JP2022095400A - Method for performance evaluation and performance evaluation device - Google Patents

Abstract

To provide a method for evaluating a performance that can obtain a high test result that is highly correlated to the performance when a vehicle is travelling.SOLUTION: A method for performance evaluation 100 includes: a strain provision step S2 of providing a strain to a test piece made of an elastic material; an imaging step S3 of irradiating the test piece with an X-ray and taking an image of a projected image; a measurement step S4 of measuring a density distribution of the elastic material from the projected image; a detection step S5 of detecting a low density region generated in the inside of the test piece in association with the provision of the strain; and an evaluation step S6 for evaluating the performance of the elastic material on the basis of the rate of generation of a low-density region.SELECTED DRAWING: Figure 2

Description

The present invention relates to a performance evaluation method for evaluating various performances such as wear resistance of an elastic material and a performance evaluation device used thereof.

Conventionally, as a method for evaluating the wear resistance of vulcanized rubber, for example, a method for evaluating the wear resistance based on the density distribution of a strained elastic material has been proposed. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-83182

The conventional method disclosed in Patent Document 1 is effective as a new evaluation technique in place of the Ramborn wear tester, and further improvement is expected.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a performance evaluation method and a performance evaluation device capable of evaluating the performance of an elastic material more quickly and accurately.

The performance evaluation device method according to the first aspect of the present invention is a method for evaluating the performance of an elastic material containing rubber or an elastomer, and includes a strain applying step of applying strain to a test piece made of the elastic material and the test. An imaging step of irradiating a piece with X-rays to take a projected image, a measuring step of measuring the density distribution of the elastic material from the projected image, and the generation inside the test piece due to the application of strain. It includes a detection step of detecting a low density region and an evaluation step of evaluating the performance of the elastic material based on the generation rate of the low density region.

In the performance evaluation device method according to the present invention, the low density region is a region in which the ratio of the density of the elastic material after the strain is applied to the density of the elastic material before the strain is applied is 10 to 80%. It is desirable to have.

In the performance evaluation device method according to the present invention, the measurement step includes a step of forming a tomographic image of the test piece using the projected image and a step of measuring the density distribution of the elastic material from the tomographic image. It is desirable to include.

In the performance evaluation device method according to the present invention, it is desirable that the strain is an extension strain.

In the performance evaluation device method according to the present invention, it is desirable that the generation rate is calculated by the following formula (1).
ν = V / ε (1)
However, ν: the production rate V: the volume ratio (%) of the low density region to the test piece.
ε: Stretch strain (%) applied to the test piece
And.

In the performance evaluation device method according to the present invention, it is desirable that the elastic material having a production rate ν of 50 or more is evaluated as the elastic material having excellent wear resistance.

In the performance evaluation device method according to the present invention, it is desirable that the extension strain is 20% or more.

The elastic material is a rubber obtained by using one or more kinds of conjugated diene compounds.
In the performance evaluation device method according to the present invention, it is desirable that the rubber is a rubber for a tire.

In the performance evaluation device method according to the present invention, it is desirable that the luminance (photons / s / mrad ² / mm ² / 0.1% bw) of the X-ray is 10 ¹⁰ or more.

In the performance evaluation device method according to the present invention, it is desirable that the brightness is 10 ¹² or more.

The performance evaluation device according to the second aspect of the present invention is a device for evaluating the performance of an elastic material containing rubber or an elastomer, and has a strain applying portion for applying strain to a test piece made of the elastic material and the test piece. Is irradiated with X-rays to capture a projected image, a measuring section that measures the density distribution of the elastic material from the projected image, and a unit generated inside the test piece as the strain is applied. It includes a detection unit that detects a low density region and an evaluation unit that evaluates the performance of the elastic material based on the generation rate of the low density region.

In the performance evaluation device according to the present invention, it is desirable that the photographing unit has a phosphor for converting X-rays into visible light, and the attenuation time of the phosphor is 100 ms or less.

