Construction method of crack growth rate model of spliced rubber

Abstract

The invention provides a construction method of a crack growth rate model of spliced rubber. According to the method, a crack propagation scene of a material interface is constructed by splicing the first sample wafer and the second sample wafer and forming the test crack, so that a mechanical environment of interface crack propagation of the tire in actual use is reproduced, and then, a stress-strain curve of each tensile period is acquired to determine the crack propagation of the tire. And finally, calculating a first coefficient and a second coefficient to correct the initial model by combining the crack growth rates and the maximum strains of the plurality of period groups, so as to obtain the crack expansion rate of each period group and the maximum strain in the period groups. According to the method, the model of the crack growth rate of the spliced rubber material formed based on the combination of the first sample sheet and the second sample sheet is reconstructed so as to accurately represent the crack growth of the interface of the spliced rubber, and the new constructed model can significantly reduce errors, so that the accuracy of tire fatigue life evaluation is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber material testing, and particularly to a method for constructing a crack propagation rate model of bonded rubber. Background Art

[0002] Rubber is a key material for tires, and the crack propagation rate at its interface is a major indicator of tire performance, directly affecting the fatigue life of tires.

[0003] In most cases, the fatigue crack path of tires extends along the rubber interface between adjacent components, and the speed of crack propagation determines the length of service life. Therefore, studying the crack propagation rate between the interfaces of rubber materials with different components is of great significance for improving the fatigue life of tires.

[0004] However, existing testing methods only target the crack propagation rate of a single rubber material. In actual applications, tire fatigue cracks often extend along the interfaces of different rubber materials. Existing methods cannot accurately characterize the interface behavior, and the traditional crack propagation model based on tearing energy has significant errors in the interface propagation scenario, especially when the tearing energy is large, resulting in poor fitting effect and poor accuracy in evaluating the fatigue life of tires. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide.

[0006] In a first aspect, an embodiment of the present invention provides a method for constructing a crack propagation rate model of bonded rubber, and the method is as follows: Obtain a first sample piece and a second sample piece; Bond and splice the first sample piece and the second sample piece to obtain a target sample piece; Cut the target sample piece to obtain a test sample piece with a test crack formed at the junction of the first sample piece and the second sample piece; Under preset experimental parameter conditions, perform a crack tensile test on the test crack on the test sample piece to obtain a test result; wherein, the test result at least includes the stress-strain curve of each tensile cycle; For each cycle group, calculate the crack propagation rate after the tensile test of the cycle group based on the stress-strain curve and determine the maximum strain corresponding to the cycle group; wherein, the cycle group includes a first number of tensile cycles; Substitute all the crack propagation rates and maximum strains into the initial model to calculate the first coefficient and the second coefficient; Determine the crack propagation rate model according to the first coefficient, the second coefficient and the initial model.

[0007] Combined with the first aspect, an embodiment of the present invention provides a first possible implementation manner of the first aspect. The step of bonding and splicing the first sample piece and the second sample piece to obtain a target test piece includes: Freeze the edges of the first sample piece and the second sample piece to form a first bonding edge and a second bonding edge; Splice the first bonding edge and the second bonding edge and perform vulcanization treatment to obtain a target test piece.

[0008] Combined with the first aspect, the embodiment of the present invention provides a first possible implementation manner of the first aspect. The step of freezing the edges of the first sample piece and the second sample piece to form a first bonding edge and a second bonding edge includes: With a freezing depth of 20 to 30 mm, put the edges of the first sample piece and the second sample piece into liquid nitrogen and freeze for 15 to 20 minutes to obtain a first sample piece with a first bonding edge and a second sample piece with a second bonding edge.

[0009] Combined with the first aspect, the embodiment of the present invention provides a first possible implementation manner of the first aspect. The step of freezing the edges of the first sample piece and the second sample piece to form a first bonding edge and a second bonding edge further includes: Put the first sample piece and the second sample piece into a vulcanization mold and splice the first bonding edge and the second bonding edge, and perform vulcanization for 30 min under the conditions of 150 °C and 10 Mpa to obtain a pre-connected sample piece; Cool the pre-connected sample piece to room temperature to obtain a target sample piece.

