Study On The Mechanism Structural And Mechanical Performance Of Sirospun Composite Yarn

In this thesis,the mechanism of sirospun is studied.Based on objective analysis and reasonable assumption,a general rule is obtained with more precise and conformation to the fact.The results are validated by the experimental analysis.Based on which this research pay more attention to the practicability of this sirospun technique.The purpose of this research is to reveal the relationship and the interrelation influence by component fibers properties,processing parameters of sirospun yarn formation,structural parameters and mechanical parameters of resultant yarn, consequently,the sirospun processing can be optimally controlled,as well obtain resultant yarn with better performance.The method adopted in this research is that the theoretical model,simulated by the experimental results,can be used for prediction results.However,as for the sirospun composite yarn,the structure of which is investigated and found more complicated than ring yarn because of its instability of yarn formation and structural complication. Accordingly,this research has studied the structural characters of sirospun composite yarn by using methods of simulating spinning together with structural image analysis. On the one hand,the stabilization of convergence point can play a major role in the structure and performance of sirospun yarn,as for the dynamic mechanism of sirospun yarn formation,dyed strands are used for spinning processing,while dynamic processing is record by high-speed photography,which can be used for validation the theoretical model;On the other hand,as for the structural configuration of sirospun composite yarn,the method of structural image analysis are used,while the structural image of appearance is recorded by micrograph.Consequently corresponding general rules of sirospun yarn formation and yarn structural parameters can be obtained.As one of modification to the conventional ring spinning technique,the sirospun process,make the new yarn formation,and change the yarn structure or distribution of the fibers in the yarn,therefore,improve the yarn performance.Especially it has not only achieved the complementary of imperfect component fibers properties,and better controlled the composite ratio,but also developed the applicability of yarn.This sirospun composite yarn has caused people's more attention because of its obvious structural configuration and corresponding attractive performance such as well mechanical performance,multi-component fibers,less hairiness,better abrasive resistance,lower production cost and so on.All of which,however,can easily obtain by modifying some processing parameters to the traditional ring spinning.It has some actual application value and instructional significance to technological innovation, upgrading and reformation of 90%of national ring spinning industries.This paper is consisted of 8 chapters.Firstly introduces the background of the study in chapter 1.International and domestic research in current years on development of new spinning methods,technique as well as structural study is described.The existing problems,theories and experimental conclusions in the research are mainly discussed.While chapter 2 or chapter 3 respectively discusses the mechanism,motion of the convergence point and structural character of symmetrical or asymmetrical sirospun composite yarn,firstly developed an improved dynamic model for predicting oscillation motion of the convergence point.Based on reasonable assumption,a solvable theoretical dynamic model was obtained with more precise and conformation to the fact.Comparing to that obtained in opened research,this model presents a more practical expression of sirospun yarn formation based on improved dynamic analysis. The experimental validation shows that oscillating motion of convergence point could be determined by processing parameters of sirospun.With this mode it can easily get the optimal oscillation motion of the convergence point and better structure of yarn formation;Chapter 3 studies the mechanism and performance of asymmetrical sirospun composite yarn,also discusses the relationship between the force,force moment and torsion moment of two strands and spinning parameters,as well as the movement rule of the convergence point.By taking corresponding methods,the instability of convergence point because of the difference of component fibers properties,consequently,the performance of resultant yarn can be effectively improved.However,chapter 4,chapter 5 and chapter 6 focus on the relationship between the processing parameters of sirospun composite yam formation and structural parameters of reluctant yarn.Chapter 4 mainly discusses the mechanism of twist transferring and controlling method on the convergence point.The experimental sirospun yarn formation is carried,in which two different materials are manufactured with different processing parameters and different spinning system respectively is investigated.The result shows that with different oscillation motion of the convergence point determined by processing parameters of traveler weight,there are different structures and performances of the resultant yarn accordingly,by which the optimal results can be obtained.As well as a new approach of improved yarn performance by control on the convergence point with a changed yarn guide has been analyzed and validated;especially,chapter 5 theoretically deduces the relation between the processing parameters such as different gauges of feeding roves, convergence angle and tension of yarn formation,also validated by experiments. Moreover,by structural imaging analysis of symmetric or asymmetric sirospun yarn, choosing and measuring the structural parameters which can reflect not only the processing parameters,but also mechanical parameters.In experiment the parameters of reluctant yarn such as diameter,twist angle and twist pitch are calculated,which can well used as next theoretical model.Chapter 6 mainly discusses the relationship between the component fibers ratio of sirospun composite yarn and the resultant yarn. On the basis of analysis on the mechanism of sirospun yarn formation,structural and breaking,the theoretic breaking strength and elongation expression of different component fiber ratio of sirospun composite yarn is established as well as validated by the experimental results.Therefore,this expression can be used to evaluate the breaking and elongation property of sirospun composite yams,which will be helpful for designing the spinning parameters and processes of sirospun in engineering practice.Chapter 7 gives a new mechanical model for predicting the strength-elongation performance of sirospun composite yarn.Based on the analysis of mechanism of sirospun yarn formation,as well as the mechanical behavior of component fiber and structural configuration,a strength-elongation model of asymmetrical composite yarn is established and well validated by experimental results.Consequently,it can be found that the elongation of composite yarn is determined by that of component fibers with lower elongation but higher modulus,in fact lead to waste some strength contribution provided by the other component fiber with higher elongation but lower modulus.As a result,it will try to avoid using quite difference of elongation in composite yarn formation. This research uses the method that based on analysis of component fibers properties,well considering the processing parameters of sirospun yarn formation and structural parameters of reluctant yarn,mechanical performance can be predicted. This method can be used for better learning the interrelation mechanism,structural configuration and performance of sirospun system,also be referred by and two strand yarn formation,such as sirofil and two-ply yarn.Moreover,the experimental results obtained in this research are also helpful for yarn spinning factory.