Test apparatus and method for tensile, compressive and flexural fatigue properties of fiber-rubber composite structures

Abstract

The present invention provides a testing device and method for the tensile, compressive and bending fatigue performance of a fiber and rubber composite structure, the testing device includes a guide roller system, a lever loading system, a sample strip and an extrusion pre-tightening device; the guide roller system includes a fixed guide roller and a sliding guide roller; the lever loading system is arranged on one side of the sliding guide roller in the horizontal direction and one end is connected to the rotating shaft of the sliding guide roller; the lever loading system applies an upward force to the sliding guide roller to complete the loading of the sample strip; the extrusion pre-tightening device is arranged on the outside of the sample strip, which is in contact with the outer surface of the sample strip and applies an extrusion force to the outer surface of the sample strip. The present invention can make the fiber and rubber composite structure sample produce tensile, compressive and bending deformations, and can control what kind of deformation each component in the sample strip produces, especially can make the fiber produce compressive strain during the test process, so as to evaluate its various fatigue life indicators including compression resistance.

Description

Technical Field

[0001] The invention relates to the technical field of rubber industrial products, and in particular to a testing device and method for tensile and compressive bending fatigue performance of a fiber and rubber composite structure. Background Art

[0002] Fiber-reinforced rubber, or fiber-rubber composite structure, is an important structure widely used in rubber industrial products such as tires. Its fatigue resistance is directly related to the reliability and service life of industrial products such as tires. However, since the structures of these industrial products are often complex and the working conditions they are subjected to during service are varied, such as tension and bending, it has always been a difficult problem to evaluate the fatigue life of fiber-rubber composite structures. Research in recent years has found that the fiber components in composite materials not only undergo tensile deformation, but also undergo certain compression deformation under certain conditions of use, and fatigue failure occurs under compression conditions. The loading conditions involved in the existing test devices or test methods for the fatigue life of fiber-rubber composite structures are mainly concentrated on the determination of fatigue properties related to tension, and there is a lack of test devices and methods that can realize the compression deformation of fiber components in composite materials and test the fatigue mechanical properties of fibers under corresponding conditions. Therefore, there is a need for a test device and method that can cause compression deformation of fiber components and test the tensile, compressive and bending fatigue properties of fiber-rubber composite structures. Summary of the invention

[0003] In view of the problems existing in the above-mentioned background technology, the present invention provides a testing device and method for the tensile and compressive bending fatigue properties of a fiber and rubber composite structure. The device and method are reasonably conceived, in which the fiber and rubber composite structure is processed into a closed annular strip, and a pair of guide rollers with a certain curvature are used to simulate the bending state of the fiber and rubber composite structure at different curvature radii; at the same time, the guide roller system, the sample strip and the extrusion device are loaded through a lever loading system, so that the sample strip obtains a certain tensile force; in addition, by controlling parameters such as the position of the neutral plane of the sample cross section, the cross-sectional size, and the tensile force, the fiber components in the sample can produce a certain compression deformation during the test, and the mechanical properties of the fibers of the sample strip when compressive deformation are produced are tested, thereby providing valuable data for the product reliability of the fiber-reinforced rubber.

[0004] In order to solve the above technical problems, the present invention provides a testing device for tensile and compressive bending fatigue performance of a fiber and rubber composite structure, which includes a guide roller system, a lever loading system, a sample strip and an extrusion pre-tightening device;

[0005] The guide roller system is used as a carrier for the fiber reinforced rubber sample, and includes a fixed guide roller and a sliding guide roller; the rotation axis position of the fixed guide roller is fixed relative to the ground, and the fixed guide roller can rotate around its rotation axis; the sliding guide roller is located directly above the fixed guide roller, and a vertical slide groove is matched in the central area of ​​the sliding guide roller; the rotation axis of the sliding guide roller can slide up and down in the slide groove; the rotation of the sliding guide roller and the fixed guide roller is driven by the same motor; the sample strip is matched and wound around the fixed guide roller and the sliding guide roller;

[0006] The lever loading system is matched and arranged on one side of the sliding guide roller in the horizontal direction, and one end of the lever loading system is matched and connected with the rotating shaft of the sliding guide roller; the lever loading system applies an upward force to the sliding guide roller by using the lever principle to complete the loading of the sample strip;

[0007] The extrusion pre-tightening device is matched and arranged on the outside of the sample strip, and is in contact with and connected to the outer surface of the sample strip and applies an extrusion force to the outer surface of the sample strip.

[0008] The testing device for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure, wherein: the width of the slide groove is equal to the diameter of the rotating shaft of the sliding guide roller, and the rotating shaft of the sliding guide roller does not contact the two ends of the slide groove.

