JP2003185507A - Tape and method for measuring stress distribution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stress distribution measuring tape and a stress distribution measuring method which enable easy measurement of a stress distribution on a specific straight line, polygonal line, or curve, which is performed by applying the tape on a structure. <P>SOLUTION: The stress distribution measuring tape formed by applying a plurality of anisotropic piezoelectric materials to one surface of a base material tape changing their direction of anisotropy to at least two directions, is caused to adhere to the surface of a structural member. The surface potentials of the anisotropic piezoelectric materials are measured by a noncontact system using a surface electrometer, and the surface potential values are substituted in a piezoelectric equation, and the stress distribution of the member is found. Besides, the measuring probe of the surface electrometer is attached to a holder and put on the upper surface of an anisotropic piezoelectric material, the holder is moved and surface potentials are measured quickly at a large number of spots. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a straight line connecting two specific points on the surface of a member in the stress measurement of a machine or a structure,
The present invention relates to a stress distribution measuring tape that can easily measure a stress distribution on a polygonal line or a curve, and a stress distribution measuring method using the stress distribution measuring tape.

[0002]

2. Description of the Related Art Strain gauges have been widely used for measuring the stress of machines and structures. However, since the strain gauge can measure the stress at the bonded portion of the strain gauge, the strain gauge can be measured on a specific line or surface of the member surface. It was necessary to bond a large number of strain gauges to measure the stress distribution of. In addition, it is necessary to use a biaxial or triaxial strain gauge to obtain the stress component of a member in a two-dimensional stress state, and in the strain measurement at a large number of points, the number of channels of the electric wiring and the strain measuring instrument increases and the device There was a problem that it would be a big problem.

Recently, as a method for measuring the stress distribution on a specific line or surface of a structural member, an optical fiber,
Optical methods using thermography or moire fringes have been proposed. These have the advantage that the stress distribution can be measured in a non-contact manner and multi-point measurement is possible, but since the measuring equipment is expensive and susceptible to the environment such as temperature and vibration, it is not possible to perform on-site measurement of actual structures. There was a problem that it was not easy.

[0004]

An object of the present invention is to easily measure the stress distribution on a specific straight line, broken line or curved line on the surface of a structure by using a piezoelectric material for strain sensing.

When a strain is applied to the piezoelectric material, the piezoelectric material is polarized and an electric potential is generated on a specific surface of the piezoelectric material. This potential is proportional to the applied strain according to the piezoelectric equation. Therefore, the member stress can be obtained by bonding the piezoelectric material to the structural member and measuring the potential of the surface of the piezoelectric material with a non-contact type surface electrometer.

Since the surface of the structural member is generally in a two-dimensional stress state, it is necessary to install an anisotropic piezoelectric material having directionality in strain sensing in order to separately determine the stress component. For example, when the surface potentials V _x , V ₄₅ , and V _Y of three anisotropic piezoelectric materials (PVDF) bonded so that the directions of the principal axes of anisotropy are 0 degree, 45 degrees, and 90 degrees, the member surface is measured. Σ _X , σ
It is shown in Japanese Patent Application No. 2000-366269 that _Y and shear stress τ _XY can be obtained by solving the simultaneous equations of Equation 1.

[0007]

[Equation 1] In the above equation, a1 and a2 are coefficients that depend on the characteristics of the anisotropic piezoelectric material, the Young's modulus and Poisson's ratio of the structural member, and the bonding conditions.

By the way, on a specific straight line on the surface of the structural member,
In order to measure the stress distribution on a polygonal line or on a curved line, it is necessary to accurately adhere a large number of anisotropic piezoelectric materials to the surface of the member with a simple method. An object of the present invention is to easily measure the stress distribution of a structural member by providing a stress distribution measuring tape in which a plurality of anisotropic piezoelectric materials are changed in the anisotropic direction and bonded accurately.

In order to measure the surface potential of a large number of piezoelectric materials adhered to a structural member, it is effective to apply a non-contact type surface electrometer. Some high-speed type surface electrometers can measure the surface potential at a high speed of millisecond or less (for example, according to the Trek Japan catalog, the response time of Mode 1362A is 200 μsec). However, when the measurement probe of the surface electrometer is held in the hand to measure the surface potentials at many points, problems such as camera shake occur. Therefore, it is an object of the present invention to provide a method for efficiently measuring a surface potential by attaching a measuring probe to a holder.

