JP2007163390A - Method and device for detecting defect of structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely detect defects of a large structure from a remote position with a simple device configuration, without having to construct scaffolds for detecting defects, a heating means such as infrared irradiation, and an applying means for a load to a structure, such as an excitation system. <P>SOLUTION: Stress fluctuations are generated, by applying a moving load 7 to the structure 1 of an object to be detected; temperature distribution fluctuation in the structure 4 is generated by the thermoelastic effects or plastic heat generation, depending on the stress fluctuations are measured as a thermal image; the stress fluctuations are grasped, based on the temperature distribution fluctuations; and then defects of the object are detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a structure, in particular, a defect such as a load handling machine or a large steel structure such as a bridge that causes a defect when the load moves, such as surface cracks, internal cracks, and corrosion from a distance without approaching the measurement target site. The present invention relates to a defect detection method and apparatus for a structure to be detected.

  The aging of large structures such as bridges, cranes and conveyors, and cargo handling machines has become a social problem, and there is a strong need for this countermeasure. In order to implement effective countermeasures against aging, it is first determined to know the degree of aging. For this reason, it is necessary to detect a defect in the target structure, and color check, magnetic flaw detection, ultrasonic flaw detection, and the like have been conventionally performed as means for the detection.

  However, methods such as color check, magnetic flaw detection, and ultrasonic flaw detection cannot be measured unless a person approaches to the vicinity of the measurement object in order to perform necessary treatments. For example, in magnetic flaw detection, it is necessary to apply a magnetic field after removing rust and the like in the detection area to obtain a measurable surface property. For this reason, in the case of a large structure, it is impossible to perform an operation unless a scaffold is assembled for inspection and preparations for work at a high place are made and a worker's hand reaches the inspection area. As a result, the work of building a scaffold has to spend more manpower and money than the cost of detecting defects.

  Under such circumstances, an infrared thermograph method using an infrared camera has been proposed in recent years in order to realize remote measurement, and for the convenience of inspecting a wide area at a time. For example, as a means of detecting cracks and delamination of concrete walls inside a tunnel, the tunnel wall surface is heated by some heat source instead of the conventional diagnostic method using a hammering test, and the defective part is identified from the difference in temperature distribution of the normal part. A detection method is used. As a prior art of an active method using these infrared cameras, for example, Patent Document 1 discloses that internal defects of a structure are measured by measuring a temperature distribution using means for uniformly irradiating a concrete structure with infrared rays. A method of detecting is disclosed.

  Patent Document 2 discloses a defect identification method using a difference image between temperature distribution images before and after heating and a difference between healthy and unhealthy sample thermal images for a steel structure.

  From another viewpoint, for example, as a method for detecting a crack generated in a test piece during processing of a metal material, a method using an infrared image using a thermoelastic property of the material is disclosed in Patent Document 3.

  However, the methods described in Patent Documents 1 and 2 are premised on infrared irradiation for heating, and this method can be applied to an object having a relatively low thermal diffusion rate such as concrete. For a steel structure having a high diffusion rate, it is difficult to create a temperature distribution that can be detected by an infrared camera unless infrared rays are irradiated from a close distance. For this reason, means for approaching the measurement object is necessary to perform heating, and it is necessary to assemble a scaffold as well as the above-described methods such as color check, magnetic flaw detection, and ultrasonic flaw detection.

In the above-mentioned Patent Document 3, a thermal image is taken with an infrared camera in order to detect a crack generated in association with plastic deformation during processing such as pressing or punching a metal material, and this technique is used. Is applied to the detection of defects in large structures, it is not only necessary to separately prepare a large-scale vibration device for positively causing load load fluctuations. Naturally, the load must be in a range that does not cause further damage to the structure, so the temperature change is very small. To capture the temperature change with a thermal image, use multiple thermal image data. A complicated operation is unavoidable, and the apparatus becomes complicated, and it is difficult to detect defects in a wide range from a remote location.
JP 2003-185608 A Japanese Patent Application Laid-Open No. 2004-37201 JP-A-10-82726

  The present invention has been made in view of such circumstances, and even for large structures such as bridges and various cargo handling machines, defects such as surface cracks can be formed without assembling a scaffold for defect detection work. It is possible to detect easily and reliably from a remote location with a simple device configuration without the need for heating means such as infrared irradiation and without the need for applying load load to structures such as vibration devices. An object of the present invention is to provide a defect detection method and apparatus for a structure.

