JPH07316518A - Adhesive member for forming adhesive layer capable of detecting internal defect - Google Patents

Abstract

PURPOSE:To provide an adhesive member for forming an adhesive layer capable of detecting internal defect in high sensitivity, composed of an uncured adhesive main body and a specific soft magnet embedded in the main body, by precisely measuring stress of soft magnet in a non-destructive state and readily detecting the internal defect. CONSTITUTION:This adhesive member 1 is used for forming an adhesive layer B bonding either member 41 to be bonded to the other member 42 to be bonded and capable of detecting internal defect by utilizing stress-magnetic characteristics of soft magnet. The adhesive member 1 is composed of a main body 2 comprising an uncured adhesive agent and plural soft magnets 3 embedded in the main body 2 and constrained in a state in which outer force is applied after curing of the main body 2. Furthermore, preferably, the soft magnet 3 is fibrous and arranged at definite intervals in the main body 2 or composed of an amorphous metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive member for forming an adhesive layer capable of detecting internal defects, in particular, one member to be adhered and the other member to be adhered are bonded to each other, and the stress-magnetic characteristics of a soft magnetic material are measured. The present invention relates to an adhesive member for forming an adhesive layer that can detect internal defects by utilizing the adhesive member.

[0002]

2. Description of the Related Art Conventionally, JI has been used as a method for evaluating an adhesive layer.
A performance test method according to the general rule of weather resistance test method as defined in SK-6860, and a nondestructive inspection method such as an ultrasonic flaw detection method and an X-ray method are known.

[0003]

However, it is very difficult to evaluate the adhesive layer between both members to be adhered because the performance test method is a method applied only to a test piece,
On the other hand, although the non-destructive inspection method can obtain a certain degree of evaluation when applied to a test piece, the adhesive layer as described above is not suitable because there are many restrictions on its shape, size, and the like.

In view of the above, it is an object of the present invention to provide an adhesive member capable of forming an adhesive layer capable of easily detecting an internal defect in a non-destructive state in various adherend members. To do.

[0005]

According to the present invention, one member to be bonded and the other member to be bonded are bonded to each other, and the internal defect can be detected by utilizing the stress-magnetic property of the soft magnetic material. An adhesive member for forming an adhesive layer, comprising a main body made of an uncured adhesive, and a plurality of the soft members embedded in the main body and constrained to an external force after the main body is cured. It is characterized by being composed of a magnetic material.

[0006]

When one of the adhered members and the other adhered member are adhered to each other using the adhesive member, a plurality of soft magnetic bodies are embedded in the adhesive layer with a predetermined stress.
The stress of the soft magnetic material can be accurately measured from the surface side of either one of the adherends by utilizing the stress-magnetic characteristics.

On the other hand, when internal defects such as cracks occur in the hardened main body of the adhesive layer, the binding force to the soft magnetic material,
Therefore, since the external force initially applied is reduced, the stress of the soft magnetic material is also reduced accordingly, whereby the internal defect of the adhesive layer can be easily detected in a non-destructive state.

Immediately after the two adhered members are adhered, the stress of the soft magnetic material is detected along the surface of one of the adhered members, and if there is an abnormal stress value at that time, that part is detected. Are considered to be defective adhesion points. In this way, the adhesive member, whether the adhesive layer formed from it is sound,
It is also used to judge whether it is unhealthy.

For example, when the main body is made of an uncured thermosetting synthetic resin adhesive and the thickness thereof is extremely thin, and both members to be adhered have a coefficient of thermal expansion different from that of the soft magnetic material, the soft magnetic material is applied to the soft magnetic material. The application of external force is easily realized by the difference in the coefficient of thermal expansion between the soft magnetic material and the members to be adhered when the main body is heated and hardened, but means for hardening the main body while applying tension to the soft magnetic material is used. May be adopted.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2, an adhesive member 1 for forming an adhesive layer capable of detecting an internal defect is a main body 2 made of an uncured adhesive, which has a rectangular shape and is in the form of a film having a uniform thickness. It is composed of a plurality of soft magnetic bodies 3 embedded inside.

