JP7286973B2 - Resin material deterioration evaluation method and deterioration evaluation device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a deterioration evaluation method and a deterioration evaluation apparatus capable of non-destructively evaluating deterioration of a resin material in the depth direction.

The following Patent Documents 1 and 2 describe methods for evaluating deterioration of resin materials. In Patent Document 1, the relationship between the surface characteristics of the resin material and the degree of deterioration is stored in advance as master data. Then, the degree of deterioration of the resin material is evaluated by performing a comparison operation with the master data.

Further, in Patent Document 2, microparticles are projected onto a resin surface at high speed by an MSE (Micro Slurry Jet Erosion) method to cause abrasion. Then, the degree of deterioration is evaluated from the rate of progress of wear.

JP-A-10-74628 JP 2016-127279 A

However, in Patent Document 1, master data is required for each resin material, and preparation for deterioration evaluation requires cost and time. In addition, if the resin material is changed, the master data must be changed each time, and various resin materials cannot be easily evaluated.

Moreover, in Patent Document 2, it is necessary to damage the resin surface by projecting fine particles onto the resin surface, and non-destructive deterioration evaluation cannot be performed.

The present invention has been made in view of such a point, and a deterioration evaluation method and a deterioration evaluation apparatus for a resin material that can evaluate deterioration in the depth direction of a resin material in a simple and non-destructive manner. One of the purposes is to provide

A deterioration evaluation method for a resin material according to one embodiment of the present invention is a deterioration evaluation method for a resin material having a deteriorated layer formed on the surface thereof by curing, wherein a plurality of ultrasonic signals having different frequencies are propagated through the resin material. a step of acquiring propagation characteristics of each ultrasonic signal, and a step of evaluating deterioration in the depth direction of the resin material based on the difference in the propagation characteristics , wherein the plurality of ultrasonic waves having different frequencies The signal is characterized by including at least an ultrasonic signal with a frequency of 1.0 MHz or less and an ultrasonic signal with a frequency of 2.5 MHz or more .

An apparatus for evaluating deterioration of a resin material according to one aspect of the present invention is an apparatus for evaluating deterioration of a resin material having a deteriorated layer formed on the surface thereof due to curing, is installed on the surface of the resin material, and has a frequency of at least 1.0 MHz or less. a propagation device for propagating a plurality of said ultrasonic signals including an ultrasonic signal and an ultrasonic signal with a frequency of 2.5 MHz or more in said resin material; and a propagation characteristic of each ultrasonic signal obtained from said propagation device and an evaluation unit for evaluating deterioration of the resin material in the depth direction based on the difference in propagation characteristics.

According to the deterioration evaluation method and the deterioration evaluation apparatus of the present invention, it is possible to easily and non-destructively evaluate deterioration in the depth direction of a resin material whose initial characteristics are unknown.

1 is a schematic diagram of a deterioration evaluation device in an embodiment of the present invention; FIG. FIG. 2 is a conceptual diagram of a transmission signal and a reception signal of a first signal S1 (low frequency signal); FIG. 4 is a conceptual diagram of a transmission signal and a reception signal of a second signal S2 (high frequency signal); 4 is a flowchart of a deterioration evaluation method according to an embodiment of the present invention; It is a graph which shows the relationship between the frequency and propagation speed in two-point evaluation. It is a graph which shows the relationship between a frequency and a propagation speed in 5-point evaluation.

DETAILED DESCRIPTION OF THE INVENTION A deterioration evaluation apparatus and a deterioration evaluation method according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The deterioration evaluation apparatus and deterioration evaluation method according to the present invention are not limited to the following embodiments, and various modifications can be made within the scope of the invention.

First, an overview of deterioration evaluation of a resin material in this embodiment will be described. As described in the above patent documents, in the past, master data is required for each resin material to be measured, or non-destructive evaluation cannot be performed. could not evaluate the deterioration of

As a result of analyzing the deterioration phenomenon of the resin material, the present inventor focused on the fact that deterioration occurs only in the vicinity of the surface layer of the resin material, and the inside of the resin material is in an undegraded state. As a result of repeated experiments, it was also found that the deteriorated layer located on the surface is hardened and the wave propagation velocity in the medium is faster than that of the undegraded layer.