  As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention have a thermoelastic effect if a stress is applied by a moving load applied during actual use in a large structure such as a cargo handling machine such as a bridge or a crane. Alternatively, the present inventors have found that temperature fluctuations based on plastic heat generation can be increased, and defects can be easily and reliably detected from a remote location using a thermal image from an infrared camera.

  This invention is made | formed based on such knowledge, and provides the following (1)-(13).

  (1) A stress variation is generated by applying a moving load to the structure to be detected, and a temperature distribution variation generated in the structure due to a thermoelastic effect or plastic heat generation due to the stress variation is measured as a thermal image. A defect detection method for a structure characterized by grasping a stress fluctuation based on a temperature distribution fluctuation and detecting a defect of the measurement object.

  (2) The moving amount or moving speed of a moving object that causes a moving load, or information correlated with the moving amount or moving speed is captured at the same time as the thermal image, and the moving amount or moving speed of the moving object, or the moving amount or moving speed. The defect detection method for a structure according to (1), wherein a defect of the structure is detected by using a thermal image that varies in synchronization with the information having a correlation with the reference signal as a reference signal.

  (3) The moving object image that causes the moving load is simultaneously captured in the thermal image, the moving amount or moving speed of the moving object is estimated from the thermal image, and this is used as a reference signal to synchronize with this. The defect detection method for a structure according to (1), wherein a defect of the structure is detected by using a thermal image that fluctuates in this manner.

  (4) Capture the reference signal and the thermal image, and detect a structural defect in the thermal image by finding a local peak value of the temperature change that is correlated with the reference signal in the thermal image. (2) or the defect detection method for a structure according to (3).

  (5) Taking in the reference signal and the thermal image, and finding a local and steep temperature change portion of the temperature change that is correlated with the reference signal in the thermal image, thereby causing a defect in the structure in the thermal image. The defect detection method for a structure according to (2) or (3), wherein the defect is detected.

  (6) The structure defect detection method according to any one of (1) to (5), wherein the moving load moves along the structure.

  (7) The structure defect detection method according to any one of (1) to (6), wherein the structure is a bridge or a cargo handling machine.

  (8) An infrared camera that photographs the structure in a state where a moving load is applied to the structure to be detected by a moving object, and a thermoelastic effect or plasticity from a temperature distribution variation in a thermal image captured by the infrared camera. An apparatus for detecting a defect in a structure, comprising: an information processing unit that calculates a stress fluctuation of an imaging region of the structure based on heat generation, and detects a defect of the structure from the calculated stress fluctuation.

  (9) The information processing unit captures, together with the thermal image, the moving amount or moving speed of the moving object that generates the moving load, or information correlated with the moving amount or moving speed, and the moving amount or moving speed of the moving object; Alternatively, the structure described in (8) is characterized in that a defect of a structure is detected using a thermal image that varies in synchronization with information having a correlation with a moving amount or a moving speed as a reference signal. Defect detection device.

  (10) The structure according to (9), further comprising a sensor that detects a movement amount or movement speed of the moving object that generates the moving load, or information correlated with the movement amount or movement speed. Defect detection device.

  (11) The information processing unit simultaneously captures the moving object image causing the moving load into the thermal image, estimates the moving amount or moving speed of the moving object from the thermal image, and uses this as a reference signal The defect detection device for a structure according to (9), wherein a defect in the structure is detected using a thermal image that fluctuates in synchronization with the above.

  (12) The information processing unit captures the reference signal and the thermal image, finds a local peak value of the temperature change that is correlated with the reference signal in the thermal image, and thereby the structure in the thermal image. The defect detection apparatus for a structure according to any one of (9) to (11), wherein the defect is detected.

  (13) The information processing unit takes in the reference signal and the thermal image, and finds a local and steep temperature change portion of the temperature change that is correlated with the reference signal in the thermal image. The defect detection device for a structure according to any one of (9) to (11), wherein a defect of the structure inside is detected.

  According to the present invention, a moving load is applied to a structure to be detected to cause a stress fluctuation, and a temperature distribution fluctuation generated in the structure due to a thermoelastic effect or plastic heat generation due to the stress fluctuation is measured as a thermal image. Based on this, since the defect of the object to be measured is detected, it is possible to measure the defect without the need for a heating means such as infrared irradiation without forming a scaffold for defect detection work, and in a stationary state. The stress fluctuation can be made larger than the load load, and the defect can be detected with higher accuracy. In addition, a moving load is originally planned for a large structure such as a bridge or crane, which is the subject of the present invention, and stress fluctuations are generated using the planned moving load. Without requiring special load application means such as a vibration device, a defect in the structure can be detected with a simple device configuration.

