JPH10307091A - Method and system for evaluating flexing fatigue resistance of elastomer material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a quantitative evaluation with high reproducibility by inputting a pure shear repetitive elongation and contraction with arbitrary waveform, displacement and frequency through cam mechanism. SOLUTION: A preliminary flaw is made in a sample composed of an elastomer material having lateral length three times or more longer than the longitudinal length, for example. The sample is subjected to pure shear repetitive elongation and contraction in the longitudinal direction and the length of a crack growing in the lateral direction is measured. More specifically, the sample is subjected to pure shear repetitive elongation and contraction by moving a shaft 4 on one side of a chuck for fixing the opposite ends of the sample through a motor driven cam mechanism 2 with fixed waveform, displacement and frequency. For example, a pseudo triangular repetitive elongation and contraction stimulus is inputted with displacement of 1.5 mm at 200 r.p.m. According to the arrangement, a constant crack grow rate is obtained and the flexing fatigue resistance of an elastomer material can be evaluated quantitatively with high reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for evaluating flex fatigue resistance of an elastomer material.

[0002]

2. Description of the Related Art Hitherto, as an index of flex fatigue property of an elastomer material, crack growth in a dematcher flex test is generally taken up. However, in the dematcher bending test, a cut gloss is put in the center of the sample, and the sample is bent to grow a crack. Therefore, the stimulus relating to the crack growth on the tip of the cut gloss constantly changes during the test. Therefore, in the dematcher bending test, the crack growth rate is not uniform during the test, and the results often differ even when a sample made of the same material is used, resulting in poor reproducibility. For these reasons, in the dematcher bending fatigue test, there is a problem that it is difficult to quantitatively evaluate the bending fatigue resistance of the elastomer material.

On the other hand, as a method for quantitatively evaluating crack growth due to bending fatigue, there is a crack growth evaluation based on pure shearing expansion and contraction. In this crack growth evaluation, a test piece having a predetermined length parallel to the horizontal direction and a predetermined length of pre-scratch is applied to one end of a sample that is sufficiently long in the horizontal direction, and a predetermined expansion and contraction is applied to the test piece. In this crack growth evaluation, the stimulus related to crack growth at the crack tip does not change during the test, and a stable crack growth rate is obtained, so the flexural fatigue resistance of the elastomer material can be quantitatively and reproducibly measured. Can be evaluated well.

[0004] When the crack growth is evaluated, it is necessary to repeat the expansion and contraction with a constant waveform, displacement and frequency. As a method for arbitrarily applying a repetitive stimulus having a constant waveform, displacement, and frequency, a device using a hydraulic servo is generally used and has high accuracy.

[0005] However, the hydraulic servo system is expensive and requires a dedicated hydraulic source, which increases the size of the device.
There is a problem that the installation space may be limited. Furthermore, in an evaluation having a certain period of time such as a fatigue test, evaluations under several different conditions must be performed in parallel, but a hydraulic servo system requires a hydraulic power source for each condition. In addition, there are problems such as excessive cost for the apparatus.

[0006]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a method and an apparatus for evaluating the bending fatigue resistance of an elastomer material, which can quantitatively and reproducibly evaluate the bending fatigue resistance of the elastomer material. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The first aspect of the present invention is that a sample having a shape that is sufficiently long in the horizontal direction as compared with the vertical direction is subjected to repeated pure shearing expansion and contraction in the vertical direction, and the crack length that grows in the horizontal direction is increased. A method for evaluating the bending fatigue resistance of an elastomer material, wherein the pure shearing repetitive expansion and contraction is input by a cam mechanism at an arbitrary waveform, displacement and frequency. Is the way.
In the present invention, it is more preferable that the waveform of the pure shearing repeated expansion and contraction is an intermittent wave.

[0008] A second aspect of the present invention is to provide an elastomeric material for measuring the length of a crack that grows in the lateral direction by subjecting a sample having a shape that is sufficiently longer in the lateral direction than in the longitudinal direction to repeated longitudinal shearing expansion and contraction. A method for evaluating bending fatigue resistance, wherein the pure shearing repetitive expansion and contraction is a method for evaluating bending fatigue resistance of an elastomer material, which is input by a crank mechanism in a sinusoidal waveform at an arbitrary displacement and frequency. Further, an apparatus for evaluating bending fatigue resistance of an elastomer material, which employs the first and second methods for evaluating bending fatigue resistance of an elastomer material of the present invention, is also one of the present invention. Since the flexural fatigue resistance evaluation apparatus for an elastomer material of the present invention uses a motor-driven cam mechanism or a crank mechanism as a stimulus input source, it does not impair stable crack growth and reproducibility, and is inexpensive and narrow. It can be installed in space.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The sample used in the present invention is an elastomer material, and has a shape that is sufficiently longer in the horizontal direction than in the vertical direction, as shown in FIG. The term “sufficiently long” means, for example, having a length three times or more in the vertical direction. The sample is preliminarily scratched.

FIG. 2 shows an embodiment of the bending fatigue resistance evaluation method of the present invention. The sample is subjected to repeated longitudinal pure shearing expansion and contraction, and the length of the crack growing in the lateral direction is measured. By moving a shaft on one side of the chuck for fixing both ends of the sample at a constant waveform, displacement and frequency by a cam mechanism driven by an electric motor, the pure shear can be repeatedly expanded and contracted to the sample.