[0009] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure, wherein: the lever loading system includes a lever, a hook, a hinge point and a lever weight; the hinge point is arranged at the lower part of the lever, the left end is hinged with the rotating shaft of the sliding guide roller, and the right end is distributed with a hook for hanging the lever weight at intervals.

[0010] The testing device for tensile and compressive bending fatigue performance of the fiber and rubber composite structure, wherein: the length of the lever body located on the left side of the hinge point is smaller than the length of the lever body located on the right side of the hinge point.

[0011] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure, wherein: the extrusion preload device is matched and arranged directly above the sliding guide roller, and comprises a device body, a preload weight, a spring and an extrusion roller; the upper end of the device body is used to place the preload weight, and the lower end is a concave arc surface structure and the arc is consistent with the sliding guide roller; the upper end of the spring is matched and connected with the lower end arc surface of the device body, and the lower end of the spring is matched and connected with the extrusion roller; the lower part of the extrusion roller is matched and contacted with the upper side surface of the sample strip, and is used to transfer the load of the extrusion preload device to the surface of the sample strip for loading.

[0012] The testing device for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure, wherein: the extrusion pre-tightening device can also be matched and arranged directly below the fixed guide roller, and an extrusion force is applied to the lower surface of the sample strip by a bottom-up loading method.

[0013] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure, wherein: the extrusion preload device can use an circumscribed circular roller; one axial side of the circumscribed circular roller is open, the other axial side is closed and a circumscribed circular roller shaft is matched and arranged in the center; the open side of the circumscribed circular roller is used to facilitate the connection between the lever loading system and the rotating shaft of the sliding guide roller; the inner edge of the circumscribed circular roller contacts the top of the sample strip; the circumscribed circular roller shaft can be matched and connected with an external loading device for downward loading, so that the circumscribed circular roller and the sample strip are squeezed at the top of the sliding guide roller.

[0014] The testing device for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure, wherein: the extrusion preload device can also use two auxiliary rollers arranged on the outside of the sample strip to achieve the function of bending and loading the sample strip on the other side; and the positions of the two auxiliary rollers can be moved artificially to change the load on the sample strip.

[0015] The testing device for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure, wherein: the auxiliary roller can be provided with a height-adjustable boss on its surface; the upper end surface of the boss is smooth and will cause the sample strip to bulge upward when in contact with the sample strip.

[0016] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure, wherein: the auxiliary roller can also be composed of a number of adjacent guide rollers of the same size; the lower end of each guide roller is connected to a telescopic rod; when the telescopic rod is extended, the guide roller connected thereto will be pushed outward; when conducting the test, a mark can be made on the sample strip in advance, and the telescopic rod can be controlled in conjunction with an optical sensor. When the marked position of the sample strip moves above one of the guide rollers, the telescopic rod is automatically extended to cause a local bulge deformation at the marked position of the sample strip.

[0017] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure, wherein: the sample strip can be provided with a groove at its top to change the shape of a partial cross section of the sample strip, so that the neutral plane of the sample strip is changed and is no longer a plane, but is controlled by the shape of the groove.

[0018] A test method for the tensile and compressive bending fatigue performance of a fiber and rubber composite structure. After selecting a sample strip of appropriate size, the sample strip is installed on a fixed guide roller and a sliding guide roller, and the motor speed is set according to the required loading rate, and the sample strip begins to undergo a fatigue test; when the sample strip is obviously damaged or partially broken, the sample is determined to be failed and the test is ended; finally, the number of revolutions of the sample strip from the beginning of the test to the end of the test is recorded, which is the fatigue life of the sample strip under the corresponding loading conditions.

[0019] The test method for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure, wherein: the test method is based on the premise that the sample strip is a symmetrical structure, and the force F that the lever loading system needs to generate and transmit to the sample strip is controlled by formula (1):

[0020] F = 2EAε (1);

[0021] In the above formula (1), A is the total cross-sectional area, and E is the average elastic modulus of the cross-sectional area, which is calculated as shown in the following formula (2):

[0022]

[0023] In the above formula (2), E1 and E2 are the elastic moduli of the fiber and rubber of the sample strip, respectively; A1 and A2 are the areas of the fiber and rubber of the sample strip, respectively, and A1+A2=A.

