Testing And Study On Damage Of Cotton Yarn During High-speed Warp Knitting

The natural fiber in staple yarn is represented by cotton and linen,which is a kind of green material of natural environmental protection.Natural short fiber warp knitting products with good moisture absorption,good skin comfort and other characteristics are chosen by people,gradually used in the field of taking,home and decoration.However,in the process of warp knitting,there are many problems such as broken yarn and flying flowers.In order to solve the problem of staple yarn in warp knitting,the damage mechanism of cotton yarn in the process of high-speed warp knitting was studied.Different kinds of cotton yarns are tested and simulated by means of comparative experimental analysis and finite element simulation analysis,which provides a basis for improving cotton yarn raw materials,improving warp knitting machine parts and removing hairiness.First of all,this paper mainly introduces the research and application of staple yarn in warp knitting.The advantages and disadvantages of staple yarn warp knitting at present are put forward,and the research status of finite element analysis in textile is summarized,which provides theoretical support for the development of the subject.In addition,the requirements for cotton yarns in warp knitting production are briefly introduced,several kinds of cotton yarns that meet the basic requirements are listed,and their mechanical properties,hairiness and twist are tested and analyzed.Secondly,the stress and motion of different cotton yarn and warp knitting machine are analyzed in detail,and the damage of cotton yarn in warp knitting process is studied from four aspects by dynamically collecting the samples of different cotton yarns after they have gone through the reed,tension bar and guide needle in high-speed warp knitting process.First,the morphology of cotton yarns after different warp knitting machines was characterized and tested,and the damage of different kinds of cotton yarns after the warp knitting process was explored.Secondly,the mechanical properties of cotton yarn after passing through different warp knitting machines are tested,and the changes of mechanical properties of cotton yarn after passing through different warp knitting machines are discussed.Thirdly,hairiness index of cotton yarn after different warp knitting parts was tested.The increase of hairiness index was mainly concentrated in the process of cotton yarn passing through the tension rod,and the hairiness index of cotton yarn after the guide needle was reduced due to friction and other reasons.Fourthly,the twist change of cotton yarn after warp knitting was tested.The result showed that the twist of cotton yarn decreased all the time,and the decrease of twist of cotton yarn would directly affect the breaking strength of cotton yarn.Finally,SOLIDWORKS software was used to establish a cotton yarn model in this paper.The model was imported into ABAQUS to simulate the tensile fracture process of cotton yarn model,and the stress/strain distribution of cotton yarn model was obtained.Compared with the experimental results,the load-displacement curves of the two are basically similar.In the finite element software,the warp knitting motion is equivalent to the repeated stretching motion of cotton yarn model to simulate its damage condition and stress and strain distribution.The results show that the damage pattern of simulated tensile fracture of cotton yarn model is basically the same as that of the test sample,and the finite element results of simulated equivalent warp knitting can also reflect the damage of cotton yarn in the actual warp knitting process.