Calculation method and device for crack growth rate of rubber material and computer terminal

Abstract

The invention provides a method and device for calculating the crack propagation rate of a rubber material and a computer terminal.The method comprises the steps that the change of structural parameters of a unit rubber material under pure shear deformation is recognized, the change of the structural parameters is processed, and the network chain conformation entropy change of the rubber material is obtained; obtaining rubber free energy change according to the network chain conformation entropy change, and obtaining a stress-strain corresponding relation based on the rubber free energy change and the network chain conformation entropy change; obtaining the strain energy density of the macroscopic rubber material according to the stress-strain corresponding relation, obtaining a tearing energy peak value based on the strain energy density, and then obtaining the crack growth rate by combining the calculation logic of a crack growth rate model of Lake-Lidley. According to the method, a new calculation model of the crack growth rate is provided from the principle, and a theoretical basis is provided for life prediction and maintenance of rubber materials, rubber design and modification, fault analysis and damage tolerance design.

Description

Technical Field

[0001] The invention relates to the technical field of rubber mechanical property calculation, and in particular to a method, a device and a computer terminal for calculating the crack growth rate of a rubber material. Background Art

[0002] Rubber materials, as a class of polymer materials with remarkable high elasticity, play an indispensable role in the industrial field due to their excellent physical and mechanical properties. These properties include high elasticity, good wear resistance, excellent sealing and corrosion resistance, making rubber materials an ideal choice for manufacturing key components such as tires, shock absorbers, and seals. However, these rubber products often face complex cyclic loads in practical applications, which leads to stress concentration and crack propagation inside the material, and ultimately causes fatigue failure. Therefore, studying the fatigue crack growth rate of rubber materials is of great significance for predicting their fatigue life and improving product reliability.

[0003] Fatigue failure of rubber is usually caused by defects inside the material gradually forming tiny cracks under cyclic loads. These cracks continue to expand over time until they eventually lead to product failure. At present, the calculation model of rubber crack growth rate mainly relies on the fitting analysis of experimental data. Although the functional relationship between crack growth rate and tear energy can provide certain prediction capabilities, it lacks sufficient theoretical basis and is difficult to explain the physical mechanism of crack growth in essence. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method, device and computer terminal for calculating the crack growth rate of rubber materials, which not only proposes a new calculation model of crack growth rate based on principle, but also provides a theoretical basis for life prediction and maintenance of rubber materials, rubber design and modification, fault analysis, and damage tolerance design.

[0005] In a first aspect, an embodiment of the present invention provides a method for calculating the crack growth rate of a rubber material, comprising: identifying changes in structural parameters of a unit rubber material under pure shear deformation, processing the changes in the structural parameters, and obtaining a network chain conformational entropy change of the rubber material; obtaining a rubber free energy change according to the network chain conformational entropy change, and obtaining a stress-strain correspondence relationship based on the rubber free energy change and the network chain conformational entropy change; obtaining a strain energy density of a macroscopic rubber material according to the stress-strain correspondence relationship, and further obtaining a tear energy peak value based on the strain energy density; based on the tear energy peak value, using the calculation logic of the Lake-Lindley crack growth rate model to obtain the crack growth rate.

[0006] In a preferred embodiment of the present invention, the change of structural parameters of a unit rubber material under pure shear deformation is identified, the change of the structural parameters is processed, and the network chain conformation entropy change of the rubber material is obtained, including: in a three-dimensional coordinate system, the change of the structural parameters includes the elongation ratio of the unit rubber material in different axial directions; based on the elongation ratios in different axial directions, according to the functional relationship between the network chain conformation entropy and the elongation ratios in different axial directions, the change of the elongation ratios in different axial directions is processed to obtain the network chain conformation entropy change of the rubber material.

