Methods for assessing rubber abrasion resistance

Abstract

Methods for assessing rubber abrasion resistance, including: Applying an additional force directed towards a circular circumferential surface of a rotating body, which is turned by a drive motor towards a rubber test specimen, thereby compressing the test specimen and bonding it to the circular circumferential surface in a predetermined fixed position; Holding the test specimen in a state in which movement of the test specimen in one direction against the additional force is always possible; performing an abrasion test in which a contact surface of the test specimen with the circular circumferential surface is worn away; and Assessing the abrasion resistance of the test specimen based on at least one of two elements, including the power required to drive and rotate the drive motor during the abrasion test, and the temperature of the test specimen, in addition to the degree of abrasion of the test specimen. the method further includes calculating a generation cycle of a stick-slip phenomenon occurring in the test specimen based on fluctuations in performance and evaluating the abrasion resistance of the test specimen based on a quantity of the generation cycle.

Description

Technical area

[0001] The present invention relates to a method for evaluating rubber abrasion resistance, particularly to a method for evaluating rubber abrasion resistance that ensures evaluation with high reliability. State of the art

[0002] State-of-the-art testing devices for evaluating rubber abrasion resistance include a DIN abrasion tester and a Williams abrasion tester. These abrasion testers generally evaluate abrasion resistance based on the degree of abrasion experienced by the rubber in tests.

[0003] As another method for evaluating rubber abrasion resistance, for example, a method has been proposed that causes abrasion on a rubber test piece by pressing a peripheral surface of a rotating rubber test piece against a peripheral surface of a rotating grindstone to evaluate the tread rubber of a tire (see Patent Document 1). With this proposed method, tests can be performed under conditions close to actual tires by changing the torque, thereby causing the test piece to rotate in a desired pattern or the like. Patent Document 2 discloses a method for testing the durability of indoor tires. A tire durability test is performed by measuring the internal tire temperature of a test tire and comparing it with a structurally identical tire.Patent Document 3 discloses a method for evaluating a surface structure of a plastic material, comprising measuring the degree of wear of a plastic material by a metal material through a friction test and evaluating a higher-order structure of the surface of the plastic material based on the wear amount. The friction test is performed in a surface contact mode in which an end surface of a cylinder is pressed against a flat test piece. Patent Document 4 discloses a rubber wear testing device consisting of an abrasion machine body, a temperature regulating device, a speed regulating device, an angle regulating device, and a temperature detecting device.

[0004] However, the current evaluation method focuses on only one evaluation object, such as abrasion degree, to assess abrasion resistance. Therefore, in some cases, rubber abrasion resistance cannot be adequately assessed using only the individual evaluation object. Accordingly, there is room for improvement to conduct a more reliable evaluation. List of citationsPatent literature Patent document 1: JP 2008 - 185 475 A Patent document 2: JP 2004 - 37 286 A Patent document 3: JP 2013 - 178 163 A Patent Document 4: CN 2 01 004 038 Y Summary of the inventionTechnical problem

[0005] It is an object of the present invention to provide a method for evaluating rubber abrasion resistance which ensures evaluation with high reliability. Solution to the problem

[0006] To achieve the above-mentioned object, a method for evaluating rubber abrasion resistance according to the present invention includes applying an additional force directed to a circular peripheral surface of a rotating body rotated by a drive motor to a rubber test specimen, thereby compressing and adhering the test specimen to the circular peripheral surface in a predetermined fixed position, holding the test specimen in a state in which movement of the test specimen in a direction opposite to the additional force is always permitted, conducting an abrasion test in which a contact surface of the test specimen with the circular peripheral surface is worn, and evaluating the abrasion resistance of the test specimen based on at least one of two elements,including the power required to drive and rotate the drive motor during the abrasion test and a temperature of the test piece in addition to an abrasion degree of the test piece, the method further comprising calculating a generation cycle of a stick-slip phenomenon occurring in the test piece based on fluctuation in the power, and evaluating the abrasion resistance of the test piece based on a size of the generation cycle. Advantageous effects of the invention

