JP2007263674A - Crack detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crack detection sensor for reducing the crack keeping control cost of a steel structure to aim labor saving in consideration of the point at issue of a crack detection method due to a linear sensor or a crack detection tape being a conventional method because crack monitoring is important from an aspect of the maintenance and control of the steel structure, a measuring instrument using the crack detection sensor, a measuring method using the crack detection sensor and a manufacturing method of the crack detection sensor. <P>SOLUTION: The crack detection sensor is equipped with a sensor element of which the electric resistance value is increased by the occurrence and development of the crack of a structure, a measuring circuit for measuring the electric resistance value of the sensor element, an antenna for taking in drive power in a non-contact state from an external activator and a communication circuit for transmitting the electric resistance value to the activator in a non-contact state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crack detection technique that is formed on the surface of a monitoring object that is predicted to generate cracks, and that monitors the occurrence of cracks in the monitoring object and the progress of the cracks.

  In steel structures, fatigue cracks occur at sites where tensile loads are applied due to repeated loads. Even in the initial stage, even a small crack can grow by being continued repeatedly, eventually leading to large deformation and brittle fracture. For the purpose of preventing such serious troubles, if there is a risk of exceeding the degree of deformation allowed for each deformed part, construction is being carried out for repair and reinforcement. Normally, the seriousness of steel structures progresses over several years, so there is no need to repair or reinforce immediately when deformation occurs. In addition, since the progress may stop in the middle of the deformation, it is necessary to monitor the progress after the occurrence of the deformation in order to determine the necessity of repair or reinforcement.

  Until now, various methods for monitoring cracks in steel structures have been developed for the above purpose. For example, in Patent Document 1, one linear sensor continuous in an area where fatigue cracks are likely to occur is bent and pasted into a wave shape, and the breakage of this sensor due to cracks is constantly energized to measure data in a data logger. It describes a system that accumulates and transmits wirelessly to remote locations. However, actual structures are complicated in structure, and there are usually dozens of places where there are concerns about fatigue cracks in actual bridges, etc., which are often separated from each other. Therefore, placing one continuous linear sensor is wasteful and extremely complicated. In addition, in order to measure the sensors installed at these many locations and record and save the data, it is necessary to install measuring equipment that requires a 100V power supply. It is also necessary to maintain and manage these devices at all times. Therefore, in such a measurement system, both initial investment and running costs are high and have not been widely adopted.

  Patent Document 2 discloses that a tape for the purpose of facilitating crack detection by being attached to an area where a tunnel is liable to crack is sandwiched between two upper and lower insulating layers to cover the bottom layer. Describes a crack detection tape and a crack detection system having an adhesive layer for bonding to an object. However, although this crack detection tape can detect the occurrence of cracks, it cannot monitor the process of crack growth and growth. In many cases, existing structures already have some cracks, and how these cracks develop over time is a major issue in maintenance. In addition, as in Patent Document 1, it is necessary to arrange and maintain a large number of power supplies and measuring devices, and the initial investment and running costs are high.

JP 2004-75301 A "Fatigue Crack Monitoring System for Structures" Japanese Patent Laid-Open No. 2005-91167 “Crack Detection Tape and Crack Detection System” 78

  Monitoring cracks is an important issue in the maintenance and management of steel structures. In order to implement this, the conventional means requires a lot of cost for installing the sensor, installing a large data logger, a data recording device, a communication device, and a power source. In particular, it becomes more difficult to work in places with high or narrow locations to be monitored, and in remote locations, power supply preparation is also a heavy burden. In addition, the maintenance costs for these devices over a long period of time are also significant.

  In view of such a situation, in the present invention, a crack detection sensor aiming at low cost and labor saving, which contributes to reduction in crack maintenance cost of a steel structure, a crack measuring device and a crack measuring method using the crack detection sensor, It is another object of the present invention to provide a method for manufacturing a sensor element for a crack detection sensor.

In the present invention, the following is defined.
(1) A sensor element whose resistance changes due to the occurrence and development of a crack in the crack detection structure, a measurement circuit that measures the electrical resistance value of the sensor element, and an antenna that captures drive power from an external activator in a non-contact manner A crack detection sensor comprising: a communication circuit that transmits the electrical resistance value to the activator in a contactless manner.

(2) The sensor element has one or a plurality of conductors or resistors covered with an electrically insulating member, and two or more electrical resistance measurement terminals connected to the conductors or resistors. The crack detection sensor as described in (1) characterized by these.

(3) The one or more conductors or resistors are linear, and have the electric resistance measurement terminals at both ends, and the measurement circuit includes the electric current of each conductor or resistor. The crack detection sensor according to (2), wherein a resistance value is measured.

(4) having a plurality of the conductors or resistors, the plurality of conductors or resistors being linear and having the electrical resistance measurement terminal at one end of each side; The other end portion is connected to each other and has one common electric resistance measurement terminal. The crack detection sensor according to (2),

(5) Having a plurality of the conductors or resistors, the plurality of conductors or resistors are linear and form a parallel circuit, and the electrical resistance measurement terminals are provided at both ends of the parallel circuit. (2) The crack detection sensor according to (2).

