Impact test procedure

Abstract

An impact testing method in which an impact application element is caused to freely fall onto and collide with a sample, the impact testing method comprising: Measuring an impact force exerted on the sample when the impact application element caused to fall freely collides with the sample and an indentation amount of the impact application element in the sample; and Calculating, based on the measured impact force and indentation amount, energy loss E1 absorbed by the sample when the impact application element and the sample collide with each other, determining a ratio (E1 / E) of the energy loss E1 absorbed by the sample to the impact energy E exerted by the impact application element, and collecting data regarding a correlation between this ratio (E1 / E) and the impact strength of the sample to form a database, so that the impact strength corresponding to that under actual use conditions of a target object is determined based on the database and the calculated energy loss E1, where rubber is used as the sample.

Description

Technical area

[0001] The present invention relates to an impact testing method, and more particularly to an impact testing method capable of determining the impact resistance corresponding to that under actual use conditions of a target object such as a conveyor belt. State of the art

[0002] Various objects, including mineral raw materials such as iron ore and limestone, are transported by a conveyor belt. When the objects to be conveyed are fed onto the upper cover rubber of the conveyor belt, the upper cover rubber is subjected to impact. If the surfaces of the objects to be conveyed are sharp, a surface of the upper cover rubber will occasionally experience cut damage. The impact resistance of the upper cover rubber depends, for example, on the rubber properties and the operating environment.

[0003] To date, various methods for assessing the impact resistance of a target object have been proposed (see, for example, Patent Document 1). The method described in Patent Document 1 involves causing a falling weight to collide with and damage (penetrate) a test object. However, as for the target object such as the conveyor belt during general actual use, the conveyed objects that are fed do not easily penetrate and damage the target object. Therefore, the method proposed in Patent Document 1 does not correspond to the actual use conditions of the target object such as the conveyor belt. Thus, the impact resistance cannot be sufficiently determined during actual use. Patent Document 2 discloses an impact testing method.in which, in the same test, both the impact energy and the kinetic energy contained in the ejected mass are determined experimentally by sensors. The total impact energy applied is then automatically corrected to determine the actual fracture energy. The actual fracture energy is then immediately displayed or further evaluated or processed by an automatic measurement evaluation and / or processing system. Patent Document 3 discloses an impact testing device and method for predicting the impact strength of a conveyor belt top cover rubber during actual use. A contact element is repeatedly collided with the surface of a rubber sample by: adjusting the rotation speed of a rotating drum, to the outer peripheral surface of which the rubber sample is attached,to a desired speed; setting an impact cycle for the contact element for impacting the surface of the rubber sample to a desired cycle as a result of a repetitive impact mechanism; setting the impact load from the contact element to a desired impact load using a weight element; selecting a desired contact element as a provided contact element from a variety of types of contact elements having different specifications for a contact surface that comes into contact with the surface of the rubber sample; attaching the contact element to one end in the longitudinal direction of an arm portion constituting the repetitive impact mechanism; rotating a vertical excitation roller; and rotating the arm portion in the vertical direction, having a rotation shaft as a rotation center. List of citationsPatent literature Patent document 1: JP 2008 - 224 632 A Patent document 2: DE 31 49 986 A1 Patent document 3: WO 2016 / 042 999 A1 Summary of the inventionTechnical problem

[0004] An object of the present invention is to provide an impact testing method capable of determining the impact resistance corresponding to that under actual use conditions of a target object such as a conveyor belt. Solution to the problem

[0005] To achieve the above object, one embodiment of the present invention is an impact testing method in which an impact application member is caused to freely fall onto and collide with a sample, the impact testing method including: measuring an impact force applied to the sample when the freely fallen impact application member collides with the sample and an indentation amount of the impact application member in the sample;and calculating, based on the measured impact force and indentation amount, energy loss absorbed by the sample when the impact application member and the sample collide with each other, wherein a ratio (E1 / E) of the energy loss E1 absorbed by the sample to the impact energy E applied by the impact application member is determined, and data regarding a correlation between this ratio (E1 / E) and the impact resistance of the sample is collected to form a database, so that the impact resistance corresponding to that under actual use conditions of a target object is determined based on the database and the calculated energy loss E1, wherein rubber is used as the sample.; Advantageous effects of the invention

