JP2013079910A - Fatigue degree detection strain gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fatigue degree detection strain gauge that enables measurement of strains in structural materials and also enables exact prediction in advance of a sign of fatigue fracture locally generated in the structural materials.SOLUTION: In a fatigue degree detection strain gauge 100, measurement of strains and detection of fatigue degree can be conducted by detecting electrical variations of resistance in a resistor constituted such that there are connected a strain detection part 130, a fatigue degree detection part 150 connected in series to the strain detection part, and a conduction part connected in parallel to the fatigue degree detection part. The detection of fatigue degree in the vicinity of a stress concentration portion in a structure is properly conducted in such a constitution that there are included terminal parts 120 connected to one end of the strain detection part and one end of the conduction part respectively in order to detect the electrical variations of resistance in a resistor and the fatigue degree detection part is disposed at an end on the opposite side to a position at which the terminal parts are disposed.

Description

  The present invention relates to a fatigue level detecting strain gauge capable of measuring strain of a structural material and predicting in advance signs of fatigue fracture locally occurring in the structural material.

  For example, a strain gauge for measuring the strain of a structural material is generally known (see Patent Document 1). This strain gauge configuration has a flexible gauge base and two gauges for detecting strain in a predetermined direction. The strain gauge output is calculated from the strain gauge output, Predict signs of fatigue failure.

JP 2009-264856 A

  Strain gauges generally have sufficient mechanical properties equivalent to mechanical structural materials. Therefore, in general structural materials such as beams, columns, bridge piers, steel towers, bridges, etc., whose mechanical strength and fatigue strength are lower than those of mechanical structural materials, a single strain gauge is used at the base, welded portion, and notched portion of a beam that is particularly susceptible to fatigue failure. Is used as a strain sensor for fatigue detection, strain output trends must be collected over a long period of time via a data logger, etc., and the amount of data for accumulating the detected data becomes enormous. And processing is difficult.

  In addition, even when trying to use a single strain gauge for a part where a stress concentration is likely to occur due to a sudden change in the cross-sectional shape of a welded part or a structural material having a relatively low fatigue strength of a mechanical structural material used in an industrial machine, for example. Problems similar to those of the general structural material described above arise.

  On the other hand, the strain gauge described in Patent Document 1 described above detects a strain of a welded portion (hot spot) using a Wheatstone bridge circuit including two strain gauges. However, when trying to output the difference between resistance values of strain gauges having mechanical properties equivalent to that of a mechanical structural material using a Wheatstone bridge circuit, the fatigue level of the structural material must be predicted from the slight difference in output. It is difficult to accurately predict the degree of fatigue.

  In order to avoid such a problem, a fatigue level detecting strain gauge 500 related to the present invention as shown in FIG. 6 has been proposed, which is not yet known at the time of filing the present invention. The configuration of the strain gauge 500 includes a strain detection unit 530, a conduction unit 540 connected in series with the strain detection unit, and a fatigue level detection unit 550 connected in parallel with the conduction unit 540. Breaking due to fatigue increases the resistance of the strain gauge and detects fatigue step by step.

  However, since the fatigue level detection strain gauge 500 has the fatigue level detection unit 550 formed on the terminal side, if the fatigue level detection unit 550 is disposed in a place where stress concentration locally occurs, the terminal units 521 and 522 are provided. (520) is also arranged in the vicinity, and stress is also generated, for example, at the solder joint portion of the terminal portion 520 with the stress concentration of the structural material. It is not preferable from the viewpoint of keeping. On the other hand, when the fatigue degree detection strain gauge 500 is arranged in a state where the terminal part 520 is separated from the local stress concentration part so that the terminal part 520 is not affected by the stress concentration, the fatigue degree detection part 550 is also a stress concentration part. Therefore, it is not preferable from the viewpoint of detecting the degree of fatigue quickly and accurately.

  An object of the present invention is to provide a fatigue degree detection strain gauge capable of measuring strain of a structural material and predicting a fatigue fracture sign locally generated in the structural material in advance and accurately.

