Structure Evaluation System and Structure Evaluation Method

Abstract

Embodiments of the present invention relate to a structure evaluation system and a structure evaluation method. The structure evaluation system according to the embodiment includes a plurality of sensors, a position calibration unit, and an evaluation unit. The plurality of sensors detect elastic waves. The position calibration unit calibrates the position of the elastic wave generation source using an elastic wave having an amplitude exceeding a threshold determined by the position of the generation source of the plurality of elastic waves and the arrangement positions of the plurality of sensors among the plurality of elastic waves respectively detected by the plurality of sensors. The evaluation unit evaluates the deterioration state of the structure based on the position calibration result of the elastic wave source by the position calibration unit.

Description

[0001] This application is a divisional application of a patent application for an invention titled "Structural Evaluation System and Structural Evaluation Method" with an application number of 201880014696.X, a filing date of February 27, 2018. Technical Field

[0002] Embodiments of the present invention relate to a structural evaluation system and a structural evaluation method. Background Art

[0003] By providing sensors such as AE sensors on the surface of a structure such as a bridge, elastic waves generated from damaged parts inside the structure can be detected. By further providing multiple sensors, the position of the elastic wave generation source (hereinafter referred to as "elastic wave source") can be calibrated based on the difference in the arrival times of the elastic waves between the sensors. In addition, by applying an impact to the structure from the outside, the same elastic waves are also generated, so the position of the elastic wave source can be calibrated. However, when there is damage in the transmission path of the elastic wave, the transmission of the elastic wave is hindered, so the elastic wave cannot be detected by the sensor. As a result, the correct position of the elastic wave source cannot be calibrated. Utilizing such characteristics, damage inside the structure can be detected based on the disorder of the distribution of the elastic wave sources at the calibrated positions. However, depending on the sensor configuration, even when a uniformly distributed impact is applied to the structure from the outside as an elastic wave source without damaging the structure, there may be a situation where the distribution of the elastic wave sources calibrated based on the signals obtained by the sensors is non-uniform. In such a case, there may be a situation where the deterioration state of the structure cannot be correctly evaluated.

[0004] Prior Art Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-125721 Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a structural evaluation system and a structural evaluation method that can improve the evaluation accuracy of the deterioration state of a structure.

[0007] The structural evaluation system according to the embodiment includes multiple sensors, a position calibration unit, and an evaluation unit. The multiple sensors detect elastic waves. The position calibration unit calibrates the position of the elastic wave generation source using the elastic waves having an amplitude exceeding a threshold determined by the position of the generation source of the multiple elastic waves and the arranged positions of the multiple sensors among the multiple elastic waves respectively detected by the multiple sensors. The evaluation unit evaluates the deterioration state of the structure based on the position calibration result of the elastic wave source by the position calibration unit. Brief Description of the Drawings

[0008] Figure 1This is a diagram showing the structure of the structure evaluation system in the first embodiment.

[0009] Figure 2 This is a diagram showing the positions where uniform impacts are randomly applied.

[0010] Figure 3 This is a diagram showing the results obtained by evaluating the position of the elastic wave source when a uniform impact is applied.

[0011] Figure 4 This is a diagram showing an enlarged view of the area surrounded by four sensors.

[0012] Figure 5A This is a diagram showing the relationship between the position of the elastic wave source and the position of the fourth sensor reached by the elastic wave.

[0013] Figure 5B This is a diagram showing the relationship between the position of the elastic wave source and the position of the fourth sensor reached by the elastic wave.

[0014] Figure 6 This is a diagram showing the distance between the position of the elastic wave source and the position of the fourth sensor reached by the elastic wave in proportion.

[0015] Figure 7 This is a timing diagram showing the processing flow of the structure evaluation system in the first embodiment.

[0016] Figure 8A This is a diagram showing the distance from the elastic wave source to the fourth sensor reached by the elastic wave using contour lines.

[0017] Figure 8B This is a diagram showing an example of the area division line.

[0018] Figure 9 This is a diagram for explaining the method of setting the threshold for each area.

[0019] Figure 10 This is a diagram showing the effect of using the method in this embodiment.

[0020] Figure 11A This is a diagram showing another example of the method of setting a new threshold.

[0021] Figure 11B This is a diagram showing another example of the method of setting a new threshold.

[0022] Figure 12 This is a diagram showing the structure of the structure evaluation system in the second embodiment.

[0023] Figure 13A This is a diagram showing an example of the elastic wave source distribution.

[0024] Figure 13B is a diagram showing an example of the elastic wave source density distribution.

[0025] Figure 14 is a timing chart showing the process flow of the structure evaluation system in the second embodiment.

[0026] Figure 15 is a diagram showing the structure of the structure evaluation system in the third embodiment.

[0027] Figure 16 is a timing chart showing the process flow of the structure evaluation system in the third embodiment. Detailed Embodiments

[0028] Hereinafter, with reference to the drawings, a structure evaluation system and a structure evaluation method according to an embodiment will be described.

[0029] (First Embodiment)

[0030] Figure 1 is a diagram showing the structure of the structure evaluation system 100 in the first embodiment.

[0031] The structure evaluation system 100 is used for evaluating the soundness of a structure. In the following description, evaluation means determining the degree of soundness of a structure, that is, the deterioration state of the structure, according to a certain criterion. Further, in the following description, as an example of a structure, a bridge is taken as an example, but the structure is not limited to a bridge. For example, as long as the structure is a structure that generates elastic waves due to the generation or development of cracks or external impacts (such as rain, artificial rain, etc.), any example can be used. In addition, a bridge is not limited to a structure erected over a river, valley, etc., and also includes various structures (such as viaducts on expressways) provided above the ground.

[0032] The structure evaluation system 100 includes an impact imparting unit 10, a plurality of sensors 20-1 to 20-n (n is an integer of 2 or more), a signal processing unit 30, and a structure evaluation device 40. The signal processing unit 30 and the structure evaluation device 40 are communicably connected by a wired or wireless method. Further, in the following description, when the sensors 20-1 to 20-n are not distinguished, they are referred to as sensors 20.