As shown in FIG. 3, the cam mechanism used in the present invention may be of a type in which a roller is brought into close contact with a cam by a spring or the like. Large pressing force is required, and when high speed rotation or large force works, cam, roller,
The problem of friction and wear of bearings and the like is inevitable.
In consideration of these points, it is preferable to provide a rail-shaped groove on the outer periphery of the cam as shown in FIG.

When the waveform is a sine wave, pure shearing repetitive expansion and contraction of an arbitrary displacement and frequency can be applied to the sample by using a crank mechanism instead of a cam mechanism. In the present invention, by using a cam mechanism, not only a normal sine wave but also a pseudo-triangular wave, a pseudo-trapezoidal wave, an intermittent wave (pulse wave) having a rest portion between these expansion and contraction waveforms, and the like can be obtained. Can be entered.

[0013]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A test piece having a width of 100 mm, a height of 15 mm, and a thickness of 1 mm shown in FIG. 1 was prepared, and a preliminary scratch 1 was made 2 mm as shown in FIG. 1 and driven by a cam mechanism shown in FIG. The test piece was mounted on a stretching fatigue test apparatus having an attachment part, and a repetitive stretching stimulus consisting of a pseudo-triangular wave shown in FIG. 5 was input at a displacement of 1.5 mm and a rotation speed of 200 rpm, and the crack length (mm) was measured. It was measured. As a result, as shown in FIG. 10, a constant crack growth rate was obtained, and as shown in Table 1, there was almost no difference in the state of the crack growth even after repeating three times.

Embodiment 2 Instead of a cam mechanism, an expansion / contraction fatigue test apparatus having a sample mounting portion driven by a crank mechanism shown in FIG. 6 was used, and a displacement amount of 1.5 mm and a rotation speed of 200 rpm were used.
And the length of a crack (mm) was measured. As a result, as shown in FIG. 10, a constant crack growth rate was obtained, and the state of the crack growth showed almost no difference even after the third repetition, as shown in Table 1.

Comparative Example 1 A test piece having the shape shown in FIG. 8 was prepared using the same material as in Example 1, and was subjected to J-test using a dematcher bending tester shown in FIG.
A bending test was performed according to IS K6301, and the crack length (mm) was measured. As a result, the crack growth rate changed as shown in FIG. 10 with respect to the number of bendings, and a constant crack growth rate was not obtained. In addition, the state of crack growth changed as shown in Table 1 from the first time to the third time.

[0017]

[Table 1]

[0018]

As described above, the method for evaluating the bending fatigue resistance of an elastomer material according to the present invention is as described above, so that the bending fatigue resistance of the elastomer material can be evaluated quantitatively and with good reproducibility. An apparatus for evaluating the bending fatigue resistance of an elastomer material using this evaluation method is inexpensive and can be installed even in a narrow space.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a shape of a sample according to an embodiment of the present invention.

FIG. 2 is a schematic view of an embodiment of an apparatus for evaluating bending fatigue resistance of an elastomer material of the present invention driven by a cam mechanism.

FIG. 3 is an enlarged schematic view of a cam in one embodiment of the apparatus for evaluating bending fatigue resistance of an elastomer material of the present invention.

FIG. 4 is an enlarged schematic view of a cam in one embodiment of the apparatus for evaluating bending fatigue resistance of an elastomer material of the present invention.

FIG. 5 is a diagram showing an input waveform by a cam mechanism in the first embodiment.

FIG. 6 is a schematic view of one embodiment of an apparatus for evaluating bending fatigue resistance of an elastomer material of the present invention driven by a crank mechanism.

FIG. 7 is a diagram illustrating an input waveform by a crank mechanism according to the second embodiment.

FIG. 8 is a schematic diagram showing the shape of a sample in a dematcher bending test.

FIG. 9 is a schematic view showing an evaluation method of a dematcher bending test.

FIG. 10 is a diagram showing a crack growth rate in an example. The vertical axis represents the crack length (mm), and the horizontal axis represents the number of times of bending.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preliminary scratch 2 Cam 3 Rail-shaped groove 4 Shaft 5 Roller 6 Holding spring 7 Crank

Claims (4)

[Claims] 1. A flexural fatigue evaluation of an elastomer material in which a sample having a shape that is sufficiently longer in the horizontal direction than in the vertical direction is subjected to repeated pure shearing expansion and contraction in the vertical direction and the length of a crack growing in the horizontal direction is measured. A method for evaluating bending fatigue resistance of an elastomer material, wherein the pure shearing repetitive expansion and contraction is inputted by a cam mechanism with an arbitrary waveform, displacement and frequency. 2. The method for evaluating bending fatigue resistance of an elastomer material according to claim 1, wherein the waveform of the pure shearing repeated expansion and contraction is an intermittent wave. 3. A flexural fatigue evaluation of an elastomer material in which a sample having a shape sufficiently longer in the horizontal direction than in the vertical direction is subjected to repeated pure shearing expansion and contraction in the vertical direction, and the length of a crack growing in the horizontal direction is measured. A method for evaluating bending fatigue resistance of an elastomer material, characterized in that the pure shearing repetitive expansion and contraction is input in a sinusoidal waveform with an arbitrary displacement and frequency by a crank mechanism. 4. An apparatus for evaluating bending fatigue resistance of an elastomer material, wherein the method for evaluating bending fatigue resistance of an elastomer material according to claim 1, 2 or 3 is used.