Method and measuring device for determining the longitudinal loading in a railway rail

Abstract

The invention relates to a method for determining the longitudinal loading (N, T0), in particular the longitudinal force (N), in a railway rail (2), the method comprising the steps of: acquiring at least one measurement signal which correlates with the longitudinal loading (N, T0) in the railway rail (2); determining the longitudinal loading (N, T0) on the basis of the at least one measurement signal, wherein the longitudinal loading (N, T0) is determined on the basis of a measurement signal from at least one sensor (21, 29) permanently connected to the railway rail (2) and / or on the basis of a vibration frequency and / or vibration period of the railway rail (2) determined by means of the at least one measurement signal. The invention also relates to a measuring device (1.1, 1.2) for determining the longitudinal loading (N, T0), in particular the longitudinal force (N), in the railway rail (2).

Description

[0001] Method and measuring device for determining the longitudinal load in a railway track

[0002] The content of the German patent application DE 102025 101 319.5 is incorporated herein by reference.

[0003] The invention relates to a method for determining the longitudinal load in a railway track. Furthermore, the invention relates to a measuring device for determining the longitudinal load in a railway track.

[0004] From WO 2023 / 066918 A1, a method and a device for determining the longitudinal load in a railway track are known. This requires moving a section of track vertically, in particular by means of a lifting and straightening unit. Such a method involves considerable mechanical, temporal, and economic costs.

[0005] The invention is based on the objective of creating an improved method for determining the longitudinal load in a railway track, which in particular leads to particularly precise results, is flexible in terms of location and time and is economically feasible.

[0006] This problem is solved by a method with the features of claim 1. It has been recognized that a method for determining the longitudinal load, in particular the longitudinal force, in a track rail yields particularly precise results and is particularly flexible and economical to implement if the longitudinal load, in particular the longitudinal force, is determined based on the vibration frequency and / or the vibration period of the track rail determined by means of the at least one measurement signal. Since the at least one sensor is preferably permanently connected to the track rail, the at least one measurement signal can be acquired independently of the arrangement of a measuring vehicle at the evaluation position, both temporally and spatially. In particular, continuous or short-term determination of the longitudinal load, in particular the longitudinal force, is enabled.Furthermore, contact problems, particularly those caused by contamination, between the track rail and a reversibly installed sensor can be avoided. Based on the vibration frequency and / or duration, the longitudinal load, especially the longitudinal force, can be determined with exceptional precision and flexibility, particularly with reduced data, and especially without a reference temperature during track laying. With precise and flexible information about the longitudinal load, track construction measures whose feasibility depends on the longitudinal load can be planned and carried out with exceptional reliability and flexibility, and economically. Precise knowledge of the longitudinal load prevents damage to the track due to incorrect approval of track construction measures under excessive longitudinal loads. The method thus ensures the construction, maintenance, and operation of the rail transport system in a particularly safe and economical manner.

[0007] It is preferred, but generally optional, that the longitudinal load, in particular the longitudinal force, is determined based on the vibration frequency and / or the vibration period of the track rail as determined by means of at least one measurement signal. Alternatively or additionally, the longitudinal load can be determined based on a measurement signal from at least one sensor permanently connected to the track rail. Longitudinal load is understood to be information corresponding to the magnitude of the load on the track rail in the longitudinal direction of the rail. The longitudinal load can include, and in particular consist of, a longitudinal force and / or a longitudinal stress and / or a longitudinal strain and / or a neutral temperature of the track rail. Longitudinal force is understood to be, in particular, a shear force oriented parallel to the longitudinal direction of the rail, especially the normal force, of the track rail.The neutral temperature is understood to be the temperature of the track rail at which the longitudinal force or longitudinal stress, in particular the residual stress, becomes zero. The longitudinal force is frequently described below, but this always includes the longitudinal load in general, as well as the alternatives to longitudinal force mentioned above. Preferably, the longitudinal load is always defined as the longitudinal force.

[0008] The track rails can be continuously welded or non-welded, particularly those of a jointed track system. The method is equally suitable for both types of track.

[0009] A permanent connection is preferably understood to be a connection that cannot be irreversibly detached or detachable without destruction. Preferably, the at least one sensor is positively connected to the track rail, in particular by crimping, and / or by a material bond, in particular by welding and / or bonding.

[0010] Correlation, in particular of the measurement signal with the longitudinal force, is understood to mean that a known, unambiguous, and especially analytically describable, preferably linear, relationship exists. The vibration frequency of the track rail is preferably the frequency of a transverse vibration or a vibration with a vibration amplitude oriented horizontally and / or perpendicular to the longitudinal direction of the rail. The longitudinal force can be derived from the transverse vibration particularly efficiently and precisely.

[0011] The oscillation period is the reciprocal of the oscillation frequency.

[0012] To determine the vibration frequency and / or duration, a time-dependent profile of the measurement signal is preferably evaluated. In particular, at least one natural frequency of the track rail can be determined based on the vibration frequency and / or duration. The normal force can then be deduced from the natural frequency using known methods, in particular an analytical equation and / or a numerical model, especially a finite element method (FEM) model. For this purpose, the relationship can be used whereby the vibration frequency of a transverse vibration correlates with the longitudinal load, in particular the longitudinal force, on the track rail, and is in particular approximately directly proportional to the square root of the longitudinal force, in particular the square root of the quotient of the longitudinal stress and the density of the track rail material, wherein the longitudinal stress preferably results from the quotient of the longitudinal force and the cross-sectional area of ​​the track rail.

[0013] Preferably, the longitudinal load is determined taking into account the bending and / or longitudinal stiffness of the track rail and / or the stiffness of at least one track rail support, in particular the stiffness of the ballast bed and / or at least one rail fastening and / or at least one track sleeper, and / or the weight of the track rail and / or the density of the ballast bed. The vibration frequency is preferably a natural frequency of the track rail.

[0014] The vibration frequency can be determined under tensile and / or compressive stress on the track rail, particularly due to thermal expansion, or specifically under tensile stress and / or compressive stress only, especially in a neutral fiber of the track rail. In particular, when determining the longitudinal load, it is possible to distinguish between tensile and compressive stress.