[0007] In a preferred embodiment of the present invention, the structural parameters include λ x , y and λ z ; The network chain conformation entropy change ΔS = m(k, N, λ x ,λ y ,λ z ), where k is the Boltzmann constant, N is the number of cross-linked networks; λ x is the elongation ratio in the x-axis direction when the unit cubic rubber specimen is deformed; y is the elongation ratio in the y-axis direction when the unit cubic rubber specimen is deformed; z It is the elongation ratio in the z-axis direction when the unit cubic rubber specimen is deformed.

[0008] In a preferred embodiment of the present invention, the free energy change of the rubber is obtained according to the network chain conformation entropy change, and the corresponding relationship between the stress and the strain is obtained based on the free energy change of the rubber and the network chain conformation entropy change, including: based on the internal energy change ΔU of the rubber material under pure shear deformation, combined with the functional relationship between the free energy change ΔF and the network chain conformation entropy change ΔS, the corresponding relationship between the stress and the strain is obtained as σ=p(ε); wherein ε is the strain of the rubber material.

[0009] In a preferred embodiment of the present invention, the internal energy of the rubber material remains unchanged under pure shear deformation ΔU=0; the functional relationship between the free energy change ΔF and the network chain conformation entropy change ΔS is ΔF=ΔU-TΔS=TΔS; and the corresponding relationship between stress and strain is obtained as σ=p(ε).

[0010] In a preferred embodiment of the present invention, the strain energy density of the macro rubber material is obtained according to the stress-strain correspondence, and the tear energy peak value is obtained based on the strain energy density, including: based on the stress-strain correspondence σ=p(ε), and the calculation formula of the strain energy density u ε =∫σdε, and obtain the functional relationship between the strain energy density and the strain; bring the functional relationship between the strain energy density and the strain into the macroscopic size for calculation, and then obtain the tearing energy peak value.

[0011] In a preferred embodiment of the present invention, based on the tear energy peak value, the calculation logic of the Lake-Lindley crack growth rate model is used to obtain the crack growth rate, including: according to the relationship between the tear energy peak value and the strain in the tear energy peak value, combined with the calculation logic of the Lake-Lindley crack growth rate model, the tear energy peak value is processed to obtain the functional relationship between the crack growth rate r and the strain ε, r=f(ε); wherein ε is the strain of the rubber material.

[0012] In a second aspect, an embodiment of the present invention further provides a calculation device for the crack growth rate of a rubber material, comprising: a data acquisition module for identifying changes in structural parameters of a unit rubber material under pure shear deformation; a first data processing module for processing the changes in structural parameters to obtain the network chain conformational entropy change of the rubber material; a second data processing module for obtaining the rubber free energy change according to the network chain conformational entropy change, and obtaining a stress-strain correspondence relationship based on the rubber free energy change and the network chain conformational entropy change; a third data processing module for obtaining the strain energy density of a macroscopic rubber material according to the stress-strain correspondence relationship, and further obtaining a tear energy peak value based on the strain energy density; and a fourth data processing module for obtaining the crack growth rate based on the tear energy peak value using the calculation logic of the Lake-Lindley crack growth rate model.

[0013] In a third aspect, an embodiment of the present invention further provides a computer terminal including a processor and a memory, wherein the memory stores a computer program, and the processor is used to execute the computer program to implement the method for calculating the crack growth rate of the rubber material of the first aspect.

[0014] In a fourth aspect, an embodiment of the present invention further provides a readable storage medium storing a computer program, which, when executed on a processor, executes the method for calculating the crack growth rate of a rubber material according to the first aspect.

[0015] The embodiments of the present invention bring the following beneficial effects:

[0016] The embodiment of the present invention provides a method, device and computer terminal for calculating the crack growth rate of a rubber material. By identifying the change of the structural parameters of a unit rubber material under pure shear deformation, the change of the structural parameters is processed to obtain the network chain conformation entropy change of the rubber material; the rubber free energy change is obtained according to the network chain conformation entropy change, and the stress-strain correspondence is obtained based on the rubber free energy change and the network chain conformation entropy change; the strain energy density of the macro rubber material is obtained according to the stress-strain correspondence, and the tear energy peak value is obtained based on the strain energy density; based on the tear energy peak value, the crack growth rate is obtained using the calculation logic of the Lake-Lindley crack growth rate model. In this method, not only a new crack growth rate calculation model is proposed based on the principle, but also a theoretical basis is provided for the life prediction and maintenance of rubber materials, rubber design and modification, fault analysis, and damage tolerance design.

