超声法是无损检测在役油气管道受力状态的有效方法，能够准确测出管道危险点的应力值，对判断变形管段是否处于安全状态有重大的工程意义。超声法属于敏感性测试技术，其影响因素主要有温度和管道曲面。基于声弹性效应，理论上分析了温度对零应力试件下LCR波（临界折射纵波）飞行时间t₀的影响机理，并推导出修正公式；分析了管道曲面耦合状态对测量结果的影响，提出了根据管道曲率半径修正应力系数的方法。利用自主开发的超声应力测量装置，通过变温试验和管道打压试验来验证修正方法。结果显示：零应力试件下LCR波飞行时间与温度关系的理论推导公式和试验拟合公式有很好的一致性；超声法所测环向应力值修正后与应变法测量值在结果和分布规律上都一致。结果可为使用超声法高精度地测试管道应力提供有效的支撑。

Ultrasonic method, an effective way to measure on-line stress on oil and gas pipelines in nondestructive testing field, can take an accurate measurement of stress on the dangerous point. It has a significant influence on the safety of operating of deformed pipe sections. The accuracy of ultrasonic method, a kind of sensitivity testing techniques, is mainly affected by ambient temperature and the curvature of pipelines. Based on acoustic elastic theory, we first analyze the influence of temperature on LCR time-of-flight t₀ in free stress specimens and propose modified formulas. Then, the influence of the curved surface coupling state on the measurement is analyzed and the method of stress coefficient correction based on radius of curvature of pipeline is proposed. The theoretic correction model has been verified by temperature and pipe pressing varying experiments on an independently developed experimental platform of LCR waves stress measurement. The results show that the theoretically deduced formula of the relationships between the time of flight of LCR waves and temperature are basically consistent with the experimental fitting formula of that in stress-free specimens. In terms of result and distribution trend of measured circumferential stress value, ultrasonic method is consistent with strain method after stress coefficient is corrected based on radius of curvature of pipes. The findings in this paper effectively improve the accuracy and reliability of ultrasonic method of measuring pipe stress.