[0024] The test method for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure, wherein: the test method is based on the premise that the sample strip is a symmetrical structure, and the specific test process is as follows:

[0025] First, according to the bending radius required by the test, select the sliding guide roller and fixed guide roller of appropriate size;

[0026] Secondly, according to the cyclic loading frequency required by the test, adjust the motor to control the speed of the sliding guide roller and the fixed guide roller;

[0027] Then, the position of the neutral plane of the sample strip is determined. According to material mechanics, the definition of the neutral plane is: the static moment of the cross section with respect to the neutral plane is zero; for the cross section of the sample strip, it is expressed by the following formula (3):

[0028]

[0029] In the above formula (3), E1 and E2 are the elastic moduli of the fiber and rubber of the sample strip, respectively; A1 and A2 are the areas of the fiber and rubber of the sample strip; r is the radius of the sliding guide roller and the fixed guide roller; a is the distance between the neutral plane and the bottom surface of the cross section, which is used to determine the position of the neutral plane;

[0030] For a sample strip with an asymmetric structure, the distance between the neutral plane of the sample strip and the bottom surface can be solved as shown in the following formula (4):

[0031]

[0032] In the above formula (4), L is the total thickness of the sample strip, b is the distance between the fiber 31 and the bottom surface of the sample strip 3, and c is the thickness of the fiber 31;

[0033] At this time, if the test requires that the compressive strain of the fiber of the sample strip be ε, then:

[0034]

[0035] In the above formula (5), F is the constant force transmitted to the sliding guide roller by the lever loading system, A is the total cross-sectional area, and E is the average elastic modulus of the cross-sectional area;

[0036] The constant force F transmitted to the sliding guide roller by the lever loading system is controlled by the following formula (1):

[0037] F = 2EAε (1);

[0038] In the above formula (1), A is the total cross-sectional area, and E is the average elastic modulus of the cross-sectional area, which is calculated as shown in the following formula (2):

[0039]

[0040] In the above formula (2), E1 and E2 are the elastic moduli of the fiber and rubber of the sample strip, respectively; A1 and A2 are the areas of the fiber and rubber of the sample strip, respectively, and A1+A2=A;

[0041] The constant force F transmitted to the sliding guide roller by the lever loading system can be obtained from the above formula (5): Between the sliding guide roller and the fixed guide roller, the sample strip will always remain in a tensile state. The width of the sample strip can be changed in advance according to the actual situation, thereby changing the value of A, so that the tensile strain of the tensile section also meets the test requirements;

[0042] When all test conditions meet the requirements, make the sliding guide roller and the fixed guide roller run at a certain speed or acceleration, and record the number of turns the sample strip makes from the start of the test to the occurrence of damage. Twice the number of turns is the fatigue life of the sample strip under the test conditions.

[0043] By adopting the above technical solution, the present invention has the following beneficial effects:

[0044] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure of the present invention can cause the fiber and rubber composite structure sample to produce tensile, compressive and bending deformations, and can control what kind of deformation each component in the sample strip produces, especially can cause the fiber to produce compressive strain during the test, so as to evaluate its various fatigue life indicators including compression resistance.

[0045] The testing device for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure of the present invention can achieve a curvature radius and a loading rate that are closer to actual use conditions by freely selecting the bending radius of the guide roller system, the rotational angular velocity of the guide roller system, etc., and obtain more accurate life test data; it can also realize a bidirectional bending loading test on the sample by arranging guide rollers on both sides of the sample; at the same time, by changing the guide roller configuration, the test device can have the function of simulating the stress state of the fiber and rubber composite structure when the tire passes over an uneven road surface.

[0046] The testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure of the present invention can simulate the fatigue performance testing device when the fiber and rubber composite structure sample is bent in two directions, and can simulate the state of the tire encountering an uneven road surface during driving by adding a boss to the auxiliary roller or using automated means to test the corresponding fatigue performance of the fiber and rubber composite structure.

[0047] The test method for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure of the present invention can change the magnitude of the loading force and adjust the position of the neutral plane of the sample strip through a set of control equations, so as to make the tested sample produce certain tensile, compressive and bending deformations during the test process according to user needs, thereby testing the fatigue life of the fiber and rubber composite structure under various load composite loading conditions. In addition, by prefabricating grooves on the sample strip, the neutral plane of the sample strip is no longer a simple plane, thereby adjusting the stress conditions of different sections of the sample to meet more abundant test loading requirements.

[0048] The testing method for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure of the present invention is based on a set of control equations. By changing the size of the guide roller, the size of the loading force, the position of the neutral plane of the sample strip, etc., the fiber component of the tested sample can produce stretching, compression, bending and other deformations that meet the needs of the user during the test, thereby achieving a test effect that is closer to reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 A schematic diagram of the structure of a testing device for the tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided by the present invention;

[0051] Figure 2 A schematic diagram of the structure of the test device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention after the extrusion pre-tightening device is replaced with an external circular roller;

[0052] Figure 3 A schematic cross-sectional view of a sample strip with a symmetrical cross section involved in a testing device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention;

[0053] Figure 4 A schematic side view of a sample strip with a symmetrical cross section involved in a testing device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided by an embodiment of the present invention;

[0054] Figure 5 A schematic cross-sectional view of a sample strip with an asymmetric cross section involved in a method for testing the tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention;

[0055] Figure 6 A schematic side view of a sample strip with an asymmetric cross section involved in a method for testing the tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention;

