JP6640932B2 - Fatigue sensor, fatigue measurement method, and method of manufacturing fatigue sensor - Google Patents

Description

  The present invention relates to a fatigue sensor, a fatigue measurement method, and a method for manufacturing a fatigue sensor, and more particularly, to a fatigue sensor for a structure.

  In objects (structures, structures) formed of materials such as metals, resins, glasses, ceramics, and concrete, mechanical strength is reduced (fatigue) due to repeated or continuous application of stress. Ultimately, fracture (fatigue fracture, fracture, permanent deformation) may occur. For example, in a structure that repeatedly expands and contracts due to heat, the structure may be destroyed by stress (thermal stress) due to restriction of free deformation (expansion and contraction).

The fatigue characteristic of a structure is often represented by an SN curve (stress-number curve, Wehrer curve). The SN curve shows the magnitude (repetitive stress value) of the stress (repetitive stress) repeatedly applied at a constant magnitude (amplitude, etc.) in the fatigue test of the structure, and the magnitude of the stress until the structure breaks. It is a curve which showed the relationship with the number of load repetitions (number of break repetitions). Normally, in the graph of the SN curve, the repetitive stress value is represented by the vertical axis (normal scale or logarithmic scale), and the number of repetition of fracture is represented by the horizontal axis (logarithmic scale). In some materials (such as low carbon steel), in certain repetition rate (e.g. 10 ⁶ to about 10 ⁷⁾ or greater, S-N curve becomes horizontal. That is, there is an upper limit (fatigue limit) of a repeated stress value at which a repeated stress value equal to or less than a certain value does not cause fracture even if the load is repeated many times.

  Therefore, when designing a structure, materials and structures may be selected so that the repetitive stress value expected to occur in the structure is not more than the fatigue limit in consideration of the margin (safety factor). is there. When a material does not have a definite fatigue limit, a material, a structure, or the like may be selected using a cyclic stress value corresponding to a practically sufficient number of fracture cycles as a guide corresponding to the fatigue limit.

  The fatigue characteristics of a structure are affected by stress such as average stress applied to the structure and residual stress in the structure. Generally, tensile stress reduces the strength of a structure (the number of fracture cycles). Compressive stress often increases the strength of a structure.

  For example, Patent Document 1 discloses a general method of manufacturing a floor panel that gives residual stress to a floor panel using a wooden plywood. In the floor panel of Patent Document 1, a plywood main surface material is fitted in a plywood housing in a state of being curved in an arc shape. As a result of the above configuration, the floor panel of Patent Document 1 is hardly deformed.

  Further, for example, Patent Document 2 discloses a general method of manufacturing a (disk brake) pad in which a residual stress is applied to a friction material using a thermoforming mold. In the manufacturing method of Patent Document 2, the back plate of the pad and the friction material are formed and adhered by heating and pressing in a thermoforming mold. Here, the insert of the thermoforming mold has a concave portion. The recess gives the back plate warpage due to the molding pressure of the friction material. As a result of the above configuration, in the manufacturing method of Patent Literature 2, the back plate causes the friction material to generate internal stress (residual stress) for returning the warp.

  When determining the cyclic stress in the design of a structure, the cyclic stress in the structure is often not measured. Therefore, if the cyclic stress generated in the real environment exceeds the cyclic stress predicted in the design, the structure may be broken in the real environment.

  Further, when determining the fatigue characteristics of a material or a structure in designing a structure, the fatigue characteristics of the material or the structure are often not actually measured. Therefore, if a defect is present in the material or a notch is formed in the structure due to an external force or the like, the fatigue limit of the structure may decrease. As a result, the structure may be destroyed even at the cyclic stress predicted in the design.

  In the inspection of a structure, there is a problem similar to the problem in the design. In order to avoid the fatigue fracture of the structure, a periodic structure inspection (visual inspection, hammering inspection, etc.) may be performed. However, if the degree of fatigue of the structure (eg, the degree of fatigue damage according to the Miner's rule) is not measured, it may not be known whether the inspection interval (inspection span) is too large or too small.

  Therefore, a fatigue sensor for measuring the degree of fatigue of a structure is required.

  Patent Document 3 discloses an example of a technique relating to a fatigue sensor. The fatigue sensor disclosed in Patent Literature 3 has a foil-like substrate and a foil in which a slit extending from one side in the width direction perpendicular to the longitudinal direction toward the other side in the width direction is formed in a central portion between both ends in the longitudinal direction. And broken fragments. The broken pieces are joined on one surface of the substrate by welding intersections formed between both ends in the longitudinal direction of the second electroformed portion and one surface of the substrate. The fatigue sensor is fixed to the member to be detected on the other surface of the substrate. A crack propagation length detecting member for electrically detecting a crack propagation length is formed in a crack propagation region extending from the tip of the slit to the other side in the width direction at an intermediate portion of the fragment. The thickness T3 of the intermediate portion is smaller than the thickness T4 of the second electroformed portion. The crack propagation detecting member has a plurality of electric resistance lines extending along a crack propagation direction, that is, a longitudinal direction perpendicular to the lateral direction. The electric resistance wires are arranged in parallel at equal intervals in the width direction, both ends are electrically connected in parallel, and are bonded to the crack propagation region with an adhesive or the like. When a crack propagates from the tip of the slit, the electric resistance wire is sequentially broken, and a change with time in the resistance value due to such a break is measured by a measuring device. As a result of the above configuration, the measuring device of Patent Document 3 detects the degree of fatigue damage of the detected member according to the measurement result of the resistance value of the fatigue sensor.

JP 2005-180145 A JP 2002-295555 A JP 2005-164247 A

  In order to detect the degree of fatigue damage of the detected member, the measuring device of Patent Document 3 needs to know the relationship between the resistance value of the fatigue sensor and the degree of fatigue damage of the detected member. This relationship is determined, for example, by measuring the resistance value of the fatigue sensor in a fatigue test on a structure (duplicate) having the same specifications as the detected member in which a fatigue sensor (duplicate) having the same specifications as the fatigue sensor is installed. Can be estimated.

  In the above-described fatigue test, generally, the degree of fatigue damage (fatigue characteristic) of the fatigue sensor with respect to a predetermined cyclic stress does not match the degree of fatigue damage (fatigue characteristic) of the structure with respect to the same predetermined cyclic stress. When the fatigue characteristic of the fatigue sensor is larger than the fatigue characteristic of the structure, if the degree of fatigue damage of the fatigue sensor becomes 1 (if the fatigue detecting member of the fatigue sensor breaks), the degree of fatigue damage of the structure thereafter. Cannot be calculated. When the fatigue characteristic of the fatigue sensor is smaller than the fatigue characteristic of the structure, the fatigue damage degree of the structure can be calculated based on the fatigue damage degree of the fatigue sensor. However, if the fatigue characteristics of the fatigue sensor are too small relative to the fatigue characteristics of the structure, the accuracy of calculating the degree of fatigue damage of the structure based on the degree of fatigue damage of the fatigue sensor decreases. That is, the sensitivity (fatigue characteristic) of the fatigue sensor must be adapted to the fatigue characteristic of the structure. Therefore, it is desirable that a fatigue sensor having appropriate sensitivity can be easily manufactured according to the fatigue characteristics of a structure.