[0033] The impact imparting unit 10 generates elastic waves inside the structure 50 by imparting an impact 11 to the structure 50. The impact imparting unit 10 is a device provided on a vehicle or other transportation means that travels on the structure 50, for example. The impact imparting unit 10 imparts a lot of impacts 11 to the road surface of the structure 50 in a way that forms a uniform distribution. The impact 11 is imparted by, for example, the dispersion of water droplets, ice particles, solids, the knocking with a hammer such as a mallet, the heating with a laser, etc. When the impact imparting unit 10 imparts the impact 11 by dispersing water droplets, it is preferable that the size and timing of the water droplets hitting the road surface can be controlled by adjusting the nozzle and controlling the ejection timing. It is also preferable that during the knocking with a hammer such as a mallet, the intensity and timing of the impact 11 can be controlled to desired values.

[0034] The sensor 20 is provided on the structure 50. For example, the sensor 20 is provided on the surface opposite to the surface where the impact imparting unit 10 imparts the impact 11. The sensor 20 has a piezoelectric element, detects the elastic waves generated from inside the structure 50, and converts the detected elastic waves into an AE source signal as a voltage signal. The sensor 20 performs processing such as amplification and frequency limitation on the AE source signal and outputs it to the signal processing unit 30. In addition, an acceleration sensor can be used instead of the sensor 20. In this case, the acceleration sensor outputs the signal after signal processing to the signal processing unit 30 by performing the same processing as the sensor 20. The thickness of the structure 50 is, for example, 15 cm or more.

[0035] The signal processing unit 30 takes the AE source signal after the processing using the sensor 20 as an input. The signal processing unit 30 performs signal processing on the AE source signal in the input that has an amplitude value higher than a first threshold determined to be higher than the noise level. Specifically, first, when vibrations larger than the first threshold are detected, the signal processing unit 30 determines the signal for a predetermined time period starting from the moment when the first threshold is exceeded as an elastic wave waveform and saves the AE source signal having an amplitude value higher than the first threshold. Then, the signal processing unit 30 extracts AE feature quantities including information related to the elastic waves based on the data of the elastic wave waveforms represented by the saved AE source signals. In addition, the first threshold is set in advance.

[0036] The signal processing performed by the signal processing unit 30 is, for example, noise removal, parameter extraction, etc. In addition, the information related to the elastic waves refers to, for example, information such as the amplitude, energy, rising edge time, duration, frequency, number of zero crossings of the AE source signal, etc. The signal processing unit 30 outputs the information based on the extracted AE feature quantities as an AE signal to the structure evaluation device 40. The AE signal output by the signal processing unit 30 includes information such as the sensor ID, AE detection time, AE source signal amplitude, energy, rising edge time, and frequency.

[0037] Here, the amplitude of the AE source signal is, for example, the value of the maximum amplitude among elastic waves. The energy is, for example, the value obtained by time-integrating the values obtained by squaring the amplitude at each time point. In addition, the definition of energy is not limited to the above example, and a value approximated by, for example, the envelope of the waveform may also be used. The rise time is, for example, the time T1 from when the elastic wave rises from the zero value to exceed a preset predetermined value. The duration is, for example, the time from the rising edge of the elastic wave until the amplitude is less than a preset value. The frequency is the frequency of the elastic wave. The number of zero-crossing counts is, for example, the number of times the elastic wave crosses the reference line of the zero value.

[0038] The structure evaluation device 40 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, etc. connected by a bus, and executes an evaluation program. By executing the evaluation program, the structure evaluation device 40 functions as a device including a position calibration unit 401, an evaluation unit 402, and a display unit 403. In addition, all or part of each function of the structure evaluation device 40 may also be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). In addition, the evaluation program may be recorded on a computer-readable recording medium. A computer-readable recording medium refers to, for example, a removable medium such as a floppy disk, an optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built into a computer system. In addition, the evaluation program may also be transmitted and received via an electrical communication line.

[0039] The position calibration unit 401 takes the AE signal output from the signal processing unit 30 as an input. In addition, the position calibration unit 401 pre-holds information related to the installation position of the sensor 20 in the structure 50 (hereinafter referred to as "sensor position information") in correspondence with the sensor ID. The information related to the installation position is, for example, latitude and longitude, or the horizontal and vertical distances from a specific position of the structure 50.

[0040] The position calibration unit 401 performs position calibration of the elastic wave source based on the sensor ID included in the input AE signal, information such as the AE detection time, and the sensor position information previously stored. Specifically, the position calibration unit 401 evaluates the position of the elastic wave source based on the difference in the arrival times of the elastic waves at each sensor 20, that is, the AE detection time. In addition, the position calibration unit 401 uses the position calibration result to generate an elastic wave source distribution. The elastic wave source distribution represents the distribution of the positions of the elastic wave sources generated in the structure 50.

[0041] In addition, the position evaluation unit 401 divides the area within the elastic wave source distribution into a plurality of areas according to predetermined conditions. The position evaluation unit 401 newly sets different thresholds for each of the divided areas. In the following description, for simplicity of explanation, the case where the area within the elastic wave source distribution is divided into two areas is taken as an example for explanation. Then, the position evaluation unit 401 uses the AE signals having amplitude values higher than the newly set thresholds to perform position calibration of the elastic wave source again. Then, the position calibration unit 401 uses the position calibration result to generate an elastic wave source distribution. The position calibration unit 401 outputs the generated elastic wave source distribution to the evaluation unit 402.

[0042] The evaluation unit 402 takes the elastic wave source distribution output from the position calibration unit 401 as input. The evaluation unit 402 evaluates the deterioration state of the structure 50 based on the input elastic wave source distribution. Specifically, the evaluation unit 402 evaluates the deterioration state of the structure 50 based on the characteristic quantity of the elastic waves in the elastic wave source distribution. The characteristic quantity of the elastic waves in the elastic wave source distribution corresponds to the density of the elastic wave sources.

[0043] As a specific process, the evaluation unit 402 evaluates, based on the elastic wave source distribution, the areas where the density of the elastic wave sources is less than a predetermined determination threshold as the areas where deterioration of the structure 50 occurs. The density of the elastic wave sources can be obtained, for example, for each area surrounded by three sensors 20, or for each area surrounded by four sensors 20, or the elastic wave source distribution can be divided by a predetermined area, and the density can be obtained for each of the divided areas. The evaluation unit 402 displays the evaluation result on the display unit 403.