  Conventionally, the thermoelastic effect of structures has been used as a means of visualizing the stress state, but has not been used for detecting defects in structures, especially for detecting defects in large steel structures. Even if a change was given, the temperature change caused by the change was so small that it could not be captured as a thermal image. On the other hand, by applying a moving load as in the present invention, a thermoelastic effect, etc. for a metal having a good thermal diffusibility such as a steel structure in combination with a recent improvement in the performance of an infrared camera. It became possible to detect defects using.

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a state in which a defect of an overhead crane is detected by the method according to the first embodiment of the present invention.

  The overhead crane 1 has a girder 4 on which a crane carriage 7 travels. The girder 4 is movable along a girder traveling rail 5 laid on a building 6. The crane carriage 7 moves on the girder 4 along its longitudinal direction with the load 8 suspended. An infrared camera 9 for taking a thermal image of the girder 4 is arranged on the ground, and information from the infrared camera 9 is taken into the information processing unit 10 where predetermined processing for detecting defects is performed.

  When detecting a defect in the girder 4 of the actual overhead crane 1, first, the infrared camera is set on the ground so that the distance to the girder 4 is a predetermined distance, for example, about 10 to 20 m, and the load 8 is suspended. The crane cart 7 is moved over the girder 4 in the same manner as when the crane is operated. As a result, a stress fluctuation occurs in the girder 4 and a slight temperature distribution fluctuation occurs due to the thermoelastic effect or plastic heat generation associated therewith. The infrared camera 9 takes a thermal image of the girder 4 at this time and transmits the information to the information processing unit 10. In the information processing unit 10, the information is taken into the personal computer 11, and based on the thermoelastic effect or plastic heat generation from the temperature distribution variation on the thermal image measurement surface 3 on the girder 4 photographed by the infrared camera 9, the imaging part of the structure is photographed. The stress variation is calculated, the size and position of the defect S are detected based on the result, and a defect detection screen at that time is displayed on the display unit (display) 12. If the defect S is large or the stress concentration is sufficient, it is possible to detect a defect such as a crack that appears as a temperature fluctuation portion from a real-time thermal image by the above configuration. If the defect detection location is far away, a telephoto lens is used.

  By applying the moving load in this way, the stress fluctuation can be increased more than the stationary load load, and the temperature change can be increased accordingly, so the thermoelastic effect or plastic heat generation is utilized. It is possible to accurately grasp defects such as cracks. In addition, a moving load is originally planned for a large structure such as a bridge or crane, which is the subject of the present invention, and stress fluctuations are generated using the planned moving load. Without requiring special load application means such as a vibration device, a defect in the structure can be detected with a simple device configuration.

  However, in the case of an initial crack or when the moving load is relatively light, it may be difficult to clearly recognize a temperature distribution change based on a defect only with the above configuration. Therefore, the second and third embodiments below show a method in which a defect can be detected by clarifying the difference between a temperature fluctuation portion (that is, a defect occurrence portion) and a normal portion even in such a case.

  In the second embodiment, as shown in FIG. 2, a laser displacement meter 13 is provided on the crane carriage 7, a reflecting plate 14 is provided on the end of the girder 4, and a laser displacement meter is reflected from the laser reflected by the reflecting plate 14. The detection signal detected by 13 is transmitted to the lock-in processor 15 provided in the information processing unit 10, and the movement amount or movement speed of the crane carriage 7 obtained from this detection signal is taken into the personal computer 11 at the same time as the thermal image. As a signal, a thermal image that fluctuates in synchronization with this is taken out and displayed on the display unit (display) 12. In the lock-in processor 15, the relationship between the reference signal and the thermal image information (temperature data) is as shown in FIG. 3. By measuring the thermal image information in synchronization with the reference signal, the temperature fluctuation amplitude In addition, the defect is detected based on the phase shift, and this can reduce the influence of the temperature fluctuation that has no correlation with the reference signal. Therefore, the S / N ratio of the signal can be improved by using the reference signal and the lock-in processor 15.

  In the third embodiment, as shown in FIG. 4, the crane carriage 7 as a moving object that causes the movement load fluctuation is included in the thermal image measurement surface 3 ′ (that is, the image of the crane carriage 7 is included in the photographed image of the infrared camera 9. A wheel is taken in), a moving amount or moving speed is estimated from moving object data in the image, and this is used as a reference signal, and a thermal image that fluctuates in synchronization with this is taken out. In this case, the information processing unit 10 captures the thermal image signal of the infrared camera 9 into the personal computer 11, calculates the moving amount or moving speed of the wheel of the crane carriage 7 that is a moving object, and sends it to the signal combining unit 16. To synthesize these signals. The thermal image information processed by the personal computer 11 and the combined signal combined by the signal combining unit 16 are image-processed by the lock-in processor 15 and the image is displayed on the display unit (display) 12.

