Research On Ultrasonic Phased Array Detection And TFM Imaging Based On Finite Element Method

Phased-array ultrasonic technology is a hot topic in the field of Nondestructive testing.Research on ultrasonic sound field and imaging of phased-array technology is a critical part in promoting the application of phased-array technology in industrial testing.As the most common structural steel,Q235 steel is widely used in construction engineering,large railway Bridges,pressure vessels manufacturing and other fields due to its good toughness,strength and weldability.Therefore,it is of great importance to study the detection of Q235 steel.In this paper,the acoustic field and signal analysis of the hole defects and weld defects at different depths of 30mm-thick Q235 steel plate were studied based on the principle of phased array through the combination of ultrasonic phased array finite element simulation and experiment,and TFM imaging was studied based on a 30mm-thick Q235 steel plate.The main research contents and results are as follows:(1)Established a phased array beam stacking multiple line model based on principle of phased array and the Rayleigh integral method.The probe parameters of phased-array detection model,such as array width and spacing,were optimized by analyzing the characteristics of phased-array focusing sound field.Using the optimized probe parameters,the simplified b-scan test blockwas modeled by finite element method,and the sound field was visualized in the phased array detection process.The finite element model was verified by experiments,and the defect positioning error and simulation error detected by experiments were 2.26%.(2)The hole defects and weld defects at different depths in Q235 structural steel were analyzed by simulation and experiment through the finite element model after parameter optimization.The experiment is not ideal for defect detection in the near field,but in the simulation process,the defect identification in the near field can be realized by adding a fixed displacement constraint between the elements.The area defects of 0.5mm and 1mm high on the end face of the object can not be detected by the experimental equipment,while the simulation can identify the area defects of 1mm.(3)The codes of TFM imaging were written and the reconstruction of the fully focused imaging region was improved based on the principle of TFM of phased array ultrasonic.A fully focused phased array detection model was established to conduct a fully focused imaging of the analog signal based on a 30mm-thick Q235 steel plate.The positioning error of the defect was within 1%,and the precise quantification of the defect was achieved.The result was verified by experiments.