In order to solve the above-described problem, a fatigue degree detection strain gauge according to claim 1 of the present invention is provided.
A strain detector;
A fatigue detection unit connected in series with the strain detection unit;
Fatigue level detection capable of strain measurement and fatigue level detection by detecting electrical changes in the resistance value of a resistor configured by connecting a conductive portion connected in parallel with the fatigue level detection unit A strain gauge,
In order to detect an electrical change in the resistance value of the resistor, comprising a terminal portion connected respectively at one end of the strain detection portion and one end of the conduction portion,
It is characterized in that the fatigue degree detection part is arranged at the end opposite to the position where the terminal part is arranged to appropriately detect the fatigue degree near the stress concentration part of the structure.

  With the fatigue level detection strain gauge according to claim 1 having such a configuration, the fatigue level detection unit can be disposed at a place where stress concentration locally occurs in the structural material, and the fatigue level can be quickly and accurately determined. Detection is possible. In addition, since the fatigue level detection part is not formed on the terminal part side, even if the fatigue level detection part is arranged in a place where stress concentration occurs locally, for example, stress is applied to the solder joint of the terminal part due to the stress concentration. This does not adversely affect the fatigue detection strain gauge itself.

  Further, in order to predict the signs of fatigue failure of the structural material, it is not necessary to collect strain output trends over a long period of time, and the management and processing of an enormous amount of data are not bothered. Further, when the fatigue detection section breaks due to fatigue, the resistance of the strain gauge increases, and the output of the strain gauge changes stepwise, making it easier to predict fatigue failure of the structural material.

Moreover, the fatigue degree detection strain gauge according to claim 2 of the present invention is the fatigue degree detection strain gauge according to claim 1,
The strain detection part and the conduction part are arranged on the arrangement position side of the terminal part,
It is a fatigue degree detection strain gauge in which the fatigue degree detection unit is disposed so as to protrude from the strain detection unit and the conduction unit.

  The fatigue level detection strain gauge according to claim 2 has such a configuration, so that the fatigue level detection unit can be easily arranged in a place where local stress concentration occurs, and local stress concentration accompanying fatigue of the structural material. As a result, the fatigue level detection part is easily broken. As a result, fatigue failure of the structural material can be predicted more quickly.

  On the other hand, the conduction part and strain detection part can be installed in a place away from the place where stress concentration occurs, and the conduction part and strain detection part are disconnected due to the tensile and compressive stress of the structural material to detect the degree of fatigue. The function as a strain gauge is not impaired.

  In addition, by arranging the fatigue degree detection part so as to protrude from the strain detection part and the conduction part, the terminal part can be further separated from the fatigue degree detection part, so that the local stress concentration part of the structural material can be separated. The terminal portions can be arranged further apart. Thereby, the solder joint portion of the terminal portion can be prevented from being adversely affected by the stress concentration portion of the structural material.

Moreover, the fatigue degree detection strain gauge according to claim 3 of the present invention is the fatigue degree detection strain gauge according to claim 1 or 2,
A plurality of the fatigue level detection units are configured by connecting the strands and the adjacent strands with a fatigue level detection folded tab,
A fatigue level detection strain gauge having a plurality of fatigue level detection folded tabs having different end tab ratios, where the ratio of the length of the fatigue level detection folded tabs to the line width of the plurality of strands is defined as an end tab ratio. It is characterized by that.

  When the fatigue level detection strain gauge according to claim 3 has such a configuration, the fatigue level detection unit breaks in stages according to the level of fatigue of the structural material. Therefore, the fatigue level of the structural material can be detected in stages.

Moreover, the fatigue degree detection strain gauge according to claim 4 of the present invention is the fatigue degree detection strain gauge according to any one of claims 1 to 3,
The fatigue level detecting strain gauge is characterized by being a fatigue level detecting strain gauge provided with a notch in the vicinity of the inner part of the folded tab of the fatigue level detecting folded tab.

