JP6682176B2 - Strain measuring component and strain measuring method using the same - Google Patents

Description

  The present invention relates to a strain measuring component, and more particularly to a strain measuring component suitable for measuring residual stress associated with curing shrinkage and a strain measuring method using the same.

  In order to ensure safety and reliability in the manufacturing of industrial products including the process of curing resin and resin kneaded products, it is necessary to correctly grasp the residual stress due to curing shrinkage of resin etc. And sensors are used.

  In Patent Document 1, a sensor body capable of wirelessly outputting measurement data is resin-molded in a state of being arranged between two metal plates, and the output data regarding the pressure in the three axial directions is received from the sensor body, and A technique is described in which the direction and magnitude of the principal stress are measured to measure the internal stress in a portion of the resin molded component where the sensor body is arranged.

JP 2012-52891 A

  According to the configuration of Patent Document 1, in place of the known strain gauge, there is a problem that it is necessary to prepare a sensor body and a measuring device having a complicated configuration capable of transmitting and receiving output data regarding pressure in the three axial directions and performing calculation. is there.

  That is, the conventional strain gauge has a problem that residual stress due to shrinkage stress or tensile stress generated when the resin or the resin kneaded product is cured in the container cannot be easily and accurately measured.

  Therefore, it is an object of the present invention to provide a strain measuring component and a strain measuring method using the same, which solve the above problems.

  In order to solve the above-mentioned problems, a strain measuring component of the present invention includes a plate-shaped body formed by molding an insulating resin having elasticity, and a strain sensing unit having an input / output terminal unit, The section is derived from the plate-shaped body, and the strain sensing section is embedded in the plate-shaped body such that the plate thickness direction of the plate-shaped body and the strain sensing direction coincide with each other.

  In the strain measuring component of the present invention, the strain sensing section includes a metal resistor.

  In the strain measuring component of the present invention, the strain sensing section includes a semiconductor resistor.

  In the strain measuring component of the present invention, a layer having releasability is provided on a surface other than the plate surface of the plate-shaped body.

  The strain measuring method of the present invention is characterized by using the strain measuring component having the insulating resin and having a coefficient of thermal expansion equal to a coefficient of thermal expansion of an object to be measured.

  A well-known representative strain gauge has a metal foil arranged on an insulating thin plate, and the insulating thin plate is adhered to the object to be measured, so that the object to be measured expands and contracts, that is, the insulating thin plate expands and contracts. The strain amount is measured from the change in the resistance value of the metal foil.

  For example, when a resin kneaded product injected into a container having an opening on the upper surface is cured, the resin kneaded product has a force that shrinks inward with the passage of time, that is, shrinkage stress and adhesion to the inner wall of the container. The resulting tensile stress acts, and these forces remain as residual stress in the resin kneaded product after curing.

  Consider a case where a well-known representative strain gauge is used to measure the tensile stress generated between two opposing inner walls in the container. The strain gauge is embedded in the resin kneaded material as the object to be measured such that the front and back surfaces of the insulating thin plate are parallel to the bottom surface of the container. The tensile stress is detected as the amount of strain due to the expansion and contraction of the resin adhered to the front and back surfaces of the strain gauge, that is, the front and back surfaces of the insulating thin plate.

  However, the tensile stress generated is minute and the output is small. In addition, since Poisson contraction occurs from the opening of the container, that is, from the liquid surface of the resin kneaded material to the bottom surface, the strain amount due to the tensile stress cannot be accurately detected on the surface of the strain gauge.

 In addition, the tensile stress generated on the inner wall, that is, the force in the direction perpendicular to the inner wall, which is most likely to be detected, has a small area of the thickness portion of the insulating thin plate.

  In the strain measuring component according to the present invention, a strain sensing part including a metal resistor such as a metal wire or a metal foil or a semiconductor resistor is a plate-shaped body made of a resin having elasticity, and the strain sensing direction of the strain sensing part is plate-shaped. It is embedded so as to be substantially parallel to the plate thickness direction of the body, and for example, the amount of strain caused by the tensile stress generated between two opposing inner sidewalls in the container is detected by the plate surface of the plate body.

