This paper investigates the effects of differential scheme and mesh density on elastohydrodynamic lubrication (EHL) film thickness based on a full numerical solution with a semi-system approach. The solution variation with different schemes and mesh sizes is revealed based on a set of numerical cases in a wide range of central film thickness from several hundred nanometers down to a few nanometers. It is observed that when the film is thick, the effects of differential schemes and mesh density are not significant. However, if the film becomes ultra-thin, e.g., below 10‐20 nanometers, the influence of mesh density and differential schemes becomes more significant, and a proper dense mesh and differential scheme may be highly desirable. The present study also indicates that the solutions from the 1st-order backward scheme give the largest film thickness among all the solutions from different schemes at the same mesh size. DOI: 10.1115/1.2194916

Effects of Differential Scheme and Mesh Density on EHL Film Thickness in Point Contacts

Hydraulic seals are complicated machine elements. The engineering research on hydraulic reciprocating seals, which commenced roughly in the 1930s, has achieved a basic understanding of performance issues. This article provides a review of the experimental and theoretical research conducted over a period of eight decades, discussing more than 200 of the most significant publications from the related literature. The topics discussed include reciprocating seal designs, materials, experimental methods, theoretical studies, elastohydrodynamic lubrication, solid and contact mechanics, performance issues, and optimization.

Eighty years of research on hydraulic reciprocating seals: Review of tribological studies and related topics since the 1930s

Elastohydrodynamic Lubrication (EHL) is commonly known as a mode of fluid-film lubrication in which the mechanism of hydrodynamic film formation is enhanced by surface elastic deformation and lubricant viscosity increase due to high pressure. It has been an active and challenging field of research since the 1950s. Significant breakthroughs achieved in the last 10–15 years are largely in the area of mixed EHL, in which surface asperity contact and hydrodynamic lubricant film coexist. Mixed EHL is of the utmost importance not only because most power-transmitting components operate in this regime, but also due to its theoretical universality that dry contact and full-film lubrication are in fact its special cases under extreme conditions. In principle, mixed EHL has included the basic physical elements for modeling contact, or hydrodynamic lubrication, or both together. The unified mixed lubrication models that have recently been developed are now capable of simulating the entire transition of interfacial status from full-film and mixed lubrication down to dry contact with an integrated mathematic formulation and numerical approach. This has indeed bridged the two branches of engineering science, contact mechanics, and hydrodynamic lubrication theory, which have been traditionally separate since the 1880s mainly due to the lack of powerful analytical and numerical tools. The recent advancement in mixed EHL begins to bring contact and lubrication together, and thus an evolving concept of “Interfacial Mechanics” can be proposed in order to describe interfacial phenomena more precisely and collaborate with research in other related fields, such as interfacial physics and chemistry, more closely. This review paper briefly presents snapshots of the history of EHL research, and also expresses the authors’ opinions about its further development as a gateway to interfacial mechanics. [DOI: 10.1115/1.4004457]

Elastohydrodynamic Lubrication: A Gateway to Interfacial Mechanics—Review and Prospect

Free abrasive machining (FAM) process associated with the wiresaw wafer slicing involves a three body abrasion environment. During the process, the cutting action is caused by fine abrasives freely dispersed in the slurry, which get trapped between an axially moving taut wire and the ingot being sliced. In this paper a model is proposed wherein the entry of abrasives into the cutting zone is governed by elasto-hydrodynamic (EHD) interaction between the slurry and the wire. An EHD film is formed by the abrasive carrying viscous slurry, squeezed between the wire and the ingot. This phenomenon is analyzed here using the finite element method. The analysis of such an interaction involves coupling of the basic Reynold’s equation of hydrodynamics with the elasticity equation of wire. Newton‐Raphson algorithm is used to formulate and solve this basic coupling. The finite element discretization of the resulting nonlinear equation is carried out using Galerkin’s method of weighted residuals. Basic hydrodynamic interaction model and the incorporation of the entry level impact pressure into the inlet boundary conditions are the two novel features introduced in this work. The analysis yields film thickness profile and pressure distribution as a function of wire speed, slurry viscosity, and slicing conditions. A perusal of results suggests that the wiresawing occurs under ‘‘floating’’ machining condition. The minimum film thickness is greater than the average abrasive size. This is practically very important since the wiresaw is used to slice fragile semiconductor wafers with severe requirements on the surface finish. The possible mechanism by which a floating abrasive can cause material removal is also touched upon in this work. Material removal rate has been modeled based on energy considerations. @S0742-4787~00!00702-5#

Elasto-Hydrodynamic Interaction in the Free Abrasive Wafer Slicing Using a Wiresaw: Modeling and Finite Element Analysis

The classical problem of elasto-hydrodynamic lubrication of cylinders in line contact is formulated as a non-linear complementarity problem. A direct algorithm is applied to the approximation obtained by finite differences. Implementation considerations are emphasized. The new method provides reliable and automatic location of the previously troublesome lubricant free boundary. Numerical results reveal the qualitative behaviour of the pressure distribution and the lubricant film thickness under variation of key physical parameters.

Elasto-hydrodynamic lubrication: A non-linear complementarity problem

A unified mathematical treatment of thick and thin film elastohydrodynamic lubrication problems is presented. The construction of approximate solutions is discussed by using Ritz-Galerkin methods with piecewise polynomial basis functions. In particular for the line contact problem, smooth Hermite and cubic spline spaces are used to obtain solutions over a wide load-speed range. Pressure ‘spikes’ are obtained.

S. M. Rohde

Papers

A unified treatment of thick and thin film elastohydrodynamic problems by using higher order element methods