  The fatigue level detection strain gauge according to claim 4 has such a configuration, so that the fatigue level of the structural material is the same as that of a fatigue level detection strain gauge not having such a configuration. The detection part is more easily broken. Therefore, when the same degree of fatigue level detection is performed, the length of the fatigue level detection folded tab can be shortened compared to a configuration in which the folded tab does not have such a cut. As a result, since the fatigue level detection unit can be arranged closest to the local stress concentration portion of the structural material, it is possible to predict fatigue fracture of the structural material quickly and accurately in advance.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to measure the distortion | strain of a structural material, the fatigue degree detection strain gauge which can predict the sign of the fatigue fracture which arises locally in a structural material in advance and exactly can be provided.

It is a top view which shows the fatigue degree detection strain gauge which concerns on this embodiment. It is a perspective view showing roughly the state where the fatigue degree detection strain gauge concerning this embodiment was attached to a structural material. It is a top view which shows the 1st modification of the fatigue degree detection strain gauge which concerns on this embodiment. It is a top view which shows the 2nd modification of the fatigue degree detection strain gauge which concerns on this embodiment. FIG. 5A is an enlarged plan view showing a fatigue level detection unit of a second modification of the fatigue level detection strain gauge according to this embodiment, and fatigue level detection of the fatigue level detection strain gauge according to this embodiment. It is a top view (Drawing 5 (b)) expanding and showing an example of correction of a portion. It is a top view which shows the fatigue degree detection strain gauge relevant to this invention.

  The fatigue level detection strain gauge according to the present embodiment includes a strain detection unit, a fatigue level detection unit connected in series with the strain detection unit, and a conduction unit connected in parallel with the fatigue level detection unit and in series with the strain detection unit. By detecting an electrical change in the resistance value of the resistor configured as described above, strain measurement and fatigue level detection are performed. And in order to detect the electrical change of the resistance value of a resistor, the terminal part connected by the end of a distortion | strain detection part and the end of a conduction | electrical_connection part is provided, respectively. In addition, a fatigue level detection unit is arranged at the end opposite to the position where the terminal unit is positioned, so that the fatigue level in the vicinity of the stress concentration part of the structure is appropriately detected.

  Hereinafter, a fatigue level detection strain gauge according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a fatigue level detecting strain gauge according to the present embodiment. FIG. 2 is a perspective view schematically showing a state in which the fatigue detection strain gauge according to the present embodiment is attached to a structural material. In the following description, the vertical direction of the film-like member in FIG. 1 is the longitudinal direction, and the horizontal direction is the width direction. Moreover, let the upper side of the film-like member in FIG. 1 be a front end side, and let the lower side be a base end side.

  The fatigue level detection strain gauge 100 according to the present embodiment is used to detect the fatigue level of general structural materials such as beams, columns, piers, steel towers, bridges, etc. of buildings, and is a flexible insulator. A film-like member 110 made of a resin material and an electric resistor made of a metal foil patterned on the film-like member 110 are used. The electrical resistor includes terminal portions 121 and 122 (120), a strain detection unit 130, a conduction unit 140, and a fatigue level detection unit 150.

  The film-like member 110 is made of a resin member, has flexibility, and has an elongated rectangular shape. In addition, as shown in FIG. 2, the fatigue detection unit 150 disposed on the distal end side of the film-like member 110 is closest to the stress concentration portion of the structural material, and the terminal unit 120 disposed on the proximal end side is the structural material. The film-like member 110 is pasted with an adhesive or the like at the position farthest from the stress concentration portion.

  The terminal portion 120 is formed on the base end side of the film-like member 110 and in the vicinity of both ends in the width direction. An electric wire (not shown) is soldered to the terminal portion 120, and a change in the resistance value of the electric resistor composed of the strain detection portion 130, the conduction portion 140, and the fatigue level detection portion 150 is output to the outside, and calculation control (not shown) is performed. The strain and fatigue level of the structural material to which the fatigue level detection strain gauge 100 is attached are detected by means.

  The strain detection unit 130 is formed on the one side in the width direction of the film-like member 110 (left side in FIG. 1) and in the region extending from the vicinity of the front end portion of the film-like member 110 to the vicinity of the central portion in the longitudinal direction of the film-like member 110. Has been.

