Strain gauge assembly, particularly for an axle counter

Abstract

A method for assembling a strain gauge arrangement for an axle counter, includes: a strain sensor element; a carrier, to which the strain sensor element is fastened; and a railroad track structure to be monitored. When the carrier is fastened to the structure at least a part of it is kept in an elastically deformed state. The carrier is embodied with a first carrier piece opposing a second carrier piece. The strain sensor element is fastened to the first carrier piece with a first fixing point, to the second carrier piece with a second fixing point, and to neither the first nor the second carrier piece with a central section between the fixing points. At least the part of the carrier is elastically braced by means of a bracing element for when adhesively bonding to the structure to be monitored. Thereafter the bracing element is removed.

Claims

1. A method for assembling a strain gauge arrangement for an axle counter, the method comprising the steps of: a) providing at least one strain sensor element; b) providing a carrier, to which the strain sensor element is fastened; c) providing a structure to be monitored, being a railroad track, to which the carrier is fastened, wherein at least a part of the carrier is kept in an elastically deformed state by the structure when the carrier is fastened to the structure; d) embodying the carrier with a first carrier piece and a second carrier piece, which oppose one another in spaced apart fashion; e) fastening the strain sensor element to the first carrier piece with at least one first fixing point, to the second carrier piece with at least one second fixing point, and to neither the first nor the second carrier piece with a central section between the fixing points; f) elastically bracing at least the part of the carrier by means of a bracing element; g) keeping at least the part of the carrier in the elastically braced state by means of the bracing element and fastening the carrier to the structure to be monitored; and h) removing the bracing element.

2. The method as claimed in claim 1, wherein the bracing element is securely connected to the carrier before step f) and wherein the bracing element is broken off from the carrier for step f).

3. The method as claimed in claim 2, wherein following the assembly of one or more strain gauge arrangements, the bracing element which were broken off and removed in step h) are checked for completeness.

4. The method as claimed in claim 1, characterized in that the bracing element is securely connected to the carrier in steps f) and g) and wherein the bracing element is broken off from the carrier for step h).

5. The method as claimed in claim 4, wherein following the assembly of one or more strain gauge arrangements, the bracing element which were broken off and removed in step h) are checked for completeness.

6. The method as claimed in claim 1, including the step of using of the strain gauge arrangement to count axles.

7. The method as claimed in claim 1, wherein, when the part of the carrier which is kept in the elastically deformed state by the structure when the carrier is fastened to the structure comprises the first carrier piece and the second carrier piece, the elastically bracing at least of the part of the carrier includes elastically bracing the first carrier piece and the second carrier piece with respect to one another with at least a direction component along an extension direction of the strain sensor element.

8. The method as claimed in claim 7, wherein the first and second carrier piece are connected to one another by a bracket, wherein the bracket is spaced apart from the strain sensor element by a distance AS, where the following applies to the distance AS and a distance AE from the first to the second fixing point: AS≥1*AE.

9. The method as claimed in claim 8, wherein the carrier forms a bracing bearing, at or in which the bracing element, which engages on the first and second carrier piece, is arrangeable.

10. The method as claimed in claim 9, wherein during assembly the bracing element arranged at or in the bracing bearing is broken off from the carrier from the inner region of the bracing bearing.

11. The method according to claim 9, wherein the bracing bearing and bracing element interact in the style of a cam.

12. The method as claimed in claim 7, wherein the first and second carrier piece are connected to one another by a bracket, wherein the bracket is spaced apart from the strain sensor element by a distance AS, where the following applies to the distance AS and a distance AE from the first to the second fixing point: AS≥3*AE.

13. The method as claimed in claim 12, wherein the carrier forms a bracing bearing, at or in which the bracing element, which engages on the first and second carrier piece, is arrangeable.

14. The method as claimed in claim 13, wherein during assembly the bracing element arranged at or in the bracing bearing is broken off from the carrier from the inner region of the bracing bearing.

