Defect Classification and Imaging with Phase Array Techniques

The use of arrays and the possibility of electronic beam steering, focusing and side lobe suppression allows a better defect classification and reconstruction of defective areas in work pieces, components and industrial plants. Because of synthesizing a large sector by a narrm'i ultrasonic beam, the advantage of a narrow beam for oood signal/noise ratio is combined with the advantage of a broad beam for good detectability of unfavorable orientations of flaws. A Fortran program has been written for an equidistant or nonequidistant linear array with the arbitrary choice of amplitude and phase of each element. For shear wave excitation, the shear wave point characteristic of a point source is implemented. The phased array technique has been used for distinction between cracks and voluminous flaws and for the destination of flaw inclination and surface curvature. Three evaluation methods can be used: interpretation of the sector display; generation of compound-scan amplitude locus curves, and flaw imaging by superposition of all sector scans on a storage display. The experimental results show that the arrays are a powerful tool in increasing the reliability of nondestructive testing methods.