Based on the characteristics of such deterioration phenomena, we have found a method that enables non-destructive evaluation of deterioration of resin materials whose initial characteristics are unknown. That is, in the present embodiment, a plurality of signals with different frequencies are propagated in a resin material, the propagation characteristics of each signal are obtained, and the deterioration evaluation is performed from the difference in these propagation characteristics. There is

First, referring to FIG. 1, a schematic configuration of a deterioration evaluation device 1 according to this embodiment will be described. FIG. 1 is a schematic diagram of a deterioration evaluation device 1 according to this embodiment.

As shown in FIG. 1, the deterioration evaluation apparatus 1 includes a propagation device 3 installed on the surface 11a of a resin material 11, which is an object to be inspected, a calculation unit 4, an evaluation unit 5, and a storage unit 6. configured as

The propagation device 3 includes a transmitting probe 3a and a receiving probe 3b. The probes 3a and 3b shown in FIG. 1 are angle probes, but they may be vertical probes or other probes. Also, an oblique angle probe and a vertical probe may be used in combination.

As shown in FIG. 1, a signal transmitted through the resin material 11 from the probe 3a propagates through the resin material 11 and is received by the probe 3b. In this embodiment, a plurality of signals with different frequencies are propagated through the resin material 11 . Here, for ease of explanation, the plurality of signals will be described as a first signal S1 with a lower frequency and a second signal S2 with a higher frequency than the first signal S1.

As shown in FIG. 1, the first signal S1 propagates deep in the resin material 11, and the second signal S2 propagates near the surface layer of the resin material 11. As shown in FIG.

The computation unit 4 computes the propagation speed and attenuation of each signal based on the transmission signal transmitted from the probe 3a and the reception signal received by the probe 3b.

FIG. 2 is a conceptual diagram of a transmission signal and a reception signal of the first signal S1 (low frequency signal). FIG. 3 is a conceptual diagram of a transmission signal and a reception signal of the second signal S2 (high frequency signal).

As shown in FIG. 2, the propagation time and attenuation of the first signal S1 are obtained based on the transmitted signal and the received signal of the first signal S1. Similarly, as shown in FIG. 3, the propagation time and attenuation of the second signal S2 are obtained based on the transmitted and received signals of the second signal S2.

Here, the distance L between the probes 3a and 3b shown in FIG. 1 is set to a predetermined distance. Therefore, the calculation unit 4 can calculate each propagation speed of the first signal S1 and the second signal S2 from the distance L and the propagation time.

The calculator 4 further calculates the difference between the first propagation velocity v1 of the first signal S1 and the second propagation velocity v2 of the second signal S2. The "difference in propagation speed" may be obtained as an absolute value or as a ratio. Similarly, the calculator 4 can obtain the difference in attenuation between the first signal S1 and the second signal S2.

The evaluation unit 5 evaluates deterioration of the resin material 11 in the depth direction based on, for example, the difference in propagation speed as the propagation characteristic obtained by the calculation unit 4 . As the deterioration permeates in the depth direction, the difference in propagation speed between the first signal S1 and the second signal S2 increases, making it possible to evaluate the deterioration level and the deterioration depth.

The storage unit 6 shown in FIG. 1 stores the propagation characteristics calculated by the calculation unit 4 and the deterioration evaluation information obtained by the evaluation unit 5 . In the storage unit 6, deterioration evaluation information and the like can be accumulated each time deterioration evaluation is performed. Such information can be used for evaluation of the degree of deterioration due to differences in use environment, relative evaluation for each product, future prediction of deterioration, and the like.

As shown in FIG. 1, a control unit 7 including a calculation unit 4, an evaluation unit 5, and a storage unit 6 is configured. The control unit 7 can include components other than the calculation unit 4 , the evaluation unit 5 , and the storage unit 6 .

The display device 8 displays deterioration evaluation information (for example, deterioration depth and deterioration level) diagnosed by the evaluation unit 5 . The display device 8 may be included as a component of the deterioration evaluation device 1 or may be configured separately from the deterioration evaluation device 1 . The deterioration evaluation device 1 and the display device 8 are connected by wire or wirelessly, and the deterioration evaluation information is transmitted from the deterioration evaluation device 1 to the display device 8 . The display device 8 is, for example, a personal computer, and can display the deterioration evaluation result of the resin material 11, which is the object to be inspected, on the screen of the personal computer.