  In the present embodiment, the strain detection unit 130 is a metal foil having a thin line width and is folded back in the same direction many times on the end side, and the extension portions of the constant length are slightly spaced. They are so-called zigzag folded shapes (hereinafter simply referred to as “zigzag folded” shapes) arranged in parallel with each other. In addition, each extension part of the distortion | strain detection part 130 is extended in the longitudinal direction of the film-like member.

  In addition, one end of the strain detection unit 130 is connected to one terminal unit 121, and the other end is connected to the conduction unit 140 and the fatigue level detection unit 150.

  More specifically, the strain detection unit 130 includes a plurality of strands 131 (the above-described extending portion) and a folded tab 132 (the above-described folded portion). The resistance value of the detection unit 130 is increased, and the resistance value of the entire electrical resistor is also increased. In addition, the shape of the inner part of the folding tab 132 at the portion where the folding tab 132 of the strain detecting unit 130 and the strand (gauge sensing unit) 131 are connected has a curved shape in which the curvature gradually and gradually changes. The shape is less likely to cause disconnection due to fatigue.

  The fatigue degree detection unit 150 is formed on the other side in the width direction of the film-like member 110 (on the right side in FIG. 1), from the vicinity of the tip end portion of the film-like member 110 to the region of the central portion in the longitudinal direction. In addition, each extension part which makes the strand 151 of the fatigue degree detection part 150 is extended in the longitudinal direction of the film-like member 110.

  In this embodiment, the fatigue level detection unit 150 is also made of a metal foil having a thin line width, and includes a plurality of strands 151 and folded tabs 152 (152a, 152b), and the strands 151 extend in the longitudinal direction of the film-like member 110. The formed spelled shape is folded. The strands 151a and 151b at both ends of the fatigue detection unit 150 further extend to the proximal end side of the film-like member 110, and one strand 151a is connected to the strand 131 of the strain detection unit 130 and one end of the conduction unit 140. Conducted. Further, the other strand 151 b of the fatigue degree detection unit 150 is connected to the terminal unit 122.

  Note that the length of the folded tab 152a formed on the distal end side of the film-like member is longer than the length of the folded tab 152b formed on the proximal end side of the film-like member.

  In the present embodiment, the fatigue level detecting strain gauge 100 is attached to the structural material so that the folded tab 152a is positioned at or near the stress concentration portion where the structural material is locally generated. When the strand 151 and the folded tab 152a are broken, no current flows through the fatigue detection unit 150, and only current flows through the strain detection unit 130 and the conduction unit 140. As a result, the resistance value of the entire electrical resistor increases stepwise, thereby enabling local fatigue failure of the structural material to be predicted quickly and accurately. If the length dimension L in the longitudinal direction of the folded tab 152a (see FIG. 5A) and the length dimension W in the width direction of the strand 151 (see FIG. 5A) are set, the dimension L is long and the dimension W is long. The shorter it is, the easier it is for the fatigue level detector 150 to break.

  The conduction part 140 is formed on one side in the width direction of the film-like member 110 (the right side in FIG. 1) similarly to the fatigue degree detection part 150, and more than the fatigue degree detection part 150 in the longitudinal direction of the film-like member 110. It is formed so as to be in parallel with the fatigue detection unit 150 in the proximal end region.

  The conductive portion 140 also has a zigzag shape in which the length of each extending portion between the folded portions is short, and one end portion (the left end portion in FIG. 1) of the folded portion is the strain detecting portion 130 and the fatigue degree detecting portion 150. One extension portion 151 a is connected, and the other end portion (the right end portion in the width direction in FIG. 1) is connected to the other extension portion 151 b of the fatigue degree detection unit 150.

  More specifically, the conduction part 140 is composed of a plurality of strands 141 and folded tabs 142. Even if the conduction part 140 is distorted, the resistance value of the conduction part 140 does not change, and the electrical resistor as a whole. The resistance value is also not changed. In addition, the shape of the inner portion of the folded tab 142 where the folded tab 142 and the strand 141 of the conductive portion 140 are connected has a curved shape in which the curvature gradually changes continuously, and disconnection due to fatigue is unlikely to occur. It has a shape. As a result, when the fatigue level detection unit 150 breaks, no current flows through the fatigue level detection unit 150 and current flows only through the conduction unit 140, so that the resistance value of the entire electrical resistor increases. It has become.