(6) The crack detection sensor according to (2), wherein, in the sensor element, the conductor or the resistor has a strip shape and has terminals for measuring electrical resistance at both ends of the strip resistor.

(7) The crack detection sensor according to any one of (1) to (6), wherein the conductor or the resistor is formed of a conductive paint.

(8) The crack detection sensor further includes a memory for storing at least one of an identification code unique to the crack detection sensor and an identification code unique to the sensor element, and the communication circuit adds to the electrical resistance value. The crack detection sensor according to any one of (1) to (7), wherein the crack detection sensor has a function of transmitting the identification code.

(9) A crack measuring apparatus using the crack detection sensor according to any one of (1) to (8), wherein driving power is sent to the crack detection sensor and the crack detection sensor in a non-contact manner. And an activator having a function of receiving at least one of an identification code unique to the crack detection sensor or an identification code unique to the sensor element and the electrical resistance value or the electrical resistance value in a non-contact manner. A crack measuring device.

(10) A method for measuring crack initiation and propagation using the crack measuring apparatus according to (9), wherein the crack detection sensor is attached to a structure, and driving power is not applied to the crack detection sensor from the activator. A method for measuring cracks, characterized by transmitting the contact and receiving the electrical resistance value of the sensor element or the electrical resistance value and the identification code in a non-contact manner and measuring the occurrence or progress of cracks in the structure. .

(11) A method for manufacturing a sensor element in a crack detection sensor according to (7), wherein an electrical resistance measurement terminal is mounted on a sheet-like electrical insulating member, and a predetermined circuit line portion is cut through the electrical resistance measurement terminal. After the shielding plate is placed, a conductive paint is applied to form a conductor or a resistor on the circuit line portion, and the formed conductor or resistor is further covered with an electrical insulating member. A method for manufacturing a sensor element for a detection sensor.

(12) A method for manufacturing a sensor element in a crack detection sensor according to (2), wherein a metal material is bonded onto a sheet-like electrical insulating member, a photosensitive resist is applied thereon, The circuit line portion is transferred onto the photosensitive resist by exposure through the light shielding plate on which the circuit line portion is drawn, and then the exposed portion and the unexposed portion are transferred to the photosensitive resist. The conductive resist is removed, and the metal material portion exposed by removing the photosensitive resist is removed by etching to form the conductor or resistor, and an electrical resistance measurement terminal is attached to the conductor or resistor. Then, a sensor element is formed by covering the top with an electrically insulating member to form a sensor element.

By using the present invention, it is possible to easily measure the crack growth of a structure at a high place or in a narrow place without contact, and it is possible to measure for a long time even under conditions without a power source or battery. Management such as repair and maintenance can be carried out easily.
The crack detection sensor, crack measurement device, crack measurement method, and method for manufacturing a sensor element for a crack detection sensor according to the present invention can monitor cracks in many structures at low cost.

  The crack detection sensor of the present invention includes a sensor element whose electrical resistance value increases as a result of crack generation and development of a crack detection structure, a measurement circuit for measuring the electrical resistance of the sensor element, and an external activator in a non-contact manner. An antenna for taking in drive power and a communication circuit for transmitting the electrical resistance to the activator in a contactless manner are provided.

  Figure 1 shows the configuration. An electromagnetic wave is received from the antenna 8 connected to the transmission / reception circuit 9 of the activator 7, and an electromotive force is obtained by electromagnetic induction by the transmission / reception antenna 3 in the crack detection sensor 1. Based on this electric power, the measurement circuit 4 measures the electric resistance value of the sensor element 2 for detecting cracks. The measured value is converted into transmission data by the communication circuit 5 and sent to the antenna 8 of the activator 7 via the transmission / reception antenna 3.

  Here, FIG. 1 shows an example in which the antenna for transmitting and receiving data and reception of electromagnetic force for driving power is used as the transmitting and receiving antenna 3, but both can be provided separately. Further, the transmission / reception antenna 3 may be an antenna capable of receiving data such as an identification number sent from the activator 7.

  The AC frequency used for power transmission / reception and communication between the activator 7 and the crack detection sensor 1 is not particularly limited, but the 125 kHz band and 13.56 MHz band can be used depending on the purpose according to regulations of the Radio Law.

  The activator used in the present invention is not particularly limited as long as it has a function of transmitting an alternating current to the crack detection sensor to induce an electromotive force and reading data transmitted from the crack detection sensor. . For example, commercially available products such as the RX2100 manufactured by Yoshikawa AR System for the 125kHz band can be used, and the RX-TP-RW01 manufactured by Yoshikawa AR System can also be used for the 13.56MHz band.

  It should be noted that the crack detection sensor according to the present invention has no problem even if it is an integrated type, or the sensor element and the antenna, the communication circuit, and the measurement circuit are separated and electrically connected to each other. The features of the present invention will be described below.

