14. starptautiskā konference 2012 - Latvijas Jūras akadēmija

Proceedings of 14th International conference „Maritime Transport and Infrastructure - 2012”Fig. 3 Rheological curves for different modelsThe effect of temperature and time on actual area of contact most perceptibly appears duringplastic contact. The growth of the actual area of contact with raise of temperature is mainly due to theraise of plasticity that has an exponential dependence. Time dependence of the actual area of contact ata constant load (for metals) is satisfactorily described by the equation:m m m rt N(t2 t1) / HBtHB,(10)where rt- change of the actual area of contact during the time intervalm mt t2 1 ; N – thetime of ball tip load determining Brinell hardness, m - rheological constant of the material.Assessment of contact deformations, considering the microgeometry of the surfaces and theheterogeneity of the mechanical properties of surface layers, surface films, and the stress distributionin the surface layers is necessary for the calculation of nodes with minimal friction and high wearresistance.During the capillary adhesion condensation of water vapors leads to the formation of thinliquid films on solid surfaces. In this case, the force of capillary adhesion Pa on a single microprotrusion is defined by the formula [2]:P a 4R (1 ), (11)where - thickness of the liquid film.Contact characteristics in the presence of a liquid film depends on the shape of the stamp, thebilateral attraction of two molecular roughness, the energy dissipation in the loop "convergingremoval"roughness (Fig. 4), etc. a bFig. 4 The scheme of the convergence of the contacting surfacesа – initial position; b – end position and deformation of the protrusion.146