  However, the sensitivity of the fatigue sensor of Patent Document 3 is determined mainly based on the ratio between the thickness T3 of the intermediate portion and the thickness T4 of the second electroformed portion. Then, the intermediate portion and the second electroformed portion are formed by an electroforming method. This manufacturing method does not consider providing a variation in the sensitivity of the fatigue sensor after manufacturing the fatigue detection member. Therefore, the fatigue sensor disclosed in Patent Document 3 has a problem that it is difficult to set a desired sensitivity for the fatigue sensor.

  The manufacturing methods of Patent Documents 1 and 2 do not relate to a method of manufacturing a fatigue sensor.

  The present invention has been made in view of the above problems, and has as its main object to provide a fatigue sensor that can easily set a desired sensitivity.

  In one embodiment of the present invention, the fatigue sensor includes a fatigue detection unit that breaks when repeatedly applied stress is applied to the structure, a tensile force application unit that applies a tensile force to the fatigue detection unit, It is provided with a tensile force adjusting section for adjusting the tensile force applied to the detecting section to a desired tensile force value, and a break detecting section for detecting a break in the fatigue detecting section.

  In one embodiment of the present invention, the fatigue measurement method, a fatigue detection unit that is broken by repeatedly applying a stress in a state where it is installed on the structure, a tensile force application unit that applies a tensile force to the fatigue detection unit, A method for measuring the fatigue of a structure using a fatigue sensor including a tensile force adjusting unit that adjusts a tensile force applied to a fatigue detecting unit to a desired tensile force value and a fracture detecting unit that detects a fracture in the fatigue detecting unit A plurality of fatigue sensors having different internal stress values in the fatigue detection unit are installed on the structure, and the progress of the fatigue in the structure is measured based on the presence or absence of breakage detected by each fatigue sensor.

  In one aspect of the present invention, a method for manufacturing a fatigue sensor includes a fatigue detection unit that is broken by repeated stress applied in a state where the fatigue sensor is installed on a structure, and a tension application unit that applies a tensile force to the fatigue detection unit. A method of manufacturing a fatigue sensor including a tensile force adjusting unit that adjusts a tensile force applied to a fatigue detecting unit to a desired tensile force value and a fracture detecting unit that detects a fracture in the fatigue detecting unit, An internal stress adjusting step of adjusting an internal stress in the fatigue detecting section to a predetermined internal stress value; an assembling step of assembling a fatigue sensor from the fatigue detecting section, a tensile force applying section, a tensile force adjusting section, and a fracture detecting section; Adjusting the adjusting unit to adjust the tensile force applied to the fatigue detecting unit to a desired tensile force value.

  According to the present invention, there is an effect that a fatigue sensor that can easily set a desired sensitivity can be provided.

It is a three-view figure showing an example of the composition of the fatigue sensor in a 1st embodiment of the present invention. FIG. 4 is a two-side view showing a modification of the fatigue sensor according to the first embodiment of the present invention. 4 is a flowchart illustrating a method for manufacturing a fatigue sensor according to the first embodiment of the present invention. It is a three-view figure showing an example of the composition of the fatigue sensor in a 2nd embodiment of the present invention. It is a flow chart which shows a manufacturing method of a fatigue sensor in a 2nd embodiment of the present invention. It is a side view explaining the manufacturing method of the fatigue sensor in a 2nd embodiment of the present invention. It is a side view showing operation of a fatigue sensor in a 2nd embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will not be repeated.
(First embodiment)
The first embodiment of the present invention, which is the basis of each embodiment of the present invention, will be described.

  The configuration in the present embodiment will be described.

  FIG. 1 is a three-view drawing showing an example of the configuration of the fatigue sensor according to the first embodiment of the present invention. In the drawings after FIG. 1 and the subsequent description, the direction in which the fatigue sensor is installed is an example, and the direction in which the fatigue sensor is actually installed is an arbitrary direction according to the direction of the structure in which the fatigue sensor is installed. It may be. In the drawings after FIG. 1 and the subsequent description, when viewed from a certain direction, the width direction of the fatigue sensor is indicated by “Y”, the depth direction is indicated by “X”, and the height (thickness) direction is indicated by “Z”. It will be shown. That is, the X, Y, and Z directions are orthogonal to each other. In each of the Y, X, and Z directions, the right, front, and upward directions are referred to as “positive sides”, and the left, rear, and downward directions are referred to as “negative sides”. In the following description, the positive side in the X direction is the “X +” side, the negative side in the X direction is the “X−” side, the positive side in the Y direction is the “Y +” side, and the negative side in the Y direction is the The “Y−” side, the positive side in the Z direction is also referred to as “Z +” side, and the negative side in the Z direction is also referred to as “Z−” side. 1A is a side view (XZ plan view), FIGS. 1B and 1D are front views (YZ plan view), and FIG. 1C is a top view (XY plan view). ).

  The fatigue sensor 100 is installed on the structure 800. Here, the installation means that the fatigue sensor 100 is fixed to the structure 800 such that stress is generated in the X direction in the fatigue sensor 100 in response to the generation of stress in the structure 800. The fatigue sensor 100 is fixed to the structure 800 by, for example, an adhesive. The adhesive is, for example, a silicone adhesive or an epoxy adhesive.

  The fatigue sensor 100 detects that the degree of fatigue in the fatigue detection unit 110 exceeds a predetermined value based on the occurrence of fracture (fatigue fracture) in the fatigue detection unit 110 (described later) of the fatigue sensor 100. I do. Here, it is assumed that the fatigue proceeds by the repetitive stress applied in the X direction in the fatigue detection unit 110. The fatigue degree is, for example, the degree of fatigue damage according to the minor rule. In this case, the degree of fatigue at which the fatigue detection unit 110 breaks is one. Alternatively, for example, if the magnitude of the repetitive stress (hereinafter, referred to as “repetitive stress value; the repetitive stress value is, for example, the amplitude of the repetitive stress) in the fatigue detection unit 110 is considered to be constant, The degree is a ratio of the number of times that the repetitive stress is generated in the fatigue detection unit 110 (hereinafter, referred to as “repetition number”) to the number of repetitions (hereinafter, referred to as “repetition number of fracture”) at which the fatigue detection unit 110 breaks. is there. Also in this case, the degree of fatigue at which the fatigue detection unit 110 breaks is one.