15. The method according to claim 13, wherein the bracing bearing and bracing element interact in the style of a cam.

16. The method as claimed in claim 7, wherein the carrier forms a bracing bearing, at or in which the bracing element, which engages on the first and second carrier piece, is arrangeable.

17. The method as claimed in claim 16, wherein during assembly the bracing element arranged at or in the bracing bearing is broken off from the carrier from the inner region of the bracing bearing.

18. The method according to claim 16, wherein the bracing bearing and bracing element interact in the style of a cam.

19. The method as claimed in claim 1, wherein in step a), the at least one strain sensor element is chosen as an optical fiber with a fiber Bragg grating.

20. The method as claimed in claim 1, wherein in step g), fastening the carrier to the structure to be monitored is done by adhesively bonding the carrier to the structure to be monitored.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is illustrated in the drawing and explained in more detail on the basis of exemplary embodiments. In the figures:

(2) FIG. 1a shows a schematic plan view of a first embodiment of a strain gauge arrangement according to the invention, with a frame-shaped base element;

(3) FIG. 1b shows a schematic cross-sectional view of the strain gauge arrangement of FIG. 1a;

(4) FIG. 2a shows a schematic plan view of a second embodiment of a strain gauge arrangement according to the invention, comprising a leaf spring element, support element and driver element;

(5) FIG. 2b shows a schematic side view of the strain gauge arrangement of FIG. 2a, comprising a carrier fastened to the structure;

(6) FIG. 2c shows a schematic side view of the strain gauge arrangement of FIG. 2a, comprising a carrier detached from the structure;

(7) FIG. 3 shows a schematic plan view of a third embodiment of a strain gauge arrangement according to the invention, with a bracket;

(8) FIG. 4a shows a schematic plan view of a fourth embodiment of a strain gauge arrangement according to the invention, comprising a cam that has not yet been broken out;

(9) FIG. 4b shows the strain gauge arrangement of FIG. 4a, with a spreading cam;

(10) FIG. 4c shows the strain gauge arrangement of FIG. 4b, following fastening to the structure and with the cam removed;

(11) FIG. 5a shows a schematic side view of a fifth embodiment of a strain gauge arrangement according to the invention, comprising a base element in the elastically relaxed, arched state;

(12) FIG. 5b shows the strain gauge arrangement of FIG. 5a, in the elastically deformed, flat state of the base element;

(13) FIG. 6a shows a schematic embodiment of a sixth embodiment of a strain gauge arrangement according to the invention, comprising application elements in contact with the strain sensor element;

(14) FIG. 6b shows the strain gauge arrangement of FIG. 6b, with the application elements disposed away from the strain sensor element;

(15) FIG. 7 shows a schematic embodiment of a seventh embodiment of a strain gauge arrangement according to the invention, comprising a fiber Bragg grating of the strain sensor element and a further fiber Bragg grating in a further strain sensor element;

(16) FIG. 8a shows a schematic embodiment of an eighth embodiment of a strain gauge arrangement according to the invention, comprising a bracket and securely connected bow-shaped bracing element, during fastening to a structure;

(17) FIG. 8b shows the strain gauge arrangement of FIG. 8a, following fastening to the structure, with a broken off bracing element;

(18) FIG. 8c shows the strain gauge arrangement of FIG. 8b, following a fall from the structure; and

(19) FIG. 9 shows a schematic view of an axle counter, comprising two strain gauge arrangements according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(20) FIG. 1a shows a first embodiment of a strain gauge arrangement 1 according to the invention in a plan view, and FIG. 1b shows an associated cross-sectional view, cf. plane lb in FIG. 1a.

(21) The strain gauge arrangement 1 comprises a carrier 2, which here comprises a substantially rectangular base element 3 that is closed in ring-shaped fashion, a first carrier piece T1, and a second carrier piece T2. The carrier pieces T1, T2 protrude inward from the base element 3, which forms an outer frame of the carrier 2.

