Research On Tribological Behavior Of Fiber-reinforced Nylon Roller In Rolling Contact

Polymer roller is widespread used in spinning-weaving, printing-dyeing and steel rolling industry as a transport component. It commonly consists of steel core and polymer layer wrapped around the core. Good service life and surface quality of the roller is fundamental to the continuous production and the surface quality of strip steel, and can significantly save cost in production. Nylon roller frequently serves as transporting roller in strip steel cold rolling industry on behalf of its good mechanical strength and wear resistance. But under high load, speed and surface roughness condition, the wear rate of nylon roller was too large. The production has to be shut down to replace the roller and the strips adhered by abrasions of roller were also degraded, which will result in great economic loss. The new roller with excellent wear resistance and surface cleanness is urgently required. Numerous researches have proved that the fiber-reinforced composite behaves better tribological properties with smaller friction coefficient and lower wear rate than its matrix material. But few literatures have taken the counterpart surface quality into consideration. Moreover, wear mechanism of side-slipping rolling contact differs from the differential-sliding rolling contact which was studied by most scholars. Therefore, the existing tribological theory can not evaluate the tribological behavior of fiber-reinforced nylon roller under side-slipping rolling with strip steel effectively.In this dissertation, wear forms and mechanism of nylon roller was discussed firstly. Scanning electron microscopy, Fourier transform infrared spectrometer and energy dispersive spectrometer were used to analyze the chemical constitution of black covering on roller surface. The test results indicated that the black coverings were a mixture of iron fines and nylon debris. Meanwhile, the relationship between the wear forms and deviation mounting angle of nylon roller was discussed that small deviation mounting angle will benefit the forming of black coverings on roller surface with low wear rate and large deviation mounting angle will induce the polishing of roller surface with large wear rate. Besides adjusting the deviation mounting angle, to reinforce nylon with fiber could be a better proposal to improve its tribological property.To make a comprehensive understanding of mechanical and tribological performance of fiber-reinforced polymer composite, prediction model for visco-elastic behavior of fiber-reinforced composite was developed to discuss the effect of fiber content, fiber properties and fiber distribution on composite’s static and dynamic mechanical properties. Moreover, finite element method, static tensile test and dynamic mechanical test were also employed to testify the accuracy of the prediction model. Meanwhile, rolling contact model of short fiber-reinforced visco-elastic layer with rigid cylinder was also developed to study the effect of fiber content, strip steel weight and running speed on the macro-contact characterization between fiber-reinforced nylon roller and strip steel. The results show that the rolling friction coefficient between roller and strip steel decreases with a increasing content of fiber, increases with a increasing strip steel weight considerably and diverse a little with the changing rolling speed. Furthermore, finite element method (FEM) analysis of contact behavior between fiber-reinforced composite with rigid plane was also engaged to study the effect of fiber on stress field distribution in contact zone in a micro scale. The FEM results reveals that the stress of the matrix beneath the fiber is released and intensified that above the fiber, fiber endures a much higher stress than the matrix on contact surface, and the matrix around fiber also experiences higher stress than the matrix away from fiber in contact zone.A new kind of side-slipping rolling wear testing rig was invented to investigate the tribological behavior of glass fiber-reinforced nylon with steel plate under rolling and side-slipping rolling in diverse load, speed, temperature and side-slipping angle condition. Torque monitor system, precision electronic balance, scanning electron microscopy and optical microscope were utilized to analyze the testing results. The relation between glass fiber content, load, temperature, rolling speed and side-slipping angle and friction coefficient, wear rate and wear morphology were discussed, and wear mechanisms of glass fiber-reinforced nylon composite under rolling and side-slipping rolling test were clarified. The main testing results reveal that the wear form of glass fiber-reinforced nylon in side-slipping rolling is a combination of adhesive wear and abrasion wear, and glass fiber can effectively reduces the wear rate of nylon in all test conditions. To achieve low friction coefficient and good surface quality of both testing sample and counter disc, glass fiber content and side-slipping angle should match with each other.In summary, wear mechanism of nylon transport roller was clarified, prediction model for visco-elastic behavior of fiber-reinforced composite as well as rolling contact model of short fiber-reinforced visco-elastic layer with rigid cylinder was developed, side-slipping rolling wear testing rig was invented, and wear mechanisms of fiber-reinforced polymer composite under rolling and side-slipping rolling test were clarified. The research in this dissertation will provide guideline for the design of transport roller, and also will lay out footstone for further study of wear behavior in form of side-slipping rolling contact.