In the performance evaluation device method of the first invention, in the detection step, the low density region generated inside the test piece due to the application of the strain is detected. Then, in the evaluation step, the performance of the elastic material is evaluated based on the generation rate of the low density region. This makes it possible to quickly and accurately evaluate the performance of the elastic material.

Then, in the second invention, the detection unit detects the low density region generated inside the test piece due to the application of the strain. Then, the evaluation unit evaluates the performance of the elastic material based on the generation rate of the low density region. This makes it possible to quickly and accurately evaluate the performance of the elastic material.

It is a perspective view which shows the schematic structure of one Embodiment of the performance evaluation apparatus of this invention. It is a flowchart which shows the processing procedure of the performance evaluation method of this invention. It is an exploded view which shows the test piece and the jig of FIG. It is a figure which shows an example of the projection image photographed by this invention schematically. It is a figure which shows typically the low density region detected after applying the extension strain to the test piece made of elastic material A. It is a figure which shows typically the low density region detected after applying the extension strain to the test piece made of elastic material A. It is a graph which shows the relationship between the stretch strain and the volume ratio of a low density region.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a schematic configuration of a performance evaluation device used in the performance evaluation method of the present embodiment. The performance evaluation device 1 of the present invention is a device for evaluating various performances such as wear resistance, chipping resistance, and crack resistance of elastic materials. As shown in FIG. 1, the performance evaluation device 1 of the present embodiment includes a distortion applying unit 2, a photographing unit 3, a measuring unit 4, a detecting unit 5, and an evaluation unit 6.

The strain applying portion 2 applies strain to the test piece 10 made of an elastic material containing rubber or an elastomer.

The strain applying unit 2 includes a pair of jigs 21 and 22 to which the test piece 10 is fixed, and a driving unit 23 that relatively moves the jig 21 and the jig 22 to apply strain to the test piece 10. Have. The drive unit 23 moves the other jig 22 in the axial direction of the test piece 10 with one jig 21 fixed. As a result, the test piece 10 is stretched in the axial direction thereof, and strain is applied to the test piece 10.

The strain or load applied to the test piece 10 is detected by a load cell (not shown) or the like. The position and format of the load cell are arbitrary. A predetermined strain or load is applied to the test piece 10 by the strain applying unit 2. The drive unit 23 is configured to rotate the test piece 10 and the jigs 21 and 22 around the axis of the test piece 10.

The photographing unit 3 irradiates the test piece 10 with X-rays and photographs a projected image. The photographing unit 3 has an X-ray tube 31 that irradiates X-rays, and a detector 32 that detects X-rays and converts them into electrical signals. By rotating the test piece 10 and the jigs 21 and 22 around the axis of the test piece 10 and taking a plurality of projected images by the photographing unit 3, it is possible to obtain a projected image of the test piece 10 over the entire circumference.

The detector 32 has a phosphor 32a for converting X-rays into visible light. The decay time of the phosphor 32a is preferably 100 ms or less. When the decay time of the phosphor 32a exceeds 100 ms, when a plurality of projected images are continuously photographed while rotating the test piece 10 or the like around the axis of the test piece 10, the afterimage of the previously captured projected image is displayed. It may affect the projected image taken later. From this point of view, the more desirable decay time of the phosphor 32a is 50 ms, and the more desirable decay time is 10 ms.

The measuring unit 4 measures the density distribution of the elastic material from the projected image. The detection unit 5 detects a low-density region generated inside the test piece 10 due to the application of strain. The evaluation unit 6 evaluates the performance of the elastic material based on the generation rate in the low density region.

For example, a computer 7 is applied to the measurement unit 4, the detection unit 5, and the evaluation unit 6. The computer 7 includes a main body 71, a keyboard 72, and a display device 73. The main body 71 is provided with, for example, a storage device such as an arithmetic processing unit (CPU), a ROM, a working memory, and a hard disk. Software for executing the performance evaluation method of the present embodiment is stored in the storage device in advance. The measurement unit 4, the detection unit 5, and the evaluation unit 6 are realized by the arithmetic processing apparatus executing the software.