The surface layer of the resin material 11, which is the object to be inspected, is degraded due to aging such as oxidation, and becomes a deteriorated layer 11b. The inside of the resin material 11 is an undegraded layer 11c. The deteriorated layer 11b is hardened compared to the undegraded layer 11c. It should be noted that there may or may not be a boundary between the deteriorated layer 11b and the undegraded layer 11c. is changing.

As shown in FIG. 1, the first signal S1, which is a low-frequency signal, mainly propagates through the undegraded layer 11c, and the second signal S2, which is a high-frequency signal, mainly propagates through the deteriorated layer 11b. Since the degraded layer 11b has a higher degree of hardening than the non-degraded layer 11c, there is a difference in propagation characteristics between the first signal S1 and the second signal S2. Therefore, even if the initial characteristics are unknown, it is possible to evaluate the deterioration of the resin material 11 in the depth direction based on the difference in the propagation characteristics. Hereinafter, the deterioration evaluation method of the resin material according to the present embodiment will be specifically described with reference to the flow chart of FIG.

Here, an epoxy resin, which is a typical cast insulating material, is used as the object to be inspected. The wave propagation velocity V in the medium is approximately 3000 m/s. This wave propagation velocity V does not change with frequency if the medium is the same. Therefore, in the initial state where the deteriorated layer 11b is not formed on the resin material 11, even if the first signal S1 and the second signal S2 having different frequencies are propagated, the wave propagation velocity V is substantially the same.

In step ST1 shown in FIG. 4, a first signal S1 as a low-frequency signal is transmitted from the probe 3a and received by the probe 3b. Note that the second signal S2 as a high-frequency signal may be transmitted/received first. In this embodiment, the frequency of the first signal S1 is preferably adjusted to 1.0 MHz or less, more preferably 0.5 MHz or less.

Here, the depth d to which the surface wave of frequency f propagates in the resin is about 1/4 of the wavelength λ. Therefore, with the wavelength λ=v/f, the propagation depth d=λ/4=v/f/4=750/f. Therefore, when the frequency is set to 1.0 MHz or less, the first signal S1 propagates inside the resin material 11 at a depth of 750 μm or more. Also, when the frequency is set to 0.5 MHz or less, the first signal S1 propagates inside the resin material 11 at a depth of 1500 μm or more.

Then, in step ST2 of FIG. 4, the first propagation velocity v1 of the first signal S1 is acquired. The first propagation velocity v1 of the first signal S1 is calculated by the calculation unit 4 shown in FIG. 1 based on the propagation time obtained from the transmitted signal and the received signal shown in FIG. can ask. Further, in this step ST2, the degree of attenuation of the first signal S1 shown in FIG. 2 can be obtained as the propagation characteristic in addition to the propagation velocity.

Next, in step ST3 of FIG. 4, a second signal S2 as a high frequency signal is transmitted from the probe 3a and received by the probe 3b.

According to the results of resin deterioration analysis, it is known that the maximum depth of the deteriorated layer 11b is about 100 μm. It should be noted that the maximum depth of the deteriorated layer 11b is substantially the same as long as the resin material is made of a polymer compound, regardless of the epoxy resin.

In this embodiment, the first signal S1 is mainly propagated through the undegraded layer 11c, and the second signal S2 is mainly propagated through the deteriorated layer 11b. As described above, by adjusting the frequency of the first signal S1 to 1.0 MHz or less, preferably 0.5 MHz or less, the first signal S1 can be generated at a depth of 750 μm or more, preferably 1500 μm or more. It propagates around the deteriorated layer 11c.