  First, in the crack detection sensor of the present invention, the sensor element has one or more conductors or resistors covered with an electrically insulating member, and two or more electrical resistance measurements connected to the conductors or resistors. And a terminal for use.

  FIG. 2A shows an example of the sensor element 2 in the crack detection sensor of the first embodiment. Reference numeral 13 denotes a part of a metal weld of the structure. In FIG. 2A, a single linear conductor or resistor 10 forming an electric circuit is fixed with an adhesive on an electrical insulating material 11 adhered to the surface of the structure 13 with an adhesive or the like. The electrical resistance measuring terminals 12 are attached to both ends of the electrical circuit portion formed by covering the electrical circuit portion with the electrical insulating member 11. Further, a state in which the crack 14 is in the vicinity of the sensor element 2 is also shown. In this example, for example, the conductor or resistor 10 is formed in a substantially U shape, and the two electrical measurement terminals 12 are close to adjacent positions. The electrical insulation member 11 is first cut by the development of cracks, and the electrical circuit fixed on the electrical insulation member 11 is cut by further development of cracks. Therefore, if the electrical resistance measurement terminals 12 attached to both ends of the electrical circuit are connected to the measurement circuit 4 and the resistance is measured, the resistance is changed to infinity due to the electrical circuit being disconnected, and a crack is generated. Alternatively, it can be easily detected that the crack progress has reached the position of the sensor element 2. Usually, the electric circuit length 26 is preferably about 5 mm to 100 mm in consideration of the crack size and workability of the structure.

  Next, in the crack detection sensor of the second embodiment of the present invention, in the sensor element, one or a plurality of conductors or resistors are linear, and electric resistance measurement terminals are provided at both ends. And a measuring circuit measures an electric resistance value of each conductor or resistor.

  An example of this structure is shown in FIG. In this figure, a plurality of linear conductors or resistors 10 forming an electric circuit have electric resistance measuring terminals 12 at both ends, and these are running side by side. Then, by separately preparing a measurement circuit for measuring the electric resistance value of each electric circuit, it is possible to detect crack generation and progress from the respective resistance value changes.

  Next, in the crack detection sensor of the third embodiment of the present invention, in the sensor element, a plurality of conductors or resistors are linear, and an electric resistance measurement terminal at one end of each side. Each of the other ends is connected to each other and has one common electric resistance measurement terminal.

  An example of this structure is shown in FIG. In this figure, a plurality of linear conductors or resistors 10 forming an electric circuit are running side by side, each having an individual electric resistance measuring terminal 12 at one end on one side, and the other side. One common electric resistance measuring terminal 16 connected to each other is provided at the end. With this structure, a plurality of electrical resistance measurement terminals on one side in FIG. 2B can be combined into one, and wiring can be simplified. In the measurement using the sensor element 2, a plurality of electrical resistance measurement terminals 12 are connected to the measurement circuit 4, and the resistance between the common electrical resistance measurement terminal 16 and each electrical resistance measurement terminal 12 is sequentially measured. Take a technique. In this sensor element 2, the crack 14 sequentially cuts the circuit as it progresses, so it is possible to monitor how far the crack has progressed. Therefore, it is possible to calculate the crack growth rate by knowing how many lines were cut within a certain measurement cycle period by appropriately setting the interval of multiple lines in the electric circuit according to the purpose. It becomes.

  Next, in the crack detection sensor of the fourth embodiment of the present invention, in the sensor element, a plurality of conductors or resistors are linear and form a parallel circuit, and are formed at both ends of the parallel circuit. It has an electrical resistance measurement terminal.

  An example of this structure is shown in FIG. In this case, a plurality of linear conductors or resistors 10 are arranged in parallel, and one end of each line is connected to one common electrical resistance measurement terminal 16, and the other side is also another common. Are connected to the electric resistance measuring terminal 16 to form a parallel type electric circuit. In the measurement using the sensor element 2, two common electric resistance measurement terminals 16 are connected to the measurement circuit 4 to measure the resistance of the parallel electric circuit. In this sensor element 2, the circuit is sequentially cut as the crack 14 progresses, so that the resistance of the electric circuit gradually changes, and the progress of the crack can be monitored from this change. Therefore, it is possible to calculate the crack growth rate by knowing how many lines were cut within a certain measurement cycle period by appropriately setting the interval between multiple lines of the electric circuit according to the purpose. It becomes. In general, the distance is preferably about 0.5 mm to 10 mm in the case of a steel structure and about 5 mm to 50 mm in the case of a concrete structure in consideration of the crack size of the structure. In this figure, the lengths and widths of the plurality of linear conductors or resistors 10 arranged in parallel are the same, but the lengths and widths are not necessarily the same. It is also effective to change the length and width according to the purpose such as a large change in resistance value caused by cutting the parallel resistance circuit.