A thermosetting synthetic resin adhesive is mainly used as an adhesive constituting the main body 2. The thermosetting synthetic resin adhesive is a phenol resin adhesive from the viewpoint that it can be easily formed into a film. Agents, epoxy resin adhesives, phenol epoxy resin adhesives, etc. However, it is also possible to use a thermoplastic synthetic resin adhesive.

The soft magnetic material 3 has a fibrous shape and is made of an amorphous metal in this embodiment. The plurality of fibrous soft magnetic bodies 3 are arranged in parallel with the longitudinal direction a of the main body 2 at a constant pitch b.

The thickness c of the adhesive member 1 is 0.03 mm≤c≤
1.0 mm is suitable, and the diameter d of the fibrous soft magnetic material 3 is
Is preferably 30 μm ≦ d ≦ 200 μm. Based on these points, the pitch b of the fibrous soft magnetic material 3 is set to 2d ≦ b ≦ 10d in relation to the diameter d thereof.

When the pitch b is set in this way, the main body 2
Is sufficient, and thus the amount of adhesive is appropriate, sufficient adhesive strength can be obtained, and the distribution state of the fibrous soft magnetic material 3 is appropriate, so that its stress detection sensitivity is good.
However, when b <2d, the volume fraction Vf of the fibrous soft magnetic material 3 in the adhesive layer is Vf≈40% because of the relationship with the thickness c of the adhesive member 1, resulting in insufficient adhesive strength. Further, the fibrous soft magnetic bodies 3 are easily entangled with each other during the bonding work, and it is difficult to make the thickness of the bonding layer uniform.
On the other hand, when b> 10d, the distribution state of the fibrous soft magnetic material 3 becomes sparse, and the stress detection sensitivity thereof decreases.

Table 1 shows dimensions and the like of specific examples of the adhesive member 1. In Table 1, the volume fraction V of the fibrous soft magnetic material 3
f shows the value in the adhesive member 1.

[0016]

[Table 1]As shown in FIG. 3, the same structure and the same size of the members to be adhered
Two FRP plates of the method (length g: 155 mm, width h: 25 m
m, thickness k: 1.6 mm, coefficient of thermal expansion: 3.5 × 10 ^-6/
℃) 4₁, 4₂Both FRP plates 4 for bonding₁, 4
₂Of the entire adhesive member 1 between each one end of the
Both FRP plates 4₁, 4₂Aligned with the longitudinal direction m of the
Then, the adhesive member 1 was heated at 180 ° C. for 1 hour, and 3.
It is cured under the condition of 2 atm. As a result, the adhesive layer B is shaped
Both FRP plates 4 are formed through the adhesive layer B.₁, 4₂But
To be glued. Adhesion allowance at this time is 10 cm²Is.

In this case, the coefficient of thermal expansion of the fibrous soft magnetic material 3 is 7.3 × 10 ^-6 / ° C., while both FRP plates 4 ₁ , 4
_Since that of No. ₂ is 3.5 × 10 ⁻⁶ / ° C., the fibrous soft magnetic body 3 is restrained in a state in which a tensile load is applied after the heat curing of the main body 2, and thus at room temperature after the formation of the adhesive layer B. .

When the stress of the fibrous soft magnetic material 3 in the adhesive layer B is measured, an alternating current exceeding the coercive force of the soft magnetic material 3 is applied to the fibrous soft magnetic material 3 to be measured by using an exciting coil. By applying a magnetic field, the fibrous soft magnetic material 3 is applied to the detection coil.
An AC electromotive force is induced via the, and in the waveform of the AC electromotive force, it is calculated from the effective value of one or more harmonic components including the stress information of the fibrous soft magnetic body 3 and the effective value of the fundamental wave component. A method in which the strain rate K (hereinafter, simply referred to as the strain rate K) is used as the measurement amount is adopted.

In this way, the strain rate K is used as the measured quantity,
That is, if the harmonic component is captured as an amount, the stress of the fibrous soft magnetic material 3 can be measured with high accuracy, and thus the minute stress change can be accurately detected.