[0044] The display unit 403 is an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit 403 displays the evaluation result under the control of the evaluation unit 402. The display unit 403 can also be an interface for connecting the image display device to the structure evaluation device 40. In this case, the display unit 403 generates a video signal for displaying the evaluation result and outputs the video signal to the image display device connected to itself.

[0045] Next, as described above, the reason for setting a new threshold value will be described.

[0046] When the impact 11 is applied to the structure 50 in a uniform distribution, if the distribution of the position calibration results of the elastic wave sources is non-uniform, the region where the density is reduced can be judged as the damaged region. However, even when the impact 11 is applied to a sound structure without damage in a uniform distribution, it is possible that the distribution of the calibrated elastic wave sources becomes non-uniform.

[0047] Figure 2 is a diagram showing the positions where the uniform impact 11 is randomly applied. In Figure 2 the vertical axis and the horizontal axis represent the length (m) of the region to be measured. Figure 2 The indicated points 55 represent the positions where the impact 11 is applied.

[0048] In addition, Figure 3 is a diagram showing the result obtained by evaluating the positions of the elastic wave sources when the uniform impact 11 as shown in Figure 2 is applied. In Figure 3 the vertical axis and the horizontal axis represent the length (m) of the region to be measured. Figure 3 The positions of the triangles in Figure 3 represent the installation positions of the sensors 20. In Figure 3 the case where 15 sensors 20 are installed is shown. Figure 4 The position of the points 60 in Figure 3 represents the positions of the elastic wave sources.

[0049] In Figure 4 the density of the elastic wave sources near the sensor 20 is reduced. When comparing the density within the rectangular region 61 divided by the dashed line in Figure 3 and the density outside the rectangular region 61 including the installation position of the sensor 20, it can be seen that there is a difference in the density of the elastic wave sources. This is caused by the distance relationship between the positions of the elastic wave sources and the installation positions of the sensors 20. Generally, the position of the elastic wave source is calculated based on the time difference between the four sensors 20 that detect the elastic wave.

[0050] Figure 5A And Figure 5B are diagrams showing the relationship between the position of the elastic wave source and the distance to the position of the 4th arriving sensor 20 of the elastic wave. In the following description, the sensor 20 where the elastic wave arrives 4th is referred to as the 4th arriving sensor. As Figure 5AAs shown, when the position 60 of the elastic wave source is at the center of the four sensors 20, the distance between the position 60 of the elastic wave source and the position of the 4th arriving sensor is approximately the same as the distance that the elastic wave reaches the other sensors 20. Here, the other sensors 20 refer to the sensor 20 that the elastic wave reaches first, the sensor 20 that the elastic wave reaches second, and the sensor 20 that the elastic wave reaches third. In this case, elastic waves with approximately the same amplitude can be detected by all the sensors 20. As a result, if the amplitude value of the elastic wave detected by one sensor 20 exceeds the first threshold set in the signal processing unit 30, the possibility that the amplitude values of the elastic waves detected by all the sensors 20 exceed the first threshold becomes higher. In this case, the position of the elastic wave source can be evaluated.

[0051] In contrast, as Figure 5B shown, the closer the position 60 of the elastic wave source is to a certain one sensor 20 (the lower left sensor 20 in Figure 5B ), the farther the distance between the sensor 20 that is diagonal to a certain one sensor 20 (the upper right sensor 20 in Figure 5B ) and the position 60 of the elastic wave source becomes compared to the distance between the position 60 of the elastic wave source and the position of the 4th arriving sensor in Figure 5A . The farther the distance, the greater the attenuation of the elastic wave in the path. In this case, the amplitude of the elastic wave becomes smaller. As a result, the possibility of not exceeding the first threshold set in the signal processing unit 30 becomes higher.

[0052] When no elastic wave is detected by the 4th arriving sensor, it is difficult to determine the position of the elastic wave source, and the ratio of the elastic waves for which the position of the elastic wave source cannot be determined increases. Therefore, as Figure 3 and Figure 4 shown, for a uniformly distributed input, a difference in density is generated in the calibration result of the position of the elastic wave source. Thus, in a sound structure 50, when a density deviation occurs in the elastic wave source, there is a possibility that the structure evaluation device 40 misjudges the region with relatively low density as a region where deterioration has occurred.

[0053] Figure 6 is a graph showing the simulation results representing the distance between the position of the elastic wave source and the position of the 4th arriving sensor in the entire measurement object region shown in Figure 3 by a ratio. As Figure 5A shown, when the position of the elastic wave source is at the center of the four sensors 20, the distance between the position of the elastic wave source and the position of the 4th arriving sensor becomes the smallest. Therefore, in Figure 6In this case, the minimum distance from the elastic wave source to the 4th arrival at the sensor is expressed as "1". When taking area 12 as an example, the distance from the elastic wave source at the central point surrounded by four sensors 20 within area 12 to the 4th arrival at the sensor becomes the minimum distance 1.

[0054] In addition, the distance from the elastic wave source at a point near the sensor 20 to the 4th arrival at the sensor becomes the maximum. For example, the distance from the elastic wave source at a point near the sensor 20 to the 4th arrival at the sensor becomes approximately twice the distance from the elastic wave source at the central point surrounded by four sensors 20 to the 4th arrival at the sensor. Therefore, in Figure 6 the maximum distance from the elastic wave source to the 4th arrival at the sensor is expressed as "2". When taking area 12 as an example, the distance from the elastic wave source at a point near any one of the four sensors 20 within area 12 to the 4th arrival at the sensor becomes the maximum distance 2.

[0055] Therefore, as Figure 6 shown, it is shown that the closer the position of the elastic wave source is to one sensor 20, the farther the distance between the elastic wave source and the 4th arrival at the sensor. In addition, it is shown that the closer the position of the elastic wave source is to the center of the four sensors 20, the shorter the distance between the elastic wave source and the 4th arrival at the sensor.

[0056] Therefore, in the structure evaluation system 100 in the present embodiment, in the position evaluation unit 401, the measurement object area is divided into a plurality of areas, and different thresholds are newly set for each of the divided areas. Specifically, the position evaluation unit 401 divides the measurement object area into a plurality of areas according to the distance between the position of the elastic wave source and the position of the 4th arrival at the sensor. Then, by using the AE signal exceeding the newly set threshold again for position calibration by the position evaluation unit 401, the above-mentioned density deviation can be suppressed, and a more accurate diagnosis can be performed.