[0056] Figure 7 A schematic diagram of the geometrical meanings of the parameters involved in the test method for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure provided by the present invention;

[0057] Figure 8 A schematic diagram of the bending deformation of an asymmetric sample cross section involved in the test method for the tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided by the present invention;

[0058] Fig. 9 A schematic diagram of a structure in which two auxiliary rollers are arranged outside a sample strip in a testing device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention;

[0059] Fig.10A schematic diagram of the structure of the auxiliary roller involved in the testing device for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure provided in an embodiment of the present invention ( Figure 8 FIG14-1 is a schematic diagram of the structure of the auxiliary roller with an additional boss, and FIG14-2 and FIG14-3 are schematic diagrams of two different states of the auxiliary roller and the sample strip composed of a plurality of adjacent small guide rollers of the same size);

[0060] Fig.11 A schematic side view of a sample strip with grooves involved in a testing device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention;

[0061] Fig.12 A front view of a sample strip with irregular grooves involved in a testing device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention;

[0062] Fig.13 A schematic side view of a sample strip with irregular grooves involved in a testing device for tensile and compressive bending fatigue properties of a fiber and rubber composite structure provided in an embodiment of the present invention.

[0063] Notes: 1-guide roller system; 11-sliding guide roller; 12-slideway; 13-fixed guide roller; 14-auxiliary roller; 15-boss; 16-small guide roller; 17-telescopic rod; 2-lever loading system; 21-lever; 22-hook; 23-fulcrum; 24-weight; 3-sample strip; 31-fiber; 32-rubber; 33-neutral surface; 34-groove; 4-extrusion preload device; 41-weight; 42-loading spring; 43-extrusion roller; 5-circumscribed circular roller; 51-circumscribed circular roller shaft. DETAILED DESCRIPTION

[0064] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] The present invention is further explained below in conjunction with specific implementation modes.

[0066] like Figure 1 As shown, the testing device for the tensile and compressive bending fatigue properties of the fiber and rubber composite structure provided by the present invention includes a guide roller system 1, a lever loading system 2, a sample strip 3 and an extrusion pre-tightening device 4.

[0067] The guide roller system 1 is used as a carrier for a fiber and rubber composite structure sample, and includes a sliding guide roller 11 , a slide groove 12 and a fixed guide roller 13 .

[0068] The sliding guide roller 11 is a cylindrical structure of a certain width as a whole, and its outer edge surface is relatively rough. When in use, no sliding friction is generated between the outer surface and the sample strip 3; the rotating shaft of the sliding guide roller 11 can slide up and down in a slide groove 12, and the rotating shaft of the sliding guide roller 11 is connected to one end of the lever loading system 2; the rotation of the sliding guide roller 11 is driven by a motor, and the speed of the sliding guide roller 11 can be set by adjusting the output power of the motor.

[0069] The width of the slide groove 12 is equal to the diameter of the rotating shaft of the sliding guide roller 11 , and the length is long enough, that is, during the test loading process, the rotating shaft of the sliding guide roller 11 will not hit the two ends of the slide groove 12 .

[0070] The fixed guide roller 13 has a similar appearance to the sliding guide roller 11. The fixed guide roller 13 has a fixed rotation axis relative to the ground, and the fixed guide roller 13 can rotate around its rotation axis. The fixed guide roller 13 is driven by the same motor that drives the sliding guide roller 11. The rotation angular velocity of the fixed guide roller 13 can be changed by adjusting the motor power. The fixed guide roller 13 and the sliding guide roller 11 can have different diameters as needed.

[0071] The lever loading system 2 is the main loading system of the whole device. It applies an upward force to the sliding guide roller 11 of the guide roller system 1 by using the lever principle, so as to complete the loading of the sample strip 3. The lever loading system 2 includes a lever 21, a hook 22, a hinge 23 and a lever weight 24. A hinge 23 is arranged at the lower part of the lever 21, and the length of the lever body of the lever 21 on the left side of the hinge 23 is shorter than the length of the lever body on the right side of the hinge 23; the left end of the lever 21 is matched and hinged with the rotating shaft of the sliding guide roller 11 of the guide roller system 1, and a hook 22 is distributed at a certain distance at the right end of the lever 21 to hang the lever weight 24; when loading the left end of the lever 21, the position of the hook 22 and the weight of the lever weight 24 can be selected according to the test needs; the length of the lever 21 can be selected according to the lever principle.

