JP2012255741A - Tear testing method and apparatus for vulcanized rubber and wear resistant performance evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wear resistant performance evaluation method with which a wear resistant performance can be reproduced and evaluated with high relativeness in a short time and easily for a vulcanized rubber product such as a tire even at the laboratory level.SOLUTION: According to a wear resistant performance evaluation method of a vulcanized rubber, a test piece which has a V-shaped part with a predetermined inner angle and is notched for a predetermined length at a vertex of the inner angle, is fixed at right and left sides of a center line of the V-shaped part. The fixed parts are then allowed to respectively independently reciprocate in a X direction vertical to the centerline and a Y direction parallel thereto, thereby adding predetermined distortion to the test piece predetermined times. Thereafter, a crack growth amount grown to the notch of the test piece is measured and on the basis of the crack growth amount, a wear resistant performance of the vulcanized rubber is evaluated. In the wear resistant performance evaluation method of the vulcanized rubber, as the test piece, a notched angular test piece specified in JIS K6252 is used.

Description

  The present invention relates to a vulcanized rubber tear test method, a test apparatus therefor, and a wear resistance performance evaluation method.

  One of the characteristics required for tires is wear resistance, and tires with excellent wear resistance have a long product life. This wear resistance performance is generally evaluated by measuring the weight loss after a tire is mounted on a real vehicle and travels a predetermined distance. Specifically, the reciprocal of the weight loss is evaluated as wear characteristics, and the larger the value, the better the wear resistance performance.

  However, such a test using an actual vehicle requires a lot of time and cost and has poor test efficiency. Therefore, there is a need for a test method that can estimate and evaluate wear resistance performance more easily and in a short time at a laboratory level. It was.

  Therefore, the measurement of fracture strength and elongation using a tensile tester or the measurement of crack growth using a fatigue tester is performed, and wear resistance performance is estimated and evaluated based on the results. (For example, patent document 1).

JP-A-8-193933

  However, these methods are all methods for measuring and evaluating uniaxial deformation, and therefore have a high correlation with the actual wear characteristics affected by biaxial deformation caused by load, friction, etc. However, at the laboratory level, it was not sufficient as a method for evaluating the wear resistance performance with high correlation.

  For this reason, even at the laboratory level, there has been a demand for an abrasion resistance performance evaluation method that can reproduce and evaluate abrasion resistance performance in a short time and easily with respect to vulcanized rubber products such as tires.

The invention described in claim 1
After fixing a test piece having a V-shaped part having an inner angle of a predetermined angle and having a notch of a predetermined length at the apex of the inner angle at the left and right of the center line of the V-shaped part, After a predetermined strain is applied to the test piece a predetermined number of times by independently reciprocating the fixing portion in the X direction and the Y direction parallel to the center line,
Measure the amount of crack growth that has grown in the notch of the specimen,
A wear resistance performance evaluation method for a vulcanized rubber, characterized in that the wear resistance performance of the vulcanized rubber is evaluated based on the amount of crack growth.

The invention described in claim 2
2. The vulcanized rubber wear resistance evaluation method according to claim 1, wherein the test piece is an angled test piece with a notch defined in JIS K6252.

The invention according to claim 3
A test piece having a V-shaped portion having an inner angle of a predetermined angle and fixing test pieces each having a notch of a predetermined length at the apex of the inner angle on the left and right of the center line of the V-shaped portion. Fixing means;
A strain adding means for applying a predetermined strain to the test piece by reciprocating each of the test piece fixing means independently in the X direction perpendicular to the center line and the Y direction parallel to the center line. When,
Tear test of vulcanized rubber, comprising a crack growth amount measuring means for measuring the crack growth amount that has been torn by applying the strain a predetermined number of times and has grown into the notch of the test piece Device.

The invention according to claim 4
Using the vulcanized rubber tear test device according to claim 3,
After fixing a test piece having a V-shaped part having an inner angle of a predetermined angle and having a notch of a predetermined length at the apex of the inner angle at the left and right of the center line of the V-shaped part, After applying a predetermined strain to the test piece by independently reciprocating the fixing portion in the X direction perpendicular to the center line and the Y direction parallel to the center line,
It is a tear test method for vulcanized rubber, characterized by measuring the amount of crack growth that has grown in the notch of the test piece.

The invention described in claim 5
Using the vulcanized rubber tear test method according to claim 4, the amount of crack growth that has grown in the notch of the test piece is measured, and the wear resistance performance of the vulcanized rubber is evaluated based on the amount of crack growth. This is a method for evaluating the wear resistance performance of a vulcanized rubber.

  According to the present invention, since deformation caused by adding strain in the biaxial direction is measured and evaluated, the vulcanized rubber product such as a tire can be easily and quickly resisted even at a laboratory level. Wear performance can be reproduced with high correlation and evaluated.