On the other hand, the second signal S2 is affected by the hardened deterioration layer 11b, and in order to cause a propagation speed difference between the first signal S1 and the second signal S2, the maximum depth of the deterioration layer 11b is three times or less. , 300 μm or less. Therefore, from f=750/d, it is preferable to adjust the frequency of the second signal S2 to 2.5 MHz or higher. The higher the frequency of the second signal S2, the higher the ratio of the deteriorated layer 11b to the signal propagation region, and the more pronounced the difference in propagation speed. It is even more preferable to have By setting the frequency to 5 MHz or more, the second signal S2 propagates through the resin material 11 to a depth of 150 μm or less, and by setting the frequency to 7.5 MHz or more, the second signal S2 propagates to a depth of 100 μm or less. It propagates through the resin material 11 . As described above, the maximum depth of the deteriorated layer 11b of the resin material 11 is about 100 μm. Propagate inside.

Then, in step ST4 of FIG. 4, the second propagation velocity v2 of the second signal S2 is acquired. The second propagation velocity v2 of the second signal S2 is calculated by the calculation unit 4 shown in FIG. 1 based on the propagation time obtained from the transmitted signal and the received signal shown in FIG. can ask. Further, in this step ST4, the degree of attenuation of the second signal S2 shown in FIG. 3 can be obtained as the propagation characteristic in addition to the propagation velocity.

In step ST5 of FIG. 4, the difference between the first propagation velocity v1 and the second propagation velocity v2 obtained in steps ST2 and ST4 is calculated by the calculator 4 shown in FIG. Here, as the difference in propagation velocity, for example, the absolute value of the first propagation velocity v1 - the second propagation velocity v2 may be obtained, or the ratio of the second propagation velocity v2 / the first propagation velocity v1 You can also ask for

Then, in step ST6 of FIG. 4, deterioration evaluation is performed by the evaluation unit 5 shown in FIG. 1 based on the propagation velocity difference obtained in step ST5.

An example of determination of deterioration evaluation in this embodiment will be described. As described in the above steps, the first signal S1, which is a low-frequency signal, and the second signal S2, which is a high-frequency signal, are used for evaluation. The description will be made separately for the case where evaluation is performed using point signals. The frequency of each signal is shown in Table 1 below.

As shown in Table 1, in the two-point evaluation, the frequency of the first signal S1 was set at 0.5 MHz and the frequency of the second signal S2 was set at 2.5 MHz.

Then, the first propagation velocity v1 of the first signal S1 and the second propagation velocity v2 of the second signal S2 were obtained, and the difference between the propagation velocities was calculated by the calculation unit 4 . FIG. 5 is a graph showing the relationship between frequency and propagation velocity in two-point evaluation. Here, the circle data and rhombus data shown in FIG. 5 are the results of evaluating different deterioration states in the depth direction of the resin material.

As shown in FIG. 5, in round data, the first propagation velocity v1 of the first signal S1 with a frequency of 0.5 MHz and the second propagation velocity v2 of the second signal S2 with a frequency of 2.5 MHz are almost the same. be. This is because the entire resin material 11 as an object to be inspected is in an undegraded state.

On the other hand, in the lozenge data shown in FIG. 5, the second propagation velocity v2 of the second signal S2 with a frequency of 2.5 MHz is greater than the first propagation velocity v1 of the first signal S1 with a frequency of 0.5 MHz. ing. This is because the deteriorated layer 11b is formed on the surface layer of the resin material 11 as the object to be inspected, and the second signal S2 propagates through at least a portion of the deteriorated layer 11b that is harder than the first signal S1. Assuming that the frequency of the second signal S2 is 2.5 MHz, when the resin material 11 has a deteriorated layer 11b with a thickness of about 100 μm, which is in the state of life, the second signal S2 is 1/3 of the deteriorated layer 11b. propagates around a depth of 300 μm.

The difference between the second propagation velocity v2 of the second signal S2 having a frequency of 2.5 MHz and the first propagation velocity v1 of the first signal S1 having a frequency of 0.5 MHz shown in FIG. At some point, the deteriorated layer 11b reaches a predetermined thickness or more, and is determined to be at an abnormal level. If it is determined to be at an abnormal level, it means that the life span is at or near the end of the life span, and the inspector can appropriately determine whether to replace the resin material 11 or the like.

In the two-point evaluation, when the deteriorated layer 11b reaches a predetermined thickness or more, it is possible to determine whether or not there is an abnormality. is preferable, for example, 5-point evaluation. Note that 5 points is an example and does not limit the number of evaluation points.

