1.1 本试验方法 2. 描述了当只需要近似真实捻度时，单纱捻度的测定。 注1: 有关更准确的方法，请参阅测试方法 D1423 . 1.2 本试验方法适用于连续长度的纺纱单纱，也适用于从织物上绕制的纺纱，前提是试样至少为200 mm[8 in]可以获得long。 1.3 该试验方法适用于测定所有类型的单环锭纱的近似捻度含量和纤维含量，但不适用于开口纺纱- 端纺纱线。 1.4 本规范以英寸-磅单位和国际单位显示数值。“英寸-磅”单位是美国常用单位的技术正确名称。“国际单位制”是公制单位的技术更正名称，称为国际单位制。以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值不一定是精确的等价物； 因此，为确保符合本标准，每个系统应独立使用，且两个系统的值不得组合。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 出于经济原因，该测试方法用于行业验收测试，尽管其准确性不如直接测试方法 D1423 . 5.1.1 如果两个实验室（或更多实验室）报告的测试结果之间存在差异或实际意义，则应进行比较测试，以确定它们之间是否存在统计偏差，并使用适当的统计协助。作为最低要求，应使用尽可能均匀的测试样品，从获得不同测试结果的材料中提取，并以相同数量随机分配给每个实验室进行测试。 具有既定测试值的其他材料可用于此目的。应使用未配对数据的统计测试，在测试系列之前选择的概率水平上，比较两个实验室的测试结果。如果发现偏差，必须找到并纠正其原因，或者考虑到已知偏差，调整未来的测试结果。 5.2 当纱线反向加捻时，某些纤维的捻度“设置”会导致过度收缩。 因此，将试样恢复到其原始长度所需的圈数可能小于解缆时移除的圈数。通过使用更高的预拉伸载荷，可以部分抵消这种影响；但这增加了纱线拉伸的危险。关于不同纤维或不同捻度纱线的正确张力，几乎没有可用的信息。 5.3 除了不那么繁琐之外，这种测试方法比直接测试方法需要更少的样本- 计数方法和结果对于某些目的可能足够准确。在主要目标是测量平均值变化的情况下，该测试方法可能有用。另一种可能的应用是需要对类似类型和捻度的纱线进行大量捻度测试。在这种情况下，可以使用比较该方法和直接方法的初步试验来确定正确的预张力。 5.4 捻度对纱线的物理性能有重要影响。 低捻纱是一种高捻度的纱线，由于其柔软、遮盖力强和保暖性，通常是针织的首选。增加捻度可以通过增加纤维内聚力提高纱线强度，但当捻度角度增加超过最佳点时，强度会因有效纤维贡献的损失而降低。通过插入中等捻度来获得最大纱线强度，以在这两个相反的力之间获得最佳平衡。高捻度生产高密度（“硬”或“硬”）和高伸长率的纱线，并可能提高织物的耐磨性和抗冲击性。 5.5 无论是制造效率还是物理性能的最佳捻度通常随着装订长度的减少而增加。 5.6 纱线在包装前的捻度可能与纱线从包装中取出后的捻度不同，这是因为张力的变化和取出方法的影响。按照正常使用的方向从包装中取出纱线，从侧面或反面。如果纱线从末端抽出，则捻度会略有增加或减少，具体取决于纱线中的捻度方向、包装上的卷绕方向以及包装上的卷绕（或包裹）长度。 注2: 从侧面退绕和从上方退绕之间的扭曲度差为1/4π d 哪里 d 是包装的直径。 4. 因此，对于25毫米[1英寸]直径包，差异将约为13 tpm或约三分之一tpi。 5.7 当纱线取自更复杂的纱线结构或织物时，由于退绕、处理和加工过程中遇到的机械应变的影响可能会发生变化，因此产生的捻度应仅被视为原始值的近似值。

1.1 This test method 2 describes the determination of twist in single spun yarns when only an approximation of the true twist is required. Note 1: For a more accurate method see Test Method D1423 . 1.2 This test method is applicable to spun single yarns in continuous lengths, and also to spun yarns raveled from fabrics, provided specimens at least 200 mm [8 in.] long can be obtained. 1.3 This test method has been found satisfactory for use in determining the approximate twist content in single ring spun yarns of all types and fiber contents, but not in open-end spun yarns. 1.4 This specification shows the values in both inch-pound units and SI units. The “inch-pound” units is the technically correct name for the customary units used in the United States. The “SI” units is the technically corrected name for the system of metric units known as the International System of Units. The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 This test method is used for acceptance testing in the trade for economic reasons even though it is less accurate than the direct method, Test Method D1423 . 5.1.1 If there are differences or practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if their is a statistical bias between them, using competent statistical assistance. As a minimum, the test samples should be used that are as homogeneous as possible, that are drawn from the material from which the disparate test results are obtained, and that are assigned randomly in equal numbers to each laboratory for testing. Other materials with established test values may be used for this purpose. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results must be adjusted in consideration of the known bias. 5.2 The “setting” of twist in some fibers causes excessive contraction when the yarn is retwisted in the reverse direction. Therefore, the number of turns required to bring the specimen back to its original length may be less than the number of turns removed in untwisting. This effect may be partially offset by the use of higher pretensioning loads; but this increases the danger of stretching the yarn. Little information is available on the correct tensions to use for yarns made from different fibers or with different amounts of twist. 5.3 In addition to being less tedious, this test method requires fewer specimens than the direct-counting method and the results may be sufficiently accurate for certain purposes. This test method can be useful in those cases where the main objective is to measure variations from an average value. Another possible application is where a large amount of twist testing is required on yarns of similar type and twist. In this case preliminary tests comparing this method and the direct method could be used to determine the correct pretension. 5.4 Twist has important effects on the physical properties of yarn. Low-twist yarn is lofty and is usually preferred for knitting because of its softness, covering power, and warmth. Increasing the amount of twist causes an increase in yarn strength by increasing fiber cohesion, but as the twist angle increases beyond an optimum point, strength decreases due to a loss in effective fiber contribution. Maximum yarn strength is obtained by inserting a medium amount of twist to obtain an optimum balance between these two opposing forces. High twist produces yarns of high density (“hard” or “wiry”) and high elongation and may improve the abrasion and impact resistance of fabrics. 5.5 The optimum twist for either manufacturing efficiency or physical properties usually increases as staple length decreases. 5.6 The twist in a yarn before it is packaged may be different from that of the yarn after it has been withdrawn from the package because of changes in tension and the effect of the method of withdrawal. Withdraw the yarn from the package in the direction of normal use, either from the side or over-end. If the yarn is withdrawn over-end, a slight increase or decrease in twist will take place, depending upon the direction of the twist in the yarn, the direction of winding on the package, and the length of the turn (or wrap) on the package. Note 2: The difference in twist between unwinding from the side and over-end is 1/π d, where d is the diameter of the package. 4 Thus, for a 25-mm [1-in.] diameter package, the difference would be about 13 tpm or about one third tpi. 5.7 When a yarn is taken from a more complex yarn structure or from a fabric, the resultant twist should be considered only an approximation of the original value because of alterations that may have occurred as a result of the effects of unwinding, handling, and mechanical strains met in processing.