JPH08304250A - Fatigue test method of rubber composite and test piece used in the fatigue test method - Google Patents

Abstract

(57) [Summary] [Purpose] In the fatigue test and test pieces in which the residual tensile strength of the reinforcement is measured by applying repeated stress of extension and compression, the variation in the measured data of the residual tensile strength obtained is minimized. A rubber composite in which a canvas 5 is embedded at a middle position in the thickness direction of the rubber body 4 so as to extend continuously in the longitudinal direction is used for the strip plate. The test piece 1 is composed of the main body 2 and the bulging portions 3 and 3 in which the rubber bodies at both ends are projected to both sides in the thickness direction.
Grooves 2 on both sides in the thickness direction of the central position of the main body in the longitudinal direction
Then, a and 2a are formed to form a defective section. Both ends are attached to both disks of the disk fatigue tester, and by rotating both disks, repetitive stress of expansion and compression in the longitudinal direction is concentratedly applied to the groove position, and then both bulging parts are chucked by a chuck. Then, the residual tensile strength of the tension canvas is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composite body such as a timing belt in which a reinforcing body such as a canvas or a cord is embedded in a rubber body in order to evaluate the fatigue property of the canvas or the like as the reinforcing body. The present invention relates to a fatigue test method performed and a test piece used for the fatigue test method.

[0002]

2. Description of the Related Art The Goodrich method using a disk fatigue tester has been known as a fatigue test method for rubber composites of this type (see JIS L 1017 3.2.2.2 Disk fatigue strength). This is because two discs are tilted from each other so that the gap between the two discs is narrower on one side in the diametrical direction and wider on the other side. The test piece is set to have a predetermined compression rate, while the wide disk spacing is set to a dimension at which the test piece has a predetermined expansion rate. This is to repeatedly apply compression and expansion. After that, the reinforcing body is taken out from the test piece and a tensile force is applied in the longitudinal direction to measure the residual tensile strength. Then, based on this, the strength retention rate (extension
By obtaining the compression fatigue ratio), the fatigue property of the canvas or the like as the reinforcing body is evaluated.

Further, as a test piece used in the above fatigue testing method, generally, as shown in FIG. 7, a rubber body 4 and a rubber body 4 are embedded so as to extend continuously in the longitudinal direction at an intermediate position in the thickness direction. It is known that a rubber composite is formed from the reinforcing body 5 thus formed, and that the rubber body 4 and the reinforcing body 5 are formed in a strip plate shape extending in the longitudinal direction in equal cross sections. Then, both ends of the test piece 13 are attached to the peripheral edges of the respective disks, and the test piece 13 between the both end portions is subjected to repeated stress of extension and compression, and thereafter, as shown in FIG. The residual tensile strength is measured by moving the two chucks 8 and 9 relative to each other in the pulling direction while gripping the parts with the chuck pieces 8a, 8a, 9a and 9a of the chucks 8 and 9, respectively.

[0004]

However, in the above-mentioned conventional fatigue testing method for rubber composites and test pieces thereof,
Since the test piece 13 extending in the longitudinal direction with an equal cross section is used, even if both end portions of the test piece are attached to both disks and elongation and compression forces are applied in the longitudinal direction, repeated stress (strain) due to the elongation and compression is obtained. Is not concentrated at one point, and the resulting residual tensile strength data tends to vary. Moreover, in measuring the residual tensile strength of the reinforcement,
The cloth or cord as a reinforcement embedded in the rubber body is taken out from the test piece after the repeated stress of extension and compression, and the residual tensile strength of the taken out cloth or the like is measured. Therefore, the canvas or cord may be pulled or damaged during the taking-out, which tends to further increase the variation in the data.

