The invention relates to a method and a rail vehicle for detection of a flaw or flaws in a railway track.

EP 2 750 955 discloses a rail vehicle having rail wheels accommodated to guide the rail vehicle along a railway track, wherein each of the wheels is connected to the vehicle by an intermediate axle box providing a bearing for the wheel, and said axle box is provided with at least one accelerometer, wherein a measurement system on or external of the vehicle is present comprising a receiving portion for signals from the at least one accelerometer. For this purpose the known rail vehicle is provided with a noncontact vibrometer which is arranged to measure vibrational movement of the railway track surface, and the measurement system on or external of the vehicle is used for comparing railway track surface vibrations as measured with the noncontact vibrometer with vibratory signals from the at least one accelerometer.

As is disclosed in EP 2 750 955, due to the interaction between the wheels of the train and the track, dynamic forces arise between the wheels and the rails which cause that the quality and performance of the components and the track system as a whole degrades. Also the interfaces between the components degrades. The components which are subject to (gradual) degradation include the rails, the switches and crossings, the insulated joints, the rail pads, (loose and missing) fasteners, (damaged or hanging) sleepers, as well as their interfaces. Also local poor ballast and slab quality are a concern.

There is a need for a quick and reliable system or method to detect degradation of the respective parts of the railway track early, so as to be able to initiate maintenance of these respective parts of the railway track before the degradation of the railway track becomes problematic. The object is therefore specifically to enable detection of which parts of the railway tracks require maintenance. In this connection degradation can also be understood as a deviation of a (new) construction compared with the original design. According to the invention a method and railway vehicle are proposed in accordance with one or more of the appended claims.

In a first aspect of the invention the measurement system comprises a vehicle-railway track interaction model which generates an estimation of the expected signals from the at least one accelerometer, and the receiving portion and the vehicle-railway track interaction model connect to a comparator to compare the measured signals and the expected signals from the at least one accelerometer, wherein the comparator connects to a tuning portion of the measurement system, which tuning portion is arranged to adjust parameters of the vehicle-railway track interaction model so as to provide a closer fit of the estimation of the expected signals from the at least one accelerometer with the measured signals from the at least one accelerometer.

Accordingly the invention is also embodied in a method for detection of a flaw or flaws in a railway track, whereby the rail vehicle which is provided with at least one accelerometer in an axle box of the vehicle is moved along the railway track for exciting the railway into vibration and that signals from the at least one accelerometer are used for detection of a flaw or flaws in the railway track, wherein the expected signals from the at least one accelerometer are estimated with a vehicle-railway track interaction model and compared with measured signals from the at least one accelerometer, and that parameters of the vehicle-railway track interaction model are subsequently tuned so as to provide a closer fit of the estimation of the expected signals from the at least one accelerometer with the measured signals from the at least one accelerometer.

The reliability of the vehicle-railway track interaction model is thus continuously improved, and the accordingly tuned parameters of the vehicle-railway track interaction model thus provide a reliable indication that maintenance may be required. In comparison with prior art methods, the invention provides the advantage that the level of acceptable deterioration of the railway track and its respective parts can be scientifically determined beforehand, and needs not to be based on historical or experience-based data.

One of the other advantages of the invention is that no specific inspection vehicle is required for the implementation of the method of the invention. In the invention standard railway vehicles may be applied. This tremendously reduces costs, including the reduction of the costs of operation of the railway track itself because it can be more intensely used.

Preferably the vehicle-railway track interaction model includes a model of respective parts of the railway track selected from the group comprising rails, fasteners including rail pads, sleepers, ballast, and substructures. This enables the identification of the specific parts of the railway track that require maintenance.

It is found that best results can be achieved when the parameters of the vehicle-railway track interaction model comprise tuning parameters of respective parts of the railway track selected from the group comprising stiffness, inertia, damping, geometry irregularities.

The invention will hereinafter be further elucidated with reference to the drawing of an exemplary embodiment of a method and railway vehicle according to the invention that is not limiting as to the appended claims.