(22) By way of the frame-shaped base element 3, the carrier 2 is fastened to a structure 4 to be monitored in a manner not shown in detail, e.g., it adhesively bonds to the structure 4 with the entire underside of the base element 3; however, the undersides of the carrier pieces T1, T2 are not adhesively bonded to the structure 4, but only rest on said structure 4. By way of example, the structure 4 to be monitored can be a railroad track of a train route.

(23) A strain sensor element 5 is fastened to the carrier pieces T1 and T2 at fixing points 7, 8. The fixing points 7, 8 each lie at the inner end of the pieces T1, T2. The central section 5a of the strain sensor element 5 located between the fixing points 7, 8 freely spans between the pieces T1, T2 in this case.

(24) In the embodiment shown, the strain sensor element 5 is embodied as an optical fiber 6 with a fiber Bragg grating (FBG) 6a in the central section 5a. It should be noted that the fiber 6 is only shown in the region of the central section 5a in FIG. 1a for simplification purposes; FIG. 1b also shows feed lines 6b of the fiber 6. Alternatively, other types of strain sensor elements, such as electrical resistance-measuring strips, could also be used.

(25) In a basic state for using the strain sensor element 5 for monitoring the strain of the structure 4, the strain sensor element 5 is typically slightly elastically strained in the direction of extension ER of the fiber 6 in the central section 5a in order to set the working point of the FBG. Here, the elastic strain of the strain sensor element 5 can be predetermined practically as desired when or by fastening the strain sensor element 5 to the fixing points 7, 8 (in the basic state).

(26) If there is a deformation of the structure 4, the base element 3 fastened to the structure 4 is also deformed. This deformation of the base element 3 is transferred to the strain sensor element 5 via the carrier pieces T1, T2, as a result of which this deformation becomes measurable.

(27) A total length GL of the pieces T1, T2, in each case from the rear region 9 to the front region 10 where the respective fixing point 7, 8 is arranged, with GL=LT1+LT2, is significantly longer than the distance AE between the fixing points 7, 8 in this case. In the embodiment shown, GL=2*AE applies approximately; in general, GL≥2*AE or GL≥3*AE is preferred. As a result of the pieces T1, T2 protruding parallel to the direction of extension ER of the strain sensor element 5, which pieces move when the structure 4 is deformed along the direction of extent ER but are themselves hardly deformed, the deformation of the structure 4 or the frame in the direction of extent ER can be transferred in reinforced fashion to the strain sensor element 5, in accordance with the ratio AE/(LT1+AE+LT2).

(28) In the basic state already mentioned, the frame-shaped base element 3 is in an elastically deformed state, in which it is kept by the underlying structure 4 to which the base element 3 is fastened. In the present case, the base element 3 is strained slightly elastically with respect to the direction of extent ER. Should the base element 3 or the carrier 2 fall off the structure 4, the elastic deformation of the base element 3 would spring back; i.e., the base element 3 would contract in the direction of extent ER in this case. This would also change the elastic strain state of the strain sensor element 5, as a result of which the fall-off from the structure 4 can be uncovered.

(29) In the further described embodiments of strain gauge arrangements, it is primarily the differences from the embodiment of FIGS. 1a, 1b that are explained.

(30) A second embodiment of a strain gauge arrangement 1 according to the invention is illustrated in a plan view in FIG. 2a and, in a side view, in the state fastened to the structure 4 in FIG. 2b and in the detached state in FIG. 2c.

(31) The strain gauge arrangement 1 has a carrier 2, which also comprises a leaf spring element 21 in addition to the pieces T1, T2. In the embodiment shown, the leaf spring element 21 connects the two carrier pieces T1, T2 to one another, the leaf spring element 21 being fastened with its ends 22, 23 to the pieces T1, T2 in each case; the end regions of the leaf spring element 21 extending over the pieces T1, T2.

