Corrosive environment detection sensor and system

Abstract

To provide a corrosive environment detection sensor and a corrosive environment detection system which are small in size and can be easily used.SOLUTION: A corrosion environment detection sensor according to an embodiment of the present disclosure includes: an elastic body including a metal material which is altered by corrosive factors in the atmosphere; a vibration sensor attached to the elastic body; a signal processing unit for processing a signal from the vibration sensor; and a housing including a signal processing unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a sensor and system for detecting corrosive environments. [Background technology]

[0002] Conventionally, in order to monitor salt damage environments for structures such as reinforced concrete, data is collected and verified using methods such as the Public Works Institute Tank Method and the Dry Gauze Method, which observe the amount of airborne salt (see Patent Document 1). Salt damage refers to a phenomenon in which, for example, chloride ions contained in antifreeze agents used in marine environments and cold regions penetrate from the concrete surface, the presence of chloride ions accelerates corrosion of reinforcing bars in the concrete, and the volume expansion of the corrosion products causes cracks and peeling in the concrete or a reduction in the cross-sectional area of ​​the reinforcing bars, thereby reducing the performance of the structure and making it unable to perform its intended function. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-058193 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is known that the deterioration characteristics of structures vary even at adjacent locations within the same material, so a small, easy-to-use sensor that can be attached to structures is extremely useful for monitoring salt damage environments.

[0005] The present disclosure has been made in consideration of such problems, and has an object to provide a small, easy-to-use corrosive environment detection sensor and system. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, a corrosive environment detection sensor is characterized by comprising an elastic body including a metallic material that is altered by a corrosive factor in the atmosphere, a vibration sensor attached to the elastic body, a signal processing unit that processes a signal from the vibration sensor, and a housing that includes the signal processing unit.

[0007] According to one aspect of the present disclosure, the metal material is the same as the material contained in the structure to be monitored.

[0008] According to one aspect of the present disclosure, the metal material is a material that is altered by corrosion factors in the atmosphere more quickly than materials contained in the structure to be monitored.

[0009] According to another aspect of the present disclosure, the vibration sensor is an acceleration sensor.

[0010] According to another aspect of the present disclosure, the vibration sensor is a vibration power generating element.

[0011] According to another aspect of the present disclosure, the above-mentioned corrosive environment detection sensor further includes a wireless device that wirelessly transmits a processing result by the signal processing unit.

[0012] According to another aspect of the present disclosure, the corrosive environment detection sensor further includes a display unit.

[0013] According to another aspect of the present disclosure, a corrosive environment detection system includes the above-described corrosive environment detection sensor and a monitoring terminal including a display unit, the monitoring terminal being communicatively connected to a plurality of the corrosive environment detection sensors.

[0014] According to another aspect of the present disclosure, the corrosive environment detection system further includes a concentrator communicatively connected to a plurality of the corrosive environment detection sensors, and the monitoring terminal is communicatively connected to the concentrator.

[0015] According to another aspect of the present disclosure, the concentrator includes a determination means for determining whether or not a value of the processing result from the signal processing unit is equal to or greater than a predetermined threshold value.

[0016] According to another aspect of the present disclosure, the concentrator further includes a display unit. Effect of the Invention

[0017] According to the present disclosure, it is possible to provide a small-sized and easy-to-use corrosive environment detection sensor and system. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of a corrosive environment detection sensor according to an embodiment; [Diagram 2] FIG. 1 is a schematic configuration diagram of a vibration power generating element according to an embodiment. [Diagram 3] FIG. 2 is a cross-sectional view of an elastic body according to an embodiment. [Figure 4] FIG. 2 is a perspective view of (a) a corrosive environment detection sensor and (b) an elastic body according to an embodiment. [Diagram 5] FIG. 2 is a top view of the corrosive environment detection sensor according to the embodiment. [Figure 6] FIG. 2 is a side view of the corrosive environment detection sensor according to the embodiment. [Figure 7] FIG. 1 is a schematic configuration diagram of a corrosive environment system according to one embodiment. [Figure 8] 11 is a graph showing a change in the resonance frequency of a leaf spring. [Figure 9] 4 is a graph showing a change in generated voltage. [Figure 10] 4 is a graph showing a change in generated voltage. [Figure 11] 11 is a graph showing a change in the resonance frequency of a leaf spring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the accompanying drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0020] (overview) Metallic materials contained in structures (e.g., rebars contained in reinforced concrete structures) may be altered by corrosion factors in the atmosphere. When metallic materials are altered, for example, the frequency of vibration of the metallic material and its surrounding parts changes even if a similar external force is applied due to a change in spring constant (hereinafter, simply referred to as "change in vibration"). The corrosive environment detection sensor according to the present disclosure focuses on the change in vibration, and a vibration sensor is attached to one end of an elastic body containing a metallic material that is altered in the same way as the metallic material contained in the structure, and another end of the elastic body is attached to the structure to monitor the corrosive environment. The corrosive environment detection sensor according to the present disclosure is smaller and easier to use than conventional devices used for monitoring corrosive environments.

