Yuri Kligerman

Analytical and Experimental Investigation of Laser-Textured Mechanical Seal Faces

An analytical model is developed to predict the relation between the opening force and operating conditions in a mechanical seal with laser textured microsurface structure in the form of micropores. The model is valid for any desired shape of the micropores. An optimization is performed for spherical shape micropores evenly distributed on one of the mating rings face to maximize the opening force and fluid film stiffness. Results of a parametric study are presented showing the effect of the main design parameters on the seal performance. Some results of an experimental investigation with water-lubricated seal rings are also shown and compared with the theoretical model. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998

A Laser Surface Textured Parallel Thrust Bearing

The potential use of a new technology of laser surface texturing (LST) in parallel thrust bearings is theoretically investigated. The surface texture has the form of micro-dimples with pre-selected diameter, depth, and area density. It can be applied to only a portion of the bearing area (partial LST) or the full bearing area (full LST). Optimum parameters of the dimples, and best LST mode, are found in order to obtain maximum load carrying capacity for a thrust bearing having parallel mating surfaces. A comparison is made with optimum linear and stepped sliders showing that parallel LST sliders can provide similar load carrying capacity. Scheduled for Presentation at the 58th Annual Meeting in New York City April 28–May 1, 2003

Friction-Reducing Surface-Texturing in Reciprocating Automotive Components ©

A model is presented to study the potential use of micro-surface structure in the form of micro pores to improve tribological properties of reciprocating automotive components. The Reynolds equation and the equation of motion are solved simultaneously for a simplified “piston/cylinder” system with surface texturing. The solution provides the time behavior of both the clearance and the friction force between the “piston ring” and “cylinder liner” surfaces. It is shown that surface texturing can efficiently be used to maintain hydrodynamic effects even with nominally parallel surfaces. It is also shown that optimum surface texturing may substantially reduce the friction losses in reciprocating automotive components. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001

Experimental Investigation of Laser Surface Texturing for Reciprocating Automotive Components

An experimental study is presented to evaluate the effectiveness of micro-surface structure, produced by laser texturing, to improve tribological properties of reciprocating automotive components. The test rig and test specimens are described and some test results are presented. Good correlation is found with theoretical prediction of friction reduction on a simple, yet representative, test specimen. Potential benefit of the laser surface texturing under conditions of lubricant starvation is also presented. Finally, friction reduction with actual production piston rings and cylinder liner segments is demonstrated. Presented at the 57th Annual Meeting in Houston, Texas May 19–23, 2002

Improving tribological performance of piston rings by partial surface texturing

An analytical model is developed to study the potential use of part ial laser surface texturing (LST) for reducing the friction between a piston ring and cylinder liner. The hydrodynamic pressure distribution and the time dependent clearance between the pi ston ring and cylinder liner are obtained from a simultaneous solution of the Reynolds equation and the ring equation of motion in the radial direction. The time behavior of the fric tion force is calculated from the shear stresses in the viscous fluid film and the time de pendent clearance. An intensive parametric investigation is performed to identify the m ain parameters of the problem. The optimum LST parameters such as dimples depth, texture area density and textured portion of the nominal contact surface of the piston ring are evaluated.

Experimental Investigation of Laser Surface Textured Parallel Thrust Bearings

Performance enhancements by laser surface texturing (LST) of parallel-thrust bearings is experimentally investigated. Test results are compared with a theoretical model and good correlation is found over the relevant operating conditions. A comparison of the performance of unidirectional and bi-directional partial-LST bearings with that of a baseline, untextured bearing is presented showing the benefits of LST in terms of increased clearance and reduced friction.

Analysis of the Hydrodynamic Effects in a Surface Textured Circumferential Gas Seal

A theoretical finite-element model was developed to study the hydrodynamic effect of micro-pores generated by laser surface texturing (LST) in a circumferential gas seal. The seal is represented by two non-contacting annular surfaces of a rotating shaft and a stationary ring. The micro-pores of spherical segment shape are distributed uniformly over one of the annular surfaces. The hydrodynamic dimensionless pressure distribution in the uniform clearance between the annular surfaces is obtained from a solution of the Reynolds equation for compressible viscous gas in a laminar flow. Results of a parametric study along with a numerical example for a specific circumferential seal demonstrate a substantial hydrodynamic effect that can raise the opening average pressure in the seal clearance above the ambient one by up to 50 percent. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001

Experimental Investigation of Partial Laser Surface Texturing for Piston-Ring Friction Reduction

An experimental study is presented to evaluate the effect of partial laser surface texturing (LST) on friction reduction in piston rings. In a previous study, 30% friction reduction was obtained with full LST where the full width of the piston ring is textured with a very large number of microdimples that act individually as microhydrodynamic bearings. In partial LST, only a portion of the piston-ring width is textured with high dimple density, producing a “collective” effect of the dimples that provides an equivalent converging clearance even with nominally parallel mating surfaces. Experimental results obtained with flat and parallel test specimens with partial LST are presented, confirming a previously published theoretical model and the advantage of partial over full LST. Friction reduction by LST with actual production-crowned piston rings and cylinder liner segments is not straightforward and needs further investigation. Presented at the STLE Annual Meeting in Las Vegas, Nevada May 15-19, 2005 Review led by Gray Barber

The Validity of the Reynolds Equation in Modeling Hydrostatic Effects in Gas Lubricated Textured Parallel Surfaces

Microdimples generated by laser surface texturing (LST) can be used to enhance performance in hydrostatic gas-lubricated tribological components with parallel surfaces. The pressure distribution and load carrying capacity for a single three-dimensional dimple, representing the LST, were obtained via two different methods of analysis: a numerical solution of the exact full Navier-Stokes equations, and an approximate solution of the much simpler Reynolds equation. Comparison between the two solution methods illustrates that, despite potential large differences in local pressures, the differences in load carrying capacity, for realistic geometrical and physical parameters, are small. Even at large clearances of 5% of the dimple diameter and pressure ratios of 2.5 the error in the load carrying capacity is only about 15%. Thus, for a wide range of practical clearances and pressures, the -Simpler approximate Reynolds equation can safely be applied to yield reasonable predictions for the load carrying capacity of dimpled surfaces.

A Model for Junction Growth of a Spherical Contact Under Full Stick Condition

The evolution of the contact area (junction growth) of an elastic-plastic preloaded spherical contact subjected to an additional tangential loading is investigated theoretically. The normal preloading, under full stick condition, leads to the formation of a junction that can support additional tangential load. A gradual increase of this tangential load, while the normal preload remains constant, can incept plasticity of the contact zone in case the initial normal preload was elastic or enhance an existing one, thus lowering the tangential stiffness of the junction. Finally, the tangential stiffness approaches zero, which corresponds to sliding inception (i.e., loss of stability). The evolution of the contact area during the tangential loading prior to sliding inception reveals an essential junction growth which depends on the magnitude of the normal preload. The mechanism causing this junction growth seems to be new points of the sphere surface, which originally lay outside of the initial contact area that are coming into contact with the rigid flat during the tangential loading. The theoretical results for the junction growth obtained in the present work correlate well with some limited experiments.