(32) A support element 24 is formed on the leaf spring element 21, said support element extending over the strain sensor element 5 in this case and being supported with a support projection 24a on the structure 4 to be monitored as a stop partner. When the carrier 2 is fastened to the structure 4 (cf. FIG. 2b), the support element 24 presses the leaf spring element 21 away from the structure 4 in the upward direction, as a result of which the leaf spring element 21 is elastically deformed, specifically strained in this case.

(33) Moreover, a driver element 25 is formed on the leaf spring element 21, said driver element likewise extending over the strain sensor element 5 in this case and having a driver projection 25a which projects downward in the direction towards the strain sensor element 5 in this case. Thus, driver projection 25a engages behind the strain sensor element 5 from above. In state where the leaf spring element 21 is elastically deformed by the support on the structure 4 (cf. FIG. 2b), the driver element 25 (or its driver projection 25a) is raised so far in the embodiment shown that it does not touch the strain sensor element 5. Accordingly, the strain sensor element 5 has its normal strain state, which is provided for normal measurement operation (for strain monitoring of the structure 4).

(34) Should the strain gauge arrangement 1 fall off the structure 4, the leaf spring element 21 springs back into an elastically non-deformed state, which is shown in FIG. 2c, since the support element 24 no longer has a stop partner at the front end. In this state, the driver projection 25a of the driver element 25 presses on the strain sensor element 5 and impresses a significant elastic strain thereon. This significant elastic strain is easy to measure, as a result of which the strain gauge arrangement 1 falling from the structure 4 can easily be detected.

(35) In the embodiment of FIGS. 2a-2c, the carrier pieces T1, T2 or the carrier 2 can be fastened to the structure 4 to be monitored without any significant shear stress, which simplifies the assembly.

(36) FIG. 3 shows a third embodiment of a strain gauge arrangement 1 according to the invention in a schematic top view.

(37) In this case, the carrier 2 comprises the pieces T1, T2, to which the strain sensor element 5 is fastened at the fixing points 7, 8, and a bracket 31, which connects the pieces T1, T2 to one another at one end (the lower end in FIG. 3). The direction of extent ER of the strain sensor element ER extends parallel to the bracket 31 or its connecting direction.

(38) The carrier 2 is fastened to the structure 4 in an elastically deformed state, specifically with a certain mutual torsion of the pieces T1, T2, approximately around a joint region 32 in the middle of the bracket 31. The torsion acts approximately parallel to the direction of extension ER of the strain sensor element 5 in the region of the strain sensor element 5.

(39) Should the structure 4 fall off, this torsion springs back, as a result of which the strain state at the strain sensor element 5 changes. Both the pieces T1, T2 and the bracket 31 are involved in the torsion.

(40) The distance AS between the bracket 31 (or the upper part thereof) and the strain sensor element 5 is preferably significantly greater than the distance AE between the fixing points 7, 8 in order to be able to control the forces in the region of the strain sensor element 5 well. In the embodiment shown, approximately AS=3*AE applies; generally AS≥2*AE or AS≥3*AE is preferably chosen.

(41) If desired, the bracket 31 can be weakened in the joint region 32, for example by way of a notch 33. As a result, larger torsions can be produced with the same force, for example, which makes it easier to detect a fall-off from the structure. It is likewise possible to dispose a spring 34 or a plurality of springs 34 (tension or compression springs, as required) between the pieces T1, T2 in order to adjust the elastic behavior of the pieces T1, T2 with respect to one another.

(42) It should be noted that in this embodiment, too, the strain sensor element 5 can be freely spanned in the central section 5a, and an elastic strain state of the strain sensor element 5 in the basic state can, in principle, be freely determined.

