Research On Phased Array Ultrasoinc Total Focusing Method Imaging Technique For Wheel Defects

With the rapid development of China’s high-speed rail, people are increasingly concerned about the safety of train travel. Wheel is one of the key components of the train, its inspection and maintenance requirements are also increasing. The development of Wheel detection is trend to improve the accuracy and sensitivity of the defect, and analysis of the defect localization and quantitative.In order to optimize Wheel ultrasonic testing technology, this paper access a large number of phased array ultrasonic and Total Focusing Method literature. Focusing on the theory of total focusing method algorithm and applied it to the Wheel defect detection of location and quantitative. Works are as follows:First of all, by studying the theory of acoustic field. Ultrasonic transducer mathematical model is established, it turns out the rectangular plane ultrasonic transducer acoustic field distribution. Based on the characteristics of the acoustic field distribution lay the foundation for ultrasonic phased imaging.On the basis of the Full Matrix Capture model and total focusing method theory, through simulation and experimental implementation of a single medium total focusing method imaging. Further analysis of the array directivity function improve the quality of defect image in the near field and the depth. While the total focusing method has been applied to process the data created by two-dimensional (2D) array, and the focusing method algorithm based on 2D array probe is established, comparative analysis of the results of the simulation and experiment.Analysis of the propagation characteristics of ultrasonic wave in dual-layered media. According to Snell’s law and Ferrari’s method can find the point of incidence at the refractive interface. This is the dual-layered media total focusing method algorithm, and through the experiment of the calculation model is verified.At last, the dual-layered media total focusing method algorithm is used for wheel defect detection. Proposed a principle that the maximum amplitude to determine the center of defect is giving to locate the defect, and the improved -6dB method is used for defect quantitative. The dual-layered media total focusing method algorithm have advantages compare with sector-scan. Localization and quantitative accuracy are greatly improved.