On the other hand, in order to eliminate the above-mentioned inconvenience when taking out the canvas and the like, the residual tensile strength of the reinforcing member is measured by
It is conceivable that a tensile force is directly applied to the test piece in which the canvas or the like is embedded without removing the canvas or the like from the rubber body. However, when this method is adopted,
As described above, since the strain due to the repeated expansion and compression is generated at a plurality of positions dispersed in the longitudinal direction, the breakage position, which is the final state, is not constant, and accordingly the data is varied. Moreover, in this case, both end portions of the strip-shaped test piece having an equal cross section, that is, the smooth surface of the rubber body surface is gripped by the chucks, so that each chuck slides along the rubber body surface. However, stable measurement cannot be performed. In this case, to prevent slippage,
If the gripping force of each chuck is increased and the chucks are sandwiched by a large pressure, a situation occurs in which the chucking portion is cut, and stable data cannot be obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to perform a fatigue test in which a residual tensile strength of a reinforcing body is measured by applying repeated stress of extension and compression. In the test piece used for that purpose, the variation of the obtained residual tensile strength measurement data should be minimized to obtain stable data. In addition, it is to facilitate and ensure the measurement of the residual tensile strength while securing stable data.

[0007]

In order to achieve the above object, the invention according to claim 1 is a rubber composite body in which a reinforcing body is embedded at a middle position in the thickness direction of the rubber body so as to extend continuously in the longitudinal direction. The fatigue test method of the rubber composite is premised on measuring the residual tensile strength of the reinforcing body in the longitudinal direction after repeatedly stretching and compressing the test piece in the longitudinal direction. In this, the test piece,
The rubber body and the reinforcing body are formed so as to extend in the longitudinal direction in equal cross sections, respectively, and a cross section defective portion is provided at one location in the longitudinal direction of the rubber body so that the repeated stress due to the expansion and compression is applied to the cross sectional defective portion. It is configured to concentrate on the.

According to a second aspect of the present invention, in the first aspect of the present invention, the cross-section defective portion is formed by a concave groove portion formed so as to extend over the entire width of the rubber body in the width direction orthogonal to the longitudinal direction of the test piece. To do.

According to a third aspect of the present invention, in the second aspect of the present invention, the concave groove portions are formed in the rubber bodies at both sides in the thickness direction with the reinforcing body of the test piece sandwiched therebetween.

According to a fourth aspect of the present invention, in the invention according to the first aspect, the residual tensile strength of the reinforcing member is measured by gripping both end portions in the longitudinal direction of the test piece and pulling the test pieces away from each other in the longitudinal direction. It is something to do.

According to a fifth aspect of the invention, in the invention according to the fourth aspect, bulging portions bulging on both sides in the thickness direction of the test piece are formed at both end portions in the longitudinal direction of the test piece, and the residual tensile strength is measured. At this time, chucks are engaged with and gripped by the respective bulging portions, and both chucks are relatively moved in the pulling direction.

According to a sixth aspect of the present invention, a rubber composite is composed of a rubber body and a reinforcing body embedded at a middle position in the thickness direction of the rubber body so as to extend continuously in the longitudinal direction.
It is premised on a test piece used in a fatigue test method for a rubber composite, in which the residual tensile strength of the reinforcing body in the longitudinal direction is measured after repeatedly extending and compressing in the longitudinal direction. In this structure, the rubber composite is formed such that the rubber body and the reinforcing body respectively extend in the longitudinal direction in an equal cross section, and a repetitive stress due to the expansion and compression is applied to one location in the longitudinal direction of the rubber body. The configuration is such that the cross-section defective portion is formed so as to act in a concentrated manner.

According to a seventh aspect of the invention, in the sixth aspect of the invention, the cross-section defective portion is constituted by a concave groove portion formed so as to extend over the entire width of the rubber body in the width direction orthogonal to the longitudinal direction of the rubber composite. To do.

According to an eighth aspect of the invention, in the invention of the seventh aspect, the concave groove portions are formed in the rubber bodies at both positions in the thickness direction with the reinforcing body of the rubber composite body sandwiched therebetween.

Further, the invention of claim 9 is the same as claim 6.
In the invention described above, bulging portions that project to both sides in the thickness direction and engage with the gripping chuck are formed at both end portions in the longitudinal direction of the rubber composite.

