Search results

As the internal defects (pore defect) of materials formed during the preparation of the composite material have important effects on wear process, the model has been improved to simulate it.

Materials with defects were simulated by an improved cellular automaton model which show changes in three-dimensional topography, temperature of surface and coefficient of friction (COF) during wear process.

It is found that defects increase temperature of material surface. Besides, the materials with little defects have a smaller COF than base materials, as the large block defects make the COF larger than base materials.

Except for effects of defects were simulated in model, how to initialize the surface temperature status that many reports do not take into account can be preferred. And the model is convenient to simulate complex composite materials by setting different properties of cells.

This paper aims to study the tribological behavior of the WS2/oil-impregnated porous polyimide (PPI) solid/liquid composite system, in which both PFPE (perfluoropolyether) and SiCH (silahydrocarbons) oils with different hydrocarbon chains were used, respectively. Lubricating mechanism of the composite system was also explored.

The tribological behaviors of the WS2 films against the PPI cylindrical pins before and after immersing oil were evaluated under different loads by a reciprocating-type ball-on-disc tribometer.

The composite system exhibited the low and stable friction coefficient after the running-in stage, and the lubricant oil played a positive effect. It was found that the WS2/PFPE composite system exhibited more excellent lubricating property, although sole SiCH far exceeds PFPE in lubrication. The abnormal phenomenon mainly resulted from the influence of the oil amount. XRD results on the wear track surfaces indicated that PFPE and SiCH oils with different hydrocarbon chains were likely to preferentially adsorb to the edge plane and basal plane of the WS2 crystals, respectively.

In previous studies, liquid lubricants were directly dripped or spin-coated on the solid lubricant surface. Based on its potential advantage in application, the tribological behavior and mechanism of the solid lubricating film/oil-impregnated PPI composite system were investigated in this study.

In the 40 years of reform and opening-up toward a more rational micro-economic structure, the proportion of output of state-owned enterprises shows a declining trend. Over the past decade, on one hand, the operational efficiency of state-owned enterprises has tended to be low as compared to other ownership enterprises; on the other hand, the asset–liability ratio of state-owned enterprises has risen against the trend, and still remains high under the recent national policy of “deleveraging.” The paper aims to discuss this issue.

This indicates that the inefficiency of state-owned enterprises that once hindered China’s economic development has not yet been fundamentally solved, and the task of deepening state-owned enterprises reform is still arduous.

In the process of establishing China’s modern economic system, there will be some “new state-owned enterprises” growing into world-class ones. This requires more effort in enhancing the capacity for independent innovation, improving the level of organizational control, expanding international market opportunities and fulfilling enterprise social responsibilities with high standards.

It is more appropriate for China to have a micro-economic structure in which public ownership predominates and diverse forms of ownership enjoy common prosperity and development.