[0021] (Embodiment) FIG. 1 is a schematic diagram of a corrosive environment detection sensor according to an embodiment. The corrosive environment detection sensor 100 includes an elastic body 10 made of a metal material, a vibration power generation element 20 attached to one end of the elastic body 10, and a housing 30 to which another end of the elastic body 10 is fixed. A weight 40 for adjusting the frequency may be attached to the end of the elastic body 10 to which the elastic body 10 is attached. The corrosive environment detection sensor 100 may also include a display unit (not shown) such as an LED or a monitor. The elastic body 10 is a leaf spring made of a plate-shaped metal material, but may be a coil spring.

[0022] The elastic body 10 includes a metal material that is altered by atmospheric corrosion factors. Corrosion factors include, for example, oxygen and water, and may also include sodium chloride, magnesium chloride, sodium sulfate, magnesium sulfate, and the like contained in seawater. Corrosion includes chemical erosion and the formation of so-called rust due to an oxidation reaction of metal. The metal material is preferably the same as the material contained in the monitored structure 110. Alternatively, the metal material may be a material that is altered by atmospheric corrosion factors faster than the material contained in the structure 110. The vibration of the metal material also changes as the alteration progresses. A material that is altered by atmospheric corrosion factors faster than the material contained in the structure 110 can be selected by, for example, leaving the material in an environment where the alteration of the material occurs due to the corrosion factors and performing a test to measure the change in the vibration of the material. Note that if the rate of alteration due to the corrosion factors is known, such a test is not necessary.

[0023] As such a metal material, an iron-based material that is also used as reinforcing bars for structures is preferable, and a zinc-based material can also be used. The reason why an iron-based material and a zinc-based material are preferable will be described later with reference to FIG.

[0024] In this embodiment, a vibration power generating element 20 is used as the vibration sensor. The vibration power generating element 20 generates power by vibrations in the direction of the arrow in the figure, which are generated by the elastic body 10. The vibration direction and the power generating direction of the vibration power generating element 20 may be the same. The vibration power generating element 20 is set so that the amount of power generated is greatest when the vibration of the elastic body 10 has a resonant frequency. Details of the vibration power generating element 20 will be described later.

[0025] A signal processing unit 60 connected to the vibration power generating element 20 via a connection line 50 is mounted on a circuit board within the housing 30. The signal processing unit 60 receives a voltage signal from the vibration power generating element 20 and processes the signal. A wireless device 70 is also installed within the housing 30. The wireless device 70 wirelessly transmits the processing result by the signal processing unit 60 to an external device. The external device is, for example, a monitoring terminal or a concentrator as described below.

[0026] The configuration of the corrosive environment detection sensor 100 shown in FIG. 1 and the method of mounting the sensor to the structure are merely an example and are not limited to this. For example, in this embodiment, the other end of the elastic body 10 is mounted to the structure 110 via the housing 30. However, as long as the other end of the elastic body 10 can be mounted to the structure 110, the other end of the elastic body 10 having the vibration sensor at one end may be directly fixed to the structure 110. In this case, the housing 30 may be separately mounted to the structure 110, or may be mounted to one end of the elastic body 10 together with the vibration sensor. Alternatively, the housing 30 or the vibration sensor may be mounted to the structure 110 via a jig (not shown) for fixing or amplifying vibration. In addition, a material that is difficult to deteriorate may be used for the parts other than the elastic body 10, or a coating may be applied. The mounting direction shown in the figure is also merely an example and is not limited to this.