[0015] The longitudinal force can be determined by comparing the current temperature of the track rail with a reference temperature at the time the track was laid. For a continuously welded track, the longitudinal force results from the thermal expansion according to the following equation:

[0016] N = —a * AT * E * A,

[0017] where a is the coefficient of thermal expansion, AT is the temperature difference between the current temperature and the reference temperature, E is the modulus of elasticity of the track material, and A is the cross-sectional area of ​​the track. Determining the longitudinal force using this method requires that the reference temperature is known. Furthermore, additional strains introduced into the track, particularly the track rail, especially mechanical strains, can lead to errors in the determined longitudinal force. Determining the longitudinal force based on the oscillation frequency and / or duration eliminates the need for a reference temperature. Additional strains in the track are taken into account. Consequently, determining the longitudinal force based on the oscillation frequency and / or duration is particularly flexible and leads to especially precise results.

[0018] The reference temperature refers to the temperature of the track rail during installation or welding. Reference strain refers to the longitudinal strain of the track rail or a strain sensor during installation or welding. The reference strain is preferably zero.

[0019] Determining the longitudinal force on the track bed based on the measurement signals is preferably automated, in particular by means of an evaluation unit, especially an electronic one. The evaluation unit can be connected to at least one, and in particular all, of the sensors for receiving the measurement signals. The evaluation unit can include a signal converter for converting the sensor signals, especially optical signals, into electrical, and in particular digital, signals.

[0020] Preferably, the evaluation unit comprises at least one electronic processor and / or a data storage device. The data storage device may include a computer program containing instructions that instruct a computer to execute the method.

[0021] The invention also relates to the computer program product and the data storage device containing the computer program product. The evaluation unit can be stationary, in particular located on the track. The evaluation unit can be connected to the at least one sensor via a wired signal connection. For communication, in particular wireless and / or wired communication, with a rail vehicle and / or a central computing unit, in particular a control center of the rail traffic system, the evaluation unit can have at least one additional communication connection, in particular a radio module and / or a wired data interface.

[0022] A rail vehicle can be designed as a transport vehicle and / or as a work vehicle, in particular as a track construction vehicle.

[0023] The evaluation unit may have a data interface, in particular a network interface, in particular a wired interface, in particular a USB interface, and / or a wireless interface, in particular a GPRS interface and / or a WiFi interface, and / or its own power supply, in particular an electrochemical energy storage device, and / or an electrical connection, in particular for supplying the electrical energy required for operation, and / or a protective housing and / or a data storage device, in particular for temporarily storing the measurement signals and / or information on the integrity of the railway system and / or reference values ​​of the measurement signals and / or limit values, in particular warning and / or intervention limit values, in particular with regard to maintenance and / or quality assurance, and / or for storing the computer program product.in particular for automatically executing the procedure for determining the condition of the track bed and / or for carrying out statistical methods, in particular for calculating the mean and / or for determining a standard deviation, and / or having a processor for processing the measurement signals, in particular with a clock frequency of at least 8 MHz, in particular at least 1 GHz and / or a maximum of 100 GHz.

[0024] The evaluation unit and / or a central processing unit can be configured to determine the axial force based on a structural mechanics model, in particular a finite element method (FEM) model, and / or on analytical equations. These are preferably implemented in a computer program and / or stored in a data memory of the evaluation unit and / or the central processing unit.

[0025] To determine the longitudinal force, the measurement signal from at least one sensor can be evaluated individually, particularly at a specific point in time and / or over time. A single value can provide information about the instantaneous longitudinal force on the track rail. The time-dependent trend can reveal changes in the longitudinal force. In particular, the change in longitudinal force over time can provide a forecast of future longitudinal force, especially at a specific time of day and / or on a specific date and / or under specific weather conditions. Based on this forecast, track construction measures can be planned and / or initiated.

[0026] According to one aspect, the longitudinal load can be determined using at least one measurement signal from at least one strain sensor permanently connected to the track rail. The at least one strain sensor is preferably designed, and in particular arranged on the track rail, such that it can detect strains in the longitudinal direction of the track rail. The longitudinal strain correlates with the longitudinal force according to the equation

[0027] N = s * E * A,

[0028] where e stands for strain. This applies in particular to a track rail whose longitudinal strain is not blocked, for example, a jointed track. Using at least one strain sensor, the longitudinal force can thus be precisely determined.

[0029] To precisely determine the strain of the track rail based on the measurement signal from at least one strain sensor, it may be necessary to generate a reference measurement signal and / or the reference strain of the strain sensor in a stress-free state and / or at a specific temperature, in particular the reference temperature. These can be acquired, and in particular stored, during the laying of the track, especially the track rails, or during the application of the at least one strain sensor.

[0030] According to another aspect, the longitudinal load can be determined using a measurement signal from at least one temperature sensor permanently connected to the track rail. The longitudinal force correlates with the temperature difference AT as described above. Because the at least one temperature sensor is attached to the track rail, the temperature of the track rail can be measured with particular precision.

[0031] The longitudinal load is preferably determined using the measurement signals from at least one strain sensor and at least one temperature sensor. With a continuously welded track rail, expansion is largely prevented, so that thermal expansion is largely absorbed by the elasticity of the track rail material. However, expansion can still occur, for example, from track displacement, such as due to alternating thermal expansion or track construction work, particularly lifting, straightening, and / or stabilizing the track, from rail vehicles running over the track, and / or from creep. Alternating thermal expansion can lead to displacement, which is particularly pronounced in curves and is referred to as "curve breathing." Such expansion can be detected by the at least one strain sensor.The axial force is determined taking into account the measurement signals of the strain and temperature sensors as follows:.

[0032]

[0033] The axial force can also be determined using other or additional, especially more complex, analytical equations and / or using numerical simulation, especially by means of an FEM model.

[0034] Preferably, at each evaluation position, the measurement signals of at least one temperature sensor and at least one strain sensor are evaluated to determine longitudinal load, in particular the longitudinal force.