  It is assumed that the relationship between the degree of fatigue in the structure 800 and the degree of fatigue in the fatigue sensor 100 installed in the structure 800 is known in advance. Here, the fatigue level of the structure 800 is defined in the same manner as the fatigue level of the fatigue sensor 100. For example, it suffices if the relationship that the degree of fatigue in the structure 800 is 50% of the degree of fatigue in the fatigue sensor 100 is known. Such a relationship can be measured by, for example, a fatigue test (test for measuring an SN curve) for the fatigue sensor 100 installed on the structure 800 and the structure 800. For example, when the repeated stress value in the fatigue sensor 100 installed in the structure 800 and the repeated stress value in the structure 800 can be considered to be constant, the number of repeated fractures is measured at each of the repeated stress values.

  That is, when the fatigue level of the fatigue sensor 100 exceeds a predetermined value, it is possible to estimate the fatigue level of the structure 800. For example, when the degree of fatigue of the structure 800 is 50% of the degree of fatigue of the fatigue sensor 100, the degree of fatigue of the structure 800 when the fracture is detected by the fatigue sensor 100 is 50%. The fatigue sensor 100 includes a fatigue detecting unit 110, a tensile force applying unit 120, a tensile force adjusting unit 150, and a fracture detecting unit 170.

  The fatigue detection unit 110 breaks when the stress is repeatedly generated while the fatigue sensor 100 is installed on the structure 800. The fatigue detector 110 is a rod-shaped member (bar) having a constant cross-sectional area in a cross section perpendicular to the X direction (FIGS. 1A to 1C). The fatigue detection unit 110 may be a plate-shaped member (plate material) having a constant cross-sectional area in a cross section perpendicular to the X direction (FIG. 1D). The fatigue detector 110 is made of, for example, a single metal or an alloy. The fatigue detection unit 110 may have a notch (cut, dent, or groove) formed on a side parallel to the X direction. The notch is, for example, a semicircular depression formed on the side. Due to the formation of the notch, the number of repeated fractures of the fatigue detection unit 110 decreases. Further, the fatigue detecting section 110 may be annealed. Since the residual stress in the fatigue detecting unit 110 becomes substantially zero by annealing, the number of repeated fractures of the fatigue detecting unit 110 increases.

  The tensile force applying unit 120 applies a tensile force to the fatigue detecting unit 110 in the X direction. In FIG. 1, the tensile force applying unit 120 includes, for example, an urging unit 121, a pedestal 130, a pedestal 140, an adjustment shaft 151, and a guide 160.

  The urging unit 121 urges the fatigue detecting unit 110 in a direction to pull in the X direction. In FIG. 1, the urging portion 121 is, for example, a wound spring that expands and contracts in the X direction.

  In FIG. 1, the pedestal 130 is, for example, a plate made of an insulator having a thickness direction in the X direction. The pedestal 130 is connected (adhesive or the like) to one end of the fatigue detection unit 110 on the Z + side surface of the concave portion 133 provided on the lower bottom surface (Z− side). The pedestal 130 is connected (adhered or the like) to the structure 800 on the lower bottom surface. The pedestal 130 has a through hole 131 and a through hole 132 formed in the X direction.

  In FIG. 1, the pedestal 140 is, for example, a plate made of an insulator having a thickness direction in the X direction. The pedestal 140 is connected (adhesive or the like) to the other end of the fatigue detection unit 110 on a Z + side surface of a concave portion (not shown) provided on the lower bottom surface (Z− side). The pedestal 140 is connected (adhered or the like) to the structure 800 on the lower bottom surface. The pedestal 140 has a screw hole 141 and a screw hole 142 formed in the X direction.

  The adjusting shaft 151 transmits the force urged by the urging unit 121 to the pedestal 140, and limits the direction in which the tensile force applying unit 120 applies the tensile force to the fatigue detecting unit 110 in the X direction. In FIG. 1, for example, a screw portion 152 and a partition plate 153 are formed on the adjustment shaft 151. The adjusting shaft 151 is screwably engaged with the screw hole 141 at the screw portion 152 (the end portion on the X− side), penetrates the biasing portion 121 (winding spring), and passes through the through hole 131 at the X + side end portion. Is slidably engaged with. Here, the screw portion 152 is held at each position in the X direction with respect to the screw hole 141 by a frictional force between the screw portion 152 and the screw hole 141. The partition plate 153 locks the X-side end of the urging portion 121 (winding spring). The X + end of the urging portion 121 (winding spring) is locked by the pedestal 130.

  The guide 160, together with the adjustment shaft 151, restricts the direction in which the tensile force applying section 120 applies the tensile force to the fatigue detecting section 110 in the X direction. In FIG. 1, for example, the guide 160 is screwed into the screw hole 142 at the X− end, and slidably engages with the through hole 132 at the X + end.

  The tensile force adjusting unit 150 adjusts the tensile force applied to the fatigue detecting unit 110 to a desired value by restricting the shape of the tensile force applying unit 120 (the urging unit 121 in FIG. 1). In FIG. 1, for example, the tensile force adjusting unit 150 is realized by the partition plate 153 of the adjusting shaft 151 and the screw portion 152 of the adjusting shaft 151 in the tensile force applying unit 120. That is, the tensile force adjusting unit 150 moves the screw portion 152 in the X direction with respect to the pedestal 140 by rotating the partition plate 153 around the adjusting shaft 151.

  The break detector 170 detects a break in the fatigue detector 110. In FIG. 1, the break detection unit 170 includes, for example, a fatigue detection unit 110 formed of a conductor and interrupting a current at the time of break. The break detection unit 170 can detect a break in the fatigue detection unit 110 by monitoring the conduction of current in the fatigue detection unit 110 by an external detection circuit (not shown). The break detection unit 170 may include a wiring member 181 and a wiring member 182 formed (for example, soldered) at both ends of the fatigue detection unit 110 in order to monitor conduction of current in the fatigue detection unit 110. External detection circuits are connected to ends of the wiring members 181 and 182 that are not connected to the fatigue detection unit 110.

  A modified example of the present embodiment will be described.

  FIG. 2 is a two-side view showing a modified example of the fatigue sensor according to the first embodiment of the present invention. 2A is a side view (XZ plan view), and FIG. 1B is a front view (YZ plan view). However, in FIG. 2A, a part (a portion surrounded by a dotted line) of the fracture detection unit 171 and the fatigue detection unit 110 is shown in a transparent manner.

  In the fatigue sensor 101 according to the present modification, the break detection unit 171 includes a tension sensor 190 (FIGS. 2A and 2B). The tension sensor 190 is installed (adhered or the like) on the surface of the concave portion 133 on the Z + side. The tension sensor 190 includes a wiring member 183 at one end on the X + side. The end on the X + side of the fatigue detection unit 110 is connected (adhered or the like) to the surface on the Z− side of the tension sensor 190. It is assumed that a sufficient tensile force in the X direction has been applied to the fatigue detecting unit 110 in advance. Then, when the fatigue detector 110 is broken, the output of the tension sensor 190 changes to a specific value (for example, zero). The break detection unit 171 can detect a break in the fatigue detection unit 110 by monitoring the output of the tension sensor 190 by an external detection circuit (not shown). The tension sensor 190 is, for example, a metal strain gauge or a semiconductor strain gauge. The tension sensor 190 is widely known to those skilled in the art and will not be described in detail here. In this modification, the pedestal 130 or the pedestal 140 may be made of a conductor.