  The fatigue level detection strain gauge 100 according to the present embodiment is an electrical resistance type fatigue level detection strain gauge that can detect the fatigue level by using the fatigue level detection unit 150. It is not only specialized in degree detection, but when strain occurs in the strain detector 130, the resistance value of the strain detector 130 changes, and the strain of the structural material can be detected from the changed value. .

  Then, the specific usage method of the fatigue degree detection strain gauge 100 mentioned above is demonstrated. FIG. 2 is a perspective view schematically showing a state in which the fatigue level detection strain gauge 100 according to the present embodiment is attached to a structural material. In FIG. 2, two fatigue degree detection strain gauges 100 </ b> A and B are attached to a connecting portion between a column 11 and a beam 12 as a general structural material. The local stress concentration portion of the structural material is a connection portion between the column 11 and the beam 12.

  More specifically, one fatigue level detection strain gauge 100A is attached to the side surface of the column 11 in the vicinity of the connecting portion between the column 11 and the beam 12, and the other fatigue level detection strain gauge 100B is connected to the column 11 and the beam 11. It is attached to the lower surface of the beam 12 in the vicinity of the connecting portion of the beam 12.

  In the fatigue level detection strain gauge 100A attached to the column 11, the distal end side, that is, the formation side of the fatigue level detection portion 150 is located in the immediate vicinity of the connection portion between the column 11 and the beam 12, and the proximal end side, that is, the formation side of the terminal portion 120 is located. It is affixed to the column 11 so as to be located farthest from the connecting portion between the column 11 and the beam 12. In addition, the fatigue level detection strain gauge 100B attached to the beam 12 is also located at the distal end side, that is, the formation side of the fatigue level detection unit 150, in the immediate vicinity of the connection portion between the column 11 and the beam 12, and the proximal end side, that is, the terminal portion formation side. It is affixed to the beam so that it is located farthest from the connection between the column and the beam.

  Since the two fatigue degree detection strain gauges 100A and 100B are attached to the column 11 and the beam 12 in this way, when a bending load or a tensile load is applied to the column 11 or the beam 12, the fatigue of the column 11 or the beam 12 is detected. When the stress concentration of the tensile stress is locally generated on the side to which the degree detection strain gauges 100A and B are attached, this is detected by the fatigue degree detection unit 150 of each fatigue degree detection strain gauge 100A and B, and the column 11 and the beam This can be useful for predicting fatigue fracture at the twelve connecting portions.

  Since the fatigue level detection strain gauge according to the present embodiment described above has both the fatigue level detection unit 150 and the strain detection unit 130, the following usage method unique to the present invention is possible. Specifically, for example, when the fatigue level detection strain gauge 100 according to the present embodiment is provided in a general structural material of a pier that passes a lot of vehicles, for a while from the completion of the pier, the strain detection unit 130 detects the structural material. The trend of the degree of strain can be collected, and the tendency of the degree of strain accompanying the vehicle traffic of the structural material constituting the pier can be detected.

  In addition, when a fatigue failure of a structural material is predicted due to the disconnection of the fatigue level detection unit 150, by collecting from the strain detection unit 130 for a while from the trend of the strain level of the structural material immediately after that, what kind of phenomenon It is possible to grasp whether the fatigue failure of the structural material is approaching. On the other hand, even if the fatigue detection unit 150 does not break, for example, when the amount of traffic of a vehicle passing through a pier increases rapidly, the structure from the strain detection unit 130 for a while immediately after the increase of the traffic amount. By collecting the trend of the degree of strain of the material, it is possible to analyze the influence of the increase in traffic on the structural material.

  Such a method of use is not limited to the case where a general structural material is used for a pier, and may be applied to a general structural material that forms the framework of a multi-story building, for example. Thereby, for a while immediately after the building is completed, the strain detection unit 130 detects the trend of the degree of distortion of the structural material, whereby the change in the degree of distortion of the structural material after the building is completed can be analyzed.

