JP3940740B2 - Crack detection system, adhesive and linear detector available in this system - Google Patents

Description

The present invention also relates to the crack detection system.

  Structures that are subjected to mechanical vibration such as bridges, vehicles, ships, aircraft, and machines may crack due to metal fatigue. There are various types of cracks, such as those generated from the inside of the structure, those generated from the surface, those that stop growing when grown to some extent, and those that gradually increase in growth rate. Early detection and countermeasures are necessary from the viewpoint of safety management.

Therefore, in the past, visual inspection was performed regularly or irregularly to detect cracks.
However, since visual inspection is based on the ability and attention of the inspector, there is a risk of missing a crack. In addition, fatigue cracks may grow during the inspection cycle, leading to destruction of the structure. In addition, inspection costs such as inspector salary and inspection scaffolding will be required.

In recent years, therefore, various monitoring systems have been developed to detect bridge cracks.
(1) In the “Bridge Continuity Health Monitoring System and Method”, as shown in FIG. 6, a plurality of optical fibers 6 are installed from the bridge 5 on one end side to each bridge 5, and the other side of each optical fiber is installed. It is determined that the bridge 5 is broken when the reflection mirror 60 is provided at the end, and the optical fiber 6 is also bent due to the bridge 5 being bent or the like, and the light incident on the optical fiber 6 from the light entrance 62 is not reflected and returned. (Patent Document 1).
(2) The “crack detection device”, as shown in FIG. 7, displays a mechanism 70 for pressure-feeding gas into the interior 7a of the structural member 7 and sealing it, a pressure sensor 72 for displaying the internal pressure, and an internal pressure. A display unit 74 is provided. The structural member 7 monitors the measured value P of the internal air pressure of the structural member 7 measured by the pressure sensor 72. When a crack occurs in the structural member 7 and the crack penetrates the plate pressure, the internal air pressure decreases, and the measured value P of the internal air pressure decreases. The occurrence of a crack is detected by determining from the display on the display unit 74 that a change in P displayed on the display unit 74 has occurred (Patent Document 2).
Japanese Patent Application 2000-133206 Japanese Patent Application 2000-026169

However, (1) “Bridge Continuity Health Monitoring System and Method” has a problem in terms of safety management because detection is performed only after a bridge is broken.
In addition, (2) the “crack detection device” is costly because the structural member has to be in a sealed space, and the crack cannot be detected unless there is a crack that causes a hole in the structural member. In addition, there is a problem that it is difficult to specify the location where the crack has occurred because it is not known where the air is leaking.

In this invention, to solve the problems described above, cracks occur and be found their place early, yet an object to provide a crack detection system having a simple structure.

The crack detection system according to claim 1, which has been made to solve the above-described problems, is wired in a state of being stacked on the surface of the detected object so as to be arranged along the surface of the detected object. The detection target is detected by detecting the presence or absence of disconnection of the detection line when two detection lines or a linear detector provided with the detection line are constantly energized from both ends of the detection line and the detection line is not energized. Crack detecting means for detecting the presence or absence of a crack due to metal fatigue of an object, and the crack detecting means performs an operation indicating an abnormality when the current applied to the detection line is interrupted by the disconnection of the detection line. And a holding means for holding the state after the operation, wherein the detection object is cracked, the detection line is de-energized, and the detection means is held to determine whether the holding means is held. this to detect the presence or absence of crack The features.

In the crack detection system of the present invention, two detection lines wired so as to be arranged along the surface of the object to be detected or a linear detector equipped with the detection lines are stacked on the surface of the object to be detected. The detection of the crack in the detected object is detected by constantly energizing the detection line by the crack detection means and detecting that the detection line is not energized.

Therefore, if this crack detection system is used, the occurrence of cracks in the detected object can be detected quickly.

 In the crack detection system according to claim 2, when the crack detection means detects the presence or absence of a crack in the detected object, the crack detection means specifies the disconnection position of the detection line using the TDR method. The location of the crack in the object is specified. Therefore, in the crack detection system of the present invention, it is possible to properly grasp the occurrence location of the crack of the detected object by using the TDR method. Moreover, the crack detection system of the present invention can be introduced at a low cost because it has a simple structure in which detection lines or linear detectors are simply stacked on the surface of an object to be detected.

 In the crack detection system of the present invention, the reason for using two detection lines is that the TDR
The principle of the method is that the potential difference is propagated in a pulsed manner between the two detection lines, and the measurement object such as the breaking point
Because it measures the time it takes to reflect off the surface and return,
This is because an insulated detection line is required.
In addition, as described in claim 3, the holding means may use a relay switch.

