JP6518128B2 - Rubber chipping performance evaluation method - Google Patents

Description

  The present invention relates to a method for evaluating rubber chipping resistance performance.

  For example, the tire is provided with a tread. The tire rolls when the tread touches the road surface. This tread is made of a crosslinked rubber. When the rubber is chipped in the tread, the tire can not perform sufficiently. This rubber is required to have an anti-rubber chipping property in order to fully demonstrate its performance.

  As a method of evaluating this rubber chipping resistance performance, there is, for example, a method of calculating the fracture energy of rubber. This fracture energy is calculated in accordance with JIS K6251 "Vulcanized rubber and thermoplastic rubber-Determination of tensile properties". In this method, the resistance to chipping of rubber is evaluated based on the magnitude of this breaking energy. However, in a tire, the evaluation result by this method often does not coincide with the evaluation result in a real vehicle. There is a need for a method of evaluating this rubber chipping resistance performance with high accuracy.

  JP-A-2012-251833 discloses a method for evaluating the resistance to chipping of rubber. In this method, a plurality of cuts are formed at the corners of the rubber block. The striking piece collides with this corner. Due to this collision, a rubber chip is generated in the rubber test piece. Based on the size of this rubber chipping, the rubber chipping resistance performance is evaluated. In this way, with regard to the tire, an evaluation closer to a real vehicle can be obtained as compared with the method by the destruction energy.

JP, 2012-251833, A

  In general, rubber having large elastic deformation is excellent in rubber chipping resistance performance. In a rubber block made of such rubber, the impact is dispersed by elastic deformation of the entire rubber block. With such a rubber block, rubber chipping is less likely to occur by the method of JP-A-2012-251833. With such a rubber block, it is difficult to evaluate the resistance to rubber chipping with high accuracy.

  FIG. 5 is an explanatory view of another method for evaluating the rubber chipping resistance performance. This method is a method created by the inventors. In this method, a rubber block 1 is prepared. A metal impact plate 2 is embedded in the rubber block 1. The striking piece 3 collides with the rubber block 1. The impact due to the collision acts on the rubber portion between the front surface 4 of the rubber block 1 and the impact plate 2 in a concentrated manner. Thereby, even if it is rubber | gum to which elastic deformation is large, rubber chipping generate | occur | produces comparatively easily. According to this method, even if the rubber block 1 has large elastic deformation, the rubber chipping resistance can be evaluated. On the other hand, in the case of a high hardness rubber having a small elastic deformation, rubber chips occur in any case. This method is not suitable for the evaluation of high hardness rubbers with small elastic deformation. With a rubber block made of high-hardness rubber with small elastic deformation, it is difficult to evaluate the resistance to rubber chipping with high accuracy.

  In addition, in the tire, rubber chipping may occur due to repeated collisions with relatively small input. It is difficult for the evaluation method of Unexamined-Japanese-Patent No. 2012-251833 and the evaluation method shown in FIG. 5 to evaluate the rubber chipping which arises by repetition collision with such comparatively small input.

  An object of the present invention is to provide a method for evaluating the resistance to chipping of rubber which can make a near-vehicle evaluation with high accuracy.

  The evaluation method of the rubber chipping resistance performance according to the present invention comprises a test piece preparation step, a test step and an evaluation step. In the test piece preparation process, rubber test pieces are prepared. This rubber test piece comprises a main body. The body is provided with a front facing front. In this test process, the impacting piece repeatedly strikes the front surface of the rubber test piece to cause the rubber test piece to crack. In this evaluation process, the number of collisions between the impacting piece and the rubber test piece is required until the rubber test piece is cracked. The rubber chipping resistance performance of the rubber test piece is evaluated based on the number of collisions.

  Preferably, the rubber test piece comprises a base. The base forms an upper surface of the base facing upwards. The main body protrudes upward from the upper surface of the base. The front surface and the base upper surface of the main body extend in a crossing direction. A corner is formed at the boundary between the front surface of the main body and the upper surface of the base.

  Preferably, in the test step, the rubber test piece is fixed by fixing the base of the rubber test piece.

  Preferably, in the test step, a pendulum tester provided with the impacting piece is prepared. This pendulum tester includes an arm whose one end is pivotally supported by a horizontal rotation shaft and whose other end is rotatable, and a support. The striking piece is attached to the other end of the arm. The support fixes the rubber test piece with the front surface of the rubber test piece parallel to the pivot axis of the arm. The collision in the test step is performed below the pivot.