  That is, the configuration is such that a minute amount of strain is efficiently detected on a plate surface having a large area to be detected.

  Further, the strain measurement component according to the present invention, by forming a layer having releasability on the surface other than the plate surface for detecting the amount of strain, weakens the adhesive strength with the resin kneaded material, and reduces the contraction stress as much as possible. Use a configuration that excludes the effects.

  The strain measurement component according to the present invention is embedded in a required number in the object to be measured, and the input / output terminal part derived from the strain sensing part is connected to an external measuring device to be placed in the object to be measured. The generated force is detected and the amount of strain is measured.

  At this time, a more accurate strain amount can be obtained by selecting and using a strain measurement component in which a plate-shaped body is made of a material having a thermal expansion coefficient equal to or substantially equal to the thermal expansion coefficient of the measured object. it can.

  ADVANTAGE OF THE INVENTION According to this invention, the strain measuring component and strain measuring method which can measure residual stress produced when hardening resin or a resin kneaded material in a container at low cost simply and accurately are obtained.

It is explanatory drawing which shows 1st Embodiment in the distortion measurement component of this invention. It is explanatory drawing which shows 2nd Embodiment in the distortion measuring component of this invention. It is a figure which shows the distortion amount measurement result in the distortion measuring component of this invention, and a comparative example.

  Hereinafter, embodiments of the present invention will be described in detail.

(First embodiment)
FIG. 1 is an explanatory view showing a first embodiment of a strain measuring component of the present invention.

  A strain sensing portion 1 formed by forming a metal foil pattern on an insulating thin plate is embedded in the central portion of a plate-like body 2 made of a resin having elasticity so that the strain sensing direction and the direction of the plate thickness h coincide with each other. Then, the strain measuring component 100 is configured.

  The input / output terminal portion 11 led out from the end of the strain sensing portion 1 is drawn out of the plate-shaped body.

  The strain sensing unit 1 is preferably selected from known strain gauges in which metal resistors and semiconductor resistors are pattern-arranged on an insulating thin plate, and is preferably used. However, the strain sensing unit 1 is directly embedded in the resin forming the plate-shaped body 2. Good. Moreover, you may provide the some distortion detection part 1 in one plate-shaped body as needed.

  The strain sensing unit 1 may be embedded at any position, but it is preferable to dispose the strain sensing unit 1 in the vicinity of the central portion of the plate-shaped body 2 which is less likely to be affected by stress outside the sensing target.

  As the resin constituting the plate-shaped body 2, a resin having elasticity under at least an environment for strain measurement is used, but a resin having a tensile elastic modulus of about 1 MPa to 40 GPa at −40 to 200 ° C. is preferable, and the resin to be measured is Those having the same elastic modulus are particularly preferable.

  Further, the resin forming the plate-shaped body 2 is a metal resistor or a semiconductor resistor included in the strain sensing portion 1, an insulating thin plate as necessary, and further, an object to be measured so as to be in close contact with the object to be measured. It is preferable that the adhesive has an adhesive force of about several MPa to several hundred MPa depending on the breaking strength.

  In view of the above, the resin forming the plate-shaped body 2 is preferably a silicone resin or an epoxy resin having a so-called low elastic modulus, or a resin contained in another object to be measured.

  The plate-shaped body 2 preferably has a disk shape including a plate surface and a side peripheral surface, but the plate surface may be substantially flat, and the plate surface may have a circular shape, a quadrilateral shape, a polygonal shape, or a geometrical shape. It may be indefinite without being bound by the definition.

  The maximum dimension d of the plate surface, for example, the diameter in FIG. 1, is preferably 1 time or more and 20 times or less the plate thickness h, and in order to effectively eliminate the influence of curing shrinkage and to detect the tensile stress efficiently, It is particularly preferable that the thickness h is 2 times or more and 15 times or less. In consideration of the strength of the plate-shaped body 2, the maximum dimension d of the plate surface is more preferably 5 times or more and 10 times or less the plate thickness h.