[0072] The extrusion preload device 4 is mainly used to apply a certain extrusion force to the surface of the sample strip 3, simulating the interlayer extrusion effect encountered by the fiber and rubber composite structure during use. The extrusion preload device 4 is matched and arranged directly above the sliding guide roller 11 of the guide roller system 1, and includes a device body 40, a preload weight 41, a spring 42 and an extrusion roller 43. The upper end of the device body 40 is a plane and is used to place the preload weight 41 for loading. The lower end of the device body 40 is a concave arc surface structure and the arc is consistent with the sliding guide roller 11 of the guide roller system 1; the upper end of the spring 42 is connected to the lower end arc surface of the device body 40, and the lower end of the spring 42 is connected to the extrusion roller 43; the extrusion roller 43 transfers the load of the extrusion preload device 4 to the surface of the sample strip 3 for loading. The upper end of the preload extrusion device 4 can be loaded with a preload weight 41 by its own weight, and the lower end transmits the load to the upper surface of the tested sample strip 3 through a spring 42 and an extrusion roller 43, extruding the sample strip 3 to simulate the interlayer extrusion effect of the fiber and rubber composite structure during actual use. The extrusion preload device 4 can also be installed below the fixed guide roller 13 of the guide roller system 1, and it only needs to change the loading method from the preload weight 41 to other methods such as a lever, and apply extrusion force to the lower surface of the sample strip 3 by a bottom-up loading method.

[0073] like Figure 2 As shown, another testing device for tensile and compressive bending fatigue performance of a fiber and rubber composite structure provided by an embodiment of the present invention is to Figure 1 The extrusion preload device 4 is replaced by an external circular roller 5. The external circular roller 5 is open on one axial side, closed on the other axial side, and matched with an external circular roller shaft 51 at the center; the open side of the external circular roller 5 facilitates the connection of the lever loading system 2 with the rotating shaft of the sliding guide roller 11 of the guide roller system 1; the inner edge of the external circular roller 5 contacts the top of the sample strip 3; the external circular roller shaft 51 can be connected to an external loading device (such as a servo motor or a weight) for downward loading, so that the external circular roller 5 and the sample strip 3 are squeezed at the top of the sliding guide roller 11 of the guide roller system 1, thereby simulating the interlayer squeezing force that the sample strip 3 is subjected to during use.

[0074] Among them, the tested sample in the present invention is a closed replacement strip shape made by calendering, vulcanization and other methods, namely, a sample strip 3. During the test, it needs to be sleeved on the outer edges of two sliding guide rollers 11 and a fixed guide roller 13, and its movement is driven by the rotation of the sliding guide rollers 11 and the fixed guide rollers 13; during the movement of the sample strip 3, the deformation of each component may include stretching, compression and bending.

[0075] like Figure 4-5As shown, the sample strip 3 includes fiber 31, rubber 32 and neutral surface 33. The sample strip 3 is a closed replacement strip shape made by calendering, vulcanization and other methods. During the test, it needs to be sleeved on the outer edge of the sliding guide roller 11 and the fixed guide roller 13, and the sliding guide roller 11 and the fixed guide roller 13 rotate to drive the sample strip 3 to move; during the movement of the sample strip 3, the deformation of each component may include tension, compression and bending. From the knowledge of material mechanics, it can be known that when the material is bent and deformed, the part below the neutral surface 33 on the cross section of the sample strip 3 will be subjected to compressive stress, and the part above the neutral surface 33 will be subjected to tensile stress.

[0076] The testing method for the tensile and compressive bending fatigue performance of the fiber and rubber composite structure of the present invention is to select a sample strip of appropriate size, install the sample strip on a fixed guide roller and a sliding guide roller, set the motor speed according to the required loading rate, and start the fatigue test of the sample strip; when the sample strip is obviously damaged or partially broken, it is determined that the sample has failed and the test is ended; finally, the number of revolutions of the sample strip from the beginning of the test to the end of the test is recorded, which is the fatigue life of the sample strip under the corresponding loading conditions.

[0077] In one embodiment of the present invention, the cross-sectional morphology of the sample strip 3 is as follows: Figure 3 and Figure 4 As shown, it is a symmetrical structure; it involves a test method for the tensile and compressive bending fatigue performance of a fiber and rubber composite structure. Based on a set of control equations, by changing the size of the guide roller, the size of the loading force, the position of the neutral plane of the sample strip, etc., the fiber 31 of the sample strip 3 can produce stretching, compression, bending and other deformations that meet the user's needs during the test, thereby achieving a test effect that is closer to the actual situation.

[0078] In the test, if we want to obtain the tensile bending fatigue test life of the sample strip 3 when the tensile strain is ε and the bending radius is r, we need to select the sliding guide roller 11 and the fixed guide roller 13 with a radius of r, and adjust the tensile strain of the sample strip 3 to ε through the lever loading system 2. It can be calculated that the force F that the lever loading system 2 needs to generate and transmit to the sample strip 3 is controlled by formula (1):

[0079] F = 2EAε (1);

[0080] In the above formula (1), A is the total cross-sectional area, and E is the average elastic modulus of the cross-sectional area, which is calculated as shown in the following formula (2):

[0081]

[0082] In the above formula (2), E1 and E2 are the elastic moduli of the fiber 31 and the rubber 32 respectively; A1 and A2 are the areas of the fiber 31 and the rubber 32, and A1+A2=A.