[0035] According to another aspect, the longitudinal load can be determined using a measurement signal from at least one fiber optic sensor permanently connected to the track rail, in particular a fiber Bragg grating sensor. Preferably, the at least one strain sensor and / or the at least one temperature sensor are designed as corresponding fiber optic sensors. Such a sensor ensures particularly precise measurement results, is corrosion-resistant, and its measurement signals can be transmitted reliably, and especially without interference, over long distances, particularly more than 100 m. Furthermore, several such strain sensors can be integrated into a single optical fiber. Alternatively or additionally, at least one of the strain sensors can be designed as an electrical strain sensor, in particular as a strain gauge.

[0036] According to one aspect, the longitudinal stress can be determined using the measurement signals from several sensors permanently connected to the track rail, in particular using at least 20, in particular at least 50, in particular at least 100, in particular at least 250, in particular at least 500, in particular at least 1,000, in particular at least 2,000, and / or a maximum of 10,000, in particular a maximum of 5,000, in particular a maximum of 3,000, strain sensors, which are preferably arranged at intervals along the track rail. With a sufficiently large number of sensors, the track rail can be determined over long sections with high spatial resolution. Track construction work, in particular maintenance work, which in particular requires intervention in the integrity of the track grid, especially the track rail, can thus be planned or initiated with particular flexibility, especially at short notice.The rail transport system can therefore be operated in a particularly economical way.

[0037] Preferably, the longitudinal load is determined at several evaluation positions along the track. At least one, and in particular exactly one, value for the longitudinal load can be determined at each evaluation position. At least one sensor, and in particular at least one, and in particular exactly one, strain sensor and / or temperature sensor, can be assigned to each evaluation position. The number of evaluation positions can be within the ranges described above regarding the number of sensors. The evaluation position is also referred to as the measurement position.

[0038] According to one aspect, a substitute value, in particular a mean value, of the longitudinal load can be determined based on the measurement signals of several sensors and using at least one statistical method. The at least one statistical method can include determining a mean value, a standard deviation, and / or a maximum value.

[0039] Longitudinal loads can vary significantly over short distances along the rail, for example, due to varying solar radiation or shading and / or differing humidity, and / or different support reactions, particularly across the track sleepers, especially due to differing shear resistances, particularly lateral and / or longitudinal shear resistances. Using the equivalent value for longitudinal load, especially longitudinal force, longitudinal forces determined by multiple sensors, particularly those measured at multiple evaluation points, can be taken into account. The equivalent value is therefore particularly informative regarding the technically relevant load state of the track rail, especially for assessing the feasibility of track construction measures.The at least one, in particular the exactly one, substitute value is preferably determined on the basis of the measurement signals from at least 5, in particular at least 10, in particular at least 20, in particular at least 50, sensors and / or on the basis of the measurement signals from sensors at a corresponding number of evaluation positions.

[0040] According to one aspect, based on the measurement signals, in particular based on the substitute value, especially in addition to or as an alternative to the assessment of the permissibility of a track construction measure, a recommendation for action regarding the implementation of a track construction measure can be determined and / or issued, in particular a recommendation regarding the timing and / or scope of the track construction measure, for example for track bed compaction and / or stabilization.

[0041] According to another aspect, the multiple sensors can be components of a linear detection device that extends, in particular, over a measuring section along the track rail with a length of at least 50 m, in particular at least 100 m, in particular at least 300 m, in particular at least 1 km, and / or a maximum of 20 km, in particular a maximum of 10 km. The sensors, in particular those of the same measuring fiber, can be designed as strain sensors and / or as temperature sensors. The sensors can be designed exclusively in the form of fiber optic sensors. Alternatively, the linear detection device can additionally or exclusively include electrical sensors, in particular strain gauges.

[0042] The linear detection element can be a single piece, in particular not divisible without damage, and / or continuous. The linear detection element can have at least one and / or a maximum of five, in particular a maximum of two, connections, or a single connection for connecting to the electronic evaluation unit. The at least one connection can be configured for transmitting optical and / or electrical signals. The at least one connection can be located at a free end and / or between the free ends of the linear detection element. A connection located between the ends can be configured as a bending coupler. At least one connection can be configured as a monitoring connection.

[0043] The length of the measuring section is preferably measured along the linear detection means and / or along the track rail and / or is determined by the distance between the first and the last strain sensor of the linear detection means.

[0044] The linear detection means preferably comprises at least two, in particular at least five, in particular at least 10, and / or a maximum of 50, in particular a maximum of 20 signal lines, in particular optical and / or electrical signal lines. The linear detection means can be designed as a measuring tape, in particular with signal lines arranged adjacent to each other, in particular side by side.

[0045] The multiple signal lines can be materially bonded together to form the detection means and / or arranged within the same covering material, in particular insulating sheath, and in particular glued together by this.

[0046] Preferably, the linear detection means is further developed with at least one of the features described in PCT / EP2024 / 070372, the contents of which are incorporated herein by reference. Preferably, the linear detection means, in particular the multiple strain sensors, is designed to be attached to the at least one track rail, in particular to be clamped and / or glued to it, especially in the area of ​​the rail fastening or the track sleepers and / or on the rail foot and / or the rail web and / or the rail head, and / or to be laid below and / or on and / or within the track sleepers, in particular to be fastened.

[0047] According to a further aspect, at least one track rail is loaded, with the longitudinal load being determined based on at least one measurement signal acquired during loading. The longitudinal load, in particular the longitudinal force, can be determined on the loaded track rail and / or on the opposite track rail. The load can be parallel and / or preferably inclined, in particular perpendicular, to the longitudinal direction of the rail and / or horizontally oriented. The load is preferably an impact load. The load can be dynamic and / or static. Preferably, the load is a mechanical load acting on the track rail. Alternatively, the load can be thermal. The loading is preferably carried out in a defined manner, i.e., with a known load magnitude. Based on the measurement signal acquired during loading, the longitudinal force can be determined with particular precision.

[0048] The sensor for determining the measurement signal under the load of the track rail can be at least one sensor permanently connected to the track rail and / or another sensor, in particular a sensor detachably connected to the track rail and / or a contactless measuring sensor and / or a mobile sensor, which can be, for example, an optical sensor and / or an acoustic sensor, in particular an ultrasonic sensor, and / or a tactile sensor.

