| Reinforced concrete is widely applied in the construction field. The price is low, and the material is easy to obtain. It meet the needs of the present stage of China’s development, so the vast majority of infrastructure are reinforced concrete structures. Although concrete itself is a good durable mat erial, but in harsh environment, such as cold, marine, industrial and alpine climate conditions, there are still many damage cases due to the decrease durability. And steel corrosion is one of the important factors affecting the durability of concrete structure, no matter at home and abroad each year the losses caused by steel corrosion are enormous, so detecting the important part of the structure during the using process can reduce the loss to a certain extent.The traditional steel corrosion detection methods, suc h as physical, electrochemical method are relatively mature, although these methods have various advantages, but there are some unavoidable defects. In this paper, we use ultrasonic guided waves to detect the steel corrosion. This method is not only faster, but also larger detection range, under certain conditions, it can become an on-line monitoring methods.This paper analyzes the ultrasonic guided waves propagating in the rod in a variety of modes, and use MATLAB software to solve each mode dispersion equations by numerical methods to obtain a theoretical speeds of the various modes propagating in the steel. This paper also analyzes the different physical parameters of steel influence the guided wave propagation velocityUsing ANSYS software to establish a piezoelectric ceramic and steel, and apply voltage signal which is modulated by Hanning window at one of the piezoelectric ceramic. This paper set up a two-dimensional model to analysis the process that guided wave propagate in solid. Through simulation we found that with increasing depth of local corrosion, the ratio of reflected wave signal and the first wave signal will increase, while the length of corrosion, the location of the corrosion are also influence the received signal, comparing with received signal without defect we can get the corrosion information. Along with a brief study of the uniform corrosion of steel to analyze the affect the expansion force and interfacial bond strength between steel and concrete in the received voltage signal. From the ANSYS result we find expansion force has little effect for guided wave propagation, but the received signal changes large with the bond strength, so we can see the bonding force between steel and concrete impact the signal greatly.Experiments using NI data acquisition devices, and using LABVIEW to built a platform to control the instrument. Using the platform to produce excitation signals with different frequencies at one of the end of steel, and analyze the receiving voltage signal. Comparing the dispersion curves which are solved by numerical methods in MATLAB and the received voltage signal, we can confirm the authenticity of the numerical solution methods. Selecting 100 KHz as excitation frequency to analyzes the influence of depth, length, and position of corrosion in the received voltage signal, along with a brief analysis of the multi-point corrosion effect in the signal.By comparing the numerical simulation and experimental results, it confirm the possibility to use ultrasonic guided wave testing of steel corrosion. |
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