[0027] FIG. 2 is a schematic diagram of a vibration power generating element according to an embodiment. The vibration power generating element 20 includes a fixed electrode 21 and a movable electrode 22. An electret is formed near the electrode surface of at least one of the fixed electrode 21 and the movable electrode 22. That is, the vibration power generating element 20 is a capacitance type vibration power generating element including an electret electrode. In the vibration power generating element 20, the movable electrode 22 vibrates relative to the fixed electrode 21 in response to the vibration of the elastic body 10, thereby generating power. Such an electrode structure is also called a comb-tooth structure. The vibration power generating element 20 itself has a resonance characteristic. The output voltage Vout of the vibration power generating element 20 is the largest when the resonance frequency of the system including the elastic body 10 is equal to the resonance point of the vibration power generating element 20, and is significantly reduced when the resonance frequency is shifted. That is, the output voltage of the vibration power generating element 20 is reduced as the deterioration of the elastic body 10 made of a metal material progresses. The size of the vibration power generating element 20 can be approximately 13 mm×7 mm. The configurations of the fixed electrode 21 and the movable electrode 22 are not limited to those shown in the drawings. Such a decrease in output voltage can be detected by performing a hammering test on the structure 110, or by measuring the output voltage due to environmental vibrations occurring in the structure 110.

[0028] 1, the elastic body 10 made of a metallic material has been described, but the elastic body used in the corrosive environment detection sensor 100 is not limited to this. Fig. 3 shows a cross-sectional view of an elastic body in another embodiment.

[0029] The elastic body 11 shown in Fig. 3 is configured such that a metal plate 12 is covered with a cementitious material 13 similar to that used in concrete. This configuration is similar to that of reinforced concrete, and may be used for a reinforced concrete structure to make the corrosive environment of the elastic body closer to that of the structure.

[0030] Alternatively, the elastic body may be formed from a mixture of powdered metallic material and a cementitious material similar to that used in concrete.

[0031] 4 is a perspective view of (a) a corrosive environment detection sensor 100 and (b) an elastic body 10 according to one embodiment. In the corrosive environment detection sensor 100, one end of the elastic body 10 is attached to the vibration power generation element 20, and the other end is attached to a housing 30. In addition, a weight 40 for adjusting the frequency is also attached to the same end.

[0032] Fig. 5 is a top view of the corrosive environment detection sensor 100 according to one embodiment, and Fig. 6 is a side view of the corrosive environment detection sensor 100 according to one embodiment.

[0033] 7 is a schematic diagram of a corrosive environment detection system according to an embodiment. The corrosive environment detection system 200 includes a plurality of corrosive environment detection sensors 100, a plurality of concentrators 210 each connected to the plurality of corrosive environment detection sensors 100 by wireless communication, and a monitoring terminal 230 connected to the plurality of concentrators 210 via a network 220. The monitoring terminal 230 may include a display unit. Each of the plurality of corrosive environment detection sensors 100 may be attached to a monitoring point of a structure. Cloud computing may be used for the network 220.

[0034] The concentrator 210 is a device that enables the consolidation and management of processing results of signals from the multiple corrosive environment detection sensors 100. The concentrator 210 includes a wireless device 211 and a diagnostic unit 212. The concentrator 210 may also include a display unit. The wireless device 211 receives processing results of signals wirelessly transmitted from the multiple corrosive environment detection sensors 100. The diagnostic unit 212 can compare the value of the processing result from the corrosive environment detection sensor 100 with a predetermined threshold value and, for example, determine whether the value of the processing result is equal to or greater than the predetermined threshold value. When the value of the processing result is equal to or greater than the predetermined threshold value, the diagnostic unit 212 can notify the monitoring terminal 230 of a warning. Note that the corrosive environment detection system 200 does not need to include the concentrator 210. That is, the monitoring terminal 230 and the multiple corrosive environment detection sensors 100 may directly communicate wirelessly. In this case, the monitoring terminal 230 may include a diagnostic unit. Note that the above-mentioned system configuration is merely an example and is not limited to this configuration. For example, the number of the corrosive environment detection sensors 100, the number of the monitoring terminals 230, and the number of the concentrators 210 are not limited to those shown in the figures.