[0016]

According to the above-mentioned structure, according to the first aspect of the present invention,
A test piece of a rubber composite body comprising a rubber body and a reinforcing body is provided with a cross-section defect portion at one position in the longitudinal direction of the rubber body so that the repeated stress due to the expansion and compression is concentrated on the cross-section defect portion. Therefore, the strain due to the repeated expansion and compression is concentrated on the cross-section defective portion, that is, at one point in the longitudinal direction of the test piece. For this reason, the fatigue due to the loading of the repeated stress is concentrated on one specific place of the test piece extending in the longitudinal direction, and in the measurement of the residual tensile strength of the reinforcing body, the fatigue is broken at the specific one place. As a result, even if a plurality of test pieces are formed identically to each other in the conventional fatigue test method, the fatigue due to the repeated stress is dispersed in the longitudinal direction, resulting in different positions for each test piece in the measurement of the residual tensile strength. In contrast to the fact that there is a variation between the data due to the fracture at, the fatigue test method of the present invention greatly reduces such a variation between the data. Then, the influence of the predetermined repeated fatigue of the elongation and compression is directly reflected in the measured residual tensile strength, and by comparing the residual tensile strength and the tensile strength before fatigue, the fatigue property due to the repetition of elongation and compression. It becomes possible to evaluate more accurately.

According to the invention of claim 2 or 7,
Since the cross-section defective portion is constituted by the concave groove portion formed so as to extend over the entire width of the rubber body in the width direction orthogonal to the longitudinal direction of the test piece, as a cross-sectional defective portion that concentrates repetitive stress due to extension and compression, It is possible to easily form such a cross-section defective portion.

In the invention according to claim 3 or claim 8,
Since the concave groove is formed in the rubber body at both sides in the thickness direction with the reinforcing body of the test piece sandwiched between them, strain is repeatedly generated more intensively for one point in the longitudinal direction of the reinforcing body embedded in the rubber body. This is more suitable as the cross-section defective portion provided at one specific location in the longitudinal direction of the test piece.

According to the invention described in claim 4, in addition to the action according to the invention described in claim 1, the measurement of the residual tensile strength of the reinforcing body is performed by gripping both longitudinal end portions of the test piece and separating them from each other in the longitudinal direction. Since it is performed by pulling to the side, labor saving of the work to take out the embedded reinforcing body from the test piece after the action of repeated stress of extension and compression can be achieved, and the reinforcing body that tends to occur during the taking out work. It is possible to surely prevent the damage and the inadvertent loading of tensile force. As a result, in the measurement of the residual tensile strength, the occurrence of variations among the measurement data due to the damage of the reinforcing body and the like is eliminated. Moreover, even if the residual tensile strength of the reinforcing body is measured not by the reinforcing body itself but by pulling the test piece embedded in the rubber body, there is a defective cross section due to repeated stress due to extension and compression. Since the strain is concentrated on the reinforcing body at one specific position in the longitudinal direction, the reinforcing body is broken at this specific one position, which makes it possible to accurately evaluate the fatigue property of the reinforcing body.

In the invention according to claim 5 or claim 9, bulging portions bulging in both sides in the thickness direction of the test piece are formed at both end portions in the longitudinal direction of the test piece, and when measuring the residual tensile strength, Since the step position of each bulge is gripped by the chucks and both chucks are moved relative to each other in the pulling direction, the gripping of the test piece by each chuck can be performed without increasing the gripping pressure of each chuck so much. Be certain. In addition, the inconvenience that the test piece is cut at the chucking portion by each chuck is prevented from occurring, and the occurrence of variations between measurement data due to the occurrence of the cutting is eliminated.

According to the sixth aspect of the present invention, since the test piece of the rubber composite body including the rubber body and the reinforcing body is provided with the cross-section defective portion at one position in the longitudinal direction of the rubber body, the extension and compression are performed. When a repetitive stress is applied, the strain due to repetitive stretching and compression is concentrated on the cross-section defective portion, that is, at one point in the longitudinal direction of the test piece.
Therefore, the fatigue due to the loading of the repeated stress is concentrated on one specific place of the test piece extending in the longitudinal direction, and in the measurement of the residual tensile strength of the reinforcement body performed using this test piece, the fracture should occur at the specific one place. become. As a result, even if a plurality of test pieces are formed identically to each other in the conventional test piece, the fatigue due to the above repeated stress is dispersed in the longitudinal direction, and as a result, at different positions for each test piece in the measurement of the residual tensile strength. Whereas, due to the breakage, a variation between data is generated, whereas in the test piece of the present invention, such a variation between data is significantly reduced. Then, by performing a fatigue test using such a test piece, the effect of fatigue due to the predetermined repetition of the elongation and compression is directly reflected in the measured residual tensile strength, before the residual tensile strength and fatigue. By comparing with the tensile strength of No. 1, it is possible to more accurately evaluate the fatigue property due to repeated stretching and compression.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