  In addition, when a fatigue failure of a structural material is predicted due to the disconnection of the fatigue level detection unit 150, the trend of the degree of strain of the structural material is collected from the strain detection unit for a while immediately after that, so that what kind of phenomenon It is possible to grasp whether the fatigue fracture of the material is approaching. On the other hand, even if the fatigue detection unit 150 does not break, for example, when a heavy object such as an industrial machine is installed on the upper floor of a building, for example, the strain of the structural material for a while immediately after the installation of the heavy object. By collecting the trend of the degree from the strain detection unit 130, it is possible to analyze the influence of the installation of heavy objects on the structural material.

  Then, the 1st modification of embodiment mentioned above is demonstrated. In addition, about the structure equivalent to embodiment mentioned above, a corresponding code | symbol is attached | subjected and detailed description is abbreviate | omitted. FIG. 3 is a plan view showing a first modification of the fatigue level detection strain gauge according to the present embodiment.

  The fatigue degree detection strain gauge 200 according to the first modification has the same configuration as that of the above-described embodiment, that is, the strain detection unit 230, the fatigue level detection unit 250 connected in series with the strain detection unit 230, and the fatigue level detection unit. By detecting a change in the resistance value of the electric resistor configured by connecting the conduction unit 240 connected in parallel with the 250 and the strain detection unit 230, strain measurement and fatigue level detection can be performed. ing. And in order to detect the change of the resistance value of an electrical resistor, the terminal part 221 and 222 (220) respectively connected by the end of the distortion | strain detector 230 and the end of the conduction | electrical_connection part 240 are provided. In addition, a fatigue level detection unit 250 is disposed at the end opposite to the position where the terminal unit 220 is positioned to appropriately detect the fatigue level near the local stress concentration portion of the structure. .

  The difference in configuration between the fatigue level detection strain gauge 200 according to the first modification and the fatigue level detection strain gauge 100 according to the above-described embodiment is that the fatigue level detection strain gauge 200 according to the first modification is configured to detect strain. The portion 230 and the conducting portion 240 are arranged in the vicinity of the terminal portion 220, and the fatigue degree detecting portion 250 is arranged at a position protruding to the tip side of the film-like member 210 with respect to the strain detecting portion 230 and the conducting portion 240. . That is, the fatigue detection unit 250, the conduction unit 240, the strain detection unit 230, and the terminal unit 220 are arranged side by side on the film member in this order from the longitudinal tip side to the base side of the film member 210. In terms of circuit, the conduction unit 240 and the strain detection unit 230 are connected in parallel.

  Since the fatigue level detection strain gauge 200 according to the first modification has such a configuration, the front end side of the film-like member 210 on which the fatigue level detection strain gauge 200 is formed is formed between the column 11 and the beam 12 illustrated in FIG. When it is attached to the connecting portion and located at the local stress concentration portion and the proximal end side is positioned so as to be located farthest from the connecting portion of the column 11 or the beam 12, the fatigue degree detection portion 250 is locally stress concentrated. It can be arranged at the position where this occurs or as close as possible. As a result, the fatigue level detector 250 can be easily broken against stress concentration, and the fatigue failure of the structural material can be predicted more quickly and accurately.

  On the other hand, the conduction part 240 and the strain detection part 230 can be installed at a place away from the place where the stress concentration occurs, and the strain detection part 230 and the conduction part 240 are affected by the local stress concentration part of the structural material. It is possible to collect data on only the strain generated in the structural material. Moreover, since the terminal part 220 can be further separated from the fatigue degree detection part 250, it can be arranged further away from the stress concentration part of the structural material. Accordingly, for example, the solder joint portion of the terminal portion 220 can be prevented from being adversely affected by the stress concentration portion of the structural material.

  Then, the 2nd modification of embodiment mentioned above is demonstrated. In addition, about the structure equivalent to embodiment mentioned above, a corresponding code | symbol is attached | subjected and detailed description is abbreviate | omitted. FIG. 4 is a plan view showing a second modification of the fatigue level detection strain gauge 300 according to the present embodiment.