[0017] Other features and advantages of the present invention will be set forth in the following description, or some features and advantages may be inferred or unambiguously determined from the description, or may be learned by implementing the above-mentioned technology of the present disclosure.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 described below 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.

[0020] Figure 1 A flow chart of a first method for calculating a crack growth rate of a rubber material provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of a rubber unit cube in a uniform strain state used in an embodiment of the present invention;

[0022] Figure 3 A flow chart of a second method for calculating the crack growth rate of a rubber material provided by an embodiment of the present invention;

[0023] Figure 4 A flow chart of a third method for calculating the crack growth rate of a rubber material provided by an embodiment of the present invention;

[0024] Figure 5 Process pictures of application examples and the shape of the specimens used;

[0025] Figure 6 The measured curve and the fitted curve obtained for the verification example;

[0026] Figure 7 A schematic diagram of the structure of a device for calculating the crack growth rate of a rubber material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0028] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0030] Furthermore, the terms “first”, “second”, “third”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0031] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present invention belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present invention.

[0032] Crack growth rate refers to the rate of change of crack length with the number of cycles under fatigue load, which reflects the speed of crack growth. There is a close relationship between crack growth rate and material properties. Rubber materials are polymer elastomers with unique mechanical properties. The prior art generally believes that the crack growth rate of rubber materials is affected by factors such as its viscoelastic properties, flexibility, and tensile strength.

[0033] An embodiment of the present invention provides a method for calculating the crack growth rate of a rubber material. The method can be applied to electronic devices, such as computers, smart terminals, and vehicle-mounted terminals.

[0034] See also Figure 1 , the calculation method of the crack growth rate of rubber materials includes the following steps:

[0035] Step S102: identifying changes in structural parameters of the unit rubber material under pure shear deformation, processing the changes in the structural parameters, and obtaining a network chain conformation entropy change of the rubber material;

[0036] When studying the mechanical behavior of rubber materials, rubber materials are considered to be isotropic materials, that is, materials with the same physical properties in all directions. For isotropic elastic bodies such as rubber, after being subjected to uniform strain, all parts of its internal structure will respond to external forces in the same way.

[0037] Pure shear deformation is a specific deformation mode in which the rubber material deforms parallel to the shear plane, but not in other directions. In this deformation mode, the direction and length of the two principal strain lines of the rubber material change with the progressive deformation, but no rotation of the principal axis occurs. This mode helps to simplify the analysis process of crack growth because it excludes the influence of rotational deformation or non-coaxial deformation under complex stress states.

[0038] In pure shear deformation, the stress state inside the material is relatively simple, mainly composed of shear stress, without the effect of normal stress. This simplified stress state helps to more accurately calculate the relationship between stress and strain, and thus predict the crack growth rate.

[0039] Step S104: obtaining the rubber free energy change according to the network chain conformation entropy change, and obtaining a stress-strain correspondence relationship based on the rubber free energy change and the network chain conformation entropy change;

[0040] The change of network chain conformational entropy refers to the fact that in the molecular chain network of rubber materials, due to the flexibility and randomness of the molecular chain, the molecular chain can take a variety of different spatial conformations. These different conformations constitute the conformational entropy of the molecular chain. When the rubber material is subjected to external force, the conformation of the molecular chain will change, resulting in a change in conformational entropy.

[0041] In other words, when the rubber material is subjected to external force, pure shear deformation occurs, and the structural parameters of the rubber material will change, which in turn leads to changes in the network chain conformation entropy.

[0042] Free energy change refers to the amount of energy change in thermodynamics when a system changes from one state to another. It is the part of the system energy that can be used to do work. Free energy change is related to stress change, while the network chain conformation entropy change is related to strain. Through the relationship between free energy change and network chain conformation entropy change, the corresponding relationship between stress and strain can be obtained.

