Abstract:

Objective In order to study the damage of wool yarn in the process of warping for warp knitted fabrics, the study focused on the warping tension and the influence of machine parts on the hairiness index and mechanical properties of wool yarn, using the yarn leasing reed as an example, aiming to understand the damage of wool yarn during warping and provide insights for the utilization of wool yarn.

Methods Three types of compact Siro-spun yarns prepared from wool, cashmere, and nylon staple fibers were selected. The warping machine served as the experimental platform for sampling, testing, and analysis. The mechanical properties and hairiness index of the three types of yarns were tested before and after warping. A mathematical model was developed to analyze and predict the influence of warping tension on yarn performance based on the relationship between tension, yarn strength loss, and mass loss. The damage to wool yarn caused by warping tension, reed, and KFD yarn tension compensation brake was simulated and validated using finite element modeling.

Results Three types of wool yarn were tested after warping on the warping machine. These included yarn A (70% wool and 30% polyamide, 16.7 tex), yarn B (60% wool, 30% polyamide and 10% cashmere, 16.7 tex), and yarn C (60% wool, 30% polyamide and 10% cashmere, 12.5 tex) which were subjected to tight Siro spinning. The study revealed that the mechanical properties and hairiness index of the yarn were influenced by the friction between the reed of the warping machine and the yarn. Yarns A, B, and C experienced a decrease in strength by 12.0%, 10.7% and 8.2%, respectively. Additionally, due to shedding and the generation of new hairiness during continuous friction with the reed, the hairiness index fluctuated, leading to an overall weight decrease. During the warping process, if the yarn warping tension exceeded 30 cN and the elongation surpassed 0.8%, warping failure could occur due to hairiness aggregation, yarn entanglement and other factors. At the same time, the relationship between yarn strength, mass, and warping tension adhered to asymptotic, Boltzmann, and other mathematical models. Based on the model curve, it was deduced that when the warping tension was 20 cN and the warping speed was 300 m/min, the tension roller hole selection should be the second hole position; or when the warping speed was 400 m/min, the tension roller hole selection should be the first hole position. Under these conditions of warping tension and speed, both warping efficiency and quality could be guaranteed. By establishing the equivalent model of wool yarn, the finite element method was utilized to simulate the warping process and further investigate the damage of wool yarn. The simulation results were compared with the actual scenario to replicate the morphological changes of the yarn during warping and confirm the warping of the yarn under various tension and elongation conditions. This study provided a valuable experimental and theoretical foundation for examining short fiber yarn for warp knitting and exploring yarn damage during the warping process.

Conclusion The relationship between mechanical properties and hairiness index was established. According to the mathematical model, when the warping tension was 20 cN and the warping speed was 300 m/min, the tension roller hole selection was the second hole position, or when the warping speed was 400 m/min, the tension roller hole selection was the first hole position. Under these conditions, the weight loss and strength loss were kept minimal. By comparing the finite element modeling with test data, it was deduced that warping would be hindered when the warping tension exceeded 30 cN and the elongation surpassed 0.8% due to hairiness aggregation, yarn entanglement and the like. the like This method allowed for the preliminary screening of warping yarn, offering a theoretical foundation for the warping process.

Key words: warping damage, wool yarn, strength, hairiness, mathematical model, finite element simulation