[0006] According to the present invention, the energy loss absorbed by the sample is calculated based on the impact force applied to the sample in a process in which the impact application element, which is caused to fall freely, collides with the sample, and the amount of indentation of the impact application element relative to the sample. Thus, the energy loss corresponding to that during actual use of a target object such as a conveyor belt can be determined. Furthermore, the energy loss is closely related to the impact resistance of the target object. Thus, based on the calculated energy loss, the impact resistance corresponding to that under actual use conditions of the target object can be determined with high accuracy. Brief description of the drawings Fig. 1 is an explanatory diagram illustrating a basic structure of an impact testing apparatus. Fig. 2 is an explanatory diagram schematically illustrating a sample deformed by an impact application element caused to fall freely. Fig. Figure 3 is a graph showing a relationship between impact force and indentation amount at room temperature. Fig. Figure 4 is a graph showing a relationship between impact force and indentation amount at a temperature of 70 °C. Fig. Figure 5 is a graph showing a change in a surface temperature of the sample over time. Fig. 6 is an explanatory diagram illustrating a conveyor line in a simplified manner. Fig. 7 is a cross-sectional view along line AA of Fig. 6. Fig. Figure 8 is an explanatory diagram illustrating the speed of an object to be conveyed at the time of collision with the conveyor belt. Description of embodiments

[0007] An impact testing method according to embodiments of the present invention will be described below with reference to the drawings. In the embodiments, examples are described in which a conveyor belt top cover rubber is the target object subjected to impact resistance evaluation.

[0008] On a Fig. In the conveyor belt line illustrated in Figure 6, objects C to be conveyed, which are transported by another conveyor belt 17, are fed to a conveyor belt 11 and transported by this conveyor belt 11 to a conveying destination. The object C to be conveyed can be fed to the conveyor belt 11 through a hopper and the like. The conveyor belt 11 is tensioned with a prescribed tension between the pulleys 15a and 15b.

[0009] As in Fig. As illustrated in Fig. 7, the conveyor belt 11 includes a core layer 12 formed of a core such as canvas or steel cords, and an upper cover rubber 13 and a lower cover rubber 14 sandwiching the core layer 12 therebetween. The core layer 12 is a member that absorbs tension causing the conveyor belt 11 to stretch. The lower cover rubber 14 is supported by a support roller 16 on a support side of the conveyor belt 11, and the upper cover rubber 13 is supported by the support roller 16 on a return side of the conveyor belt 11. Three of the support rollers 16 are arranged on the support side of the conveyor belt 11 in the transverse direction of the belt. The conveyor belt 11 is supported by these support rollers 16 in a concave shape having a prescribed trough angle α.When the pulley 15a on one drive side is driven in rotation, the conveyor belt 11 is operated in one direction at a predetermined transport speed V1. The objects S to be conveyed are fed to the upper cover rubber 13 and are loaded and conveyed onto the upper cover rubber 13.

[0010] In this conveyor line, as shown in Fig. As illustrated in Figure 8, the conveyor belt 11 and the other conveyor belt 17 are arranged so that they have a vertical difference h therebetween. On the other conveyor belt 17, the objects C to be conveyed are transported at a horizontal direction speed V0 (V0 < V1). At the moment the object C to be conveyed, which is fed by the other conveyor belt 17, collides with the conveyor belt 11, the object C to be conveyed is at the horizontal direction speed V0. The vertical direction speed of the object C to be conveyed is accelerated from 0 to V2. The vertical direction speed V2 corresponds to (2gh) 1 / 2 . Therefore, the actual collision speed Vr at which the object C to be conveyed collides with the upper cover rubber 13 of the conveyor belt 11 (V0 2 + V2 2 ) 1 / 2 = (V0 2 + 2gh) 1 / 2"g" denotes the acceleration due to gravity. When the object C to be conveyed, which has fallen freely as described above, collides with the upper cover rubber 13, the impact energy exerted on the upper cover rubber 13 is equal to E Mgh. "M" denotes a mass of the object C to be conveyed.