[0035] According to another embodiment, the corrosive environment detection sensor 100 may use an acceleration sensor as the vibration sensor. The acceleration sensor attached to the elastic body 10 can detect the acceleration of the vibration of the elastic body 10. In this case, the signal processing unit 60 receives an acceleration signal from the acceleration sensor and performs FFT (Fast Fourier Transform) processing, and then performs a judgment. This can be performed to detect a change in frequency from the vibration in a normal state in which the elastic body 10 has not deteriorated. In this way, the vibration sensor is not limited to the vibration power generation element 20 described above, and may be any sensor that can detect a change in vibration.

[0036] (Experimental Results) The following describes the results of an experiment conducted on the corrosive environment detection sensor according to the above embodiment, which uses a vibration power generating element as a vibration sensor.

[0037] (Experiment overview) A corrosion accelerated test was conducted by exposing a steel spring (hereinafter referred to as leaf spring A (thickness 0.5 mm) or leaf spring B (thickness 0.8 mm) with a width of 21 mm, length of 30 mm, and thickness of 0.5 mm or 0.8 mm) to a salt damage environment. The salt damage environment was set to a condition in which dry-wet cycles were performed (Case 1) and a condition in which dry-wet cycles were not performed (Case 2). In Case 1, the leaf spring was immersed in a 3 wt% NaCl solution at a temperature of 40°C and a relative humidity of 95% for 4 days, then removed and dried at a temperature of 40°C and a humidity of 40% for 3 days for a total of 7 days, and the test was conducted for 13 weeks (cycles). In Case 2, the leaf spring was immersed in a 3 wt% NaCl solution at a temperature of 40°C and a relative humidity of 95% for 13 weeks. The resonant frequency of the leaf spring was measured before the start of the exposure test and after 4, 8, and 13 weeks of exposure.

[0038] Figure 8 is a graph showing the change in the resonant frequency of the leaf spring over the course of exposure. The resonant frequency is affected by the thickness of the leaf spring, with leaf spring A (thickness 0.5 mm) being lower than leaf spring B (thickness 0.8 mm), and it can be seen that the frequency is more likely to decrease over the course of exposure. Comparing cases 1 and 2, it can be seen that the repeated dry and wet environment accelerates the rate at which corrosion of the leaf spring progresses, making it more likely to cause a decrease in frequency.

[0039] In addition, a mortar specimen was created with a rebar placed at the axial center, measuring 140 mm in length, 40 mm in height, and 40 mm in width. The natural potential of the rebar inside the mortar specimen was measured once a week in the above-mentioned exposure environment using a saturated copper sulfate reference electrode as a reference electrode. A simulation was also carried out of the voltage output expected when a vibration power generation device is attached to the end of a leaf spring. A sine wave (amplitude 0.5 m / sec) equivalent to the resonant frequency of the leaf spring was generated. 2 ) is input, and the charged electret element and the comb-tooth structure of the electrode are driven based on the vibration behavior of the leaf spring, causing a transfer of charge, which can be extracted as a voltage by connecting it to an external load (10 MΩ).

[0040] Figures 9 and 10 show the results of the generated voltage obtained from the numerical simulation results of vibration power generation and the change in the natural potential of the rebar in the mortar specimen when leaf spring A and leaf spring B were used. In the calculation simulation of the generated voltage obtained from the vibration power generation device attached to each leaf spring, the resonance frequency was set to 115 Hz (leaf spring A) and 212 Hz (leaf spring B). The actual measured values ​​of the resonance frequency of the leaf spring in the initial state were approximately 110 Hz (leaf spring A) and approximately 180 Hz (leaf spring B), and the generated voltage of the vibration power generation device decreases due to the decrease in the resonance frequency associated with the progress of corrosion of the leaf spring. In addition, in case 1 (with repeated dry and wet cycles), the natural potential of the rebar in the mortar specimen decreases over time compared to case 2 (without repeated dry and wet cycles), and it can be seen that this corresponds well to the change in the generated voltage. From the above, it can be said that there is a strong correlation between the deterioration factors of salt damage progression in the environment and the progress of rebar corrosion inside the mortar due to environmental conditions, and the corrosion behavior of the leaf spring and the decrease in the resonance frequency. In other words, it is seen that the corrosive environment detection sensor according to the present disclosure is effective as a sensor for monitoring steel corrosion and salt damage environments in reinforced concrete structures.

