Zhou Xincong

Tribological Performance of a Polymer Blend of NBR Used for Stern Bearings

Nitrile-butadiene rubber (NBR) and another polymer with an excellent self-lubricating property are blended to develop a new kind of polymer used for water-lubricated stern bearings. The tribological performance of the new Polymer Blend of NBR (PBN), with the comparison of a rubber common used for most stern bearings, was studied using a stern bearing test rig of SSB-100. The results showed that the friction coefficients of PBN are lower than those of NBR under water-lubricated conditions. And the difference is the most evident at speeds of 0.1 ~ 2.0m/s. So PBN will change to Plasto-Elastohydrodynamic (PEH) Lubrication at lower speed to reduce the critical speed of bearing squeal. This indicates blending rubber with other polymers is an effective means to develop low-friction stern bearing materials. Furthermore, test results revealed that reducing the rubber layer thickness and hardness will reduce the friction coefficients. So in the structure design of water-lubricated rubber bearings, selecting proper structural parameter will improve the tribological performance.

Environmental Impact Assessment of Artificial Aggregate Systems Based on Fuzzy Comprehensive Evaluation

Aggregates are food for construction industry and hydraulic and hydropower engineering, account for 80% of concrete. Now the number of artificial aggregate systems of being used and preparing to put into use is considerable, which calls for an efficient method to assess the environment impact. In this paper eight factors are taken into consideration to set up a factor set, which includes wastewater, noise, dust, construction worker’s health, soil and water conservation, solid waste, rare animal and plant, the natural landscape and heritage. The option set (reviews set) includes four elements: slight impact, minor impact, greater impact and serious impact. The weight coefficient set is established based on the Delphi Method. After all the membership degrees of a single factor to the option set are determined, a remark vector is obtained. The remark vector of all factors composes the evaluation matrix. After a calculation with the matrix, we get the fuzzy comprehensive evaluation vector and the environmental impact assessment is conducted. An example of fuzzy comprehensive evaluation of environmental impact on an artificial aggregate system by the Dadu River shows that the method is practical and feasible.