(43) FIG. 4a shows a fourth embodiment of a strain gauge arrangement 1 according to the invention. In this case, the carrier 2 comprises the carrier pieces T1, T2, to which the strain sensor element 5 is fastened with the fixing points 7, 8, and a bracket 31, which connects the carrier pieces T1, T2. Prior to the assembly of the strain gauge arrangement 1, a bracing element 41, which is designed as a cam, is kept between the carrier pieces T1, T2. The bracing element 41 is typically made in one piece with the remainder of the carrier 2 (for example by laser cutting from a metal sheet) and is held at the remainder of the support 2 at two predetermined breaking points 42, between the carrier pieces T1, T2 in this case. In the situation shown in FIG. 4a, the carrier 2 is in an elastically relaxed state and has not yet been fastened to a structure. The long side of the bracing element 41 is aligned parallel to the carrier pieces T1, T2 or perpendicular to the direction of extension ER of the strain sensor element 5. The strain sensor element 5 hangs slack between the carrier pieces T1, T2; this state can easily be determined by a strain measurement.

(44) For the assembly on a structure 4 to be monitored, the bracing element 41 is broken off from the predetermined breaking points 42, for example by turning 43 the bracing element 41 as shown in FIG. 4a.

(45) As a result of half a rotation of the bracing element 41 or cam, the latter spreads the pieces T1, T2 apart (or applies torsion with respect to the carrier pieces T1, T2), as a result of which the carrier 2 assumes an elastically deformed state, cf. FIG. 4b. A bracing bearing 44 for the bracing element 41 is consequently set up between the inner sides of the carrier pieces T1, T2; a fixed axis of rotation 45 is typically set up for the bracing element 41. The strain sensor element 5 is tightened and receives a slight elastic strain, in accordance with the working point thereof. The long side of the bracing element 41 is aligned perpendicular to the carrier pieces T1, T2 or parallel to the direction of extension ER of the strain sensor element 5. In this spread state, the carrier 2 is fastened, for example adhesively bonded, to the structure 4 to be monitored.

(46) After fastening to the structure 4 (for example after an adhesive has cured), the bracing element can be removed, cf. FIG. 4c. For as long as the strain gauge arrangement 1 remains fastened to the structure 4, the elastically deformed state of the carrier 2 and the slight elastic strain of the strain sensor element 5 are also retained. Should detachment from the structure 4 occur, the strain gauge arrangement 1 would return to the elastically relaxed state shown in FIG. 4a, which could easily be measured by the slackening of the strain sensor 5.

(47) In the fifth embodiment of a strain gauge arrangement 1 according to the invention, shown schematically in a side view in FIG. 5a, the carrier 2 has a base element 3, with a closed area in this case, to which the pieces T1, T2 are fastened. In the shown elastically relaxed state of the base element 3, in which it is not fastened to a structure 4, the base element 3 is arched, as a result of which the pieces T1, T2 are close together and a strain sensor element 5 extending therebetween is slack, which is easy to measure.

(48) In the basic state shown in FIG. 5b, in which the carrier 2 is fastened, for instance adhesively bonded, to the structure 4 to be monitored (shown in dashed lines) by means of the base element 3, the base element 3 is kept in an elastically deformed state, a flat state in this case, and the strain sensor element 5 is tightened so that it can be used in its working range. In particular, deformations of the structure 4 along (or with a component along) the direction of extension ER of the strain sensor element 5 can be measured well.

(49) A sixth embodiment of a strain gauge arrangement 1 according to the invention is illustrated in an elastically relaxed state of a base element 3 of a carrier 2 in FIG. 6a and in an elastically deformed state of said base element 3 in FIG. 6b. Two application elements 61 are arranged or formed on the base element 3.

(50) In an elastically relaxed state of the base element 3, the latter assumes an arched state, as a result of which the application elements 61 press on the strain sensor element 5 in a central region 5a between the carrier pieces T1, T2 (the fastening of which to the rest of the carrier 2 has not been shown in detail for the sake of simplification), as illustrated in FIG. 6a, or even cut therethrough (not shown in detail). As a result, the strain sensor element 5 is temporarily or permanently impaired in an easily measurable manner. If the strain sensor element 5 is embodied as an optical fiber with a fiber Bragg grating, the reflection wavelength can be greatly detuned, for example by squeezing the fiber, or the attenuation of the fiber can be greatly increased.

