| 摘要 |
FIELD: nondestructive testing; ultrasonic testing. ^ SUBSTANCE: method can be used for determining shapes of defects and spatial position of such defects as cavities, slag inclusions as well as for measurement of thickness of tested objects with complex profile. Ultrasonic oscillations are excited in tested object by piezoelectric converter having wide directional pattern which results to reduction in distortions of acoustic image induced by spread of acoustic wave propagation. When receiving reflected oscillations the receiving piezoelectric converter is disposed at different points on surface of tested object. Then object is divided to local parts, which are judged as local concentrated reflecting element. Reflected signal after being received by any position of receiving piezoelectric converter from any local area have to be shifted in time for value being equal to time of propagation of reflected wave from local area till corresponding position of receiving piezoelectric converter. Then time-shifted signals are summed correspondingly for any local area. The procedures described before repeat for two or more frequency versions for each of which frequencies of acoustic waves being used at ultrasonic test are different. For any frequency version M preliminary images are formed in form of values of amplitudes of sum signals, which correspond to different local areas of tested volume and are defined for different assumed values of speed of wave propagation in material M. Then all pairs of M preliminary images are compared pairwise which images are specified for any frequency version at similar values of speed of propagation. Pair of images is chosen from all the pairs having less differences than others and final acoustic image of tested object is formed in form of half-sum of latter images. ^ EFFECT: improved precision. ^ 2 cl, 3 dwg |
