scholarly journals Effect of Relative Velocity Between Rough Surfaces: Hydrodynamic Lubrication of Rotary Lip Seal

2017 ◽  
Vol 22 (2) ◽  
pp. 321-332 ◽  
Author(s):  
I. Lahjouji ◽  
M. El Gadari ◽  
B. El Fahime ◽  
M. Radouani

Abstract Since the sixties, most of numerical studies that model the rotary lip seal lubrication have been restricted by assuming that one of the two opposing surfaces is smooth: either the lip or the shaft. This hypothesis, although it is verified only for a shaft roughness ten times smaller than that of the seal, is the best solution to avoid the transient term “∂h/∂t” in the deterministic approach. Thus, the subject of the present study is twofold. The first part validates the current hydrodynamic model with the international literature by assuming the asperities on the lip and shaft as a two-dimensional cosine function. In the second part the Reynolds equation for rough surfaces with relative motion is solved. The numerical results show that the relative motion between rough surfaces impacts significantly the load support and the leakage rate, but affects slightly the friction torque.

Lubricants ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 16
Author(s):  
Imane Lahjouji ◽  
M’hammed El Gadari ◽  
Mohammed Radouani

It is generally agreed that radial lip seals are used in systems with a rotating shaft and a stationary lip. However, according to previous work, it was demonstrated that relative motion between the shaft and the lip has substantial effects on the hydrodynamic lifting load and sealing performances. Nowadays, new generations of textured shafts have emerged in order to reduce friction torque and improve reverse pumping, but no study has confirmed the effect of the relative motion between the rough lip and the shaft grooves on the rotary lip seal performances. In this work, an isothermal hydrodynamic lubrication was performed in transient conditions to investigate the effect of the relative velocity between an oblique grooved shaft and a rough lip. After confirming the validity of the current model with respect to previous works, simulations have underlined the effect of the grooved shaft with relative lip motion on the rotary lip seal performance. Indeed, by keeping the same relative velocity between surfaces, it is shown that moving the shaft with a rate higher than that of the lip surface could produce an important reverse pumping and reduce the friction torque significantly, in comparison with cases where the shaft velocity is weaker.


Using the two-space homogenization method we derive an averaged Reynolds equation that is correct to O (< H 6 > — < H 3 > 2 ), where H is the total film thickness and the angle brackets denote a spatial average. Applications of this mean Reynolds equation to a squeeze-film bearing with a sinusoidal or an isotropic surface roughness are discussed.


1978 ◽  
Vol 100 (1) ◽  
pp. 12-17 ◽  
Author(s):  
Nadir Patir ◽  
H. S. Cheng

A new approach is utilized to determine the effects of surface roughness on partially lubricated contacts. An average Reynolds equation for rough surfaces is defined in terms of pressure and shear flow factors, which are obtained by numerical flow simulation. Through the use of measured or numerically generated rough surfaces, any three dimensional roughness structure can be analyzed with this method. The average Reynolds equation is obtained for isotropic surfaces, and for surfaces with directional patterns. The flow factors for these surfaces are expressed as empirical relations in terms of h/σ and a surface characteristic γ defined as the ratio of x and y correlation lengths.


Perception ◽  
10.1068/p2983 ◽  
2000 ◽  
Vol 29 (6) ◽  
pp. 721-727 ◽  
Author(s):  
George Mather

A texture pattern devised by the Japanese artist H Ouchi has attracted wide attention because of the striking appearance of relative motion it evokes. The illusion has been the subject of several recent empirical studies. A new account is presented, along with a simple experimental test, that attributes the illusion to a bias in the way that local motion signals generated at different locations on each element are combined to code element motion. The account is generalised to two spatial illusions, the Judd illusion and the Zöllner illusion (previously considered unrelated to the Ouchi illusion). The notion of integration bias is consistent with recent Bayesian approaches to visual coding, according to which the weight attached to each signal reflects its reliability and likelihood.


2021 ◽  
Vol 11 (23) ◽  
pp. 11299
Author(s):  
Liangjie Zheng ◽  
Biao Ma ◽  
Man Chen ◽  
Liang Yu ◽  
Qian Wang

Clutch disengaging dynamic characteristics, including the disengaging duration and the variations of friction pair gaps and friction torque, are crucial to the shifting control of an automatic transmission. In the present paper, the influence of lubrication oil (ATF) temperature on disengaging dynamic characteristics is investigated through a comprehensive numerical model for the clutch disengaging process, which considers the hydrodynamic lubrication, the asperity contact, the heat transfer, the spline resistance, and the impact between the piston and clutch hub. Moreover, the non-uniformity coefficient (NUC) is proposed to characterize the disengaging uniformity of friction pairs. As the ATF temperature increases from 60 °C to 140 °C, the clutch disengaging duration shortens remarkably (shortened by 55.1%); besides, the NUC sees a decreasing trend before a slight increase. When the ATF temperature is 80 °C, the distribution of friction pair gaps is most uniform. During the disengaging process, the increase of ATF temperature not only accelerates the change of the lubrication status between friction pairs but also contributes to the decrease of contact torque and hydrodynamic torque. This research demonstrates for the first time, evidence for clutch disengaging dynamic characteristics with the consideration of ATF temperature.