[0049] According to another aspect, applying a load to the track rail causes it to vibrate. The vibration frequency and / or duration can be determined, in particular by means of at least one sensor. The sensor for determining the vibration frequency and / or duration can be, in particular, a mobile sensor. Preferably, the vibration frequency and / or duration of a transverse vibration of the track rail is determined. Based on the vibration frequency and / or duration, especially the transverse vibration, the longitudinal force can be determined with particular precision. Similar to the strings of a musical instrument, the vibration frequency and / or duration provides information about the longitudinal stress, in particular the temperature-induced residual stress, in the track rail and thus about the longitudinal force.

[0050] To induce vibration, the track rail can be loaded using a track construction tool, in particular a lifting and aligning unit and / or a dynamic track stabilizer, and / or by means of, in particular the weight force of, a track vehicle traveling on the guide rail, in particular a traffic vehicle and / or a measuring vehicle. Alternatively, the track rail can be struck manually, in particular with a test hammer, to generate the vibration. The load can also be generated by means of a test actuator, in particular one that can be reversibly positioned on the track bed.

[0051] According to another aspect, track construction work can be initiated and / or controlled based on a specific longitudinal load, particularly the longitudinal force. For example, track construction work, especially for constructing, laying, and / or maintaining the track, can be initiated and / or authorized depending on the specific longitudinal force, particularly its equivalent value. A track tamping operation, a lifting and straightening operation, and / or a track stabilization operation are preferably authorized if the longitudinal force does not exceed a specific, predetermined limit.

[0052] Control can alternatively or additionally be achieved by limiting the load and / or stress exerted on the track, particularly the rail, by the track construction work, especially by limiting it to a predetermined maximum value, or specifically by reducing it. For example, deflection of the rails or track bed, especially straightening movement, and / or lifting of the rails or track bed can be limited to a predetermined maximum value, especially a maximum straightening value and / or a predetermined maximum height. This prevents excessive stress on the rail due to longitudinal forces and / or buckling of the rail.

[0053] According to one aspect, the permissibility of a track construction measure and / or the operational safety of the track, particularly with regard to the risk of buckling of a track rail, can be assessed based on the measurement signals and on information about the structural properties of the track, especially the sleeper type and / or the rail type and / or the ballast type and / or the implementation of measures to secure the track position, especially safety caps. Such information can be retrieved from a database, especially the central processing unit. The longitudinal forces can be evaluated in relation to specific positions to enable position-specific control of the track construction measure. In particular, the control can be carried out individually for each evaluation position.

[0054] The specified longitudinal load, in particular the longitudinal force, can be transmitted to the track construction device for controlling the track construction measure immediately before and / or during and / or immediately after the track construction measure, and / or while the track construction device is positioned at the section of track to be worked on and / or at the evaluation position. Alternatively, instead of transmitting the longitudinal force, the control command derived from it can be transmitted to the track construction device.

[0055] Limiting the load can depend on the type of track construction machine and / or the condition, in particular the integrity and / or type, of the track rail. The type of track construction machine allows conclusions to be drawn about the load that the machine can exert on the track rail. The type of track rail can include its geometry and material. The integrity of the track rail can be determined, for example, using an optical method, in particular image analysis, and / or by means of at least one sensor attached to the track rail.

[0056] Alternatively or additionally to determining the longitudinal load based on the vibration frequency and / or duration of the track rail, the longitudinal load can be determined based on the strain, in particular a static and / or quasi-static strain, of the track rail. In general, especially when determining the longitudinal load based on strain, an adjustment and / or calibration of the measuring method, in particular the calculation methodology for determining the longitudinal load, and / or the measuring device can be carried out, in particular based on the measurement signals and / or taking into account the rail vibration, in particular measurement signals correlated with it, and / or based on the sensitivity of the measurement signals to a load on the track rail and / or based on recorded strains and / or with known load on the track rail, in particular known test force acting on the track rail, and / or known temperature of the track rail.

[0057] The internal stress of the rail can change the measured absolute strain. If this change is taken into account during calibration, for example, by measuring the absolute strain in response to a defined load at different temperatures, the stress state, and thus the longitudinal load, can be determined.

[0058] According to one aspect, the at least one measurement signal for determining the longitudinal load in the track rail can be acquired at, in particular at least two, in particular at least three, in particular at least five, in particular at least ten, different temperatures of the track rail and / or at at least one, in particular at least two, in particular at least three, in particular at least five, in particular at least ten, different, in particular defined, loads on the track rail. The defined load can be a test force, preferably provided by means of a test actuator and / or by passing a rail vehicle, in particular with a known weight, preferably a weighed vehicle with known axle loads and / or wheel contact force, and / or known speed, over the track rail.An approximate linear relationship can exist between longitudinal load, particularly longitudinal force, and temperature. The longitudinal loads determined at various temperatures and / or loads, especially the determined neutral temperature or the residual stress of the track rail, can be checked for accuracy by comparison, preferably taking the linear relationship into account. A corresponding plausibility check can alternatively or additionally be carried out using the longitudinal loads determined at the different loads.

[0059] Preferably, the longitudinal load is determined using statistical methods, in particular by calculating a mean and / or a standard deviation.

[0060] To determine the longitudinal load, at least one measurement signal can be used as the basis for an evaluation model, in particular a structural mechanics calculation model, in particular an FEM model, in particular comprising the track rail and / or at least one, in particular several, track sleepers and / or a track bed.

[0061] Preferably, the measuring method and / or the measuring device is calibrated by recording the measurement signals at a specific test force and / or temperature and / or at a known longitudinal load, preferably using measurement signals at at least two different temperatures. The strain is preferably measured at several points on the rail circumference, for example, on the left and right sides of the rail foot and / or head and / or web. This allows torsional loads to be determined, in particular, and taken into account when determining the longitudinal load.

[0062] Preferably, methods of machine learning, in particular artificial intelligence, especially unsupervised learning, can be used to determine the longitudinal load and / or to calibrate or adjust.

[0063] The sensors permanently attached to the track rail, preferably fiber Bragg grating sensors, in particular strain and / or temperature sensors, can be used to determine the longitudinal load, in particular a residual stress, of the track rail in such a way that the sensitivity and / or the reaction of the measurement signal, in particular the strain signal, to a defined load, preferably of a weighed vehicle traveling on the track rail with known axle loads and / or wheel contact forces, at different temperatures is determined, preferably evaluated in an evaluation model and / or a calculation model.

