14. starptautiskā konference 2012 - Latvijas Jūras akadēmija

Proceedings of 14th International conference „Maritime Transport and Infrastructure - 2012”R m a xR W m a xFig.1 Main characteristics of the rough surface geometryWell-known theoretical approaches to calculate the actual contact area [1, 2] do not take intoaccount the effect of time of loading and temperature of the contacting surfaces of solids. However, allmaterials to a greater or lesser extent have the viscoelasticity and viscoplasticity, i.e. elastic and plasticdeformation does not affect immediately after loading, but progress after some time.2. Rheologic properties of contactThe rate of increase of deformation increases with raise of temperature. Such behavior ofmaterials, leading to a change in the actual contact area depending on the temperature and time, isdescribed by means of rheological models. Rheology - a set of deformation study methods for studyingthe deformation and flow of media having a viscosity and plasticity. In Fig. 2a, b, c are shown themost often used models describing the rheology of materialsFig. 2 Rheological model for the interaction of solidsThe first model (see Fig. 2a) describes the ideal elasticity (Hooke's body): .(1)The second model (see Fig. 2b) reflects the viscous flow (Newton’s body). For it appliesNewton's formula: d dt., (2)here d- relative offset deformation.The third model (Fig. 2, c) describes the plastic deformation (Saint-Venant’s body): т sign ,(3)where the “sign” stands for variable gradual function. If т , then the elements 1 and 2 (seeFig. 2c) are one unit. 0,if т – elements slide relative to each other. The body is indefinitelyplastically deformed if .. This is followed by a combination of the first three models (see Fig.2, d, e, f), reflecting at first approximation, the properties of actual solids.144