[0010]

In order to solve the above problems, the first stress distribution measuring tape of the present invention is [1] a piezoelectric material as a strain sensing portion is regularly arranged and bonded on one surface of a support tape. A stress distribution measuring tape, comprising: a support tape made of an insulating material; and a plurality of anisotropic piezoelectric materials adhered side by side in one surface of the support tape while changing their anisotropic directions in at least two directions. The stress distribution measuring tape, comprising a shape of the anisotropic piezoelectric material marked on the surface of the support tape to which the anisotropic piezoelectric material is not adhered and a mark indicating the anisotropic direction, It is characterized in that stress is measured by adhering to the surface of the structural member so that the mark of the anisotropic piezoelectric material can be seen.

The second stress distribution measuring tape of the present invention is [2] a stress distribution measuring tape in which piezoelectric materials as strain sensing portions are regularly arranged on one surface of a support tape and adhered with a peelable adhesive. And a transparent support tape, a plurality of anisotropic piezoelectric materials which are arranged and adhered on one surface of the support tape while changing anisotropic directions in at least two directions, and the anisotropic piezoelectric material. And a mark indicating the anisotropic direction of the anisotropic piezoelectric material, which is marked on the contact surface of the material with the adhesive, and the stress distribution measuring tape is structured so that the mark of the anisotropic piezoelectric material can be seen. After adhering to the surface of the member, the pressure-sensitive adhesive is peeled off between the support tape and the anisotropic piezoelectric material to remove the support tape, and the stress measurement is performed with the surface of the anisotropic piezoelectric material exposed. To do.

Further, in order to measure the stress distribution in the non-conductive structure, [3] the stress distribution measuring tape according to the above [1] or [2] was attached to one surface of the support tape. On the surface of the anisotropic piezoelectric material, further, a metal film is adhered in a shape that covers the entire surface of the anisotropic piezoelectric material and a part of the anisotropic piezoelectric material protrudes outside the support tape, and a surface potential is applied to the metal film. It is characterized by connecting the ground terminal of the meter to the reference potential.

The first stress distribution measuring method of the present invention is [4] in the stress measurement using the stress distribution measuring tape according to the above [1] to [3], the surface potential of an anisotropic piezoelectric material is measured. A vibration capacitance type and distance compensation type surface electrometer was used for the measurement, the measurement probe of the surface electrometer was attached to a holder, and the holder was placed on the upper surface of an anisotropic piezoelectric material adhered to a structural member for measurement. It is characterized in that the position of the probe is held and that the holder is moved on the upper surface of the anisotropic piezoelectric material to measure the surface potential.

The second stress distribution measuring method of the present invention is [5] a stress measurement using the stress distribution measuring tape described in [1] to [3] above. The tool is placed on the upper surface of the anisotropic piezoelectric material to hold the position of the metal plate 57a, and the electric wiring is connected to the metal plate 57a to another metal plate 57b placed at a position away from the stress measurement position. One end is connected, a measurement probe of a surface electrometer is brought close to the metal plate 57b to fix the gap with the metal plate 57b, and the holder is moved on the upper surface of the anisotropic piezoelectric material to make the surface It is characterized in that the electric potential was measured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1A is a diagram showing the structure of a stress distribution measuring tape according to an embodiment of the present invention. On one surface of the thin support tape 1 made of an insulating material such as a resin film, the anisotropic piezoelectric materials 2a, 2b, and 2c are provided with the anisotropic main axes at 0 °, 45 °, and 0 ° to 45 ° with respect to the length direction of the support tape 1. Three pieces are arranged as one set so as to face the direction of 90 degrees, and the same set is repeatedly arranged in the length direction of the support tape 1 and bonded with the adhesive 3.

An example of the anisotropic piezoelectric material is a polymer anisotropic piezoelectric material PVDF. PVDF is thin, flexible and easy to process. There are PVDF whose surface is treated with an electrode and those whose surface is not treated with an electrode. Both of them can be used for stress measurement, but considering the adhesive force, those not treated with an electrode are preferable.

On the surface of the support tape 1, which is the back surface of the surface to which the anisotropic piezoelectric materials 2a, 2b, 2c are adhered,
A mark 6 indicating the shape of the anisotropic piezoelectric material and the direction of the anisotropic main axis is marked by printing or the like. The rectangular mark 6 in the figure represents the shape and the bonding position of the anisotropic piezoelectric material, and the straight line inside the rectangle represents the direction of the anisotropic principal axis.