Next, the principle of the stress measuring method will be described.

In FIG. 4, the fibrous soft magnetic material 3 is inserted into the exciting coil 6 and the detection coil 7 connected to the oscillator 5, and a predetermined tensile load is applied to the soft magnetic material 3.

When the oscillator 5 is actuated and the exciting coil 6 applies to the fibrous soft magnetic material 3 an alternating magnetic field H that does not include a direct current magnetic field component and exceeds the coercive force Hc of the soft magnetic material 3, the detecting coil 7 is applied to the detecting coil 7. AC positive / negative symmetrical AC electromotive force V ₂ is induced through the fibrous soft magnetic material 3.

Here, the AC electromotive force V ₂ is, as shown in [Equation 1],

[0024]

[Equation 1] Is represented. However, φ is magnetic flux, t is time, α is a coefficient, I is the strength of magnetization of the fibrous soft magnetic material 3, and H is the strength of the AC magnetic field.

The alternating magnetic field H is, as shown in [Equation 2],

[0026]

[Equation 2] Is represented. However, Hm is the amplitude of the alternating magnetic field, f ₀ is the frequency, and ψ ₀ is the phase angle.

Here, when [Equation 2] is differentiated with respect to time t, as shown in [Equation 3],

[0028]

[Equation 3] Becomes

Therefore, the dH / dt of [Equation 3] is changed to [Equation 1]
Substituting into, the AC electromotive force V ₂ is, as shown in [Equation 4],

[0030]

[Equation 4] Is represented.

In the magnetization process of the fibrous soft magnetic material 3,
Since the magnetization curve as shown by the line n ₁ in FIG. 5 is obtained,
[Equation 4] uses the instantaneous magnetic susceptibility dI (H) / dH as shown in [Equation 5],

[0032]

[Equation 5] Is represented.

This AC electromotive force V ₂ contains a harmonic component because its waveform is a distorted wave as shown in FIG. In this case, since the AC magnetic field H does not include the DC magnetic field component as described above, the harmonic component of the AC electromotive force V ₂ is, in principle, composed of only odd harmonic components and does not include even harmonic components. Absent.

The harmonic component is the instantaneous magnetic susceptibility dI (H) /
It depends on dH, and its instantaneous magnetic susceptibility dI (H) / dH depends on the stress of the fibrous soft magnetic material 3. Therefore, the harmonic component includes the stress information of the fibrous soft magnetic body 3.

Therefore, the waveform of the AC electromotive force V ₂ is frequency-analyzed using a spectrum analyzer and divided into a fundamental wave component and a harmonic wave component, and the strain rate K is determined by the stress measurement amount of the fibrous soft magnetic material 3 as described above. And

The distortion factor K is the effective value of the third, fifth, seventh and ninth harmonic components when the harmonic components are the third, fifth, seventh and ninth harmonic components, for example. Let E ₃ , E ₅ , E ₇ , and E ₉ be the respective values and the effective value of the fundamental wave component be E ₁ , as shown in [Equation 6],

[0037]

[Equation 6] Is represented. A calculator is used to calculate the distortion rate K.

On the other hand, the magnetic characteristics of the fibrous soft magnetic material 3 are as follows.
Change with the change of the state where the soft magnetic body 3 of
That is, the instantaneous magnetic susceptibility dI (H) of the fibrous soft magnetic material 3
/ DH is because the tensile load on the soft magnetic material 3 is large.
When it changes to a small value, the line n in FIG. ₃→ line n₂→ line n₁As
Changes from large to small, and as a result, the periodic function V
₂Since (t) changes, the effective value of the harmonic component also changes.
It

Therefore, by using the strain rate K as the measurement amount as described above, it is possible to accurately measure the minute stress change of the fibrous soft magnetic material 3 as shown in FIG.

Specific examples will be described below.