(51) In an elastically deformed state of the base body 3, in this case, as shown in FIG. 6b, in a flat state of the base body 3 fastened to the flat structure 4 to be monitored, the application elements 61 are disposed distant from the strain sensor element 5 and do not impair the latter. Normal strain monitoring of the structure 4 can be carried out.

(52) FIG. 7 shows a seventh embodiment of a strain gauge arrangement 1 according to the invention. This includes a strain sensor element 5 and a further strain sensor element 71 in this case. The strain sensor element 5 is formed with a fiber Bragg grating 6a (also called a slave FBG or auxiliary FBG) (cf., e.g., FIG. 1a above in this respect), and the further strain sensor element 71 is formed with a further fiber Bragg grating 72 (also called master FBG or main FBG). The fiber Bragg grating 6a and the further fiber Bragg grating 72 are formed at different positions in the same optical fiber 6.

(53) In the case of the strain sensor element 5, the two carrier pieces T1, T2 are fastened via the bracket 31 to the structure 4 in an elastically deformed state in relation to the structure 4 to be monitored (cf., e.g., FIG. 3 above); to this end, an elastic tension was typically applied locally to the carrier 2 during fastening, for instance using a cam or another bracing element (not illustrated in more detail). Should the elastic deformation of the carrier 2 be lost in the monitored region of the strain sensor element 5, this would be recognized by a significant change in the strain state on the strain sensor element 5.

(54) At the further strain sensor element 71, the optical fiber 6 is fastened to carrier pieces T1′, T2′ with fixing points 74, 75 in this case, with the optical fiber 6 freely spanning between the fixing points 74, 75. The carrier pieces T1′, T2′ are also in this case interconnected by way of a bracket 73, but there is no local elastic bracing or deformation of the carrier 2 with respect to the structure 4. Thus, in the monitored region of the further strain sensor element 71, the carrier 2 transfers a deformation of the structure 4 without a tension offset by the local carrier 2.

(55) In the embodiment shown, the fiber Bragg grating 6a and the further fiber Bragg grating 72 have significantly different, non-overlapping reflection wavelength intervals. By way of example, the reflection wavelength of the fiber Bragg grating 6a (primarily depending on the deformation state of the local carrier 2) can be in the range of 720 nm to 670 nm, and the further reflection wavelength of the further fiber Bragg grating 72 (primarily depending on the strain state of the structure 4) can be in the range of 635 nm to 625 nm. Then, the correct fit on the structure 4 can be checked on the basis of the current reflection wavelength of the strain sensor element 5, and the deformation of the structure 4 can be checked on the basis of the current, further reflection wavelength of the further strain sensor element 71; both are measurable at the same time. Alternatively, the strain sensor element 5 or the strain gauge arrangement 1 could be set up in such a way that, in the event of falling off, the fiber Bragg grating 6a becomes non-transparent in the working range (corresponding to the entire further reflection wavelength interval) of the further fiber Bragg grating 72, which can easily be uncovered when an attempt is made to determine the reflection wavelength of the further fiber Bragg grating 72.

(56) Typically, the local parts of the carrier 2 are fastened in the same way in the monitored region of the strain sensor element 5 and in the monitored region of the further strain sensor element 71, and so an equal hold (for example as a result of aging) can generally be expected. Preferably, all parts of the carrier 2 are mechanically coupled to one another, in a manner not shown in detail, so that all parts of the carrier 2 behave in the same way (in particular all are fastened to the structure 4 or all fall-off therefrom).

(57) FIG. 8a shows an eighth embodiment of a strain gauge arrangement 1 according to the invention. The carrier 2 comprises the pieces T1, T2, to which the strain sensor element 5 is fastened at the fixing points 7, 8. Firstly, the pieces T1, T2 are securely connected to one another via a bracket 31 of the carrier 2, and, secondly, also securely connected to one another via a bow-shaped bracing element 81 in this case.