<Test Piece> FIGS. 1 and 2 show a test piece 1 according to an embodiment of the present invention. Reference numeral 2 denotes a strip-like plate (including a rod-like plate) to which fatigue is forcibly given by a disk fatigue tester described later. 3) and 3) are bulging portions formed on both ends of the body portion 2.

The main body 2 and the bulging portions 3 and 3 are made of a rubber compound which is composed of a rubber body 4 containing hydrogenated nitrile rubber (H-NBR) as a main component and a canvas 5 as a reinforcing member, which is an integrated rubber compound. Formed as a body. The canvas 5 extends in the longitudinal direction (horizontal direction in the drawing) at the central position in the thickness direction (vertical direction in the drawing) of the rubber body 4 in the width direction of the main body 2 (direction orthogonal to the paper surface of FIG. 2). It is buried so as to extend continuously over the entire length. And the said test piece 1
Is formed in a state in which the canvas 5 and the rubber body 4 are vulcanized and adhered to each other by integral vulcanization molding and are in close contact with each other.

At the center of the main body 2 in the longitudinal direction, recessed groove portions 2a as cross-section defective portions are formed on both side surfaces in the thickness direction of the rubber body 4 constituting the main body portion 2 so as to extend over the entire width. There is. The bulging portions 3 are formed such that the rubber bodies 4 at both end portions of the main body portion 2 are projected to both sides in the thickness direction and have a substantially rectangular parallelepiped shape.

<Fatigue Test Method> FIG. 3 shows an outline of a fatigue tester for performing a fatigue test using the test piece 1. This fatigue testing machine is based on the disk fatigue testing machine by the Goodrich method specified in 3.2.2.2 of JIS L 1071, and has a pair of opposed disks 6a and 6b.
And a pair of rotary drive shafts 7 fixed to the central positions of the disks 6a and 6b to rotate the disks 6a and 6b.
a and 7b. Both rotation drive shafts 7a, 7b
Are eccentrically arranged with respect to each other, and both the disks 6a and 6b are
The interval between them is set to be narrow at the peripheral edge on one side (upper side in the illustrated example) in the diametrical direction and wider at the peripheral edge on the other side (lower side in the illustrated example).

In the fatigue testing machine, the test piece 1 is bridged between the peripheral edges of the disks 6a and 6b and fixed to the peripheral edges of the disks 6a and 6b at the positions of the bulged portions 3 and 3 respectively. By rotating both the disks 6a and 6b in the same rotational direction in the mounted state, a predetermined compression rate is obtained in the longitudinal direction of the test piece 1 when the test piece 1 is at the upper rotational position in the drawing. A compressive force is applied, and an extension force having a predetermined extension rate is applied in the longitudinal direction when in the lower rotation position. Further, the compression force and the extension force are repeatedly applied to the test piece 1 by continuing the rotation.

The fatigue test method using the above test piece 1 is as follows.
First, the fatigue tester 1 applies repetitive stress of elongation and compression to the test piece 1 to give fatigue, and then the test piece 1 after the fatigue is removed from the fatigue tester and pulled in the longitudinal direction to obtain the residual tensile strength. By measuring.

To mount the test piece 1 on the fatigue tester, the test piece 1 is bridged between the peripheral edges of both disks 6a and 6b, and both bulges 3 and 3 are fixed to the peripheral edges of the disks 6a and 6b. By doing. And both rotary drive shafts 7a, 7b
Is rotated in the same rotation direction a predetermined number of times, so that repeated stress of extension and compression is applied a predetermined number of times.

