US2736193A - Ultrasonic inspection of sail joints - Google Patents

Description

Feb 28. 1956 H. a VAN VALKENBURG ErAL 2,736,193

ULTRASONIC INSPECTION 0F RAIL JOINTS Filed July 2. 1953 I 2m-w1 L27 i 26 j v 25 Ill 60M Y A 24 MSWI# A, 26 swsfp I GMM/#MR 2,736,193 Patented Feb. 28, 1958 ULTRASONlC INSPECTION F RAIL IOINTS Howard E. Van Valkenburg, Candlewood Isle, and Raymond E. Sansoni, Bethel, Conn., assignors to Sperry rortilncts, Inc., Danbury, Conn., a corporation of New Application Italy 2, i953, Serial No. 365,632

2 Claims. (C1. 'I3-67) This invention relates to the ultrasonic inspection of rail joints. In such inspeaion, ultrasonic beams are pen'- odically transmitted in to the rail through the head thereof, and if there are internal defects, the beams are reilected by the retlecting mrfaces of such defect back to the transmitting point where they are caused to opcrate suitable indicating means. A problem in connec tion with such testing arises by reason of the fact that the rail joints are held togethrr by mechanisms which comprise angle bars which are bolted to the rail by bolts passing through the angle bars and through bolt holes in the rail ends. Obviomly the bolt holes constitute reflecting surfaces in a manner similar to a defect, and in order that such bolt hole indications shall not be received and therefore shall not complicate the indicated defects, it has been the practice heretofore to provide gating means which gated out from the indicating means the passage of the ultrasonic beams through a longitudinal strip of rail joint in which the bolt holes are located. Thus while the bolt holes were not indicated, it was also the case that bolt hole cracks radiating from the bolt holes to a length of as much as one-half inch were also gated out, and therefore remained undetected. bolt hole cracks are defects which it is desirable to detect, it is the principal object of this invention to provide a means whereby sach bolt hole cracks may be detected while at the same time gating out the indications which would otherwise be caused by the bolt holes themselves.

Further objects and advantages of this invention will become apparent in the following detailed description thereof.

In the accompanying drawings,

Fig. l s an assembly including a block wiring diagram, showing one form of this invention.

Fig. 2 is a side elevation, largely diagrammatic, of a portion of a rail joint and a graph in relation thereto.

Referring to Fig. 1 of the drawings, the invention is shown as applied to the detection of defects in a rail joint indicated generally at I and comprising the rail ends and 11 which are adagcd to be joined by joint bars, not shown, and fixed to the rail ends by bolts, not shown, extending through bolt holes 12 in the rai ends. For the ultrasonic testing of such rail joints there may be provided an electro-acoustic transducer 15 which may take the form of a piezo-electric element sisch as a quartz crystal 16, preferably moonted so as to transmit vibrations into the rail ends at an angle. The electro-acoustic transducer l5 is adapted to be periodically energized by means of a synchronizet 2d which is energized periodically from a suitable source of energy sach as 60-cycle A. C., and said synchroniser periodically trips a pulse generator 21 to generate wave trains of relatively high frequency which are applied to the transducer 15 which transforms the electric vibrations into trchanical vibrations and transmits such wave trains of ultrasonic vibrations into the rail through the rail head. The wave trains travelthroughthenlfromtoptobottom, and if a reflecting surface such as an internal defect D is ert- Since countered, the were train will be reected back to the transducer which will convert such rellected ultrasonic wave train into an electric voltage which after being suitably amplified by an amplier 22 may be applied to the vertical plates 23 of an oscilloscope 24 to deect the sweep 25 which is generated between horizontal plat-:s 26 by a sweep generator 27 which is energized by the synchronizer 2li in synchronism with the generated wave trains.

Referring to Pig. 2, it will be seen that when the: transmitted beam strikes a bolt hole 12 such bolt hole will reflect the transmitted beam back to the transduc v 15 in the same manner as the defect D, and this w occur at every bolt hole throughout the rail joint regiert which is being tested. It is obvious therefore that the sweep 2S on the oscilloscope will show a large number of indications, similar to the indication of a defect, where in fact no defect exists. Therefore as stated in the introduction hereto, it has been customary to gate out all indications which would be caused by reflections of the wave train in the region between the dot and dash lines 30. While this resulted in eliminating the indications of the bolt holes on the indicator, it also resulted in bolt hole cracks, such as indicated at 3l and which lie within said gated-out area 30, escaping detection. It is desirable to detect such bolt hole cracks since they constitute true defects in the rail joint area.

ln order that boit hole cracks of the type described above may be detected, there is provided the following arrangement whereby instead of gating out an entire longitudinal section 30 of the rail, there is gated-out only the bolt holes themselves while the portion of the section 30 lying between bolt holes is rendered sensitive to de tection.