  The operation in the present embodiment will be described.

  FIG. 3 is a flowchart illustrating a method for manufacturing a fatigue sensor according to the first embodiment of the present invention. Note that the flowchart shown in FIG. 3 and the following description are merely examples, and the order of processing, the like, the processing may be returned, or the processing may be repeated according to the processing that is appropriately obtained.

  With reference to FIG. 3, a method for manufacturing the fatigue sensor 100 according to the present embodiment will be described.

  First, the internal stress of the fatigue detector 110 is adjusted to a predetermined internal stress value (Step S110). The fatigue detector 110 is formed by, for example, cold rolling. If a wider variation is required for the sensitivity of the fatigue sensor 100, the variation of the fatigue detector 110 may be different depending on the post-processing such as the presence or absence of notch formation and the presence or absence of annealing for the fatigue detector 110 after formation. It may be prepared. Here, it is assumed that the fatigue characteristics (part of the SN curve) of the fatigue detection unit 110 are known by performing a fatigue test on the sample of the fatigue detection unit 110. When the fatigue detection unit 110 has a plurality of variations, the fatigue characteristics of another variation may be estimated based on the known fatigue characteristics of a certain variation, the measurement result of the internal stress of another variation, and the like. .

  Next, the fatigue sensor 100 is assembled from the fatigue detecting unit 110, the tensile force applying unit 120, the tensile force adjusting unit 150, and the fracture detecting unit 170 (Step S120).

  Then, the tension applied to the fatigue detecting unit 110 by adjusting the tension adjusting unit 150 is adjusted to a desired value (step S130). Here, when a variation is required for the sensitivity of the fatigue sensor 105, each variation is manufactured by adjusting the force for changing the shape of the tensile force applying unit 120 (the urging unit 121 in FIG. 1). For example, it is assumed that the relationship between the tensile force applied to the fatigue detection unit 110 and the parameters used when manufacturing variations of the fatigue sensor 100 is known by a fatigue test or the like on a sample of the fatigue sensor 100. When manufacturing the sample of the fatigue sensor 100, for example, the manufacturing parameters such as the shape of the tensile force applying unit 120 (the length of the urging unit 121 in FIG. 1) and the external force applied to the tensile force applying unit 120 are recorded. I will keep it. Then, when manufacturing the variation of the fatigue sensor 100, if the recorded manufacturing parameters are reproduced, the variation of the fatigue sensor 100 having the same fatigue characteristics as the sample can be manufactured. Alternatively, the sensitivity of each fatigue sensor 100 may be determined by measuring the residual stress in the manufactured fatigue sensor 100 using the cos α method (described later) or the like.

  Through the above operation, the fatigue sensor 100 can be manufactured. Here, for example, by changing the presence / absence of annealing after the cold rolling of the fatigue detection unit 110 and the presence / absence of notch formation, the fatigue characteristics of the fatigue detection unit 110 can be varied. In addition, by adjusting the force for changing the shape of the tensile force applying unit 120 (the urging unit 121) and changing the tensile force (residual stress) with respect to the fatigue detecting unit 110, the fatigue characteristics of the fatigue detecting unit 110 are varied. Can be provided. As a result, the fatigue sensors 100 having different fatigue characteristics of the fatigue detector 110 can be easily manufactured.

  In general, if the material, the material, the shape, the state, or the like is different, the number of repetition of breakage of the material is different. Omission of annealing, notch formation, increase in tensile force, and the like with respect to the fatigue detection unit 110 decrease the number of repeated fractures in the fatigue detection unit 110. The fatigue sensor 100 detects that the fatigue has reached a predetermined value due to the fracture of the fatigue detection unit 110. That is, the omission of the annealing, the formation of the notch, and the increase in the tensile force with respect to the fatigue detection unit 110 increase the sensitivity of the fatigue sensor 100 (however, the value of the sensitivity decreases).

  With reference to FIG. 1 again, an operation in which the fatigue sensor 100 according to the present embodiment detects fatigue will be described.

  In the following description, for the sake of simplicity, it is assumed that a cyclic stress having a predetermined cyclic stress value occurs at some frequency in the structure 800. When the number of repetitions at which the repetitive stress is generated reaches the number of repetition of fractures of the structure 800, the structure 800 is to be fractured. Further, in the fatigue sensor 100 installed in the structure 800, a repetitive stress having another predetermined repetitive stress value is generated at the same frequency as that in the structure 800, corresponding to the repetitive stress generated in the structure 800. I decided to. Then, when the number of repetitions reaches the number of repetition of breakage of the fatigue detection unit 110, it is assumed that breakage occurs in the fatigue detection unit 110 of the fatigue sensor 100.

  First, the fatigue sensor 100 is installed on the structure 800. The fatigue sensor 100 is fixed to the structure 800 by, for example, a silicone-based adhesive. As a result, in the fatigue sensor 100, a repeated stress is generated corresponding to the repeated stress generated in the structure 800.

  In the fatigue sensor 100, the fatigue detection unit 110 is broken according to the sensitivity determined at the time of manufacturing (the number of repeated fractures when a predetermined repeated stress value is generated). Here, a plurality of fatigue sensors 100 having different sensitivities may be installed in the structure 800 according to the fatigue characteristics of the structure 800. For example, the fatigue sensor 100 having a sensitivity of 50% and the fatigue sensor 100 having a sensitivity of 70% of the number of repetitions of the fracture of the structure 800 may be installed on the structure 800.

  The fatigue sensor 100 detects a break in the fatigue detection unit 110 by detecting a small current flowing through the break detection unit 170.

  As described above, by installing the fatigue sensor 100 having a sensitivity corresponding to the fatigue characteristics of the structure 800, the fatigue of the structure 800 can be monitored. For example, by installing a plurality of fatigue sensors 100 having different sensitivities on a structure, the progress of fatigue in the structure 800 can be monitored (measured). Then, the maintenance person of the structure 800 shortens the inspection interval after detecting the repetition number of 50% of the number of repetitions of the fracture in the structure 800, for example, and reduces the inspection interval to 70% of the number of repetitions of the fracture in the structure 800. When the is detected, the structure 800 is replaced or repaired.

  The operation of the fatigue sensor 101 of the modification of FIG. 2 is the same as the operation of the fatigue sensor 100.

  As described above, the fatigue sensor 100 according to the present embodiment includes the fatigue detecting unit 110, the tensile force applying unit 120, the tensile force adjusting unit 150, and the fracture detecting unit 170. The tensile force applying unit 120 applies a tensile force to the fatigue detecting unit 110. The tensile force adjusting unit 150 adjusts the tensile force applied to the fatigue detecting unit 110 to a desired value by restricting the shape of the tensile force applying unit 120. That is, in the fatigue sensor 100, even when the fatigue detection unit 110 having the same fatigue characteristics is used, variations in sensitivity of the fatigue sensor 100 are increased by adjusting the tensile force applied to the fatigue detection unit 110. It is possible. Therefore, the fatigue sensor 100 according to the present embodiment has an effect that the fatigue sensor 100 that can easily set a desired sensitivity can be provided. This effect is the same for the fatigue sensor 101.

