The Research On Crack Sizing By PA-SAFT Imaging Technique

Crack quantitative is of great significance to ensure the safe operation of the component. And ultrasound method has obvious advantages for crack sizing. Phased Array Ultrasonic Technology, PAUT, with the advantages of beam adjusted dynamically, well accessibility, high detection efficiency and intuitive defect imaging, become popular in the field of nondestructive testing of crack sizing. But due to the limited focal beam, it is difficult to capture the echo of the crack tip in the blind inspection of cracks. PA-SAFT of Synthetic Aperture Focusing Technology (SAFT) combined with PAUT, can realize space focusing point by point. PA-SAFT can improve the crack height quantitative accuracy and estimate incline angle effective. It helps to accurately determine position of the crack tip, so as to realize precise quantitative for cracks. In this paper, research methods of combination of simulation and experiment are used, compared crack sizing by PAUT and PA-SAFT is conducted for embed and bottom crack in the carbon block of thickness 55.00mm using electronic scanning of 5MHz linear array probe. The main work is as follows:(1) For embed cracks of through wall height 10.00mm,8.00mm,4.00mm,2.00mm and 1.00mm crack sizing is realized by confirming the location of the maximum amplitude of top and bottom tip in the images of PAUT and PA-SAFT. The results showed:The max error absolute value of height sizing by PAUT(focusing depth 35mm) is 0.15mm, the max error absolute value of height sizing by PA-SAFT is 0.02mm for cracks of incline angle 0.00° The max error absolute value of incline angle sizing by PAUT is 12.05°, the max error absolute value of incline angle sizing by PA-SAFT is 4.41° for cracks of incline angle 15.00°,30.00°,45.00°,60.00° and 75.00°(2) For bottom cracks of through wall height 10.00mm,8.00mm,4.00mm,2.00mm and 1.00mm, first of all, in case of cracks of incline 0.00°, against the problem the bottom tip and undersurface aliasing, minimum amplitude method is used for confirming the location of bottom tip to achieve crack quantitative. In the further, for cracks of inclined angle 15.00° 30.00°,45.00°,60.00°and 75.00°, the location of bottom tip is confirmed by-6dB method to achieve incline angle sizing. The results showed:For cracks of incline angle 0.00° the max error absolute value of height sizing by PAUT(focusing depth 55mm) is 0.04mm, PAUT can not sizing crack of height 1.00mm.The max error absolute value of height sizing by PA-SAFT is 0.03mm, and is 0.02mm for crack sizing of height 1.00mm. For cracks of incline angle 15.00°,30.00°,45.00°,60.00° and 75.00°, the max error absolute value of incline angle sizing by PAUT is 4.98°, the max error absolute value of height sizing by PA-SAFT is 3.68°...