It is a top view which shows typically the shape of the test piece in the tear test of one embodiment of this invention. It is a figure which shows the shape of the "angle type test piece with a cut" prescribed | regulated to JISK6252. It is a perspective view which shows the state which mounted | wore the tear test apparatus in one embodiment of this invention with the test piece. FIG. 2 is a diagram showing the “shape of a dumbbell-shaped No. 3 test piece” defined in JIS K6251. It is a front view which shows the state which mounted | wore the test piece with the uniaxial tension test apparatus. It is a figure which shows an example of the relationship between a crack growth resistance index and a wear characteristic index. It is a figure which shows an example of the relationship between a fracture | rupture ENG index | exponent and a wear characteristic index | exponent.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

[1] Tear Test First, the tear test method for vulcanized rubber according to the present invention will be described.

1. Production of Test Piece FIG. 1 is a plan view schematically showing the shape of a test piece used in the tear test of the present embodiment.

  The test piece 1 is formed by punching a plate-like vulcanized rubber having a predetermined uniform thickness into a shape shown in FIG. 1 having a V-shaped portion having an inner angle of a predetermined angle θ, and then at the apex of the inner angle. It is produced by providing a cut 1a having a predetermined length. Note that the internal angle θ is appropriately determined.

  As the test piece, it is preferable to use an “angle type test piece with a cut” defined in JIS K6252 shown in FIG. In addition, as shown in FIG. 2, the test piece 2 is provided with a cut 2a having a length of 1 mm.

2. Fixation of Test Piece and Addition of Distortion FIG. 3 is a perspective view showing a state in which the test piece is attached to the tear test apparatus in the present embodiment.

  The tear test apparatus 3 includes chucks 31a and 31b which are test piece fixing means, screw rods 32a and 32b which apply displacement in the X direction (horizontal direction in the figure) to the test piece, and the Y direction (vertical direction in the figure). Cylinder rods 33a and 33b that provide displacement in the direction) are provided.

  Then, after fixing the left and right of the center line of the test piece with an interval of L and holding it with the chucks 31a and 31b, the screw rods 32a and 32b and the cylinder rods 33a and 33b are operated independently of each other, The test piece 1 is configured to be able to freely apply biaxial strain.

  During the test, the screw rods 32a and 32b and the cylinder rods 33a and 33b are actuated on the fixed test piece 1 to add a predetermined biaxial strain, whereby the test piece is torn. , Cracks occur at the incision position and grow.

3. Measurement of Crack Growth Amount After adding a predetermined strain a predetermined number of times, the amount of crack growth grown at the cut position of the test piece is measured using an optical microscope.

[2] Wear resistance performance evaluation Next, the wear resistance performance evaluation method of the vulcanized rubber according to the present invention will be described.

  The reciprocal number of each crack growth amount obtained by the above-described tear test method is obtained to obtain the crack growth resistance in each tread rubber composition.

  This crack growth resistance is data obtained by adding strain in the biaxial direction, and the wear resistance performance is evaluated with higher correlation than the conventional method using data obtained by adding strain in the uniaxial direction. Can do.

  Next, the present invention will be described more specifically based on the following examples. In the following examples, data obtained by conducting a biaxial tear test (Example) and a uniaxial tensile test (Comparative Example) using a tread rubber composition having a predetermined composition and obtained by an actual vehicle test in advance. The correlation with the obtained wear characteristic data was evaluated.

1. Abrasion characteristics test (1) Abrasion characteristics test Using tread rubber compositions having six different compositions, tires having the same structure and the same pattern were manufactured using the same materials except for the tread rubber composition. The prepared six types of tires were mounted on an actual vehicle, and after traveling a predetermined distance (8000 km), the gauge of each tire was measured to determine the weight loss associated with actual vehicle travel.

(2) Wear characteristics The reciprocal of each gauge reduction obtained was calculated | required, and it was set as the wear characteristic in each tread rubber composition.

2. Biaxial tear test (Example)
(1) Preparation of test piece Six kinds of tread rubber compositions, which are the same as the materials used in the wear characteristic test, were newly prepared, and vulcanized rubber sheets were prepared.

  Using each vulcanized rubber sheet, six types of “angle-shaped test pieces with cuts” shown in FIG. 2 were prepared according to JIS K6252.

(2) Attaching the test piece Using the chucks 31a and 31b of the tear test apparatus shown in FIG. 3, each test piece is torn along the center line of the V-shaped portion of each test piece. Fixed to. The interval L between the two chucks when fixed was 20 mm.

(3) Addition of strain The fixed test pieces were deformed under the following conditions to add strain, and the amount of crack growth grown at the cutting position of each test piece was measured with an optical microscope. The deformation speed and displacement are relative values between the two chucks.
Deformation direction: direction indicated by an arrow in FIG. 3 Deformation speed: 50 mm / min
Displacement X direction: 20mm
Y direction: 5mm
Repeat count: 100 times

(4) Crack growth resistance The reciprocal of each obtained crack growth amount was calculated | required and it was set as the crack growth resistance in each tread rubber composition.

