scholarly journals Understanding the Mechanism of Load-Carrying Capacity between Parallel Rough Surfaces through a Deterministic Mixed Lubrication Model

Lubricants ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 12
Author(s):  
Yuechang Wang ◽  
Abdullah Azam ◽  
Gaolong Zhang ◽  
Abdel Dorgham ◽  
Ying Liu ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Stribeck Curve ◽  
Future Research ◽  
Load Carrying Capacity ◽  
Proposed Model ◽  
Load Carrying ◽  
Lift Off

Experimental results have confirmed that parallel rough surfaces can be separated by a full fluid film. However, such a lift-off effect is not expected by the traditional Reynolds theory. This paper proposes a deterministic mixed lubrication model to understand the mechanism of the lift-off effect. The proposed model considered the interaction between asperities and the micro-elastohydrodynamic lubrication (micro-EHL) at asperities within parallel rough surfaces for the first time. The proposed model is verified by predicting the measured Stribeck curve taken from literature and experiments conducted in this work. The simulation results highlight that the micro-EHL effect at the asperity scale is critical in building load-carrying capacity between parallel rough surfaces. Finally, the drawbacks of the proposed model are addressed and the directions of future research are pointed out.

Efficient running-in of gears and improved prediction of the tooth flank load carrying capacity

2019 ◽  
Vol 71 (3) ◽  
pp. 366-373
Author(s):  
Martin Zimmer ◽  
Dirk Bartel
Keyword(s):  
Carrying Capacity ◽  
Plastic Material ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Load Carrying Capacity ◽  
Content Type ◽  
Load Carrying ◽  
Life Model ◽  
Extended Life ◽  
Tooth Flank

Purpose The purpose of this paper is to determine parameters for an efficient running-in of gears and an improved method for the prediction of the tooth flank load carrying capacity. Design/methodology/approach In this contribution, a model for the calculation of the pitting life of involute spur gears is introduced, which is based on an extension of the life model according to Ioannides and Harris for rough surfaces. To achieve the most realistic thermal elastohydrodynamic lubrication simulation and stress calculation possible, measured real surfaces and elastic-plastic material properties of the area close to the surface are used. Special attention is paid to the compatibility of the fatigue life calculation for heterogeneous rough surfaces and their consistent consideration in the lifespan calculation. Findings A non-destructive running-in for twin-disc pairings can be performed using suitable operating parameters, which subsequently can be transferred to tooth flank tests. Using the extended life model according to Ioannides and Harris, an enhanced prediction of the tooth flank load carrying capacity is possible. Originality/value The developed extended life model includes a new numerical approach for calculating the tooth flank load carrying capacity. It has the potential to reliably support and hence to accelerate the design process of gears.

scholarly journals Two-scale homogenization of hydrodynamic lubrication in a mechanical seal with isotropic roughness based on the Elrod cavitation algorithm

2021 ◽  
pp. 135065012110176
Author(s):  
Yanxiang Han ◽  
Qingen Meng ◽  
Gregory de Boer
Keyword(s):  
Surface Topography ◽  
Carrying Capacity ◽  
Hydrodynamic Lubrication ◽  
Tribological Performance ◽  
Stribeck Curve ◽  
Polar Coordinate System ◽  
Load Carrying Capacity ◽  
Mechanical Seal ◽  
Macro Scale ◽  
Load Carrying

A two-scale homogenization method for modelling the hydrodynamic lubrication of mechanical seals with isotropic roughness was developed and presented the influence of surface topography coupled into the lubricating domain. A linearization approach was derived to link the effects of surface topography across disparate scales. Solutions were calculated in a polar coordinate system derived based on the Elrod cavitation algorithm and were determined using homogenization of periodic simulations describing the lubrication of a series of surface topographical features. Solutions obtained for the hydrodynamic lubrication regime showed that the two-scale homogenization approach agreed well with lubrication theory in the case without topography. Varying topography amplitude demonstrated that the presence of surface topography improved tribological performance for a mechanical seal in terms of increasing load-carrying capacity and reducing friction coefficient in the radial direction. A Stribeck curve analysis was conducted, which indicated that including surface topography led to an increase in load-carrying capacity and a reduction in friction. A study of macro-scale surface waviness showed that the micro-scale variations observed were smaller in magnitude but cannot be obtained without the two-scale method and cause significant changes in the tribological performance.