As the two FRP plates 4 ₁ and 4 ₂ , the reinforcing fibrous body is composed of 8 cloths made of carbon fibers having a diameter of 6 μm, and the orientation of the carbon fibers of both adjacent cloths is 45.
There was prepared a laminated body in which the layers were laminated so as to be changed, and the matrix of which was an epoxy resin. Both FRP plates 4 _1, 4 ₂ dimensions and coefficient of thermal expansion is the same as above. These FRP plates 4 ₁ and 4 ₂ were adhered using the adhesive member 1 in the same manner as described above to form an adhesive layer B as shown in FIG. In this case, the fibrous soft magnetic body 3 is constrained in a state where a tensile load is applied as in the above.

In FIG. 8, the stress measuring device 8 is constructed as follows. That is, the ferrite core 9 is formed in a U shape by the pair of leg portions 9a and the connecting portion 9b that connects one ends of the both leg portions 9a. The detection coil 7 is attached to the connecting portion 9b.
The winding is wound 0 turns / 15 mm, and the exciting coil 6 is wound around the detection coil 7 at 140 turns / 15 mm. The exciting coil 6 is connected to the oscillator 5. Further, the detection coil 7 is connected to the spectrum analyzer 10, and the spectrum analyzer 10 is connected to the calculator 11.

First, stress measurement was performed on the fibrous soft magnetic material 3 of the adhesive layer B. In measuring the stress of the soft magnetic body 3, the end faces of both legs 9a of the core 9 are applied to the surface of _one FRP plate 41, and the oscillator 5 is set to a sine wave containing no DC magnetic field component, a frequency of 1 kHz, and a peak-to-peak interval. The magnetic field, that is, the peak and the peak-to-peak voltage in one cycle, was operated under an oscillation condition of 30 V _PP to apply an AC magnetic field H to the exciting coil 6 that exceeds the coercive force Hc of the fibrous soft magnetic body 3. As a result, a magnetic path is formed between the core 9 and the soft magnetic body 3, and the detection coil 7
AC electromotive force V ₂ is induced in the. This AC electromotive force V ₂ is input to the spectrum analyzer 10, and then the calculator 11
More distortion rate K, that is, as shown in [Equation 7],

[0044]

[Equation 7] Was output, and this was used as the stress measurement amount of the fibrous soft magnetic body 3. When the soft magnetic body 3 is magnetized as described above, the soft magnetic body 3 expands, that is, a magnetostriction phenomenon occurs.
The magnetostrictive vibration phenomenon under an alternating magnetic field is suppressed by the hardened main body 2.

Next, the outer end portions of both FRP plates 4 ₁ and 4 ₂ are clamped by a chuck, and a tensile-tensile fatigue test is performed on the adhesive layer B until the adhesive layer B breaks, and a predetermined stress is applied during that time. The stress of the fibrous soft magnetic material 3 was measured for each cycle repetition number. The fatigue test conditions are a distance between both chucks of 150 mm, a minimum tensile load of 0.14 tons, a maximum tensile load of 1.4 tons, and a repetition frequency of 20 Hz.

Then, the relationship between the number of stress cycle repetitions and the strain rate K was determined, and the results shown in FIG. 9 were obtained. The strain rate K decreases due to the fact that the main body 2 plastically deforms immediately after the start of the test, but after that, it is constant up to the stress cycle number of 2 × 10 ³ times, whereby the adhesive layer B does not exist. It turns out to be damage. When the number of stress cycle repetitions exceeds 2 × 10 ³ , the strain rate K starts to decrease. This is because damage occurred in the adhesive layer B,
This is because the restraining force on the fibrous soft magnetic material 3 is reduced, the stress of the soft magnetic material 3 is reduced due to that, and the suppression of the magnetostrictive vibration phenomenon under an alternating magnetic field is relaxed. When a cross section of the adhesive layer B was observed with a microscope at a stress cycle number of 5 × 10 ³ times, the occurrence of cracks was confirmed.

FIG. 10 shows another tensile-tensile fatigue test example. In this test example, the FRP of either one of the above
Plate 4 ₁ and the steel plate (JIS S45C, length g: 155mm,
Width h: 25 mm, thickness k: 4 mm, coefficient of thermal expansion 11.2 × 10
^-6 / ° C.) and the adhesive member 1 were adhered in the same manner as described above. In this case, the thermal expansion coefficient of the steel sheet due to larger than that of the FRP plate 4 _1, fibrous soft magnetic body 3 is restrained in a state of being applied a compressive load.