[0007] According to the present invention, when conducting the above-mentioned abrasion test for evaluating the abrasion resistance of the test piece, evaluation indices based on not only the abrasion degree of the test piece but also at least one of two elements including the power required to drive and rotate the drive motor during the abrasion test and the temperature of the test piece during the abrasion test are used, so that the evaluation can be performed with high reliability without excessively depending on data on the abrasion degree. Brief description of the drawings Fig. 1 is an explanatory diagram showing, by way of example, a test apparatus for evaluating rubber abrasion resistance in a front view according to the present invention. Fig. 2 is an explanatory diagram showing a part of the test device in Fig. 1 in top view. Fig. 3 is an explanatory diagram illustrating a stick-slip phenomenon. Fig. 4 is a graph illustrating a relationship between an abrasion degree of a test specimen and an additional force in a case where a peripheral speed of a circular peripheral surface of a rotating body is a certain predetermined speed. Fig. Fig. 5 is a graph illustrating a relationship between an abrasion degree of a test piece and an additional force in a case where a peripheral speed of a circular peripheral surface is three times that of Fig. 3. Fig. Figure 6 is a graph illustrating a relationship between an abrasion degree and an apparent friction energy. Fig. 7 is a graph illustrating a relationship between a peripheral speed of a circular peripheral surface and the power of a driving motor and a sliding friction coefficient of a test specimen. Fig. Figure 8 is a graph illustrating power fluctuations of a drive motor. Fig. Figure 9 is a graph illustrating a temperature change of a test specimen. Description of embodiments

[0008] Hereinafter, a method for evaluating rubber abrasion resistance according to the present invention will be described based on embodiments illustrated in drawings.

[0009] In the present invention, a Fig. 1 and Fig. 2 is used. In the testing apparatus 1, a test specimen S of rubber to be tested uses a block-shaped mass or the like, not a ring-shaped body. The testing apparatus 1 includes a holding section 3 for holding the test specimen S, a rotating body 4, a drive motor 5 for driving and rotating the rotating body 4, and a pressure connection mechanism 10. Further, the testing apparatus 1 includes a dynamometer 6a, a temperature sensor 6b, a camera 6c, a control unit 7, a temperature control mechanism 8, and a scraper 16, and the elements except for the dynamometer 6a and the control unit 7 are covered with a case 2a installed on a base 2.

[0010] The holding section 3 detachably holds the test piece S. The number of holding sections 3 is not limited to one, and a plurality of holding sections 3 may be provided.

[0011] The rotating body 4 is a columnar or cylindrical grinding wheel and includes a circular peripheral surface 4a that is in contact with the test piece S. The circular peripheral surface 4a serves as a grinding surface relative to the test piece S. The rotating body 4 is rotatable about a rotating shaft 4b provided in its circular center.

[0012] Regarding a material or surface roughness of the circular peripheral surface 4a, or the like, appropriate specifications are selected based on inspection conditions. For example, a plurality of rotating bodies 4, each of which has a different specification, are prepared, and the rotating bodies 4 are configured to be replaced according to the specification of a required circular peripheral surface 4a. Alternatively, the rotating body 4 may be provided such that only the circular peripheral surface 4a needs to be replaced. In this case, the circular peripheral surface 4a corresponding to a required specification is attached to the core of the rotating body 4.

[0013] The drive motor 5 is connected to the control unit 7. The rotational speed of the rotating body 4 (rotating shaft 4b) is controlled by the control unit 7 to a desired speed. The outer diameter of the rotating body 4 is known, and thus, a peripheral speed V of the circular peripheral surface 4a is calculated in the control unit 7. In this embodiment, the drive motor 5 and the control unit 7 are connected via the dynamometer 6a. The dynamometer 6a measures the power W of the drive motor 5 required to drive and rotate the rotating body 4. Measurement data from the dynamometer 6a is input to and stored in the control unit 7.

[0014] The pressure-bonding mechanism 10 applies an additional force F, directed toward the circular peripheral surface 4a, to the test specimen S held by the holding portion 3. This causes the test specimen S held by the holding portion 3 to be compressed and adhered to the circular peripheral surface 4a in a predetermined fixed position relative to the driven and rotated rotating body 4. Furthermore, the pressure-bonding mechanism 10 is configured to allow the test specimen S to move in a direction opposite to the additional force F at any time.

