纱条中纤维排列的模拟及其对成纱质量的影响

发布时间：2018-05-24 20:42

本文选题：纤维随机排列 + 纤维几何特征　；参考：《东华大学》2017年博士论文

【摘要】：纤维性能对成纱质量的影响一直是纺织领域的经典课题之一。其中,纤维在纱条中的排列状态不仅影响着纺纱过程,也直接决定了纱或线的条干均匀度、断裂强力等性能,从而对后续织造工艺和最终纺织品的质量产生影响。纤维在纱条中的随机排列很大程度上取决于纤维的几何特征(长度、细度)。因此,模拟纤维在纱条中随机排列将有助于从理论上认识纤维几何特征对成纱质量的影响机理,这对于原料配置的优化、纺纱工艺的改进、优质纱线的生产都具有指导意义。本研究从模拟纤维在纱条中的随机排列出发,探讨纤维的长度和细度对成纱条干极限不匀(或称为理论不匀)的综合影响。然后根据此模拟建立单纱断裂强力的计算方法,并据此分析单纱断裂强力的影响因素。单纱拉伸断裂过程中断裂截面上的纤维可能会发生断裂或者滑脱,这取决于临界滑脱长度。临界滑脱长度的求解不仅与纤维性质有关,还取决于单纱的加捻。单纱的加捻程度还决定了断裂纤维和滑脱纤维对单纱断裂强力的实际贡献。本研究采用模拟方法建立了计算的理论模型,并对理论计算值采用实验和文献数据验证分析。由于纤维头端位置以及长度、细度指标具有随机性,在模拟纤维排列时采用Monte Carlo的方法对这些随机变量进行生成,使其能够与实际相符合。关于成纱性能的分析和临界滑脱长度的推导还采用了几何概率方法。为便于模拟和计算,本研究未考虑纺纱过程中机械因素以及纤维形态(或弯钩)对成纱质量的影响。论文按照研究内容共分为五章,其中各章的主要工作如下:论文的第一章介绍了研究的背景,并在文献综述中着重介绍了国内外关于纤维在纱条中随机分布、成纱条干不匀和断裂强力的理论研究模型,并介绍了这些研究中所存在的问题。论文的第二章首先基于纤维左头端沿纱轴方向呈均匀分布的假设,模拟了纤维在纱条中随机排列,模拟纱条的条干极限不匀是通过计算从纱条截取的各子片段中包含所有纤维总重量的不匀来表示。以单纱8mm片段极限不匀的计算为例,若仅考虑纤维长度因素的影响,计算结果表明,单纱的条干极限不匀随着纤维长度的增加而增加,并最终趋于稳定,这与suh的理论和纺纱实测值的趋势是一致的。对于不等长纤维纱,其条干极限不匀仅与平均纤维长度有关,与纤维长度本身所服从的分布类型无关。若进一步考虑纤维细度的影响,模拟计算结果表明考虑纤维细度分布时计算得到的条干极限不匀率高于未考虑纤维细度分布时的计算结果。其中纤维细度不匀越大,两者之间的差异也越大,考虑纤维细度分布时计算的极限不匀值更趋近于实测值,这说明纤维细度分布对纱条极限不匀的影响是显著的。将纤维长度和细度各指标对条干极限不匀的影响进行综合分析,得到它们的影响程度顺序为:平均纤维细度纤维细度不匀平均纤维长度纤维长度不匀。纤维在纱条中随机排列的模拟是对纱条条干均匀度的直观反映,从而为进一步研究成纱的实际不匀以及成纱断裂强力等性质提供了可行的方法。论文的第三章根据纤维在单纱中的随机排列提出了单纱断裂强力的模拟计算方法。其中单纱断裂中纤维发生的断裂或滑脱取决于临界滑脱长度,发生断裂的纤维对单纱强力的贡献为其本身断裂强力,发生滑脱的纤维对单纱强力的贡献为其平均滑脱摩擦力,它们的贡献之和就为单纱的断裂强力。据此可计算模拟单纱中各个截面可能发生断裂时的强力,其中的最小值就为整个单纱的断裂强力。从模拟计算结果可以看出,当纤维长度增加或临界滑脱长度减小时,发生断裂的纤维数目增多,发生滑脱的纤维数目减少,因而单纱的断裂强力就呈增加趋势,这是与纺纱实测值的趋势是一致的。而对于不等长纤维纱,其断裂强力还与纤维长度本身的分布形式有关。此外,模拟单纱片段长度越长,单纱断裂强力的计算值也越低,这也是与前人得到的理论和实验结论相一致。由于考虑了单纱截面纤维根数的变异,采用纤维在单纱中随机排列的模拟计算成纱断裂强力更加合理可靠,它能够直观反映纤维长度对成纱强力的影响,也能够直观反映单纱中出现的弱节,因此它可以用于单纱断裂强力的预测。论文的第四章基于单纱结构的假设,探讨了临界滑脱长度的近似计算方法,并对第三章单纱断裂强力的模拟计算方法进行了修正。临界滑脱长度的近似表达式不仅考虑了纤维的力学性能,还考虑了单纱加捻的影响。计算结果表明临界滑脱长度随着捻系数的增加而下降。由于单纱加捻造成纤维断裂强力的损失,因此发生断裂的纤维和发生滑脱纤维对单纱强力的贡献需要进一步的修正,并将其代入第三章提出的单纱断裂强力模拟计算方法中进行强力计算。从模拟计算结果可以看出,单纱断裂强力的模拟计算值随着捻系数的增加先上升至最高值而后发生下降,这是与实测值的变化趋势是一致的。低于临界捻系数时,临界滑脱长度的下降使发生滑脱的纤维根数减小,且发生断裂的纤维增多,这导致单纱强力随捻系数的增加而上升。而在高于临界捻系数时,纤维因强力损失过大导致其有效强力的剧烈降低,并且纤维有效强力沿纱轴方向上的分力也大大减小,这将最终导致单纱强力的下降。此外,对于等长纤维,各纤维指标对单纱断裂强力的影响程度顺序为:纤维细度纤维强力纤维长度。临界滑脱长度的求解和单纱断裂强力的计算能够揭示单纱随捻系数变化的断裂机理,它是合理且符合实际的。论文的第五章是对本论文的主要贡献和不足之处进行了总结,并且提出了本课题未来的研究方向。综上所述,本研究通过模拟纤维在纱条中的随机排列,对成纱条干极限不匀和断裂强力分别进行了计算,其能够较为直观地揭示了纤维的几何特征对成纱质量的影响机理,为纤维原料的配置、纺纱工艺的优化及成纱性能的预测提供了理论依据。
[Abstract]:The effect of fiber properties on yarn quality has always been one of the classic topics in the textile field. The arrangement of fiber in yarn not only affects the spinning process, but also directly determines the evenness of yarn or thread, breaking strength and so on, thus affecting the quality of subsequent weaving and final textiles. Fiber is in yarn bar. The random arrangement of the medium depends largely on the geometric characteristics (length, fineness) of the fiber. Therefore, the random arrangement of the simulated fibers in the yarn will help to understand the mechanism of the influence of the geometric characteristics of the fiber on the yarn quality in theory, which is of guiding significance to the optimization of the configuration of the raw materials, the improvement of the spinning technology and the production of high quality yarns. Based on the random arrangement of simulated fiber in yarn bar, the effect of length and fineness of fiber on the limit unevenness of yarn evenness (or theory unevenness) is discussed. Then, the calculation method of breaking strength of single yarn is established according to this simulation, and the influence factors of single yarn fracture strength are analyzed. The fiber on the section may break or slip, which depends on the length of the critical slipping. The calculation of the critical slipping length is not only