[0064] Loads are preferably understood to be loads exerted on the track rail, in particular test forces.

[0065] A further object of the invention is to provide an improved measuring device for determining the longitudinal load, in particular the longitudinal force, in a track rail, which makes the longitudinal load, in particular the longitudinal force, determinable in a particularly flexible manner in terms of location and time, as well as precisely and economically.

[0066] This problem is solved by a measuring device for determining the longitudinal load, in particular the longitudinal force, in a track rail, comprising at least one sensor for acquiring at least one measurement signal that correlates with the longitudinal load, in particular the longitudinal force, in the track rail, and an electronic evaluation unit configured to determine the longitudinal load, in particular the longitudinal force, based on the at least one measurement signal. The evaluation unit is configured to determine a vibration frequency and / or duration of the track rail based on the at least one measurement signal and to determine the longitudinal load, in particular the longitudinal force, based on the vibration frequency and / or duration. The measuring device is preferably further developed with at least one of the features described above in connection with the method. The advantages of the measuring device preferably correspond to the advantages of the method.

[0067] It is preferred, but fundamentally optional, that the evaluation unit is designed to determine the vibration frequency and / or duration of the track rail based on the at least one measurement signal and / or to determine the longitudinal load, in particular the longitudinal force, based on the vibration frequency and / or duration. Alternatively or additionally, the at least one sensor for acquiring the at least one measurement signal can be permanently connected to the track rail.

[0068] The measuring device can be stationary, particularly due to the at least one sensor being permanently connected to the track rail, and / or reversibly detachable from the track rail, particularly mobile, especially with at least one mobile sensor. The mobile sensor can be portable, particularly as a handheld device. The at least one mobile sensor can comprise a strain sensor and / or a temperature sensor and / or a vibration sensor.

[0069] Preferably, the mobile measuring device comprises the load-bearing device, in particular at least one test actuator for loading the track rail, and / or the at least one sensor / or the evaluation unit.

[0070] According to one aspect, the at least one sensor can be a fiber optic strain sensor, in particular a fiber Bragg grating sensor.

[0071] Further features, details, and advantages will become apparent from the following description of exemplary embodiments with reference to the figures. These show:

[0072] Fig. 1 A schematic representation of a rail transport system with different measuring devices for determining the longitudinal forces in a track rail, each comprising at least one sensor and an evaluation unit, wherein a track construction vehicle is arranged on the track, or

[0073] Fig. 2 shows a schematic representation of the rail transport system in Fig. 1, with a transport vehicle arranged on the track. With reference to Figs. 1 and 2, exemplary embodiments of measuring devices 1.1, 1.2 for determining the longitudinal force N in a track rail 2 are described.

[0074] The measuring device 1.1 according to the first embodiment is integrated into a rail transport system 3.

[0075] The rail transport system 3 comprises a rail network with several track sections 4. Each track section 4 has a track bed 5 with track sleepers 6 and track rails 2 arranged on it. The track bed 5 rests on a track bed 7 designed as a ballast bed. Alternatively, the track bed 7 can be a solid, ballastless surface.

[0076] The track section 4 can include an overhead line 8 for supplying rail vehicles 9 with electrical energy. The respective rail vehicle 9 can be a transport vehicle 9.1 or a work vehicle 9.2, in particular a track construction vehicle, a maintenance vehicle and / or a measuring vehicle. Alternatively, the rail vehicles 9 can have their own energy supply, for example, fuel. The respective rail vehicle 9 includes a bogie 10 with track wheels 11 on several axles 12.

[0077] The respective track rail 2 is designed as a continuously welded track rail. Alternatively, the track can be designed as a butt joint track.

[0078] The track rails 2 are laid at a specific temperature T, the neutral temperature To. A temperature change AT compared to the neutral temperature To leads to a thermal expansion 8T according to the equation. T = a * AT

[0079] where a denotes the coefficient of thermal expansion and AT the temperature change. Expansion of the track is prevented in the case of a continuously welded track. Consequently, a longitudinal force N occurs in the track rails 2, which compensates for the thermal expansion 8. The longitudinal force is determined according to the following equation:

[0080] N = —s T * E * A = —a * AT * E * A,

[0081] where E is the modulus of elasticity of track rail 2 and A is the cross-sectional area of ​​track rail 2.

[0082] Temperature changes put stress on the track rails 2. Temperatures below the neutral temperature To result in tensile forces, and temperatures above the neutral temperature To result in compressive forces. The material of the track rails 2 is selected such that they can withstand a typical temperature range of -25°C to +65°C. In the case of compressive forces, in addition to strength, the stability, and in particular the buckling behavior, of the track rails 2 is crucial. To keep the stress on the track rails 2 as low as possible, they are typically installed at a temperature in the range of 20°C to 26°C, which is also referred to below as the reference temperature TR.

[0083] Creep processes and / or displacement of the track rails 2 relative to the track bed can lead to changes in the neutral temperature To, meaning that it is ultimately not precisely known. The neutral temperature To is crucial for various track construction operations. For example, the position of the track rails 2 must not be changed if the temperature T is too far above the neutral temperature To, in order to avoid an impermissible reduction in the displacement resistance, especially the lateral displacement resistance, or buckling of the track rails 2. At temperatures T below the neutral temperature To, it must be ensured that the sum of all loads acting on the track rails 2, especially the combination of temperature loads and track construction loads, does not exceed the permissible stress on the track rails 2.Moving the track rail 2 usually introduces additional tensile forces into the track rail 2, which, in combination with temperature-related tensile forces, could lead to an overload of the track rail 2.

[0084] The neutral temperature To is therefore relevant for track construction work that interferes with the structural integrity of the track superstructure, in particular the track grid 5, for example by cutting the track rails 2, welding the track rails 2, grinding the track rails 2, loosening the rail fastenings 13 and / or compacting the track bed 7.

[0085] With precise knowledge of the neutral temperature To, impermissible stresses on the track or highly restrictive safety precautions, such as limiting track construction work to a few calendar days when temperatures are within a narrow permissible range, can be avoided. Maintenance measures are more flexible and therefore particularly economical. The measuring device 1.1 comprises an electronic evaluation unit 20 and at least one sensor, in particular at least one strain sensor 21 and / or at least one temperature sensor 29.