  The fatigue level detection strain gauge 300 according to the second modification has the same configuration as that of the above-described embodiment, that is, the strain detection unit 330, the fatigue level detection unit 350 connected in series with the strain detection unit 330, and the fatigue level detection unit. The strain measurement and the fatigue level detection are performed by detecting a change in the resistance value of the electric resistor formed by connecting the conduction unit 340 connected in parallel with the 350 and the strain detection unit 330 in series. . And in order to detect the change of the resistance value of an electrical resistor, the terminal parts 321 and 322 (320) respectively connected by the end of the distortion | strain detector 330 and the end of the conduction | electrical_connection part 340 are provided. In addition, a fatigue level detection unit 350 is disposed at the end opposite to the position where the terminal unit 320 is disposed, so that the fatigue level in the vicinity of the stress concentration portion of the structure is detected quickly and accurately.

  The difference in configuration between the fatigue detection strain gauge 300 according to the second modification and the fatigue detection strain gauge 100 according to the above-described embodiment is that the fatigue detection of the fatigue detection strain gauge 300 according to the second modification is detected. When the ratio of the length L of the folded tab 352 for fatigue detection to the line width W of the plurality of strands 351 (see FIG. 5A) (see FIG. 5A) is the end tab ratio, This is in that it has a plurality of folded back tabs 352a, b, c, d for detecting the degree of fatigue with different end tab ratios.

  More specifically, in FIG. 4, the length of the folded tab 352 a for detecting the degree of fatigue at the center in the width direction of the film-like member 310 is the longest (that is, the end tab ratio is the largest), and is generated in the local stress concentration portion. Disconnection is caused by slight fatigue. Thereafter, the length of the folded tabs 352b, c, d for detecting the degree of fatigue gradually decreases toward the end in the width direction of the film-like member 310, and fatigue occurs when the folded tab 352 and the strand 351 are disconnected. The degree is gradually increased in the order of the folded tabs 352b, c, d.

  Further, the adjacent strands 351a and 351b extending from the adjacent folded tabs 352a and 352b are electrically connected to the folded tab 342a of the conducting portion 340, and the adjacent strands 351b ′ extending from the adjacent folded tabs 352b and 352c are adjacent to each other. , 351c are electrically connected to the folded tab 342b of the conducting portion 340, and the adjacent strands 351c ′, 351d extending from the adjacent folded tabs 352c, 352d are electrically connected to the folded tab 342c of the conducting portion 340.

  Since the fatigue level detection strain gauge 300 according to the second modification has such a configuration, the fatigue level detection unit 350 is broken in stages due to the fatigue level of the structural material, and the resistance value of the electrical resistor is also in accordance with this. Rises in stages. Specifically, when the fatigue level of the structural material increases to a certain level, the folded tab 352a and the strand 351 are disconnected, branch from the strain detecting unit 330, and the conductive portion via the folded tab 352a and the strand 351a. Current stops flowing in the circuit connected to 340, and the resistance value of the electrical resistor increases by a certain amount (one step).

  Next, when the fatigue level of the structural material further increases to a certain level, the folded tab 352b and the strand 351 are disconnected, and in addition to the circuit described above, branch from the strain detector 330 and the folded tab 352b and the strand 351b ′. As a result, the current of the circuit connected to the conduction portion 340 does not flow via the, and the resistance value of the electrical resistor is increased by a certain amount (further step). In this way, as the fatigue level of the structural material increases, the folded tab 352c and the strand 351 are disconnected in sequence, and the folded tab 352d and the strand 351 are disconnected in sequence, and the resistance value of the electrical resistor is gradually increased accordingly. To rise. And by detecting the step change of this resistor, the fatigue level of the structural material can be detected step by step.

  Then, the correction example of the fatigue degree detection part of the fatigue degree detection strain gauge which concerns on embodiment mentioned above is demonstrated. FIG. 5B is an enlarged plan view showing a fatigue level detection unit 150 'of a modification example of the fatigue level detection strain gauge 100 according to the present embodiment. In this modified example, a notch is provided in the vicinity of the inner part of the folded tab 152 for detecting the degree of fatigue.