[0043] Step S106: obtaining the strain energy density of the macroscopic rubber material according to the stress-strain correspondence relationship, and obtaining the tear energy peak value based on the strain energy density;

[0044] Strain energy density is the strain energy per unit cubic volume of the rubber material. It reflects the amount of energy stored in the unit cubic volume when the rubber material is deformed under the action of external force.

[0045] Peak tearing energy refers to the maximum value of the energy required per unit area when the crack expands during the material tearing process.

[0046] Step S108: Based on the tear energy peak value, the crack growth rate is obtained using the calculation logic of the Lake-Lindley crack growth rate model.

[0047] The Lake-Lindley model was proposed by Lake and Lindley to describe the crack growth behavior of rubber materials under dynamic loading. The model identifies four different growth mechanisms or regions during the fatigue crack growth of rubber:

[0048] When the tear energy is lower than the threshold tear energy T0, the crack extension is not related to mechanical load, but to ozone and oxygen aging. T0 is also called the threshold tear energy, which is the minimum tear energy required to promote crack extension.

[0049] At T0 and the transition tearing energy T t The crack growth rate r is linearly related to the tearing energy, T t For the transition tear energy. t To the critical tearing energy T c The crack growth rate and tearing energy show a power law relationship. If the tearing energy T is greater than T c , the crack will become unstable and the material will fail rapidly.

[0050] The above calculation method comprehensively considers the change in network chain conformation entropy caused by the change in the structural parameters of the rubber material and the change in free energy under pure shear deformation, and obtains the corresponding relationship between stress and strain, and then obtains the peak value of tear energy. Based on the peak value of tear energy, the crack growth rate can be accurately calculated using the calculation logic of the Lake-Lindley crack growth rate model.

[0051] In the field of fatigue life prediction of rubber materials, although the traditional experimental data fitting analysis method can provide certain prediction capabilities, it is limited by the experimental conditions and accidental factors, and its prediction accuracy and reliability are limited. In order to overcome this limitation, researchers began to combine the theoretical properties of rubber materials with experimental data to develop more accurate theoretical tools. This method not only reduces the randomness of experimental results, but also improves the accuracy and universality of the prediction model by deeply understanding the intrinsic mechanism of the material.

[0052] First, the analysis method combined with theoretical performance can provide a solid theoretical basis for the fatigue life prediction of rubber materials. By considering the molecular structure, network morphology and deformation mechanism of rubber under external force, technicians in this field can more accurately describe the response behavior of the material under cyclic loading. This analysis method guided by theory makes the prediction of fatigue life no longer rely solely on empirical data, but has a more scientific basis.

[0053] Secondly, this theoretical tool provides important guidance for the design and modification of rubber products. During the design process, by predicting the impact of different material formulations or structural designs on fatigue life, technicians in this field can optimize the performance of the product and improve its reliability and durability in practical applications. In addition, for existing rubber products, this theoretical tool also helps to evaluate their remaining life and provide scientific decision support for maintenance and replacement.

[0054] Furthermore, this theoretical analysis method also plays a key role in fault analysis and damage tolerance design. By simulating the crack propagation behavior of rubber materials under different load conditions, technicians in this field can identify the weak links that may lead to failures and design safer damage tolerance. This not only improves the safety of the product, but also provides an important reference for the reliability design of materials.

[0055] Considering that if there are too many parameters, there will be a certain amount of redundant parameters that increase unnecessary calculations. Therefore, according to the accuracy requirements of the crack growth rate of rubber materials in practical applications, in a possible implementation of the present invention, Figure 3 As shown, the method for calculating the crack growth rate of the rubber material comprises the following steps:

[0056] Step S202: In the three-dimensional coordinate system, the changes in the structural parameters include the elongation ratios λ of the unit rubber material in different axial directions. x , y and λ z ; Based on different axial elongation ratios λ x , y and λ z According to the functional relationship between the network chain conformation entropy and the elongation ratios in different axial directions, the changes in the elongation ratios in different axial directions are processed to obtain the network chain conformation entropy change of the rubber material.