Next, as described in claim 4, the two detection lines or the detection lines wired in a state of being stacked on the surface of the object to be detected are arranged so as to be aligned along the surface of the object to be detected. A crack detector for detecting the presence or absence of a crack in the detected object by detecting the presence or absence of disconnection of the detection line due to inability to energize the detection line. And a crack location specifying means for detecting a break position of the detection line by a TDR method and identifying a crack occurrence location of the detection object when the crack detection means detects the presence or absence of a crack in the detection object. The detection line is made of a hard copper wire whose cross section perpendicular to the longitudinal direction is formed in a rectangular shape, and the surface on one side of the long side of the cross section faces the surface of the object to be detected. It is preferable that wiring is performed in such a state.
For example, a detection line having a circular cross section has a large vertical distance from the surface of the object to be detected to the surface facing the object to be detected, but when configured as in the present invention, the detection line is perpendicular to the cross sectional area. The distance can be reduced, and the wire breaks in response to a crack in the detected object with high accuracy. Therefore, if a detection line having a rectangular cross section is used, a crack in the detection object can be detected with high accuracy.

As described in claim 5, the detection line is preferably formed of a coated copper wire having a diameter of 0.30 mm or less. If this coated copper wire is used, it breaks in response to a crack in the bridge, so that the occurrence of a crack in the detected object can be detected with high sensitivity.

As described in claim 6, it is preferable that the two detection lines or the linear detection tool provided with the detection lines are wired on the detection object in a one-stroke manner through the assumed crack. Although it is conceivable to detect a crack by wiring a detection line etc. to each of the cracks that are supposed to be detected (such as the start and end of the welded part or the shape change part), It is less costly to wire through the assumed crack location and the location of the crack occurrence can be specified by the TDR method, so that the location of the crack occurrence in the detected object can also be detected accurately.

As described in claim 7, the two detection lines or the linear detection tool including the detection lines are laminated on an object to be detected using an adhesive having a longitudinal elastic modulus of 300 MPa or more when cured. Is preferred. When this adhesive is used, if a crack occurs in the detected object, a crack is generated correspondingly. Therefore, compared with the case where an adhesive having a longitudinal elastic modulus of 300 MPa or less is used, the crack of the detected object is greatly reduced. It can be detected with high sensitivity. Examples of the adhesive of 300 MPa or more include an epoxy adhesive and a cyanoacrylate adhesive .

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[First embodiment]
FIG. 1 is an overall view of a pier to which the crack detection system according to the first embodiment is applied. In FIG. 1, (a) to (e) illustrate a crack measurement procedure in time series. FIG. 2 is a graph for explaining the experimental results for specifying the adhesive to be used, and is a graph with longitudinal elastic modulus and crack passage distance as parameters.

  As shown in FIG. 1, the crack detection system 1 of the first embodiment is a system for detecting a crack in a bridge 5 that is an object to be detected, and includes two lines arranged along the surface of the bridge 5. A detection line 10 and a crack location identification device 20 are provided.

  The detection wire 10 is a covered electric wire having a diameter of 0.30 mm covered with a hard copper wire (a hard copper wire defined by the electrical copper wire and aluminum wire test method of JIS C 3002). Then, as shown in FIG. 1 (a), two detection lines 10 arranged in parallel are wired in a single stroke on the surface of the bridge 5 so as to pass through the assumed crack portion of the bridge 5, and when cured, 300 MPa. It adhere | attaches on the surface of the bridge 5 with the epoxy resin-type adhesive agent used as the above hardness.

  The crack location identification device 20 is a TDR (Time Domain Reflectometry) type detector. Here, the TDR method propagates micropulses intermittently transmitted by an electronic circuit to the detection line 10, receives the micropulses reflected on the surface of the measurement object such as the breaking point and transmitted again through the detection line 10, The distance from the transmission point to the breaking point is measured by measuring the round-trip time to the measurement object of the pulse. In the present embodiment, CFL535F TDR2000 / 2 manufactured by MEGGER is used.

When detecting a crack in the bridge 5 using the crack detection system 1 of the present embodiment, the following procedure is used.
As shown in FIG. 1B, when the train passes through the bridge 5 many times, a crack may occur at a portion where the crack is assumed to be structurally brittle, such as a welded portion (the portion where the symbol x is sold). When a crack occurs at the assumed crack location, the detection line 10 is disconnected along with the crack. When inspecting whether a crack has occurred in the bridge 5, as shown in FIG. Connected to the detection line 10, micro pulses are intermittently transmitted to the detection line 10 to detect the presence or absence of cracks.

