Research On Sound Field Characteristics And 3D Visualization Of Deep Defects In Low Carbon Steel Based On Ultrasonic Phased Array

The rapid and effective detection of internal defects in key parts of rail train by ultrasonic phased array is very important for the safe operation of train.In this paper,aiming at the complex acoustic characteristics and defect display of deep defects in medium-thick low carbon steel plate,the finite element simulation of phased array sound field is used to optimize the detection parameters.At the same time,the influence of different factors on the propagation of sound field is simulated.The interaction between defects and phased array sound field is further elaborated.Combined with the principle of phased array detection,the phased array probe and defect block are designed and the influence of different factors on the results of deep defect phased array detection are analyzed.Combined with the simulation results,the influence of the sound field mechanism of low carbon steel deep defect on the phased array detection effect is clarified,and the optimization criteria of deep defect detection based on phased array is further clarified.And the three-dimensional visualization of low carbon steel deep defect based on Open GL is realized.The above research has practical significance for the application of ultrasonic phased array detection in rail train.Based on the finite element simulation model of phased array sound field,the effects of different probe parameters on the focused sound field of phased array are studied by analyzing the focused sound field diagram and sound pressure distribution diagram.The results show that the larger the number of array elements and the higher the frequency of array elements have better focal area size,and the larger number of array elements,the lower frequency of array elements,the larger width and gap of array elements have better sound field center.meanwhile,the change of the width of the array element has little effect on the focal area size,while the change of the gap of the array element has no effect on the optimization of the focal area size.At the same time,the influence of different defect factors on the sound field propagation is studied.By analyzing the internal sound field distribution cloud diagrams of different defect models and the voltage waveform diagrams of the transducer components,the propagation direction and energy distribution of the sound wave after reflection at the defects of different shapes are relatively large.The difference is that the defect echo signal and the bottom surface echo signal of the long strip defect model are higher than the round hole defect.The long strip defect has a stronger reflection effect on the phased array sound field in the vertical direction,and the defect echo and bottom echo signals received by the transducer are stronger;the width of the defect affects the diffraction effect of the sound field and the defect.As the width of the defect decreases,the size of the acoustic shadow area increases,and the bottom echo voltage received by the transducer decreases accordingly;different defect spacing affects the reception of the second defect echo,and does not affect the same echo signal on the bottom surface.The change of the defect spacing affects the acoustic reflection and diffraction time of the second defect;The delay algorithm of the excitation signal is different for the depth,and when the focus depth is higher than the defect position,the defect echo signal is weaker,and when the depth is lower than the defect position,the defect echo signal is stronger,but the signal interference effect is greater at the same time.After obtaining the simulation results of ultrasonic phased array defect detection,two kinds of phased array probes with different parameters are designed.The main parameters of the two groups of probes are 64 elements-15 MHz and 32 elements-5MHz respectively,and different wedges are matched.By analyzing the acoustic field sensitivity and resolution under different probe parameters and defect factors,and the phased array detection effect is compared,the acoustic field sensitivity is higher with larger number of elements,lower frequency of elements and larger principal axis aperture,and the acoustic field resolution is higher with larger number of elements,higher frequency of elements and larger principal axis aperture;The phased array sound field has higher detection sensitivity and resolution with more concentrated reflections at the position of defect,and the smaller diffraction effect will receive lower echo signal from the bottom surface,while sound field has better detection effect for larger defects,and the detection sensitivity and resolution of the sound field for small defects can be improved by adjusting the probe parameters.In addition,the phased array detection effect is the best when the focusing depth is close to the defect depth.Finally,the 3D display of the phased array data in the geometric structure is realized based on the 3D database Open GL.The effects of 3D display are clear and intuitive,and the effects of 3D display on different defects are analyzed,the results show that,if the effect of the phased array detection is better,the result of the 3D display is more reliable.