related to the properties of the fibers, but also depends on the twisting of the single yarn. The twist degree of the single yarn also determines the actual contribution of the broken fiber and the slipping fiber to the breaking strength of the single yarn. The theoretical model is calculated, and the theoretical calculation values are tested and analyzed by the literature data. Due to the randomness of the end position and length of the fiber head and the fineness index, the Monte Carlo method is used to generate these random variables in the simulation of the fiber arrangement, so that it can be in conformity with the actual phase. In order to facilitate the simulation and calculation, the effect of mechanical factors and fiber form (or hook) on yarn quality is not considered in this study. The main work of this paper is divided into five chapters. The main work of each chapter is as follows: the first chapter of the paper introduces the background of the study and is used in the first chapter of the paper. In the literature review, the theoretical research model about the random distribution of fiber in yarn and the unsymmetry breaking strength of yarn evenness and breaking strength is introduced in the literature, and the problems in these studies are introduced. The second chapter of the paper is based on the assumption that the left end of the fiber is uniformly distributed in the direction of the yarn axis, and the random arrangement of the fiber in the yarn bar is simulated. The unevenness of the dry limit of a simulated yarn is expressed by calculating the unevenness of the total weight of all the fibers in each fragment intercepted from the yarn. Taking the calculation of the limit unevenness of the single yarn 8mm fragment as an example, if only the influence of the fiber length factor is considered, the calculation results show that the dry limit of the single yarn increases with the increase of fiber length. It is consistent with the trend of the Suh theory and the measured value of spinning. For unequal length fiber yarn, the dry limit of the yarn is only related to the average fiber length, and is independent of the distribution type of fiber length itself. If further consideration of the fiber fineness, the simulation results show that the fiber fineness distribution is considered. The ultimate unevenness of the strip is higher than that of the calculation of the fiber fineness distribution. The greater the fiber fineness is, the greater the difference between the two. The limit unevenness calculated by the fiber fineness distribution is closer to the measured value, which shows that the fiber fineness distribution has a significant effect on the limit unevenness of the yarn. The influence of fiber length and fineness on the ultimate unevenness of the strip is analyzed synthetically, and the order of their influence is as follows: the average fiber length of average fiber fineness is not uniform. The simulation of the random arrangement of fiber in the yarn is a direct reflection of the evenness of the yarn evenness, thus further research is made. In the third chapter of the paper, the fracture strength of single yarn is calculated according to the random arrangement of fiber in single yarn. The fracture or slipping of fiber in single yarn fracture depends on the length of critical slipping and the strength of broken fiber to single yarn. The contribution of the fibers to the strength of the single yarn is the strength of the single yarn. The contribution of the fibers to the strength of single yarn is the breaking strength of the single yarn. According to this, the strength of each section in the single yarn may be calculated. The minimum value is the