3. Uniaxial tensile test (comparative example)
(1) Preparation of test piece In the same manner as described above, the same six types of tread rubber compositions as those used in the wear characteristic test were newly prepared, and vulcanized rubber sheets were prepared.

  Using each vulcanized rubber sheet, six types of “dumbbell-shaped No. 3 test pieces” shown in FIG. 4 were prepared according to JIS K6251.

(2) Mounting of test piece As shown in FIG. 5, each test piece 4 was fixed using chucks 51 and 52 of a uniaxial tensile test apparatus 5.

(3) Addition of strain To each of the fixed test pieces, strain was applied by applying tension until the specimen was broken under the following conditions, and the breaking strength (TB) and elongation at break (EB) were measured. The elongation at break (EB) was calculated from the amount of deformation between the marked lines (20 mm).
Deformation direction: Uniaxial direction Deformation speed: 500 mm / min

(4) Breaking ENG (rubber strength)
Based on the obtained breaking strength (TB) and elongation at break (EB), (TB × EB) / 2 was determined and used as the breaking ENG (rubber strength) in each tread rubber composition.

4). Correlation with wear characteristics (1) Conversion to index Next, one of six tread rubber compositions was selected as a standard sample, and the wear characteristics, crack growth resistance and fracture ENG obtained above were selected. Each measured value was converted into an index with respect to the measured value of the standard sample.

(2) Evaluation of correlation Based on each converted index, a scatter diagram (FIG. 6) was created with the vertical axis representing the wear characteristic index and the horizontal axis representing the crack growth resistance index. In addition, a scatter diagram (FIG. 7) was created with the vertical axis representing the wear characteristic index and the horizontal axis representing the fracture ENG index.

  Since the correlation between each other's data can be evaluated by the correlation coefficient, the correlation coefficient of each scatter diagram was obtained.

  As a result, a high correlation coefficient of 0.76 could be obtained from the scatter diagram of FIG. 6 based on the data obtained by adding strain in the biaxial direction. On the other hand, only a correlation coefficient as low as 0.25 could be obtained from the scatter diagram of FIG. 7 based on the data obtained by adding distortion in the uniaxial direction.

  From this result, the amount of crack growth generated and grown by adding strain in the biaxial direction was measured, and the reciprocal number of this crack growth amount was regarded as crack growth resistance. It was confirmed that the actual wear characteristics could be reproduced with high correlation.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

1, 2, 4 Test piece 1a, 2a Incision 3 Tear test device 5 Uniaxial tensile test device 31a, 31b, 51, 52 Chuck 32a, 32b Screw rod 33a, 33b Cylinder rod L interval θ angle W width

Claims (5)

After fixing a test piece having a V-shaped part having an inner angle of a predetermined angle and having a notch of a predetermined length at the apex of the inner angle at the left and right of the center line of the V-shaped part, After a predetermined strain is applied to the test piece a predetermined number of times by independently reciprocating the fixing portion in the X direction and the Y direction parallel to the center line,
Measure the amount of crack growth that has grown in the notch of the specimen,
A method for evaluating the wear resistance of a vulcanized rubber, wherein the wear resistance of the vulcanized rubber is evaluated based on the amount of crack growth.   The method for evaluating wear resistance of vulcanized rubber according to claim 1, wherein the test piece is an angled test piece with a cut defined in JIS K6252. A test piece having a V-shaped portion having an inner angle of a predetermined angle and fixing test pieces each having a notch of a predetermined length at the apex of the inner angle on the left and right of the center line of the V-shaped portion. Fixing means;
A strain adding means for applying a predetermined strain to the test piece by reciprocating each of the test piece fixing means independently in the X direction perpendicular to the center line and the Y direction parallel to the center line. When,
Tear test of vulcanized rubber, comprising a crack growth amount measuring means for measuring the crack growth amount that has been torn by applying the strain a predetermined number of times and has grown into the notch of the test piece apparatus. Using the vulcanized rubber tear test device according to claim 3,
After fixing a test piece having a V-shaped part having an inner angle of a predetermined angle and having a notch of a predetermined length at the apex of the inner angle at the left and right of the center line of the V-shaped part, After applying a predetermined strain to the test piece by independently reciprocating the fixing portion in the X direction perpendicular to the center line and the Y direction parallel to the center line,
A tearing test method for vulcanized rubber, characterized by measuring the amount of crack growth grown in the notch of the test piece.   Using the vulcanized rubber tear test method according to claim 4, the amount of crack growth that has grown in the notch of the test piece is measured, and the wear resistance performance of the vulcanized rubber is evaluated based on the amount of crack growth. A method for evaluating the wear resistance of vulcanized rubber.

Images