  Next, a crack detection sensor according to a fifth embodiment of the present invention is characterized in that, in the sensor element, the conductor or the resistor has a strip shape, and has terminals for measuring electrical resistance at both ends of the strip resistor. And

  An example of this structure is shown in FIG. In this example, a strip-like conductor or resistor 17 that forms an electric circuit is pasted with an adhesive on the electrical insulating member 11 stuck on the surface of the structure, and two locations of the strip-like conductor or resistor 17 ( The sensor element 2 is shown with electrical resistance measuring terminals 12 connected to both ends in the figure. In the measurement using the sensor element 2, two electric resistance measurement terminals 12 are connected to the measurement circuit 4 to measure the resistance of the electric circuit. Since the conductor or resistor 17 has a strip shape, there is an advantage that it can be easily positioned and fixed with an adhesive or the like on the surface of the structure. Further, by using the sensor element 2 as a strip-shaped conductor or resistor 17, the strip-shaped resistor 17 is gradually cut with the progress of the crack 14, and accordingly, the electric circuit resistance gradually increases. Become. It is also possible to monitor the progress of crack growth from this resistance value. By obtaining the relationship between crack length and electrical circuit resistance as a calibration curve in advance, quantitative crack growth evaluation becomes possible. The electrical resistance measurement terminal 12 is not necessarily required to be a strip-shaped conductor or both ends of the resistor 17, and may be anywhere as long as a change in resistance is detected due to the occurrence of a crack.

  Next, a crack detection sensor according to a sixth embodiment of the present invention is characterized in that the conductor or resistor is formed of a conductive paint in the sensor element. By using a conductive paint for the conductor or resistor of the sensor element, the conductive surface of the structure can be bumped with a brush or brush on the electrically insulating layer formed of the paint on the surface of the structure. It is possible to freely form an electric circuit according to the state. Here, the conductive paint is an acrylic resin, polyurethane resin, epoxy resin, ferroelastomer, cellulose, potassium silicate, PVB, PVC, etc. binder as conductive particles such as graphite, carbon black, nickel, aluminum, silver, copper, Silver-plated copper or the like is added and kneaded. Particularly preferably, a conductive paint obtained by kneading nickel particles in an acrylic resin is cured at room temperature and has a high heat resistance and is easy to handle.

  All of the sensor elements of the crack detection sensor shown in FIGS. 2, 3, and 4 show only a single sensor element. However, some structures require crack detection over a range of tens of centimeters. In some cases, crack monitoring is required at several locations. For this purpose, FIG. 5 shows an example of an embodiment in which a plurality of sensor elements having two ends are used to monitor cracks. In FIG. 5A, four vertical sensor elements 2 are arranged in parallel in the horizontal direction at regular intervals, and one end of one side of the sensor element 2 is connected to a common electrical resistance measurement terminal 16. An example is shown in which one end of the other side is connected to an individual electrical resistance measurement terminal 12. In this figure, the sensor element 2 is arranged so as to place an existing crack 14 in the middle. Therefore, when the crack grows and the sensor element interval is exceeded, the electric circuit is cut off, which can be used for the management of a certain crack length. In general, the distance between the sensor elements is preferably 10 mm to 100 mm in consideration of the supervision limit length of cracks in the structure.

  In FIG. 5 (b), four sensor elements 2 arranged in a horizontal direction are arranged in a row in the horizontal direction, one end of one side of the sensor element 2 is connected to a common electrical resistance measurement terminal 16, and the other side. An example in which one end of each side is connected to an individual electrical resistance measurement terminal 12 is shown. For example, when the crack monitoring section length is 40 cm, four sensor elements 2 having an electric circuit length of 10 cm are used. This arrangement is effective when it is difficult to predict where the crack will occur in the control section.

  In FIG. 5C, four vertical sensor elements 2 are arranged in parallel in the horizontal direction at regular intervals, and one end of one side of the sensor element 2 is connected to a common electrical resistance measurement terminal 16. An example in which each one end on the other side is also connected to another common electric resistance measurement terminal 16 is shown. In this figure, the sensor element 2 is arranged so as to place an existing crack 14 in the middle. Therefore, when the crack grows and the sensor element interval is exceeded, the electric circuit is cut, and this resistance change can be used to manage a certain crack length.

  In FIG. 5 (d), four horizontal sensor elements 2 are arranged in a row in the horizontal direction, one end of each side of each sensor element 2 is connected to a common electric resistance measurement terminal 16, An example is shown in which each one end on one side is connected to an individual electrical resistance measurement terminal 12. For example, when the crack monitoring section length is 40 cm, four sensor elements 2 having an electric circuit length of 10 cm are used. This arrangement is effective when it is difficult to predict where the crack will occur in the control section. In this example, the number of sensor elements is four, but it is effective to increase or decrease the number according to the purpose.