[0057] Figure 7 is a timing chart showing the processing flow of the structure evaluation system 100. In addition, in Figure 7 the processing, only the characteristic processing is described by using the signal processing unit 30 and the structure evaluation device 40.

[0058] The signal processing unit 30 acquires the AE source signal after the processing using the sensor 20 is performed (step S101). The signal processing unit 30 compares the amplitude value of the acquired AE source signal with the first threshold value. Then, the signal processing unit 30 stores the AE source signal having an amplitude value higher than the first threshold value (step S102). The signal processing unit 30 stores the AE source signal for a predetermined period of time. The signal processing unit 30 performs signal processing on the stored AE source signal (step S103). The signal processing unit 30 outputs the information based on the extracted AE feature amount as an AE signal to the structure evaluation device 40 (step S104).

[0059] The position calibration unit 401 performs position calibration of the elastic wave source based on the sensor ID, AE detection time, etc. information included in the input AE signal and the sensor position information held in advance (step S105). After that, the position calibration unit 401 generates an elastic wave source distribution using the position calibration result (step S106). In addition, the elastic wave source distribution obtained in the process of step S106 becomes a distribution having a deviation reflecting the arrangement of the sensors 20.

[0060] The position evaluation unit 401 generates a distance distribution representing the distribution of the distance from the elastic wave source to the 4th arriving sensor based on the generated elastic wave source distribution and the arrangement position of the sensor 20 (step S107). For example, the position evaluation unit 401 Figure 8A generates the contour map shown as the distance distribution. Figure 8A is a diagram showing the distance from the elastic wave source to the 4th arriving sensor at each position in the plane where 9 sensors 20 are arranged, using a contour map. In addition, as the contour map, it is also possible to perform a theoretical calibration simulation as shown in Figure 3 and calculate and utilize the density of the calibration points.

[0061] Next, the position evaluation unit 401 uses the generated distance distribution to draw a contour line 21 at an arbitrary distance (the distance from the elastic wave source to the 4th arriving sensor) as shown in Figure 8B and sets the contour line 21 as the region dividing line (step S108). Figure 8B is a diagram showing an example of the region dividing line. The distance serving as the reference for the position evaluation unit 401 to draw the contour line 21 is set in advance. In addition, in Figure 8A and Figure 8B the case where 9 sensors 20 are arranged is illustrated using a diagram, but in the case where 15 sensors 20 are arranged in the measurement object region as shown in Figure 3 the position calibration unit 401 generates a corresponding contour map.

[0062] Thereafter, the position evaluation unit 401 sets a threshold value for each region divided by the region division line (step S109). Here, the position evaluation unit 401 sets a threshold value for the region inside the region division line and a threshold value for the region outside the region division line, respectively. The region inside the region division line refers to the region inside the contour line 21. The region outside the region division line refers to the region outside the contour line 21. In addition, the position evaluation unit 401 may directly use the contour line 21 as the region division line, or use an appropriate shape such as a quadrilateral or an ellipse according to the contour line 21 and the arrangement position of the sensor 20, as Figure 3 shown, for example, in the shape of a quadrilateral, an ellipse, etc.

[0063] The method for setting the threshold value for each region divided by the region division line will be described.

[0064] Figure 9 FIG. is a diagram for explaining the method for setting the threshold value for each region. It is assumed that the number of measured elastic waves has a normal distribution with respect to the amplitude. In Figure 9 , the vertical axis represents the amplitude of the elastic wave, and the horizontal axis represents the distance from the elastic wave source to the 4th arrival sensor. D in the horizontal axis represents the position of the region division line obtained from the contour map such as Figure 8A shown. Figure 9 The line segment 62 shown represents the upper limit of the amplitude of the elastic wave with respect to the distance from the elastic wave source to the 4th arrival sensor. Figure 9 The line segment 63 shown represents the lower limit of the amplitude of the elastic wave with respect to the distance from the elastic wave source to the 4th arrival sensor. The longer the transmission distance of the elastic wave, the more the amplitude of the elastic wave decays. Therefore, the detected amplitude is represented by a line that descends to the right.

[0065] For example, through prior experiments on the measurement object, similar structures, sound test specimens, etc., the above attenuation characteristics, amplitude distribution of elastic waves, etc. can be measured and determined. In addition, based on materials, structures, etc., estimated values can be calculated in advance and the calculated estimated values can be used. When measuring elastic waves, a first threshold value is set in the signal processing unit 30. Therefore, elastic waves with an amplitude lower than the first threshold value are not used for calibrating the position of the elastic wave source. As a result, the farther the distance from the elastic wave source to the 4th arrival sensor, the fewer elastic waves with an amplitude above the first threshold value are detected. As a result, the density of the calibrated elastic wave source decreases. Therefore, the position calibration unit 401 divides the region based on the position at distance D.

[0066] The position evaluation unit 401 sets each threshold value in such a way that it has different threshold values for each area. For example, it sets the threshold value for the area closer than D to the second threshold value, and the threshold value for the area farther than D to the third threshold value. The area closer than D is the area within the area dividing line. The far area is the area outside the area dividing line. For example, the position evaluation unit 401 adjusts the second threshold value and the third threshold value so that the number of elastic waves with a distance shorter than D and an amplitude higher than the second threshold value, and the number of elastic waves with a distance longer than D and an amplitude higher than the third threshold value are approximately equal. Thereby, the calibration density of the elastic wave sources in the near-distance area and the far-distance area can be adjusted to be equal. In Figure 9 In the example of, the position calibration unit 401 sets the second threshold value and the third threshold value to be higher than the first threshold value and the second threshold value to be higher than the third threshold value.

[0067] The position evaluation unit 401 selects AE signals exceeding the newly set second threshold value and third threshold value from the stored AE signals (step S110). Specifically, the position evaluation unit 401 selects AE signals exceeding the second threshold value from the stored AE signals used for position calibration of the elastic wave sources in the area closer than D. The position evaluation unit 401 selects AE signals exceeding the third threshold value from the stored AE signals used for position calibration of the elastic wave sources in the area farther than D.