[0057] When a unit cube is taken out of the rubber material after being stressed, the dimensions of the force on this unit cube in the three main axis directions will change, such as Figure 2 As shown. The force analysis of the unit cube is the basis for studying the macroscopic mechanical behavior of rubber materials. The unit cube refers to a cubic element with a side length of 1. By analyzing the stress and strain of this microscopic element, the mechanical properties of the macroscopic rubber material can be derived.

[0058] The network chain conformation entropy change of rubber materials is based on the network chain conformation entropy change ΔS=m(k,N,λ x ,λ y ,λ z );

[0059] Among them, k is the Boltzmann constant, N is the number of cross-linked network chains;

[0060] λ x is the elongation ratio in the x-axis direction when the unit cubic rubber specimen is deformed;

[0061] λ y is the elongation ratio in the y-axis direction when the unit cubic rubber specimen is deformed;

[0062] λ z It is the elongation ratio in the z-axis direction when the unit cubic rubber specimen is deformed.

[0063] Step S204: Based on the internal energy change ΔU of the rubber material under pure shear deformation, combined with the functional relationship between the free energy change ΔF and the network chain conformation entropy change ΔS, the corresponding relationship between stress and strain is obtained as σ=p(ε); wherein ε is the strain of the rubber material.

[0064] In a preferred embodiment of the present invention, the internal energy of the rubber material remains unchanged under pure shear deformation ΔU=0; the functional relationship between the free energy change ΔF and the network chain conformation entropy change ΔS is ΔF=ΔU-TΔS=TΔS; and the corresponding relationship between stress and strain is obtained as σ=p(ε).

[0065] Step S206: Based on the stress-strain correspondence σ=p(ε) and the calculation formula of strain energy density u ε =∫σdε, and obtain the functional relationship between the strain energy density and the strain; bring the functional relationship between the strain energy density and the strain into the macroscopic size for calculation, and then obtain the tear energy peak value T max =j(u ε ,h).

[0066] Step S208: Based on the relationship between the tear energy peak value and the strain in the tear energy peak value, combined with the Lake-Lindley crack growth rate model r = g (C, D, T max ) calculation logic, the tear energy peak is processed to obtain the functional relationship between the crack growth rate r and the strain ε, r=f(ε); wherein ε is the strain of the rubber material.

[0067] Among them, C and D are constants, T max It is the peak tearing energy of the rubber pure shear specimen.

[0068] The above crack growth rate function fully considers the stress conditions of the rubber material under pure shear deformation, as well as the network chain conformation entropy change, internal energy change ΔU, and free energy change ΔF of the rubber material under pure shear deformation. Combined with the calculation logic of the Lake-Lindley crack growth rate model, the obtained crack growth rate function is closer to the actual situation and has higher reliability.

[0069] As a possible implementation, see Figure 4 , the specific crack growth rate of rubber material is obtained by the following steps:

[0070] Step S302, obtaining the elongation ratios λ in different axial directions when the cubic rubber specimen is deformed x , y and λ z , according to ΔS=m(k,N,λ x ,λ y ,λ z ) Calculate the entropy change of the network chain conformation.

[0071] Based on different axial elongation ratios λ x , y and λ z , according to the polymer material network chain conformation chain entropy changes can include:

[0072] ΔS=m(k,N,λ x ,λ y ,λ z )=-m1kN(λ x 2 +λ y2 +λ z 2 -m2)

[0073] Among them, m1 is a constant, k is the Boltzmann constant, and N is the number of chains in the cross-linked network.

[0074] Furthermore, the value range of m1 is 0.1 to 0.8, preferably 0.5.

[0075] Furthermore, the value range of m2 is 1 to 5, preferably 3.

