Tribology Commons^™

Nonlinear Prediction Of Rotordynamic Coefficients For A Hydrodynamic Journal Bearing, Jerzy Sawicki, T.V.V.L. Rao

Jerzy T. Sawicki

In the analysis of hydrodynamic journal bearings, linearized stiffness and damping coefficients are widely used for the evaluation of stability and dynamic response characteristics. Under given operating conditions, these coefficients vary along the locus of the orbital response, and are not valid at large amplitudes (40% of the bearing clearance) of the journal motion. The time history of journal bearing motion for large vibrations is accurately predicted herein using nonlinear (time-transient) analysis. This paper discusses the adequacy of bearing analysis based on linearized coefficients and presents the significance of variation of the coefficients under the dynamic conditions. A method to …

Analytical Solution Of Piston Ring Pack Lubrication For Truck Air Brake Compressor, Biao Yu, Jerzy Sawicki, V. Dunaevsky

Jerzy T. Sawicki

This paper presents an analytical solution of piston ring pack lubrication for two-cylinder truck air brake compressor. A system of nonlinear equations with seven variables was developed to describe lubrication phenomena of the piston ring pack for both fully flooded and starvation conditions. The full mass conservation boundary conditions defined by JFO ([ 14 ],[ 15 ]) theory were employed for complete description of the cavitation algorithm with enclosed and open cavitation patterns. Impact of the piston ring design parameters such as offset, crown height, and tension on the oil transport, lubrication conditions and friction losses of the compressor were …

Stability Characteristics Of Herringbone Grooved Journal Bearings Incorporating Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki

Jerzy T. Sawicki

Stabilitycharacteristics of the herringbone grooved journal bearings (HGJBs) are analyzedtaking into account cavitation of the fluid flow. The perturbedvalues of pressure and film thickness from a given equilibriumposition are substituted into the Elrod's universal equation, which considersmass conservation in the complete bearing geometry. In order toanalyze the herringbone groove configuration, the governing equations under steadyand perturbed states are transformed to a rectangular domain usingthe grid transformation techniques. It is assumed that under perturbedconditions, the cavitation extent in the bearing remains unchanged andthe pressure gradients are computed in the full film region.The linearized stiffness and damping coefficients are evaluated in thecomplete …

Linear Stability Analysis For A Hydrodynamic Journal Bearing Considering Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki

Jerzy T. Sawicki

The purpose of this paper is to present the two-dimensional linear stability analysis considering the fluid flow in both full film and cavitation regions for a plain cylindrical journal bearing. The Lund's infinitesimal perturbation procedure is applied to Elrod's universal equation for evaluation of unsteady pressure gradients. Based on JFO theory, the pressure distribution, film rupture, and reformation boundaries can be obtained using Elrod's universal equation, for a given operating position of the journal. In this work, it is assumed that for infinitesimal perturbation of a journal about the equilibrium position, the film rupture and film reformation boundaries are the …

Dynamic Coefficient Prediction In Multi-Lobe Journal Bearings Using A Mass Conservation Algorithm, T.V.V.L. Rao, Jerzy Sawicki

Jerzy T. Sawicki

A numerical procedure incorporating cavitation modeling in the predication of dynamic coefficients for four multi-lobe bearings is presented. A first order perturbation solution of the density (or fractional film content) is obtained by using the Elrod universal equation. The Elrod algorithm conserves mass throughout the bearing and automatically predicts the full film and cavitation regions using a switch function. In this work, the cavitation boundary predicted under steady state is considered for calculation of four unsteady pressure gradients. Results of stiffness and damping coefficients are presented for four multi-lobe bearing configurations, viz., two-axial groove, elliptical, three-lobe and offset cylindrical bearing …

Magnetic Bearings For Non-Destructive Health Monitoring Of Rotating Machinery Supported In Conventional Bearings, M. Kasarda, D, Quinn, T. Bash, D. Inman, R. Kirk, Jerzy Sawicki