[0010] Combined with the first aspect, the embodiment of the present invention provides a first possible implementation manner of the first aspect. The step of cutting the target sample piece to obtain a test sample piece with a test crack formed at the junction of the first sample piece and the second sample piece includes: Cut the target sample piece to obtain a pure shear specimen with the junction of the first sample piece and the second sample piece located at the center; Cut the edge of the pure shear specimen along the junction of the first sample piece and the second sample piece to obtain a test sample piece; Wherein, the length of the test crack is 25 mm.

[0011] Combined with the first aspect, the embodiment of the present invention provides a first possible implementation manner of the first aspect. The thickness of the first sample piece is the same as that of the second sample piece, and is greater than or equal to 1.5 mm and less than or equal to 2 mm.

[0012] Combined with the first aspect, the embodiment of the present invention provides a first possible implementation manner of the first aspect. The first sample piece and the second sample piece are mixed rubbers of two different types of rubber materials.

[0013] Combined with the first aspect, the embodiment of the present invention provides a first possible implementation manner of the first aspect. The first sample piece and the second sample piece are rectangular structures with the same size and shape.

[0014] In combination with the first aspect, the embodiments of the present invention provide a first possible implementation manner of the first aspect, and the crack growth rate model is .

[0015] In the second aspect, the present application provides a method for calculating the crack growth rate of spliced rubber. The method includes: Obtaining the maximum strain corresponding to each cycle group in the crack tensile test of the target spliced rubber; Combining the maximum strain and the provided crack growth rate model to calculate the target crack growth rate of the spliced rubber.

[0016] The embodiments of the present invention bring the following beneficial effects: The present invention provides a method for constructing a crack growth rate model of spliced rubber.

[0017] In the present invention, by splicing the first sample piece and the second sample piece and forming a test crack, the crack growth scenario of the material interface is directly constructed, so as to reproduce the mechanical environment of the interface crack growth during the actual use of the tire. Subsequently, by collecting the stress-strain curves of each tensile cycle, the crack growth rate of each cycle group and the maximum strain in the cycle group are obtained. Finally, combining the crack growth rates and the maximum strains of multiple cycle groups, the first coefficient and the second coefficient are calculated to correct the initial model, and a new model of the crack growth rate of the spliced rubber material formed by combining the first sample piece and the second sample piece is reconstructed to accurately characterize the crack growth of the interface of the spliced rubber. The constructed new model can significantly reduce the error, thereby improving the accuracy of tire fatigue life assessment.

[0018] Other features and advantages of the present invention will be described in the following specification, and some of them will become obvious from the specification or be understood by implementing the present invention. The objectives and other advantages of the present invention are achieved and obtained by the structures specifically pointed out in the specification, claims and drawings.

[0019] To make the above objectives, features and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given and detailed descriptions are made in conjunction with the accompanying drawings as follows. Description of the Drawings

[0020] In order to more clearly illustrate the specific implementation manners of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific implementation manners or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1Schematic flow chart of a method for constructing a crack propagation rate model of spliced rubber provided in Embodiment 1 of the present invention. Detailed implementation manners

[0022] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] To facilitate the understanding of this embodiment, the application scenarios and design concepts of the embodiments of the present application are briefly introduced.

[0024] In most cases, the fatigue crack path of a tire extends along the rubber interface between adjacent components. The rate of crack propagation determines the service life. However, current rubber fatigue crack propagation rate experiments only test the crack propagation rate of a single rubber material, and the relationship model between the crack propagation rate and the tearing energy is not applicable to the crack propagation rate at the interface of spliced rubber. When calculating the crack propagation rate using the traditional relationship model between the crack propagation rate and the tearing energy, the greater the tearing energy received by the spliced rubber, the greater the error. Therefore, the present invention proposes a method for constructing a crack propagation rate model of spliced rubber.

[0025] Embodiment 1 Combined with Figure 1 , this embodiment provides a method for constructing a crack propagation rate model of spliced rubber, and the method is as follows: S100, Obtain a first sample piece and a second sample piece.

[0026] S200, Splice and bond the first sample piece and the second sample piece to obtain a target sample piece.

[0027] S300, Cut the target sample piece to obtain a test sample piece with a test crack formed at the junction of the first sample piece and the second sample piece.

[0028] S400, Under preset experimental parameter conditions, perform a crack tensile test on the test crack on the test sample piece to obtain a test result. Among them, the test result at least includes the stress-strain curve of each tensile cycle.

