Research on acoustic emission characteristics of local corrosion on Q235 steel

To solve the problem of corrosion acoustic emission （AE） source feature extraction and recognition, the AE detection validation and the amplitude-frequency characteristics were derived in theory. The amplitude of AE signal generated by bubble burst is proportional to its radius square and the liquid level, while the AE signal frequency is inversely proportional to the bubble radius. The AE signal amplitude of the steel and the steel corrosion product cracking is proportional to the local stress, and the AE signal frequency is proportional to the crack propagation velocity and inversely proportional to the crack propagation distance. Three Q235 specimens were separately immersed in the solution of 10% FeC13.6H20, 5% CuSOa.5H20 and 10% FeC13.6H20 with 0.01 mol/L HCL. The AE systems with high frequency and low frequency were used to detect the whole corrosion process AE signals. The AE signals of Q235 steel and the steel corrosion products cracking were detected as the verification experiment. The AE signals from different sources could be distinguished by AE hits count and the power spectrum. It is coincident with theoretical analysis. These conclusions have significant guidance for the corrosion detection and evaluation by on-line acoustic emission detecting.

Mechanical behavior of 2G NPR bolt anchored rock samples under static disturbance loading

The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering hazards.The implementation of NPR(negative Poisson's ratio)bolts are capable of controlling large deformations in the surrounding rock effectively.This paper focuses on studying the mechanical properties of the NPR bolt under static disturbance load.The deep nonlinear mechanical experimental system was used to study the mechanical behavior of rock samples with different anchored types(unanchored/PR anchored/2G NPR anchored)under static disturbance load.The whole process of rock samples was taken by high-speed camera to obtain the real-time failure characteristics under static disturbance load.At the same time,the acoustic emission signal was collected to obtain the key characteristic parameters of acoustic emission such as acoustic emission count,energy,and frequency.The deformation at the failure of the samples was calculated and analyzed by digital speckle software.The findings indicate that the failure mode of rock is influenced by different types of anchoring.The peak failure strength of 2G NPR bolt anchored rock samples exhibits an increase of 6.5%when compared to the unanchored rock samples.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 62.16%and 62.90%,respectively.The maximum deformation of bearing capacity exhibits an increase of 59.27%,while the failure time demonstrates a delay of 42.86%.The peak failure strength of the 2G NPR bolt anchored ones under static disturbance load exhibits an increase of 5.94%when compared to the rock anchored by PR(Poisson's ratio)bolt.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 47.16%and 43.86%,respectively.The maximum deformation of the bearing capacity exhibits an increase of 50.43%,and the failure time demonstrates a delay of 32%.After anchoring by 2G NPR bolt,anchoring support effectively reduces the risk of damage caused by static disturbance load.These results demonstrate that the support effect of 2G NPR bolt materials surpasses that of PR bolt.