[0076] Step S304, the internal energy of the cross-linked network in the rubber material remains unchanged under pure shear deformation ΔU=0, based on the functional relationship between the free energy change ΔF and the network chain conformation entropy change ΔS ΔF=ΔU-TΔS=TΔS; and then the corresponding relationship between stress and strain is obtained as σ=p(ε).

[0077] In the isochoric process, the work done by the external force on the system is equal to the increase in the free energy of the system, so:

[0078] W=ΔF=m1kN(λ x 2 +λ y 2 +λ z 2 -m2).

[0079] For plane stretching, it is assumed that the stretching is performed in one direction and the volume does not change during stretching, that is, λ x ×λ y ×λ z =1, then λ x =λ,λ y =1,λ z =1 / λ, then

[0080]

[0081] So

[0082] And because dW=fdl, then:

[0083]

[0084] Among them, f is the applied external force, l0 is the length before deformation, l is the length after deformation, and A0 is the area before deformation.

[0085] but

[0086] Where N1 is the number of network chains per unit volume of the sample, N1 can also be used to represent the average molecular weight of the chains between cross-linking points. express,

[0087] Where N A is Avogadro's constant, and ρ is the polymer density. R is the ideal gas constant, and λ=1+ε, then the relationship between stress and strain is:

[0088]

[0089] In another formula So

[0090] Step S306: Calculate the strain energy density u based on the corresponding relationship between stress and strain ε .

[0091] Specifically,

[0092] According to Taylor expansion, we know

[0093] The calculation formula of strain energy density is u ε =A(1+2ε 2 ).

[0094] Step S308, according to the strain energy density u ε , calculate the peak tear energy T of the rubber material max .

[0095] T max =u ε h=A(1+2ε 2 )·h

[0096] Step S310: According to the crack growth rate model of Lake-Lindley, when T0 <T max <T t When the crack growth rate of rubber is:

[0097] r=C·T max -D=C·A·h·(1+2ε 2 )-D=a·(1+2ε 2 )-D;

[0098] Where D = CT0-r z , T0 is the threshold tearing energy, T t For the turning tearing energy, r z is the crack growth rate when the peak tearing energy is less than T0; C is a constant, D is a constant; a=C·A·h.

[0099] It can be seen that the crack growth rate r of the rubber material is related to 1+2ε 2 There is a linear relationship.

[0100] Application Examples

[0101] Taking a filled natural rubber material as an example, the crack growth rate of the material is calculated by applying the above calculation method of the crack growth rate of the rubber material:

[0102] Step S402: According to the density of the rubber material ρ=1.34×10 6 g / m 3 , R = 8.314 J / (mol·K), T = 295.15 K and average molecular weight The calculated A value is 8.07×10 5 .

[0103] Step S404: The initial clamping height of the rubber material is h = 10.51 mm, C = 9.93 × 10 -12 , D = 8.51 × 10 -5 , a is calculated to be 8.43×10 -5 .

[0104] Step S406: According to r=a·(1+2ε 2 )-D, the calculation formula for the crack growth rate is r = 8.43 × 10 -5 ·(1+2ε 2 )-8.51×10 -5 .

[0105] When the strain ε is equal to 0.15, the crack growth rate r = 1.99 × 10 -6 mm / cycle.

[0106] Verification Example

[0107] The same filled natural rubber as in the application example is made into a specimen with a length of 150 mm, a width of 25 mm, and a thickness of 1.5 mm. A 25 mm long crack is cut in the middle of one side. The specimen is placed in a clamp and clamped. The ratio of the specimen length (L) to the initial clamping height (h) is not less than 10. Figure 5 When the machine is in operation, the lower fixture is fixed and the upper fixture moves in a sinusoidal manner. The displacement and force of the fixture are recorded by the sensor. There is a camera in front of the specimen to take pictures of the crack tip.