Influence of geometric parameters on the bump foil bearing performance

2019 ◽  
Vol 234 (7) ◽  
pp. 1017-1026
Author(s):  
Sadanand Kulkarni ◽  
Soumendu Jana
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
System Development ◽  
Load Capacity ◽  
Radial Clearance ◽  
Load Carrying Capacity ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Load Carrying ◽  
Lift Off

High-speed rotating system development has drawn considerable attention of the researchers, in the recent past. Foil bearings are one of the major contenders for such applications, particularly for high speed and low load rotating systems. In foil bearings, process fluid or air is used as the working medium and no additional lubricant is required. It is known from the published literature that the load capacity of foil bearings depend on the operating speed, viscosity of the medium, clearance, and stiffness of the foil apart from the geometric dimensions of the bearing. In case of foil bearing with given dimensions, clearance governs the magnitude of pressure developed, whereas stiffness dictates the change in radial clearance under the generated pressure. This article deals with the effect of stiffness, clearance, and its interaction on the bump foil bearings load-carrying capacity. For this study, four sets of foil bearings of the same geometry with two levels of stiffness and clearance values are fabricated. Experiments are carried out following two factor-two level factorial design approach under constant load and in each case, the lift-off speed is measured. The experimental output is analyzed using statistical techniques to evaluate the influence of parameters under consideration. The results indicate that clearance has the maximum influence on the lift-off speed/ load-carrying capacity, followed by interaction effect and stiffness. A regression model is developed based on the experimental values and model is validated using error analysis technique.

Analysis of Lap Region between Skirt and Composite Case under Axial Force in Solid Rocket Motor

2011 ◽  
Vol 71-78 ◽  
pp. 4357-4360
Author(s):  
Hong Chao Liu ◽  
Chun Guang Wang ◽  
Yong Qiong Liu ◽  
Bo Yuan
Keyword(s):  
Carrying Capacity ◽  
Element Model ◽  
Optimization Method ◽  
Rocket Motor ◽  
Load Carrying Capacity ◽  
Solid Rocket Motor ◽  
Proposed Model ◽  
Load Carrying ◽  
Solid Rocket ◽  
Main Factor

To study load carrying capacity for Lap Region between the Skirt and Composite Case(LRSC) of the solid rocket motor(SRM),made the stress of layer out of skirt as the research object, established the two-dimensional axisymmetric finite element model for compsite case,analysed the main factor(lap length) for carrying capacity of LRSC,and verified the conclusions by calculation.Optimized the lap length ranged from 40mm to 60mm, proposed model of the optimal lap length and optimization method,calculated optimal lap length under different axial loads.The results show that, with the increase of lap length of skirt, the load bearing capacity of LRSC enhances first and depresses then,exists a great value,which of the corresponding lap length is optimal;With the increase of axial load,optimal lap length monotonously will increase.

scholarly journals Deep learning for bridge load capacity estimation in post-disaster and -conflict zones

2019 ◽  
Vol 6 (12) ◽  
pp. 190227
Author(s):  
Arya Pamuncak ◽  
Weisi Guo ◽  
Ahmed Soliman Khaled ◽  
Irwanda Laory
Keyword(s):  
Deep Learning ◽  
Carrying Capacity ◽  
Load Capacity ◽  
Future Research ◽  
Load Carrying Capacity ◽  
Class Interval ◽  
Conflict Zones ◽  
Post Conflict ◽  
Load Carrying ◽  
Post Disaster

Many post-disaster and post-conflict regions do not have sufficient data on their transportation infrastructure assets, hindering both mobility and reconstruction. In particular, as the number of ageing and deteriorating bridges increases, it is necessary to quantify their load characteristics in order to inform maintenance and asset databases. The load carrying capacity and the design load are considered as the main aspects of any civil structures. Human examination can be costly and slow when expertise is lacking in challenging scenarios. In this paper, we propose to employ deep learning as a method to estimate the load carrying capacity from crowdsourced images. A convolutional neural network architecture is trained on data from over 6000 bridges, which will benefit future research and applications. We observe significant variations in the dataset (e.g. class interval, image completion, image colour) and quantify their impact on the prediction accuracy, precision, recall and F 1 score. Finally, practical optimization is performed by converting multiclass classification into binary classification to achieve a promising field use performance.