[0015] Specifically, the pressure connection mechanism 10 of the present embodiment consists of an L-shaped support arm 11a coupled to the support portion 3, a wire 12 having one end connected to the support arm 11a, and a weight 15 connected to the other end of the wire 12. A support shaft 14 arranged parallel to the rotating shaft 4b of the rotating body 4 penetrates a support column 11, which is installed vertically on the base 2 and rotatably supported. The support arm 11a is fixed to one end portion of the support shaft 14, and a balancer 13 is fixed to the other end portion.

[0016] The weight of the weight 15 acts on the holding arm 11a via the wire 12. Thus, the holding section 3 integrated into the holding arm 11a rotates with the test piece S around the support shaft 14 due to the tension of the wire 12. This means that the weight of the weight 15 acts on the test piece S held by the holding section 3 and thereby applies the additional force F directed onto the circular peripheral surface 4a to the test piece S.

[0017] The magnitude of the additional force F can be easily changed by varying the weight of weight 15. Alternatively, the magnitude of the additional force F can be changed by varying a horizontal distance between the support shaft 14 and the connection position of the wire 12 with respect to the support arm 11a, or by varying the weight of a balance member 13. Further, the balance member 13 can be installed so that the additional force F reaches zero in a state where the weight 15 is removed. For example, the weight of the balance member 13 and a distance from the support shaft 14 are selected so that the dead weight of the pressure connection mechanism 10 cancels out in a state where the weight 15 is removed, thereby causing the additional force F to reach zero.The weight of weight 15 and the additional force F can be balanced by installing the balancing member 13 so that the additional force F reaches zero in a state where the weight 15 is removed and by balancing a distance between the test piece S and the support shaft 14 with a distance between the support shaft 14 and the connecting position of the wire 12 with respect to the holding arm 11a.

[0018] The surface of the test specimen S opposite the circular peripheral surface 4a is brought into a state where it is pressed against and in contact with the circular peripheral surface 4a by the additional force F (specified load) with a constant magnitude at all times. It is preferable that the direction of the additional force F be set to a direction aligned with the rotation center (rotating shaft 4b) of the rotating body 4. With this direction, the test specimen S can be stably pressed by the additional force F and be in contact with the circular peripheral surface 4a. To facilitate the smooth rotation of the support arm 11a around the support shaft 14, the support shaft 14 can be supported by the support column 11 through a bearing, for example.

[0019] In this document, the test piece S is simply pressed against the circular peripheral surface 4a based on the weight of weight 15. Thus, the support arm 11a rotates around the support shaft 14, allowing the test piece S to move in the opposite direction to the additional force F at any time. In addition, when the force in the opposite direction to the additional force F acts on the test piece S, the test piece S can move in the direction in which the test piece S separates from the circular peripheral surface 4a.

[0020] The pressure-bonding mechanism 10 is not limited to the configuration illustrated in the embodiment. Various configurations can be used as long as the pressure-bonding mechanism 10 has the configuration in which the additional force F directed toward the circular peripheral surface 4a is applied to the specimen S held by the holding portion 3, thereby compressing and adhering it to the circular peripheral surface 4a in a predetermined fixed position, and the movement of the specimen S in the opposite direction to the additional force F is always possible.

[0021] In this embodiment, the test piece S is in contact with the circular peripheral surface 4a at the same position as the rotating shaft 4b in the horizontal plane, but the position (position in the circumferential direction of the rotating body 4) where the test piece S is in contact with the circular peripheral surface 4a is not limited to this. For example, a configuration may be adopted in which the test piece S is in contact with the circular peripheral surface 4a at a position above the rotating shaft 4b. Thus, a predetermined fixed position in which the test piece S is pressed and adhered to the circular peripheral surface 4a can be set appropriately.

[0022] The temperature sensor 6b detects a temperature T of the test object S. The detection data of the temperature sensor 6b is input to the control unit 7 and stored. The camera 6c takes a photo of the movement of the test object S, and the photographed video data is input to the control unit 7 and stored.