  If a plurality of cracks are generated in the bridge 5, the detection line 10 is disconnected at the closest crack generation position along the wiring direction of the detection line 10 as viewed from the crack location identification device 20. Therefore, the micro pulse is reflected there, and the crack occurrence location is specified by the crack location specifying device 20.

  When the location where the crack is generated can be identified, the worker connects the disconnected detection line 10 with the jumper line 10a as shown in FIG. Then, a crack occurrence location farther than the closest crack occurrence location as seen from the crack location identification device is also detected.

Finally, as shown in FIG. 1 (e), the jumper wire 10b is also installed at a distant crack detection occurrence location, and once another crack is detected, the detection is terminated.
When detecting a crack, as shown in FIGS. 1C, 1D, and 1E, if a loading train / vehicle or the like is placed on the bridge 5, a load is applied to the bridge 5 and the crack opens. Since the detection line 10 that has been disconnected once does not come into contact again, the disconnection point of the detection line 10, that is, the crack generation point of the bridge 5 can be properly grasped. There is an effect like this.

  In this crack detection system, two detection lines 10 wired so as to be arranged along the surface of the bridge 5 are stacked on the surface of the bridge 5 and detected by the crack location identification device 20 using the TDR method. The occurrence position of the crack in the bridge 5 is specified by specifying the disconnection position of the line 10. Therefore, in the crack detection system 1 of the present embodiment, it is possible to properly grasp the crack occurrence location of the bridge 5 by using the TDR method. Moreover, since the crack detection system 1 of the present embodiment has a simple structure in which the detection line 10 is simply stacked on the surface of the bridge 5, it can be introduced at a low cost.

If a coated copper wire having a diameter of 0.30 mm or less is used as the detection line 10, it breaks in response to a crack in the bridge 5, so that the occurrence of a crack in the bridge 5 can be detected with high sensitivity.
In order to detect the occurrence of cracks in the bridge 5, it is conceivable to detect the cracks by wiring the detection lines 10 to each of the assumed cracks of the bridge 5 (such as the start and end portions of the welded portion and the shape change portion). In addition, it is less costly to wire the bridge 5 through the assumed crack location in a single stroke, and the location of the crack occurrence in the bridge 5 can be accurately detected because the crack occurrence location can be specified by the TDR method.

  In the present embodiment, the detection line 10 is laminated on the bridge 5 using an adhesive having a longitudinal elastic modulus of 300 MPa or more when cured. When this adhesive is cracked in the bridge 5, cracks are generated in response to the crack. Therefore, the crack in the bridge 5 should be detected very sensitively compared to the case where an adhesive having a longitudinal elastic modulus of 300 MPa or less is used. Can do.

By the way, in the said embodiment, although the longitudinal elastic modulus used the adhesive agent of 300 Mpa, this is based on the following reasons.
As shown in the model diagram circled in FIG. 2, FIG. 2 shows a detection line having a diameter of 0.08 mm in a resin as an adhesive from a target to be detected (a bridge in the present embodiment). (0.08 mm and 0.58 mm) It was buried in the height, and the relationship between the crack passage distance (the distance that the crack passed across the detection line 10) and the longitudinal elastic modulus was examined. According to the experiment of FIG. 2, since the slope of the graph is steep at around 300 MPa, in this embodiment, an adhesive having a longitudinal elastic modulus of 300 MPa or more was used during curing.

  When a fatigue crack occurs in a metal structure, the crack progresses little by little each time the load is repeated, and suddenly breaks down when it reaches a certain length. This certain length is called “limit crack length”. Therefore, from the standpoint of maintaining the structure, it is necessary to find a crack before the crack progresses to the limit crack length. When this is applied to the present embodiment, if the total length from the position where the crack start point is assumed to the crack passing distance past the detection line installation position is less than the limit crack length, the crack can be detected safely. It will be possible. The parameters in FIG. 2 are (1) crack passage distance (vertical axis), (2) longitudinal elastic modulus (horizontal axis), and (3) resin thickness, so (1) is initially set in relation to the limit crack length, The combination of (2) and (3) can be arbitrarily changed. In addition, it is thought that the limit crack length is 20 mm or more under normal steel materials and use conditions. On the other hand, when the longitudinal elastic modulus is less than 300 MPa, the crack passage distance is abruptly increased to 5.0 mm or more. For safety reasons, it was considered that a material having a longitudinal elastic modulus exceeding 300 MPa should be used.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, about this embodiment, only a different point from 1st Embodiment is demonstrated.