  Further, in the fatigue sensor 100 according to the present embodiment, the sensitivity of the fatigue sensor 100 can be changed depending on whether or not there is annealing, whether or not a notch is formed, when manufacturing the fatigue detecting unit 110. Therefore, the fatigue sensor 100 according to the present embodiment has an effect that it is easy to further increase the variation regarding the sensitivity of the fatigue sensor 100. This effect is the same for the fatigue sensor 101.

  Further, in the fatigue sensor 100 according to the present embodiment, when the fracture detection unit 170 includes the fatigue detection unit 110 formed of a conductor and interrupting the current at the time of fracture, the number of components is small. Therefore, there is an effect that the manufacturing cost of the fatigue sensor 100 can be further reduced.

The fatigue sensor 100 or 101 according to the present embodiment may be used for detecting, among fatigue, thermal fatigue. Thermal fatigue is fatigue caused by thermal stress. Generally, the structure 800 undergoes deformation (thermal strain: thermal expansion or thermal contraction) with a change in temperature. The thermal stress is a stress generated inside the structure 800 in response to thermal strain when free deformation of the structure 800 is restricted. However, if the structure 800 is made of a plurality of materials, if it is made of a non-uniform material, or if the temperature is uneven, even if the free deformation of the structure 800 is not restricted from the outside, Thermal stress may be generated inside the structure 800. That is, the structure 800 may expand and contract in the X direction with a change in temperature.
(Second embodiment)
Next, a second embodiment of the present invention based on the first embodiment of the present invention will be described. In the fatigue sensor according to the present embodiment, the urging portion is a leaf spring. In this embodiment, a method for manufacturing a fatigue sensor will be described in more detail.

  The configuration in the present embodiment will be described.

  FIG. 4 is a three-view drawing showing an example of the configuration of the fatigue sensor according to the second embodiment of the present invention. 4A is a side view (XZ plan view), FIG. 4B is a front view (YZ plan view), and FIG. 4C is a top view (XY plan view). However, FIGS. 4B and 4C show a state in which the tensile force adjusting unit 155 has been removed.

  The fatigue sensor 105 according to the present embodiment is installed on a structure 800. The fatigue sensor 105 detects thermal fatigue or fatigue other than thermal fatigue. In the following description, when the fatigue sensor 105 detects thermal fatigue, the structure 800 expands and contracts in the X direction according to a temperature change. That is, when detecting fatigue (the fatigue may be thermal fatigue), the fatigue sensor 105 expands and contracts in the X direction according to expansion and contraction of the structure 800. The fatigue sensor 105 includes the fatigue detecting unit 1, a tensile force applying unit 125, a tensile force adjusting unit 155, and a break detecting unit 175.

  The fatigue detection unit 1 is broken by repeatedly applying stress in the X direction in a state where the fatigue sensor 105 is installed on the structure 800. The fatigue detecting unit 1 is a conductor plate (including a foil) having a constant cross-sectional area in a cross section perpendicular to the X direction. The thickness of the fatigue detector 1 is, for example, 20 to 30 micrometers. The fatigue detector 1 is made of, for example, silver, oxygen-free copper, or an alloy. Notch may be formed in the fatigue detection unit 1 on a side parallel to the X direction.

  When the fatigue sensor 105 detects thermal fatigue, in the X direction, the linear expansion coefficient of each part constituting the fatigue sensor 105, particularly the linear expansion coefficient of the fatigue detecting unit 1 is different from the linear expansion coefficient of the structure 800. For example, it is desirable to be close enough to zero.

  The tensile force applying unit 125 applies a tensile force to the fatigue detection unit 1 in the X direction. The tensile force applying unit 125 includes the urging unit 23, the thin plate 2, the thin plate 3, and the thin plate 4.

  The urging unit 23 urges the fatigue detecting unit 1 in a direction of pulling in the X direction. The urging portion 23 is a leaf spring whose cross section parallel to the X direction has a substantially semicircular shape. The cross-sectional shape of the urging portion 23 is not limited to a substantially semicircular shape, but is preferably a substantially semicircular shape in which stress is uniformly dispersed. The height of the urging portion 23 (substantially semicircular portion) in the Z direction depends on the thickness of the thin plate 2 and the like, but is, for example, 200 micrometers or less. The urging portion 23 is made of, for example, silver, oxygen-free copper, or an alloy.

  The thin plate 2 includes a flat plate portion 21, a flat plate portion 22, and an urging portion 23 formed between the flat plate portion 21 and the flat plate portion 22 in the X direction. The thickness of the flat plate portion 21 and the flat plate portion 22 of the thin plate 2 is, for example, 20 to 30 micrometers, although it depends on the thickness of the fatigue detection unit 1 and the like. The thin plate 2 is made of, for example, silver, oxygen-free copper, or an alloy.

  The thin plate 3 is a plate made of an insulator that is shorter than the thin plate 2 in the X direction. The thickness of the thin plate 3 depends on the thickness of the fatigue detecting section 1 and the like, but is, for example, about 200 micrometers. The thin plate 3 is made of, for example, ceramics. The thin plate 3 is welded in a state where the thin plate 3 is overlapped in parallel with the flat plate portion 21 at the welding point 32. The thin plate 3 is welded in a state where the thin plate 3 is overlapped in parallel with one end of the fatigue detector 1 at a welding point 31. The welding point 32 and the welding point 31 are metal layers formed to be weldable to the thin plate 3 by sputtering or vacuum deposition.

  The thin plate 4 is a plate made of an insulator that is shorter than the thin plate 2 in the X direction. The thickness of the thin plate 4 is the same as the thickness of the thin plate 3. In the X direction, the combined length of the thin plate 3 and the thin plate 4 is shorter than the length of the thin plate 2. That is, there is a gap between the thin plates 3 and 4 so that the thin plates 3 and 4 do not collide during operation. The thin plate 4 is made of, for example, ceramics. The thin plate 4 is welded in a state where it is overlapped in parallel with the flat plate portion 22 at a welding point 42. The thin plate 4 is welded in a state where it is overlapped at the welding point 41 in parallel with the other end of the fatigue detector 1. The welding point 42 and the welding point 41 are metal layers formed to be weldable to the thin plate 4 by sputtering or vacuum deposition.

