GB785775A - Ultrasonic penetrant methods of flaw detection - Google Patents

Abstract

785,775. Testing physical qualities of materials. SWITZER BROS., Inc. Dec. 9, 1955 [July 27, 1955], No. 35437/55. Class 106 (2). [Also in Group XXXVIII] The method of testing for flaws having surface openings in parts such as forged aluminium fittings, iron castings, ball-bearing races, &c., by applying a penetrant liquid to the surface of the body under test and after superficial removal of the penetrant inspecting the body for the appearance of penetrant which was retained in the flaw, is expedited by the application of ultrasonic vibrations to the body at a frequency to which the body is resonant. The vibrations may be applied at the first stage to assist penetration and/or at the inspection stage to assist in expelling the penetrant. For example, the normal time of immersion in a penetrant may be reduced from 15 minutes to a matter of 10 seconds when vibrations are applied; or a period of ¥ hour standing after drying to allow indications to appear may be accelerated to give full development after 30 seconds of vibration. The frequencies are usually in the range 10 kc/s. to 500 kc/s., but higher or lower frequencies may be used. Piezo-electric transducers are recommended for determining resonant frequencies of articles to be tested, but the more rugged magneto-strictive type are preferred for production testing of mass produced articles whose resonant frequencies are usually below 50 kc/s. If the bodies to be tested are themselves magneto-strictive they may be passed, while immersed in penetrant, through a coil carrying pulses (for example, 30 per second) of current alternating at the resonant frequency of the bodies. Known methods of detecting the penetrant exuding from flaws are utilized, for example, a fluorescent dye may be dissolved in the penetrant liquid, or a finely dispersed pigment may be used. The process may be applied to articles having different resonant frequencies in different portions by transducing the appropriate frequencies in the different parts taking care to avoid fracture in the boundary zones. Specification 684,021 and U.S.A. Specifications 2,259,400 and 2,405,078 are referred to.