[0041] (Consideration of metal types) Next, we will explain the experiment conducted to find the metal material suitable for the leaf spring. Here, leaf springs were formed from iron (Fe), copper (Cu), zinc (Zn), and aluminum (Al), and vibration sensors using the leaf springs were exposed to air at a temperature of 40°C and humidity of 95% for 8 weeks. The exposure was performed while the leaf springs were covered with a sheet (cloth) impregnated with a 3% aqueous solution of NaCl. The size of the leaf springs was 10 mm wide x 20 mm long x 0.6 mm thick.

[0042] Fig. 11 is a graph showing the change in resonance frequency over time for leaf springs made of different metals. As shown in the figure, compared to leaf springs made of copper (Cu) and aluminum (Al), the resonance frequency of leaf springs made of iron (Fe) and zinc (Zn) changes significantly over time. As shown, since the resonance frequency changes more significantly, iron-based and zinc-based materials are more preferable metal materials for use in leaf springs than copper-based and aluminum-based materials.

[0043] As described above, the corrosive environment detection sensor according to the present disclosure provides the following advantageous effects.

[0044] (1) It is smaller and easier to use than conventional devices used for monitoring corrosive environments. (2) The device can be installed closer to the monitoring point of the structure than conventional devices used for monitoring corrosive environments, thereby improving the accuracy of detecting corrosive environments. (3) By using the same metal material as the elastic body as the metal material that constitutes the structure, the accuracy of detecting corrosive environments can be improved. (4) Alternatively, by using a metal material used as the elastic body that is altered by atmospheric corrosion factors more quickly than the metal material that constitutes the structure, the progression of the alteration can be detected at an early stage. [Explanation of symbols]

[0045] 10, 11 Elastic body 12 metal plate 13 Cement-based materials 20 Vibration power generation element 21 Fixed electrode 22 Movable electrode 30 Case 40 Weight 50 Connection Line 60 Signal Processing Section 70 Radio equipment 100 Corrosive environment detection sensor 110 Structures 200 Corrosive Environment Detection System 210 Concentrator 211 Radio equipment 212 Diagnostic Department 220 Network 230 Monitoring terminal

Claims

1. an elastic body including a metal material that is altered by a corrosive factor in the atmosphere; A vibration sensor attached to the elastic body; a signal processing unit that processes a signal from the vibration sensor; A housing including the signal processing unit; A corrosive environment detection sensor comprising:

2. 2. The corrosive environment detection sensor according to claim 1, wherein the metallic material is the same as a material contained in a structure to be monitored.

3. 2. The corrosive environment detection sensor according to claim 1, wherein the metallic material is a material that is altered by the corrosive factor in the atmosphere more quickly than a material contained in a structure to be monitored.

4. 2. The corrosive environment detection sensor according to claim 1, wherein the vibration sensor is an acceleration sensor.

5. 2. The corrosive environment detection sensor according to claim 1, wherein the vibration sensor is a vibration power generating element.

6. 2. The corrosive environment detection sensor according to claim 1, further comprising a wireless device that wirelessly transmits a result of processing by the signal processing unit.

7. 2. The corrosive environment detection sensor according to claim 1, further comprising a display unit.

8. The corrosive environment detection sensor according to any one of claims 1 to 7, a monitoring terminal including a display unit, the monitoring terminal being communicatively connected to the plurality of corrosive environment detection sensors; A corrosive environment detection system comprising:

9. A concentrator communicatively connected to the plurality of corrosive environment detection sensors is further provided.

9. The corrosive environment detection system according to claim 8, wherein the monitoring terminal is communicatively connected to the concentrator.

10. The corrosive environment detection system according to claim 9 , wherein the concentrator further comprises a display unit.

11. 10. The corrosive environment detection system according to claim 9, wherein the concentrator includes a determination unit that determines whether a value of the processing result from the signal processing unit is equal to or greater than a predetermined threshold value.

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