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Aircraft transmissions for helicopters, turboprops and geared turbofan aircraft require high reliability and provide several thousand hours of operation between overhauls. In addition, They should be lightweight and have very high efficiency to minimize operating costs for the aircraft.
This paper addresses the lubrication of helical gears - especially those factors influencing lubricant film thickness and pressure. Contact between gear teeth is protected by the elastohydrodynamic lubrication (EHL) mechanism that occurs between nonconforming contact when pressure is high enough to cause large increases in lubricant viscosity due to the pressure-viscosity effect, and changes of component shape due to elastic deflection. Acting together, these effects lead to oil films that are stiff enough to separate the contacting surfaces and thus prevent significant metal-to-metal contact occurring in a well-designed gear pair.
The complete Product News section from the July 2018 issue of Gear Technology.
The complete Product News section from the January/February issue of Gear Technology.
What are the pros and cons of using Vickers versus Knoop hardness testers for measuring case depth in carburized gears?
Mineral-oil-base lubricants show a significant decrease of kinematic viscosity with rising temperature, as exemplified in Figure 1 by lubricants for vehicle gears. An important attribute of lubricants is their viscosity index (VI), according to DIN/ISO 2909 (Ref. 4). Viscosity index is a calculated coefficient, which characterizes the change of viscosity of lubricants as a function of temperature. A high viscosity index represents a low variation of viscosity due to temperature and vice versa. A low viscosity-temperature-dependence is required for lubricants that are operated at significantly varying temperature conditions, such as vehicle engine and gear lubricants in summer and winter time. This way, the oils remain flowing and pumpable at low temperatures on the one hand; and on the other hand, sufficiently thick lubricant films can be formed at higher temperatures for a safe separation of the surfaces.
This review of elastohydrodynamic lubrication (EHL) was derived from many excellent sources (Refs. 1â€“5). The review of Blokâ€™s flash temperature theory was derived from his publications (Refs. 6â€“9). An excellent general reference on all aspects of tribology is the Encyclopedia of Tribology (Ref. 10).
News Items About ehl
1 Buehler Celebrates Wilson Hardness 100-Year Anniversary (February 7, 2020)
Buehler, an ITW Company, celebrates the 100-year anniversary of its Wilson hardness brand which was originally known as the Wilson Mechan... Read News
2 Grupo Mess Named Exclusive Buehler Distributor for Metallographic and Hardness Equipment in Mexico (January 20, 2020)
Buehler, an ITW Company announces a partnership with Grupo Mess, a leading Mexico supplier of scientific equipment and services specializ... Read News
3 Buehler Expands Universal Hardness Tester Range (January 31, 2019)
Buehler is excited to announce their latest addition to the Wilson hardness testing range, the new UH4000 Series Universal Hardness Tes... Read News
4 Buehler Offers DiaMet Hardness Software Upgrade for Legacy Hardness Testers (December 21, 2018)
Buehler, an ITW company has announced that the DiaMet hardness software upgrade is now available for legacy Wilson testers. The DiaMet Ha... Read News
5 Buehler Introduces AutoMet Pro Grinder Polishers (November 20, 2018)
Buehler, an ITW company has introduced the AutoMet family, new semi-automatic grinder-polishers that enhance the company’s metallog... Read News
6 Buehler Quick Ship Program Delivers Rockwell Hardness Test Blocks Next Day (January 5, 2018)
Buehler has introduced a Quick Ship program for the popular Wilson certified Rockwell hardness test blocks. For ultimate accuracy an... Read News
7 Hainbuch America Announces Christian Yehle Regional Sales Manager for South Central Region (November 3, 2016)
Hainbuch America has announced that Christian Yehle has rejoined their team as regional sales manager for the South Central Region, cover... Read News
8 David Flynn Joins Diehl Steel (January 7, 2013)
Diehl Steel is pleased to announce the hiring of David Flynn as its new production manager. Flynn will be responsible for managing day-to... Read News
9 Diehl Introduces EDM Blanks (November 27, 2012)
Diehl Steel has introduced Ready-Block EDM Blanks for EDM applications. The ready-to-use blanks are pre-hardened, squared and ground at D... Read News