As shown in FIG. 4, the residual tensile strength was measured by holding the fatigue-treated test piece 1 with a pair of chucks 8 and 9 and holding the two chucks 8 and 9 together. The test pieces 1 are relatively moved in the longitudinal direction (vertical direction in FIG. 4) away from each other until the fracture occurs, and the tensile force until the fracture is measured. The pair of chucks 8 and 9 described above each include a pair of L-shaped chuck pieces 8a, 8a, 9a and 9a whose tip claw portions are arranged to face each other. For gripping, the two swelling portions 3 of the test piece 1 are sandwiched by both chuck pieces 8a, 8a or 9a, 9a from both sides in the thickness direction of the swelling portions 3 on both sides in the thickness direction and the surface of the body portion 2 side. To engage.

<Operations and Effects of Examples> In the test piece and the fatigue test method using the test piece, the repeated stresses of extension and compression acting by the rotational driving of both disks 6a and 6b of the fatigue tester are both applied. It acts in a concentrated manner at a position sandwiched by the concave groove portions 2a, 2a, that is, at a single point position in the longitudinal center of the test piece 1. As a result, strain is concentratedly generated at the one point position, and fatigue due to the action of the above repeated stress is concentratedly given to the central position in the longitudinal direction of the test piece 1, and the rotational speeds of the disks 6a and 6b. And, the correlation with the fatigue given to the test piece 1 becomes closer. As a result, in the measurement of the residual tensile strength, the test piece 1 can be fractured at the central position, that is, at a constant position of the test piece 1, and the variation of the measurement data is suppressed and prevented, which is stable. Measurement data can be obtained. Moreover, even if a method of applying a tensile force to the test piece 1 itself without taking out the buried canvas 5 from the rubber body 4 of the test piece 1, accurate measurement data on the residual tensile strength of the cloth 5 itself is obtained. Obtainable. Therefore, in the measurement of the residual tensile strength, it is possible to save labor in the work of taking out the buried canvas 5, and at the same time, damage to the canvas 5 that is likely to occur during the taking out work and inadvertent loading of tensile force, etc. Can be reliably prevented. As a result, it is possible to eliminate the influence on the measurement data due to the damage of the canvas 5 and the like, and it is possible to further suppress and prevent the occurrence of the variation between the measurement data.

Moreover, the bulging portions 3, 3 are formed at both end portions of the test piece 1.
Since the chucks 8 and 9 are engaged with and pulled by the bulging portions 3 and 3, respectively, the test piece does not slip even if the gripping pressure of the chucks 8 and 9 is not so high. 1 can be gripped with certainty, and the inconvenience of cutting the test piece 1 at the chucking portion can be avoided. As a result, it is possible to reliably prevent the occurrence of variations between measurement data due to the occurrence of slippage or cutting.

The fatigue imparted to the test piece 1 is directly reflected in the above measured residual tensile strength, and the variation between the measured data is greatly reduced. Therefore, the residual tensile strength and the tensile strength before fatigue are reduced. By comparing with the strength, it is possible to more accurately evaluate the fatigue property due to repeated stretching and compression. As a result, in developing a member used as a reinforcing body, it becomes possible to quickly and accurately determine the direction of the development, and the efficiency of research and development of the reinforcing body and the product of the rubber composite using the same. Can be realized.

<Comparative Test> Test piece 1 according to the above-mentioned embodiment
And a test piece 1 according to three types of comparative examples shown in FIGS.
Fatigue tests were conducted using 1, 12, and 13, and the results were compared.

-Setting of test piece- The test piece 11 of Comparative Example 1 (see FIG. 5) is obtained by omitting the formation of the recessed groove portions 2 and 2 from the test piece 1 according to the embodiment, Comparative Example 2
Test piece 12 (see FIG. 6) in which the formation of the bulging portions 3 and 3 is omitted from the test piece 1 and the concave groove portions 2a and 2a are arranged so as to be displaced from each other in the longitudinal direction, and the test piece 13 of Comparative Example 3
(See FIG. 7) is a conventionally used test piece 1 in which the formation of the concave groove portions 2a, 2a and the formation of the bulging portions 3, 3 are omitted. And each of the above test pieces 1, 1
18 to 2 for each of four types of 1, 12, and 13
Zero test pieces were formed.