[0029] S500, For each cycle group, calculate the crack propagation rate after the tensile test of the cycle group based on the stress-strain curve and determine the maximum strain corresponding to the cycle group. Among them, the cycle group includes a first number of tensile cycles.

[0030] S600, substitute all crack growth rates and maximum strains into the initial model to calculate the first coefficient and the second coefficient.

[0031] S700, determine the crack growth rate model according to the first coefficient, the second coefficient and the initial model.

[0032] Specifically, in this embodiment, first, the first sample piece and the second sample piece are combined to form a test crack, so as to construct a crack growth scenario of the material interface of the spliced rubber, thereby reproducing the mechanical environment of the interface crack growth during the actual use of the tire.

[0033] Subsequently, by collecting the stress-strain curves of each tensile cycle, the crack growth rate of each cycle group and the maximum strain in the cycle group are obtained.

[0034] Among them, the preset experimental parameters in this embodiment include the frequency and strain range of the reciprocating tensile motion. The frequency is specifically 3 - 8 Hz, and the strain range is 10% - 50%.

[0035] Moreover, in this embodiment, one tensile cycle is 600 reciprocating tensile actions, and one cycle group includes 800 tensile cycles. During the crack tensile test, the stress-strain curve of each tensile cycle is recorded by the experimental equipment.

[0036] In addition, after the end of each tensile cycle, a photo is taken of the tip of the test crack. According to the taken photo, the length of the crack growth in each tensile cycle is calculated, and then divided by the number of times of the tensile cycle, which is the crack growth rate corresponding to this tensile cycle.

[0037] Finally, combining the crack growth rates and maximum strains of multiple cycle groups, the first coefficient and the second coefficient are calculated to correct the initial model, and a new model of the crack growth rate of the spliced rubber material formed by combining the first sample piece and the second sample piece is reconstructed to accurately characterize the crack growth of the interface of the spliced rubber. The constructed new model can significantly reduce the error, thereby improving the accuracy of the tire fatigue life assessment.

[0038] In this embodiment, step S200, the step of splicing the first sample piece and the second sample piece and bonding them to obtain the target test piece includes: S210, freeze the edges of the first sample piece and the second sample piece to form a first bonding edge and a second bonding edge.

[0039] S220, splice the first bonding edge and the second bonding edge and perform vulcanization treatment to obtain the target test piece.

[0040] In this embodiment, first, the edges of the first sample piece and the second sample piece are frozen to increase the elastic modulus at the frozen edges of the first sample piece and the second sample piece, avoiding misalignment caused by material rebound at room temperature.

[0041] Subsequently, through a vulcanization process, the first bonding edge and the second bonding edge of the first sample piece and the second sample piece are bonded, and chemical cross-linking is generated at the bonding position between the first sample piece and the second sample piece. The bonding strength at the bonding position is relatively high, thereby ensuring that the crack propagates along a preset path.

[0042] Among them, step S210, the step of freezing the edges of the first sample piece and the second sample piece to form the first bonding edge and the second bonding edge, includes: S211, with a freezing depth of 20 mm to 30 mm, put the edges of the first sample piece and the second sample piece into liquid nitrogen and freeze for 15 minutes to 20 minutes to obtain the first sample piece with the first bonding edge and the second sample piece with the second bonding edge.

[0043] To ensure that the frozen area can cover the edge areas of the first sample piece and the second sample piece so that the widths of the first bonding edge and the second bonding edge can resist tensile stress, it is necessary to ensure that the freezing depth of the first sample piece and the second sample piece is not less than 20 mm. In this embodiment, the freezing depth is specifically 25 mm. At this freezing depth and with a freezing duration of 15 to 20 minutes for the first sample piece and the second sample piece, the temperature of the rubber can be reduced below the glass transition temperature, enabling the first sample piece and the second sample piece to be fully tempered, thereby avoiding springback during splicing.

[0044] In this embodiment, step S210, the step of freezing the edges of the first sample piece and the second sample piece to form the first bonding edge and the second bonding edge, further includes: S212, put the first sample piece and the second sample piece into a vulcanization mold and splice the first bonding edge and the second bonding edge, and vulcanize for 30 min under the conditions of 150 °C and 10 Mpa to obtain a pre-connected sample piece.