FIG. 2 shows a processing procedure of a performance evaluation method 100 for evaluating the performance of an elastic material containing rubber or an elastomer using the performance evaluation device 1. The performance evaluation method 100 includes steps S1 to S8.

In step S1, the test piece 10 is fixed to the jigs 21 and 22.

FIG. 3 shows the test piece 10 and the jigs 21 and 22. In this embodiment, the columnar test piece 10 is applied. Such a test piece 10 has symmetry, and a highly reproducible measurement result can be easily obtained.

It is desirable that the test piece 10 has a diameter of 5 times or more the length in the axial direction thereof. According to such a test piece 10, when the test piece 10 is distorted, the deformation of the side surface of the test piece 10 is limited. As a result, the volume of the test piece 10 is increased, and a very large stress is applied to the inside. Therefore, the density distribution inside the test piece 10 is likely to be biased, and the performance of the elastic material can be evaluated quickly and easily.

The test piece 10 is fixed while being sandwiched between the jigs 21 and 22. The upper end surface 10a of the test piece 10 is fixed to the lower end surface 21a of the jig 21, and the lower end surface 10b of the test piece 10 is fixed to the upper end surface 22b of the jig 22. The fixing method can be appropriately selected depending on the test environment and the like. For example, fixing by an adhesive or fixing by vulcanization adhesion of an elastic material constituting the test piece 10 can be applied. Further, by providing corresponding engaging portions on the upper end surface 10a, the lower end surface 21a, the lower end surface 10b, and the upper end surface 22b and engaging the respective engaging portions, the test piece 10 and the jigs 21 and 22 are engaged. And may be fixed.

An elastic material having a uniform density distribution is used for the test piece 10. As an example of the elastic material constituting the test piece 10, for example, rubber obtained by using one or more kinds of conjugated diene compounds can be mentioned. Further, as an example of the elastic material constituting the test piece 10, rubber for a tire can be mentioned, for example.

In the strain applying step S2, as shown in FIG. 1, the jig 21 and the jig 22 are relatively moved by the drive unit 23, and strain is applied to the test piece 10. In the present embodiment, the columnar test piece 10 is moved in the axial direction, that is, in the direction in which the jig 22 is separated from the jig 21, and the test piece 10 is extended. The strain of the test piece 10 is not limited to stretching. For example, it may be compression strain or shear strain. By applying the strain in the strain applying step S2, stress is generated inside the elastic material, and the density is biased. Then, a low density region is generated inside the test piece 10.

The magnitude of the stretch strain is represented by the ratio (%) of the length of the test piece 10 after the strain is applied to the length (height) of the test piece 10 before the strain is applied.

In the photographing step S3, the test piece 10 is irradiated with X-rays from the X-ray tube 31 while rotating the test piece 10. X-rays pass through the test piece 10 and are detected by the detector 32. The detector 32 converts the detected X-rays into an electric signal and outputs the detected X-rays to the computer 7. The electrical signal output from the detector 32 is processed by the computer 60. As a result, the projected image of the test piece 10 is photographed and acquired.

When the test piece 10 having an unknown density is used, the photographing step S3 may be started prior to the strain applying step S2. As a result, a projection image for measuring the density of the test piece 10 before and after the strain applying step S2 is obtained.

The strain applied to the test piece 10 may be gradually increased. In this case, as shown in FIG. 5 described later, the strain applying step S2 and the photographing step S3 are repeated according to the number of steps.

FIG. 4 schematically shows a projected image taken through the steps S1 to S3. From the projected image, the low density region 15 generated inside the test piece 10 can be confirmed. The low density region 15 can be defined as, for example, a region where the density of the elastic material is below a predetermined threshold. The density of the elastic material can be calculated from the projected image.

In the measurement step S4, the density distribution of the elastic material is measured from the projected image. The measurement step S4 is executed by the arithmetic processing apparatus of the computer 7. The computer 7 acquires a three-dimensional tomographic image of the test piece 10 by reconstructing the projected image. As a result, the three-dimensional density distribution of the elastic material is measured. That is, the measurement step S4 includes a step of forming a tomographic image of the test piece 10 using a projected image and a step of measuring the density distribution of the elastic material from the tomographic image.

