Evaluation of Bolt-Nut Fastening Condition Using Nonlinear Ultrasonic Components

本研究探讨使用超音波二次谐波成分在质量控制的螺栓紧固结构。本文提出了一种改进的透射法检测螺栓与螺母连接时二次谐波分量的方法。实验中使用了六角头铁螺栓。使用数字扭矩扳手紧固螺栓。二次谐波分量在螺栓紧固前后增加了约10 dB。二次谐波分量的来源是螺栓-螺母螺纹界面的接触声学非线性和螺栓与紧固螺栓的塑性变形。这一结果与我们以前的方法几乎相同。此外，在法向轴向力作用下，二次谐波分量的增加值发生了变化。因此，有效性的新方法检测二次谐波超声分量产生的紧固螺栓被证实。

This study examines the use of ultrasonic second harmonic components in the quality control of bolt-fastened structures. An improved method for detecting the second harmonic components, from a bolt fastened with a nut, using the transmission method is constructed. A hexagon head iron bolt was used in the experiments. The bolt was fastened using a digital torque wrench. The second harmonic component increased by approximately 10 dB before and after the bolt was fastened. The sources of second harmonic components were contact acoustic nonlinearity in the screw thread interfaces of the bolt-nut and were the plastic deformation in the bolt with fastening bolt. This result was almost same compared with previous our method. Moreover, increase values of second harmonic components are changed at the normal axial force. Consequently, usefulness of the novel method for detecting second harmonic ultrasonic components generated from fastened bolt was confirmed.