Xiuyan Wang

Quality inspection of highway guardrail posts partly embedded based on longitudinal guided waves technology

The guardrail is one of the most important attachments in the highway. The compactness of the soil around it, called as embedded quality, determines the crashworthiness performance of the guardrails. Unqualified guardrail posts can not avoid severe accidents happen. But there are not efficient nondestructive detecting methods until now. So we research on the applications of ultrasonic guided waves technology to inspect guardrail post length and embedded quality. For cylindrical guardrail posts, ultrasonic guided waves can be used for their length measurement and evaluation of embedded quality. In this paper, the effect of the parameters of soil including density, the velocities of longitudinal and shear waves on propagation characteristics of longitudinal guided waves modes is analyzed and verified experimentally. It indicates the change of soil characteristics have no effect on group velocity of L(0,2) mode in the frequency range from 160kHz to 270kHz and it will convenient to the length measurement of guardrail post with different embedded conditions. However, the attenuation of the same L(0,2) mode increases monotonously with increasing soil compactness. As a result, L(0,2) mode in the frequency range from 160kHz to 270kHz can be used to evaluate embedded quality of guardrail post to improve the safety of guardrails in the highway.

Propagation characteristics of ultrasonic guided waves in bolts embedded in soil

The treatment of a bolt embedded in soil is simplified to the model of a rod embedded in an infinite medium. The dispersion curves of the model are calculated. Propagation characteristics of longitudinal modes in a free bolt and a bolt embedded in soil are studied. The longitudinal mode L(0,1) in a bolt embedded in soil in the frequency range from 40kHz to 90kHz the displacement of the profile is simple, which makes it easy to be excited. Its attenuation is the smallest in all modes, and its energy velocity is the fastest. This indicates that the longitudinal mode L(0,1) can be used for the inspection of a bolt embedded in soil. At the same time, the experiments on a 2 m long bolt embedded in soil, inspected by using ultrasonic guided wave have been carried out. The results of the experiment show, that the longitudinal mode L(0,1) in the frequency range from 40kHz to 90kHz is suitable for the inspection of a bolt embedded in soil.

The Characterization of Guided Waves on Hollow Cylinder From Non-Axisymmetric End Loading

Ultrasonic guided waves are used for the rapid testing of a steel pipe (O.D 70 mm, I.D 63 mm, 2544 mm long). The non-axisymmetric transducer ring (arc) is put on one end of the pipe to excite and receive the guided wave in the pipe. An artificial hole of 1 mm diameter can not be found by conventional axisymmetric end loading transducer. However, the non-axisymmetric transducer ring (arc), compared with the axisymmetric transducer ring, is very sensitive to the artificial hole when The middle point (MP) of the transducer arcs coincided with the center of the artificial hole on the cross section of the pipe. The results show that the non-axisymmetric end loading technology can locate the crack or defect on the pipe not only in the axial direction but also in the circumferential direction.Copyright