[0083] like Figure 5 and Figure 6 The asymmetric cross-section specimen shown can cause compressive strain in the fibers 31 in the specimen strip 3 under certain conditions, thereby evaluating the fatigue mechanical properties of the specimen strip 3 in a compressed state containing the fibers 31 .

[0084] In one embodiment of the present invention, the cross-sectional morphology of the sample strip 3 is as follows: Figure 5 , Figure 6 and Figure 8 As shown, it is an asymmetric structure; it involves a test method for the tensile and compressive bending fatigue performance of a fiber and rubber composite structure, and the specific steps are as follows:

[0085] First, according to the bending radius required by the test, the sliding guide roller 11 and the fixed guide roller 13 of appropriate size are selected;

[0086] Secondly, according to the cyclic loading frequency required by the test, the motor is adjusted to control the rotation speed of the sliding guide roller 11 and the fixed guide roller 13;

[0087] Then the position of the neutral plane is determined. According to material mechanics, the definition of the neutral plane is: the static moment of the cross section with respect to the neutral plane is zero; for the cross section of the sample strip 3, it is expressed by the following formula (3):

[0088]

[0089] In the above formula (3), a is the distance between the neutral plane and the bottom surface of the cross section, which is used to determine the position of the neutral plane; the other parameters have the same meaning as in the previous text.

[0090] for Figure 7 For the asymmetric general structure shown, the distance between the neutral plane and the bottom surface can be solved as shown in the following formula (4):

[0091]

[0092] In the above formula (4), L is the total thickness of the sample strip 3, b is the distance between the fiber 31 and the bottom surface of the sample strip 3, and c is the thickness of the fiber 31.

[0093] At this time, if the test requires that the compressive strain that the fiber 31 needs to reach is ε (absolute value of strain), then:

[0094]

[0095] In the above formula (5), F is the upward constant force transmitted to the sliding guide roller 11 by the lever loading system 2.

[0096] Assuming that the constant upward force transmitted by the lever loading system 2 to the sliding guide roller 11 is F, the required It is worth noting that the sample strip 3 will always remain in a tensile state between the sliding guide roller 11 and the fixed guide roller 13. Therefore, the width of the sample strip 3 can be changed in advance according to the actual situation, thereby changing the value of A, so that the tensile strain of the tensile section also meets the test requirements. When all test conditions meet the requirements, the sliding guide roller 11 and the fixed guide roller 13 are operated at a certain speed or acceleration, and the number of turns of the sample strip 3 from the start of the test to the occurrence of damage is recorded. Twice the number of turns is the fatigue life of the sample strip 3 under the test conditions.

[0097] The above is a method for adjusting the load F of the lever loading system 2 so that the sample strip 3 produces tensile, compressive and bending deformations that meet the test requirements.

[0098] In another embodiment of the present invention, the test has specified the load F to be applied. Under this condition, in order to meet the condition that the compressive strain of the fiber 31 reaches ε, the area of ​​the neutral surface 33 of the sample strip 3 needs to be adjusted to meet the test requirements. According to equations (4) and (5), the value of b that meets the requirements can be calculated:

[0099]

[0100] α=2[E1(Lc)+E2c] (7);

[0101]

[0102] That is, the geometric parameters a and b obtained by equations (6) to (8) can satisfy the condition that the compressive strain of fiber 2 reaches ε under the specified load F. The adjustment method of the bending radius and the deformation of the tensile section required for the test is the same as the method described above.

[0103] The above is a test method for achieving tensile, compressive and bending deformations that meet the test requirements under certain loading conditions by adjusting the geometric features of the sample strip 3 and changing the position of the neutral plane 33.

[0104] In another embodiment of the present invention, Fig. 9 As shown, by arranging two auxiliary rollers 14 on the outside of the sample strip 3, the function of bending and loading the sample strip 3 on the other side is realized. Figure 7 As shown, the positions of the auxiliary rollers 14 on both sides can be moved manually, so that the load on the sample strip 3 is changed.

[0105] Another embodiment of the present invention, as Fig.10As shown in Figure 14-1, a height-adjustable boss 15 can be added to the surface of the auxiliary roller 14, and the upper end of the boss 15 should be as smooth as possible. When the sample strip 3 contacts the boss 15, an upward bulge will occur, which can be used to simulate the stress of the fiber and rubber composite structure of the tire under abnormal conditions such as road bumps.

