Patent GB-1192176-A (GB)
Title: Improvements in Testing Apparatus and Methods of Testing
Inventor: KENT DONALD ARTHUR
IPC: G01N29/06
Filed: 1966-10-06
Abstract: 1,192,176. Measuring physical properties, using radiant energy; copying by scanning. IMPERIAL METAL INDUSTRIES (KYNOCH) Ltd. 18 Sept., 1967 [6 Oct., 1966], No. 44710/66. Heading H4D and H4F. In a system for the inspection of an object by the through-transmission and/or pulse-echo method using ultrasonic or X-radiation, radioactive emission or high energy atomic particles, signals representing the energy received from different test locations on the object are recorded on tape together with corresponding location-defining signals and are subsequently used to produce a pictorial representation of the object. For detecting lack of bonding between the tubular steel case 2, rubber liner 3 and solid propellant 4 of a rocket motor 1 the motor is mounted for rotation in water tank 6. Ultrasonic pulse transmitting transducer 8 transmitting/receiving transducer 10 and receiving transducer 9 execute a two-way longitudinal scan of motor 1 between incremental rotations of the motor. In a "through-transmission test channel" (12-21) received signals are amplified at 13, 14, displayed on oscilloscope 12 against a time-base synchronized with the transmitted pulses, passed through logarithmic amplifier 16 to gate 17 which selects only the directtravelling ultrasonic pulse, and fed to peak amplitude detector 19. The peak amplitude signal is applied to amplitude/frequency converter 21 for recording as an F.M. signal on one track of magnetic tape recorder 23, and may also be applied to a pen-recorder 20. In a "pulse-echo test channel" (12a-21a), echo signals are similarly displayed and converted to an F.M. signal for recording on a second track of recorder 23. Digital encoders 24, 33 provide signals indicative of the longitudinal position of transducers 8, 9, 10 and rotational position of motor 1, i.e. provide position coordinates of the motor region being inspected at any instant. The co-ordinates are recorded on further tracks of recorder 23, together with a timing signal from clock 38, are converted to decimal form for display on digital indicators 30, 36, and are applied to computer 27 for automatic transducer scanning according to a predetermined programme. Recorded data is played back at 39. Circuits 41, 42, 43 reconstitute the position co-ordinate data as analogue voltages for displacing the beam of oscilloscope 44 to a position on the screen corresponding to a test region on the motor 1. In a "through-transmission" signal channel, a count representing the frequency of the through-transmission F.M. signal (e.g. representing the received acoustic signal level in decibels) is routed to counter 50 by gates 47, 48, 49 and interval counter 46. This level count is compared at 51 with a pre-set level count in counter 52 and if greater a brightness-modulation signal is passed to oscilloaope 44. A pictorial representation of the motor 1 is thus built up point by point and is recorded by a camera 45. Further representations can be obtained for other pre-set level counts in counter 52. Representations for the "pulse-echo" inspection are similarly derived using a second channel comprising pre-set level counter 59, counter 57, count comparator 58 and further oscilloscope and camera units 54, 55; alternatively this second channel may be used with the "throughtransmission" channel to provide a single representation displaying only those signal levels which lie between two pre-set levels. In a modification the pre-set level feature is omitted and the oscilloscope provides a full grey-scale representation of the motor 1. In a further modification the pre-set level is varied according to a predetermined programme, during the build-up of the pictorial representation, so that for any test region of the motor it equals a corresponding reference value for the particular motor type: the representation thus displays only those signal levels differing from the reference values.