In the drawing:

-figure 1 shows schematically a railway vehicle of the invention;

-figure 2 shows a representation of the vehicle railway track interaction model used in connection with the railway vehicle of the invention.

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

Figure 1 shows a vehicle 1 that 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 track 2, including the rails 17 and the substructure 5. If there is ballast 16 (or slab) this may be excited into vibration as well. The discrete support of sleepers 6 supporting the rails 17 excites periodic vibration of said rails 17 with a passing frequency and its harmonics corresponding to the vehicle 1 speed and the sleeper 6 spacing.

The vehicle 1 has axle boxes 7, 8 providing a bearing for the wheels 3, 4. An accelerometer 9 provides signals corresponding to vibrations of the bearing of the wheels 3, 4 and of the dynamic wheel-rail contact of the wheels 3, 4 and rails 17, vibrations of the wheels 3, 4 and rails 17 surfaces, as well as vibrations of the railway 2 track itself.

The invention is based on the insight that different track parameters that alter over time and space, such as stiffnesses, will lead to different characteristic frequencies in the acceleration signal from the accelerometer 9. The proposed method and railway vehicle 1 of the invention recognizes that anomalies in the railway 2 track will occur due to degradations caused by forces, stresses and strains in and between the components of the railway 2 track, which forces, stresses and strains are the eventual result of the wheel-rail interaction. The degradations will cause the response of the railway 2 track and its respective components to develop and deviate from their original response, depending on where and how the degradations have taken place. In this regard it is remarked that the different components and interfaces in the railway 2 track system are designed to fulfil their respective functions in the system with different stiffness, damping and wavelength characteristics. Correspondingly they exhibit different frequency contents and magnitudes in their responses. The state of the system and of its components and interfaces can thus be assessed by a vibrational analysis of the responses, which develop in line with the degradation of the components and the interfaces and interaction between these components, resulting in varying input-response relationships.

The vehicle 1 of the invention comprises a measurement system 10 on or external of the vehicle 1 comprising a receiving portion 11 for signals from the at least one accelerometer 9. A quantitative relationship between for instance the parameter stiffness of different parts of the railway 2 track and the acceleration signal from the accelerometer 9 can suitably be provided by a vehicle-railway track interaction model 12. Accordingly the measurement system 10 further comprises a vehicle-railway track interaction model 12 which generates an estimation of the expected signals from the at least one accelerometer 9. The receiving portion 11 and the vehicle-railway track interaction model 12 connect to a comparator 13 to compare the measured signals and the expected signals from the at least one accelerometer 9, wherein the comparator 13 connects to a tuning portion 14 of the measurement system 10, which tuning portion 14 is arranged to adjust parameters of the vehicle-railway track interaction model 12 so as to provide a closer fit of the estimation of the expected signals from the at least one accelerometer 9 with the measured signals from the at least one accelerometer 9.

The railway 2 track can for instance be represented by a two-layer discretely supported model, see Fig. 2. The rails and sleepers can be modeled as beam elements. Ballast and rail-pads can be modeled as discrete spring-damper pairs. The wheel can be simplified as a rigid mass. The load from the suspension springs is applied as a vertical load on the wheel. The wheel-rail contact can be modeled as a Hertzian spring. Accordingly the vehicle-railway track interaction model 12 includes a model of respective parts of the railway track selected from the group comprising rails, fasteners including rail pads, sleepers, ballast, and substructures. The parameters of the vehicle-railway track interaction model 12 comprises tuning parameters of respective parts of the railway track selected from the group comprising stiffness, inertia, damping , geometry irregularities. These parameters are available as is symbolized by reference 15 for deciding whether or not maintenance is required on the respective parts of the railway 2 track.

Although the invention has been discussed in the foregoing with reference to an exemplary embodiment of the method and vehicle of the invention, the invention is not restricted to this particular embodiment which can be varied in many ways without departing from the invention. The discussed exemplary embodiment shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment.