| Abstract:Ultrasonic methods are widely used in the non-destructive testing of concrete because they have outstanding advantages in penetrating ability, instruments, operation and testing cost. However, concrete is a strongly heterogeneous solid including aggregates, cracks and porosity. It represents an important but also very challenging object for ultrasonic non-destructive testing methods. So we have to study the ultrasonic wave propagation process systematically for understanding the relationship between acoustic parameters and flaws of concrete.In the present paper the elastodynamic finite integration technique (EFIT) is used to calculate ultrasonic wave propagation because of its suitability for heterogeneous materials. The process of EFIT discretization is described in detail. The effect of internal boundaries in the medium in the sense of changes in the material parameters is automatically handled by the numerical method. Meanwhile, the stress-free boundaries and absorbing boundaries are considered separately in the algorithm. In order to simulate the concrete medium, the concrete is analyzed as a two-phase system consisting of aggregates and mortar matrix. A numerical model is developed to produce the random elliptical aggregate structure and two-dimensional numerical concrete model is built in the paper.In order to investigate the effect of aggregates, flaws of concrete such as cavities, cracks and so on, the simulations of ultrasonic wave propagation in concrete medium are performed by EFIT code. The ultrasonic wave propagation in these models consists of complex mixture of multiple mode conversion and multiple scattering. The paper also shows the complex process of ultrasonic wave propagation in the tendon duct concrete model. Simultaneously, ultrasonic testing using phased array for concrete components is researched. The results of these simulations provide some useful knowledge for ultrasonic data processing and inversion imaging.40pictures,1tables,62references. |
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