[0011] The upper cover rubber 13 absorbs a predetermined portion of the impact energy E. The amount of energy absorbed by the upper cover rubber 13 (energy loss E1) depends on the rubber type. The amount of absorbed energy loss E1 and the impact resistance of a specific rubber type are interrelated. Thus, the impact resistance of a specific rubber type can be determined by calculating the energy loss E1.

[0012] As in Fig. As illustrated in Figure 1, an impact testing apparatus 1 includes a placement platform 2 on which a sample S is placed, an impact application member 10 that is caused to fall freely onto the sample S, a load cell 5, a displacement sensor 6, and a calculation unit 8. In this embodiment, the impact testing apparatus 1 further includes a temperature sensor 7 and a temperature controller 9. The sample S is an article corresponding to an actual-use member as a target object subjected to impact resistance evaluation (upper cover rubber 13).

[0013] The impact application elements 10 preferably include a plurality of types of impact application elements 10a, 10b, 10c, and 10d with different characteristics in terms of the shape of the bottom end and weight. Among the plurality of feature types, the impact application element 10 is selected with characteristics similar to those of the object C to be conveyed, which applies an impact to the upper cover rubber 13 during actual use.

[0014] The impact testing apparatus 1 has a configuration in which a support portion 3a extends within a frame 3 in an upright state, and a holding mechanism 4 is provided on the support portion 3a; the support portion 3a can be tilted and fixed to any height position; and when the impact application member 10a detachably held by the holding mechanism 4 is released from a holding state, the impact application member 10a freely falls onto the sample S placed on the placement platform 2 having a flat plate shape.

[0015] The load cell 5 is installed below the placement platform 2 and measures an impact force exerted on the sample S. As shown in Fig. As illustrated in Figure 2, the displacement gauge 6 measures an indentation amount H of the impact application element 10a that has freely fallen onto and collided with the sample S. If the impact application element 10a has a lower end with a sharp shape, the indentation amount H corresponds to a scratch depth. Measurement data obtained from the load gauge 5 and the displacement gauge 6 are input to the calculation unit 8. For example, a computer of any type can be used as the calculation unit 8.

[0016] The temperature sensor 7 measures a surface temperature of the sample S. The surface temperature measured by the temperature sensor 7 is input into the calculation unit 8. For example, thermography can be used as the temperature sensor 7.

[0017] The temperature controller 9 adjusts the temperature of the sample S to an arbitrary temperature by heating or cooling the sample S. In this embodiment, the temperature controller 9 installed on a lower surface of the placement platform 2 heats or cools the placement platform 2. In this way, the sample S is indirectly heated and cooled to adjust to an arbitrary temperature. Instead of the temperature controller 9, for example, a thermostatic housing that covers the entire testing device with a cover and is capable of adjusting the cover interior to an arbitrary ambient temperature may be used.

[0018] Next, the process of a testing method using the impact testing apparatus 1 will be described.

[0019] The sample S is placed on the Fig. 1. Among the plurality of types of impact application elements 10, the impact application element 10a that is suitable for and similar to the actual usage conditions of the conveyor belt 11 is selected and mounted on the support mechanism 4. Further, the support section 3a is moved so that the impact application element 10 is set to a suitable height position (for example, a position of a height h from the surface of the sample S). The temperature controller 9 sets the sample S to have a predetermined temperature.

