Research On Crack Height Measurement And Defect Qualitative Of Ultrasonic Phased Array

The vessel and pipeline have the local high stress area due to stress or corrosioneffect. When the stress is accumulated to a certain extent, there will have a fatiguecrack initiation. Fatigue crack usually appear within the workpiece surface and nearsurface.It can lead to fracture or buckling expansion and have serious damage to theequipment safe use. So the bottom opening crack detection is particularly important.This paper first introduces the ultrasonic phased array testing technology, includingthe theory of sound field, detection principle, working mode, the advantages of phasedarray inspection and the trend of phased array testing. The influence of variousparameters on focusing sound field is discussed, on this basis, the optimum value rangeof each parameter is given.The simulation model of ultrasonic phased array and the measuring method ofbottom opening crack height is discussed in detail. The theoretical basis for ultrasonicphased array simulation and experiment has established.In the simulation experiment of inspect and measure the bottom opening of crackheight by ultrasonic phased array relative arrival time technique (RATT), the sound fielddistribution and the defect response is calculated when the beam is deflected differentangle. The best detection angle to measure bottom-break height is extracted in differentcases. When the bottom-break crack is inclined at different angle, the height of crack ismeasured by the best incidence angle in the simulation. The minimum length of crack iscalculated and the corresponding measurement results and the relative error are given.The simulation experiment of measuring bottom-break crack by ultrasonic phased arraysingle point focusing RATT is taked and the result shows that point focusing detectionmodel can improve effectively the measurement accuracy of inspection, but thedetection range is reduced.The height of the artificial cracks in different thickness block is measured byultrasonic phased array absolute arrival time technique (AATT) in test simulation andexperimental measurement. The height of natural crack in weld is also be measured byAATT method. A comparative analysis of experimental results and TOFD measurementresults is conducted in the paper. The results show that the height of bottom break crackcan be measure quantitatively by the AATT method from one side and can achieve thesame accuracy as the conventional TOFD. In this paper, the ability of ultrasonicphased array point focusing on defect positioning and quantitative is also discussed.The welding test block within different kinds of natural defects is detected byultrasonic phased array s-scan in simulation and actual experiment. Through acomparative analysis of simulation results and experimental results, S-scan features ofnatural defects are summarized. There is an improtant reference and guidingsignificance for defect qualitative of ultrasonic phased array s-scan inspection.