The test conditions are the same as those of the test example except that the minimum tensile load is set to 0.06 ton and the maximum tensile load is set to 0.55 ton. The core 9 of the stress measuring device 8 from the viewpoint of improving sensitivity is disposed FRP plate 4 ₁ side.

In FIG. 10, the strain rate K slightly increases because the main body 2 undergoes plastic deformation immediately after the start of the test, but after that, the stress cycle repetition number 6
It is constant up to × 10 ³ times, which shows that the adhesive layer B is undamaged. And the stress cycle number is 6
When it exceeds × 10 ³ times, the strain rate K starts to increase. This is because the adhesive layer is damaged, so that the restraining force on the fibrous soft magnetic material 3 is reduced, which causes the stress of the soft magnetic material 3 to be reduced and also suppresses the magnetostrictive vibration phenomenon under an alternating magnetic field. Is due to the relaxation. When the cross section of the adhesive layer B was observed with a microscope at a stress cycle number of 10 ⁴ times, cracks were observed between the fibrous soft magnetic body 3 and the cured main body 2.

The adhesive member 1 may contain glass fiber or the like for the purpose of strengthening it. Both members to be adhered may be made of metal, and the material of these members may be wood, ceramics, or the like.

The stress measurement amount of the soft magnetic material is not limited to the strain rate K, but in the waveform of the AC electromotive force, the effective value of one or more harmonic components including the stress information of the soft magnetic material, the peak-to-peak voltage, A peak value or the like can be used.

[0052]

According to the present invention, with the above-mentioned structure, the stress of the soft magnetic material is accurately measured in the non-destructive state to form the adhesive layer capable of detecting the internal defect with high sensitivity. It is possible to provide an adhesive member that can be manufactured.
Further, since the stress measurement of the soft magnetic material may be performed from the surface side of one of the adherend members, the internal defect of the adhesive layer can be easily detected.

[Brief description of drawings]

FIG. 1 is a perspective view of an adhesive member.

2 is an enlarged sectional view taken along line 2-2 of FIG.

FIG. 3 is a perspective view showing a state in which two FRP plates are bonded via an adhesive layer.

FIG. 4 is a principle diagram of a stress measuring method.

FIG. 5 is a magnetization curve diagram of a soft magnetic material.

FIG. 6 is a waveform diagram of AC electromotive force V ₂ .

FIG. 7 is a graph showing the relationship between stress and strain rate K.

FIG. 8 is a schematic view of a stress measuring device.

FIG. 9 is a graph showing an example of the relationship between the number of stress cycle repetitions and the strain rate.

FIG. 10 is a graph showing another example of the relationship between the number of stress cycle repetitions and the strain rate.

[Explanation of symbols]

1 Adhesive member 2 Main body 3 Soft magnetic material 4 ₁ , 4 ₂ FRP plate (adhered member) B Adhesive layer

Claims (3)

[Claims] 1. An internal defect is detected by adhering _one adhered member (4 ₁ ) and the other adhered member (4 ₂ ) and utilizing the stress-magnetic characteristics of the soft magnetic material (3). An adhesive member for forming an adhesive layer (B) thus obtained, comprising a main body (2) made of an uncured adhesive, and a main body (2) embedded in the main body (2) and after curing the main body (2). Is an adhesive member for forming an adhesive layer capable of detecting an internal defect, which is composed of a plurality of the soft magnetic bodies (3) which are constrained to be applied with an external force. 2. The internal according to claim 1, wherein the soft magnetic material (3) has a fibrous shape, and the fibrous soft magnetic materials (3) are juxtaposed at regular intervals in the main body (2). An adhesive member for forming an adhesive layer capable of detecting defects. 3. The adhesive member for forming an adhesive layer according to claim 1, wherein the soft magnetic material (3) is made of an amorphous metal.