Acoustic Detection Method In Defect Of Concrete Structure

Acoustic detection method is a traditional nondestructive testing, which can detect the defect of concrete structure, so has attracted people's great attention. Firstly, we introduce the backgrounds and the current research situations of concrete detection technology, particularly, the forward and inverse methods usually used in acoustic detection.Secondly, we establish a forward model of concrete structure, and use a acoustic equation, which is a simplified form of elastic wave equation, to simulate the spread of wave. Considering the characteristics of concrete structure, we use Neumann boundary and initial condition, and apply finite-difference method to different defect models in the forward simulation. The result presents that finite-difference method is effective in the detection of defects in concrete structure, which means the forward method is totally feasible to detect the defects in concrete structure.Thirdly, we consider the same equation in chapter two. Noticing that the forward model with Neumann boundary condition has strong edge reflection, while absorbing boundary condition can effectively eliminate the edge reflection, we establish a forward model with absorbing boundary condition, and then simulate the forward by finite-difference method. The simulation results show that the model with absorbing boundary condition is better than the model with Neumann boundary condition in detecting the defects in concrete structure.At last, by analyzing the features of concrete, we establish the mixed regularization on the basis of total variation regularization and Tikhonov regularization. We choose a regular model with absorbing boundary condition, and use it to inverse the change of flow. The result displays that to apply the mixed regularization to inverse the change of defect is feasible.