FIG. 1 (b) is a view for explaining a method of adhering a stress distribution measuring tape to a structure. First, the surface of the member is ground with an emery paper or the like, then placed on the surface of the structural member so that the mark 6 of the piezoelectric material marked on the support tape can be seen, and the surface of the piezoelectric material is bonded to the member with the adhesive 4. In the stress distribution measuring tape of FIG.
Anisotropy principal axes of one piece of anisotropic piezoelectric material are 0 degree, 45 degree, and 9
Since the arrangement is such that the direction of 0 degree is formed, the surface potentials V _x , V ₄₅ , and V _Y of three adjacent sheets are measured, and σ _X , σ _Y, and τ obtained by substituting them into Equation 1 are obtained. _{Let XY} be the stress at the center of gravity of the three sheets. When the surface potential is measured by shifting the set of three adjacent sheets, a discrete stress distribution can be obtained in the length direction of the support tape.

The stress distribution measuring tape may be used as a long tape by adhering a plurality of tapes in series,
It can also be cut to the required length with scissors and used.
Further, a long stress distribution measuring tape wound in a roll may be prepared.

FIG. 2A is a diagram showing an embodiment of a stress distribution measuring tape in which an anisotropic piezoelectric material is attached to a support tape with a peelable adhesive 5. Anisotropic piezoelectric material 2a,
A piezoelectric material having an anisotropic principal axis direction marked by printing or the like on one surface of 2b or 2c is regularly attached to a transparent support tape with an adhesive 5. This is bonded with an adhesive 4 on the surface of the structural member so that the marks 6 of the anisotropic piezoelectric materials 2a, 2b, 2c can be seen. After the adhesive has dried, the adhesive 5 between the support tape 1 and the anisotropic piezoelectric material is peeled off to remove the support tape 1 so that the surface of the anisotropic piezoelectric material is exposed.

FIG. 2B shows the adhesive 5 of the support tape 1.
3 shows a cross section of the anisotropic piezoelectric material 2a, 2b, 2c during peeling. In this stress distribution measuring tape, since the surface of the anisotropic piezoelectric material is exposed after the support tape is removed, it is possible to measure the surface potential by bringing the measurement probe of the surface electrometer closer to the surface of the piezoelectric material. Alternatively, the surface potential can be measured by coating the upper surface of the anisotropic piezoelectric material.

FIG. 3A is a view showing an embodiment of the stress distribution measuring tape of the present invention when the stress distribution is measured in a non-conductive structure. Since the non-conductive structure cannot set the potential of the structure itself to the reference potential, the shape of covering the entire surface of the anisotropic piezoelectric material on the upper surfaces of the anisotropic piezoelectric materials 2a, 2b, 2c of the stress distribution measuring tape. One piece of metal film 7 is adhered. Further, in order to connect the ground terminal of the surface electrometer to the metal film 7, the metal film 7 has a structure in which a part of the metal film 7 protrudes outside the support tape 1. In adhering to the structure, as shown in FIG. 3B, the metal film 7 is placed on the surface of the structural member so that the mark 6 of the anisotropic piezoelectric material marked on the support tape 1 can be seen. Adhesive 4 is attached to the surface.

FIG. 4 is a diagram showing an embodiment of a stress distribution measuring tape in which anisotropic piezoelectric materials 2a, 2b, 2c are arranged in two rows. One of the anisotropic piezoelectric material columns 2a, 2
b, 2c and another row of anisotropic piezoelectric materials 12a, 12
By arranging b and 12c in a staggered manner, a set of three anisotropic piezoelectric materials whose anisotropic principal axes are oriented in the directions of 0 °, 45 ° and 90 ° can be selected in a triangular shape. .
The stress distribution on the plane can be measured by using a stress distribution measuring tape in which the rows of the piezoelectric material are further increased to 3 rows and 4 rows.

FIG. 5 shows elongated anisotropic piezoelectric material strips 22a, 2 cut so that the principal axes of the anisotropy are oriented at 0, 45, and 90 degrees with respect to the longitudinal direction of the support tape 1.
It is a figure which shows one Example of the stress distribution measuring tape which adhered 2b and 22c so that it might become vertical stripe shape along the longitudinal direction of the support body tape 1. In this stress distribution measuring tape, the anisotropic piezoelectric material is continuously adhered in the length direction of the support tape, so that the strips 22a, 22b of the anisotropic piezoelectric material are located at arbitrary positions in the length direction of the support tape. , 22c, it is possible to obtain a continuous stress distribution in the length direction of the support tape by measuring the surface potentials at three points.

