Analysis of EHL Circular Contact Start Up: Comparison With Experimental Results

2005 ◽  
Author(s):  
Jiaxin Zhao
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Contact Geometry ◽  
Experimental Results ◽  
Contact Interface ◽  
Solid Contact ◽  
Start Up ◽  
Lubrication Performance ◽  
Lubricated Contact ◽  
Thickness Variations ◽  
Good Agreement

In this paper, the start up condition in elastohydrodynamic lubrication was studied on a steel ball on glass disc contact lubricated with a mineral oil, using a previously developed mixed phase lubrication contact model. The numerical simulation demonstrated the contact geometry change in the transition from initial solid contact to final fully lubricated contact, as well as the load sharing variation between lubricated and solid contacts during the start up. The numerical results of contact geometry was then compared with an experimental study of the same start up situation published by Glovnea and Spikes [1]. The film thickness variations and the propagation of the solid-lubricated contact interface during the start up were compared. Furthermore, an analytical result of the propagation of the solid-lubricated contact interface was also generated by assuming the dominance of the wedge and squeeze terms in the Reynolds Equation, and was also compared with the numerical and experimental results. Good agreement exists among the analytical, numerical and experimental results. The good agreement proves the numerical model as a valid tool in studying the start up condition in elastohydrodynamic lubrication as the transition from solid contact to lubricated contact is of great importance when investigating the start up process and its effects on the overall lubrication performance.

Analysis of EHL Circular Contact Start Up: Part I—Mixed Contact Model With Pressure and Film Thickness Results

2000 ◽  
Vol 123 (1) ◽  
pp. 67-74 ◽  
Author(s):  
Jiaxin Zhao ◽  
Farshid Sadeghi ◽  
Michael H. Hoeprich
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Contact Problems ◽  
Iteration Scheme ◽  
Mixed Lubrication ◽  
Contact Forces ◽  
Solid Contact ◽  
Start Up ◽  
Lubricated Contact

In this paper a model is presented to investigate the start up condition in elastohydrodynamic lubrication. During start up the lubrication condition falls into the mixed lubrication regime. The transition from solid contact to lubricated contact is of importance when investigating the start up process and its effects on bearing performance. The model presented uses the multigrid multilevel method to solve the lubricated region of the contact and a minimization of complementary energy approach to solve the solid contact region. The FFT method is incorporated to speed up the film thickness calculation. An iteration scheme between the lubrication and the solid contact problems is used to achieve the solution of the mixed lubrication contact problem. The results of start up with smooth surfaces are provided for the case when speed increases from zero to desired speed in one step and the case when speed is linearly increased to desired speed. The details of the transition from full solid contact to full lubricated contact in EHL start up are presented. The change of pressure and film thickness as well as contact forces and contact areas are discussed.

Thermal insulation effect on EHL of coated cam/tappet contact during start up

2018 ◽  
Vol 70 (6) ◽  
pp. 917-926 ◽  
Author(s):  
Xianghui Meng ◽  
Changya Yu ◽  
Youbai Xie ◽  
Benfu Mei
Keyword(s):  
Thermal Insulation ◽  
Power Loss ◽  
Elastohydrodynamic Lubrication ◽  
Cold Start ◽  
Content Type ◽  
Friction Power ◽  
Warm Start ◽  
Start Up ◽  
Lubrication Performance ◽  
Insulation Effect

Purpose This paper aims to investigate the lubrication performance of cam/tappet contact during start up. Especially, the thermal insulation effects of coating on the lubrication performance during cold start up process and warm start up process are studied. Design/methodology/approach A numerical model for the analysis of thermal elastohydrodynamic lubrication of coated cam/tappet contact is presented. In this model, the Reynolds equation and the energy equations are discretized by the finite difference method and solved jointly. Findings During start up, the contact force at cam nose-to-tappet contact decreases with increasing time, while the absolute entrainment velocity has the upward trend. The minimum film thickness, maximum average temperature and friction power loss increase with increasing time, while the coefficient of friction decreases during start up. Because of the thermal insulation effect, the coating can significantly increase the degree of temperature rise. Compared with the uncoated case, the coated cam/tappet results in a lower friction power loss. Generally, the friction power loss in the cold start up process is much higher than that in the warm start up process. Originality/value By this study, the lubrication performance and the kinematics and the dynamics of the cam/tappet during start up process are investigated. Meanwhile, the thermal insulation effect of coating is also illustrated. The difference of lubrication performance between cold start up process and warm start up process is analyzed. The results and thermal elastohydrodynamic lubrication method presented in this study can be a guidance in the design of the coated cam/tappet.

