Research Of Ultrasonic Phased Array Based On Signal Scattering Characteristics

Ultrasonic phased array offers two key advantages over monolithic transducers. Firstly, the signal is excitated by beam synthesis, a particular array is able to undertake a range of different inspections from a single location. Secondly, most types of array can be used to produce images at each test location. Due to the current phased array has not been adequately consider the impact of the scattering characteristics of different defects on imaging, making the advantages of phased array inspection fail to exert sufficiently.Through the analysis of ultrasonic phased array imaging theory and computer modeling, and according to Doppler production PHASCAN portable ultrasound phased array flaw detector characteristics, phased array inspection probes and sound field model is established, as well as theoretical calculated the sound field of phased array in this paper, in addition, calculated the delay laws when the incident beam are steering, focused or produce a beam, which is focused at a given range and propagated at a specific azimuth angle. Using MATLAB according to the theoretical formula for calculating theory sound field and sound field distribution. CIVA simulation software is used to calculate the radiation sound field of a single or mullti array element, as a basis for the introduction of elliptic defect model, by changing the axial ratio of the ellipse to analog circular, crack or bar defects and research of the effect of defects types and defect size on scattering behavior of ultrasonic signals, later validated by using the laser photoelastic experiment, and then use PHASCAN phased array detector for inspecting the reference block for detecting the signal which contain the defect diffraction signal, using the diffraction characteristics acquired by computer calculated to correct the inspection results and evaluated it according to the defect size measurement error.The results showed that the theortical sound field distribution based on PHASCAN phased array detector calculated by MATLAB agree well with CIVA analogy results. For analog circular defect the critical scatter dimension is 5λ in longitudinal wave and 10λ in shear wave, and exhibit crack defect its critical scatter dimension is 2.5λ in longitudinal wave and 2λ in shear wave, in which the circular defect scattering results calculated coincide with laser photoelastic experiment. Using Doppler production PHASCAN portable ultrasound phased array flaw detector adopt sector scanning and measuring the through hole with diameter 2mm within the depth range of 20~ 40 mm in phased array reference block, the relative size measurement error is fluctuation from 16.5% to 23.5%. ABAQUS software is conducted to simulate the inspection process, compared with the measurement by calculated the path difference between diffracted echo and reflected flaw echo for correction with a relative error of 12% to 14%.This research results provide evidence for improving the detection ability of tiny defects and defect size measurement accuracy in Phased Array inspection.