When a stress distribution measuring tape in which two kinds of anisotropic piezoelectric materials whose anisotropy principal axis is 0 degree and 90 degrees with respect to the length direction of the support tape is adhered is used, two directions of the surface of the member are used. The axial stresses σ _X and σ _Y can be measured.

FIG. 6 is a diagram for explaining a method of measuring the surface potential of a piezoelectric material using a vibration capacitance type distance compensation type surface electrometer 80. When the structure is a conductive material, the ground terminal 82, which serves as the reference potential of the surface electrometer, is connected to the surface of the structure. When the structure is made of a non-conductive material, the ground terminal 82, which becomes the reference potential, is connected to the metal film 7 of the stress distribution measuring tape.

Next, the vibrating electrode of the measuring probe 81 connected to the main body of the surface electrometer 80 is brought close to the anisotropic piezoelectric material to measure the surface potential. The non-contact type of vibration capacitance type and distance compensation type is used. The surface electrometer of the method is a method of canceling the influence of the electrostatic capacitance between the vibrating electrode and the surface of the piezoelectric material to measure by controlling the casing potential of the measuring probe 81. The surface potential can be measured even if there is a support tape 1 made of an insulating material in between. If the measurement probe 81 is held in hand and moved on the support tape 1, the surface potential can be sequentially measured at a plurality of points, but it is difficult to quickly measure the surface potential at a large number of points due to camera shake or the like. Is.

FIG. 7 is a diagram showing one embodiment of a method for measuring the surface potential by attaching the measuring probe 81 to the holder 50 and moving the holder 50 so as to slide on the upper surface of the support tape 1. When the holder 50 is pushed by hand, or when the holder 50 is moved by attaching wheels to the holder 50,
The surface potential can be measured quickly and accurately as compared with the case where the measurement probe 81 is directly held in the hand for measurement. Further, the holder 50 itself may be provided with a self-moving means and a function of adhering to the structure. Further, for example, if a surface electrometer having three channels is used as the surface electrometer, and three measuring probes are attached to the holder 50, the surface potentials of the three anisotropic piezoelectric materials are simultaneously measured. Will be possible.

FIG. 8 is a diagram showing an embodiment of a method for measuring the surface potential without bringing the measuring probe 81 itself close to the stress distribution measuring tape. The metal plate 57a is attached to the holder 5
No. 0, the holder 50 is placed on the upper surface of the support tape to hold the position of the metal plate 57a, and electric wiring is connected to the metal plate 57a so that another place placed away from the stress measurement position can be used. One end is connected to the metal plate 57b. Next, the measurement probe 81 of the surface electrometer is brought close to the metal plate 57b to fix the distance from the metal plate 57b. The circuit of this stress measuring method is the metal plate 57 placed on the surface of the piezoelectric material and the support.
The electrostatic capacitance formed by a and the electrostatic capacitance formed by the metal plate 57b placed in front of the measurement probe and the vibration electrode at the probe tip are connected in series. In the meter, the voltage of the probe casing is changed to cancel the influence of the electrostatic capacitance and the measurement is performed, so that the surface potential can be measured.

The stress distribution measuring tape of the present invention is shown in FIG.
, The anisotropic orientations are 0 degree, 45 degree and 90 degree.
As the stress measuring tape in which three anisotropic piezoelectric materials 2a, 2b, and 2c, which are changed in degrees, are adhered or adhered to the support tape 1, it can be used for stress measurement at one place as in the case of the triaxial strain gauge. it can.

[0031]

When the stress distribution measuring tape of the present invention is used, a large number of anisotropic piezoelectric materials serving as strain sensing portions can be easily and accurately adhered to structural members. Further, the stress distribution can be measured at high speed by attaching a measuring probe of a surface electrometer or a metal plate to the holder and moving the holder on the upper surface of the anisotropic piezoelectric material. In addition, various types of development are possible, such as a measuring method in which the holder itself has a self-moving means and a function of adhering to the structure, and a measuring method in which the holder is attached to the arm tip of the structure inspection manipulator to move the structure surface. Is.