  The tensile force adjusting unit 155 adjusts the tensile force applied to the fatigue detecting unit 1 to a desired value by restricting the shape of the urging unit 23. The tensile force adjusting section 155 includes the cover 5 and the filler 6. As in the first embodiment of the present invention, the relationship between the tensile force applied to the fatigue detection unit 1 and the parameters for manufacturing variations of the fatigue sensor 105 is determined by a fatigue test or the like on a sample of the fatigue sensor 105. It shall be known. When the sample of the fatigue sensor 105 is manufactured, for example, the shape of the tensile force applying unit 125 (in FIG. 4, the length in the X direction or the height in the Z direction of the urging unit 23, or the thin plate 3 and the thin plate 4). , And manufacturing parameters such as an external force (for example, the weight of a weight) applied to the tensile force applying unit 125. Then, when manufacturing the variation of the fatigue sensor 105, if the recorded manufacturing parameters are reproduced, the variation of the fatigue sensor 105 having the same fatigue characteristics as the sample can be manufactured. Alternatively, the sensitivity of each fatigue sensor 105 may be determined by measuring the residual stress in the manufactured fatigue sensor 105 by using the cos α method (described later) or the like.

  The cover 5 changes the shape of the urging portion 23 (presses and spreads) by being pressed in the Z-direction while being locked to the urging portion 23. The tensile force (prestress, residual stress) applied to the fatigue detecting unit 1 is determined according to the strength with which the cover 5 presses the urging unit 23. The thickness of the cover 5 depends on the thickness of the thin plate 2 and the like, but is, for example, about 100 micrometers. The cover 5 is made of, for example, glass. The cover 5 is desirably transparent or translucent.

  The filler 6 is filled in the gap between the cover 5 and the tensile force applying unit 125, so that the cover 5 is kept pressed to be locked by the urging unit 23. The filler 6 is, for example, a silicone-based adhesive (resin). When the filler 6 is a resin, the filler 6 can prevent the urging portion 23 and the thin plate 2 from being oxidized. The filler 6 is desirably transparent or translucent. If both the filler 6 and the cover 5 are transparent or translucent, the state of the biasing portion 23 can be visually or visually confirmed by a camera or the like at the time of manufacturing the fatigue sensor 105, so that the failure of the fatigue sensor 105 can be determined. Easy.

  The break detector 175 detects a break in the fatigue detector 1. The break detection unit 175 includes the fatigue detection unit 1 formed of a conductor and interrupting a current at the time of break. The break detection unit 175 can detect a break in the fatigue detection unit 1 by monitoring the conduction of current in the fatigue detection unit 1 by an external detection circuit (not shown). The break detection unit 175 may include, for example, a wiring member 181 and a wiring member 182 formed (for example, soldered) at both ends of the fatigue detection unit 1 in order to monitor conduction of current in the fatigue detection unit 1. Good. External detection circuits are connected to ends of the wiring members 181 and 182 that are not connected to the fatigue detection unit 1.

  The other configuration in the present embodiment is the same as the configuration in the first embodiment.

  The operation in the present embodiment will be described.

  FIG. 5 is a flowchart illustrating a method for manufacturing a fatigue sensor according to the second embodiment of the present invention. However, FIG. 5 shows details of step S130 in the flowchart shown in FIG. 3 and illustrating the method for manufacturing the fatigue sensor according to the first embodiment of the present invention. Note that the flowchart illustrated in FIG. 5 and the following description are merely examples, and the order of processing, the like, the processing may be returned, or the processing may be repeated according to the processing that is appropriately obtained.

  FIG. 6 is a side view (XZ plan view) illustrating a method for manufacturing a fatigue sensor according to the second embodiment of the present invention. Here, in the order of FIGS. 6A, 6B, and 6C, the force for expanding the urging portion 23 increases.

  A method for manufacturing the fatigue sensor 105 according to the present embodiment will be described with reference to FIGS.

  First, the internal stress of the fatigue detector 1 is adjusted to a predetermined internal stress value (Step S110).

  Next, the fatigue sensor 105 is assembled from the fatigue detecting unit 1, the tensile force applying unit 125, the tensile force adjusting unit 155, and the break detecting unit 175 (Step S120). Details are, for example, as follows.

  ● Weld the fatigue detector 1 to the thin plate 3 and the thin plate 4.

  ● The thin plate 2 is welded to the thin plate 3 and the thin plate 4 on the surface opposite to the surface to which the fatigue detection unit 1 is welded.

  ● The wiring member 181 and the wiring member 182 are soldered to either of both ends of the fatigue detecting section 1.

  In a state where the cover 5 is superimposed on the thin plate 2, the urging portion 23 is pressed to spread.

  Subsequently, the tension applied to the fatigue detecting unit 1 is adjusted to a desired value by adjusting the tension adjusting unit 155 (step S130). Here, when a variation is required for the sensitivity of the fatigue sensor 105, each variation is manufactured by adjusting the force for expanding the urging portion 23 (FIG. 6). Details are, for example, as follows.

  ● Pressing of the cover 5 from the Z + side with a predetermined pressing force is started (step S210 in FIG. 5). Here, for example, by placing a weight on the Z + side of the cover 5, the urging unit 23 is pushed and spread with a predetermined pressing force, and as a result, the fatigue detecting unit 1 is pulled with a predetermined tensile force value.

  ● The filler 6 is injected between the cover 5 and the tensile force applying unit 125 (Step S220 in FIG. 5). With this operation, the fixing of the tensile force to the fatigue detecting unit 1 is started.

  Wait for the hardening of the filler 6 (step S230 in FIG. 5). As a result, the tensile force applied to the fatigue detector 1 is fixed.

  ● The pressing of the cover 5 from the Z + side ends (step S240 in FIG. 5). As a result, a desired tensile force is applied to the fatigue detector 1.

  Through the above operation, the fatigue sensor 105 can be manufactured. Here, by changing the presence / absence of annealing, the presence / absence of notch formation, and the like after the cold rolling of the fatigue detection unit 1, variations can be given to the fatigue characteristics of the fatigue detection unit 1. Further, by changing the tensile force (residual stress) on the fatigue detection unit 1 by adjusting the pressing force on the cover 5, the fatigue characteristics of the fatigue detection unit 1 can be varied. As a result, the fatigue sensors 105 having different fatigue characteristics of the fatigue detector 1 can be easily manufactured.

  Next, an operation of detecting fatigue by the fatigue sensor 105 in the present embodiment will be described.

  FIG. 7 is a side view (XZ plan view) showing an operation of the fatigue sensor according to the second embodiment of the present invention. Here, FIG. 7A shows a state where the fatigue sensor 105 is contracted, and FIG. 7B shows a state where the fatigue sensor 105 is expanded.

  In the following description, for the sake of simplicity, it is assumed that a cyclic stress having a predetermined cyclic stress value occurs at some frequency in the structure 800. When the number of repetitions at which the repetitive stress is generated reaches the number of repetition of fractures of the structure 800, the structure 800 is to be fractured. Further, in the fatigue sensor 105 installed in the structure 800, a repetitive stress having another predetermined repetitive stress value is applied at the same frequency as that in the structure 800, corresponding to the repetitive stress generated in the structure 800. Shall be done. Then, when the number of repetitions reaches the number of repeated repetitions of the fatigue detection unit 1, the fracture is generated in the fatigue detection unit 1 of the fatigue sensor 105.