Here, FIG. 3 is an overall view of the pier to which the crack detection system of the second embodiment is applied, and illustrates a crack measurement method in time series in (a) to (f).
In the second embodiment, as shown in FIG. 3 (a), the two detection lines 10 are laid in parallel in one stroke through the assumed crack, but the crack is the same as in the first embodiment. Before using the place identification apparatus 20, the point which uses the crack detection apparatus 30 differs.

  In this crack detection device 30, one of the two detection lines 10 is always energized from one end side to the other end side, and the current applied to the detection line 10 is disconnected from the detection line 10. When the relay switch is cut off, the relay switch performs an operation indicating an abnormality and maintains the state after the operation.

  As shown in FIG. 3 (b), when the crack is generated in the pier 5 as shown in FIG. 3 (b), the detection wire 10 is turned off and the relay switch is turned on as shown in FIG. 3 (c). Retained. Therefore, since this crack detection device 30 detects the occurrence of a crack in the bridge 5 depending on whether or not the detection line 10 becomes unenergized, the crack in the bridge 5 can be detected quickly.

  In the following, as in the first embodiment, the crack location identification device 20 is attached to the detection line 10 and, as shown in FIG. As shown in FIG. 3, the jumper wire 10a is connected to the portion where the detection line 10 is disconnected, and another location is specified. As shown in FIG. 3 (f), the jumper wire 10b is connected, and a crack is detected. After confirming that it has disappeared, the crack detection work is finished.

Although the crack location identifying device 20 can detect the presence or absence of a crack, the TDR method is more expensive than the relay-type crack detection device 30 and the TDR2000 / 2 is a device that is currently available. Can only be measured three times per second due to the specifications, and there is a risk of missing a momentary disconnection that occurs when a train or the like passes (this fault can be eliminated by improving the equipment), so the relay circuit The method used is also proposed.
[Third embodiment]
Next, a third embodiment of the present invention will be described. In addition, about this embodiment, only a different point from 1st Embodiment and 2nd Embodiment is demonstrated.

4 is a cross-sectional view of the linear detector, and FIG. 5 is a plan view thereof.
This embodiment is different from the first and second embodiments in that the detection line 10 itself is not laminated on the bridge 5 but the linear detector 40 is laminated on the bridge 5.

  As shown in FIG. 4, the linear detector 40 detects parallel cracks generated in the bridge 5, and the parallel detection lines 11 wired along the surface of the bridge 5 and the bridge facing the bridge 5. And a pair of films 41 disposed on the opposite side, and an adhesive 42 made of a material having a longitudinal elastic modulus of 300 MPa or more is injected between the pair of films 41 at the time of curing. And the detection line 11 are bonded together. The film 41 also has a longitudinal elastic modulus of 300 MPa or more. Similar to the first embodiment, the linear detection tool 40 is bonded to the bridge 5 using an adhesive having a longitudinal elastic modulus of 300 MPa or more when cured, and performs crack detection.

  Since the detection line 11 is protected by the film 41, the linear detection tool 40 can prevent rusting by being wet with rain, and is more resistant to weathering than when the detection line 11 itself is laminated on the bridge 5. Will improve. In addition, the linear detection tool 40 has a structure in which the detection line 11 is sandwiched between films 41, and as shown in FIG. It is suitable for wiring with a single stroke, because it can be bent and wired to change the direction of attachment. Furthermore, when the linear detection tool 40 of the present embodiment is used, it is possible to stack the detection lines in parallel by one stacking as compared to stacking the two detection lines independently. In addition, it is easier to handle than two detection lines, because it is less likely to accidentally cut during the stacking operation.

  By the way, in the linear detection tool 40 of the present embodiment, a hard copper wire having a rectangular cross section perpendicular to the longitudinal direction is used as the detection line 11. When the shape detector 40 is laminated on the bridge 5, the surface on one side of the long side of the cross section is wired in a state of facing the surface of the bridge 5. The detection line 11 having a circular cross section has a large vertical distance from the surface of the detection object to the surface facing the detection object, but the detection line 11 can reduce the vertical distance with respect to the cross-sectional area. The wire breaks in response to a crack in the object to be detected with high accuracy. Therefore, if the detection line 11 having a rectangular cross section is used, a crack in the bridge 5 can be detected with high accuracy.