Elastohydrodynamic Lubrication Analysis of Point Contacts With Consideration of Material Inhomogeneity

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Zhang Shengguang ◽  
Wang Wenzhong ◽  
Zhao Ziqiang
Keyword(s):  
Film Thickness ◽  
Numerical Algorithms ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Bearing ◽  
Inclusion Problem ◽  
Material Inhomogeneity ◽  
Equivalent Inclusion Method ◽  
Lubrication Performance ◽  
The Matrix ◽  
Lubricated Contact

Inhomogeneities in matrix may significantly affect the performance of mechanical elements, such as possible fatigue life reduction for rolling bearing due to stress concentration induced by inhomogeneities; on the other hand, most components operate under lubrication environment. So far the numerical algorithms to solve lubrication problems without the consideration of inhomogeneities or inclusions are well developed. In this paper, the combination of elastohydrodynamic lubrication (EHL) and inclusion problem is realized to consider the effect of material inhomogeneity on the lubrication performance and subsurface stress distribution, etc. The matrix inhomogeneity will induce disturbed displacement, which will modify the film thickness and consequently result in the change of lubricated contact pressure distribution, etc. The matrix inhomogeneity is treated as the homogeneous inclusion with equivalent eigenstrain according to equivalent inclusion method (EIM), and the disturbed displacement is calculated by semi-analytical method (SAM). While the pressure and film thickness distributions are obtained by solving Reynolds equation. The iterative process is realized to consider the interaction between lubrication behavior and material response. The results show the inhomogeneity in contacting body will greatly influence the lubricated contact performance. The influences are different between compliant and stiff inhomogeneity. It is also found that different sizes and positions of inhomogeneity can significantly affect the contact characteristic parameters.

Formation of Steady Dimples in Point TEHL Contacts

2000 ◽  
Vol 123 (1) ◽  
pp. 42-49 ◽  
Author(s):  
P. Yang ◽  
S. Qu ◽  
M. Kaneta ◽  
H. Nishikawa
Keyword(s):  
Complete Solution ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Major Radius ◽  
Theoretical Results ◽  
Good Agreement ◽  
Contact Ellipse

Experimental results of steady dimples measured in elliptical glass-steel contact under pure sliding conditions are presented. It is found that two dimples connected with a shallower furrow are generated, each near an end of the major radius of the contact ellipse. The complete solution of the corresponding thermal elastohydrodynamic lubrication (TEHL) problem is calculated numerically. Good agreement is obtained between the experimental and theoretical results. This agreement can be explained by the temperature-viscosity wedge mechanism. Correctness of this mechanism is demonstrated using additional experiments with ceramic balls in contact with glass and sapphire disks.

Modelling Tribological Performance of Bodymaker Lubricants

2008 ◽  
Vol 3 (1) ◽  
Author(s):  
Javier Lara-Romero ◽  
Rafael Maya-Yescas ◽  
Fernando Chiñas-Castillo
Keyword(s):  
Mathematical Model ◽  
Tribological Performance ◽  
Experimental Results ◽  
Contact Interface ◽  
Mechanical Contact ◽  
Test Protocol ◽  
Wear Rates ◽  
Oil In Water ◽  
Good Agreement ◽  
Algebraic Modelling

Bodymaker lubricants are oil-in-water emulsions used as coolants in the ironing process during production of aluminium cans. Lubricants are formulated to diminish friction during ironing and to cool down the mechanical contact interface. In the present work, a methodology based on algebraic modelling of the process is proposed to select among bodymaker lubricants, featuring their tribological performance. Experimental results are obtained by "pin-and-vee" test protocol, mathematical model exhibits good agreement with experimental observations. In general, tests carried out indicate that different bodymaker lubricants exhibit different wear rates, therefore evaluation of this rate can be used as tool to discriminate among lubricants performance. At present, this approach is being successfully used by a lubricant making company to evaluate and compare the performance of commercial bodymaker lubricants.

Influence of a Surface Bump or Groove on the Lubricating Performance and Dimple Phenomena in Simple Sliding Point EHL Contacts

2004 ◽  
Vol 126 (3) ◽  
pp. 466-472 ◽  
Author(s):  
Peiran Yang ◽  
Jinlei Cui ◽  
Motohiro Kaneta ◽  
Hiroshi Nishikawa
Keyword(s):  
Numerical Solution ◽  
Significant Influence ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Optical Interferometry ◽  
Steel Ball ◽  
Experimental Results ◽  
Oriented Surface ◽  
Glass Disk ◽  
Good Agreement

The influence of a transversely or longitudinally oriented surface bump or groove on the lubricating performance and dimple phenomena in the simple sliding point contact composed of a steel ball and a glass disk has been investigated theoretically with numerical solution of the thermal elastohydrodynamic lubrication (EHL) and experimentally with optical interferometry technique. Good agreement has been obtained between the theoretical and experimental results. It has also been discovered that the surface bump or groove is dangerously harmful to the lubricating performance and has a significant influence on the dimple phenomena.

Elastohydrodynamic Lubrication of a Spinning Ball in a Nonconforming Groove

1970 ◽  
Vol 92 (1) ◽  
pp. 89-94 ◽  
Author(s):  
C. W. Allen ◽  
D. P. Townsend ◽  
E. V. Zaretsky
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Theoretical Predictions ◽  
Ball Spinning ◽  
Spinning Speed ◽  
Paraffinic Oil ◽  
Good Agreement

An elastohydrodynamic solution for the spinning torque of a ball spinning without rolling in a non-conforming groove is presented. The solution is compared with experimental results using a synthetic paraffinic oil as the lubricant. A modified pressure-viscosity relation is proposed. The theory predicts increase in torque with stress and spinning speed and decreasing conformity. Good agreement was obtained between theoretical predictions and experimental results.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

Plasto ‐elastohydrodynamic lubrication performance of greased ellipsoid contact

2021 ◽  
Author(s):  
Yong Zheng ◽  
Changqing Wang ◽  
Chao Pu ◽  
Jiayu Gong ◽  
Fanming Meng
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Lubrication Performance
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