  Preferably, the impacting piece is provided with an abutment surface that collides with the front surface of the rubber test piece. The contour of the contact surface is arc-shaped in the cross section of the striking piece parallel to the direction in which the striking pieces collide and perpendicular to the front surface.

  Preferably, the rubber test piece is made of tire rubber.

  In the evaluation method of the rubber chipping resistance performance according to the present invention, the impacting piece collides multiple times until the rubber test piece is cracked. According to this method, the rubber chipping resistance performance can be evaluated with high accuracy by the number of collisions until the crack is generated. In addition, rubber chipping caused by repeated collisions can be properly evaluated with small input. According to this method, in a tire, rubber chipping resistance performance close to a real vehicle can be evaluated.

FIG. 1 is a front view showing a pendulum tester used in an evaluation method according to an embodiment of the present invention together with a rubber test piece. FIG. 2 is a perspective view showing a state of use of the tester of FIG. FIG. 3 is an explanatory view of an evaluation method using the tester of FIG. FIG. 4 is a cross-sectional view of a tire suitable for evaluation by an evaluation method according to an embodiment of the present invention. FIG. 5 is an explanatory view of the evaluation method of the comparison test.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

  A pendulum tester 12 is shown in FIG. 1 as a test apparatus used for this evaluation method. Here, the left-right direction in FIG. 1 is referred to as the front-rear direction, the direction perpendicular to the sheet of FIG. 1 is referred to as the left-right direction, and the up-down direction in FIG. The right direction in FIG. 1 is forward, and the left direction is backward.

  The pendulum tester 12 includes a base 14, a support 16, a support 18, a support shaft 20, a display 22, an arm 24, a weight 26 and a striking piece 28. A rubber test piece 30 is shown together with a pendulum tester 12 in FIG.

  The base 14 is installed on the floor 32. The support 16 is attached to the base 14. For example, a so-called vise is used as the support 16. The support 16 is not limited to a vise, as long as the rubber test piece 30 can be fixed. The support 16 only needs to be fixed so that the rubber test piece 30 does not move relative to the base 14 when the impacting piece 28 collides with the rubber test piece 30.

  The support 18 extends upward from the base 14. A support shaft 20 is fixed to an upper portion of the support 18. The support shaft 20 extends in the horizontal direction. The support shaft 20 extends in the left-right direction perpendicularly to the front-rear direction. The display unit 22 is fixed to the support 18. The display unit 22 displays an angle about the axis of the support shaft 20. The angle of the display unit 22 is 0 ° vertically downward from the axis of the support shaft 20, and is 90 ° horizontally forward and backward from the axis of the support shaft 20.

  One end of the arm 24 is pivotally supported by the support shaft 20. The other end of the arm 24 is pivotable with the support shaft 20 as a pivot. The angle of the display 22 described above represents the swing-up angle of the pivoting arm 24. The swing-up angle of the arm 24 shown by the solid line in FIG. 1 is 60 °. A weight 26 is attached to the other end 33 of the arm 24. The striking piece 28 is attached to the weight 26. The weight of the weight portion 26 is adjustable.

  As shown in FIG. 1 and FIG. 2, the striking piece 28 is located at one end of the weight portion 26. The striking piece 28 has a cylindrical shape. The axis of the striking piece 28 extends in the left-right direction. The axis of the striking piece 28 is parallel to the axis of the support shaft 20. The striking piece 28 has a circular cross-sectional shape in a cross section perpendicular to its axis. In a cross section perpendicular to the support shaft 20, the striking piece 28 has a circular cross-sectional shape. The striking piece 28 is made of a hard material having a large specific gravity. The striking piece 28 is made of, for example, metal.

  The impacting piece 28 is provided with an abutment surface 35 that collides with the rubber test piece 30. The abutment surface 30 exhibits a smooth curve in a cross section perpendicular to the support shaft 20. The contact surface 30 projects toward the rubber test piece 30. In the striking piece 28, the abutment surface 30 is formed in an arc shape in a cross section perpendicular to the support shaft 20.

  The rubber test piece 30 comprises a base 34 and a body 36. The base 34 includes a base upper surface 38. The upper base surface 38 faces upward. The base upper surface 38 is formed in a horizontal plane. The main body 36 is formed to project upward from the base 34. The main body 36 is formed to project upward from the base upper surface 38.

  The main body 36 has a substantially rectangular parallelepiped shape. The main body 36 includes a front surface 40, a rear surface 42, an upper surface 44, a right side 46 and a left side 48. The front surface 40 faces the front, the rear surface 42 the rear, the upper surface 44 the upper, the right side 46 the right, and the left side 48 the left.

