The mechanism of yarn tensile breakage
Strength and elasticity are two important properties of spinning yarn. The mechanical properties of spinning yarn refer to the mechanical properties of spinning yarn when subjected to mechanical action. It is an extremely important content to characterize the finishing and use performance of spinning yarn. Due to the relaxed viscoelastic properties of fiber polymer molecules, the response of spinning yarn to external effects is quite complex. Here we only describe the calculation of the strength and elasticity indicators of spinning yarns, which are closely related to fabric technology and fabric properties. 1. The strength of spinning yarn The strength of spinning yarn has an extremely important impact on the strength and wearing performance of the fabric, which mainly includes tensile resistance, bending resistance, torsion resistance, compression resistance and friction and cohesion strength. Here we only discuss spinning yarn Calculation of tensile strength of wire. (1) Mechanism of tensile breakage of spinning yarns Generally, the reasons for the breakage of spinning yarns include fiber breakage and fiber slippage, both of which coexist at the same time. The possibility of fiber slippage depends on the friction and cohesion between fibers. When the frictional cohesion force on the fiber is greater than the breaking strength of the fiber, the fiber appears to be broken; when the frictional cohesion force on the fiber is less than the breaking strength of the fiber, the fiber slips. The size of the frictional cohesion force experienced by the fiber is related to the length of the fiber. The length of the fiber when the friction saturation force is equal to the fiber strength is called the “slip length”. Therefore, fibers whose fiber length is less than twice the slip length must slip when the spinning yarn breaks. In order to ensure the strength of the yarn, fibers less than twice the slip length should be used. For example, the slip length of cotton fiber is about 8mm, so 16mm is used as the boundary between fine-staple cotton and short lint. Due to the non-synchronous breakage, fiber slippage and twisting, the fibers in the spinning yarn are tilted, resulting in tension, elongation and other factors. The strength of the spinning yarn is equal to the sum of the strength of the fibers in a certain section of the spinning yarn. Not equal. The difference between the two can be expressed by the strength utilization coefficient of the fiber in the spinning yarn. The strength utilization coefficient of fibers in a spinning yarn refers to the ratio of the single fiber strength converted by the spinning yarn strength to the sum of the single fiber strengths of n fibers in a certain section of the spinning yarn. The strength utilization coefficient of fibers in general spinning yarns is less than 1. The strength utilization coefficient depends on the structure of the spinning yarn and the properties of the fibers that make up the spinning yarn. The strength utilization coefficient of filament yarn is greater than that of short fiber yarn. For example, the strength utilization coefficient of nylon filament is 0.8-0.9, while the viscose short fiber yarn is 0.65-0.70, the cotton yarn is 0.4-0.5, and the combed wool yarn is 0.25-0.3.
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