Application of Hilbert instantaneous spectrum on improved bolt anchoring quality detection

Abstract

Abstract The nondestructive testing technology for bolt anchoring quality based on the acoustic reflection method is developing rapidly. Hilbert transform instantaneous spectrum is frequently used. However, due to the existence of the folding phenomenon in the instantaneous phase, the accurate identification of reflected signal and the effective calculation of the anchorage compactness remain a challenge. The instantaneous frequency curve of the bolt signal is used to overcome the phase folding problem. The instantaneous frequency curve of the signal can help accurately identify the reflected signal from the bolt bottom and the position of the defect, thus accurately calculate the length of the bolt and the position of the defect. According to the analysis of the instantaneous amplitude curve of the signal, the formula for computing the bolt anchorage compactness is derived based on the correlation between the attenuation amplitude ratio of the reflected signal and the bolt anchoring quality. Research results show that difficult problems such as bolt reflection signal identification and anchorage compactness calculation are both effectively solved. The model simulation analyzes and field application examples verify the effectiveness and practicability of the methodology, which provides a robust way for the nondestructive testing of the bolt anchoring quality.

Keywords

• acoustic reflection method
• bolt anchoring quality
• bolt length
• compactness
• Hilbert transform
• instantaneous frequency curve