[0108] The experiment is variable amplitude loading, with an initial strain of 10%. After every 400 cycles (400 cycles are called 1 cycle), the camera takes a photo, and the strain increases by 0.08%, and then the next cycle of the experiment is carried out. The experiment has a total of 500 cycles, and the strain of the 500th cycle is 50%. Use image recognition software to identify crack photos, obtain the size change of the crack, and then get the crack growth rate r. According to the displacement output by the test equipment, calculate the strain ε corresponding to each cycle, and you can get the crack growth rate r and 1+2ε 2 Test curve. Use the linear fitting function of origin to fit the curve and get Figure 6 .

[0109] Crack growth rate r = 8.43 × 10 -5 ·(1+2ε 2 )-8.51×10 -5 .

[0110] It can be seen from the application examples and verification examples that the calculated value of the crack growth rate provided by the present invention is moderately good to the measured value, and the calculated value basically reflects the measured value, which shows that the calculation method of the crack growth rate of the rubber material provided by the present invention is feasible.

[0111] Corresponding to the above method, an embodiment of the present invention further provides a device for calculating the crack growth rate of a rubber material, see Figure 7 , the computing device comprises:

[0112] The data acquisition module 32 is used to identify the changes in the structural parameters of the unit rubber material under pure shear deformation.

[0113] The first data processing module 34 is used to process the change of the structural parameters and obtain the network chain conformation entropy change of the rubber material.

[0114] The second data processing module 36 is used to obtain the rubber free energy change according to the network chain conformation entropy change, and obtain the corresponding relationship between the rubber free energy change and the network chain conformation entropy change.

[0115] The third data processing module 38 is used to obtain the strain energy density of the macroscopic rubber material according to the stress-strain correspondence relationship, and further obtain the tear energy peak value based on the strain energy density.

[0116] The fourth data processing module 40 is used to obtain the crack growth rate based on the tear energy peak value using the calculation logic of the Lake-Lindley crack growth rate model.

[0117] The above-mentioned calculation device for the crack growth rate of rubber materials is based on the crack growth rate model function obtained by pre-simulation, and comprehensively considers the changes in structural parameters, the entropy change of the network chain conformation and the influence of the inherent parameters of the material on the crack growth rate, and calculates the crack growth rate accordingly. The parameters considered in this way are more comprehensive and closer to the actual situation, and the crack growth rate calculated by the crack growth rate model obtained by pre-simulation is more accurate, and the parameterized calculation method can greatly reduce the calculation time, improve efficiency, and provide reliable data guarantee for material design.

[0118] The functional modules or units in various embodiments of the present invention may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0119] A third aspect of the present invention provides a computer terminal, the computer terminal comprising a processor and a memory, the memory storing a computer program, and the processor being used to execute the computer program to implement a method for calculating a crack growth rate of a rubber material.

[0120] A fourth aspect of the present invention provides a readable storage medium storing a computer program, wherein the computer program executes a method for calculating a crack growth rate of a rubber material when the computer program is run on a processor.

[0121] In some embodiments of the present invention, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and structure diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, program segment or a part of the code contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in an alternative implementation, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the structure diagram and / or the flow diagram, and the combination of boxes in the structure diagram and / or the flow diagram, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0122] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0123] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; 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 be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for calculating the crack growth rate of a rubber material, characterized in that: The calculation method includes: Identify the changes in structural parameters of unit rubber materials under pure shear deformation, process the changes in structural parameters, and obtain the entropy change of the network chain conformation of the rubber material; Obtaining the free energy change of the rubber according to the entropy change of the network chain conformation, and obtaining the corresponding relationship between the stress and strain based on the free energy change of the rubber and the entropy change of the network chain conformation; Obtaining the strain energy density of the macroscopic rubber material according to the stress-strain correspondence relationship, and obtaining the tear energy peak value based on the strain energy density; Based on the tear energy peak value, the crack growth rate is obtained using the calculation logic of the Lake-Lindley crack growth rate model.