[0068] Then, the position evaluation unit 401 uses the selected AE signals to perform position calibration of the elastic wave sources again. After that, the position evaluation unit 401 generates an elastic wave source distribution using the position calibration result (step S111). The position evaluation unit 401 outputs the generated elastic wave source distribution to the evaluation unit 402. The obtained distribution of the elastic wave sources becomes a distribution in which the deviation caused by the configuration of the sensor 20 is corrected. In this distribution, the evaluation unit 402 diagnoses the area where the density of the elastic wave sources is reduced as damaged, and the evaluation of the structure can be performed more correctly.

[0069] The evaluation unit 402 evaluates the deterioration state of the structure 50 based on the elastic wave source distribution output from the position evaluation unit 401 (step S112). Specifically, the evaluation unit 402 determines whether the density of the obtained elastic wave sources is uniform based on the elastic wave source distribution. When the density of the obtained elastic wave sources is uniform, the evaluation unit 402 determines that it is in a sound state.

[0070] On the other hand, when the density of the obtained elastic wave sources is not uniform, the evaluation unit 402 determines that deterioration has occurred. In this case, the evaluation unit 402 evaluates the area where the density of the elastic wave sources is less than the predetermined determination threshold value as the area where the deterioration of the structure 50 has occurred. The display unit 403 displays the evaluation result according to the control of the evaluation unit 402 (step S113).

[0071] Figure 10 This is a diagram showing the effects of using the method described above. In Figure 10 , to simplify the comparison with Figure 3 , the dashed line 61 shown in Figure 3 is used to represent the area dividing line. In addition, the threshold value inside the area dividing line is set to be higher than the threshold value outside the area dividing line. As shown in Figure 10 , the difference in density for each area in Figure 3 is relatively large. In contrast, in Figure 10 , the difference in density can be reduced in two areas compared to Figure 3 .

[0072] According to the structure evaluation system 100 configured as described above, the evaluation accuracy of the deterioration state of the structure can be improved. Specifically, first, the structure evaluation system 100 divides the measurement target area into multiple areas based on the position of the elastic wave source and the distance to the 4th arrival sensor. Next, the structure evaluation system 100 sets different threshold values for each divided area. At this time, the structure evaluation system 100 sets the threshold value of the area with a shorter distance between the elastic wave source position and the 4th arrival sensor higher than the threshold value of the area with a longer distance between the elastic wave source position and the 4th arrival sensor. As a result, it is difficult to detect the elastic waves in the area with a shorter distance from the elastic wave source to the 4th arrival sensor. Moreover, the structure evaluation system 100 uses the elastic waves with an amplitude exceeding the set threshold value to calibrate the position of the elastic wave source. Thus, when the structure does not have damage, even if an impact 11 evenly distributed is applied to the structure 50, as a result of the position calibration, the density of the elastic wave source becomes uniform. Consequently, a sound structure will not be misjudged as deteriorated. Therefore, the evaluation accuracy of the deterioration state of the structure can be improved.

[0073] Hereinafter, a modification example of the structure evaluation system 100 in the first embodiment will be described.

[0074] In this embodiment, a structure is shown in which the position calibration unit 401 sets the newly set threshold values (for example, the second threshold value and the third threshold value) higher than the first threshold value. However, the newly set threshold values are not limited to this. For example, the position calibration unit 401 may also set the threshold value inside the area dividing line higher than the first threshold value and set the threshold value outside the area dividing line to be the same as the first threshold value. Figure 11A This is a diagram showing another example of the setting method of the new threshold value. As shown in Figure 11A , the position evaluation unit 401 sets the second threshold value of the area closer than D higher than the first threshold value and sets the third threshold value of the area farther than D to be the same as the first threshold value.

[0075] In addition, for example, the position calibration unit 401 may also set the threshold value within the region division line to be higher than the first threshold value, and set the threshold value outside the region division line to be smaller than the first threshold value. Figure 11B It is a diagram showing another example of the new threshold setting method. As Figure 11B shown, the position evaluation unit 401 sets the second threshold value for the region closer than D to be higher than the first threshold value, and sets the third threshold value for the region farther than D to be smaller than the first threshold value. As Figure 11B shown, when setting the threshold value outside the region division line to be smaller than the first threshold value, the position calibration unit 401 needs to obtain from the signal processing unit 30 the AE signal that does not exceed the first threshold value.

[0076] The number of regions divided by the position calibration unit 401 does not need to be 2, and multiple regions can also be set stepwise. For example, the position calibration unit 401 can set the region division line for each distance obtained in the distance distribution and divide the regions stepwise, or can set the region division line for each specific distance among the distances obtained in the distance distribution and divide the regions stepwise. In addition, the position calibration unit 401 can also make the region division finer and set continuous threshold values corresponding to the distance. Furthermore, it is preferable that the position calibration unit 401 sets the newly set threshold value to be higher than the first threshold value for the region where the distance from the elastic wave source to the 4th arrival sensor is shorter.

[0077] The structure evaluation device 40 can also be configured to switch modes when the characteristics of the impact are different, such as when an artificial impact (for example, an impact applied by hand, an impact applied by the impact application unit 10) is input and during natural rainfall. In this case, the position calibration unit 401 stores the setting criteria for the region division line and the setting method for the new threshold value for each mode. Then, the position calibration unit 401 performs processing according to the mode switch.

[0078] (Second Embodiment)

[0079] In the second embodiment, the structure evaluation system does not set a new threshold value, generates the density distribution of the elastic wave source, corrects the density distribution of the elastic wave source, and thereby evaluates the deterioration state of the structure.

[0080] Figure 12 It is a diagram showing the structure of the structure evaluation system 100a in the second embodiment.

[0081] The structure evaluation system 100a includes an impact application unit 10, a plurality of sensors 20-1 to 20-n, a signal processing unit 30, and a structure evaluation device 40a. The structure evaluation system 100a is different in structure from the structure evaluation system 100 in that it includes the structure evaluation device 40a instead of the structure evaluation device 40. Hereinafter, only the structure evaluation device 40a will be described.

[0082] The structure evaluation device 40a includes a CPU, a memory, an auxiliary storage device, etc. connected by a bus, and executes an evaluation program. By executing the evaluation program, the structure evaluation device 40a functions as a device including a position calibration unit 401a, an evaluation unit 402a, a display unit 403, a density distribution generation unit 404, and a calibration unit 405. In addition, all or part of each function of the structure evaluation device 40a can also be implemented using hardware such as an ASIC, a PLD, or an FPGA. Additionally, the evaluation program can also be recorded on a computer-readable recording medium. A computer-readable recording medium refers to, for example, removable media such as a floppy disk, an optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built into a computer system. Additionally, the evaluation program can also be transmitted and received via an electrical communication line.

