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A three-dimensional sliding model of micro-scale was established between two rough surfaces exhibiting fractal behavior,and the thermo-mechanical coupling factor in the process of contact was considered. The surface temperature in sliding processes was analysed using the finite element analysis taking into account Ti-6Al-4V elastic-plastic properties with material failure. The transient surface temperature distribution of the rough surface was presented. The numerical results showed that the surface temperature in initial time rise sharply and then tend to be temporarily stable until a new contacted asperity coming into interaction. With the increase of friction slide distance the surface temperature was to present the state of fluctuating. The values of highest temperature at contact zones were different,while the highest temperature at contact zone was higher relative to the greater interface shear strength. Compared with the experimental data of the literatures,it was concluded that the rationality of the simulation,these results also deepened understanding the reason of the friction and wear.

To study the effect of solid body contact deformation on the real contact area, various models are established. These contact models include a contact model between an elastic rough solid and a rigid flat one (E-R model), an elasto-plastic rough solid and a rigid flat one (P-R model), an elasto-plastic rough solid and an elastic flat one (P-E model), an elasto-plastic rough solid and an elasto-plastic flat one (P-P model). The effects of thermo-mechanical coupling and the heat flux coupling are considered in the model which is solved by ABAQUS software. The results show that the real contact area is not only determined by the normal load, but also affected by the contact deformation mode of solid body. The real contact area from the purely elastic model (E-R model) is much smaller than that from the other elasto-plastic model. But the real contact area obtained from the P-R model is the largest. No matter what kind of the solid body contact deformation is, at the moment of the abrupt change of sliding speed and of the hot spotting coming into being, the real contact area increases noticeably, and then varies in a small range during the constant frictional sliding process. [ABSTRACT FROM PUBLISHER]

A three-dimensional model of an elasto-plastic rough surface featured by fractal geometry sliding over an elasto-plastic flat body is developed. The three-dimensional model considers the thermo-mechanical coupling and the heat flux coupling between the sliding surfaces. To obtain the transient real contact area, the problem under this three-dimensional model is solved by the finite element method. The results show that the real contact area is a small fraction of the nominal contact area during the loading and sliding process, and increases with the increase in the applied normal load. In the initial stage of friction sliding, the real contact area increases and fluctuates noticeably for the abrupt change of sliding speed, and then varies in a small range under the constant normal load and sliding velocity. It is also shown that frictional heating increases the real contact area, the instantaneous maximum contact pressure by comparing the results with those obtained from the same model, however, in which the thermal effect of frictional heat is not considered. That is to say, the real contact area is larger when the thermo-mechanical coupling is considered. It is crucial to take the thermo-mechanical coupling effect into account especially for the micro frictional sliding analysis. [ABSTRACT FROM PUBLISHER]

Lateral-force microscopy is a powerful tool to study the frictional properties of two-dimensional materials. However, few works distinctly reveal the correlation between the tip radius with the tip⁻sample distance and the frictional properties of the two-dimensional (2D) materials. We performed molecular-dynamics simulations to study the atomic-scale friction of a typical two-dimensional single-layer molybdenum disulfide (SLMoS₂). The effects of tip radius and tip⁻sample distance on the frictional properties were analyzed and discussed. The frictional force⁻sliding-distance curves show typical stick⁻slip behaviors, and the periodicity can be used to characterize the lattice constants of SLMoS₂. Sub-nanoscale stick-slip movements occur in one-lattice sliding periods along with only the armchair (AC) direction and only when the tip radius is smaller than 3 Å with 1.47 Å tip-sample distance. At the same tip⁻sample distance, a smaller tip can provide a more detailed characterization and higher-precision frictional properties of SLMoS₂. A larger tip is capable of providing comparative frictional properties of SLMoS₂ at a proper vertical tip⁻sample distance, compared with the small tip.