Jerzy T. Sawicki

This paper describes initial results from a project expanding the field of rotor health monitoring by using Active Magnetic Bearings (AMBs) as actuators for applying a variety of known force inputs to a spinning rotor in order to monitor and evaluate response signals resulting from these inputs on-line. Similar to modal analysis and other nondestructive evaluation (NDE) techniques which apply input signals to static structures in order to monitor responses; this approach allows for the measurement of both input and output response in a rotating system for evaluation. However, unlike these techniques, the new procedure allows for multiple forms of …

Stability Analysis Of Floating Ball Bearing, T.V.V.L. Rao, Jerzy Sawicki

Jerzy T. Sawicki

Conventional disk drive motors supported on ball bearings (BBs) cause nonrepeatable runout (NRRO) due to the surface imperfections on balls and raceways. NRRO is a source of track misregistration between head and disk that inhibits high track density in a hard disk drive. Fluid dynamic bearings with herringbone grooves either on the rotating or stationary surfaces are a suitable replacement for conventional ball bearings. Herringbone grooved bearings have considerably lower noise level than ball bearings and have better stability compared to plain journal bearings at concentric operating position. However, herringbone-grooved patterns are difficult to manufacture because groove depth is of …

Electrohydrodynamic Enhancement Of Heat Transfer And Mass Transport In Gaseous Media, Bulk Dielectric Liquids And Dielectric Thin Liquid Films, Seyed Reza Mahmoudi

Electronic Thesis and Dissertation Repository

Controlling transport phenomena in liquid and gaseous media through electrostatic forces has brought new important scientific and industrial applications. Although numerous EHD applications have been explored and extensively studied so far, the fast-growing technologies, mainly in the semiconductor industry, introduce new challenges and demands. These challenges require enhancement of heat transfer and mass transport in small scales (sometimes in molecular scales) to remove highly concentrated heat fluxes from reduced size devices. Electric field induced flows, or electrohydrodynamics (EHD), have shown promise in both macro and micro-scale devices.

Several existing problems in EHD heat transfer enhancements were investigated in this thesis. …

Acoustic Emission Detection Of Metals And Alloys During Machining Operations, Jameson K. Nelson

Purdue Polytechnic Masters Theses

Nelson, Jameson K. M.S., Purdue University, May 2012. Acoustic Emission Detection of Metals and Alloys During Machining Operations. Major Professor: Rodney G. Handy.

Practical correlation between material deformation attributes and theoretical concepts of machining has proven difficult to attain. The purpose of this study was to further explore trends and relationships using acoustic emission detection of materials undergoing single-point lathe turning machine processes. The majority of machining experiments that incorporate acoustic emissions focuses on tool degradation for the purposes of optimizing consumables required to manufacture mechanical devices. Experiments were implemented varying recording location, mechanical barrier condition, and machine parameters. The …

Wear Behavior Of Tini And Tini-Tic Clads Deposited By Tig Surfacing, Masoud Harooni, Morteza Shamanian, Alireza Fadaei Tehrani

Masoud Harooni

This paper deals with the investigation of wear behavior of TiNi and TiNi-TiC clads applied to plain carbon steel by tungsten inert gas (TIG) surfacing process. In this regard, ball milled Ti-Ni and Ti-Ni-C powder mixtures were used as feedstock materials. The clad layers were investigated using X-ray diffractometery (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness measurements and reciprocating wear tests. The results of microhardness measurements indicated that hardness values of TiNi-TiC composites were higher than those of TiNi by approximately 100HV. It was also shown that the wear behavior of TiNi-TiC clads was better than that …

Experimental Benchmarking Of Surface Textured Lip Seal Models, Wei Li

Theses and Dissertations--Mechanical Engineering

A thorough investigation on the existing hydrodynamic lubrication theories and the reverse pumping theories for the conventional lip seal is conducted. On that basis, the algorithms and the methods used in the numerical modeling of the conventional lip seal are modified and applied to the study of the lip seal running against surface textured shafts. For each step of the study, the numerical model is benchmarked against the experimental results. Important physical mechanisms which explain the reverse pumping ability of the triangular surface structures are revealed. Meanwhile, the accuracy of the numerical model is tested. In general, the numerical simulation …