(58) The bracing element 81 forces an elastic deformation in the bracket 31, with the pieces T1, T2 being spread apart from one another in this case (or being twisted against one another, cf. the description of FIG. 3 above in the respect as well). In this state, the carrier 2 (with the pieces T1, T2 and the bracket 31 but not with the bracing element 81) is fastened, for example adhesively bonded, to a structure 4 to be monitored.

(59) After complete fastening, the bracing element 81 is removed; to this end, the bracing element 81 is broken off the carrier 2 at predetermined breaking points 82, cf. FIG. 8b. The elastically spread state of the bracket 31 is maintained by the structure 4 to which the carrier 2 is fastened. The regions of the fracture surfaces remaining on the carrier pieces T1, T2 can be considered to be a bracing bearing 83 for the bracing element 81.

(60) Should the strain gauge arrangement 1 fall off the structure 4, the bracket 31 subsequently assumes an elastically relaxed state. This is shown in FIG. 8c. As a result, the pieces T1, T2 approach each other and the strain sensor element 5 slackens. This is easy to measure on the strain sensor element.

(61) FIG. 9 illustrates in a schematic side view an axle counter 91 for the invention, which is fastened laterally to a railroad rail 92 (for instance to the so-called rail web) as structure 4 to be monitored. The axle counter 91 in this case comprises two strain gauge arrangements 1 according to the invention, each of which is formed in exemplary fashion in this case with two pieces T1, T2 and a bracket 31 connecting them (cf., e.g., FIG. 3). Trains whose train axles can be detected by the axle counter 91 can travel on the rail 92 in the direction of travel FR. The directions of extension ER of the strain sensor elements 5 run obliquely to the direction of travel FR, at an angle of approximately 45° in the embodiment shown. It should be noted that the direction of travel FR corresponds at the same time to the direction of a neutral fiber in the rail 92 or structure 4 under the load of the trains.

(62) If, for example, a train axle rolls from left to right in FIG. 9 above the axle counter 91, the left strain gauge arrangement 1 first registers a relative strain and then a relative compression in relation to a basic state (without a train crossing). Somewhat later, the right strain gauge arrangement 1 also registers a relative strain first, and then a relative compression in relation to the basic state. In the case of an opposite direction of travel, the sequence of events is reversed accordingly.

(63) A redundancy can be set up as a result of the two strain gauge arrangements 1 in the axle counter 91, improving safety in train operation. It should be noted that, in simpler embodiments, only one strain measuring arrangement may be provided in the axle counter 91.

LIST OF REFERENCE SIGNS

(64) 1 Strain gauge arrangement 2 Carrier 3 Base element 4 Structure to be monitored 5 Strain sensor element 5a Central section 6 Optical fiber 6a Fiber Bragg grating 6b Feed line 7 First fixing point 8 Second fixing point 9 Rear region 10 Front region 21 Leaf spring element 22 End (leaf spring element) 23 End (leaf spring element) 24 Support element 24a Support projection 25 Driver element 25a Driver projection 31 Bracket 32 Joint region 33 Notch 34 Spring 41 Bracing element (cam) 42 Predetermined breaking point 43 Direction of rotation 44 Bracing bearing 45 Fixed axis of rotation 61 Application element 71 Further strain sensor element 72 Further fiber Bragg grating 73 Further bracket 74 Fixing point 75 Fixing point 81 Bracing element (bow-shaped) 82 Predetermined breaking point 83 Bracing bearing (for bow-shaped bracing element) 91 Axle counter 92 Railroad track AE Fixing point spacing ER Direction of extension (strain sensor element) GL Total length of pieces T1, T2 FBG Fiber Bragg grating FR Direction of travel LT1 Length of piece T1 LT2 Length of piece T2 T1 First piece (strain sensor element) T1′ First piece (further strain sensor element) T2 Second piece (strain sensor element) T2′ Second piece (further strain sensor element)