  Although FIG. 5 shows an example in which a plurality of sensor elements are arranged in parallel or in a row, the crack detection sensor of the present invention can be used by stacking a plurality of sensor elements. An example is shown in FIG. In this example, for example, each of the two sensor elements 2 has a configuration in which a plurality of linear conductors or resistors 10 are arranged in parallel, and these two sensor elements 2 are connected to each other's conductors or resistors 10. They are stacked one above the other so that they intersect at right angles in a grid pattern. Here, the resistors 10 at the lattice points are insulated from each other. By using this arrangement, it is possible to detect what kind of propagation path the crack that propagates two-dimensionally on the surface of the structure will follow by identifying and tracking each cutting point of the sensor elements arranged in two directions. Is possible. Such a sensor element is effective when the crack occurrence region of the structure can be roughly specified, but the detailed position and orientation cannot be specified.

  As described above, the sensor element described in FIGS. 2, 3 and 4 is an example of applying the principle that the electric circuit is directly cut by the progress of the crack, but the electric circuit is not necessarily cut directly by the crack. There is no need. By attaching the sensor element in the vicinity where cracks are expected to occur, cracks or even member deformations may occur depending on the principle that changes in strain occur due to cracks or changes in the stress state and the resistance of the electric circuit changes. It can be detected.

Next, materials used for the sensor element of the present invention will be described. The conductor of the present invention means a substance having a specific resistance of about 1.0 × 10 ⁻⁶ Ωcm to about 30.0 × 10 ⁻⁶ Ωcm, and the resistor is a ratio of about 10 ⁶ Ωcm or more above the conductor. It means having resistance. As the conductor, a metal material is easy to process, and copper and copper alloy are most suitable, but aluminum, iron, zinc, tin, lead, brass, platinum, silver, nickel, and alloys thereof may be used. As the resistor, nickel, nichrome, manganese, antimony, and alloys thereof and the above-described conductive paints can be applied. However, copper nickel alloys and nichrome alloys are preferable because they are common and easily available.

Next, a material (electrical insulating member 11) for electrically insulating and covering the conductor or resistor of the sensor element or an insulating material used for electrically insulating the structure and the sensor element will be described. The insulating material is not particularly specified, but is preferably a material having a specific resistance of 10 ⁶ Ωcm or more, having a certain degree of elasticity, and capable of being affixed to the surface of uneven parts such as welds. Epoxy resin, urethane resin, acrylic resin, polyimide resin, phenol resin, polyester resin, silicon resin, polyethylene resin, enbi, teflon, raw rubber, soft rubber, butyl rubber, neoprene rubber can be used.

  Moreover, when using as a coating, coatings, such as an epoxy resin, a urethane resin, an acrylic resin, can be used. Among them, when used in the form of a sheet, an epoxy resin and a polyimide resin are preferable because they are easily available, and when used as a coating, an epoxy resin and an acrylic resin coating are preferable because they are easy to handle.

  Next, as an embodiment of the crack detection sensor of the present invention, an identification code (hereinafter referred to as “identification code”) is provided in the crack detection sensor in preparation for using a plurality of crack detection sensors. An example will be described which has a function of storing data and further has a function of transmitting this identification code to the activator in a non-contact manner.

  As a result, when a plurality of crack detection sensors are used, it is possible to identify which crack detection sensor the data of the electrical resistance value transmitted to the activator is transmitted from.

  As a memory function of the identification code, for example, a circuit for storing an identification code of 8 digits or more in hexadecimal can be held in the communication circuit of each crack detection sensor. This makes it possible to individually identify individual measurement values of a plurality of crack detection sensors installed. In this case, specifically, an identification code set in advance is transmitted as an electromagnetic wave via the transmission / reception antenna of the activator, which is received by the transmission / reception antenna of each crack detection sensor and stored in the memory in the communication circuit.

  As another embodiment, as shown in FIG. 7, a plurality of sensor elements 27 can be provided in the crack detection sensor 1. In this case, an identification code may be assigned to each of the plurality of sensor elements 27. Each sensor element 27 is connected to a multiplexer 28 having an identification code for each channel, and the identification code is assigned to each sensor element 27. The identification code of the sensor element 27 can also be determined.

  And it becomes possible to identify the electrical resistance value of each sensor element 27 by transmitting the identification code and the electrical resistance value at the same time. In FIG. 7, four sensor elements 27 are connected to a multiplexer 28. The multiplexer 28 sequentially switches each sensor element 27 to transmit the electrical resistance value and the recognition code measured by the measurement circuit 4 for each sensor element 27 from the communication circuit 5 to the activator via the transmission / reception antenna 3.

  These identification codes can be stored in advance in the crack detection sensor 1 at the time of factory shipment, for example, but after the sensor is set on the structure to be measured, data is transmitted from the activator to detect cracks. It can also be stored in a memory in the communication circuit 5 of the sensor 1.

  Furthermore, a combination of assigning an identification code to each crack detection sensor and further assigning an identification code to each sensor element existing in the crack detection sensor is also possible.