[0083] The structure evaluation device 40a is different in structure from the structure evaluation device 40 in that it includes a position calibration unit 401a and an evaluation unit 402a instead of the position calibration unit 401 and the evaluation unit 402, and newly includes a density distribution generation unit 404 and a calibration unit 405. Regarding other structures, the structure evaluation device 40a is the same as the structure evaluation device 40. Therefore, only the position calibration unit 401a, the evaluation unit 402a, the density distribution generation unit 404, and the calibration unit 405 will be described.

[0084] The position calibration unit 401a performs position calibration of the elastic wave source based on information such as the sensor ID and AE detection time included in the input AE signal, and the sensor position information previously held. The method of position calibration of the elastic wave source is the same as that of the first embodiment, so the description is omitted. Additionally, the position calibration unit 401a uses the position calibration result to generate an elastic wave source distribution. The position calibration unit 401a outputs the generated elastic wave source distribution to the density distribution generation unit 404.

[0085] The density distribution generation unit 404 generates an elastic wave source density distribution using the generated elastic wave source distribution. The elastic wave source density distribution is a distribution representing the density of the elastic wave source. The density distribution generation unit 404 outputs the generated elastic wave source density distribution to the calibration unit 405.

[0086] Figure 13A is a diagram showing an example of the elastic wave source distribution, Figure 13B is a diagram showing an example of the elastic wave source density distribution obtained from the elastic wave source distribution shown in Figure 13A In Figure 13A the vertical axis and the horizontal axis represent the length (m) of the area to be measured. In Figure 13A it can be seen that the elastic wave sources are concentrated near the center, and the farther away from the center, the fewer the elastic wave sources. By generating an elastic wave source density distribution as shown in Figure 13BThe elastic wave source density distribution enables easy determination of where the density of the elastic wave sources is high.

[0087] The correction unit 405 corrects the generated elastic wave source density distribution by multiplying it by the correction coefficient 1 / F(x, y). The correction unit 405 outputs the corrected elastic wave source density distribution to the evaluation unit 402a. Further, in the sound structure 50, the correction coefficient is determined in such a way that the corrected elastic wave source density distribution becomes uniform. More specifically, the correction coefficient is determined by the following method, for example. The correction coefficient is a coefficient for correcting the deviation of the elastic wave source density corresponding to the arrangement position of the sensor 20. Therefore, for each position of the elastic wave source, the reciprocal of the probability F(x, y) of the correctly calibrated position is multiplied. The reference position (0, 0) of (x, y) is, for example, the upper left of the elastic wave source density distribution.

[0088] The farther the distance from the elastic wave source to the 4th arrival sensor, the lower F(x, y) becomes. For example, the correspondence between F(x, y) and the distance from the elastic wave source to the 4th arrival sensor is pre-calculated through numerical simulations based on the contour map shown in FIG. 8 and the attenuation characteristics of elastic waves, experiments in the sound structure 50, etc.

[0089] The evaluation unit 402a evaluates the deterioration state of the structure based on the elastic wave source density distribution corrected by the correction unit 405. The evaluation unit 402a displays the evaluation result on the display unit 403.

[0090] Figure 14 is a timing chart showing the processing flow of the structure evaluation system 100a. Further, in Figure 14 the processing, the signal processing unit 30 and the structure evaluation device 40a are used, and only the characteristic processing is described. Additionally, in Figure 14 regarding the same processing as Figure 7 the same symbols as Figure 7 are added and the description is omitted.

[0091] The position calibration unit 401a outputs the elastic wave source distribution generated in the processing of step S106 to the density distribution generation unit 404. The density distribution generation unit 404 generates an elastic wave source density distribution using the elastic wave source distribution output from the position calibration unit 401a (step S201). The density distribution generation unit 404 outputs the generated elastic wave source density distribution to the correction unit 405. The correction unit 405 corrects the elastic wave source density distribution by multiplying the generated elastic wave source density distribution by the correction coefficient 1 / F(x, y) (step S202).

[0092] The correction unit 405 outputs the corrected elastic wave source density distribution to the evaluation unit 402a. The evaluation unit 402a evaluates the deterioration state of the structure based on the elastic wave source density distribution corrected by the correction unit 405 (step S203). Specifically, the evaluation unit 402a determines whether the density of the elastic wave source density distribution is uniform based on the corrected elastic wave source density distribution. When the density represented by the elastic wave source density distribution is uniform, the evaluation unit 402a determines that the state is sound.

[0093] On the other hand, when the density represented by the elastic wave source density distribution is non-uniform, the evaluation unit 402a determines that deterioration has occurred. In this case, the evaluation unit 402a evaluates the region where the density represented by the elastic wave source density distribution is less than a predetermined determination threshold as the region where deterioration of the structure 50 has occurred.

[0094] The structure evaluation system 100a configured as described above evaluates the deterioration state of the structure 50 by correcting the elastic wave source density distribution obtained from the elastic wave source distribution with a correction coefficient corresponding to the arrangement of the sensors 20. By correcting the elastic wave source density distribution using the correction coefficient, when the structure has no damage, the density represented by the elastic wave source density distribution becomes substantially uniform. As a result, a sound structure will not be erroneously evaluated as deteriorated. Therefore, the evaluation accuracy of the deterioration state of the structure can be improved.

[0095] (Third Embodiment)

[0096] In the third embodiment, the structure evaluation system does not set a new threshold, but corrects the elastic wave source density distribution obtained from a sound structure 50 that is a comparison object with the measurement results, thereby evaluating the deterioration state of the structure.

[0097] Figure 15 It is a diagram showing the structure of the structure evaluation system 100b in the third embodiment.

[0098] The structure evaluation system 100b includes an impact imparting unit 10, a plurality of sensors 20-1 to 20-n, a signal processing unit 30, and a structure evaluation device 40b. The structure evaluation system 100b is different in structure from the structure evaluation system 100a in that it includes a structure evaluation device 40b instead of the structure evaluation device 40a. Hereinafter, only the structure evaluation device 40b will be described.

