Conglin Dong

Study on wear behaviour and wear model of nitrile butadiene rubber under water lubricated conditions

Nitrile Butadiene Rubber (NBR) is widely used to make water-lubricated rubber stern tube bearings in the marine field. Its tribological properties, which significantly influence its reliable life, directly affect the safe navigation, covert performance and operating costs of a ship. This study aimed to investigate the tribological properties and wear model of NBR under water-lubricated conditions. A CBZ-1 tribo-tester was used to conduct sliding wear tests between NBR pins and 1Cr18Ni9Ti stainless steel discs under water-lubricated conditions. The surface morphologies of the worn NBR pins were examined using laser-interference profilometry and scanning electron microscopy. In addition, the friction coefficients, ageing times and wear rates were analysed and compared to study the tribological properties of NBR and to identify the factors that affect its wear mass loss. The results demonstrated that different ageing times, velocities and loads had a significant effect on the friction and wear properties of the NBR specimens. The ageing times positively correlated with the friction coefficients and the wear mass losses between the rubbing pairs. The anti-tear properties of NBR deteriorated when the material was aged at a high temperature for an extended period of time, which reduced its wear-resistance. The main wear mechanism between the rubbing pairs was severe adhesion tearing wear under the water-lubricated conditions. A comprehensive empirical model for its wear rate estimation was established based on the wear and friction power. The model revealed the relationships between wear and velocity, as well as load and shore hardness. The result produced by the model was largely consistent with the experimental results. The knowledge gained in this study is anticipated to provide the theoretical data for a wear theory study of NBR and be useful for the optimisation of water-lubricated rubber stern tube bearings.

Marine environmental damage effects of solar cell panel

Solar cell is one of the crucial components in photovoltaic systems. At present, substrate crystalline silicon solar cells with clear cover glasses are widely used in photovoltaic systems. The solar panels are made of semiconducting materials including mono crystalline silicon, polycrystalline silicon and gallium arsenide (GaAs). The high transmittance glass cover is pressed together with the panel through silicone rubber, which provides a strong protection for the core solar cells. A key issue of the photovoltaic system is the photovoltaic conversion efficiency, which not only depends on the conversion efficiency of the semiconducting silicon, but also is closely related to the transmittance of the cover glass. The photovoltaic conversion efficiency will definitely reduce with the attenuation of spectral transmittance. The rigorous environment where the solar cells are used in, such as in space radiation, desert and marine environments, will cause contamination, corrosion, wear and deterioration of the optical properties of the glass cover. The results in this study show that the spectral transmittance of the cover glass decreases with the increase of the submerging time in seawater. Therefore, it is necessary to study the attenuation of the optical properties of the cover glass and to characterise surface damage. Progress in research on environmental damage effect of solar panels has been reviewed and presented in this paper. The future direction of the research in this field has also been explored.

Study on fatigue life evaluation of water lubricated rubber stern tube bearing

The study on how to use the water medium replacing mineral oil as the lubricating medium of the ship propulsion system, is the high efficient energy-saving of the mechanical transmission system and the frontage of the environmental protection scientific research. The water lubricated rubber stern tube bearing is a very important supporting part of the ship propulsion system, its reliability life will directly affect the safe navigation, covert performance and operating costs of ship. The fatigue life of rubber stern tube bearing is one of the most important indexes. This paper simplifies the contact stress model between the water lubricated rubber stern tube bearing and the stern tube. It designs a simulation program for the fatigue life of the bottom rubber bearing plate whose contact stress is the most complex, lubrication condition is the most harsh, reliability life is the shortest, and which determines the reliability life of the ship water lubricated planar rubber stern tube bearing. It is believed that the knowledge gained in this study will provide the theoretical data for researching on reliability life theory of ship water lubricated rubber stern tube bearing and guide for when repair or change the ship water lubricated rubber stern tube bearing in shipping service industry.

Reliability Evaluation of Marine Propulsion Shaft Based on Stress-Strength Interference Theory

Ships play an important role in waterway transportation and ocean development. A core component of a ship is its marine propulsion system, in which the marine propulsion shaft is an important constituent. With the development of large-scale ships, the reliability of the marine propulsion shaft under the extreme sea state has attracted many attentions from the users and scholars. This paper focuses on studying how the action time of the random load and severe sea state influences the reliabilities of the marine propulsion shaft when its strength had not or less degenerated. The stress-strength interference theory was used to evaluate the reliability of the marine propulsion shaft. Firstly, the stresses at the maximum deformation of the marine propulsion shaft under the different sea states were obtained using finite element simulation method. The calculation results fitted well with the actual situation. The action times of the random load and severe sea states had significant effects on the reliability of the marine propulsion shaft. The reliabilities decreased as the actions times increased, and decreased sharply under the severe sea states (sea states 8 and 9). The decreasing trends of the reliability and failure rate became more obvious and steeper when the action times were less than 2000 under the different sea states, and more slowly when the action times were from 2000 to 5000. It believed that the knowledge gained in this study will provide the theoretical model for researching on the reliability evaluation theory of ship propulsion system and protecting the ships completing their missions reliably and safely.Copyright