In the detection step S5, the three-dimensional shape of the low density region 15 in the test piece 10 is specified from the three-dimensional density distribution of the elastic material. Then, the computer 7 calculates the total volume of the low-density region 15 generated inside the test piece 10 due to the application of strain from the tomographic image.

Further, in the evaluation step S6, the performance of the elastic material is evaluated based on the formation rate of the low density region 15. The rate of formation is defined by the amount of increase in volume of the low density region 15 with respect to the amount of increase in strain.

As a result of diligent research, the inventor of the present application finally obtained the following findings regarding the relationship between the formation rate of the low density region 15 and the performance of the elastic material.

That is, when a strain such as elongation is applied to the elastic material, local stress concentration occurs inside the elastic material, and the molecular structure of the material is locally destroyed. Such a local stress concentration point becomes a starting point of wear in a micro region and accelerates the progress of wear.

On the other hand, inside the elastic material, the polymer moves so as to avoid the local stress concentration, and the low density region 15 shown in FIG. 4 is generated. Therefore, the faster the generation rate of the initial low-density region 15 to which strain is applied, the smaller the number of local stress concentration points in the rubber, and various performances such as wear resistance are improved.

Therefore, by calculating the generation rate of the low density region 15 when the elastic material is strained, the wear performance of the elastic material can be accurately predicted. For example, in an elastic material having a high volume generation rate in the low density region 15, it can be predicted that there are few local stress concentration points and various performances such as wear resistance are improved. Then, various performances can be quantified and evaluated objectively and accurately by calculating the generation rate of the low density region 15. Therefore, according to the performance evaluation method 100 using the performance evaluation device 1, the performance of the elastic material can be evaluated quickly and accurately.

The low density region 15 is defined as, for example, a region in which the ratio of the density of the elastic material after the strain is applied to the density of the elastic material before the strain is applied is 10 to 80%. By defining the low density region 15 in this way, it is possible to accurately estimate the region where the local stress concentration is small, which is effective for improving the performance of the elastic material.

5 and 6 show the low density region 15 detected after applying the same tensile strain (20%) to the test piece 10A made of the elastic material A and the test piece 10B made of the elastic material B. In the test piece 10A, more low density regions 15 were generated for the test piece 10B. Therefore, it can be estimated that the elastic material A relaxes the local stress concentration with respect to the elastic material B.

The volume of the low density region 15 can be calculated by adding the tomographic images obtained by the X-ray CT method. The thickness of the tomographic image depends on the spatial resolution of X-ray CT imaging. In this measurement, the volume was calculated by adding 200 tomographic images with a thickness of 10 μm.

It is desirable that the formation rate of the low density region 15 is calculated by the following equation (1).
ν = V / ε (1)
However, ν: Generation rate V: Volume ratio (%) of the low density region in the test piece
ε: Stretch strain (%) applied to the test piece
And.

FIG. 7 shows the relationship between the stretch strain ε of the elastic materials A and B and the volume ratio V of the low density region 15. The generation rate ν of the low density region 15 is indicated by the slopes of the lines A and B. Since the elastic material A has a higher formation rate ν in the low density region 15 than the elastic material B, local stress concentration is relaxed and the destruction of the molecular structure is suppressed.

Further, an elastic material having a production rate ν of the low density region 15 of 50 or more may be evaluated as an elastic material having excellent wear resistance. This makes it possible to easily evaluate the wear resistance performance of the elastic material.

The extension strain ε is preferably 20% or more. When the stretch strain ε is 20% or more, a low density region 15 having a sufficient volume is generated inside the elastic material, and the evaluation accuracy of the performance of the elastic material is easily improved.

When the stretch strain ε becomes large, the adjacent low-density regions 15 are connected to each other, and there is a possibility that the generation rate ν of the initial low-density region 15 cannot be calculated accurately. Therefore, the extension strain ε is preferably 100% or less.