  A corner 49 is formed at the boundary between the front surface 40 and the base upper surface 38. The corner 49 is formed by the intersection of the front surface 40 and the base upper surface 38. The corner 49 is recessed inside the rubber test piece 30. The corner 49 is a recess. The corner 49 is continuous with the front surface 40 and the base upper surface 38. In the rubber test piece 30, the front surface 40 and the base upper surface 38 are orthogonal to each other. The corner angle formed by the front surface 40 and the base upper surface 38 is 90 °. In the rubber test piece 30, a corner is formed at the boundary between the rear surface 42 and the base upper surface 38. The corner angle formed by the rear surface 42 and the base upper surface 38 is 90 °. The right side 46 and the left side 48 are formed on the same plane as the side of the base. The right side surface 46 and the left side surface 48 may extend upward from the base upper surface 38 to form a corner at the boundary between the right side surface 46 and the left side 48 and the base upper surface 38.

  FIG. 3A shows a state at the moment when the impacting piece 28 collides with the rubber test piece 30. Arrow R in FIG. 3A represents the radius of curvature of the contact surface 35. In FIG. 3 (b), a state in which the rubber test piece 30 is elastically deformed due to the collision of the striking piece 28 is shown.

  The evaluation method of the rubber chipping resistance performance according to the present invention will be described by taking the pendulum tester 12 and the rubber test piece 30 as an example. This evaluation method comprises a test piece preparation step, a test step and an evaluation step.

  In the test piece preparation step, a rubber test piece 30 is prepared. The rubber test piece 30 is made of the cross-linked rubber of the tread of the tire. The rubber test piece 30 is preheated. For example, the rubber test piece 30 is heated to a temperature of 60 ° C. in the test process. By this heating, the rubber test piece 30 is easily cracked. By this heating, rubber chipping resistance performance close to that of a real vehicle can be evaluated. From this point of view, preferably, in the test step, the temperature of the rubber test piece 30 is higher than normal temperature. This temperature is, for example, 40 ° C. or higher. This temperature is, for example, 150 ° C. or less.

  In the test process, a pendulum tester 12 is prepared. A rubber test piece 30 is attached to the pendulum tester 12. The base 34 of the rubber test piece 30 is fixed by the support 16. The rubber test piece 30 is fixed to the base 14. In the fixed rubber test piece 30, the front surface 40 is parallel to the axis of the support shaft 20. The front face 40 is directed forward.

  The striking piece 28 is pivoted counterclockwise. The striking piece 28 is swung forward and upward. The arm 24 is swung up to a predetermined swinging angle. For example, the arm 24 is swung up to a position of a swing angle of 90 °. The support of the arm 24 is released. The gravity causes the arm 24, the weight 26 and the striking piece 28 to rotate clockwise.

  The striking piece 28 collides with the front face 40 of the rubber test piece 30 at a position where the swing-up angle of the arm 24 is 0 °. The striking piece 28 may collide with the front surface 40 of the rubber test piece 30 at a position where the swing-up angle of the arm 24 is around 0 °. For example, the striking piece 28 may collide with the rubber test piece 30 at a position shown by a two-dot chain line in FIG. 1. The position where the swing-up angle of the arm 24 is around 0 ° means the position moved within 6 mm in the front-rear direction with reference to the position of the other end 33 of the arm 24 when the swing-up angle of the arm 24 is 0 ° doing.

  The impacting piece 28 collides with the rubber test piece 30 to reach the state of FIG. 3 (a). The potential energy of the arm 24, the weight portion 26 and the striking piece 28 is converted into kinetic energy by being in the state of FIG. The kinetic energy causes the rubber test piece 30 to be elastically deformed. Since the base 34 is fixed by the support 16, the main body 36 is mainly elastically deformed. Thus, the state shown in FIG. 3 (b) is reached.

  The elastically deformed rubber test piece 30 pushes back the arm 24, the weight portion 26 and the striking piece 28 in the counterclockwise direction. The pushed back arm 24, the weight 26 and the striking piece 28 rotate clockwise again by gravity. The striking piece 28 collides with the rubber test piece 30 again. Thereby, the rubber test piece 30 is deformed. Thus, the striking piece 28 repeats the clockwise and counterclockwise motions. The rubber test piece 30 repeats deformation. The impacting piece 28 and the rubber test piece 30 repeatedly collide. Soon, the striking piece 28 stops at a position where the swing-up angle of the arm 24 is 0 ° or this angle is around 0 °.