[0023] The temperature control mechanism 8 adjusts the test piece S to a predetermined temperature. In this embodiment, many elements (components), except for the dynamometer 6a and the control unit 7, are covered by the housing 2a installed on the base 2. The temperature control mechanism 8 is provided on the surface of the housing 2a. The internal temperature of the housing 2a is adjusted to a predetermined temperature by the temperature control mechanism 8, which indirectly adjusts the temperature T of the test piece S.

[0024] The temperature control mechanism 8 is controlled by the control unit 7. A heating element that directly heats the test specimen S or a cooler that directly cools the test specimen S can be used as the temperature control mechanism 8.

[0025] The scraper 16 has, for example, a brush shape and is in contact with the circular peripheral surface 4a. The rotation of the rotating body 4 causes the scraper 16 to remove abrasion dirt or the like of the test piece S adhering to the circular peripheral surface 4a. Consequently, a constant surface roughness on the circular peripheral surface 4a can be easily maintained at all times, which is advantageous for accurately determining the abrasion state of the rubber of the test piece S.

[0026] An evaluation method using the testing apparatus 1 according to the present invention will be described below.

[0027] As in Fig. 1 and Fig. 2, the test piece S is held by the holding section 3. A desired specification is set for the circular peripheral surface 4a. For example, when a top rubber cover 17a of a conveyor belt is evaluated as the test piece S, the circular peripheral surface 4a having a surface roughness in accordance with the shape of a conveying object 20 or the like conveyed on the conveyor belt is adopted. Moreover, the weight of the weight 15 is adjusted so that a desired additional force F is applied to the test piece S, and the rotating body 4 is rotated at the desired set speed. Further, the temperature control mechanism 8 is activated, thereby adjusting the test piece to a desired temperature. The adjustments are made, for example, under conditions under which the rubber of the test piece S is used in practice.

[0028] In the abrasion testing device 1 with the settings described above, the additional force F directed towards the circular peripheral surface 4a of the rotating body 4 is applied to the test specimen S as shown in Fig. 1. The test piece S is pressed by the additional force F in a predetermined fixed position relative to the rotating body 4 and comes into contact with the circular peripheral surface 4a. The rotating body 4 rotates, thereby bringing the test piece S and the circular peripheral surface 4a into a sliding state, and gradually wearing away the contact surface with the circular peripheral surface 4a of the test piece S.

[0029] Typically, when a target object and a rubber move relative to each other in a state where they are in contact with each other, and the target object slides with respect to the rubber, the two are not equally in contact with each other, and a so-called stick-slip phenomenon occurs. In the stick-slip phenomenon, a process (sticking process) in which the rubber resists a force (frictional force) received by the target object and is elastically deformed is repeated, and a process (sliding process) in which the rubber cannot resist the frictional force, and the elastic deformation is released, pushing the rubber toward the target object is repeated.

[0030] The adhesion process and the sliding process are repeated, and thus, as in Fig. As illustrated in Figure 3, abrasion stripes L form at predetermined intervals P in a sliding direction FD on the surface of the rubber R on which the target object slides. The intervals P correspond to the sliding process, and the abrasion stripes L correspond to the adhesion process.

[0031] In the test fixture 1, the specimen S can always move in the direction opposite to the additional force F, thus repeating the sticking and sliding processes when the specimen S slides on the circular circumferential surface 4a. This means that the stick-slip phenomenon can be reproduced. Accordingly, the abrasion state of the rubber can be determined with higher accuracy, consistent with practical use. For example, the abrasion state of the upper rubber cover of the conveyor belt can be determined with accuracy.

[0032] In the evaluation method according to the present invention as described above, the abrasion test of the test piece S is carried out for a predetermined time, and the rubber abrasion resistance of the test piece S is evaluated based on the abrasion degree D of the test piece S. Further, the abrasion resistance of the test piece S is evaluated based on at least one of two elements including the power W required to drive and rotate the drive motor 5 during the abrasion test and the temperature T of the test piece S during the abrasion test.

