| 摘要 |
1,203,854. Ultrasonic inspection devices. AUTOMATION INDUSTRIES Inc. 20 May, 1968 [9 June, 1967], No. 23830/68. Headings H4D and H4J. Apparatus for inspecting a workpiece comprises a transducer for transmitting ultrasonic energy obliquely into the workpiece surface, a spaced transducer for receiving ultrasonic energy re-radiated normally to the surface from within the workpiece, and a device for scanning the transducers over the surface. In the Fig. 1 embodiment for inspecting a weld 18 for flaws, receiving transducer 28 and angled transmitting transducers 24, 26 are reciprocated across the weld by motor 42 and mechanism 34, 36, 40 while workpiece 1,6 is driven longitudinally by rollers 37. The transducers and workpiece may be submerged in a liquid couplant or may be in direct contact or coupled by a liquid film. Transducers 24 and 26 are pulsed by transmitter 44 and their angles are adjusted such that shear waves propagate in workpiece 16. Discontinuities in the weld reradiate acoustic energy to transducer 28, whose output is fed via receiver 50 (which may incorporate A.G.C.) and time gate 52 to an oscilloscope or chart recorder 54 (comprising an amplitude threshold circuit) which is scanned synchronously with the transducer reciprocation and workpiece movement to provide a plan position indication of weld flaws. The transducers are piezoelectric and transducer 28 may incorporate an acoustic lens to give a narrow reception beam. Recorder 54 may produce either a positive or a negative record: the latter, in which a dark line recording is interrupted on reception of an acoustic signal by transducer 28, allows monitoring of the operation of the ultrasonic and recording system. In various modifications the transducers may be positioned on both faces of the workpiece, the receiving transducer may be to one side of the transmitting transducers instead of between them, and the transducer scanning may be effected by reciprocating the transducers relative to each other along guides 58, 60. |