2. The calculation method according to claim 1, characterized in that: Identify the changes in the structural parameters of the unit rubber material under pure shear deformation, process the changes in the structural parameters, and obtain the network chain conformation entropy change of the rubber material, including: In the three-dimensional coordinate system, the changes of the structural parameters include the elongation ratios of the unit rubber material in different axial directions; Based on the elongation ratios in different axial directions and according to the functional relationship between the network chain conformation entropy and the elongation ratios in different axial directions, the changes in the elongation ratios in different axial directions are processed to obtain the network chain conformation entropy change of the rubber material.

3. The calculation method according to claim 2, characterized in that: The structural parameters include λ x , y and λ z ; The network chain conformation entropy change ΔS=m(k,N,λ x ,λ y ,λ z ); Among them, k is the Boltzmann constant, N is the number of cross-linked network chains; λ x is the elongation ratio in the x-axis direction when the unit cubic rubber specimen is deformed; λ y is the elongation ratio in the y-axis direction when the unit cubic rubber specimen is deformed; λ z It is the elongation ratio in the z-axis direction when the unit cubic rubber specimen is deformed.

4. The calculation method according to claim 1, characterized in that: The free energy change of the rubber is obtained according to the entropy change of the network chain conformation, and the corresponding relationship between the free energy change of the rubber and the entropy change of the network chain conformation is obtained based on the stress-strain, including: Based on the internal energy change ΔU of the rubber material under pure shear deformation, combined with the functional relationship between the free energy change ΔF and the entropy change ΔS of the network chain conformation, the corresponding relationship between stress and strain is obtained as σ=p(ε); Here, ε is the strain of the rubber material.

5. The calculation method according to claim 4, characterized in that: The internal energy of rubber material remains unchanged under pure shear deformation ΔU = 0; Combining the functional relationship between the free energy change ΔF and the network chain conformation entropy change ΔS, ΔF=ΔU-TΔS=TΔS, the corresponding relationship between stress and strain is obtained as σ=p(ε).

6. The calculation method according to claim 1, characterized in that: The strain energy density of the macro rubber material is obtained according to the corresponding relationship between the stress and the strain, and the peak value of the tearing energy is obtained based on the strain energy density, including: Based on the stress-strain relationship σ=p(ε), and the calculation formula of strain energy density u ε =∫σdε, and obtain the functional relationship between the strain energy density and the strain; The functional relationship between the strain energy density and the strain is brought into the macroscopic size for calculation, thereby obtaining the tearing energy peak value.

7. The calculation method according to claim 1, characterized in that: Based on the tear energy peak value, the crack growth rate is obtained using the calculation logic of the Lake-Lindley crack growth rate model, including: According to the relationship between the tear energy peak value and the strain in the tear energy peak value, combined with the calculation logic of the Lake-Lindley crack growth rate model, the tear energy peak value is processed to obtain the functional relationship between the crack growth rate r and the strain ε, r=f(ε); Here, ε is the strain of the rubber material.

8. A device for calculating the crack growth rate of a rubber material, characterized in that: The computing device comprises: A data acquisition module is used to identify the changes in structural parameters of unit rubber materials under pure shear deformation; The first data processing module is used to process the changes in the structural parameters and obtain the entropy change of the network chain conformation of the rubber material; A second data processing module is used to obtain the rubber free energy change according to the network chain conformation entropy change, and obtain the corresponding relationship between the rubber free energy change and the network chain conformation entropy change; A third data processing module is used to obtain the strain energy density of the macro rubber material according to the corresponding relationship between stress and strain, and further obtain the tear energy peak value based on the strain energy density; The fourth data processing module is used to obtain the crack growth rate based on the tear energy peak value using the calculation logic of the Lake-Lindley crack growth rate model.

9. A computer terminal, characterized in that: The computer terminal comprises a processor and a memory, wherein the memory stores a computer program, and the processor is used to execute the computer program to implement the method for calculating the crack growth rate of the rubber material according to any one of claims 1 to 7.

10. A readable storage medium, characterized in that: The computer program is stored therein, and when the computer program is run on a processor, the method for calculating the crack growth rate of a rubber material according to any one of claims 1 to 7 is executed.

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