[0033] For example, since the evaluation is based on the degree of abrasion D, the abrasion test is carried out by varying the additional force F and the peripheral speed V, and the degree of abrasion D is measured. This gives the Fig. 4 and Fig. 5 illustrated data. Fig. 4 illustrates a relationship of the abrasion degree D and the additional force F for a plurality of test pieces S (S1, S2, S3), each being a different rubber type, in a case where a peripheral speed V represents a certain predetermined speed. Fig. Figure 5 illustrates a relationship between the degree of abrasion D and the additional force F in a case where the abrasion test is carried out, with the difference that the peripheral speed V is three times that in the case of Fig. 4.

[0034] A test specimen S1 is rubber from a formulation enriched with NR, S2 is rubber from a formulation enriched with SBR, and S3 is rubber from a formulation enriched with BR. Fig. 4 and Fig. 5 the degree of abrasion D is indicated by an index divided by a specific reference value.

[0035] From the data of Fig. 4 and Fig. 5 shows that, as with any specimen S, the degree of abrasion D also increases with increasing peripheral speed V. Furthermore, the degree of slope of the data varies depending on the specimen S, and thus it is obvious that the degree of influence of the additional force F and the peripheral speed V on the degree of abrasion D varies depending on the rubber type.

[0036] The apparent friction energy E1 can be calculated as a result of the "additional force F × circumferential speed V" (E1 = F × V) in a case where the test piece S is pressed against the circular peripheral surface by the additional force F 4a with the peripheral speed V. Thus, for example, the apparent friction energy E1 of corresponding test pieces S is calculated by the control unit 7, whereby the ratio of the apparent friction energy E1 and the abrasion degree D in Fig. 6. Based on the data in Fig. 6, a relationship between the apparent friction energy E1 and the degree of abrasion D can be determined for each rubber type.

[0037] As an evaluation based on the power W, for example, during the abrasion test, the friction force Ff with respect to the circular peripheral surface 4a of the test specimen S is detected based on the power W by the dynamometer 6a. Then, the abrasion resistance is evaluated by the magnitude of the calculated friction force Ff.

[0038] Specifically, the energy required to drive and rotate the rotating body 4 at a predetermined speed is compared in a case where the test piece S is in contact with the circular peripheral surface 4a of the rotating body 4 and in a case where the test piece S is not in contact with the circular peripheral surface 4a of the rotating body 4, and an energy difference between the two cases can be calculated as friction energy E2 generated by friction between the test piece S and the circular peripheral surface 4a. It can be imagined that the friction energy E2 per unit time is "E2 = friction force Ff × peripheral speed V", which is "friction force Ff = E2 / peripheral speed V". Thus, the sliding friction coefficient μ of the test piece S can be calculated as "μ = friction force Ff / additional force F".

[0039] In Fig. 7, with respect to the respective test pieces S1, S2 and S3, a relationship between the peripheral speed V and the power W is illustrated by solid lines, and a relationship between the peripheral speed V and the sliding friction coefficient µ is illustrated by dotted lines. Based on the data in Fig. 7 the abrasion behavior can be determined for each rubber type.

[0040] During the abrasion test, a generation cycle f for the stick-slip phenomenon occurring in the test specimen S can be calculated based on the fluctuation in the power W. In Fig. Figure 8 illustrates the change in power W over time, measured by the dynamometer 6a during the abrasion test of specimen S1. It is conceivable that the power W is relatively increased in the sliding process of the stick-slip phenomenon, and the power W is relatively decreased in the sliding process of the stick-slip phenomenon. Thus, the intervals between corresponding adjacent peaks within the data correspond to the generation cycle f. The peripheral speed V is known in the abrasion test, and thus the predetermined intervals P in which the Fig. 3 illustrated abrasion strips L are formed, can be calculated as “P = peripheral speed V / generation cycle f”.

[0041] The production cycle f (specified interval P) varies depending on the rubber type. Furthermore, a difference in the production cycle f (specified interval P) results in a difference in the abrasion mode, which serves as an index for evaluating rubber abrasion resistance.

[0042] In the test fixture 1, the stick-slip behavior of the test piece S can be detected by taking a photograph of the movement of the test piece S with the camera 6c. For example, the generation cycle f of the stick-slip phenomenon is approximately 0.01 to 0.03 seconds. Thus, a high-speed camera 6c capable of recording 100 frames or more per second is advantageously used.