The brightness of the X-rays incident on the test piece 10 in the photographing step S3 is greatly related to the S / N ratio of the X-ray scattering data. When the brightness of X-rays is small, the signal intensity tends to be weaker than the statistical error of X-rays, and even if the measurement time is lengthened, it may be difficult to obtain data with a sufficiently good S / N ratio. .. From this point of view, the brightness of X-rays (photons / s / mrad ² / mm ² / 0.1% bw) is preferably 10 ¹⁰ or more, and the more desirable brightness is 10 ¹² or more.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned specific embodiments, but is modified to various embodiments.

The wear resistance of the elastic materials A to F was evaluated by the present invention, and the correlation with the evaluation of the wear resistance by the actual vehicle running test was verified. As a comparative example, the elastic materials A to F were evaluated for wear resistance using a Ramborn tester according to the present invention, and their correlation with the evaluation of wear resistance by an actual vehicle running test was verified.

The reagents used are as follows.
1. 1. Polymer (1): (1 modifying group)
2. 2. Polymer (2): (2 modifying groups; different amount of monomer of polymer (1))
3. 3. Polymer (3): (3 modifying groups; different amount of monomer of polymer (1))
4. SBR: Nippon Zeon Co., Ltd. Nipol NS522
5. BR: BR150B manufactured by Ube Corporation
6. Denaturer: 3- (N, N-dimethylaminopropyl) trimethoxysilane manufactured by Azumax Co., Ltd. 7. Anti-aging agent: Nocrack 6C (N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
8. Stearic acid: Stearin manufactured by NOF CORPORATION 9. Zinc Oxide: Toho Zinc's Ginmine R
10. Aromatic oil: Diana Process AH-24 (manufactured by Idemitsu Kosan)
11. Wax: Sunknock wax manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. 12. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. 13. Vulcanization accelerator (1): Noxeller CZ manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
14. Vulcanization accelerator (2): Noxeller D manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
15. Silica: Ultra Jill VN3 made by Degussa
16. Silane coupling agent: Si69 made by Degussa
17. Carbon black: Dia black LH (N326, N2SA: 84m2 / g) manufactured by Mitsubishi Chemical Corporation.

The monomers and polymers were synthesized by the following methods.
<Monomer (1)>
To a 100 ml container fully substituted with nitrogen, 50 ml of cyclohexane, 4.1 ml of pyrrolidine and 8.9 ml of divinylbenzene were added, 0.7 ml of a 1.6 M n-butyllithium hexane solution was added at 0 ° C., and the mixture was stirred. After 1 hour, isopropanol was added to stop the reaction, and extraction and purification were carried out to obtain the monomer (1).
<Polymer (1)>
600 ml of cyclohexane, 12.6 ml of styrene, 71.0 ml of butadiene, 0.06 g of monomer (1) and 0.11 ml of tetramethylethylenediamine were added to a 1000 ml pressure-resistant container sufficiently substituted with nitrogen, and 1.6 M n- at 40 ° C. 0.2 ml of butyllithium hexane solution was added and stirred. After 3 hours, 0.5 ml of denaturant was added and stirred. After 1 hour, 3 ml of isopropanol was added to terminate the polymerization. After adding 1 g of 2,6-tert-butyl-p-cresol to the reaction solution, reprecipitation treatment was carried out with methanol, and the polymer (1) was obtained by heating and drying.
<Polymer (2)>
The amount of the monomer (1) was 0.17 g, and the polymer (2) was obtained by the same method as that of the polymer (1).
<Polymer (3)>
The amount of the monomer (1) was 0.29 g, and the polymer (3) was obtained by the same method as that of the polymer (1).

The test method is as follows.
<Evaluation of generation rate>
For the elastic materials C to E, columnar test pieces having a diameter of 20 mm and a length in the axial direction of 1 mm were prepared, and the performance evaluation device shown in FIG. 1 was used, and the performance evaluation device method shown in FIG. 2 was used. The performance of the elastic material was evaluated. In the strain applying step S2, a stretch strain of 20% was applied to the test piece. In step S6, the wear resistance performance was evaluated based on the formation rate ν of the low density region 15. The result is expressed as an index, and the larger the value, the better the wear resistance performance.