[0106] In another embodiment of the present invention, Fig.10 As shown in Figures 14-2 and 14-3, the auxiliary roller 14 is composed of a number of adjacent small guide rollers 16 of the same size. Each small guide roller 16 is connected to a telescopic rod 17 at the lower end. When the telescopic rod 17 is extended, the small guide roller 16 connected thereto will be pushed outward, achieving a similar effect as the boss 15. When conducting the test, a mark can be made on the sample strip 3 in advance, and the telescopic rod 17 can be controlled by an optical sensor to continuously switch between the two states. When the marked position of the sample strip 3 moves above a small guide roller 16, the telescopic rod 17 is automatically extended to cause a local bulge deformation at the marked position of the sample strip 3. By repeatedly loading in this way, the fatigue mechanical properties of the marked point position can be studied separately. This experimental method can also be used to conduct targeted tests on dangerous parts such as fiber breakage and overlap points in fiber and rubber composite structures.

[0107] Another embodiment of the present invention, as Fig.11 As shown, a groove 34 of a certain shape and length can be opened on the top of the sample strip 3 to change the shape of the partial cross section. The neutral plane 33 will also change accordingly and will no longer be a plane, but will be controlled by the shape of the groove 34. In this embodiment, assuming that the depth of the groove 34 is h, the position of the neutral plane directly below the groove 34 can be determined by formula (9):

[0108]

[0109] The meanings of the various parameters in the above formula (9) are consistent with the previous text.

[0110] After adjustment by the above formula (9), the shape of the groove 34 in this embodiment is as follows: Fig.11 As shown in FIG. 1 , the neutral plane 33 directly below the groove 34 is transferred to the bottom of the fiber 31, while the neutral plane 33 is still above the groove 34 at other locations. This means that the fiber 31 directly below the groove 34 is subjected to tensile stress in the test, while the other locations are subjected to compressive stress. In this way, the various mechanical performance indicators of the fiber 31 under uneven stress can be explored. It is worth noting that the shape of the groove 34 is not limited to Fig.11 The rectangle shown in can also be a curved shape of various shapes, such as Fig.12 and Fig.13 shown.

[0111] In another embodiment of the present invention, in order to study the mechanical properties of a multi-layer composite material structure, the aforementioned methods can be used to make each layer of fiber produce the stress and strain required by the user.

[0112] The present invention processes the fiber and rubber composite structure into a closed annular strip, and uses a pair of guide rollers with a certain curvature to simulate the bending state of the fiber and rubber composite structure under different curvature radii; at the same time, the guide roller system, the sample strip and the extrusion device are loaded through a lever loading system, so that the sample strip obtains a certain tension; in addition, by controlling the position of the neutral plane of the sample cross section, the cross-sectional size, the tension size and other parameters, the fiber component in the sample can produce a certain compression deformation during the test, and the mechanical properties of the fiber of the sample strip when the compression deformation occurs are tested, so as to provide valuable data for the product reliability of the fiber reinforced rubber.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for testing the tensile and compressive bending fatigue properties of a fiber and rubber composite structure, characterized in that: The test method is based on a test device for tensile and compressive bending fatigue performance of a fiber and rubber composite structure, and the test device includes a guide roller system, a lever loading system, a sample strip and an extrusion preload device; The guide roller system is used as a carrier for the fiber reinforced rubber sample, and includes a fixed guide roller and a sliding guide roller; the rotation axis position of the fixed guide roller is fixed relative to the ground, and the fixed guide roller can rotate around its rotation axis; the sliding guide roller is located directly above the fixed guide roller, and a vertical slide groove is matched in the central area of ​​the sliding guide roller; the rotation axis of the sliding guide roller can slide up and down in the slide groove; the rotation of the sliding guide roller and the fixed guide roller is driven by the same motor; the sample strip is matched and wound around the fixed guide roller and the sliding guide roller; The lever loading system is matched and arranged on one side of the sliding guide roller in the horizontal direction, and one end of the lever loading system is matched and connected with the rotating shaft of the sliding guide roller; the lever loading system applies an upward force to the sliding guide roller by using the lever principle to complete the loading of the sample strip; The extrusion pre-tightening device is matched and arranged on the outside of the sample strip, and is in contact with and connected to the outer surface of the sample strip and applies an extrusion force to the outer surface of the sample strip; The sample strip may be provided with a groove at its top to change the shape of a portion of the cross section of the sample strip, so that the neutral plane of the sample strip is changed and is no longer a plane, but is controlled by the shape of the groove; The specific process of the test method is as follows: after selecting a sample strip of suitable size, the sample strip is installed on a fixed guide roller and a sliding guide roller, the motor speed is set according to the required loading rate, and the sample strip begins to undergo fatigue test; when the sample strip is obviously damaged or partially broken, the sample is judged to be failed and the test ends; finally, the number of revolutions of the sample strip from the beginning of the test to the end of the test is recorded, which is the fatigue life of the sample strip under the corresponding loading conditions; For a sample strip with an asymmetric structure, the distance between the neutral plane of the sample strip and the bottom surface can be solved as shown in the following formula (4): In the above formula (4), L is the total thickness of the sample strip, b is the distance between the fiber (31) and the bottom surface of the sample strip (3), and c is the thickness of the fiber (31); At this time, if the test requires that the compressive strain of the fiber of the sample strip be ε, then: In the above formula (5), F is the constant force transmitted to the sliding guide roller by the lever loading system, A is the total cross-sectional area, and E is the average elastic modulus of the cross-sectional area; The constant force F transmitted to the sliding guide roller by the lever loading system is controlled by the following formula (1): F = 2EAε (1); In the above formula (1), A is the total cross-sectional area, and E is the average elastic modulus of the cross-sectional area, which is calculated as shown in the following formula (2): In the above formula (2), E1 and E2 are the elastic moduli of the fiber and rubber of the sample strip, respectively; A1 and A2 are the areas of the fiber and rubber of the sample strip, respectively, and A1+A2=A; The constant force F transmitted to the sliding guide roller by the lever loading system can be obtained from the above formula (5): Between the sliding guide roller and the fixed guide roller, the sample strip will always remain in a tensile state. The width of the sample strip can be changed in advance according to the actual situation, thereby changing the value of A, so that the tensile strain of the tensile section also meets the test requirements; When all test conditions meet the requirements, make the sliding guide roller and the fixed guide roller run at a certain speed or acceleration, and record the number of turns the sample strip makes from the start of the test to the occurrence of damage. Twice the number of turns is the fatigue life of the sample strip under the test conditions.

2. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 1, characterized in that: The width of the slide groove is equal to the diameter of the rotating shaft of the sliding guide roller, and the rotating shaft of the sliding guide roller does not contact the two ends of the slide groove.

3. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 1, characterized in that: The lever loading system includes a lever, a hook, a hinge point and a lever weight; the hinge point is arranged at the lower part of the lever, the left end is hinged to the rotating shaft of the sliding guide roller, and the right end has a hook for hanging the lever weight distributed at intervals.

4. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 3, characterized in that: The length of the lever body located on the left side of the hinge point is shorter than the length of the lever body located on the right side of the hinge point.

5. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 1, characterized in that: The extrusion pre-tightening device is matched and arranged directly above the sliding guide roller, and includes a device body, a pre-tightening weight, a spring and an extrusion roller; the upper end of the device body is used to place the pre-tightening weight, and the lower end is a concave arc structure and the curvature is consistent with the sliding guide roller; the upper end of the spring is matched and connected with the lower end arc surface of the device body, and the lower end of the spring is matched and connected with the extrusion roller; the lower part of the extrusion roller is matched and contacted with the upper side surface of the sample strip, so as to transfer the load of the extrusion pre-tightening device to the surface of the sample strip for loading.

6. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 5, characterized in that: The extrusion pre-tightening device can also be matched and arranged directly below the fixed guide roller, and apply extrusion force to the lower surface of the sample strip in a bottom-up loading manner.

7. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 1, characterized in that: The extrusion pre-tightening device can adopt an circumscribed circular roller; one axial side of the circumscribed circular roller is open, and the other axial side is closed and a circumscribed circular roller shaft is matched and arranged in the center; the open side of the circumscribed circular roller is used to facilitate the connection between the lever loading system and the rotating shaft of the sliding guide roller; the inner edge of the circumscribed circular roller contacts the top of the sample strip; the circumscribed circular roller shaft can be matched and connected with an external loading device for downward loading, so that the circumscribed circular roller and the sample strip are squeezed at the top of the sliding guide roller.

8. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 1, characterized in that: The extrusion preload device may also use two auxiliary rollers arranged outside the sample strip to achieve the function of bending and loading the sample strip on the other side; and the positions of the two auxiliary rollers may be moved manually to change the load on the sample strip.

9. The method for testing the tensile and compressive bending fatigue properties of the fiber and rubber composite structure according to claim 8, characterized in that: The auxiliary roller may be provided with a height-adjustable boss on its surface; the upper end surface of the boss is smooth and will cause the sample strip to bulge upward when in contact with the sample strip.

10. The method for testing the tensile and compressive bending fatigue properties of a fiber and rubber composite structure as claimed in claim 8, characterized in that: The auxiliary roller can also be composed of several adjacent guide rollers of the same size; the lower end of each guide roller is connected to a telescopic rod; when the telescopic rod is extended, the guide roller connected thereto will be pushed outward; when conducting a test, a mark can be made on the sample strip in advance, and the telescopic rod can be controlled by an optical sensor. When the marked position of the sample strip moves above one of the guide rollers, the telescopic rod is automatically extended to cause a local bulge deformation at the marked position of the sample strip.

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