1.1 本规程涵盖了使用超声波脉冲回波技术测量螺栓长度变化的程序。 1.2 该程序通常适用于公称直径为6.3 mm或以上、有效长径比为2:1或更大的金属螺栓连接。 1.3 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.4 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。 1.5 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 所述技术用于测量紧固件长度的变化。这种测量是从试样的一端进行的，不需要接触后表面。 5.2 超声波脉冲回波技术用于监测紧固件长度的变化，并作为工业质量控制的工具。应用包括涡轮机、石化压力容器、飞机、汽车制造、核工业内的一般螺栓连接、结构钢连接和实验室测试中使用的紧固件。

1.1 This practice covers a procedure for measuring changes in length of threaded bolts using the ultrasonic pulse-echo technique. 1.2 This procedure is normally intended for metal bolting 6.3 mm or more in nominal diameter with effective length-to-diameter ratios of 2:1 or greater. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 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. 1.5 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 The techniques described provide for the measurement of change in length of a fastener. Such measurements are made from one end of the specimen without requiring access to the rear surface. 5.2 The Ultrasonic Pulse Echo technique is used to monitor changes in length of fasteners and as a tool for industrial quality control. Applications include fasteners used in turbines, petrochemical pressure vessels, aircraft, automotive manufacturing, general bolting within the nuclear industry, structural steel connections, and laboratory testing.