The composition of each rubber body 4 of each test piece 1, 11, 12, 13 is shown below.

H-NBR 100 parts by weight Carbon black (FEF) 50 parts by weight Plasticizer 10 parts by weight Vulcanization accelerator 4 parts by weight Anti-aging agent 2 parts by weight Stearic acid 1 part by weight Zinc oxide 5 parts by weight Sulfur 0.5 parts by weight Part In addition, each canvas 5 of each test piece 1, 11, 12, 13 has a warp of 6.6 nylon (210 denier x 1 174/5 cm) twisted yarn and a weft of 6.6 nylon (210 denier). X two 130 yarns / 5 cm) each,

[Equation 1]

A 2/2 twill weave structure was used, which was subjected to sizing processing.

-Fatigue test conditions-While maintaining the temperature condition at room temperature, both disks 6a and 6b were rotated 1 x 10 ⁵ times at a rotation speed of 1000 rpm. At this time, the distortion angle of both disks 6a and 6b is set to 3 degrees (the distortion amount ±
15%).

-Fatigue Test Results and Discussion-Table 1 shows comparative test results.

[0041]

[Table 1]

As a result of the comparative test, each test piece 1, 11, 1
The occurrence of slippage in the chucking portion between the chucks 2 and 13 and the chucks 8 and 9 did not occur in the example in which the bulging portions 3 and 3 were formed and the comparative example 1, but the bulging portion 3 described above was not generated. In Comparative Example 2 and Comparative Example 3 in which 20 and 30 were not present, almost all of 20 test pieces occurred (FIGS. 11 and 12).
In the above, a “*” mark is attached above the test piece No where slippage occurred). As a result, it can be seen that the formation of the bulges 3 and 3 can prevent the occurrence of slippage between the chucks 8 and 9 and the test piece when measuring the residual tensile strength.

The occurrence of cutting of each of the test pieces 1, 11, 12, and 13 at the chucking portion at the time of measuring the residual strength did not occur in the example, but occurred in all of the comparative examples 1 to 3. In Comparative Examples 2 and 3, bulging portions 3 and 3
Therefore, the pressure for sandwiching the chucks 8 and 9 has to be increased, and it is considered that the cutting at the chucking portion has occurred because of this. On the other hand, even in Comparative Example 1 in which the bulged portions 3 and 3 are formed, the cutting at the chucking portion occurs because in the case of Comparative Example 1, the concave groove portion 2 as in the embodiment is used.
Since there is no a or 2a, the repeated stress of extension and compression is dispersed in the entire longitudinal direction of the main body 2 and the influence of fatigue is dispersed in the main body 2. As a result, the main body 2 and each bulging portion 3 are separated. It is conceivable that the chucking portion, which is the sudden change in cross section of the boundary, cuts first.

Regarding the generation of cracks, in Example and Comparative Example 2, cracks were generated at the positions where the concave groove portions 2a were formed, but Comparative Example 1 and Comparative Example 3 without the concave groove portions 2a as described above.
Then, cracks occurred in the entire area except the chucking portion.

Regarding the residual tensile strength of the canvas, in the case of the example, all the measured data are 75 to 85 k as shown in FIG.
Values between g are shown, and measurement data with little variation are obtained. On the other hand, in Comparative Example 1, as shown in FIG. 10, two test pieces Nos. 8 and 11 were cut in the middle to make measurement impossible, and the measurement data obtained for the rest were in the range of 70 to 90 kg. There are variations. Also,
In Comparative Example 2, as shown in FIG. 11, three test pieces of test pieces Nos. 7, 14 and 18 were cut in the middle and measurement became impossible,
The obtained measurement data also vary from 57 to 80 kg in a fairly wide range. Further, in Comparative Example 3, FIG.
As shown in (2), the two test pieces of the test pieces No. 7 and 12 were cut in the middle, and the obtained measurement data also varied in an extremely wide range of 55 to 90 kg.

<Other Embodiments> The present invention is not limited to the above embodiments, but includes various other modifications. That is, in the above embodiment, the arc-shaped concave groove portion 2a is shown as the cross-section defective portion, but not limited to this,
The concave groove portion may be formed in a V shape or the like. In short, it is sufficient to form a recessed portion as the cross-section defective portion.

