| With the continuous progress of fiber material properties and rope-making technology,fiber rope plays an important role in many fields,such as aerospace,marine engineering,national defense and military industry,fire rescue,and so on.In the process of using fiber rope,there are many stress forms such as stretching,bending,and so on.In the process of repeated stress,there will be repeated friction between strands and between fibers,and finally,failure.Therefore,it is of great significance for understanding the failure mechanism of fiber ropes and developing wear-resistant coatings to systematically explore the friction properties between commonly used fibers in ropes and cables.Taking the fibers commonly used in marine engineering ropes and cables,including ultra-high molecular weight polyethylene(UHMWPE),polyester(PET),aramid(Kevlar),and polyarylate(Vectran)as the research object.,this paper experimentally studies the effects of different environments and experimental parameters on the friction fatigue of yarn and yarn and reveals the friction performance and fatigue failure mechanism of the internal yarn of friction ropes and cables in the friction process by taking the friction coefficient as the medium,The prediction model of yarn friction fatigue life is established.Through the above work,the yarn friction tester test equipment and yarn friction coefficient test equipment is built.The influencing factors,failure evolution process,and life prediction related to yarn friction fatigue are described,which provides experimental and theoretical support for rope and cable failure analysis.The research contents are as follows:(1)Two sets of devices,yarn friction fatigue tester,and yarn friction coefficient tester,are built.Under the framework of relevant standards,a yarn friction fatigue tester for industrial use and a yarn friction coefficient tester for scientific research is built.Both devices can realize the test of yarn friction performance in dry and wet states,and have the functions of controllable tension and frequency,automatic stop of yarn breaking,automatic summary,and so on.The development of the equipment fills the gap in domestic fiber yarn friction testing equipment and provides data support for relevant basic research work.(2)The experimental environment(dry and wet state),experimental conditions(pretension,friction frequency),and other factors were systematically discussed on the effects of UHMWPE,PET,Kevlar,and Vectran.Effects of four fiber yarns on the friction and fatigue properties of yarns.The experimental results show that the friction fatigue life of the four fibers decreases with the increase of pre-tension.Under the same pre-tension,the effects of different friction frequencies on the four different fibers are different.Among them,the friction fatigue life of polyester continued to decrease with the increase of friction frequency,while the UHMWPE fiber showed a trend of increasing first and then decreasing.The overall friction fatigue life of aramid fiber was less affected by friction frequency,and the friction fatigue life of polyarylate fiber was higher than that of friction.When the frequency is lower than 0.5Hz,the change is not obvious,and the decrease is obvious when the frequency is higher than 0.5Hz.In the wet state,the friction fatigue life of UHMWPE fiber and polyester fiber increased significantly,while the friction fatigue life of aramid fiber and polyarylate fiber decreased.(3)The evolution process of friction coefficient in the process of yarn friction fatigue is studied,and then the evolution process of yarn friction form in the process of friction fatigue is further revealed.The test of the friction coefficient of four fibers in the process of yarn friction shows that the friction coefficient of aramid yarn first decreases and then increases with the friction process,which is about 0.078 at the beginning of friction,then decreases to 0.04-0.05,and then fluctuates between 0.05 and 0.06 with the increase of friction cycle.The friction coefficient of Polyarylate fiber yarn experiences a process of first decreasing,then increasing,and then decreasing.The friction coefficient is about 0.067 at the beginning of the friction and then decreases.After 450 friction cycles,the friction coefficient is the lowest at 0.045,and then the friction coefficient starts with the friction.It increased up to a maximum of 0.074 and then began to decrease again,with the friction coefficient fluctuating between 0.04 and 0.05 after 1000 friction cycles.The friction coefficient of UHMWPE fiber yarn shows an overall increasing trend.The friction coefficient of the first 500 times is about 0.020,and it fluctuates between 0.04 and 0.05 when the friction is about 2000 times.When the friction cycle reaches 4500 times,the friction coefficient continues to increase,and finally fluctuated around 0.09.During the friction process of polyester fiber yarn,the friction coefficient is always below 0.035,which reflects the excellent wear resistance of polyester fiber.(4)The failure mechanism of friction fatigue of different fiber yarns is revealed,and its fatigue life is predicted.The study shows that different molecular stiffness has a great influence on the failure mechanism of fibers.Due to their excellent heat resistance,the failure process of rigid chain aramid fiber and Polyarylate fiber is mainly mechanical wear,while the friction fatigue failure process of ultrahigh molecular weight polyethylene fiber and polyester fiber yarn is a failure process under the combined action of thermal effect and mechanical wear.The two effects are coupled with each other,which eventually leads to the friction fatigue failure of fiber.Using the artificial neural network as a tool and relying on experimental data,make full use of the adaptive ability of the neural network to carry out life predictions.It can be seen from the network training that the neural network has very high accuracy for fitting the friction fatigue life of yarn,and the overall correlation reaches more than 99%.Through the above work,the preset goal of the subject is completed,and it provides theoretical support and an experimental basis for further discussion on improving yarn friction properties by coating or other methods. |
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