The embodiment of the present invention is not limited to the above-described embodiment, and it goes without saying that various forms can be adopted as long as it belongs to the technical scope of the present invention.
For example, in the above-described embodiment, the case of detecting a crack in the bridge 5 has been described. However, the present invention can be used as a system for detecting a crack in any type of structure such as an aircraft partition wall, body, or building wall. Of course.

Moreover, in the said embodiment, although the epoxy-type adhesive agent was used as an adhesive agent, there exist a cyanoacrylate type adhesive agent etc. as an adhesive agent of 300 Mpa or more.
Moreover, in the said embodiment, although the covered electric wire which coat | covered the hard copper wire was used as a detection wire, an enamel wire (covered copper wire which coat | covered the soft copper wire), a bare hard copper wire, an annealed copper wire, etc. may be sufficient. Further, an aluminum wire may be used, and any material may be used as long as it can be used as the detection wire of the present embodiment.

  Further, the shape may be a ribbon line, a square line, or any shape as long as the function of the present embodiment is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS It is the whole figure of the pier to which the crack detection system of 1st Embodiment was applied, (a)-(e) demonstrates the measurement procedure of a crack time-sequentially. It is a graph for demonstrating the experimental result for specifying the adhesive agent to be used, and is a graph which uses a longitudinal elastic modulus and a crack passage distance as parameters. It is a general view of the pier to which the crack detection system of a 2nd embodiment was applied, and (a)-(f) explains the measurement procedure of a crack time-sequentially. It is sectional drawing of a linear detection tool. It is a top view which shows a mode that the linear detection tool was bent. It is explanatory drawing of a prior art. It is explanatory drawing of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Crack detection system, 5 ... Bridge, 10, 11 ... Detection line, 20 ... Crack location identification device, 30 ... Crack detection device, 40 ... Linear detection tool, 41 ... Film, 42 ... Adhesive

Claims (7)

Two detection lines wired in a state of being stacked on the surface of the object to be detected so as to be aligned along the surface of the object to be detected, or a linear detector provided with this detection line,
Crack detection means for detecting the presence or absence of cracks due to metal fatigue of the detected object by constantly energizing from both ends of the detection line and detecting the presence or absence of disconnection of the detection line due to the inability to energize the detection line;
With
The crack detection means includes
When the current applied to the detection line is interrupted by the disconnection of the detection line, an operation indicating an abnormality is performed, and holding means for holding the state after the operation is provided.
A crack detection system for detecting the presence or absence of a crack in the detected object based on whether or not the detected object is cracked and the detection line is de-energized and the holding means is held . The crack detection system according to claim 1,
If the crack detection means detects the presence or absence of a crack in the detected object, the crack location specifying means for detecting the breakage position of the detection line by the TDR method and specifying the crack occurrence position of the detected object
Crack detection system comprising: a. In the crack detection system according to any one of claims 1 and 2,
  The crack detection system, wherein the holding means is a relay switch. Two detection lines wired in a state of being stacked on the surface of the detection object so as to be aligned along the surface of the detection object, or a linear detector provided with the detection lines;
A crack detection means for detecting the presence or absence of cracks in the detected object by constantly energizing from both ends of the detection line and detecting the presence or absence of disconnection of the detection line due to the inability to energize the detection line;
When the crack detection means detects the presence or absence of a crack in the detected object, a crack location specifying means for detecting the break position of the detection line by the TDR method and specifying the crack occurrence location of the detected object;
With
The detection line is made of a hard copper wire having a cross section perpendicular to the longitudinal direction formed in a rectangular shape, and the surface on one side of the long side of the cross section faces the surface of the object to be detected. A crack detection system characterized by being wired. In the crack detection system in any one of Claims 1-4 ,
The crack detection system, wherein the detection line is formed of a coated copper wire having a diameter of 0.30 mm or less. In the crack detection system according to any one of claims 1 to 5 ,
The crack detection system characterized in that the two detection lines or the linear detection tool provided with the detection lines are wired on the detected object in a single stroke through the assumed crack portion of the detected object. . In the crack detection system in any one of Claims 1-6 ,
A crack detection system, wherein the two detection lines or the linear detection tool having the detection lines are laminated on a detection object using an adhesive having a longitudinal elastic modulus of 300 MPa or more when cured.