[0099] The structure evaluation device 40b includes a CPU, a memory, an auxiliary storage device, etc. connected by a bus, and executes an evaluation program. By executing the evaluation program, the structure evaluation device 40a functions as a device including a position calibration unit 401a, an evaluation unit 402b, a display unit 403, a density distribution generation unit 404b, and a calibration unit 405b. In addition, all or part of each function of the structure evaluation device 40b can also be implemented using hardware such as an ASIC, a PLD, or an FPGA. Additionally, the evaluation program can also be recorded on a computer-readable recording medium. A computer-readable recording medium refers to, for example, removable media such as a floppy disk, an optical disk, a ROM, a CD-ROM, etc., and storage devices such as a hard disk built into a computer system. Additionally, the evaluation program can also be transmitted and received via an electrical communication line.

[0100] The structure evaluation device 40b is different in structure from the structure evaluation device 40a in that it includes an evaluation unit 402b, a density distribution generation unit 404b, and a calibration unit 405b instead of the evaluation unit 402a, the density distribution generation unit 404a, and the calibration unit 405a. Regarding other structures, the structure evaluation device 40b is the same as the structure evaluation device 40a. Therefore, only the evaluation unit 402b, the density distribution generation unit 404b, and the calibration unit 405b will be described.

[0101] The density distribution generation unit 404b generates an elastic wave source density distribution using the generated elastic wave source distribution. The density distribution generation unit 404b outputs the generated elastic wave source density distribution to the evaluation unit 402b.

[0102] The calibration unit 405b calibrates the elastic wave source density distribution to be a comparison object. Here, the elastic wave source density distribution to be a comparison object is the elastic wave source density distribution obtained in the sound structure 50. That is, the elastic wave source density distribution to be a comparison object is an elastic wave source density distribution having a uniform distribution. The calibration unit 405b can either pre-store the elastic wave source density distribution to be a comparison object or obtain the elastic wave source density distribution to be a comparison object from a storage device storing the elastic wave source density distribution to be a comparison object.

[0103] Additionally, the calibration unit 405b calculates a calibration magnification for each position of the elastic wave source based on a theoretically calculated density deviation or an experimentally verified density deviation calculated in advance. This calibration magnification becomes, for example, a distribution such as F(x, y). The calibration unit 405b calibrates the elastic wave source density distribution to be a comparison object by multiplying the calculated calibration magnification to the elastic wave source density distribution to be a comparison object. Hereinafter, the calibrated elastic wave source density distribution to be a comparison object will be referred to as a calibrated reference density distribution. The calibration unit 405b outputs the calibrated reference density distribution to the evaluation unit 402b.

[0104] The evaluation unit 402b evaluates the deterioration state of the structure based on the elastic wave source density distribution output from the density distribution generation unit 404b and the corrected reference density distribution output from the correction unit 405b. The evaluation unit 402b displays the evaluation result on the display unit 403.

[0105] Figure 16 It is a timing chart showing the processing flow of the structure evaluation system 100b. In addition, in Figure 16 the processing, only the characteristic processing is described using the signal processing unit 30 and the structure evaluation device 40b. In addition, in Figure 16 regarding the same processing as Figure 14 the same, the same symbols as Figure 14 are added to omit the description.

[0106] The density distribution generation unit 404b generates an elastic wave source density distribution using the elastic wave source distribution output from the position calibration unit 401a (step S301). The density distribution generation unit 404b outputs the generated elastic wave source density distribution to the evaluation unit 402b. The correction unit 405b corrects the elastic wave source density distribution to be compared by multiplying it by a correction magnification calculated for each position of the elastic wave source, thereby generating a corrected reference density distribution (step S302). The density distribution generation unit 404 outputs the generated corrected reference density distribution to the evaluation unit 402b.

[0107] The evaluation unit 402b evaluates the deterioration state of the structure based on the elastic wave source density distribution output from the density distribution generation unit 404b and the corrected reference density distribution output from the correction unit 405b (step S303). Specifically, the evaluation unit 402b compares the corrected reference density distribution and the elastic wave source density distribution, and when the corrected reference density distribution and the elastic wave source density distribution are substantially the same, it is determined that the state is sound. Here, a substantially the same criterion is set in advance.

[0108] On the other hand, the evaluation unit 402b compares the corrected reference density distribution and the elastic wave source density distribution, and evaluates the area where the density is lower than the corrected reference density distribution as the area where the deterioration of the structure 50 occurs.

[0109] The structure evaluation system 100b configured as described above corrects the elastic wave source distribution serving as a reference, compares the elastic wave source density distribution and the corrected elastic wave source density distribution, and thereby evaluates the deterioration state of the structure 50. In the second embodiment, the elastic wave source density distribution in the sound state to be compared is uniform, but in this embodiment, the elastic wave source density distribution to be compared is corrected. As a result, the elastic wave source density distribution obtained from the sound structure 50 to be compared becomes the elastic wave source density distribution corresponding to the arrangement position of the sensor 20 at the time of measurement. Further, the structure evaluation device 40b compares the corrected elastic wave source density distribution and the elastic wave source density distribution obtained by actual measurement, and can evaluate that the structure is in a sound state when the elastic wave source density distribution is substantially the same as the corrected elastic wave source density distribution. Therefore, when the elastic wave source density distribution is substantially the same as the corrected elastic wave source density distribution, even if there is a region in the elastic wave source density distribution obtained by actual measurement where the density is less than a predetermined determination threshold, a sound structure is not erroneously evaluated as deteriorated. Therefore, the evaluation accuracy of the deterioration state of the structure can be improved.

[0110] Hereinafter, a modification example common to each embodiment will be described.

[0111] In the structure evaluation systems 100, 100a, and 100b, it is sufficient to include three or more sensors 20.

[0112] The structure evaluation systems 100, 100a, and 100b may not include the impact imparting unit 10. In such a configuration, the impact 11 on the structure 50 may be provided manually.

[0113] Each functional unit included in the structure evaluation device 40 may be partially or entirely provided in another housing. For example, the structure evaluation device 40 may only include the evaluation unit 402, and the position calibration unit 401 and the display unit 403 may be provided in another housing. In such a configuration, the evaluation unit 402 acquires the elastic wave source distribution from another housing, and uses the acquired elastic wave source distribution to evaluate the soundness of the structure. Then, the evaluation unit 402 outputs the evaluation result to the display unit 403 included in another housing.