The hydrodynamic lubrication of rough surfaces is analysed with the Reynolds equation, whose application requires the roughness spacing to be large, and the roughness height to be small, compared with the thick­ness of the fluid film. The general two-dimensional surface roughness is considered, and results applicable to any roughness structure are obtained. It is revealed analytically that two types of term contribute to roughness effects: one depends on the shape of the autocorrelation function and the other does not. The former contribution was neglected by previous workers. The numerical computation of an example shows that these two contributions are comparable in magnitude.


2004 ◽  
Vol 126 (1) ◽  
pp. 156-161 ◽  
Author(s):  
Richard F. Salant ◽  
Ann H. Rocke

The flow field in the lubricating film of a rotary lip seal is analyzed numerically by solving the Reynolds equation with flow factors. The behavior of such a flow field is dominated by the asperities on the lip surface. Since previous analyses treated those asperities deterministically, they required very large computation times. The present approach is much less computationally intensive because the asperities are treated statistically. Since cavitation and asperity orientation play important roles, these are taken into account in the computation of the flow factors. Results of the analysis show how the operating parameters of the seal and the characteristics of the asperities affect such seal characteristics as the pressure distribution in the film, the pumping rate and the load support.


2021 ◽  
Vol 13 (3-1) ◽  
pp. 11-34
Author(s):  
Svetlana Neretina ◽  

The purpose of this paper is to show how the thought and speech of people holding and defending directly opposite positions affect the change in the thought and speech of people of their own and subsequent generations, with different life orientations, and to find ways of this influence. The author describes the situation that arose at the end of the sixties of the twentieth century, known as the ideological dispersal of philosophical, historical and sociological trends that ran counter to the policy of the CPSU, which became especially fierce in the fight against opponents after the USSR’s invasion of Czechoslovakia in August, 1968. One of the results of such an ideological battle was the defeat of the sector of the methodology of history of the Institute of General History of the USSR Academy of Sciences, headed by M. Ya. Gefter, who published a series of books in which the so-called laws of historical development (formational approach) were questioned and the fundamental provisions of the classics of Marxism-Leninism were criticized. The subject of analysis is Gefter’s article “A Page from the History of Marxism in the Early 20th Century”, published in the book “Historical Science and Some Problems of the Modernity”, dedicated to the analysis of Lenin’s tactics and strategy development which changed the views of many, especially young, historians on the historical process, and most importantly - on the methods of seeking and expressing the truth. The differences were expressed primarily in the fact that the proponents and defenders of the Soviet regime, which was based on their own established norms of Marxism-Leninism, fearlessly used all means of pressure on unwanted opponents. Professionals, however, who tried to understand the true sense of the historical process, the sense of judgments about it, especially the sense of the revolutionary struggle against the autocracy, unfolding at the beginning of the twentieth century, were forced to use the Aesopian language, which also provoked a distortion of this sense in many ways: due to the nebulous and veiled expressions, which give the impression of theoretical blackmail, causing such consequences as speech irresponsibility.


2018 ◽  
Vol 4 (1) ◽  
Author(s):  
Cosetta Saba

This essay collects the first results of a reflection launched in the context of the Conference "The Arts of the 1900s and Carmelo Bene" curated by Edoardo Fadini and based in Turin, at the Gallery of Modern Art, between 24 and 26 October 2002. The intent is to focus on how in the first phase of the interdisciplinary practice of Carmelo Bene, between the Sixties and the Seventies, an aesthetic reflection and a deconstructive attitude emerge that involve questions (such as the subject, subjectivity and singular / plural dimension of art) that were being defined in the philosophical field and in the extended field of art during the second half of the twentieth century.


Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 539
Author(s):  
Nebojsa Nikolic ◽  
Zivota Antonic ◽  
Jovan Doric ◽  
Dragan Ruzic ◽  
Stjepan Galambos ◽  
...  

The aim of this paper is to derive an equation for the temperature distribution in journal bearing oil film, in order to predict the thermal load of a bearing. This is very important for the prevention of critical regimes in a bearing operation. To achieve the goal, a partial differential equation of the temperature field was first derived, starting from the energy equation coupled with the Reynolds equation of hydrodynamic lubrication for a short bearing of symmetric geometry. Then, by solving the equation analytically, the function of temperature distribution in the bearing oil film has been obtained. The solution is applied to the journal bearing, for which the experimental data are available in the references. Finally, the obtained results have been compared to the corresponding experimental values for two operating regimes, and a good level of agreement was achieved.


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