  Thus, from the state in which the arm 24 is set to the predetermined swing-up angle to the stop of the striking piece 28 is one striking cycle. Several collisions are repeated in this one striking cycle. This striking cycle is repeated multiple times. This striking cycle is repeated until it is confirmed that the rubber test piece 30 is cracked. In this test process, when a crack occurs in the rubber test piece 30, this impacting cycle ends.

  In the evaluation process, the number of collisions between the impacting piece 28 and the rubber test piece 30 is counted until the rubber test piece 30 is cracked. The crack grows on the rubber test piece 30 due to the growth of the crack. The ease of occurrence of the crack indicates the ease of occurrence of rubber chipping. The greater the number of collisions, the better the rubber test piece 30 is in the resistance to chipping of rubber. As the number of collisions is smaller, the rubber test piece 30 is inferior in rubber chipping resistance performance. The rubber chipping resistance performance of the rubber test piece 30 is evaluated based on the number of collisions.

  In the method of the present invention, the number of collisions until the occurrence of a crack is counted. The rubber chipping resistance performance can be objectively evaluated compared to the method of evaluating the rubber chipping resistance performance based on the size of the rubber chipping. Also, the tendency of rubber chipping to occur does not necessarily correlate with the size of rubber chipping. According to the method of the present invention, the likelihood of rubber chipping can be evaluated with high accuracy. This method, in particular, accurately evaluates rubber chipping caused by repeated impacts with small inputs. Although the number of collisions is summarized here, the number of impact cycles may be aggregated instead of the number of collisions. The rubber chipping resistance performance may be evaluated based on the number of impact cycles instead of the number of collisions.

  In this test process, the input is adjusted to such an extent that the rubber test piece 30 does not crack in one collision. This input can be adjusted, for example, by the shape of the rubber test piece 30, the collision speed of the striking piece 28, the swing-up angle of the arm 24, and the mass of the weight portion 26 and the striking piece 28. For example, the impact velocity of the striking piece 28 is preferably 0.1 m / sec or more, and more preferably 1 m / sec or more. The collision velocity is preferably 3 m / sec or less. The collision velocity can be calculated as all potential energy is converted to kinetic energy.

  Since the pendulum tester 12 is used, kinetic energy can be easily calculated from potential energy. In addition, by using the pendulum tester 12, the rubber chipping resistance performance can be evaluated under certain conditions regardless of the place or time. By using the pendulum tester 12, the rubber chipping resistance performance of a plurality of rubbers can be compared and evaluated easily and with high accuracy.

  In the rubber test piece 30, the main body 36 protrudes from the base 34. The base 34 is fixed to the support 16. The striking piece 28 collides with the front surface 40 of the main body 36. This causes stress concentration at the corner 49. The rubber test piece 30 is easily cracked at the corner 49. The rubber test piece 30 has a shape in which the occurrence of cracks tends to be concentrated at the corner 49. With this rubber test piece 30, the occurrence of cracks is easy to confirm.

  As shown in FIG. 3, the abutment surface 35 of the striking piece 28 collides with the front surface 40. Since the contact surface 35 is formed in an arc shape, stress concentration at the collision point is suppressed. As a result, the location of the crack is concentrated at the corner 49. From this point of view, the contact surface of the striking piece 28 is preferably formed as a smooth curve in cross section. The smooth curve may be a combination of a plurality of arcs. The minimum curvature radius R of this smooth curve is preferably 5 mm or more, more preferably 10 mm or more.

  High hardness rubber has a small amount of elastic deformation. Such rubber is prone to plastic deformation. Rubber that has undergone plastic deformation is broken by repeated collisions. For example, a high hardness rubber can be obtained by being filled with a resin filler or a metal filler. In such rubber, although the amount of elastic deformation is small, plastic deformation occurs due to repeated collisions. The evaluation method of the present invention is also suitable for the evaluation of the rubber chipping resistance performance of such rubber.

  FIG. 4 shows a cross section of a motorcycle tire 50 traveling on uneven terrain such as a forest, wilderness and the like. The alternate long and short dash line CL in FIG. 4 represents the equatorial plane. The shape of the tire 50 is substantially symmetrical with respect to the equatorial plane. The tread 52 has a radially outward convex shape. The tread 52 has a large number of blocks 54 which rise substantially radially outward. A groove 56 is formed between one block 54 and the other block 54. In the tire 50, the adjacent blocks 54 are separated by the groove 56 in the axial direction and the circumferential direction. The blocks 54 are independent in the axial direction and in the circumferential direction.