  When a known strain gauge is used as the strain detection unit 1, the plate thickness h is preferably 1 mm or more in consideration of the size of the strain gauge. Further, the upper limit of the plate thickness h is preferably 10 mm or less, which can eliminate the influence of curing shrinkage. In order to further improve the measurement accuracy, it is preferable that the plate thickness h is 1 mm or more and 5 mm or less.

  A surface other than the plate surface of the plate-shaped body 2, that is, the side peripheral surface is coated with a release agent in order to eliminate the influence of a force other than the measurement target force, for example, a force caused by curing shrinkage such as Poisson shrinkage. It is preferable to form a layer having releasability.

  The release agent may be appropriately selected and used from known release agents, but one having an adhesive force of 0.1 MPa or less is preferable, and a die-free (registered trademark) of Daikin Industries, Ltd., Chemlease Japan KK It is particularly preferable to use a release agent made of a fluororesin or a silicone resin such as Monocoat (registered trademark).

  The method for forming the layer having releasability may be appropriately selected from known means such as application and spraying of a release agent.

(Second embodiment)
FIG. 2 is an explanatory view showing a second embodiment of the strain measuring component of the present invention, and shows a usage state of the strain measuring component of the present invention.

 The DUT 3 made of a resin kneaded product is poured into a container 4. In the strain measuring component 100, the strain detecting direction of the strain detecting unit 1 is set to the inner wall of the container 4 in order to measure the strain amount caused by the tensile stress F1 and the tensile stress F2 generated by the adhesion between the container 4 and the DUT 3. It is arranged vertically.

  That is, the strain detection direction of the strain detection unit 1 and the directions of the tensile stress F1 and the tensile stress F2 are arranged to be substantially parallel.

  The input / output terminal portion 11 of the strain measuring component 100 is pulled out from the open surface of the DUT 3 and connected to an external measuring device (not shown).

  The position of the strain measuring component 100 inside the device under test 3 may be appropriately selected as necessary.

  Further, a plurality of strain measuring components 100 may be used as needed.

  The strain measuring component 100 provided with the plate-like body 2 made of a resin having a thermal expansion coefficient equal to that of the resin contained in the object to be measured 3 is selectively used because the force other than the measurement target due to the difference in the thermal expansion coefficient is used. Is more preferable in eliminating.

  As a product of the present invention, a plate-shaped body 2 made of an epoxy resin having a tensile elastic modulus of 17 GPa at 25 ° C., an insulating thin plate made of an epoxy resin used for the plate-shaped body as the strain sensing portion 1, and Cu- A disc-shaped strain measuring component 100 having a plate surface maximum dimension d of 15 mm and a plate thickness h of 1.5 mm was prepared, which was provided with a known strain gauge using a Ni-based metal foil.

  In addition, as a comparative example, the same strain gauge simple substance as that used as the strain sensing unit 1 of the present invention was prepared.

  As the DUT 3, a magnetic slurry containing an epoxy resin that cures and shrinks at about 120 ° C. was prepared.

  As the container 4 into which the DUT 3 is injected and cured, a SUS container and a polypropylene container having a square bottom and the same shape and the same volume were prepared.

  The present invention product and the strain gauge alone as the comparative example are placed in the center of the container 4 into which the DUT 3 is injected so that the strain sensing direction is horizontal or vertical, and the DUT 3 is heated to 120. The amount of strain was determined by holding the temperature in the vicinity of ° C and connecting the input / output terminal portion 11 to an external measuring device.

  FIG. 3 is a diagram showing the results of strain amount measurement in the strain measuring component of the present invention and the comparative example, and shows the transition of each strain amount obtained in the above-described configuration.

  The left vertical axis indicates the amount of strain, a positive value indicates elongation and a negative value indicates contraction. The vertical axis on the right shows the temperature, and the horizontal axis shows the elapsed time from the start of heating.

  The strain amount transition Sh indicates a change in strain amount due to hardening of the magnetic slurry when the product of the present invention is placed in the SUS container so that the strain detection direction is horizontal.