In the above embodiment, the bulging portion 3 has a rectangular parallelepiped shape. However, the shape is not limited to this, and the bulging portion 3 may project in the thickness direction and engage with the tip claws of the chuck pieces 8a and 9a. Anything will do.

Further, in the above-mentioned embodiment, the canvas 5 is shown as the reinforcing body of the rubber composite, but the present invention is not limited to this, and a rubber composite using a cord or the like as the reinforcing body may be used.

[0049]

As described above, according to the fatigue test method for a rubber composite in the invention described in claim 1 or the test piece in the invention described in claim 6, the rubber composite comprising a rubber body and a reinforcing body is used. 1 in the middle of the rubber body of the test piece in the longitudinal direction
Since a cross-section defective portion is provided at a location so that the repeated stress due to the elongation and compression is concentrated at the cross-sectional defective portion, the fatigue due to the loading of the repeated stress is concentrated at one specific location of the test piece extending in the longitudinal direction. Can be made. Therefore, in the measurement of the residual tensile strength of the reinforcing body, the reinforcing member can be fractured at the above-mentioned specific one position, that is, always at a fixed position, and the variation between the measured data can be significantly reduced. In addition, it is possible to directly reflect the effect of the predetermined repeated fatigue of the elongation and compression on the measured residual tensile strength, and by comparing the residual tensile strength with the tensile strength before fatigue, It is possible to perform more accurate evaluation of fatigue characteristics due to repetition.
As a result, when developing members such as reinforcements, it becomes possible to quickly and accurately determine the direction of their development, and the efficiency of research and development of the reinforcements and products of rubber composites using them. Can be realized.

According to the second or seventh aspect of the invention, the defective cross section is constituted by a concave groove portion formed so as to extend over the entire width of the rubber body in the width direction orthogonal to the longitudinal direction of the test piece. Therefore, the repetitive stress due to the expansion and the compression is concentrated to be specifically specified as the cross-section defective portion having the effect according to the invention of claim 1 or 6, and such cross-sectional defective portion can be easily formed. Can be formed.

According to the invention of claim 3 or claim 8, since the concave groove portions are formed in the rubber bodies at both sides in the thickness direction with the reinforcing body of the test piece sandwiched therebetween, they are embedded in the rubber body. It is possible to repeatedly and intensively generate strain with respect to one point in the longitudinal direction of the strengthened reinforcing body, and it is possible to provide a more suitable cross-section defect portion to be provided at one specific location in the longitudinal direction of the test piece. .

According to the invention as set forth in claim 4, the residual tensile strength of the reinforcing member is measured by gripping both end portions in the longitudinal direction of the test piece and pulling the test pieces in the direction away from each other in the longitudinal direction. It is possible to save labor in the work of taking out the embedded reinforcing body from the test piece after the repeated stress of extension and compression, and at the same time, to prevent damage or carelessness of the reinforcing body which is likely to occur during the taking out work. It is possible to reliably prevent the loading of the tensile force and the like, and to eliminate the occurrence of the variation between the measured data of the residual tensile strength due to the damage of the reinforcing body. Moreover, even if the residual tensile strength of the reinforcing body is measured not by the reinforcing body itself but by pulling the test piece embedded in the rubber body, there is a defective cross section due to repeated stress due to extension and compression. Since the strain is concentrated on the reinforcement at one specific location in the longitudinal direction, the reinforcement can be fractured at this specific location, whereby the fatigue property of the reinforcement can be accurately evaluated.

According to the invention of claim 5 or claim 9, bulging portions bulging on both sides in the thickness direction of the test piece are formed at both ends in the longitudinal direction of the test piece, and the residual tensile strength is measured. , The stepped position of each bulge is gripped by the chucks, and both chucks are moved relative to each other in the pulling direction. Therefore, even if the gripping pressure of each chuck is not so high, The grip can be reliably performed without slipping. As a result, it is possible to prevent the occurrence of slippage and the inconvenience that the test piece is cut at the chucking portion of each chuck, and it is possible to eliminate the occurrence of variations between measurement data due to the slippage and the occurrence of cutting. .

