ABSTRACT The propagation velocity of a transverse ultrasonic wave is influenced by the temperature of the testing materials. In other words, it directly affects the accuracy of thickness measurement and flaw detection as well as the validity of the focal law during the high-temperature ultrasonic inspection. For the above reasons, an electromagnetic acoustic transducer (EMAT) was adopted in this study to measure the transverse ultrasonic velocities of several metallic specimens when heated to the temperatures of the order of 700°C. EMAT was particularly favored for use in this study owing to its non-contact and couplant-free characteristics. The reliability of the collected data and experimental stability were verified via the establishment of a high-temperature experimental system as well as analysis of the measurement error and uncertainty. By comparing ferromagnetic and non-ferromagnetic materials using this system, it can be found that the transverse ultrasonic velocity of ferromagnetic materials decreases in a nonlinear “step-like” manner with the temperature. Therefore, results obtained from this study indicates that the velocity–temperature relationship of different materials does not follow the same law. Besides, the curves tested in this study can serve as a ready references to facilitate nondestructive inspections of materials at high temperatures.

中文翻译：

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高温材料中横向超声波速度变化规律的研究

摘要 横向超声波的传播速度受测试材料温度的影响。换言之，它直接影响到高温超声检测中测厚和探伤的准确性以及聚焦规律的有效性。由于上述原因，本研究采用电磁声换能器 (EMAT) 来测量加热到 700°C 左右的温度时几种金属试样的横向超声速度。由于其非接触和无耦合剂的特性，EMAT 特别适合在本研究中使用。通过高温实验系统的建立以及测量误差和不确定度的分析，验证了采集数据的可靠性和实验稳定性。通过使用该系统比较铁磁材料和非铁磁材料，可以发现铁磁材料的横向超声速度随温度呈非线性“阶梯状”下降。因此，从这项研究中获得的结果表明，不同材料的速度-温度关系并不遵循相同的规律。此外，本研究中测试的曲线可以作为现成的参考，以促进材料在高温下的无损检测。从这项研究中获得的结果表明，不同材料的速度-温度关系并不遵循相同的规律。此外，本研究中测试的曲线可以作为现成的参考，以促进材料在高温下的无损检测。从这项研究中获得的结果表明，不同材料的速度-温度关系并不遵循相同的规律。此外，本研究中测试的曲线可以作为现成的参考，以促进材料在高温下的无损检测。