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In this work, a series of experimental tests is carried out in laboratory conditions which set the rubber compound (soft and stiff), the normal load, and the direction of propagation of sea water droplets into the interface of rubber–steel pipe contact as variables. The results show that the maximum static frictions (F) of rubber–pipe contacts increase as the normal load increases in both dry and lubricating conditions, and the values of F for the softer rubber are higher than that for the stiffer rubber. However, significant reduction in static friction is found due to the lubrication of sea water droplets. The influence of lubrication is stronger when the droplets propagate into the contact interfaces at the tail edge than that at the front edge. Capture sequences of the contact region facilitate the lubrication of seawater droplets by accelerating the progress of separation in the contact interfaces, thus reducing the static friction force. This investigation improves our understanding of the lubrication of sea water droplets during pipe-laying operation, and it will help us to conduct further research on the accuracy and safety of offshore engineering.

To improve friction and wear performance and service life of the disc-brake pair material of a drilling rig, a new type of asbestos-free frictional material with better performance for disc-brake blocks is developed, and its wear mechanism is investigated by friction and wear experiments. Topography and elementary components of the brake block’s wear surface are analyzed by employing SEM and EDAX patterns, revealing its tribological behaviour and wear mechanism. When the frictional temperature is lower, the surface film of the brake block is thinner, dense, smooth with plasticity, and divided into the mixture area, Feabundant area, carbon-abundant area and spalling area. The mixture area consists of various constituents of frictional pairs without ploughing and rolling trace. The Fe-abundant area mainly consists of iron and other constituents. The carbon-abundant area is the zone where graphite and organic fibre are comparatively gathered, while the spalling area is the zone where the surface film is spalled and its surface is rough and uneven, with a loose and denuded state. During the period of high frictional temperature, the frictional surface is also divided into the mixture area, Feabundant area and spalling area. In this case, the mixture area consists of abrasive dust from friction pairs, and the surface film is distributed with crumby hard granules, exiguous oxide, carbide granules and sheared slender fibre. The Fe-abundant area is mostly an oxide layer of iron with a flaky distribution. Fracture and spalling traces as well as an overlapping structure of multilayer surface films can be easily found on the surface film. The components of the spalling area are basically the same as that of the matrix. At the beginning of wear, the hard peaks from the friction surface of the disc-brake plough on the surface of the brake block. With increasing frictional temperature, the friction surface begins to soften and expand, and oxidized wear occurs at the same time. During the high-temperature wear period, severely influenced by friction heat, obvious softening and plastic flow can be found on the friction surface of the brake block, its anti-shearing ability is weakened, and adhesive wear is intensified. Thermal decomposition of cohesive material in the brake block is simultaneously strengthened, so that constituents shed due to loss of adhesion. Organic fibre is in a flowing state and obviously generates drawing, shearing, carbonization and oxidization. In addition, thermal cracking, thermal oxidization, carbonization and cyclization of organic substances on the surface of brake block can make the friction surface produce pores or cracks, thus fatigue wear occurs.

Experiments on molecular deposition (MD) films with and without alkyl terminal groups deposited on silicon wafers were conducted using nano-indentation. It was found that MD films and alkyl-terminated MD films exhibit a higher critical load and a lower coefficient of friction than the silicon substrate. The critical load increases with the number of layers, and the coefficients of friction of MD films with alkyl terminal groups are lower than those of the corresponding MD films with the same number of layers but without alkyl terminal groups.

Mechanisms of abrasive erosion for polymers, including polyurethane, styrene-butadiene rubber, nylon-6 and polytetrafluoroethylene, have been investigated using a special abrasive erosion test machine designed by the authors. Based upon some observations of the abraded surfaces of test samples using scanning electron microscopy (SEM), the mechanisms of abrasive erosion for the polymers examined could be summarized as follows: a microcutting action of the abrasives with a certain kinetic energy; microdelamination of the surface layer of the materials resulting from initiation and propagation of microcracks; mechanochemical and thermal decomposition of materials; and surface peeling, resulting from plastic fracture expanded from local plastic deformation of the material. The influence of these factors on the wear rate of the abrasive erosion has been studied, and the relevant wear-rate equations are presented.

In order to solve the problem that super-high pressure compressor pipeline system had serious vibration and noise pollution, finite element method was used in this paper to have system vibration analysis and a vibration control program was designed by changing system inflexibility. On the other hand, in order to improve the efficiency of simulation modeling, the ANSYS parametric design language?APDL?was used to build pipeline system vibration analysis models which can be revised by test data and recover vibration field. After the implementation of the program, test data showed that the vibration displacement drop greatly, all displacement values meet compressor vibration norms. The result proved that the APDL-based finite element analysis approach was an effective way to have super-high pressure compressor pipeline system vibration control, which solved hand-modeling inefficiency issues and improved the efficiency of the simulation modeling.