  An embodiment according to the crack measuring apparatus of the present invention will be described. This device sends the drive power to the crack detection sensor and the sensor in a non-contact manner, and the electrical resistance value of each conductor or resistor constituting the sensor element and the identification code of the sensor element itself in a non-contact manner. And an activator having a receiving function.

  Furthermore, an embodiment according to a crack measuring method using the crack measuring apparatus of the present invention will be described. The present embodiment is a crack detection method using a passive and non-contact type crack detection device, wherein the crack detection sensor is attached to a structure, and driving power is sent to the sensor in a non-contact manner from an activator. In addition, the present invention is a passive and non-contact type crack detection method for detecting a crack in a structure by receiving each electrical resistance value of a conductor or a resistor constituting a sensor element in a non-contact manner.

  Furthermore, in the present invention, as a first method of manufacturing a sensor element in a crack detection sensor, an electrical resistance measurement terminal is attached on a sheet-like electrical insulation member, and a shield plate that is cut through a predetermined circuit line portion thereon is provided. After the mounting, a conductive paint is applied to form the conductor or resistor, and the formed conductor or resistor is covered with an electrically insulating member.

  FIG. 8 shows an example of the manufacturing method. In this example, the electrical resistance measuring terminal 12 is mounted on the sheet (FIG. 8A) made of the electrical insulating member 11 described above (FIG. 8B), and the circuit line portion of the electrical circuit is mounted thereon. A shield plate 19 that has been cut through is placed (FIG. 8 (c)), and a conductive circuit 20 is applied to form a measurement circuit (FIG. 8 (d)). Further, a surface insulating sheet 21 is formed on the upper layer of the electric circuit. A procedure of a method of forming a sensor element by attaching (FIG. 8E) is shown. Here, the blocking plate 19 is made of paper, various plastics, or vinyl sheets.

  Further, in the present invention, as a second manufacturing method of the sensor element in the crack detection sensor, a metal material that forms a conductor or a resistor is bonded on the sheet-like electrical insulating member, and further on the adhesive. After coating the photosensitive resist, the circuit line portion is transferred onto the photosensitive resist by exposure through a light shielding plate on which a predetermined circuit line portion is drawn, and then transferred to an exposed portion and an unexposed portion. , Removing the photosensitive resist in the exposed part or the unexposed part, and further removing the metal material part exposed by removing the photosensitive resist by an etching process to form the conductor or resistor. Alternatively, the sensor element is formed by attaching an electrical resistance measurement terminal to the resistor and further covering the terminal with an electrical insulating member.

  As a method for adhering a metal material onto the sheet-like electrical insulating member, for example, a method of using a thermosetting resin as an electrical insulating material and pressing the metal material with a roll or the like can be applied.

  FIG. 9 shows an example of the manufacturing method. In this example, after a metal material 22 is bonded onto the sheet (FIG. 9A) made of the electrical insulating member 11 described above (FIG. 9B), a photosensitive resist 23 is applied thereon. (FIG. 9 (c)), a light shielding plate 19 depicting a circuit line portion of an electric circuit (a portion other than the circuit line portion is made light transmissive) is set on the upper portion (FIG. 9 (d)), The photosensitive resist portion other than the circuit line portion is altered to be soluble by exposure (FIG. 9E) (24 indicates the photosensitive resist portion altered to be soluble), and then the soluble photosensitive property. The resist is removed with a developer, and the lower layer metal material is removed by an etching method or the like to form a measurement circuit 25 (FIG. 9 (f)), and an electric resistance measurement terminal 12 is attached to the circuit end (FIG. 9). (G)) Furthermore, a surface insulating sheet 21 as an electrically insulating member is attached to the surface of the electric circuit. That (Fig. 9 (h)) to form a sensor element by.

  This is a positive type manufacturing example in which the photosensitive resist in the portion other than the circuit line portion irradiated with light is dissolved and removed by exposure, but conversely, the circuit line portion has light transmittance. The light shielding plate may be a negative type in which a portion other than the circuit line portion that is not irradiated with light is removed.

  As the metal material 22 shown in FIG. 9, stainless steel material, copper, aluminum and alloys thereof are generally used, but iron nickel alloy, iron cobalt nickel alloy, silver, molybdenum, tungsten, titanium and the like may be used. The photosensitive resist 23 is generally called a photoresist, and a solution obtained by mixing a novolac type phenol resin with a photosensitive agent and an organic solvent can be used. Here, the light blocking plate 19 is also called a photomask, and a photographic film in which a circuit is burned is used. As a developer, an ammonium salt solution is generally used, and in etching, a mixed solution of iodine, alkali iodide and an organic solvent is generally used. However, a mixed solution of hydrochloric acid and nitric acid may be used depending on the purpose. it can.