  First, the fatigue sensor 105 is installed on a structure. The fatigue sensor 105 is fixed to the structure 800 by, for example, a silicone-based adhesive. As a result, in the fatigue sensor 105, a repeated stress is generated corresponding to the repeated stress generated in the structure 800 (FIG. 7).

  In the fatigue sensor 105, the fatigue detecting unit 1 is broken according to the sensitivity determined at the time of manufacturing (the number of repeated breaks when a predetermined repeated stress value is generated). Here, a plurality of fatigue sensors 105 having different sensitivities may be installed in the structure 800 according to the fatigue characteristics of the structure 800. For example, the fatigue sensor 105 having a sensitivity of 50% and the fatigue sensor 105 having a sensitivity of 70% of the number of repetitions of the fracture of the structure 800 may be installed on the structure 800.

  The fatigue sensor 105 detects a break in the fatigue detection unit 1 by detecting a small current flowing through the break detection unit 175.

  Thus, by installing the fatigue sensor 105 having a sensitivity corresponding to the fatigue characteristics of the structure 800, the fatigue of the structure 800 can be monitored. For example, by installing a plurality of fatigue sensors 105 having different sensitivities on the structure 800, the progress of fatigue in the structure 800 can be monitored.

  Adjustment of the internal stress value in the fatigue detection unit 1 (step S110 in FIG. 3) will be additionally described. For example, it is assumed that the SN curve of the fatigue detector 1 having no residual stress due to annealing or the like is known in advance by a test or the like. For example, residual stress can be removed by annealing after cold rolling. Based on this SN curve and the residual stress (for example, according to the number of cold rollings) in another fatigue detecting unit 1 of the same material, an SN curve in this other fatigue detecting unit 1 is estimated. (The SN curve is moved downward in the graph by the magnitude of the residual stress). That is, the fatigue detectors 1 having different residual stresses can be used for giving variations to the fatigue characteristics of the fatigue detector 1. Further, by forming a notch on the side parallel to the X direction of the fatigue detecting unit 1, the sensitivity is improved as compared with the fatigue detecting unit 1 having the same residual stress (the SN curve is moved downward in the graph). (Stress concentration effect) is possible. When the material of the fatigue detecting section 1 is a single metal such as silver or oxygen-free copper, the surface residual stress can be measured using the cosα method. By using such a technique, a variation of the fatigue detection unit 1 having a desired sensitivity is prepared by estimating or measuring an SN curve relating to the fatigue detection units 1 having different fatigue characteristics such as residual stress and shape. be able to. Further, by changing the shape of the urging portion 23 based on the above-described variation of the fatigue detection unit 1, the variation of the fatigue sensor 105 can be further increased.

  Other operations in the present embodiment are the same as the operations in the first embodiment.

  As described above, the fatigue sensor 105 in the present embodiment includes the fatigue detecting unit 1, the tensile force applying unit 125, the tensile force adjusting unit 155, and the break detecting unit 175. The tensile force applying unit 125 applies a tensile force to the fatigue detecting unit 1. The tensile force adjusting unit 155 adjusts the tensile force applied to the fatigue detecting unit 1 to a desired value by restricting the shape of the tensile force applying unit 125. That is, in the fatigue sensor 105, even when the fatigue detection unit 1 having the same fatigue characteristics is used, the sensitivity variation of the fatigue sensor 105 is increased by adjusting the tensile force applied to the fatigue detection unit 1. It is possible. Therefore, the fatigue sensor 105 according to the present embodiment has an effect that the fatigue sensor 105 that can easily set a desired sensitivity can be provided.

  The fatigue sensor 105 according to the present embodiment has the same effect as the fatigue sensor 100 according to the first embodiment.

  Further, in the fatigue sensor 105 according to the present embodiment, the tensile force adjusting unit 155 includes the cover 5 and the filler 6. That is, the tensile force adjusting unit 155 can be realized using an inexpensive material. Therefore, the fatigue sensor 105 according to the present embodiment has an effect that the manufacturing cost of the fatigue sensor 105 can be reduced.

  In the fatigue sensor 105 according to the present embodiment, the tensile force applying unit 125 includes the flat plate 21, the flat plate 22, and the urging unit 23 formed between the flat plate 21 and the flat plate 22 in the X direction. including. The biasing portion 23 is a leaf spring whose cross section parallel to the X direction is bent in a substantially semicircular shape. That is, since the tensile force applying unit 125 has a simple shape, it is easy to manufacture. Therefore, the fatigue sensor 105 according to the present embodiment has an effect that the manufacturing cost of the fatigue sensor 105 can be further reduced.

  Further, in the fatigue sensor 105 according to the present embodiment, when the cover 5 and the filler 6 are both transparent or translucent, the state of the urging portion 23 can be checked visually or by a camera or the like when the fatigue sensor 105 is manufactured. Therefore, it is easy to determine whether the fatigue sensor 105 is defective. That is, the tensile force applying unit 125 can be easily inspected during manufacturing. Therefore, when both the cover 5 and the filler 6 are transparent or translucent, the fatigue sensor 105 according to the present embodiment has an effect that the manufacturing cost of the fatigue sensor 105 can be further reduced.