  The strain amount transition Sp shows a change in strain amount due to hardening of the magnetic slurry when the product of the present invention is arranged in the SUS container so that the strain detection direction is vertical.

  The strain amount change Ph represents a change in strain amount due to hardening of the magnetic slurry when the product of the present invention is arranged in a polypropylene container so that the strain detection direction is horizontal.

  The strain amount transition Pp indicates a change in strain amount due to hardening of the magnetic slurry when the product of the present invention is arranged in a polypropylene container in a vertical direction so that the strain detection direction is vertical.

  The strain amount transition PAh shows a change in strain amount due to hardening of the magnetic slurry when the strain gauge of the comparative example is placed alone in a polypropylene container so that the strain detection direction is horizontal.

  The strain amount transition PAp shows a change in strain amount due to hardening of the magnetic slurry when the strain gauge of the comparative example is placed alone in a polypropylene container so that the strain detection direction is vertical.

  The temperature transition Tm represents a temperature change inside the DUT 3, and the temperature transition Ta represents a temperature change in the atmosphere in which the container 4 is placed.

  The strain amount transition PAh and the strain amount transition PAp obtained by using the strain gauge alone as a comparative example both start shrinking as the temperature inside the DUT 3 rises, and finally reach the curing shrinkage start point. The amount of strain B due to curing shrinkage, which is the amount of change from A, was recorded.

  On the other hand, the strain amount transitions Sh, Sp, Ph, and Pp obtained by using the product of the present invention all showed a change in strain amount due to elongation.

  It can be seen that when the product of the present invention is used, the strain amount due to elongation, that is, the tensile stress F1 and the tensile stress F2 in FIG. 2 is detected regardless of the material of the container 4.

  From the above, the residual stress generated when the resin or the resin kneaded product is cured in the container, especially the tensile stress, at low cost, a strain measurement component that can be easily and accurately measured and a strain measurement method using the same Was obtained.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above, and changes and modifications of the configuration are possible without departing from the gist of the present invention. That is, various variations and modifications that can be made by those skilled in the art are also included in the present invention.

1 Strain Detecting Section 11 Input / Output Terminal Section 2 Plate-like Object 3 Object to be Measured 4 Container 100 Strain Measuring Component d Maximum Plate Size Dimension h Plate Thickness F1, F2 Tensile Stress A Cure Shrinkage Start Point B Strain Amount Due to Cure Shrink Sh, Sp, Ph, Pp, PAh, PAp Strain amount transition Tm, Ta Temperature transition

Claims (4)

  The insulating resin having elasticity is molded, and includes a plate member having a circular, polygonal, or irregular plate surface and a side peripheral surface of the plate surface, and a strain sensing portion having an input / output terminal portion. The maximum dimension of the plate surface is not less than 2 times and not more than 15 times the plate thickness of the plate body, the input / output terminal portion is led out from the plate body, and the strain sensing portion includes a metal resistor. A strain measuring component, wherein the strain measuring component is embedded in the plate so that a plate thickness direction of the plate and a strain detection direction coincide with each other.   The insulating resin having elasticity is molded, and includes a plate member having a circular, polygonal, or irregular plate surface and a side peripheral surface of the plate surface, and a strain sensing portion having an input / output terminal portion. The maximum dimension of the plate surface is not less than 2 times and not more than 15 times the plate thickness of the plate-shaped body, the input / output terminal portion is led out from the plate-shaped body, and the strain sensing portion includes a semiconductor resistor. A strain measuring component, wherein the strain measuring component is embedded in the plate so that a plate thickness direction of the plate and a strain detection direction coincide with each other.   The strain measuring component according to claim 1 or 2, wherein the side peripheral surface of the plate-shaped body is provided with a layer having releasability. The strain measuring component according to any one of claims 1 to 3, which has the thermal expansion coefficient equal to the thermal expansion coefficient of the measured object, is embedded in the measured object, and the measured object is embedded in the measured object. strain measuring method characterized that you measure the amount of distortion by detecting the force generated within.

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