Ultrasonic testing device for inspecting thermit rail welds

Abstract

Abstract An ultrasonic testing device for inspecting thermit rail welds in a track is disclosed. The device may be passed over the top of a rail weld in a track to indicate whether there are any faults in the weld. The device includes a longitudinal shoe which may be placed lengthwise along the top surface of the rail, a transmitter which transmits an ultrasonic energy pulse and a receiver for receiving the ultrasonic energy pulse, the transmitter and receiver being positioned and aimed so that an energy pulse is directed downwards towards a location on the under surface of the rail and reflects upwards as an echo pulse so that it is received by the receiver. The indication of the transmittal and receival of the pulse is shown on a cathode ray tube or multi-channel pen recorder. A method of inspecting the thermit rail weld is also disclosed. This includes the transmission of a pulse at an angle of at least 45° through the weld and receiving an echo of this pulse which has been reflected off the bottom surface of the rail. This invention relates to ultrasonic weld testing and in particular to an ultrasonic testing device which may be passed over the top of a rail weld in a track and which indicates if there are any faults in the weld. The inspection of railroad tracks by ultrasonic testing is well known. Previous testing, however, has been primarily used to detect imperfections in the rail itself and the equipment generally includes a transmitter mounted above the rail directed vertically downwards and a receiver adjacent or the same unit as the transmitter. Such a device detects such defects as bolt hole breaks, head end web separations and horizontal split heads. Other types of testing devices have transmitters mounted at an angle above the rail and detect defects in the rail surface or defects located directly under the surface, including burns, shelling or other surface discontinuities. Whereas these devices serve the purpose for which they are intended, they are not suitable for inspecting welds between two rails. Rails are generally welded into reasonably long lengths by flash butt welding in an assembly area. The failure rate of flush butt welds which are welded under controlled conditions is very low. However, thermit welds are usually used in the field to join track together, and here failure rate is higher in view of the difficulty in strictly controlling all the parameters, including temperature of the rail at the time of the weld. Ultrasonic examination of thermit rail welds in a track presents problems, first because the welded structure causes considerable attenuation and scattering of the ultrasonic energy pulses, and second because the physical aspects and shape of the weld is such that it causes numerous non-revelent reflections which with all existing ultrasonic rail testing equipment tend to show that every thermit rail weld is a defective weld. It is, therefore, an object of the present invention to provide a device for inspecting thermit welds in rail track which overcomes the aforementioned problem. It is a further object to provide a device for determining lack of fusion and porosity in a rail and distinguishing one from the other. Yet a further object is to provide a device for inspecting welds in rail track by moving an ultrasonic testing device along the top of the rail over the weld so that lack of fusion or porosity in the weld appears on a cathode ray tube display or a multichannel chart recorder. According to the present invention, these objects and others can be accomplished by providing an ultrasonic testing device for inspecting thermit rail welds in a track, comprising a longitudinal shoe adapted to be placed lengthwise along the top surface of a rail, a means for transmitting an ultrasonic energy pulse and a means for receiving an ultrasonic energy pulse spaced a predetermined distance apart along the longitudinal shoe, the means for transmitting an ultrasonic energy pulse adapted to direct the pulse in a downwards path towards a location on the under surface of the rail below the midpoint between the means for transmitting a pulse and the means for receiving a pulse, the means for receiving a pulse adapted to receive an echo of the pulse reflecting from the location on the under surface of the rail, and means for indicating the transmission of the pulse, the receiving of the echo of the pulse, and the time interval for the pulse to pass downward through the rail and the echo of the pulse to pass upward through the rail. The present invention also provides a method of inspecting a thermit rail weld in a track comprising transmitting an ultrasonic energy pulse from the top of the track at one side of the thermit rail weld at an angle of at least 45° through the weld, receiving on the top of the track at the other side of the thermit rail weld an echo pulse of the ultrasonic energy pulse reflecting from the underside of the rail indicating transparency in the weld. The advantage of this invention, both as to its construction and mode of operation, will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings which illustrate embodiments of the invention.

Inventors

• 👤 Georges E. Vezina

Bibliographic Details