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Lubrication systems used in gear trains are intended to serve two distinct purposes: (i) provide the quantities of oil to gear mesh contact interfaces to allow formation of a healthy elastohydrodynamic fluid film and (ii) help remove heat generated at gear mesh contact interfaces. Failure of the lubrication system in either of these tasks often results in a temperature induced contact failure, called scuffing. This study investigates the effectiveness of various lubrication methods in preventing scuffing. A new high-speed gear test set-up is developed specifically for investigating the scuffing performance of high-speed, high-load helical gears operating at realistic oil temperature conditions. The objective of this study is to experimentally characterize the scuffing performance of the helical gears as a function of various lubrication methods and parameters defining each method. Sets of scuffing experiments are performed using the test methodology developed and lubrication methods that successfully prevented scuffing of the gears are identified. The test matrix includes two different automotive drivetrain lubricants and different lubrication methods of forced (jet) lubrication, dip lubrication and mist lubrication. The test specimens consist of gears having three surface finishes, (i) ground-honed gears which were identified as the baseline, (ii) super-finished gears and (iii) phosphate coated gears. The effects of parameters such as jet flow rate, jet velocity and impingement depth on scuffing are investigated and tabulated using the results from the jet lubricated tests. The impact of gear micro-geometry and edge-loading effects on scuffing initiation are also investigated.
The mechanism of surface damage known as scuffing has been a research topic of great interest for many years. However, the question of how scuffing is initiated and the factors that contribute to its occurrence are still poorly understood. Thermal analysis for scuffing will be very helpful to understand the mechanism of scuffing and explain some phenomena in scuffing. A two-dimensional rotational model and three-dimensional reciprocation model have been built to investigage the temperature distribution in scuffing phenomena. The numerical models are combined with a contact mechanics model to calculate the temperature distribution on the contact area during scuffing. The results showed that the local temperature before scuffing was high enough to change lubricant properties which will directly affect the scuffing process. However the temperature distribution was smooth even though the pressure distribution had many sharp peaks. The local temperature dropped to the ambient temperature very quickly when a contact area moved out of contact. However once scuffing occurred, the friction coefficient jumped to a high value generating more heat, the flash temperature could reach to 800° C which was high enough to change speciment's material properties. The three-dimensional reciprocation model had been utilized to investigate the domain and time effect on the validity of Jaeger and Carslaw theory. It was found that for a short time (Fourier number smaller than 1), Jaeger and Carslaw theory was valid for small calculation domain (L/l=4, H/l=2). However with increasing calculation time, a larger domain size was needed to ensure the accuracy of Jaeger and Carslaw theory. In order to investigage the scuffing mechanism, scuffing tests were conducted by using a high frequency testing rig. Low carbon steel specimens had the highest scuffing resistance as compared to medium and high carbon steel speciments. The martensite and tempered martensite stell had lower scuffing resistance but the wear resistance was much higher than the original material. For the martensite and tempered martensite, the scuffing resistance was very similar for each type of steel. After investigating the sub-surface of all speciments, plastic deformation was observed on all the testing speciments after scuffing. Hence plastic deformation is the main scuffing mechanism for the low, medium and high carbon steels.
Specifically focusing on fluid film, hydrodynamic, and elastohydrodynamic lubrication, this edition studies the most important principles of fluid film lubrication for the correct design of bearings, gears, and rolling operations, and for the prevention of friction and wear in engineering designs. It explains various theories, procedures, and equations for improved solutions to machining challenges. Providing more than 1120 display equations and an introductory section in each chapter, Fundamentals of Fluid Film Lubrication, Second Edition facilitates the analysis of any machine element that uses fluid film lubrication and strengthens understanding of critical design concepts.
This resource covers all areas of interest for the practicing engineer as well as for the student at various levels and educational institutions. It features the work of authors from all over the world who have contributed their expertise and support the globally working engineer in finding a solution for today‘s mechanical engineering problems. Each subject is discussed in detail and supported by numerous figures and tables.
The technology involved in lubrication by nanoparticles is a rapidly developing scientific area and one that has been watched with interest for the past ten years. Nanolubrication offers a solution to many problems associated with traditional lubricants that contain sulphur and phosphorus; and though for some time the production of nanoparticles was restricted by the technologies available, today synthesis methods have been improved to such a level that it is possible to produce large quantities relatively cheaply and efficiently. Nanolubricants develops a new concept of lubrication, based on these nanoparticles, and along with the authors’ own research it synthesises the information available on the topic of nanolubrication from existing literature and presents it in a concise form. Describes the many advantages and potential applications of nanotechnology in the tribological field. Offers a full review of the state-of-the-art as well as much original research that is yet unpublished. Includes sections on boundary lubrication by colloïdal systems, nanolubricants made of metal dichalcogenides, carbon-based nanolubricants, overbased detergent salts, nanolubricants made of metals and boron-based solid nanolubricants and lubrication additives. Authored by highly regarded experts in the field with contributions from leading international academics. Nanolubricants will appeal to postgraduate students, academics and researchers in mechanical engineering, chemical engineering and materials science. It should also be of interest to practising engineers with petroleum companies and mechanical manufacturers.
Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented. Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussion on equations relevant to lubrication, including the Reynolds equation. The reader is then introduced to lubrication of rigid cylinders; the importance of film thickness in highly loaded rigid contacts; the elasticity of solids in contact; and the theory of elasto-hydrodynamic lubrication. Subsequent chapters focus on apparatus and measurements of film thickness and film shape; friction and viscosity; and lubrication of gears and roller bearings. This book will be of interest to tribologists.
This book highlights some of the most important structural, chemical, mechanical and tribological characteristics of DLC films. It is particularly dedicated to the fundamental tribological issues that impact the performance and durability of these coatings. The book provides reliable and up-to-date information on available industrial DLC coatings and includes clear definitions and descriptions of various DLC films and their properties.