[0086] Preferably, the measuring device 1.1 comprises a linear detection means 19. The linear detection means 19 can comprise a plurality of sensors 21, 29, in particular at least 20, in particular at least 100, in particular at least 500, in particular at least 2,000, and / or a maximum of 10,000, in particular a maximum of 5,000, in particular a maximum of 3,000, of the sensors 21, 29. The at least one sensor 21, 29, in particular all sensors 21, 29, are preferably designed as fiber optic sensors, in particular as fiber Bragg grating sensors.

[0087] The detection means 19 can have one or more optical fibers. Preferably, at least one, in particular exactly one or more, of the optical fibers is configured with the at least one sensor 21, 29 and / or at least one, in particular exactly one or more, of the optical fibers is configured without a sensor 21, 29, particularly for transmitting data.

[0088] The sensors 21, 29, in particular the number mentioned above, are preferably formed on a one-piece detection means 19, in particular by a single or more optical fibers.

[0089] The detection device 19 can comprise at least one, in particular several, electrical signal lines. The multiple optical fibers and / or the at least one electrical signal line can be materially bonded together to form the detection device 19, in particular by means of a carrier material, in particular an insulating material, in particular by means of which they are embedded and / or encased and / or bonded together by means of which they are embedded.

[0090] The linear detection device 19 is attached to the track rails 2, in particular in the area of ​​the rail fastenings 13, in particular clamped and / or glued.

[0091] The evaluation unit 20 is designed to determine the axial force N in the at least one track rail 2 based on the measurement signal from the at least one sensor 21, 29. For this purpose, the evaluation unit 20 can be in signal communication with several, preferably all, of the sensors 21, 29. The evaluation unit 20 can include a signal converter for converting optical signals from the sensors 21, 29 into electrical signals.

[0092] The evaluation unit 20 can be in signal communication with a central computing unit 22, in particular a control center 23, of the rail transport system 2. The signal communication 24 is preferably wireless. For this purpose, the evaluation unit 20 can have a radio module 25.

[0093] Preferably, the measuring device 1.1 has two linear detection means 19, each attached to one of the track rails 2. The evaluation unit 20 can be in signal communication with the sensors 21, 29 of one or more, in particular both, detection means 19. The work vehicle 9.2 can have a load unit 26, in particular separate from the track wheels 11, for exerting a test force F on the at least one track rail 2, which preferably has a force component oriented horizontally and perpendicular to the longitudinal direction 30 of the rail. The load unit 26 can, for example, be a lifting and aligning unit 26.1 and / or a dynamic track stabilizer (not shown).

[0094] Alternatively, the work vehicle 9.2 can be a measuring vehicle, which is specifically designed to load the track rails 2 via the track wheels 11 in a defined vertical direction, in particular with a previously known weight force.

[0095] The work vehicle 9.2 can have at least one track tamping unit 26.2 for compacting the ballast bed 7. Preferably, the work vehicle 9.2 is a track tamping machine.

[0096] The work vehicle 9.2 can be in signal communication with the control center 23, particularly wirelessly. Alternatively or additionally, the work vehicle 9.2 can be in signal communication with the evaluation unit 20.

[0097] The detection means 19, in particular the strain sensors 21, preferably extends over a measuring distance 31 with a length L in a range of 100 m to 10 km, in particular from 500 m to 5 km, in particular from 1 km to 3 km.

[0098] The rail vehicle 9, in particular the work vehicle 9.2, especially the track tamping machine, may have a control unit 28 for controlling the track tamping unit 26.2 and / or the lifting and aligning unit 26.1. A corresponding control unit may be provided for controlling the dynamic track stabilizer. The control unit 28 may be configured to control and / or document the work carried out on the track bed 7, in particular the scope of the measures taken. The control unit 28 may have an electronic processor 28.1 for processing control commands and / or documentation information and / or a data storage device 28.2 for storing the documentation information.

[0099] The operating principle of the method or measuring device 1.1, 1.2 for determining the longitudinal force N in the track rail 2 is as follows:

[0100] The reference temperature TR and / or the reference strain £R of the track, in particular of the track rails 2, are documented in the undeveloped state of the track rail 2 and / or during the installation of the track rail 2. The reference temperature TR initially corresponds to the neutral temperature To, provided that the track rails 2 are installed without longitudinal forces.

[0101] Preferably, the respective reference temperatures TR and / or the reference strains £R of the track rails 2 for different track sections of the rail transport system 3 are stored on a digital storage medium, in particular in the data storage 20.2 of the evaluation unit 20 or the control center 23, particularly for one or more evaluation positions, in particular for each sensor 21, 29, particularly along the track section 4. The linear detection means 19 are attached to the track rails 2, in particular in the area of ​​the rail fastenings 13, in particular clamped and / or bonded. The at least one sensor 21, 29 provides measurement signals, in particular in the form of light signals. The measurement signals of the sensors 21, 29 are read out and processed by means of the evaluation unit 20.

[0102] The strain sensors 21 and the temperature sensors 29 provide measurement signals, particularly in the form of light signals. The measurement signals from sensors 21 and 29 are read and processed by the evaluation unit 20.

[0103] Preferably, the measurement signals from sensors 21, 29 are first evaluated and stored in a state in which the track rails 2 have the reference temperature TR or are freshly laid. The reference values ​​thus determined using sensors 21, 29, in particular the reference temperature TR and / or the reference strains ΣR, can be stored as reference values ​​in a data storage device 20.2 of the evaluation unit 20 or the control center 23. Alternatively, a data set with corresponding reference values ​​can be provided from an external source and / or stored in the data storage device 20.2 of the evaluation unit 20 or the control center 23.

[0104] The at least one measurement signal from sensors 21, 29 is preferably acquired continuously and / or at specific and / or manually determined and / or automatically determined times and / or at fixed time intervals, for example at a frequency of at least 1 / day, in particular at least 1 / hour, in particular at least 1 / minute, in particular at least 1 Hz, in particular at least 10 Hz, in particular at least 100 Hz, in particular at least 1 kHz, and / or at most 1 MHz, in particular at most 1 kHz. The at least one measurement signal is particularly preferably acquired before, in particular immediately before, and / or during, and / or after, a track maintenance operation, in particular a track maintenance operation that affects the integrity of the track, in particular the track rails 2 or their rail fastening 13, in the area of ​​the at least one sensor 21, 29, in particular the track section 4 formed therewith.

