AGMA-05FTM06-2005.pdf
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1、05FTM06 A Model to Predict Friction Losses of Hypoid Gears by: H. Xu, A. Kahraman, D.R. Houser, The Ohio State University TECHNICAL PAPER American Gear Manufacturers Association Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/111111100
2、1, User=Wing, Bernie Not for Resale, 04/18/2007 11:19:22 MDTNo reproduction or networking permitted without license from IHS -,-,- A Model to Predict Friction Losses of Hypoid Gears Hai Xu, Ahmet Kahraman, Donald R. Houser, The Ohio State University The statements and opinions contained herein are t
3、hose of the author and should not be construed as an official action or opinion of the American Gear Manufacturers Association. Abstract A model to predict friction-related mechanical efficiency losses of hypoid gear pairs is proposed, which combines a commercial available finite element based gear
4、contact analysis model and a friction coefficient model with a mechanical efficiency formulation. The contact analysis model is used to provide contact pressuresandothercontactparametersrequiredbythefrictioncoefficientmodel. Theinstantaneousfriction coefficient is computed by using a validated new f
5、ormula that is developed based on a thermal elastohydrodynamiclubrication(EHL)modelconsideringnon-Newtonianfluid. Computedfrictioncoefficient distributions are then used to calculate the friction forces and the resultant instantaneous mechanical efficiencylossesofthehypoidgearpairatagivenmeshangle.
6、Themodelis appliedtostudytheinfluenceof speed, load, surface roughness, and lubricant temperature as well as assembly errors on the mechanical efficiency of an example face-hobbed hypoid gear pair. Copyright 2005 American Gear Manufacturers Association 500 Montgomery Street, Suite 350 Alexandria, Vi
7、rginia, 22314 October, 2005 ISBN: 1-55589-854-8 Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:19:22 MDTNo reproduction or networking permitted without license from IHS -,-,-
8、 1 A Model to Predict Friction Losses of Hypoid Gears Hai Xu Ahmet Kahraman Donald R. Houser Graduate Research Associate Assoc. Professor Professor Emeritus Department of Mechanical Engineering The Ohio State University 650 Ackerman Road, OH 43202 1 Introduction Gear mesh friction has attracted a nu
9、mber of researchers for more than a century 1. The friction between gear teeth plays an important role in defining the efficiency of the system as well as influencing scoring limits and the dynamical behavior including vibration and noise 2,3. Both sliding and rolling actions at the gear mesh contac
10、t contribute to gear mesh friction. Sliding friction is a direct product of the relative sliding between the two contacting surfaces while rolling friction originates from the resistance to the rolling motion 4. Coefficient of friction that is used widely in the literature usually refers to the coef
11、ficient of sliding friction. A significant number of studies have been published especially within the last forty years on friction and efficiency of gear trains as reviewed by references 5-7. The first group of studies focused on measuring power losses of gear pair directly 8- 17. Several others me
12、asured using twin-disk test machines under conditions simulating a gear pair so that this friction coefficient can be used to predict the efficiency of a gear pair 18-30, 38-39. Some of these studies 18-25 resulted in well-known and widely used empirical formulae for . These empirical formulae indic
13、ate that is a function of a list of parameters such as sliding and rolling velocities, radii of curvature of the surfaces in contact, load or contact pressure, surface roughness, and the lubricant viscosity. A group of efficiency models 31-33 investigated the efficiency of a spur gear pair by assumi
14、ng a uniform along the entire contact surface. A tangential friction force along the sliding direction was computed by using a given constant friction coefficient , and the geometric and kinematic parameters of the spur gears. As a result, the amount of reduction of torque transmitted to the driven
15、gear was used to calculate the mechanical efficiency of the gear pair. These models were useful in bringing a qualitative understanding to the role of spur gear geometry on efficiency. They fell short in terms of the definition of , as a user- defined constant value must be used for every contacting
16、 point on the tooth surface. However, the published experiments on sliding/rolling contacts indicate that many parameters might influence 18-25. In addition, these studies were limited to spur gears and many complicating effects of the tooth bending and contact deformations, tooth profile modificati
17、ons and manufacturing errors were not included. Another group of efficiency models 34-37, 40 relied on published experimental formulae such as those in references 18-21. The models in this group considered spur 35-37, 40 and helical 34 gear pairs and calculated the parameters required to define acco
18、rding to the particular empirical formula adapted. While they are potentially more accurate than the constant models, their accuracy is limited to the accuracy of the empirical formula used. Each empirical formula typically represents a certain type of lubricant, operating temperature, speed and loa
19、d ranges, and surface roughness conditions of roller specimens that might differ from those of the gear pair that is being modeled. The models in the last group are more advanced since they use an EHL model to predict instead of relying on the user or the empirical formulae 42-54. Among them, Dowson
20、 and Higginson 47, and Martin 48 used a smooth surface EHL model to determine the surface shear stress distribution caused by the fluid film, and hence, the instantaneous friction coefficient at the contact. Adkins and Radzimovsky 49 developed a model for lightly loaded spur gears under hydrodynamic
21、 lubrication condition and assumed that the gear tooth is rigid without deflections and local deformations. Simon 50 provided an enhancement by using point contact EHL model for heavily crowned spur gears with smooth surfaces considering the elastic displacement of the surface due to fluid pressure
22、distributions. Larsson 51 and Wang et al 52 analyzed involute spur gear lubrication by using a transient thermal-EHL model with smooth surfaces. Wu and Cheng 53 developed a friction model based on mixed-EHL contacts and applied it to calculate the frictional power losses of Copyright American Gear M
23、anufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:19:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 2 spur gears. The roughness was modeled such that all the asperities hav
24、e the same radius of curvature whose heights have a Gaussian distribution. Mihalidis et al 54 included the influence of the asperity contacts as well in calculating and hence efficiency. These models 47-54 were successful in eliminating to a certain extent the need for prior knowledge of , at the ex
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