Research On The Detection Of Damage And Interior Defects In Concrete By Means Of Ultrasonic

Two parts of content are studied in this dissertation.(1) Experiments are studied on the damage and fracture characteristics of concrete by means of normal Ultrasonic technology.The applications of Ultrasonic in concrete are summarized, and some kinds of testing methods that researched on the damage of concrete are compared. The relations between Ultrasonic parameters and damage evolution are obtained by test, which include cube and prism specimens with different w/c ratios and notched concrete beams with different depth, and the mechanic of concrete destruction is testified. Finally, start from the testing results, the relation between the changing loads and damage gene that based on the Ultrasonic parameters is discussed. The coupling relational expression that it is between ultrasonic parameters and elastic modulus, stress or strain are relate to the ratio of w/c, the shape of specimens, measure position, the magnitude of loads. And the changes of Ultrasonic parameters are utilized to judge the cracking load of notched beams.(2) Ultrasonic CT technology and its applications on detecting interior defects of concrete are studied.Considering velocity in concrete distributes randomly and the interior defects have regular shapes, a ray-tracing method is proposed, which combines the Snell principle with the second ray-tracing technology, and it is apply to simulated several common models of defects in concrete. For inversion algorithms, the extending Kalman filtering theory and the iterative reconstruction algorithms including ART and SIRT are compared by computerized model tests, and the characteristics of three kinds of inversion algorithms are analyzed in theory; On condition of different defect velocity, the stability of three kinds of inversion algorithms for ray model and line model are analyzed, and the factors that affect the inversion precision of extending Kalman filtering theory are discussed in detail. All of these are realized in programs that written in VB. Finally, the results of Ultrasonic CT that applied on the interior defects test in concrete are verified by model tests of preparing specimens.