As shown in Table 1 above, in the 5-point evaluation, signals with frequencies of 0.5 MHz, 1.0 MHz, 2.5 MHz, 5.0 MHz, and 7.5 MHz were propagated through the resin material 11, Each propagation velocity was acquired. FIG. 6 is a graph showing the relationship between frequency and propagation velocity in 5-point evaluation. Here, the circle data, triangle data, square data, and rhombus data shown in FIG. 6 are the results of evaluating different states of deterioration of the resin material in the depth direction.

Low-frequency signals with frequencies of 0.5 MHz and 1.0 MHz propagate around depths of 1500 μm and 750 μm, respectively. Since the deteriorated layer 11b has a maximum thickness of about 100 μm, these low-frequency signals propagate inside the insulating layer, the majority of which is the undegraded layer 11c.

When the deteriorated layer 11b reaches about 100 μm and reaches the end of its service life, a high frequency signal with a frequency of 2.5 MHz propagates at a depth of 300 μm where the deteriorated layer 11b occupies ⅓. A high-frequency signal with a frequency of 5.0 MHz propagates through a position with a depth of 150 μm where the deteriorated layer 11b occupies ⅔. A high-frequency signal with a frequency of 7.5 MHz propagates through a depth of 100 μm, which is equivalent to the thickness of the deteriorated layer 11b.

The round data shown in FIG. 6 has almost the same propagation speed regardless of the frequency, and the entire resin material 11 as the object to be inspected is in an initial undegraded state. On the other hand, the thickness of the deteriorated layer 11b increases in the order of triangular data, square data, and rhombic data, and the change in propagation velocity increases in order.

With respect to the propagation speed of a low-frequency signal with a frequency of 0.5 MHz, which propagates at a position farthest from the deteriorated layer 11b, it is detected which frequency signal causes the propagation speed difference to exceed the judgment reference value D2. do. In the above description, the low frequency to be compared is 0.5 MHz, but 1.0 MHz may be used.

In the triangular data, only 7.5 Hz exceeds the criterion value D2. In this case, deterioration level 1 is determined. On the other hand, in square data, frequencies exceeding the criterion value D2 are 5.0 MHz and 7.5 MHz. In this case, deterioration level 2 is determined. Furthermore, in the rhombus data, frequencies exceeding the criterion value D2 are 2.5 MHz, 5.0 MHz, and 7.5 MHz. In this case, it is evaluated as deterioration level 3.

At deterioration level 3, for example, the thickness of the deteriorated layer 11b occupies two-thirds or more of the maximum thickness of 100 μm, and is a level at which replacement of the resin material 11 is recommended. Deterioration level 2 is, for example, when the degraded layer 11b reaches about 1/3 to 2/3 of the maximum thickness of 100 μm, and immediate replacement of the resin material 11 is not necessary, but it is a level that calls attention. Deterioration level 1 is, for example, a level in which the degraded layer 11b is about 1/3 or less of the maximum thickness of 100 μm, and is a level that can be safely used for the time being.

By increasing the number of evaluation points, it is possible to classify deterioration levels more finely and evaluate the depth of deterioration.

In the above description, the difference in propagation speed is compared with the criterion value D2 to evaluate the deterioration. stipulate. Alternatively, an approximate curve can be obtained from each evaluation point, and an inflection point can be obtained from the approximate curve. Then, it is possible to perform deterioration evaluation based on the frequency of the inflection point.

Alternatively, deterioration evaluation can be performed based on the difference in attenuation shown in FIGS. As for the method of evaluating deterioration, the degree of attenuation for each frequency is calculated in the same manner as in the case of using the difference in propagation speed described above, and the degree of deterioration and the depth of deterioration can be evaluated based on the difference in the degree of attenuation. .

In the deterioration evaluation method of the present embodiment, it is possible to non-destructively evaluate deterioration of a resin material whose initial characteristics are unknown. That is, in this embodiment, master data is not required for each resin material. At least, the first signal S1, which is a low-frequency signal, and the second signal S2, which is a high-frequency signal, are propagated through the resin material 11, and deterioration can be evaluated based on the obtained propagation characteristic difference.