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a test piece of the present invention.

FIG. 2 is a vertical sectional view of the test piece of FIG.

FIG. 3 is a schematic explanatory view of a fatigue testing machine.

FIG. 4 is a perspective view showing a state during measurement of residual tensile strength.

5 is a perspective view of Comparative Example 1. FIG.

6 is a perspective view of Comparative Example 2. FIG.

FIG. 7 is a perspective view of Comparative Example 3 (conventional test piece).

FIG. 8 is a perspective view showing a state at the time of measuring the residual tensile strength of a conventional test piece.

FIG. 9 is a relationship diagram between each test piece and its residual tensile strength in Examples.

FIG. 10 is a relationship diagram between each test piece and its residual tensile strength in Comparative Example 1.

FIG. 11 is a relationship diagram between each test piece and its residual tensile strength in Comparative Example 2.

12 is a relationship diagram between each test piece and its residual tensile strength in Comparative Example 3. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test piece 2a Recessed groove part (cross-section missing part) 3 Bulging part 4 Rubber body 5 Canvas (reinforcement body) 8,9 Chuck

Claims (9)

[Claims] 1. A rubber composite test piece in which a reinforcing body is embedded at a middle position in the thickness direction of a rubber body so as to extend continuously in the longitudinal direction, is repeatedly stretched and compressed in the longitudinal direction, and thereafter, In a fatigue test method of a rubber composite for measuring the residual tensile strength of the reinforcing body in the longitudinal direction, the rubber body and the reinforcing body are formed so that the rubber body and the reinforcing body respectively extend in an equal cross section in the longitudinal direction. A fatigue test method for a rubber composite, characterized in that a cross-section defective portion is provided at one location in the middle of the longitudinal direction so that the repeated stress due to the elongation and compression is concentrated on the cross-sectional defective portion. 2. The rubber composite according to claim 1, wherein the cross-section defective portion is a groove portion formed so as to extend over the entire width of the rubber body in the width direction orthogonal to the longitudinal direction of the test piece. Fatigue test method. 3. The fatigue test method for a rubber composite according to claim 2, wherein the recessed groove portions are formed in the rubber bodies at both positions in the thickness direction sandwiching the reinforcing body of the test piece. 4. The rubber composite according to claim 1, wherein the residual tensile strength of the reinforcement is measured by gripping both end portions in the longitudinal direction of the test piece and pulling the test pieces away from each other in the longitudinal direction. Body fatigue test method. 5. The test piece according to claim 4, wherein bulging portions bulging to both sides in the thickness direction of the test piece are formed at both end portions in the longitudinal direction of the test piece, and the chuck is attached to each bulging portion when measuring the residual tensile strength. To engage and hold,
A method for fatigue testing a rubber composite, characterized in that both chucks are moved relative to each other in the pulling direction. 6. A rubber composite comprising a rubber body and a reinforcing body embedded in the middle position in the thickness direction of the rubber body so as to extend continuously in the longitudinal direction, and repeatedly extends and compresses in the longitudinal direction. After that, in the test piece used in the fatigue test method of the rubber composite for measuring the residual tensile strength with respect to the longitudinal direction of the reinforcing body, the rubber composite has a rubber body and a reinforcing body in the same cross section in the longitudinal direction. While the rubber composite is formed so as to extend, a cross-section defective portion is formed at one position in the middle of the rubber body in the longitudinal direction so that the repeated stress due to the expansion and compression acts in a concentrated manner. A test piece used in the fatigue test method. 7. The rubber composite according to claim 6, wherein the defective cross section is a groove formed so as to extend over the entire width of the rubber body in a width direction orthogonal to the longitudinal direction of the rubber composite. A test piece used in the fatigue test method. 8. The method for fatigue testing of a rubber composite according to claim 7, wherein the recessed groove portions are formed in the rubber bodies at both positions in the thickness direction with the reinforcing body of the rubber composite sandwiched therebetween. Test piece 9. The rubber composite according to claim 6, wherein bulging portions are formed at both ends of the rubber composite in the longitudinal direction so as to project to both sides in the thickness direction and engage with the gripping chuck. A test piece used in the body fatigue test method.