Research On Application Of Ultrasonic Inspection In Large-scale Bridge Concrete Components

With the development of national economy and increasing of the bridge's scale and cost, large-scale bridges are becoming important to the national economy and social life, which are concerned by people for safety, durability, normal function. In order to evaluate reasonably the health status of a bridge, firstly the structure damage exist in bridge must be identified and located, and how to evaluate reasonably the health status of a bridge becomes a current problem to resolve for the engineering construction. Especially in recent years, the research of bridge detection technology is becoming urgent with increasing damages, aging, diseases of the accident for worldwide concrete bridge structural.Ultrasound has lots of advantages, such as, no harmful to humans, light Equipment, low-cost and so on. Using ultrasound imaging to detection the inside defect of concrete, sound waves spread in constant speed when concrete structure has a uniform quality. However, sound waves travel time will increase through or bypass the defect area when defects exist. Based on a single line can not determine the exact location and size of defects, travel time increasing only show that defects may fall on uncertain point of this line. If the cross-line passes the same defect area, then the exact location and size of defects are identified.In recent years, ultrasonic tomography technology has been widely used to concrete structures bridge non-destructive testing, and have achieved good results. Ultrasound tomography imaging method first divided imaging area into grid, which divided imaging area into rectangular units, some ultrasonic launch points are set on one side of detected concrete, some receiving points are set on the opposite side or other side, launch ultrasonic waves point by point on the launch points, then receive on all the receiving points, input the first-arrival travel time into computed tomography imaging software system and calculate, the velocity profile image of measured area will be reconstructed. The image can show accurately and intuitively the internal quality of the concrete. Several different directions rays pass through one unit, so the reconstructed image has a higher detection accuracy.This article describes in detail the basic principles of CT imaging, derives radon transform and its inverse transform formula of mathematical basis for CT technology. Introduces ultrasonic tomography's grid, two types of reconstruction algorithm and the ray tracing method. In this paper, the object of concrete is actually a composite, multi-phase composite system, distribute a wide range complex interface inside, in which the spread of sound waves is more complex than uniform medium. Therefore, the ray tracing in ultrasonic tomography is very important for tomography and forward modeling. The ray-tracing is to calculate and describe the spread-ray path in concrete, its accuracy and speed is a key factor to impact on image quality and efficiency. There are many different ray tracing methods, it is different for various application conditions, computational efficiency and effect of each algorithm, this paper mainly introduces the method of direct ray tracing and linear traveltime interpolation.Experimental part of this article presents the equipment and production of physical model in detail. the equipment SRS64 has many advantages of high precision, high intelligence, multi-channel, high-efficiency. Use magnetostrictive focus, with high-frequency, large energy, power stability, frequency bandwidth, repeatability, time-accurate, aftershocks short, stable performance and vibroseis the advantages of the focus. receive transducer select piezoelectric ceramic transducer with aftershocks short, low Q value, frequency bandwidth, high sensitivity, small diameter, producing simply, low-cost, and can make up into detector arrays, achieve out single launch and receive at the same time, the record has good consistency.Contrast mathematical model and physical model in the experiment, analyze the differences between theory and practice. And then mainly introduces the ability of ultrasound imaging by detecting defects in the four different physical models. compare different observing systems, optimalize the experimental method, the effect of ultrasound imaging will approach the actual situation as far as possible. Finally, this paper introduces concretely the field work, data acquisition, test results and analysis of ultrasound imaging method with a practical engineering example. Through application of ultrasound imaging in practical engineering, use other comprehensive methods to verify, results show that the effect of ultrasound imaging method has good resolution and high efficiency.