[0105] Based on the at least one measurement signal, the longitudinal force N in the at least one track rail 2 is determined, in particular by means of the evaluation unit 20, in particular according to the timing of the measurement signal acquisition and / or as required, preferably in preparation for a track construction measure, during the track construction measure or immediately after the track construction measure.

[0106] The instantaneous temperature T of the track rail 2 can be determined using at least one temperature sensor 29. It can be approximated that the neutral temperature To corresponds to the reference temperature TR. The temperature difference AT can be determined as the difference between the instantaneous temperature T and the reference temperature TR, in particular using the evaluation unit 20. From the temperature difference AT, the longitudinal force N in the continuously welded track rail 2 can be deduced according to the equations above.

[0107] The neutral temperature To, i.e., the temperature at which the track rail 2 is thermally unstressed, is subject to changes in reality, so it can deviate from the reference temperature TR. A change in the position of the track rails 2, for example due to track construction work, in particular ballast compaction and / or track stabilization and / or a lifting and straightening process, and / or due to displacement caused by thermally induced expansion, in particular by track or curve breathing, and / or due to creep processes, can lead to a change in the neutral temperature To. One way to determine the change in the neutral temperature To is to measure the instantaneous expansion 8 of the track rail 2. This can be done using at least one expansion sensor 21. For a continuously welded track rail 2, the following equation can be used:

[0108]

[0109] The axial force N is therefore preferably determined based on the measurement signals of the at least one strain sensor 21 and the at least one temperature sensor 29. The instantaneous strain e can be determined directly from the measurement signals and / or taking into account the reference strain 8R, in the strain-free state of the track rail 2.

[0110] In particular, the axial force N can be determined with high precision by combining the strain e and the temperature change AT, especially relative to the respective reference value. This method also allows changes in the neutral temperature To to be taken into account or compensated for.

[0111] The longitudinal force N is not necessarily constant along the length of the track rail 2. For example, locally varying support forces, particularly across the track sleepers 6, can act on the track rails 2, especially due to differing lateral displacement resistances. The track rails 2 can also have different temperatures T due to locally varying humidity and / or shading. This means that locally determining the longitudinal force N, especially at a single evaluation point, can give an inaccurate picture of the load on the track rails 2 from longitudinal forces N. A value for the longitudinal force N that is too low could lead to the incorrect approval of track construction work and consequently to significant damage to the track.

[0112] To avoid this, several sensors 21, 29 are provided. By means of the several sensors 21, 29, which are spaced apart from each other along the longitudinal direction 30 of the rail, the longitudinal forces N can be determined at several evaluation positions.

[0113] Preferably, a substitute value NE is determined using statistical methods and based on several of the determined longitudinal forces N. The substitute value NE can be determined as the mean value and / or the maximum value and / or based on a standard deviation of the determined longitudinal forces N. The substitute value NE can thus provide a particularly reliable measure for deciding on the permissibility of a track construction measure.

[0114] The method described above is also suitable for determining the longitudinal force N in a jointed track. In a jointed track, the longitudinal force N cannot be directly derived from the temperature difference AT, as expansions 8 in the longitudinal direction 30 of the rail are possible. The longitudinal force N in a jointed track can be precisely determined using both the expansion e and the temperature T of the track rail 2. Track construction work can be controlled and / or initiated based on the determined longitudinal force N, in particular the equivalent value NE. For example, if the longitudinal force is below a predetermined limit and / or within a predetermined range, the track can be released for track construction work.

[0115] Controlling the track construction operation based on the longitudinal force N is particularly preferably carried out in such a way that the forces introduced into the track, especially the track rail 2, during the track construction operation do not lead to an overload of the track, especially the track rail 2. The loads acting on the track, especially the track rail 2, by the track construction operation can be limited by means of the longitudinal force N. Limiting the load can be carried out, in particular, depending on the type of track construction machine and / or on the condition of the track rail 2, especially its surface finish. For this purpose, the condition of the track rail 2, especially its surface finish, can be determined, for example, optically and / or by means of the linear detection device 19.The track construction work can be limited, for example, by restricting the lifting of the track grid 5, particularly during a lifting and alignment operation, to a specific height or position, especially above the track bed 7. The grinding of the track rail 2 can be limited to a specific maximum removal depth.

[0116] When controlling track construction measures, the type of track rail 2 can be taken into account, particularly with regard to the material, especially the modulus of elasticity, and / or the cross-section, especially the area moment of inertia. The type of track rail 2 has a particular influence on the load-bearing capacity and / or buckling resistance.

[0117] The method or measuring device 1.1 can also be used to determine the axial force N without knowledge of a reference temperature TR and / or a reference strain £R, ZU and / or to determine the reference temperature TR and / or the reference strain SRZU.

[0118] For this purpose, the vibration frequency f of the track rail 2 can be determined, in particular using the at least one measurement signal. Preferably, the vibration frequency f of a transverse vibration of the track rail 2 is determined. The vibration frequency f, in particular the square of the vibration frequency f, preferably correlates with, in particular is approximately directly proportional to, the longitudinal force N, in particular the quotient between the longitudinal force N and the product of the cross-sectional area A and the density p of the track rail 2, in particular according to the following equation:

[0119] f 2 ~N / (A * p).

[0120] The underlying principle is that the oscillation frequency f of track rail 2, similar to the frequency of a vibrating string of an instrument, provides information about the longitudinal force N. Alternatively, the longitudinal force N can be determined from the oscillation period of track rail 2, which is the reciprocal of the oscillation frequency, i.e., 1 / f. For a particularly precise determination of the longitudinal force N, correspondingly more complex analytical equations and / or FEM models can be used. The support reactions of the track sleepers 6 can thus be taken into account, for example.

[0121] The axial force N can be determined based on the vibration frequency f and / or the vibration period using the strain sensors 21 described above, in particular the measuring device 1.1.