[0043] Furthermore, a degree of deformation in the pressing direction of the test specimen S can be determined using the recording data from the camera 6c. Thus, a relationship between the degree of deformation of the test specimen S and the additional force F and a relationship between the degree of deformation and the friction force Ff can be determined.

[0044] As an evaluation based on the temperature T of the test piece S during the abrasion test, for example, the heat energy E3 in a case where the test piece S is worn is calculated based on the temperature T detected by the temperature sensor 6b. Then, the abrasion resistance is evaluated by the magnitude of the calculated heat energy E3.

[0045] Fig.Figure 9 illustrates the change in temperature T over time in the abrasion test under the same conditions for specimens S1, S2, and S3. Assuming a mass m of specimen S whose temperature is elevated, the specific heat c, and an elevated temperature ΔT are available, the heat energy E3 is represented as "E3 = m × c × ΔT," and, for example, the heat energy E3 can be calculated by the control unit 7.

[0046] The magnitude of the heat energy E3 varies depending on the rubber type. Therefore, the temperature dependence of abrasion resistance varies depending on the rubber type, and thus, it is advantageous to accurately evaluate the abrasion resistance of each rubber type by determining the heat energy E3 for each rubber type. Furthermore, the lower the viscoelasticity of the rubber, which is determined by a loss factor (tanδ), a storage modulus (E'), and a loss modulus (E''), the lower the heat energy E2 tends to be, allowing a relationship between the viscoelasticity of rubber and abrasion resistance to be determined.

[0047] As described above, in the present invention, a predetermined abrasion test is conducted, and when evaluating the abrasion resistance of the test piece S, an evaluation index based on at least one of the two elements including the power W and the temperature T of the test piece S, in addition to the abrasion degree D, is applied. Therefore, the consistency of the evaluation results can be verified based on respective evaluation indices. Accordingly, it is possible to perform the evaluation with high reliability without unduly depending on data on the abrasion degree D. The rubber abrasion resistance can be evaluated based on three elements, namely the power W and the temperature T of the test piece S, in addition to the abrasion degree D. List of reference symbols 1 test device 2 Base 2a Housing 3 holding section 4 rotation bodies 4a Circular circumferential surface 4b Rotating shaft 5 Drive motor 6a Dynamometer 6b Temperature sensor 6c Camera 7 Control unit 7 Temperature control mechanism 9 Feed mechanism 10 Pressure connection mechanism 11 Support column 11a Holding arm 12 wire 13 Compensating element 14 Support shaft 15 Weight 16 scrapers S (S1, S2, S3) test specimen

Claims

[1] Method for evaluating rubber abrasion resistance, comprising: Applying an additional force directed toward a circular peripheral surface of a rotating body rotated by a drive motor toward a rubber test specimen, thereby compressing and adhering the test specimen to the circular peripheral surface in a predetermined fixed position; Holding the test specimen in a state in which movement of the test specimen in a direction opposite to the additional force is possible at all times; performing an abrasion test in which a contact surface of the test specimen with the circular peripheral surface is worn; and Evaluating the abrasion resistance of the test specimen based on at least one of two elements, including the power required to drive and rotate the drive motor during the abrasion test, and a temperature of the test specimen, in addition to an abrasion degree of the test specimen, wherein the method further comprises calculating a generation cycle of a stick-slip phenomenon occurring in the test piece based on fluctuation in performance, and evaluating abrasion resistance of the test piece based on a magnitude of the generation cycle. [2] A method for evaluating rubber abrasion resistance according to claim 1, further comprising evaluating the abrasion resistance of the test piece based on a magnitude of the abrasion degree and the additional force and a peripheral speed of the circular peripheral surface. [3] A method for evaluating rubber abrasion resistance according to claim 1 or 2, further comprising calculating the frictional force with respect to the circular peripheral surface of the test piece based on the performance and evaluating the abrasion resistance of the test piece based on a magnitude of the frictional force. [4] A method for evaluating rubber abrasion resistance according to any one of claims 1 to 3, further comprising calculating heat energy in a case where the test piece is worn based on temperature, and evaluating the abrasion resistance of the test piece based on a quantity of the heat energy.

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