimum cp’. An attempt at determining real values of cp’ for specific Θ without taking C and D into consideration has been undertaken in this study. The discussion was based on the energy balance equation for the stationary friction process which is associated with wear. The significance of friction parameters, the physical properties of a material subject to friction, and some characteristics of the tribological system have been emphasised. The analysis is also designed to determine maximum heat, cp’max, and a range of its variations, cp’min - cp’max. The resultant analytical dependences that characterise friction and its effects are illustrated with examples of selected experiments [L. 10], which were originally designed to estimate values of cp’ [L. 2]. The evaluation of cp’ discovers negligible differences between cp’ and cp’min. Important information has additionally been acquired about the values of the flash temperature, Θo, and its relations to temperature D. No regular impact of on the specific heat of wear products has been determined.