[0122] Alternatively or additionally, particularly according to a further embodiment of the invention, the oscillation frequency f and / or the oscillation period can be determined by means of a separate, particularly mobile, measuring device 1.2. The measuring device 1.2 can have its own, particularly mobile, sensor unit 32 and / or its own, particularly mobile, evaluation unit.

[0123] Preferably, the mobile measuring device 1.2 is designed such that it can be carried by a measuring person 33. Preferably, the measuring device 1.2 has a weight of a maximum of 30 kg, in particular a maximum of 15 kg, in particular a maximum of 10 kg, in particular a maximum of 5 kg.

[0124] The mobile measuring device 1.2 can be reversibly connected to, in particular brought into contact with, the at least one track rail 2.

[0125] To generate vibration in the track rail 2, the track rail 2 can be subjected to a load. This load can be generated, for example, by a rail vehicle 9.1, 9.2, in particular a transport vehicle 9.1 and / or a track construction vehicle 9.2 and / or by a test actuator 34 of the measuring device 1.1, 1.2, in particular the mobile measuring device 1.2. The test actuator 34 preferably acts on the track rail 2 by contact, in particular by impact. The test actuator 34 is particularly preferably also designed as a vibration sensor 35.

[0126] The transport vehicle 9.1 can cause the track rail 2 to vibrate through the weight force G transmitted to the track rail 2 via the track wheels 11.

[0127] The track construction vehicle 9.2 can excite the track rail 2 to vibration, in particular by means of the lifting and aligning unit 26.1 and / or by means of the track tamping unit 26.2 and / or by means of the dynamic track stabilizer.

[0128] The vibration can also be generated by a manually operated testing tool, for example a test hammer 36.

[0129] The respective test force F exerted on the track rail 2 preferably has a force component oriented horizontally and / or perpendicular to the track rail 2, in particular it consists of this. This allows the detected transverse vibration to be excited particularly efficiently.

[0130] The method and measuring device 1.1, 1.2 ensure the determination of the longitudinal force N in track rails 2 with particularly high precision and efficiency, as well as high temporal and spatial flexibility. With precise knowledge of the longitudinal forces N, track construction measures can be planned and approved flexibly, which otherwise would not have been possible, particularly due to a lack of data or excessively high safety factors. This allows for increased utilization of track construction equipment, especially track construction vehicles 9.2, making the construction and maintenance of the rail transport system 3 particularly economical.

Claims

Patent claims 1. Method for determining the longitudinal load (N, To), in particular the longitudinal force (N), in a track rail (2), comprising the steps: 1.1 Acquiring at least one measurement signal which correlates with the longitudinal load (N, To) in the track rail (2), 1.2 Determining the longitudinal load (N, To) based on at least one measurement signal, characterized by the fact that 1.3 the longitudinal load (N, To) is determined on the basis of a vibration frequency and / or duration of the track rail (2) determined by means of at least one measurement signal.

2. Method according to claim 1, characterized in that the longitudinal load (N, To) is determined on the basis of a measurement signal from at least one deformation sensor (21) permanently connected to the track rail (2).

3. Method according to claim 1 or 2, characterized in that the longitudinal load (N, To) is determined on the basis of a measurement signal from at least one temperature sensor (29) permanently connected to the track rail (2).

4. A method according to any one of the preceding claims, characterized in that the longitudinal load (N, To) is determined on the basis of a measurement signal from at least one fiber optic sensor (21, 29) permanently connected to the track rail (2), in particular a fiber Bragg grating sensor.

5. A method according to any one of the preceding claims, characterized in that the longitudinal load (N, To) is determined on the basis of the measurement signals from several sensors (21, 29) permanently connected to the track rail (2), in particular from at least 50 sensors (21, 29) which are arranged spaced apart from one another along the track rail (2).

6. Method according to claim 5, characterized by determining a substitute value (NE) of the longitudinal load (N, To) based on the measurement signals of the multiple sensors (21, 29) and statistical methods, in particular averaging.

7. Method according to claim 5 or 6, characterized in that the multiple sensors (21, 29) are components of a linear detection means (19) which extends over a measuring section (31) along the track rail (2) with a length (L) of at least 100 m.

8. Method according to one of the preceding claims, characterized by loading at least one track rail (2) and determining the longitudinal load (N, To) based on at least one measurement signal recorded during loading.

9. Method according to claim 8, characterized by exciting a vibration of the track rail (2) by loading it in order to determine the vibration frequency and / or duration of the track rail (2).

10. Method according to claim 8 or 9, characterized in that at least one track rail (2) is loaded by means of a lifting and aligning unit (26.1) and / or a dynamic track stabilizer.

11. Method according to one of claims 8 to 10, characterized in that the at least one track rail (2) is loaded by the weight force (G) of a rail vehicle (9) traveling over the track rail (2).

12. Method according to one of the preceding claims, characterized by controlling a track construction measure based on the determined longitudinal load (N, To).

13. Method according to claim 12, characterized in that the control includes limiting the load exerted on the track rail (2).

14. Method according to claim 13, characterized in that the limiting of the load is carried out depending on a type of track construction machine and / or on the condition of the track rail (2).

15. A method according to one of the preceding claims, characterized by adjusting and / or calibrating a calculation method for determining the longitudinal load (N, To), in particular on the basis of measurement signals which are acquired at different temperatures and / or loads exerted on the track rail (2).

16. A measuring device (1.1, 1.2) for determining the longitudinal load (N, To), in particular the longitudinal force (N), in a track rail (2), comprising 16.1 at least one sensor (21, 29) for detecting at least one measurement signal which correlates with the longitudinal load (N, To) in the track rail (2), 16.2 an electronic evaluation unit (20) designed to determine the longitudinal load (N, To) based on at least one measurement signal, characterized by the fact that 16.3 the evaluation unit (20) is designed to determine a vibration frequency and / or duration of the track rail (2) based on the at least one measurement signal and to determine the longitudinal load (N, To) based on the vibration frequency and / or duration.

17. Measuring device (1.1, 1.2) according to claim 16, characterized in that the at least one sensor (21, 29) is a fiber optic strain sensor (21), in particular a fiber Bragg grating sensor.

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