For this purpose there is provided the additional circuitry disclosed in Fig. l, which comprises a bolt hole gate generator 40 adapted to be periodically energized from synchronizer 2t) n synchronism with the pulse gen erator and sweep generator to cause said bolt hole generator to apply a pulse to a coincidence gate circuit 4L Since only the region 30 is to be rendered sensitive to detection, the bolt hole gate generator does not start to generate a signal gate voltage untilfthe transmitted pulse has traveled down to the region 30. By this time the voltage generated by the transmitted pulse, which is of relatively short duration, has terminated. In order to render coincidence gate circuit 41 effective it is essential that an additional pulse be received from the output of amplifier 22. Such a condition exists when the transmitted pulse first strikes a bolt hole 12. At this point the coincidence gare circuit 4l is rendered conductive so that further pulses from the output of amplifier 22 can pass through the coincidence gate circuit and operate a suitable indicator. However, it is not desired that any output from amplifier 22 shall pass through gate circuit 41 until the transducer 15, moving in the direction of the arrow A, nses the transmitted pulses to pass the bolt hole 12. Therefore the output of gate circuit 41 is fed into a delay gate generator 45 whose delay may be ,Y adjusted to correspond to the time that it takes the transducer 1S to move along the rail head a distance corresponding to the diameter of the bolt hole. As soon as this distance has been traversed the delay gate generator-r 45 enables any signals from amplifier 22 passing through coincidence gate crcait 41 to venergize suitable indicating means. Therefore at the end of the delay the signals passing through concidence gate circuit 41 from the amplifier 22 will energize a relay 46 to close contac 47 which closes the circuit to an indicating device which; may be a recorder 48 or a warning device 49, or bode Y as shown. The delay gate generator 45 is timed so that ap'szevnaaV y .t

once it energizes relay 46 it will maintain the relay energized for the time interval T (see ygraph in Fig. 2) which begins just after the transmitted beam has passed a bolt hole and ends just before the transmitted beam is about to strike the succeeding bolt hole. Therefore if a bolt hole crack such as crack 31 occurs, it will reect the transmitted beam sometime during the interval T and the indication in the form of a signal voltage corning out of amplifier 22 will pass through coincidence gate circuit 4l, delay gate generator 45, contacts 47 of relay 46, and operate the indicating means 48, 49.

Since the time T is a function of the rate of movement of the transducer 15, the delay interval of the delay gate generator 4S may be made a function of such rate of movement, as for instance by causing the movement of the transducer IS to actuate a voltage generator 50 to apply a biasing voltage to the gate generator. The voltage generator 50 may be moved by the movement of the transducer l5, or in the case where the transducer is mounted on a carriage the generator 50 may be driven from the carriage wheels.

Having described our invention, what we claim and desire to secure by Letters Patent is:

l. ln a rail flaw detector mechanism, said rails having bolt holes in the joint areas, means for detecting cracks originating at the bolt holes, said means comprising means movable relative to the rail for periodically transmitting ultrasonic wave trains into the rail and receiving reections from reliecting surfaces in the rail, said bolt holes forming reflecting surfaces. indicating means normally 30 2,527,986

maintained ineffective, a bolt hole gate generator adapted to be energized periodically in synchronism witbl'said wave train transmitting Ameans to generate a signal gate generating a signal voltage after a predetermined delay corresponding to the time that the transmitting and receiving means travels past the bolt hole, said delayed signal gate voltage continuing for a time corresponding to the travel oi the transmitting and receiving means between bolt holes, and means whereby the signal voltage from the delay gate generator renders said indicating means effective.

2. A device as specified in claim l, in which means are provided for generating a voltage which is a function of the rate of movement of the transmitting means, and means whereby said last-named voltage is applied to said delay gate generator to vary the duration of the delay Vperiod inversely as the rate of movement of the trans mitting and receiving means.

References Cited in the file of this patent UNITED STATES PATENTS 2,280,226 Firestone Apr. 2l, 1942 Carlin Oct. 31, 1950 2,646,555 Straehl ....--.t July 2l, 1953

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