<Ranborn test>
The amount of wear of the elastic materials C to E was measured using a Ramborn type wear tester under the conditions of room temperature, a load load of 1.0 kgf, and a slip ratio of 30%, and the reciprocal thereof was calculated. The result is an index with the elastic material C as 100, and the larger the value, the better the wear resistance performance.

<Actual vehicle driving test>
A size 195 / 65R15 pneumatic tire having a tread portion made of elastic materials C to E was created, mounted on a domestic FF vehicle, the groove depth of the tread portion was measured at a mileage of 8000 km, and the amount of wear of the tread portion was measured. The mileage per 1 mm was calculated. The result is an index with the elastic material C as 100, and the larger the value, the better the wear resistance performance.

As is clear from Table 1, it was confirmed that the performance evaluation device method of the example had a better correlation with the actual vehicle running test than the comparative example, and could accurately predict the performance of the elastic material.

1 Performance evaluation device 2 Straining unit 3 Imaging unit 4 Measuring unit 5 Detection unit 6 Evaluation unit 10 Test piece 15 Low density region 32a Phosphorus 100 Performance evaluation method S2 Straining process S3 Imaging process S4 Measurement process S5 Detection process S6 Evaluation process

Claims (13)

A method of evaluating the performance of elastic materials, including rubber or elastomers.
A strain applying step of applying strain to a test piece made of the elastic material, and
The imaging process of irradiating the test piece with X-rays and photographing the projected image,
A measurement step of measuring the density distribution of the elastic material from the projected image,
A detection step for detecting a low density region generated inside the test piece due to the application of the strain, and a detection step.
Including an evaluation step of evaluating the performance of the elastic material based on the formation rate of the low density region.
Performance evaluation method. The performance evaluation method according to claim 1, wherein the low density region is a region in which the ratio of the density of the elastic material after the strain is applied to the density of the elastic material before the strain is applied is 10 to 80%. .. The measurement step is
A step of constructing a tomographic image of the test piece using the projected image and
The performance evaluation method according to claim 1 or 2, comprising a step of measuring the density distribution of the elastic material from the tomographic image. The performance evaluation method according to any one of claims 1 to 3, wherein the strain is an extension strain. The performance evaluation method according to claim 4, wherein the generation rate is calculated by the following formula (1).
ν = V / ε (1)
However, ν: the production rate V: the volume ratio (%) of the low density region to the test piece.
ε: Stretch strain (%) applied to the test piece
And. The performance evaluation method according to claim 5, wherein the elastic material having a production rate ν of 50 or more is evaluated to be the elastic material having excellent wear resistance. The performance evaluation method according to any one of claims 4 to 6, wherein the extension strain is 20% or more. The performance evaluation method according to any one of claims 1 to 7, wherein the elastic material is a rubber obtained by using one or more kinds of conjugated diene compounds. The performance evaluation method according to claim 8, wherein the rubber is a rubber for a tire. The performance evaluation method according to any one of claims 1 to 9, wherein the X-ray luminance (photons / s / mrad ² / mm ² / 0.1% bw) is 10 ¹⁰ or more. The performance evaluation method according to claim 10, wherein the brightness is 10 ¹² or more. A device for evaluating the performance of elastic materials including rubber or elastomers.
A strain-imparting portion that imparts strain to a test piece made of the elastic material,
An imaging unit that irradiates the test piece with X-rays and captures a projected image,
A measuring unit that measures the density distribution of the elastic material from the projected image,
A detection unit that detects a low-density region generated inside the test piece due to the application of the strain, and a detection unit.
Including an evaluation unit that evaluates the performance of the elastic material based on the formation rate of the low density region.
Performance evaluation device. The photographing unit has a phosphor for converting X-rays into visible light.
The performance evaluation device according to claim 12, wherein the decay time of the phosphor is 100 ms or less.

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