[0045] S213, cool the pre-connected sample piece to room temperature to obtain the target sample piece.

[0046] In an environment of 150 °C, the vulcanizing agent can be activated to promote the cross-linking reaction of rubber molecular chains, enabling the first bonding edge and the second bonding edge to achieve firm bonding.

[0047] Moreover, in this embodiment, maintaining the vulcanization pressure at 10 Mpa during the vulcanization process can eliminate the interfacial voids between the first sample piece and the second sample piece, further improving the uniformity of bonding and avoiding local stress concentration in the whole after bonding.

[0048] In this embodiment, step S300, the step of cutting the target sample piece to obtain a test sample piece with a test crack formed at the junction of the first sample piece and the second sample piece, includes: S310, cut the target sample piece to obtain a pure shear specimen with the junction of the first sample piece and the second sample piece located at the center.

[0049] S320, cut the edge of the pure shear specimen along the junction of the first sample piece and the second sample piece to obtain a test sample piece.

[0050] Among them, the length of the test crack is 25 mm.

[0051] To ensure the accuracy of each group of test data, in this embodiment, the target test piece is cut to ensure the accuracy of each test.

[0052] Specifically, in this embodiment, the test sample piece formed by the building materials is 150 mm long and 25 mm wide, and the junction line of the first sample piece and the second sample piece is parallel to the long side and located at the midline of the wide side. Under this structure, the crack propagation path can be controlled by the interface, and at the same time, the interference of geometric deviation on the test results can be eliminated.

[0053] In addition, the length of the test crack in this embodiment is 25 mm, which can ensure that the tip of the test crack is in a pure shear stress field, avoiding the fracture of the test sample piece during the tensile test.

[0054] It should be noted here that in this embodiment, the thickness of the first sample piece is the same as that of the second sample piece, and is greater than or equal to 1.5 mm and less than or equal to 2 mm.

[0055] Within this thickness range, it can avoid the edge warping or local tearing of the first sample piece and the second sample piece due to being too thin, and at the same time, it can also prevent non-uniform deformation caused by being too thick.

[0056] Moreover, in this embodiment, the first sample piece and the second sample piece are mixed rubbers of two different types of rubber materials.

[0057] Under the condition that the first sample piece and the second sample piece adopt heterogeneous rubber materials, the authenticity of the simulated tire interface can be further ensured, thereby improving the matching degree of experimental data with actual working conditions.

[0058] It should be noted here that in this embodiment, the first sample piece and the second sample piece are rectangular structures with the same size and shape.

[0059] Specifically, in this embodiment, both the first sample piece and the second sample piece are rectangular sample pieces of 165 mm × 75 mm. The same size of the two sample pieces can eliminate the interference of geometric differences on the tensile strain, thereby further ensuring the accuracy of the test.

[0060] Moreover, in this embodiment, the first bonding edge and the second bonding edge are respectively the long sides of the first sample piece and the second sample piece.

[0061] In addition, in this embodiment, in the crack tensile test in step S400, first, the test sample is placed in the fixture. The upper fixture clamps one side of the first sample away from the second sample, and at the same time, the lower fixture clamps one side of the second sample away from the first sample. Subsequently, the upper fixture and the lower fixture are driven to perform a reciprocating tensile action along the width direction of the test sample.

[0062] It should be noted that the widths of the test samples clamped by the upper fixture and the lower fixture are the same, that is, the clamping depths are the same, so as to ensure that the stress during stretching can be evenly distributed.

[0063] Moreover, the ratio of the distance between the upper fixture and the lower fixture (i.e., the height of the effective test area) to the test sample is not less than 10, to avoid unexpected fracture caused by instability. At the same time, the tip stress field of the test crack under this condition is closer to the theoretical model.

[0064] In this embodiment, the crack growth rate model is .

[0065] Wherein, is the crack growth rate, is the maximum strain per cycle, and a and b are is the parameter for linear fitting with 1 + i.e., the first coefficient and the second coefficient.

[0066] This embodiment uses to replace the tearing energy variable, thus avoiding the influence of the interface bonding strength and the strain field mutation in the traditional model. The goodness of fit is higher than that of the traditional model, and the model error is reduced, especially suitable for the high-load working conditions of tires.

[0067] Specifically, in this embodiment, the finally constructed crack growth rate model of the spliced rubber is .