  The structure to which the crack detection sensor is attached is a structure that may cause problems due to deterioration due to cracks, such as land structures such as bridges, roads, and tunnels, and buildings such as buildings, gymnasiums, and stadiums. This includes social capital represented by water, rivers, harbors, seawalls, etc., and private capital such as ships, power plants and factories. As a method for affixing to these structures, a method such as affixing with an adhesive or a sticking material, a bolt connection considering electric insulation, or a method of directly embedding in the structure is appropriately selected. As for the attachment position, the part where the crack is concerned, the fluctuating stress is high, the stress concentration is high, the part where the deformation is large, the part where the member is welded and pressed, the joint of the concrete, etc. are suitable. Actual measurement conditions are shown below.

  FIG. 13 and FIG. 14 show the state of an operator who performs resistance measurement with an activator when a crack progresses after the crack detection sensor is installed. FIG. 13 shows an example in which the crack detection sensor 1 is installed in the welded portion of the bridge and measurement is performed by the activator 7 held in the hand. FIG. 14 shows the crack detection sensor 1 installed in the welded portion inside the rotating body. This is also an example in which measurement is performed with the activator 7 held in hand. In either case, the distance between the crack detection sensor 1 and the activator 7 varies depending on the frequency used and the situation of surrounding radio waves, but is usually 20 to 50 cm.

  The preferred embodiment of the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to such an example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the spirit described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

  The outline of the fatigue test conducted in order to confirm the function of the crack detection sensor of this invention is described. FIG. 10 shows a fatigue test body 29 that simulates a part of a steel structure. An out-of-plane gusset 31 is joined to the main member 30 by welding. The fatigue test body 29 has a length of 500 mm, a plate width of 70 mm, a plate thickness of 15 mm, and the gusset 31 has a length of 70 mm, a plate width of 50 mm, and a plate thickness of 10 mm. Reference numeral 32 denotes a sensor attaching portion. FIG. 11 shows a diagram in which the sensor element 2 of the present invention is attached to the toe of the welded portion 33 of the gusset 31 of FIG. 10 for the purpose of monitoring fatigue cracks.

Sensor element 2 consists of a conductive resin FC-415 (containing carbon powder, specific resistance 0.2 Ωcm) manufactured by Fujikura Kasei Co., Ltd. on a polyimide resin sheet (25 mm wide, 30 mm long, 13 μm thick) as an insulating material. An electric circuit composed of six bodies (thickness 50 μm, width 1 mm, length 20 mm) was formed, and further covered with a polyamide resin sheet serving as an insulating material on the circuit. The interval between the parallel lines of the electric circuit was 5 mm. This was connected to a measurement circuit, a communication circuit, and a circuit fabricated by sealing an antenna, and a crack detection sensor was fabricated. This crack detection sensor was bonded to the toe of the weld 33 in FIG. 11 using an adhesive. In the fatigue test, a stress amplitude of 150 Mpa was applied to the main member 30 in a cycle of 10 ⁵ times a day, and the resistance value was measured once every 2 days using a reader / writer (RX2100) manufactured by Yoshikawa Arf System as an activator. .

  Table 1 shows the measured electrical resistance and the number of confirmed circuit breaks for the number of fatigue cycles N on the measurement date.

  FIG. 12 is a graph showing the measured electric resistance value with respect to the fatigue repetition number N shown in Table 1. On the 6th day after the start of the test, the resistance change was confirmed, and when the tester was stopped, the occurrence of cracks was confirmed. After that, a sudden change in resistance was measured, and on the last 10th, the resistance became 202.0Ω, and it was confirmed from observation results that five electrical circuits were cut. As a result, it was proved that the crack detection sensor of the present invention functions sufficiently and that crack detection is easily performed.

In this experiment, it was calculated that the fatigue repetition number was 2 × 10 ⁵ times in 2 days and the crack propagation distance was about 15 mm in the final stage. In the future, the crack growth rate is expected to grow at a speed of 7.5 mm / day or more. For structures with such welds, if the crack management limit length is 50 mm, a simple calculation of 7 It is assumed that the limit will be reached in about days. Therefore, if the crack detection sensor of the present invention is used, the maintenance and management of the structure can be saved, and the future repair timing can be easily predicted.

  INDUSTRIAL APPLICABILITY The present invention is useful when detecting the occurrence and progress of a crack in a structure with low power consumption and low cost.