At this time, it is preferable to adjust at least the frequency of the first signal S1 to 1.0 MHz or less and the frequency of the second signal to 2.5 MHz or more. Further, it is more preferable to adjust the frequency of the first signal S1 to 0.5 MHz or less. As a result, deterioration evaluation accuracy can be improved.

Further, in this embodiment, a difference in propagation speed or a difference in attenuation can be used as the difference in propagation characteristics, and deterioration evaluation accuracy can be improved with a simple calculation method.

Further, in this embodiment, deterioration evaluation can be performed using the deterioration evaluation apparatus 1 shown in FIG. The deterioration evaluation device 1 evaluates deterioration based on at least a propagation device 3 for propagating a plurality of signals having different frequencies through a resin material 11, a calculation unit 4 for calculating a difference in propagation characteristics, and a difference in propagation characteristics. All that is required is to have the evaluation unit 5 . By using the deterioration evaluation apparatus 1 of the present embodiment in this manner, deterioration evaluation can be easily performed even for a resin material whose initial state is unknown.

Although each embodiment of the present invention has been described, another embodiment of the present invention may be a combination of the above-described embodiments and modifications in whole or in part.

Moreover, the embodiments of the present invention are not limited to the above-described embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way due to advances in technology or another derived technology, that method may be used. Therefore, the claims cover all embodiments that can be included within the scope of the technical concept of the present invention.

For example, although the frequency of the first signal S1 is 0.5 MHz in FIG. 5, it can be set to 1.0 MHz or less, or a little higher in some cases. It is preferable to set the frequency to 0.5 MHz or less in order to improve the deterioration evaluation accuracy. does not propagate properly, it is necessary to raise the low frequency signal to a propagable frequency.

Further, for example, in the above-described embodiment, deterioration evaluation is performed for one resin material 11, but it is also possible to perform deterioration evaluation for a plurality of resin materials 11 and perform system management. For example, it is possible to store the degree of deterioration due to the difference in use environment and manage the replacement timing of each resin material 11 .

In this embodiment, a method of separately transmitting and receiving a plurality of signals with different frequencies is described. good.

As described above, according to the present invention, it is possible to evaluate the deterioration of a resin material without obtaining the characteristics of the initial state. Therefore, non-contact deterioration evaluation can be performed for a resin material whose initial state is unknown, for example, a resin casting used in high-voltage equipment.

1: Degradation evaluation device 3: Propagation device 3a, 3b: Probe 4: Calculation unit 5: Evaluation unit 6: Storage unit 7: Control unit 8: Display device 11: Resin material 11a: Surface 11b: Degraded layer 11c: Not yet Degraded layers D1, D2: Criterion value L: Distance

Claims (4)

A deterioration evaluation method for a resin material having a deteriorated layer formed on the surface due to curing,
a step of propagating a plurality of ultrasonic signals having different frequencies through a resin material to acquire the propagation characteristics of each ultrasonic signal;
evaluating the deterioration of the resin material in the depth direction based on the difference in the propagation characteristics;
has
The deterioration evaluation method of a resin material, wherein the plurality of ultrasonic signals having different frequencies include at least an ultrasonic signal having a frequency of 1.0 MHz or less and an ultrasonic signal having a frequency of 2.5 MHz or more. 2. The deterioration evaluation method of a resin material according to claim 1, wherein the propagation speed of each ultrasonic signal is acquired as the propagation characteristic, and the deterioration evaluation is performed based on the difference between the propagation speeds. 2. The deterioration evaluation method of a resin material according to claim 1, wherein the attenuation of each ultrasonic signal is obtained as the propagation characteristic, and the deterioration is evaluated based on the difference in the attenuation. A degradation evaluation device for a resin material having a degradation layer formed on the surface layer due to curing,
A propagation device installed on the surface of a resin material for propagating a plurality of ultrasonic signals including at least an ultrasonic signal with a frequency of 1.0 MHz or less and an ultrasonic signal with a frequency of 2.5 MHz or more into the resin material. and,
a calculation unit for calculating a difference in propagation characteristics of each ultrasonic signal acquired from the propagation device;
an evaluation unit that evaluates the deterioration of the resin material in the depth direction based on the difference in the propagation characteristics;
A deterioration evaluation device for a resin material, comprising:

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