Quantitative Study On Ultrasonic Evaluation Of Flaws In The Concrete

Concrete is the most common building materials, ultrasonic nondestructive testing technology can quickly and easily diagnose the quality of concrete structure. So in recent years, theories of wave propagation in inhomogeneous damaged solid media the inversion method was more discussed. Elastic wave passing the damaged concrete medium, its acoustic parameters, such as velocity, waveform, amplitude, phase, polarization and the structure of spectrum etc, will be changed ,that contains abundant information. How to make full use of these information, quantitatively judging concrete damage status and greatly reducing the misjudgment of project measure are the key problem to Urgently to be solved.Firstly, this paper expounds the principle that the ultrasonic judge concrete structure quality and the main criterions and methods, and introduced the specific application of the ultrasonic detection in engineering.Secondly, the theories of wave propagation in inhomogeneous damaged solid media are introduced. According to its characteristics and reflection and projection coefficient among different medium boundary surface, the continuously inhomogeneous media is approximately treated as homogeneous during progress of calculation, and with the transformational coefficient among layers and Fourier transform, the response of each corresponding frequency is a gained. At last, using of inverse Fourier transform, the result is transmitted to time and the solution of transitory wave propagation is gained.On the basis of the incidence and received wave response, the properties of media are inversed. Using Newton iterative method at the course of inversion, the nonlinear equations is transformed into linear equations, and then Tikhonov's regularization method solved linear ill-posed problems. Finally, L-curve method is used to fix on regularization parameter in regularization and will get good results to be identical with actual value.Therefore, this research provides a theoretical basis for the engineering application that ultrasonic test concrete structure internal defects. Then, Using the improved PSD criterion and velocity comprehensively evaluated concrete internal defect.