  More specifically, it is a connecting portion between the outer edge 152m of the folded tab 152a ′ and the outer edge 151m of the continuous strand 151, and a connecting portion between the inner edge 151n of each strand 151 and the inner edge 152n of the folded tab 152a ′. A triangular notch 153 is formed in the portion closest to 152p.

  Since the modification example of the fatigue level detection unit has such a configuration, the fatigue level detection unit 150 ′ is easily broken at the cut portion 153. Therefore, even if the length of the folded back tab 152a ′ for detecting the degree of fatigue is shortened as shown in FIG. Even if the degree of fatigue is small, it is easy to disconnect between the folded tab 152a ′ and the strand 151. As a result, the fatigue level detection unit 150 ′ can be disposed closest to the local stress concentration portion of the structural material, and fatigue fracture of the structural material can be predicted quickly and accurately. This modified example can also be applied to the first and second modified examples described above.

  The arrangement pattern of the metal foil according to the embodiment and each modification described above is merely an example, and it goes without saying that various modifications can be applied without departing from the present invention.

  Further, the film-like member of the fatigue level detection strain gauge may not necessarily be made of resin and has flexibility as long as the strain detection unit and the fatigue level detection unit formed thereon play a role. It does not have to be.

  In addition, as an application example of the fatigue detection strain gauge according to the above-described embodiment and its modifications, a general structural material composed of columns and beams has been introduced, but the application target is limited to such a thing. Instead, for example, the present invention can be applied to a portion where stress concentration is likely to occur locally, such as a welded portion of a general structural material or a portion where the shape changes abruptly (the shape factor changes abruptly). Similarly, the above-described embodiment and its modifications are included in parts where stress concentration is likely to occur locally, such as a welded part or a part whose shape changes suddenly even if it is a mechanical structural material having the same mechanical properties as a strain gauge. The fatigue degree detection strain gauge according to the present invention can be applied.

100 (100A, 100B) Fatigue degree detection strain gauge 110 Film-like member 121, 122 (120) Terminal part 130 Strain detection part 131 Strand 132 Folding tab 140 Conducting part 150, 150 'Fatigue degree detection part 151 (151a, 151b) Strand 152 (152a, 152a ′, 152b) Folding tab 153 Notch portion 200 Fatigue degree detection strain gauge 210 Film-like members 221 and 222 (220) Terminal portion 230 Strain detection portion 240 Conduction portion 250 Fatigue degree detection portion 300 Fatigue degree detection strain gauge 310 Film-like members 321 and 322 (320) Terminal portion 330 Strain detector 340 Conductor 350 Fatigue degree detector 351 (351a, 351b, 351b ′, 351c ′) Strand 352 (352a, 352b, 352c, 352d) Folded tab

Claims (4)

A strain detector;
A fatigue detection unit connected in series with the strain detection unit;
Fatigue level detection capable of strain measurement and fatigue level detection by detecting electrical changes in the resistance value of a resistor configured by connecting a conductive portion connected in parallel with the fatigue level detection unit A strain gauge,
In order to detect an electrical change in the resistance value of the resistor, a terminal portion connected to one end of the strain detection portion and one end of the conduction portion, respectively, a position where the terminal portion is disposed; A fatigue level detecting strain gauge, wherein the fatigue level detecting unit is disposed on the opposite end to appropriately detect the fatigue level in the vicinity of the stress concentration portion of the structure. The strain detection unit and the conduction unit are arranged on the arrangement position side of the terminal unit, and the fatigue detection unit is arranged to protrude with respect to the strain detection unit and the conduction unit. Fatigue level detection strain gauge. A plurality of the fatigue level detection units are configured by connecting the strands and the adjacent strands with a fatigue level detection folded tab,
The fatigue strength detection folded tab has a plurality of end tab ratios different from each other when the ratio of the length of the fatigue level detection folded tab to the line width of the plurality of strands is defined as an end tab ratio. The fatigue degree detection strain gauge according to 1 or 2. The fatigue degree detecting strain gauge according to any one of claims 1 to 3, wherein a notch is provided in the vicinity of the inner part of the folded back of the folded tab for detecting the fatigue degree.

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