Isothermal hydrodynamic pressure and load carrying capacity of parallel rough surfaces based on FFT techniques

2020 ◽  
Vol 44 (4) ◽  
pp. 602-612
Author(s):  
Wan Ma
Keyword(s):  
Carrying Capacity ◽  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Hydrodynamic Pressure ◽  
Radius Of Curvature ◽  
Real Surface ◽  
Load Carrying Capacity ◽  
Time Saving ◽  
Lubricated Contacts ◽  
Load Carrying

In lubricated contacts, the component macrogeometry (radius of curvature) determines the pressure generation, and the surface microgeometry (i.e., roughness) alters it somewhat. However, for parallel surfaces, the microgeometry completely determines the hydrodynamic lubrication. This paper extends earlier work to numerically solve the isothermal hydrodynamic pressure generation and load carrying capacity (LCC) of surfaces with more complicated roughness features. A fast Fourier transform (FFT)-based method is described to quickly obtain the pressure distribution. The method is applicable to both real surface topographies and artificially generated rough surfaces. Results show that it enables one to predict the hydrodynamic pressure, when cavitation is negligible. The relative error of the LCC over the central domain is smaller than 8% and a 500× time saving, compared with the numerical method, is obtained.

Prevention of interfacial slippage in isothermal pure rolling line contact elastohydrodynamic lubrication under heavy loads

2003 ◽  
Vol 217 (4) ◽  
pp. 323-332 ◽  
Author(s):  
Yongbin Zhang
Keyword(s):  
Carrying Capacity ◽  
Elastohydrodynamic Lubrication ◽  
Load Carrying Capacity ◽  
Pure Rolling ◽  
Load Carrying ◽  
Rolling Line ◽  
Line Contacts ◽  
Heavy Loads ◽  
Inlet Zone ◽  
Interfacial Slippage

The contact-lubricant interfacial slippage, near and in the inlet zone, significantly reduces the load-carrying capacity of elastohydrodynamic lubrication (EHL) in isothermal pure rolling line contacts under heavy loads. The EHL load-carrying capacity can be significantly improved by the prevention of this interfacial slippage. Equations are derived for predicting the critical interfacial limiting shear stress, which is the least for preventing this interfacial slippage. These equations can be used for designing the EHL system of which the load-carrying capacity is not reduced by this slippage.

Numerical Study on Load Carrying Mechanism of Two Parallel Lubricated Rough Surfaces With Relative Motion

2007 ◽  
Author(s):  
Hua-Ping Yao ◽  
Ping Huang
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Relative Motion ◽  
Carrying Capacity ◽  
Rough Surfaces ◽  
Peak Height ◽  
Load Carrying Capacity ◽  
Lubrication Film ◽  
Load Carrying ◽  
Minimum Film Thickness

In the present paper, the load carrying mechanism of two parallel lubricated rough surfaces with relative motion is numerically analyzed from the microscopic view. It is found that each asperity of the surface forms mini-type convergent and divergent wedge sliders. The convergent wedge can create positive hydrodynamic pressure and forms a hydrodynamic lubrication film so that pressure is produced to bear an outside load. The Reynolds equation is used to analyze the influence of the roughness on the performances such as the pressure distribution, the load carrying capacity, the shearing force, the friction force and etc. The varying rules of the load carrying capacity and friction coefficient with the peak height of roughness are discussed in detail, and the influence of the minimum film thickness on lubrication state is also analyzed. The results indicate that under a given lubrication film thickness the load carrying capacity can achieve the maximum value and then decrease slowly with the peak height increasing, while the friction coefficient can achieve the minimum value. Furthermore, under the given condition of the peak height and 1 μm⩽h0⩽100 μm of the minimum film thickness the load carrying capacity drops down gradually, while the friction coefficient increases gradually with increase of the minimum film thickness.

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