In the drafting process, the strength and distribution of the friction field determines the fiber movement state, affecting the yarn formation process and yarn properties directly. The bottom pin, as an important part in the drafting zone, forms an elastic friction field with the top pin through the apron, which has an important influence on yarn properties. This work is aiming to compare the different friction fields generated by two bottom pins and its mechanical effect on fibers, revealing the influence of the friction field on the quality of yarns with different counts. Theoretical and experimental results show that a larger and stronger friction field was formed by the smaller surface curvature and flatter transition level of bottom pins, imposing a positive effect on the yarn evenness and strength. The difference in evenness between yarns spun with the two types of pins vary from 4.3% to 9.8%, while the yarn spun with a flatter bottom pin has higher strength (maximum difference to 17.1%). This study on the influence of the friction field on yarn properties can clarify the adaptability of different bottom pins for the production of different yarn counts, showing great significance on the actual control of yarn properties and property improvement.

中文翻译：

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环锭纺牵伸系统不同下针摩擦场对比分析及其对纱线性能的影响

在牵伸过程中，摩擦场的强度和分布决定了纤维的运动状态，直接影响纱线的形成过程和纱线性能。下针作为牵伸区的重要部件，通过皮圈与上针形成弹性摩擦场，对纱线性能有重要影响。本工作旨在比较两个底针产生的不同摩擦场及其对纤维的机械效应，揭示摩擦场对不同支数纱线质量的影响。理论和实验结果表明，底针较小的表面曲率和较平坦的过渡平面形成了更大更强的摩擦场，对纱线条干和强力产生积极影响。用两种类型的针纺成的纱线之间的均匀度差异从4.3%到9.8%不等，而用更平坦的底针纺成的纱线具有更高的强度（最大差异为17.1%）。研究摩擦场对纱线性能的影响，可以明确不同底针对不同纱线支数生产的适应性，对纱线性能的实际控制和性能改进具有重要意义。