[0114] By configuring in this way, by using an existing device in the derivation of the elastic wave source distribution, the manufacturing cost of the structure evaluation device 40 can be suppressed.

[0115] Alternatively, the first threshold may not be set in the signal processing unit 30, and the signal processing unit 30 continuously stores all the signals during the measurement period. In such a configuration, it may be configured that, for the signal processing unit 30, the first threshold is set after the measurement is completed. Thereby, the signal processing unit 30 outputs elastic waves with amplitudes exceeding the newly set first threshold to the structure evaluation device 40 (or the structure evaluation device 40a, the structure evaluation device 40b). As a result, by storing all the signals, the first threshold for identifying each elastic wave can be freely set after the measurement is completed. In addition, since signals with low levels are also all stored, by reducing the threshold again later to re-identify the elastic waves, the elastic wave waveforms that did not reach the first threshold once can also be obtained later.

[0116] Alternatively, the first threshold may not be set in the signal processing unit 30, and the signal processing unit 30 outputs all the AE signals during the measurement period to the structure evaluation device 40 (or the structure evaluation device 40a, the structure evaluation device 40b). In such a configuration, the position calibration unit 401 (or the position calibration unit 401a, the position calibration unit 401b) uses the obtained AE signals to perform the processing in each embodiment.

[0117] The signal processing unit 30 may also be provided in the structure evaluation device 40 (or the structure evaluation device 40a, the structure evaluation device 40b). In such a configuration, the signal processing unit 30 directly or via a relay device (not shown) from the sensor 20 obtains the AE source signal after performing the processing using the sensor 20.

[0118] In Figure 1 one signal processing unit 30 is connected to a plurality of sensors 20-1 to 10-n, but the structure evaluation system 100 (or the structure evaluation system 100a, the structure evaluation system 100b) may also be configured to include a plurality of signal processing units 30, and a signal processing unit 30 is connected to each sensor 20 to include a plurality of sensor components.

[0119] Alternatively, the evaluation unit 402 (or the evaluation unit 402a, the evaluation unit 402b) may act as an output control unit. The output control unit controls the output unit to output the evaluation result. Here, in the output unit, it includes a display unit 403, a communication unit, and a printing unit. When the output unit is the communication unit, the output control unit controls the communication unit to send the evaluation result to other devices. In addition, when the output unit is the printing unit, the output control unit controls the printing unit to print the evaluation result. Furthermore, the structure evaluation device 40 (or the structure evaluation device 40a, the structure evaluation device 40b) may also serve as the output unit, including a part or all of the display unit 403, the communication unit, and the printing unit to perform the above actions.

[0120] According to at least one embodiment described above, the structure evaluation system 100 includes a plurality of sensors 20-1 to 20-N, a position calibration unit 401, and an evaluation unit 402. The plurality of sensors 20-1 to 20-N detect elastic waves. The position calibration unit 401 calibrates the position of the elastic wave source using an elastic wave having an amplitude exceeding a threshold determined by the positions of the plurality of elastic wave sources among the plurality of elastic waves respectively detected by the plurality of sensors 20-1 to 20-N. The evaluation unit 402 evaluates the deterioration state of the structure based on the position calibration result of the elastic wave source by the position calibration unit 401. Thereby, the evaluation accuracy of the deterioration state of the structure can be improved.

[0121] Although several embodiments of the present invention have been described, these embodiments are merely illustrative and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and similarly included in the invention described in the claims and its equivalent scope.

Claims

1. A structure evaluation system, comprising: A plurality of sensors that detect elastic waves; A position calibration unit that calibrates the position of the source of the elastic waves based on a plurality of elastic waves respectively detected by the plurality of sensors; A density distribution generation unit that generates an elastic wave source density distribution representing the density distribution of the sources of the elastic waves based on the position calibration result of the sources of the elastic waves by the position calibration unit; A correction unit that corrects the elastic wave source density distribution using a correction coefficient for correcting the elastic wave source density distribution according to the arrangement positions of the plurality of sensors; and An evaluation unit that evaluates the deterioration state of the structure based on the elastic wave source density distribution corrected by the correction unit.

2. A structure evaluation system, comprising: A plurality of sensors that detect elastic waves; A position calibration unit that calibrates the position of the source of the elastic waves based on a plurality of elastic waves respectively detected by the plurality of sensors; A density distribution generation unit that generates an elastic wave source density distribution representing the density distribution of the sources of the elastic waves based on the position calibration result of the sources of the elastic waves by the position calibration unit; A correction unit that corrects the elastic wave source density distribution to be compared using a correction magnification obtained in advance from a sound structure for correcting the elastic wave source density distribution to be compared according to the arrangement positions of the plurality of sensors; and An evaluation unit that evaluates the deterioration state of the structure based on the elastic wave source density distribution generated by the density distribution generation unit and the elastic wave source density distribution to be compared corrected by the correction unit.

3. A structure evaluation method, comprising: A position calibration step of calibrating the position of the source of the elastic waves based on a plurality of elastic waves respectively detected by a plurality of sensors that detect elastic waves; A density distribution generation step of generating an elastic wave source density distribution representing the density distribution of the sources of the elastic waves based on the position calibration result of the sources of the elastic waves calibrated in the position calibration step; A correction step of correcting the elastic wave source density distribution using a correction coefficient for correcting the elastic wave source density distribution according to the arrangement positions of the plurality of sensors; and An evaluation step of evaluating the deterioration state of the structure based on the elastic wave source density distribution corrected in the correction step.

4. A structure evaluation method, comprising: A position calibration step of calibrating the position of the source of the elastic waves based on a plurality of elastic waves respectively detected by a plurality of sensors that detect elastic waves; A density distribution generation step of generating an elastic wave source density distribution representing the density distribution of the sources of the elastic waves based on the position calibration result of the sources of the elastic waves calibrated in the position calibration step; A correction step of correcting the elastic wave source density distribution to be compared using a correction magnification obtained in advance from a sound structure for correcting the elastic wave source density distribution to be compared according to the arrangement positions of the plurality of sensors; and Evaluation step: evaluate the deterioration state of the structure based on the elastic wave source density distribution generated by the density distribution generation step and the elastic wave source density distribution to be compared that has been corrected by the correction step.

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