[0020] Next, the impact application element 10 is released from a holding state by the holding mechanism 4 and is caused to freely fall to collide with the sample S. In this case, the impact energy E exerted by the impact application element 10, which has freely fallen from the position of height h from the surface of the sample S, is equal to Mgh (E = Mgh). Here, "M" denotes a known mass of the impact application element 10.

[0021] The freely fallen impact application element is brought into contact with the sample and rebounds away from the sample. In this collision process from the contact state to the removed state, the load meter 5 successively measures an impact force exerted on the sample S. Furthermore, the displacement meter 6 successively measures the indentation amount H of the impact application element 10 with respect to the sample S, which is Fig. 2. The impact force measured by the load cell 5 and the indentation amount H measured by the displacement cell 6 are input into the calculation unit 8.

[0022] As in Fig. 3 and Fig. As illustrated in Figure 4, the impact force and the indentation amount H are measured by the impact test. Four types of samples S (S1 to S4) are subjected to measurement under the same test conditions at room temperature (case where the samples S have a temperature of approximately 20 °C). Fig. 3 shows the measurement data of this case. The four types of samples S (S1 to S4) are only changed in temperature and set to have a temperature of 70 °C. In Fig. 4 shows the measurement data of this case.

[0023] Based on the input measurement data, the calculation unit 8 calculates the energy loss E1 absorbed by the sample S when the impact application element 10 and the sample S collide with each other. Fig. 3 and Fig. 4, the area where the data curves of the respective samples S extend to the upper right indicates a relationship between the impact force and the indentation amount H from the time the impact application member 10 is brought into contact with the sample S to the time the impact application member 10 indents the sample S to the deepest. Thus, by integrating the data curves in this area, the indentation energy E2 can be calculated.

[0024] The area where these data curves extend to the lower left indicates the relationship between the impact force and the indentation amount H from the time when the impact application element 10 indents the sample S to the deepest point until the impact application element 10 rebounds away from the sample 10. Thus, by integrating the data curves in this area, the repulsion energy E3 can be calculated.

[0025] Therefore, by subtracting the repulsion energy E3 from the indentation energy E2, the energy loss E1 absorbed by the sample S (E1 = E2 - E3) can be calculated. That is, in Fig. 3 and Fig. 4, the areas enclosed by the respective data curves S1, S2, S3 and S4 correspond to the energy loss E1 of the respective samples S.

[0026] In one embodiment of the present invention, a ratio (E1 / E) of the energy loss E1 absorbed by the sample S to the impact energy E applied by the impact application element 10 is determined. This ratio (E1 / E) depends on the rubber type (particularly viscoelastic properties) and is closely related to the impact resistance of rubber. In view of the above, data regarding a correlation between this ratio (E1 / E) and the impact resistance of rubber is collected to form a database. Based on the database and the calculated energy loss E1, the impact resistance corresponding to that under actual use conditions of a target object (conveyor belt 11) can be determined with high accuracy.

[0027] Furthermore, by comparing the data in Fig. 3 and Fig. 4 that the energy loss E1 depends on a temperature of the sample S. Therefore, the samples S are temperature-changed at multiple stages and subjected to the impact test, so that the above-mentioned respective measurement data are obtained. Thus, the temperature dependence of the energy loss E can be determined. Specifically, the database can be created for each temperature of the samples S. Thus, by using the database of a temperature condition corresponding to an ambient temperature for the use of the conveyor belt 11, the impact resistance corresponding to that under the actual use conditions of the target object (conveyor belt 11) can be determined with higher accuracy.

[0028] In this embodiment, the temperature sensor 7 can successively measure the surface temperature of the sample S immediately after the rebound of the impact application element 10. The surface temperature measured by the temperature sensor 7 is input to the calculation unit 8. As shown in Fig. As illustrated in Figure 5, the surface temperature of the sample is measured at room temperature, and the change over time can be determined.

