Numerical Simulation And Application Research Of The Propagation Rule Of Untrasonic Through The Concrete

The basic acoustic parameters of wave and the basic theory of wave propagation are introduced, the specific of ultrasonic propagation in concrete was analyzed, with elastic modulus of the definition of damage degree is quoted to describe the damage of concrete, several concrete damaged modulus for ultrasonic transmission are puts forward.In order to investigate the rule of pulse wave propagate in concrete. Firstly, the damage concrete is approximately treated as homogeneous, and the wave motion equation is solved by boundary and continuous conditions between two layers. Then, as for the harmonic wave propagation in inhomogeneous zone, reflective coefficient and transmission coefficient at the interface are gained, and transmission array of wave propagation is deduced in layered media. Based on transmission array, the response is obtained. Eventually, by using Fourier transform, and on the base of solutions of steady wave propagation, the response of each corresponding frequency is gained. Then, using of inverse Fourier transform, the result is transmitted to time and the solution of pulse wave propagation is gained. The attenuation of concrete is considered in the numerical simulation of pulse wave field, taking four kinds of concrete damaged modulus represents different internal defects as example. A series of results can accord with engineering practice such as the amplitude of transmitted wave is lower then the amplitude of incident wave, the phase spectrum of each harmonic wave change greatly, and there is great difference between each frequency, the wave propagation time increases with the damage rises, etc.In application, considering the superposition of wave, the ultrasonic transmission method is simulated by numerical method, bases for the principle and identifying rule of acoustic transmission method of pile foundation. Acoustic transmission method can only determine the range and position of concrete defects, then"damage degree"identifying rule is introduced. Firstly, compare the damage degree of each section with the critical value by using numerical method. As for abnormal points, Selection of concrete damaged modulus according to shadow method, and the extreme value of damage-level function are calculated. Then the serious degree of defects is estimated. Eventually, by example of engineering test of the suggested method, and compare with the PSD method, show that the"damage degree"identifying rule is available, and not likely occur missed judgment.