  In this tire 50, the treads 58 of the blocks 54 independent of each other are in contact with the road surface. The edge effect of the tread 58 provides high traction performance. Due to this block 54, the tire 50 exhibits high running performance on uneven terrain.

  On rough terrain, the road surface is rough. A motorcycle traveling on rough terrain repeats jumping and landing. This block 54 repeats the collision with the road surface. Due to this collision, in the tire 50, a crack is likely to occur at the base 60 of the block 54. This crack may grow and cause a crack in the block 54. By the evaluation method of the present invention, the rubber chipping resistance performance of the tire 50 can be evaluated with high accuracy.

  From the viewpoint of evaluating the rubber chipping performance of the tire 50 with high accuracy, the rubber test piece 30 preferably includes a main body 36 projecting upward from the base upper surface 38. Preferably, the body 36 comprises a front side 40, a rear side 42, a right side 46 and a left side 48 extending upwardly from the base top surface 38.

  The corner 49 between the base upper surface 38 and the front surface 40 of the rubber test piece 30 may be a smooth curved surface continuous with the base upper surface 38 and the front surface 40. The corner angle between the front surface 40 and the base top surface 38 may be an angle greater than 90 °. The corner between the rear surface 42 and the base upper surface 38 may be a smooth curved surface that is continuous with the base upper surface 38. Corners may be similarly formed between the right side surface 46 and the left side surface 48 and the base upper surface 38. The body 36 may be shaped as a block 54. Thereby, the rubber chipping resistance performance of the tire 50 can be more accurately evaluated. Furthermore, by evaluating the main body of the rubber test piece 30 into various block shapes and evaluating them, the shape of the block 54 which is excellent in rubber chipping resistance performance can be evaluated.

  According to this method, rubber chipping performance can be evaluated by producing the rubber test piece 30 without producing a prototype tire. By using this method, it is possible to evaluate the rubber chipping resistance performance close to a real vehicle with high accuracy.

  In the present invention, the dimensions and angles of each member of the tire are measured in a state where the tire is incorporated into a regular rim and the tire is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire. In the present specification, the normal rim means the rim defined in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims. The normal internal pressure as used herein means the internal pressure defined in the standard on which the tire is based. The “maximum air pressure” in the JATMA standard, the “maximum value” published in the “TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES” in the TRA standard, and the “INFLATION PRESSURE” in the ETRTO standard are normal internal pressure.

  Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be interpreted in a limited manner based on the description of the examples.

  In this example, four rubbers A, B, C and D were prepared. These were obtained from the rubber compositions of the formulations shown in Table 1 below. These were obtained by kneading and vulcanizing this rubber composition. These rubber compositions were compounded in parts by mass shown in Table 1.

  Polymer 1 in Table 1 is a natural rubber "TSR20". The polymer 2 is a styrene butadiene rubber ("SBR1502" manufactured by JSR). Carbon is "Diablack I (N220, ISAF class)" manufactured by Mitsubishi Chemical Corporation. Wax is "Ozo Ace 0355" manufactured by Nippon Seiwa. The anti-aging agent is "NOCLAK 6C" manufactured by Ouchi Emerging Chemical Industry. Zinc oxide is manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid is "beads stearic acid camellia" made by NOF Corporation. The oil is "Process X-260" manufactured by Japan Energy. Sulfur is powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. The vulcanization accelerator is "NOCSELER NS" manufactured by Ouchi New Chemical. The thermoplastic resin is "ESCLON V120 (Coumarone-indene resin, softening point 120 ° C)" manufactured by Nippon Steel Chemical Co., Ltd. The thermosetting resin is Sumitomo Bakelite “PR12686”. The amine promoter is "Noxceler HMT" manufactured by Ouchi Shining Chemical Industry.