Some or all of the above embodiments may be described as in the following supplementary notes, but are not limited thereto.
(Appendix 1)
A fatigue detection unit that is broken by repeated stress applied in a state where it is installed on a structure,
A tensile force applying unit for applying a tensile force to the fatigue detection unit,
A tensile force adjusting unit that adjusts the tensile force applied to the fatigue detection unit to a desired tensile force value,
A fatigue sensor comprising: a fracture detection unit that detects a fracture in the fatigue detection unit.
(Appendix 2)
The fatigue detector is a member that breaks when the repetitive stress is applied in a first direction,
The tensile force applying unit is configured to:
One end is connected to one end of the fatigue detector,
The other end is connected to the other end of the fatigue detection unit,
2. The fatigue sensor according to claim 1, further comprising an urging unit that urges the fatigue detecting unit in a direction in which the fatigue detecting unit is pulled.
(Appendix 3)
The urging unit is a spring,
The fatigue sensor according to claim 2, wherein the tensile force adjusting unit restricts a shape of the urging unit.
(Appendix 4)
The fatigue according to Supplementary Note 2 or 3, wherein the tensile force applying unit is a thin plate in which the urging unit is a leaf spring having a shape in a cross section parallel to the first direction bent in a substantially semicircular shape, and the urging unit is formed in the middle. Sensor.
(Appendix 5)
The tensile force adjusting unit,
A cover that changes the shape of the urging portion by being pressed while being locked to the urging portion,
Any one of supplementary notes 3 to 4, further comprising a filler that is filled in a gap between the cover and the tensile force applying portion, thereby maintaining a state where the cover is pressed so as to be locked to the urging portion. Item 2. The fatigue sensor according to item 1.
(Appendix 6)
The cover is transparent or translucent,
The fatigue sensor according to claim 5, wherein the filler is transparent or translucent.
(Appendix 7)
The fatigue sensor according to any one of supplementary notes 1 to 6, wherein the fracture detection unit includes the fatigue detection unit formed of a conductor and interrupting a current at the time of fracture.
(Appendix 8)
The fatigue sensor according to any one of supplementary notes 2 to 7, wherein a linear expansion coefficient of the fatigue detector in the first direction is different from a linear expansion coefficient of the structure in the first direction.
(Appendix 9)
The fatigue sensor according to any one of supplementary notes 2 to 8, wherein the fatigue detection unit has a notch formed on a side parallel to the first direction.
(Appendix 10)
The fatigue sensor according to any one of supplementary notes 2 to 9, wherein the fatigue detection unit is a plate or a bar having a constant cross-sectional area in a cross section perpendicular to the first direction.
(Appendix 11)
A fatigue detection unit that is broken by repeated stress applied in a state where it is installed on a structure,
A tensile force applying unit for applying a tensile force to the fatigue detection unit,
A tensile force adjusting unit that adjusts the tensile force applied to the fatigue detection unit to a desired tensile force value,
A fatigue measurement method using a fatigue sensor including a fracture detection unit that detects a fracture in the fatigue detection unit,
A plurality of the fatigue sensors having different internal stress values in the fatigue detection unit are installed on the structure,
A fatigue measurement method for monitoring progress of fatigue in the structure based on the presence or absence of the break detected by each of the fatigue sensors.
(Appendix 12)
A fatigue detection unit that is broken by repeated stress applied in a state where it is installed on a structure,
A tensile force applying unit for applying a tensile force to the fatigue detection unit,
A tensile force adjusting unit that adjusts the tensile force applied to the fatigue detection unit to a desired tensile force value,
A method of manufacturing a fatigue sensor including a fracture detection unit that detects a fracture in the fatigue detection unit,
Internal stress adjustment step of adjusting the internal stress in the fatigue detection unit to a predetermined internal stress value,
An assembly step of assembling a fatigue sensor from the fatigue detecting unit, the tensile force applying unit, the tensile force adjusting unit, and the fracture detecting unit,
A tension adjusting step of adjusting the tensile force applied to the fatigue detecting unit to a desired tensile force value by adjusting the tensile force adjusting unit.

  The present invention provides a method for applying stress (eg, thermal fatigue) to fatigue (for example, thermal fatigue) by attaching a plurality of fatigue sensors having different numbers of repetitions leading to fracture at a predetermined repetitive stress value to a structure (bridge, aircraft body, etc.). It can be used in applications where the number of repetitions of thermal stress) is measured and maintenance is performed at appropriate intervals according to the measurement results.

REFERENCE SIGNS LIST 100, 101 fatigue sensor 110 fatigue detection unit 120 tensile force applying unit 121 urging unit 130, 140 pedestal 133 concave portion 131, 132 through hole 141, 142 screw hole 150 tensile force adjusting unit 151 adjusting shaft 152 screw unit 153 partition plate 160 guide 170, 171 Break detection unit 800 Structure 105 Fatigue sensor 1 Fatigue detection unit 125 Tensile force application unit 2 Thin plate 21, 22 Flat plate unit 23 Urging unit 3 Thin plate 31, 32 Weld point 4 Thin plate 41, 42 Weld point 155 Tension force adjustment Part 5 Cover 6 Filler 175 Break detector 181 Wiring material 182 Wiring material 190 Tension sensor

Claims (10)

A fatigue detection unit that detects fatigue of the structure by being broken by repeated stress being applied in a state where the structure is installed,
A tensile force applying unit for applying a tensile force to the fatigue detection unit,
A tensile force adjusting unit that adjusts the tensile force applied to the fatigue detection unit to a desired tensile force value,
A fatigue sensor comprising: a fracture detection unit that detects a fracture in the fatigue detection unit. The fatigue detector is a member that breaks when the repetitive stress is applied in a first direction,
The tensile force applying unit is configured to:
One end is connected to one end of the fatigue detector,
The other end is connected to the other end of the fatigue detection unit,
The fatigue sensor according to claim 1, further comprising: a biasing portion that biases the fatigue detecting portion in a direction in which the fatigue detecting portion is pulled. The urging unit is a spring,
The fatigue sensor according to claim 2, wherein the tension adjustment unit restricts a shape of the urging unit. The said tensile-force provision part is a thin plate in which the said urging part which is a leaf spring bent in the substantially semicircular shape in the cross section parallel to the said 1st direction was formed in the middle. Fatigue sensor. The tensile force adjusting unit,
A cover that changes the shape of the urging portion by being pressed while being locked to the urging portion,
The filler according to any one of claims 3 to 4, further comprising a filler that is filled in a gap between the cover and the tensile force applying unit, thereby maintaining a state where the cover is pressed so as to lock the urging unit. The fatigue sensor according to claim 1. The cover is transparent or translucent,
The fatigue sensor according to claim 5, wherein the filler is transparent or translucent. The fatigue sensor according to any one of claims 1 to 6, wherein the fracture detection unit includes the fatigue detection unit formed of a conductor and interrupting current at the time of fracture. The fatigue sensor according to any one of claims 2 to 7, wherein a linear expansion coefficient of the fatigue detector in the first direction is different from a linear expansion coefficient of the structure in the first direction. A fatigue detection unit that detects fatigue of the structure by being broken by repeated stress being applied in a state where the structure is installed,
A tensile force applying unit for applying a tensile force to the fatigue detection unit,
A tensile force adjusting unit that adjusts the tensile force applied to the fatigue detection unit to a desired tensile force value,
A fatigue measurement method for the structure using a fatigue sensor including a fracture detection unit that detects a fracture in the fatigue detection unit,
A plurality of the fatigue sensors having different internal stress values in the fatigue detection unit are installed on the structure,
A fatigue measurement method for measuring the progress of fatigue in the structure based on the presence or absence of the break detected by each of the fatigue sensors. A fatigue detection unit that detects fatigue of the structure by being broken by repeated stress being applied in a state where the structure is installed,
A tensile force applying unit for applying a tensile force to the fatigue detection unit,
A tensile force adjusting unit that adjusts the tensile force applied to the fatigue detection unit to a desired tensile force value,
A method of manufacturing a fatigue sensor including a fracture detection unit that detects a fracture in the fatigue detection unit,
Internal stress adjustment step of adjusting the internal stress in the fatigue detection unit to a predetermined internal stress value,
An assembly step of assembling a fatigue sensor from the fatigue detecting unit, the tensile force applying unit, the tensile force adjusting unit, and the fracture detecting unit,
A tension adjusting step of adjusting the tensile force applied to the fatigue detecting unit to a desired tensile force value by adjusting the tensile force adjusting unit.

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