Test method of yarn diameter
1. Optical projection method Put the yarn under a microscope with an eyepiece measuring ruler at about 100 times, or under a projector with the same magnification, apply a predetermined tension, and then focus on the shape of the yarn surface projection. Determine the diameter standard after hairiness is removed, and randomly select inspection points on the yarn at a certain interval, and after obtaining more than 300 observation values, calculate the average value of the yarn diameter by statistical methods. Due to the fuzzy characteristics of the yarn diameter boundary, the artificial definition of the yarn diameter to remove the fuzzy boundary of the yarn hairiness is affected by human subjective factors. This method has human-observed visual errors, but because the yarn has been magnified by 100 times during testing, the accuracy of visual inspection is improved, and the test results are relatively correct. The disadvantage of this method is that the sample requires many test points, the operation is time-consuming and laborious, and the test efficiency is low. 2. Indirect calculation method Due to the shortcomings of the optical projection method to determine the diameter, the diameter calculation method derived from the yarn fineness formula is developed. Suppose the yarn is a cylinder, the length is L (mm), the weight is G (mg), the cross-sectional area is S (mm²), the volume weight is δ (g/cm³), and the diameter is d (mm), then: yarn diameter The relationship between yarn characteristics Nt, metric count Nm, and fineness D is: the volume weight δ of the yarn is related to the nature of the fiber and the twist of the yarn. The volume weight values u200bu200bof several common yarns are shown in the table: Expressed by a general formula, the expression of yarn diameter can be written as Kd is called the yarn diameter coefficient. In order to find the diameter of a certain yarn, the diameter coefficient must be measured. The diameter coefficient of the yarn is also measured by the optical projection method. Okay, so the calculation of the diameter is essentially an optical method. The disadvantage of this method is that the yarn diameter coefficient Kd is related to the volume weight of the yarn δ. With different yarn varieties, different blending ratios and the emergence of new types of fibers, the volume and weight of yarns vary greatly, and the calculation of the diameter from the yarn diameter coefficient is greatly restricted.
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