Investigating Polymer-Tool Steel Interfaces To Predict The Work Of Adhesion For Demoulding Force Optimisation, Kevin Delaney, David Kennedy, Giuliano Bissacco

Conference Papers

Demoulding parts from replication tools is a critical stage of replication processes such as injection moulding and hot embossing. This challenge increases as part size decreases since components and associated replication cores become more fragile and liable to damage. Understanding interfacial characteristics between a polymer and the tool surface is critical to optimise the demoulding of such parts from replication tools. The strength of the polymer-tool interaction is characterised by the adhesion energy and is specific for a particular polymer-tool pair. It’s magnitude depends upon the tool material, the chemical structure of the polymer, the processing conditions and the surface …

Rayleigh Test Apparatus Design Report, Josef Duller, Owen Raybould, James Nicovich

Mechanical Engineering

The Rayleigh Test Apparatus is a device that will be used to test the thermodynamic properties of Nitrous Oxide to assess the feasibility of using this fluid as a coolant for a hybrid rocket aero spike. The aero spike is intended to redirect the propulsion flow as it leaves the engine to create a more efficient flow pattern at low and high altitudes. However, there are issues of overheating which leads to melting of the aero spike. For this reason, the use of nitrous oxide (N2O) as a coolant is being explored. N20 is being considered because it is already …

Manufacturing Self-Assembled Coatings Of Micro- And Nano-Particles By Controlled Evaporation Of Drops And Thin Films, Junfeng Xiao, Rajneesh Bhardwaj, Daniel Attinger

Daniel Attinger

The engineered deposition of self-assembled coatings of micro- and nano-particles on solid surfaces has applications in photonic crystals, optoelectronic devices, sensors, waveguides and antireflective coatings. Besides lithographic, etching or vapor deposition methods, these coatings can be self-assembled on small (

Some Considerations For Regional Airline Operations On Contaminated Runways., Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Patterning Of Alloy Precipitation Through External Pressure, Jack A. Franklin

Publicly Accessible Penn Dissertations

Due to the nature of their microstructure, alloyed components have the benefit of meeting specific design goals across a wide range of electrical, thermal, and mechanical properties. In general by selecting the correct alloy system and applying a proper heat treatment it is possible to create a metallic sample whose properties achieve a unique set of design requirements. This dissertation presents an innovative processing technique intended to control both the location of formation and the growth rates of precipitates within metallic alloys in order to create multiple patterned areas of unique microstructure within a single sample. Specific experimental results for …

Atomic Force Microscopy For Better Probing Surface Properties At Nanoscale: Calibration, Design And Application, Yu Liu

Electronic Thesis and Dissertation Repository

To measure force by AFM with high resolution requires accurate calibration of optic – lever detection sensitivity and spring constant. On biological AFM force mode, the coupling effects of the liquid environment, spot size of laser beam and laser spot location on AFM cantilever backside, must be considered to correlate the static sensitivities from force curves in air and in liquid for calibration. An effective model has been developed first and experimentally elucidated to calibrate the static sensitivity in liquid. The proposed model eliminates inconvenience of static sensitivity calibration in liquid with possible contamination sources.

The static sensitivity based on …

Self-Assembly Of Colloidal Particles From Evaporating Droplets: Role Of Dlvo Interactions And Proposition Of A Phase Diagram, Rajneesh Bhardwaj, Xiaohua Fang, Ponisseril Somasundaran, Daniel Attinger

Daniel Attinger

The shape of deposits obtained from drying drops containing colloidal particles matters for technologies such as inkjet printing, microelectronics, and bioassay manufacturing. In this work, the formation of deposits during the drying of nanoliter drops containing colloidal particles is investigated experimentally with microscopy and profilometry, and theoretically with an in-house finite-element code. The system studied involves aqueous drops containing titania nanoparticles evaporating on a glass substrate. Deposit shapes from spotted drops at different pH values are measured using a laser profilometer. Our results show that the pH of the solution influences the dried deposit pattern, which can be ring-like or …