[0029] Based on the measured surface temperature and the indentation amount H, the calculation unit 8 calculates the heat energy E4 generated in the sample S when the impact application element 10 and the sample S collide with each other. The heat energy E4 can be calculated by an equation E4 = mcΔT. "m" denotes a mass of the sample S with increased temperature. "c" denotes a specific heat of the sample S. "ΔT" denotes a temperature rise of the test.

[0030] From the Fig. The measurement data shown in Figure 5 yields the temperature rise ΔT of sample S caused by the collision with the impact application element 10 (maximum temperature rise ΔT). The specific temperature c of sample S is predetermined.

[0031] The mass m of the temperature-risen sample S is calculated, for example, in the following manner. The displacement meter 6 measures the indentation amount H of the impact application member 10. Further, since the shape of the impact application member 10 is given in advance, a volume V of the temperature-risen sample S is calculated, for example, by multiplying a maximum indentation amount and a maximum cross-sectional area of ​​the portion where the impact application member 10 indents the sample S the deepest. Since a specific density ρ of the sample S is given in advance, the mass m of the temperature-risen sample S can be calculated by multiplying the volume V and the specific density ρ. Further, by multiplying the mass m, the specific heat c, and the temperature rise ΔT, the heat energy E4 can be calculated.

[0032] Thus, a ratio (E4 / E) of the heat energy E4 converted by the sample S to the impact energy E exerted by the freely fallen impact application element 10 can be determined. This ratio (E4 / E) depends on the rubber type (particularly viscoelastic properties among rubber properties) and is closely related to the impact resistance of rubber. In view of the above, data regarding a correlation between this ratio (E4 / E) and the impact resistance of rubber is collected to create a database. Based on the database and the calculated heat energy E4, the impact resistance corresponding to that under actual use conditions of a target object (conveyor belt 11) can be determined with high accuracy.

[0033] In this embodiment, the upper cover rubber 13 of the conveyor belt 11 is taken as an example of a target object subjected to impact resistance evaluation. However, the target object is not limited to this. The target object only needs to be one that is used under such a condition that various collision objects such as stones or gravel collide and rebound, and that is not easily penetrated by the collision objects. Specifically, in addition to the upper cover rubber 13, the lower cover rubber 14 of the conveyor belt 11, a rubber member such as a tread rubber of a tire, the core layer 12 of the conveyor belt 11, or other members can be exemplified as the target object. List of reference symbols 1 impact test device 2 Placement platform 3 frame 3a support section 4 Holding mechanism 5 load meters 6 displacement meters 7 Temperature sensor 8 Calculation unit 9 temperature controllers 10 Impact application element 11 Conveyor belt 12 core layer 13 Upper cover rubber 14 Lower rubber pad 15A, 15b pulley 16 support roller 17 Other conveyor belt S (S1, S2, S3, S4) sample

Claims

[1] Impact testing method in which an impact application element is caused to fall freely onto and collide with a sample, the impact testing method comprising: Measuring an impact force exerted on the sample when the impact application element caused to fall freely collides with the sample and an indentation amount of the impact application element in the sample; and Calculating, based on the measured impact force and indentation amount, energy loss E1 absorbed by the sample when the impact application element and the sample collide with each other, determining a ratio (E1 / E) of the energy loss E1 absorbed by the sample to the impact energy E exerted by the impact application element, and collecting data regarding a correlation between this ratio (E1 / E) and the impact strength of the sample to form a database, so that the impact strength corresponding to that under actual use conditions of a target object is determined based on the database and the calculated energy loss E1, where rubber is used as the sample. [2] The impact testing method according to claim 1, further comprising: Measuring a surface temperature of the sample with which the impact application element collides; and Calculate, based on the surface temperature and indentation amount measured, heat energy generated in the sample when the impact application element and the sample collide with each other. [3] The impact testing method according to claim 1 or 2, wherein the impact test is carried out under different temperature conditions.

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