  Since there is a correlation between the amount of movement of the load and the stress fluctuation of the structure when the load passes, the thermal image data is synchronously added based on the reference signal as in the second and third embodiments, or the cross-correlation with the reference signal is performed. As a result, the stress fluctuation due to the moving load can be measured with higher accuracy than in the case without the reference signal.

  When the structure to be measured is a bridge, the distance between the measurement unit and the moving load source or a means to obtain information correlated with the distance between the vehicle passing through the bridge and the measurement unit It is conceivable to capture speed information at the same time as the thermal image. For example, a noise meter or a vibration meter is installed near the measurement unit, and information on sound and vibration when the vehicle passes close to the upper part of the measurement unit is obtained, or for example, a GPS or an ultrasonic distance meter is used. The position information on the vehicle side can be obtained, or the measurement object and the vehicle can be simultaneously photographed by a CCD camera or the like to know the position of the vehicle from the image.

  In addition, when a reference signal correlated with a thermal image is used as in the second or third embodiment shown in FIGS. 2 and 4, the crack defect portion to be measured is determined by the method shown in FIG. 5, for example. It can be performed. That is, from a spatial change and a temporal change of the thermal image of the measurement target shown in FIG. 5A, a spot where the temperature change locally changes sharply with the moving load is found, and this spot is cracked. A method by considering it as a tip can be used. In this case, the stress distribution at the arrow indicated by (a) in FIG. 5 is as shown in (b) in FIG. Further, the temporal change in the stress distribution at the arrow portion is as shown in FIG.

  Further, as shown in FIG. 6, it is also possible to use a method in which a portion where the temperature change locally shows a peak value with a moving load is found and this portion is regarded as a crack tip. That is, in the thermal image of the measurement target shown in FIG. 6A, the temporal change in the stress distribution of the portion from the change in the thermal image of the arrow portion is as shown in FIG. The portion P corresponds to the crack tip K in FIG.

  A crack in a structure is likely to occur in a portion where the occurrence location can be roughly predicted in advance, such as a welded portion between members. Therefore, if the portion with the largest amount of change or the portion that changes sharply is found from the time change data of the temperature distribution that changes with the moving load at the surrounding portion around the expected crack occurrence location, The site can be identified. In FIGS. 5 and 6, the stress value data includes local data of the image as a representative example, but in the analysis process, the temporal change of the stress distribution in the entire region of the thermal image is naturally evaluated.

  However, since it is also possible that the temperature changes regardless of the moving load due to the influence of the peripheral disturbance, as described above, a signal correlated with the moving load is measured at the same time and correlated with this reference signal, or It is preferable to perform synchronous addition processing with this reference signal. Thereby, it is possible to improve the crack detection accuracy.

  FIG. 7 shows a defect determination flow when such a reference signal is used. If there is a sensor, the movement amount of the load measured by the sensor is taken into the thermal image (C1). On the other hand, when the sensor is not used, the moving amount of the load is estimated from the rotation of the wheel of the moving load (C2). Then, the load movement amount grasped in this way is used as a reference signal (S1), and then the reference signal and the thermal image are synchronously added, or the cross correlation between the reference signal and the thermal image is obtained (S2). Next, a steep temperature (stress) change or a peak value of temperature (stress) is detected from a spatial change and a temporal change of the thermal image, and this is determined as a crack end (S3). In FIG. 7, a moving speed may be used instead of the moving amount.

  In order to detect defects in large structures by these methods, access to the vicinity of the object to be measured is conventionally performed by, for example, building a scaffold around the periphery, using an inspection robot, or using a work vehicle with a lifting device. By using an infrared camera (in some cases, using a telephoto lens) and a relatively simple information processing unit, etc., the defect detection work that has been carried out can be performed from a distance without accessing the vicinity of the measurement object. It can be implemented. For this reason, not only the cost required for the preparation for the inspection is greatly reduced, but also the inspection time can be greatly shortened. Therefore, when the structure is a cargo handling machine, the operation stop time for inspection can be shortened. Further, in the case of a bridge or the like, it is possible to detect a defect in a bridge pier or a bridge girder by capturing a temperature distribution variation accompanying a load variation caused by passing of a vehicle with a thermal image.

  The present invention is extremely effective in detecting defects such as cracks generated in large structures such as bridges and cargo handling machines.