It is an example of a structure of a crack detection sensor and a crack measuring apparatus. (A) is a structural example of the sensor element in the crack detection sensor of 1st Embodiment. (B) is a structural example of the sensor element in the crack detection sensor of 2nd Embodiment. (C) is a configuration example of a sensor element in the crack detection sensor of the third embodiment. It is a structural example of the sensor element in the crack detection sensor of 4th Embodiment. It is a structural example of the sensor element in the crack detection sensor of 5th Embodiment. (A) is a configuration example using a plurality of sensor elements. (B) is a configuration example of a sensor element using a plurality of sensor elements. (C) is a configuration example of a sensor element using a plurality of sensor elements. (D) is a configuration example of a sensor element using a plurality of sensor elements. It is a structural example of a sensor element using a plurality of stacked sensor elements. It is a structural example of a crack detection sensor having a plurality of sensor elements. It is an example of the 1st manufacturing method of a sensor element. It is an example of the 2nd manufacturing method of a sensor element. It is a figure which shows the fatigue test body used for the Example. It is a figure which shows the condition which affixed the sensor element on the fatigue test body of FIG. It is the figure which showed the change of fatigue repetition frequency and resistance measured value. It is the example of a measurement which installed the sensor in the welding part of a bridge. It is the measurement example which installed the sensor in the welding part inside a rotary body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crack detection sensor 2 Sensor element 3 Transmission / reception antenna 4 Measurement circuit 5 Communication circuit 7 Activator 8 Transmission / reception antenna 9 Transmission / reception circuit 10 Conductor or resistor 11 Electrical insulation member 12 Terminal for electrical resistance measurement 13 Metal welding part 14 Crack 16 Common Electrical resistance measurement terminal 17 Strip conductor or strip resistor 19 Light shielding plate 20 Conductive paint 21 Surface insulating sheet 22 Metal material 23 Photosensitive resist 24 Photosensitive resist portion altered to solubility 25 Molded measuring circuit 26 Electric circuit length 27 Sensor Element 28 Multiplexer 29 Fatigue Specimen 30 Main Member 31 Gusset 32 Sensor Attaching Portion 33 Welded Portion

Claims (12)

A sensor element whose electrical resistance value increases due to the occurrence and progress of cracks in the cracked detection structure, a measurement circuit for measuring the electrical resistance value of the sensor element, an antenna for capturing driving power from an external activator in a non-contact manner, A crack detection sensor comprising: a communication circuit that transmits the electrical resistance value to the activator in a non-contact manner. The sensor element has one or a plurality of conductors or resistors covered with an electrically insulating member, and two or more electrical resistance measurement terminals connected to the conductors or resistors. The crack detection sensor according to claim 1. The one or more conductors or resistors are linear, and have the electric resistance measurement terminals at both ends, and the measurement circuit determines the electric resistance value of each conductor or resistor. The crack detection sensor according to claim 2, wherein measurement is performed. A plurality of the conductors or resistors, the plurality of conductors or resistors are linear, and have the electrical resistance measurement terminal at one end of each side; The crack detection sensor according to claim 2, wherein the ends are connected to each other and have one common electric resistance measurement terminal. A plurality of the conductors or resistors, the plurality of conductors or resistors being linear, forming a parallel circuit, and having the electrical resistance measurement terminals at both ends of the parallel circuit; The crack detection sensor according to claim 2, wherein: 3. The crack detection sensor according to claim 2, wherein in the sensor element, the conductor or the resistor has a strip shape, and has electrical resistance measurement terminals at two locations of the strip-shaped conductor or resistor. The crack detection sensor according to claim 2, wherein the conductor or the resistor is formed of a conductive paint. The crack detection sensor further includes a memory for storing at least one of an identification code unique to the crack detection sensor and an identification code unique to the sensor element, and the communication circuit includes the electrical resistance value, The crack detection sensor according to claim 1, which has a function of transmitting an identification code. A crack measuring apparatus using the crack detection sensor according to any one of claims 1 to 8, wherein the crack detection sensor and a driving power are sent to the crack detection sensor in a non-contact manner, and the crack is detected. A crack measuring apparatus comprising: an identification code unique to a detection sensor or an identification code unique to the sensor element; and an activator having a function of receiving the electrical resistance value or the electrical resistance value in a non-contact manner. . A crack generation and progress measurement method using the crack measurement device according to claim 9, wherein the crack detection sensor is attached to a structure, and driving power is transmitted to the crack detection sensor from the activator in a non-contact manner. And measuring the occurrence or progress of cracks in the structure by receiving the electrical resistance value of the sensor element or the electrical resistance value and the identification code in a non-contact manner. 8. A method of manufacturing a sensor element in a crack detection sensor according to claim 7, wherein an electrical resistance measurement terminal is mounted on a sheet-like electrical insulation member, and a shielding plate is formed by cutting a predetermined circuit line portion thereon. After mounting, a conductive paint is applied to form a conductor or a resistor on the circuit line portion, and the formed conductor or resistor is further covered with an electrically insulating member. A method for manufacturing a sensor element. 3. A method of manufacturing a sensor element in a crack detection sensor according to claim 2, wherein a metal material is bonded onto a sheet-like electrical insulating member, a photosensitive resist is applied thereon, and then a predetermined circuit line portion is formed. The circuit line portion is transferred onto the photosensitive resist by exposure through the light shielding plate on which the light is drawn, and then the photosensitive resist in the exposed portion or the unexposed portion is transferred to the exposed portion and the unexposed portion. Further, the metal material portion exposed by removing the photosensitive resist is removed by etching to form the conductor or resistor, and an electrical resistance measurement terminal is attached to the conductor or resistor. A method of manufacturing a sensor element for a crack detection sensor, wherein the sensor element is formed by covering the top with an electrically insulating member.

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