Phased Array Acoustic Propagation Law And Its Application In Defect Quantitative Evaluation

Phased array is one of the most advanced technologies in the nondestructive testing field, which plays a vital role in the aerospace, pressure containers, ships and other fields for its special beam focusing characteristics, fast scan ability and the advantages of clear and intuitionistic imaging results. For detection, in addition the location of the defects, quantitative the size of the defect is also wanted accurately, and even the type of defect and so on. Unfortunately, the phased array ultrasonic technology can only be done on defect location, rather than do quantitative evaluation of defect, which greatly limits the popularization and application so far.This article premised on the special beam focusing characteristics of phased array ultrasonic technology, studied the propagation of sound waves in the cross-drilled hole cavity and quantitative evaluation of defect by regularity. And then, the factors affecting the effect of quantitative evaluation of defect are analyzed.In the first place, this paper has carried on the theoretical research on phased array technology, analyzed the main technical points of the linear array probe radiation sound field, and summarized the domestic and foreign specifications and standards of ultrasonic phased array technology. Based on beam focusing conditions, Acoustic waveform transformation is taken place during propagation in the cross-drilled hole cavity and produces climb wave, phased array can accept and identify climb echo wave radiation. A method for quantitative evaluation of defect is put forward by cavity crawl wave.In the next place, test block with cross-drilled hole cavity is designed and manufacture in the optical glass is analyzed in the method of a dynamic photoelastic system. Transmission of sound waves in the cross-drilled hole cavity, reflection, diffraction and scattering is analyzed. Creeping wave is discovered and the propagation law of creeping wave and spectrum characteristic is also analyzed. Based on dynamic photoelastic experiment results, simplified mathematical model of quantitative evaluation of defect and quantitative process are proposed.Finally, taking the reference of block geometry size CSK- IIIA, the block size respectively Ф1 mm, Ф2 mm, Ф3 mm,Ф 4 mm and the size of Ф0.8 mm ~Ф4.8 mm, tolerance for Ф0.2 mm arithmetic horizontal hole are designed and manufactured. All the cross-drilled holes are quantitative.On the basis of the quantitative results, influencing factors such as test parameters, the state of the defect in the process of experiment and test conditions are analyzed, and the solution are put forward.The results show that the beam focusing characteristics of phased array can improve the utilization rate of sound waves on the ultrasonic phased array testing conditions, combined with the defects of sound wave diffraction effect, defect size can be quantified by the spread laws of sound waves on the cross-drilled hole cavity. For aperture within 3 wave length horizontal hole, quantitative error within 5%, and the method of minimum defect size for quantitative is Φ 1 mm, but this is not the sensitivity limit of the climb echo wave radiation quantitative. The defect size in the work piece can be measured by the method quickly and effectively, which provides a new method of quantitative evaluation phased array ultrasonic technology.