[Comparison test 1]
The breaking energy of the rubbers A, B, C and D is determined. This fracture energy is determined in accordance with the provisions of "JIS K6251" for "vulcanized rubber and thermoplastic rubber-determination of tensile properties". Specifically, dumbbell-shaped test pieces are produced from these rubber compositions. The tensile strength (TB) and the elongation at break (EB) of this dumbbell-shaped test piece are measured. From the tensile strength (TB) and the elongation at break (EB), the fracture energy Et is determined by the following equation. The results are shown in Table 2 as an index where rubber A is 100. The larger the index, the higher the rubber chipping performance.
Et = (TB) · (EB) / 2

[Comparison test 2]
The rubber chipping performance of the rubbers A, B, C and D was evaluated by the method of evaluating the rubber chipping resistance shown in FIG. Specifically, rubber blocks were made from these rubber compositions. A metal impact plate was embedded in this rubber block to obtain a block test piece. The impacting piece of FIG. 5 collided with the front surface of this block test piece, and the presence or absence of a rubber chip was confirmed. The results are shown in Table 2. The results are shown in Table 2 as an index where rubber A is 100. In this case, rubber blowout occurred in one shot, and no clear difference could not be confirmed.

[test]
Rubber test pieces consisting of the pendulum tester shown in FIGS. 1 and 2 and rubbers A, B, C and D were prepared. These rubber test pieces had the shapes shown in FIGS. 1 and 2. The rubber chipping resistance performance of the rubber test pieces A, B, C and D was evaluated. The results are shown in Table 2. The results are shown in Table 2 as an index with the rubber test piece A as 100. The larger the index, the higher the rubber chipping performance.

[Vehicle evaluation]
A motorcycle tire (a motocross tire) shown in FIG. 4 was produced. Tires were produced whose treads consisted of rubbers A, B, C and D, respectively. The tire size was "120 / 90-19 66M". I mounted each tire on a motorcycle for motocross and ran on the motocross course. This motocross course includes hoops which are a continuous uneven road surface. After traveling on this motocross course, the size and number of tread defects were counted. Rubber chipping resistance was evaluated based on the size and number of chips. The results are shown in Table 2. The result is the order in relative comparison, and the smaller the number, the better the resistance to chipping of rubber. In this on-vehicle evaluation, the rubber of the rubber test piece C was the best, and the rubber of the rubber test piece A was the inferior.

  As shown in Table 2, the results of the tests according to the method of the invention are closest to the results of the real vehicle evaluation. The superiority of the present invention is clear from the evaluation results.

  The method described above can be widely applied as a method for evaluating rubber chipping resistance performance. In particular, it is suitable for evaluation of the rubber chipping resistance of rubber due to repeated collisions. In a tire in which a block stands on a tread and this block forms a tread, the rubber chipping resistance performance of the tread rubber can be evaluated with high accuracy. This method is suitable, for example, for evaluating tread rubbers for motocross tires and industrial tires.

12: Pendulum tester 14: Base 16: Support 20: Support shaft 28: Impacting piece 30: Rubber test piece 34: Base 36: Main body 38 ... Base upper surface 40 ... front 50 ... tire 52 ... tread 54 ... block 56 ... groove 58 ... tread surface

Claims (5)

Test specimen preparation process, test process and evaluation process
In this test piece preparation process, rubber test pieces are prepared,
The rubber test piece comprises a body, the body comprising a front surface facing forward,
In this test process, the impacting piece repeatedly strikes the front surface of the rubber test piece, causing the rubber test piece to crack,
In this evaluation process, the number of collisions between the impacting piece and the rubber test piece until cracking occurs in the rubber test piece is determined, and the rubber chipping resistance performance of the rubber test piece is evaluated based on the number of collisions,
This rubber test piece consists of rubber for tires , The evaluation method of the rubber chipping resistance performance. The rubber test piece has a base,
The base forms an upper surface of the base facing upwards,
The main body protrudes upward from the upper surface of the base,
The evaluation method according to claim 1, wherein the front surface of the main body and the upper surface of the base extend in the intersecting direction, and a corner is formed at the boundary between the front surface of the main body and the upper surface of the base.   The evaluation method according to claim 2, wherein in the test step, the rubber test piece is fixed by fixing a base of the rubber test piece. In the above test process, a pendulum type testing machine provided with the above impact piece is prepared,
The pendulum tester includes an arm whose one end is pivotally supported by a horizontal rotation shaft and whose other end is rotatable, and a support.
This striking piece is attached to the other end of the arm,
The support fixes the rubber test piece with the front surface of the rubber test piece parallel to the pivot axis of the arm,
The evaluation method according to any one of claims 1 to 3, wherein the collision in the test step is performed below the pivot shaft. The impacting piece is provided with an abutting surface that collides with the front surface of the rubber test piece,
The evaluation method according to any one of claims 1 to 4, wherein the contour of the contact surface is arc-shaped in a cross section of the striking piece which is parallel to a direction in which the striking pieces collide and perpendicular to the front surface.

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