Method for detection of a flaw or flaws in a railway track, and a rail vehicle to be used in such a method

Abstract

Rail vehicle (1) having rail wheels (3,4) accommodated to guide the rail vehicle along a railway track (2) and said vehicle comprising means for detection of a flaw or flaws in the railway track, wherein the rail vehicle is provided with a noncontact vibrometer (9,10) which is arranged to measure vibrational movement of the railway track surface.

Claims

1. A rail vehicle having rail wheels accommodated to guide the rail vehicle along a railway track and said vehicle comprising means for detection of a flaw or flaws in the railway track, which rail vehicle is provided with a noncontact vibrometer which is arranged to measure vibrational movement of a railway track surface, wherein each of the wheels is connected to the vehicle by an intermediate axle box providing a bearing for the wheel, characterized in that said axle box is provided with at least one accelerometer and a comparator on or external to the vehicle compares railway track surface vibrations as measured with the noncontact vibrometer with vibratory signals from the at least one accelerometer.

2. A method for detection of a flaw or flaws in a railway track, the method comprising the steps of: moving a rail vehicle along the railway track to excite the railway track into vibration; measuring vibrational movement of a railway track surface with a noncontact vibrometer; and comparing railway track surface vibrations as measured with the noncontact vibrometer with vibratory signals derived from one or more axle box accelerometers of the vehicle.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

(1) The invention will hereinafter be further elucidated with reference to the drawing of a single FIGURE providing a schematic view of a vehicle according to the invention moving over a railway track.

DETAILED DESCRIPTION OF THE INVENTION

(2) A vehicle 1 runs with a certain speed along a track 2 with or without anomalies. Dynamic wheel-rail interaction is excited because the moving wheels 3, 4 excite vibration of the rails 2, and the ground 5. If there is ballast 14 (or slab) this maybe excited into vibration as well. The discrete support of sleepers 6 supporting the rails 2 excites periodic vibration of said rails 2 with a passing frequency and its harmonics corresponding to the vehicle 1 speed and the sleeper 6 spacing. Certain short wave irregularities excite their respective vibration modes and the anomalies that have developed cause certain frequency contents to deviate from their normal modes.

(3) The vibrations as can be monitored on the rail head surface of the rails 2 can be picked up by accelerometers (that are known per se and not explicitly shown in the FIGURE) at the axle boxes 7, 8, and by a noncontact vibrometer 9, 10 mounted on the vehicle 1, for instance at its underside. A particularly useful noncontact vibrometer is a laser Doppler vibrometer that is embodied with a transducer 9 for emitting a laser signal to the rail's top surface and a receiver 10 for receipt of the laser signal after reflection by the rail's top surface. It is noted however that this is simply one possible embodiment; it is also possible to implement the vibrometer with one single unitary transmitter/receiver. The signals thus derived are processed in computing means 11 to provide the vibrational measurements concerning the rail surface.

(4) It is remarked that the axle box 7, 8 accelerometers may provide signals corresponding to vibrations of the bearing of the wheels and of the wheels 3, 4, dynamic compression of the wheel-rail contact, geometry irregularity of the wheel 3, 4 and rail 2 surfaces, as well as vibration of the track as also measured by the noncontact vibrometer 9, 10 mounted onto the vehicle 1. It is noted once again that this noncontact vibrometer may also be on the bogie or on the axle box. Preferably externally or on the vehicle 1 analyzing means 12 are present for comparing railway 2 track surface vibrations as measured with the noncontact vibrometer 9, 10 and determined by computing means 11, with vibratory signals from at least one accelerometer of an axle box 7, 8 which are processed by computing means 13. The analyzing means 12 may also include storage means enabling later processing of the measurement signals.

(5) The dynamic wheelrail contact force can be derived from the axle box 7, 8 accelerometers after removal of the track vibration component and removal of the noise introduced by the vibration of the wheelset and possibly also of the bearings. The removal of the said noise can be achieved according to the method disclosed in NL 2 003 351. The track vibration components can be removed by making use of the measurement by the noncontact vibrometer 9, 10. In this way the instrumented vehicle 1 will perform a hammer-like test aimed at detecting trackflaws/anomalies/discontinuities at rail 2 such as frogs of switches and crossings, insulated joints and squats where broadband impact force arises at wheel-rail contact, with the wheels acting as the hammers. The vehicle 1 will further act as a track loading vehicle at a normal linear track with the wheel 3, 4 again being the actuator and the actuation frequency being the sleeper 6 passing frequency. At design track irregularities like those in switches and crossings, the situation will be a combination of both types of excitations. At anomalies in the railway 2 track the interaction between track components and between wheel 3, 4 and rail 2 are abnormal, causing deviation in their respective vibration modes. By comparing the respective vibration modes with their design values, the anomalies can be identified. The locations of any anomalies can be determined with an accompanying global positioning system.