Research On Anchor Defect Detection Of Anchor Rod Based On Time Inversion Guided Wave

Anchors are commonly used in industries such as mines,tunnels,railways and urban construction.In the long-term work stress,various defects and wear will inevitably occur on the anchor,which will cause the safety of the project to decrease.And the regular inspection of the anchor rod is required.The advantages of ultrasonic technology to detect defects of the anchor in engineering have the characteristics of long detection distance,high efficiency and low engineering cost.It can be widely used in the field of practical engineering detection.In this paper,by means of the theoretical analysis,numerical simulation and experimental verification methods.The method of time-reversed guided waves is used to study the defects of anchors.The main contents are as follows:The finite element simulation software ABAQUS was used to detect the circumferential defects of the anchor rod and the compactness defects of the anchoring system.The simulation results show that compared with the direct guided wave detection,the signal of time-reversed guided wave can detect smaller defects.For the time-reversed waveform detection,the time-window length of the echo of the intercepted defect signal is important factors affecting the detection capability of time-reversed guided waves.The variation of the damage ratio of the anchor defect with the depth,width and number of defects was studied.The variation of the damage ratio of the anchor defect with the density of the anchor and the type of the defect was studied.An experimental platform for detecting the anchor bolting system using ultrasonic guided wave method was built.The experiments verified that time-reversed guided waves can significantly improve the ability of detecting the anchor defects,and can detect smaller defects.The variation of the anchor defects with different depths,widths and different time-window lengths are obtained.The variation of anchor defects with different densities are obtained.The matching and tracking algorithm based on the excitation waveform was used to decompose and reconstruct the single-defect and double-defect echo signals of the anchor.The results show that single and double defects can be distinguished according to the difference in sign after the waveform signal is decomposed and reconstructed.The interval between two atoms reflects the width of the defect of the single defect and the distance between double defects.