An Evaluative Research Of Seam Welding Based On Ultrasonic Signal

Ultrasonic testing is one of the most commonly nondestructive testing methods, its main principle is based on the characteristic of ultrasonic wave propagation in the specimen. Using the ultrasonic propagation characteristics in order to evaluating the specimen itself or its internal defects and the features of defect. Phased array and TOFD (Time of Flight Diffraction) testing, as the most advanced ultrasonic testing method in the world, were introduced into our country and initial effect is achieved. But these two technologies are still in the stage of learning of equipment technology and popularization. It used finite element numerical method to simulation the weld detection by phased array and TOFD testing in this paper. That is not only help the popularization of these two technologies but also help to prove the limitation in weld inspection by TOFD method. Numerical simulation is an attempt to be used as an auxiliary judgment method in weld defect detection.In the researching of modeling numerical model for ultrasonic testing by finite element method, modeling ultrasonic probe, wedge and tested specimen respectively, which are three main parts of ultrasonic testing system. Simulated a specimen model without defect in order to make sure of the propagation process of all kinds waves conform to the laws of physics. Using pulse echo method to detecting a specimen with defects and establish the corresponding numerical model. Compared with the experimental result and simulation result, it can be found that the amplitude of simulation result is not accurate enough, that brings a large of limitations for application of numerical simulation in the practical. However, the echo time of simulation results is very accurate. That indicate numerical simulation can be used in some ultrasonic testing method, such as TOFD method, which must be avoid the measurement of amplitude but can give defect quantitative by the wave propagation time.Established a finite element numerical model of TOFD testing by huygens principle. Made a series of artificial defects detection experiment by TOFD method and compared with the experiment results and the simulation results. Those two kinds of result correspond well, so it is feasible to use numerical simulation as an auxiliary judgment method in TOFD testing, and then the numerical simulation technique can be introduced to improve weaknesses of TOFD testing in practice. Established vertical or longitudinal arrangement natural defect model by finite element method after categorizing natural defect model of weld zone, the simulation results and the experimental results correspond well. Therefore, it is feasible and effective to use numerical simulation as an auxiliary judgment method in the defect detection of weld zone by TOFD method.The finite element numerical simulations of ultrasonic testing have been researched in this paper. The numerical simulation is used as an auxiliary judgment method in the defect detection of weld zone by TOFD method. The research results provide a new method for defect judgment of the ultrasonic testing for weld zone.