Simulation of Modified Absolute Arrival Time Technique for Measuring Surface Breaking Cracks

Surface breaking cracks pose great risk to the security of steel structure equipment. It is very important to estimate the height and the orientation of surface breaking cracks accurately for the residual life evaluation of equipment. In this paper, a modified phased array ultrasonic absolute arrival time technique (AATT) for this purpose was proposed. It utilizes the absolute position of the tip diffraction echo and the corner reflection echo in a ultrasonic phased array S-scan image to estimate the crack height and the crack inclination angle. The height and the orientation of the surface breaking cracks was deduced with ray acoustic approximation. Both pencil approximation and Kirchhoff approximation were used to simulate the phased array ultrasonic S-scan image of the surface breaking cracks. The echo arrival time extracted from the S-scan image was used to calculate the height and the orientation of surface breaking cracks with AATT technique. The calculated result agree with the size of pre-set cracks in simulation. Proved that the AATT technique can be applied to measure the size of surface breaking cracks, especially in the testing from single side.