[Brief description of drawings]

FIG. 1 is a view showing an example of a stress distribution measuring tape of the present invention.

FIG. 2 is a diagram showing an example of a stress distribution measuring tape in which an anisotropic piezoelectric material is attached to a support tape with a peelable adhesive.

FIG. 3 is a diagram showing an example of a stress distribution measuring tape applied to a non-conductive structure.

FIG. 4 is a diagram showing an arrangement example of anisotropic piezoelectric materials in a stress distribution measuring tape.

FIG. 5 is a diagram showing an example of a stress distribution measuring tape on which strips of anisotropic piezoelectric material are arranged.

FIG. 6 is a diagram showing a method of measuring the surface potential of a piezoelectric material using a surface electrometer.

FIG. 7 is a method of measuring a surface potential by attaching a measurement probe to a holder.

FIG. 8 is a diagram showing a method of performing stress distribution measurement without bringing the measurement probe itself close to the anisotropic piezoelectric material.

FIG. 9 is a diagram of a stress measuring tape in which three piezoelectric materials are attached while changing the anisotropic direction.

[Explanation of symbols]

1 support tape 2a, 2b, 2c Anisotropic piezoelectric material 12a, 12b, 12c Anisotropic piezoelectric material 22a, 22b, 22c Strips of anisotropic piezoelectric material 3 adhesive 4 adhesive 5 Adhesive 6 Marks indicating the shape and anisotropy of the piezoelectric material 7 Metal film 50 holder 57a, 57b Metal plate 80 surface electrometer 81 Measuring probe 82 Ground terminal

Claims (5)

[Claims] 1. A stress distribution measuring tape in which piezoelectric materials as strain sensing portions are regularly arranged and adhered to one surface of a support tape, the support tape being made of an insulating material, and the support tape being provided on one surface of the support tape. A plurality of anisotropic piezoelectric materials adhered side by side with their anisotropy changed in at least two directions, and anisotropy marked on the surface of the support tape on which the anisotropic piezoelectric material is not adhered A stress distribution measuring tape comprising a shape of a piezoelectric material and a mark indicating an anisotropic direction, wherein the stress distribution measuring tape is adhered to a surface of a structural member so that the mark of the anisotropic piezoelectric material can be seen. . 2. A stress distribution measuring tape in which piezoelectric materials as strain sensing portions are regularly arranged on one surface of a support tape and adhered with a peelable adhesive, the support tape being transparent, and the support tape. Anisotropy marked on the contact surface between a plurality of anisotropic piezoelectric materials adhered by arranging one surface of the anisotropic piezoelectric material in different directions in at least two directions. A mark indicating the anisotropic direction of the piezoelectric material, the stress distribution measuring tape being adhered to the surface of the structural member so that the mark of the anisotropic piezoelectric material can be seen, A stress distribution measuring tape, characterized in that the pressure sensitive adhesive between the materials is peeled off and the support tape is removed to expose the surface of the anisotropic piezoelectric material. 3. The stress distribution measuring tape according to claim 1, wherein the surface of the anisotropic piezoelectric material attached to one surface of the support tape further comprises all of the anisotropic piezoelectric material. A stress distribution measuring tape characterized in that a piece of metal film is adhered in such a shape that the surface is covered and a part of the support tape protrudes outside the support tape. 4. The stress measurement using the stress distribution measuring tape according to claim 1, wherein a vibrating capacitance type distance compensation type surface electrometer is used to measure the surface potential of the anisotropic piezoelectric material. The measurement probe of the surface electrometer is attached to the holder, the holder is placed on the upper surface of the anisotropic piezoelectric material adhered to the structural member to hold the position of the measurement probe, and the holder is the anisotropic piezoelectric material. A stress distribution measuring method, characterized in that the surface potential is measured by moving on the upper surface of the. 5. The stress measurement using the stress distribution measuring tape according to claim 1, wherein a holder having a metal plate 57a attached to the bottom is placed on the upper surface of the anisotropic piezoelectric material and the position of the metal plate 57a is set. The metal plate 57a was connected to an electric wire and one end was connected to another metal plate 57b placed away from the stress measurement position.
7b, a measuring probe of a surface electrometer is brought close to the metal plate 57b to fix the distance, and the holder is moved on the upper surface of the anisotropic piezoelectric material to measure the surface potential. Method of measuring stress distribution.