China
Africa
Explore chapters and articles related to this topic
Mixed Lubrication with Rough Surfaces
Published in Q. Jane Wang, Dong Zhu, Interfacial Mechanics, 2019
Mixed lubrication is the interfacial mechanism in which the total applied load is supported by both hydrodynamic lubricant films and surface asperity contacts. Because a vast majority of lubricated components operate in this regime, and it is also a critical transition from full-film to boundary lubrication, and possibly to lubrication breakdown and surface failures, a good understanding of mixed lubrication is extremely important in both lubrication theory and engineering practice. However, there have been great challenges to researchers who attempt to fully explore the mixed lubrication characteristics. The main challenges are stated below.
On pressure-driven Hele–Shaw flow of power-law fluids
Published in Applicable Analysis, 2022
John Fabricius, Salvador Manjate, Peter Wall
Poiseuille's law also plays an important role in lubrication theory, formulated in the Newtonian case by Reynolds [16], see also [17, Ch. 22]. Recall that the fundamental problem in lubrication theory is to describe fluid flow in the gap between adjacent surfaces which are in relative motion to each other and in general there are no obstacles in the domain. Bayada and Chambat [18], gave the first rigorous mathematical derivation of Reynolds equation, considering the Stokes problem in a thin domain and assuming that the velocity field satisfies a Dirichlet condition on the whole boundary. The authors proved that the limit pressure satisfies the classical Reynolds equation with a Neumann condition. In contrast, our limit equation has a Dirichlet condition for the pressure. The connection between Hele–Shaw theory and lubrication theory has been further explored in [19]. A lubrication problem with power-law fluids was considered in [20], under the assumption that the lower surface is flat and moving whereas the upper surface is rough and stationary. Flow of power-law fluids through a thin porous medium, i.e. periodic array of vertical cylinders confined between two parallel plates with no-slip boundary condition on the whole boundary was studied in [21].
The Effects of Magnetic Treatment on the Tribological Behavior of AISI 1045 Steel under Lubricated Conditions
Published in Tribology Transactions, 2018
Xiang Xi, Yanqiu Xia, Yichao Hu
In boundary lubrication theory, the formation of an adsorption layer or generation of a surface chemical reaction film is the dominant factor in reducing friction and wear. EDS analysis of the tribofilm formed by additive-modified lubricants demonstrated that, under boundary lubrication conditions, some additives adsorbed onto the worn surfaces and others decomposed and reacted with the worn surfaces during friction to form a tribofilm, resulting in reduced friction and wear (Feng and Xia (37)). According to previous studies (Han, et al. (18); Jiang, et al. (19); Abdeljaber, et al. (41)), magnetic fields could promote tribological chemical reactions, which were attributed to the following reasoning. Oxide particles were frequently crushed between surfaces and fresh metal was continuously exposed, such that, under these rigorous conditions, additives reacted more actively with freshly exposed metal surfaces to generate a more effective tribofilm. Then the tribofilm carrying capacity on the treated surface improved, such that the worn surfaces of treated disks were flat and their real-time friction coefficients were stable. By comparison, without the effects of micromagnetic fields, the worn surfaces of untreated disks were uneven and the real-time friction coefficients were unstable, which was attributed to cracking of the tribofilm under high normal load during sliding. In conclusion, both the adsorbed and chemical layers on the treated disk surfaces played antifriction and antiwear roles during the sliding process, leading to better lubrication effects.