The schematic diagram which shows the state which detects the defect of an overhead crane with the method which concerns on the 1st Embodiment of this invention. The schematic diagram which shows the state which detects the defect of an overhead crane by the method which concerns on the 2nd Embodiment of this invention. The figure which shows the relationship between the reference signal and thermal image information (temperature data) in Lock-in processor. The schematic diagram which shows the state which detects the defect of an overhead crane with the method which concerns on the 3rd Embodiment of this invention. The figure which shows an example of the method of determining the crack defect part of the measuring object in the case of using the reference signal correlated with a thermal image. The figure which shows the other example of the method of determining the crack defect part of the measuring object in the case of using the reference signal correlated with a thermal image. The flowchart which shows the defect determination flow at the time of using the reference signal correlated with a thermal image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Overhead crane 2; Defect 3; Thermal image measurement surface 4; Girder 5; Rail 7; Crane truck (moving load)
8; Baggage 9; Infrared camera 10; Information processing unit 11; Personal computer 12; Display unit 13; Laser displacement meter 14;
16: Signal synthesis unit

Claims (13)

  Stress fluctuation is caused by applying a moving load to the structure to be detected, and the temperature distribution fluctuation generated in the structure due to the thermoelastic effect or plastic heat generation due to this stress fluctuation is measured as a thermal image, and this temperature distribution fluctuation is measured. A defect detection method for a structure characterized by grasping stress fluctuation based on the above and detecting a defect of the measurement object.   Information that correlates with the moving amount or moving speed of the moving object, or the moving amount or moving speed that causes the moving load is acquired simultaneously with the thermal image, and the moving amount or moving speed of the moving object, or the correlation with the moving amount or moving speed is correlated. 2. The defect detection method for a structure according to claim 1, wherein a defect of the structure is detected using a thermal image that changes in synchronization with a certain signal as a reference signal.   The moving object image that causes the moving load is simultaneously captured in the thermal image, the moving amount or moving speed of the moving object is estimated from the thermal image, and this is used as a reference signal. 2. The structure defect detection method according to claim 1, wherein a defect of the structure is detected using a thermal image.   Incorporating the reference signal and the thermal image, and detecting a local peak value of a temperature change that is correlated with the reference signal in the thermal image, thereby detecting a structural defect in the thermal image. A method for detecting a defect in a structure according to claim 2 or claim 3.   Capturing the reference signal and the thermal image, and detecting a local and steep temperature change portion of the temperature change that is correlated with the reference signal and detects a structural defect in the thermal image. The defect detection method for a structure according to claim 2 or 3, wherein the defect is detected.   6. The structure defect detection method according to claim 1, wherein the moving load moves along the structure.   The structure defect detection method according to any one of claims 1 to 6, wherein the structure is a bridge or a cargo handling machine. An infrared camera for photographing the structure in a state where a moving load is applied to the structure to be detected by the moving object;
Information processing for calculating a stress fluctuation of a photographing part of the structure based on a thermoelastic effect or plastic heat generation from a temperature distribution fluctuation in a thermal image photographed by the infrared camera, and detecting a defect of the structure from the calculated stress fluctuation And a defect detecting device for a structure.   The information processing unit captures, together with the thermal image, a moving amount or moving speed of a moving object that causes a moving load, or information correlated with the moving amount or moving speed, and the moving amount or moving speed of the moving object, or the moving amount. 9. The defect of the structure according to claim 8, wherein the defect of the structure is detected by using a thermal image that varies in synchronization with information having a correlation with the moving speed as a reference signal. Detection device.   The defect detection of a structure according to claim 9, further comprising a sensor that detects a movement amount or movement speed of the moving object that generates the moving load, or information correlated with the movement amount or movement speed. apparatus.   The information processing unit simultaneously captures the moving object image causing the moving load into the thermal image, estimates the moving amount or moving speed of the moving object from the thermal image, and uses this as a reference signal. The structure defect detection device according to claim 9, wherein a defect of the structure is detected using a thermal image that varies in synchronization with the structure.   The information processing unit takes in the reference signal and the thermal image, finds a local peak value of a temperature change that is correlated with the reference signal in the thermal image, and thereby detects a structural defect in the thermal image. The structure defect detection apparatus according to claim 9, wherein the structure defect detection apparatus detects the structure defect.   The information processing unit captures the reference signal and the thermal image, finds a local and steep temperature change portion of the temperature change that is correlated with the reference signal in the thermal image, and thereby creates a structure in the thermal image. The defect detection device for a structure according to any one of claims 9 to 11, wherein a defect of the object is detected.

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