An asperity-based fractional coverage model for transfer films on a tribological surface

Wear ◽  
2011 ◽  
Vol 270 (3-4) ◽  
pp. 127-139 ◽  
Author(s):  
E.Y.A. Wornyoh ◽  
C.F. Higgs
Author(s):  
E. Y. A. Wornyoh ◽  
C. F. Higgs

Topography data was obtained from an aluminum thin film deposited unto a substrate. Using this 20 μm × 20 μm specimen, an asperity-based fractional coverage model was used to predict (1) the friction coefficient at a pad/disk interface (2) the thickness of deposited lubricant film and (3) the wear factor for a compacted lubricant pellet in sliding contact. The fractional coverage varies with time and is a useful modeling parameter for quantifying the amount of third body film covering the disk asperities. The model was based on a previous 1-D control volume fractional coverage model which was used to glean tribological parameters including friction coefficient and wear factor. In this model, the wear rate of the pellet, pad friction coefficient, and lubricant thickness can be determined as a function of the pellet load, slider pad load, disk speed, and material properties. Steady-state results from the model adequately predict the self-repairing and self-replenishing nature of powder lubrication as a function of topography.


2004 ◽  
Vol 126 (3) ◽  
pp. 615-619 ◽  
Author(s):  
P. L. Dickrell ◽  
W. G. Sawyer ◽  
A. Erdemir

The frictional behavior of diamond-like carbon (DLC) films varies with environmental condition. One theory asserts that the cause of variations in the frictional performance is environmental contaminants adsorbing onto the DLC film surface. Testing of the frictional performance of DLC films in a pin-on-disk contact has mapped the transient behavior of the friction coefficient. A model for fractional coverage, based on the adsorption of environmental contaminants and their removal through the pin contact, is developed. The rate of adsorption is taken from Langmuir’s model [17], which is combined with the removal ratio from Blanchet and Sawyer [18]. The coefficient of friction is based on the average fractional coverage under the pin contact. The model also gives a closed-form expression for the steady-state fractional coverage. Model calculations compared favorably to the time progression of the friction coefficient for a series of earlier experiments on a superlow friction DLC coating [7], when the fractional removal term was allowed to increase with increasing sliding speed.


Author(s):  
E. Y. A. Wornyoh ◽  
C. F. Higgs

Several pellet-on disk and pad-on disk tribometer tests were conducted to study the lubrication characteristics of third-body particles of MoS2 powder. The tests consisted of simultaneous pellet-on disk and pad-on disk sliding contacts. Results from the tests show the self-repairing, self-replenishing, oil-free lubrication mechanism of MoS2. A theoretical control-volume fractional coverage model was developed to predict (1) the friction coefficient at the pad/disk interface and (2) the wear factor for the lubricated pellet/disk sliding contact. The fractional coverage varies with time and quantifies the amount of third body film covering the disk asperities. Results from the model capture the tribological behavior of the experimental sliding contacts reasonably well.


Wear ◽  
2013 ◽  
Vol 304 (1-2) ◽  
pp. 173-182 ◽  
Author(s):  
Randyka Pudjoprawoto ◽  
Patrick Dougherty ◽  
C. Fred Higgs

Author(s):  
R. Pudjoprawoto ◽  
P. Dougherty ◽  
C. F. Higgs

Pellets were formed by compacting MoS2 powder. In the setup, the pellet is sheared against a disk surface while the slider pad rides on the MoS2 partially-covered asperities, while depleting the lubricant. A volumetric fractional coverage (VFC) modeling approach was developed to predict the friction coefficients for the lubricated pellet/disk sliding contact by assuming that the friction coefficients at pellet/disk and slider/disk interfaces are functions of the fraction of lubricant occupying the control volume. This fractional coverage is a theoretical parameter for quantifying the amount of third body film covering the disk asperities as a function of time. The model can be applied to a deterministic surface, thus, the proposed theory can predict the behavior of friction coefficients between the pellet/disk and slider/disk interfaces for most topographies, whether they are deterministic (i.e., textured) or real (i.e., random).


2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Xinrui Zhang ◽  
Xianqiang Pei ◽  
Qihua Wang ◽  
Tingmei Wang

Carbon fabric/phenolic composites modified with potassium titanate whisker (PTW) were prepared by a dip-coating and hot-press molding technique, and the tribological properties of the resulting composites were investigated systematically using a ring-on-block arrangement under different sliding conditions. Experimental results showed that the optimal PTW significantly decreased the wear-rate. The worn surfaces of the composites and the transfer film formed on the counterpart steel ring were examined by scanning electron microscopy (SEM) to reveal the wear mechanisms. The transfer films formed on the counterpart surfaces made contributions to the improvement of the tribological behavior of the carbon fabric composites. The friction and wear of the filled carbon fabric composites was significantly dependent on the sliding conditions. It is observed that the wear-rate increased with increasing applied load and sliding speeds.


Land ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 344
Author(s):  
Haochen Yu ◽  
Jiu Huang ◽  
Chuning Ji ◽  
Zi’ao Li

A large-scale energy and chemical industry base is an important step in the promotion of the integrated and coordinated development of coal and its downstream coal-based industry. A number of large-scale energy and chemical industrial bases have been built in the Yellow River Basin that rely on its rich coal resources. However, the ecological environment is fragile in this region. Once the eco-environment is destroyed, the wildlife would lose its habitat. Therefore, this area has attracted wide attention regarding the development of the coal-based industry while also protecting the ecological environment. An ecological network could improve landscape connectivity and provide ideas for ecological restoration. This study took the Ningdong Energy and Chemical Industrial Base as a case study. Morphological spatial pattern analysis was applied to extract core patches. The connectivity of the core patches was evaluated, and then the ecological source patches were recognized. The minimum cumulative resistance model, hydrologic analysis and circuit theory were used to simulate the ecological network. Then, ecological corridors and ecological nodes were classified. The results were as follows: (1) The vegetation fractional coverage has recently been significantly improved. The area of core patches was 22,433.30 ha. In addition, 18 patches were extracted as source patches, with a total area of 9455.88 ha; (2) Fifty-eight potential ecological corridors were simulated. In addition, it was difficult to form a natural ecological corridor because of the area’s great resistance. Moreover, the connectivity was poor between the east and west; (3) A total of 52 potential ecological nodes were simulated and classified. The high-importance nodes were concentrated in the western grassland and Gobi Desert. This analysis indicated that restoration would be conducive to the ecological landscape in this area. Furthermore, five nodes with high importance but low vegetation fractional coverage should be given priority in later construction. In summary, optimizing the ecological network to achieve ecological restoration was suggested in the study area. The severe eco-environmental challenges urgently need more appropriate policy guidance in the large energy and chemical bases. Thus, the ecological restoration and ecological network construction should be combined, the effectiveness of ecological restoration could be effectively achieved, and the cost could also be reduced.


2018 ◽  
Vol 35 (12) ◽  
pp. 1273-1285 ◽  
Author(s):  
William H. Pennock ◽  
Monroe L. Weber-Shirk ◽  
Leonard W. Lion

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