Studies of Diffraction Methods of Ultrasonic Testing Applied for Revealing Artificial Defects Simulating Fractured Oxide Films in a Friction Stir Weld

Agglomerations of oxide films are some of the typical defects of friction stir welding. The structure of such defects and their small opening do not allow finding them using the conventional ultrasonic nondestructive testing methods (in particular, by the pulse-echo technique), among other things because of their low reflectivity. We have proposed a technique of artificial introduction of oxide films into a welded joint. We have shown that, to reveal such defects, it is promising to use the diffraction methods of ultrasonic nondestructive testing. The diffraction methods make it possible to detect signals from defects with minimum opening as well as from defects with a partially metallic bonding, which are semitransparent to ultrasonic waves and revealing of which is impossible using other methods of ultrasonic testing, in particular, the pulse-echo technique, along with X-ray testing.