breaking strength of the whole single yarn. It can be seen that when the length of fiber increases or the length of critical slipping decreases, the number of broken fibers increases and the number of slipping fibers decreases, so the breaking strength of the single yarn increases, which is consistent with the trend measured by the spinning yarn, and the breaking strength of unequal length fiber yarn is also with the fiber length itself. In addition, the longer the length of the single yarn fragment, the lower the calculated value of single yarn breaking strength, which is in accordance with the theoretical and experimental conclusions obtained by the predecessors. Considering the variation of the fiber root number of single yarn cross section, it is more reasonable and reliable to calculate the breaking strength of yarn by random arrangement of fiber in single yarn. It can directly reflect the influence of fiber length on yarn strength and can also directly reflect the weak joints appearing in single yarn. Therefore, it can be used to predict the breaking strength of single yarn. The fourth chapter of the paper discusses the approximate calculation method of critical slip length based on the assumption of single yarn structure, and the simulation calculation method of breaking strength of single yarn in third chapters is entered. The approximate expression of the critical slipping length not only takes into account the mechanical properties of the fibers, but also considers the effect of the single yarn twisting. The calculation results show that the critical slipping length decreases with the increase of the twist factor. The fiber and the slipping fiber are produced to the single yarn because of the loss of the breaking strength of the fiber. The strength of the contribution needs further correction, and it is replaced in the third chapter of the single yarn fracture strength simulation calculation method to carry out strength calculation. From the simulation results, it can be seen that the simulation calculation value of single yarn breaking strength first rises to the highest value with the increase of the twist factor and then drops, which is the change trend with the measured value. It is the same. When the critical twist factor is lower, the decrease of the critical slipping length makes the number of slipping fibers decrease and the broken fibers increase, which leads to the increase of the strength of the single yarn with the increase of the twist factor. The strength of the strength along the axis of the yarn will be greatly reduced, which will eventually lead to a decrease in the strength of the single yarn. In addition, the order of the influence of the fiber index to the breaking strength of the single yarn is: the length of the fiber strength fiber, the calculation of the critical slipping length and the calculation of the single yarn breaking strength can reveal the single yarn with the twist system. The fifth chapter of the paper is a summary of the main contributions and shortcomings of this paper, and the future research direction of this subject is put forward. In summary, this study is based on the random arrangement of simulated fibers in the yarn, and the strength of the yarn evenness is not uniform and breaking strength respectively. The calculation has been carried out to reveal the influence mechanism of the geometric characteristics of the fiber on the yarn quality, which provides a theoretical basis for the configuration of fiber materials, the optimization of spinning technology and the prediction of yarn properties.
【学位授予单位】：东华大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TS104.1

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