[0068] Embodiment 2 This embodiment provides a method for calculating the crack growth rate of spliced rubber. The method includes: Obtain the maximum strain corresponding to each cycle group in the crack tensile test of the target spliced rubber.

[0069] Combine the maximum strain and the crack growth rate model provided in Embodiment 1 to calculate the target crack growth rate of the spliced rubber.

[0070] In this embodiment, after obtaining the maximum strain corresponding to each cycle group, substituting the maximum strain into the crack growth rate model constructed in Embodiment 1 can quickly calculate the crack growth rate of the target spliced rubber. That is, by obtaining the of the target spliced rubber and substituting into the crack growth rate model constructed in Embodiment 1, namely it can be obtained through calculation The calculation is simple, fast and highly accurate.

[0071] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the above-described systems and devices can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0072] In addition, in the description of the embodiments of the present invention, unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0073] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0074] Finally, it should be noted that the above embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments, or can easily think of changes, or make equivalent replacements for some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for constructing a crack growth rate model for spliced ​​rubber, characterized in that: The method is as follows: Obtain a first sample and a second sample; splicing the first sample piece and the second sample piece and bonding them together to obtain a target sample piece; Cutting the target sample to obtain a test sample having a test crack formed at the junction of the first sample and the second sample; Under preset experimental parameter conditions, a crack tensile test is performed on the test crack on the test specimen to obtain a test result; wherein the test result at least includes a stress-strain curve of each tensile cycle; For each cycle group, the crack growth rate after the tensile test of the cycle group is calculated based on the stress-strain curve and the maximum strain corresponding to the cycle group is determined; wherein the cycle group includes a first number of the tensile cycles; Substituting all of the crack growth rates and the maximum strain into an initial model to calculate a first coefficient and a second coefficient; The crack growth rate model is determined according to the first coefficient, the second coefficient and the initial model.

2. The method according to claim 1, characterized in that The step of splicing and bonding the first sample piece and the second sample piece to obtain a target test piece includes: Freezing the edges of the first sample sheet and the second sample sheet to form a first bonding edge and a second bonding edge; The first bonding edge and the second bonding edge are spliced ​​and vulcanized to obtain the target test piece.

3. The method according to claim 2, characterized in that The step of freezing the edges of the first sample sheet and the second sample sheet to form a first bonding edge and a second bonding edge comprises: The edges of the first sample piece and the second sample piece are placed in liquid nitrogen and frozen for 15 to 20 minutes at a freezing depth of 20 mm to 30 mm to obtain a first sample piece with the first bonding edge and a second sample piece with the second bonding edge.

4. The method according to claim 3, characterized in that The step of freezing the edges of the first sample sheet and the second sample sheet to form a first bonding edge and a second bonding edge further comprises: Put the first sample sheet and the second sample sheet into a vulcanization mold, splice the first bonding edge and the second bonding edge, and vulcanize for 30 minutes at 150° C. and 10 MPa to obtain a pre-connected sample sheet; The pre-connected sample was cooled to room temperature to obtain the target sample.

5. The method according to claim 1, characterized in that The step of cutting the target sample to obtain a test sample having a test crack formed at the junction of the first sample and the second sample includes: Cutting the target sample to obtain a pure shear specimen with the junction of the first sample and the second sample located at the center; Cutting the edge of the pure shear specimen along the boundary between the first specimen and the second specimen to obtain the test specimen; Wherein, the length of the test crack is 25 mm.

6. The method according to claim 1, characterized in that The thickness of the first sample sheet is the same as the thickness of the second sample sheet, and is greater than or equal to 1.5 mm and less than or equal to 2 mm.

7. The method according to claim 1, characterized in that The first sample piece and the second sample piece are mixed rubbers of two different types of rubber materials.

8. The method according to claim 1, characterized in that The first sample piece and the second sample piece are rectangular structures with the same size and shape.

9. The method according to claim 1, characterized in that: The crack growth rate model is .

10. A method for calculating crack growth rate of spliced ​​rubber, characterized in that: The method comprises: Obtain the maximum strain corresponding to each cycle group in the crack tensile test of the target spliced ​​rubber; The target crack growth rate of the spliced ​​rubber is calculated by combining the maximum strain and the crack growth rate model according to any one of claims 1 to 9.

Images