https://cyberleninka.org/article/n/544115.pdf

Hydrodynamic lubrication of textured surfaces: A review of modeling techniques and key findings

The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part. (Some figures may appear in colour only in the online journal)

https://iopscience.iop.org/article/10.1088/0022-3727/47/1/013001/pdf

Mechanical properties of nanoparticles: basics and applications

The theory and recent applications of waves in periodic structures are reviewed. Both the Floquet and coupled waves approach are analyzed in some detail. The theoretical part of the paper includes wave propagation in unbounded and bounded active or passive periodic media, wave scatterring from periodic boundaries, source radiation (dipole, Cerenkov, transition, and Smith-Purcell) in-periodic media, and pulse transmission through a periodic slab. The applications part covers the recent development in a variety of fields: distributed feedback oscillators, filters, mode convertors, couplers, second-harmonic generators, deflectors, modulators and transducers in the fields of integrated optics and integrated surface acoustics. We also review the work on insect compound eyes, mehanical structures ocean waves, pulse compressions, temperature waves, and cholestric liquid crystals. Particles interaction with crystals is briefly reviewed, especially in the case of zeolite crystals and supelattices. Recent advances in fabrication techniques for very fine gratings me also covered. Finally, speculations about future problems and development in the field of waves in periodic structures are given.

/pdf/waves-in-active-and-passive-periodic-structures-a-review-1rmm6yq97w.pdf

Waves in active and passive periodic structures: A review

A mechanical seal subjected to laser surface texturing over an annular portion of one of its mating rings is theoretically and experimentally investigated. The partial surface texturing provides a mechanism for hydrostatic pressure build up in the sealing dam similar to that of a radial step or face coning. Optimization of the surface texturing parameters to obtain maximum hydrostatic pressure effect is performed on a theoretical model. A test rig that allows friction torque and temperature measurements in a back-to-back double seal arrangement is used to validate the surface texturing effect. It is found that optimally textured seals generate substantially less friction and heat. Moreover, a simple unbalanced seal, limited in its pressure capacity, can be easily transformed by surface texturing to an equivalent balanced seal with much higher pressure capability. Presented at the 57th Annual Meeting Houston, Texas May 19–23, 2002

A Laser Surface Textured Hydrostatic Mechanical Seal

https://escholarship.org/content/qt4hw2r7qc/qt4hw2r7qc.pdf?t=krne51

Material Removal Mechanisms in Lapping and Polishing

A Computational Method for Cavitation in a Wavy Mechanical Seal

The behavior of a fluid-film bearing depends on the boundary conditions at the interfaces between the liquid and the solid bearing surfaces. For almost all solid surfaces, the no-slip boundary condition applies. However, a number of researchers have recently found that slip can occur with specially engineered surfaces. These include molecularly smooth surfaces and surfaces with micron-scale patterns. By constructing an engineered heterogeneous surface on which slip occurs in certain regions and is absent in others, the flow in the liquid film of a bearing can be altered, and such characteristics as load support and friction can be improved. In the present study, a numerical analysis of a slider bearing with such an engineered slip/no-slip surface is analyzed. Slip is assumed to occur when a critical shear stress is exceeded and follows the Navier relation. The results show that with a critical shear stress of zero, a significant increase in load support and decrease in friction can be achieved with an app...

Numerical Analysis of a Slider Bearing with a Heterogeneous Slip/No-Slip Surface

An average Reynolds equation capable of predicting the effects of roughness induced inter-asperity cavitation is introduced. The average Reynolds equation is based on the JFO cavitation model and the Patir and Cheng flow factor method. The flow factors are calculated in numerical experiments as functions of the local surface separation, surface statistics, and cavitation number. The model is extended into a universal average Reynolds equation capable of predicting the combined effects of inter-asperity cavitation and macroscopic cavitation. Both the Patir and Cheng method and the present model are verified in numerical experiments.

An Average Flow Model of Rough Surface Lubrication With Inter-Asperity Cavitation

A numerical model of an elastomeric reciprocating hydraulic rod seal has been constructed. The model consists of coupled fluid mechanics, deformation mechanics and contact mechanics analyses, with an iterative computational procedure. The fluid mechanics analysis consists of the solution of the Reynolds equation, using flow factors to account for surface roughness. Deformation of the seal is computed through the use of influence coefficients, obtained from an off-line finite element analysis. The contact mechanics analysis uses the Greenwood and Williamson model. The seal model is used to predict leakage rate, friction force, fluid and contact pressure distributions, and film thickness distribution. Results for a typical seal show that the seal operates with mixed lubrication, and the seal roughness plays an important role in determining whether or not the seal leaks.Copyright © 2006 by ASME

Numerical Model of a Reciprocating Hydraulic Rod Seal

The no-slip boundary condition is part of the foundation of the traditional lubrication theory. It states that fluid adjacent to a solid boundary has zero velocity relative to the solid surface. For most practical applications, the no-slip boundary condition is a good model for predicting fluid behavior. However, recent experimental research has found that for certain engineered surfaces the no-slip boundary condition is not valid. Measured velocity profiles show that slip occurs at the interface. In the present study, the effect of an engineered slip/no-slip surface on journal bearing performance is examined. A heterogeneous pattern, in which slip occurs in certain regions and is absent in others, is applied to the bearing surface. Fluid slip is assumed to occur according to the Navier relation. Analysis is performed numerically using a mass conserving algorithm for the solution of the Reynolds equation. Load carrying capacity, side leakage rate, and friction force are evaluated. In addition, results are presented in the form of Raimondi and Boyd graphs. It is found that the judicious application of slip to a journal bearing’s surface can lead to improved bearing performance.

http://www2.eng.cam.ac.uk/~mpfs/papers/articles/WTC2005/pdfs/t-8/WTC2005-63088.pdf

Richard F. Salant

Papers

A Computational Method for Cavitation in a Wavy Mechanical Seal

Numerical Analysis of a Slider Bearing with a Heterogeneous Slip/No-Slip Surface

An Average Flow Model of Rough Surface Lubrication With Inter-Asperity Cavitation

Numerical Model of a Reciprocating Hydraulic Rod Seal

Numerical Analysis of a Journal Bearing With a Heterogeneous Slip/No-Slip Surface