Prediction method for high-frequency dynamic stiffness of rubber damping part

Abstract

The invention discloses a method for predicting high-frequency dynamic stiffness of a rubber damping part, which comprises the following steps of: preparing a sample of a target rubber damping part, and performing a rubber uniaxial tension and compression deformation test and a rubber dynamic mechanical test on the sample; a Mooney-Rivlin hyperelastic constitutive model and a rubber Prony viscoelastic model are subjected to fitting; in three-dimensional modeling software, a three-dimensional model of a rubber part in the rubber damping part is established, geometric cleaning is conducted, then the three-dimensional model is imported into finite element pretreatment software, and meshing is conducted on rubber; importing the grid model into finite element analysis software, and setting material attributes; setting analysis steps in finite element analysis software; setting contact, preloading, constraint and loading, and calculating static stiffness and dynamic stiffness; obtaining a dynamic-static ratio according to the ratio of the dynamic stiffness to the static stiffness; and comparing the dynamic stiffness value and the dynamic-static ratio simulated by the rubber damping part with the dynamic stiffness value and the dynamic-static ratio measured value, and correcting the material parameters until the result difference is less than 15%.

Description

Technical Field

[0001] The invention relates to the technical field of simulation test of automobile rubber shock-absorbing parts, in particular to a method for predicting high-frequency dynamic stiffness of rubber shock-absorbing parts. Background Art

[0002] With the development of the modern automobile industry, users have higher and higher requirements for automobile NVH (Noise, Vibration, Harshness). One of the keys to the development of automobile NVH performance is to control the vibration isolation of the suspension system, which is related to the performance of the suspension vibration-absorbing rubber damping parts. Rubber damping parts are vibration-isolating elements between the automobile powertrain and the frame, and are important components for attenuating automobile vibration and noise. A rubber damping part with excellent performance is conducive to improving the NVH performance of the automobile, thereby improving the riding comfort of users.

[0003] Automobile suspension mainly transmits excitation through rubber shock-absorbing parts, and makes full use of the viscoelastic properties of rubber shock-absorbing parts to achieve the purpose of vibration absorption. Therefore, it is of great significance to study the high-frequency dynamic characteristics of rubber shock-absorbing parts. The high-frequency dynamic stiffness performance of rubber shock-absorbing parts is an important factor in determining the NVH performance of the whole vehicle. It is necessary to focus on the dynamic characteristics of rubber vibration isolation parts in the high-frequency band. At the same time, the dynamic stiffness of rubber elastic parts has a strong amplitude correlation and frequency correlation. Therefore, when testing the dynamic stiffness performance of rubber elastic parts, it is necessary to test the characteristics of different amplitudes and different frequency excitation conditions; therefore, it brings high time cost, manpower cost and economic cost. Therefore, the research on the high-frequency dynamic stiffness prediction method of rubber shock-absorbing parts can effectively reduce the product design cycle and reduce the test verification cost; dynamic stiffness simulation can be used to guide, simplify and reduce dynamic stiffness tests. These have great research significance and economic value for enterprises. Summary of the invention

[0004] In view of the defects existing in the prior art, the object of the present invention is to provide a method for predicting the high frequency dynamic stiffness of a rubber shock absorbing part.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a method for predicting the high-frequency dynamic stiffness of a rubber shock-absorbing part, comprising the following steps:

[0006] Step S1. preparing a sample of a target rubber shock-absorbing part, and performing a rubber uniaxial tension and compression deformation test and a rubber dynamic mechanical test on the sample; fitting a Mooney-Rivlin hyperelastic constitutive model and a rubber Prony viscoelastic model;

[0007] Step S2. In a three-dimensional modeling software, a three-dimensional model of the rubber part of the rubber shock-absorbing component is established, and after geometric cleaning, the model is imported into a finite element pre-processing software to mesh the rubber;

[0008] Step S3. Import the mesh model into the finite element analysis software and set the material properties;

[0009] Step S4. Setting the analysis step in the finite element analysis software; setting the contact, preload, constraint and load, and calculating the static stiffness and dynamic stiffness; obtaining the dynamic-static ratio according to the ratio of the dynamic stiffness to the static stiffness;

[0010] Step S5. Compare the simulated dynamic stiffness values ​​and dynamic-to-static ratio of the rubber shock-absorbing component with the measured values ​​of the dynamic stiffness values ​​and dynamic-to-static ratio, and correct the material parameters until the result difference is less than 15%.

[0011] On the basis of the above technical solution, in step S1, the rubber uniaxial tension and compression deformation test is carried out by using the MTS material dynamic mechanical testing device, the prepared square rubber test is glued into the fixture, the rubber uniaxial tension and compression deformation test is carried out, and the Mooney-Rivlin hyperelastic constitutive model is fitted; the Mooney-Rivlin hyperelastic constitutive model is expressed as:

[0012] W=C 10 (I B -3)+C 01 (H B -3)(1)

[0013] Where, μ is the initial shear modulus of the rubber material, μ = 2(C 10 +C 01 );

[0014] The nominal principal stresses of the Mooney-Rivlin model in the three basic deformation modes are:

[0015]

[0016] Wherein, PS refers to pure shear test; λ is the principal elongation ratio of rubber; σ is the nominal principal strain of rubber;

[0017] By identifying C 10 and C 01 The parameters of the Mooney-Rivlin hyperelastic constitutive model are obtained.

[0018] On the basis of the above technical scheme, in step S1, the dynamic mechanical test of rubber includes: at room temperature, using RPA equipment, taking samples with Shore A hardness of 42, 46, 50, 63, and 67, 3 samples for each hardness, a total of 15 samples; the test temperature is 100 degrees; the strain is 7%; the typical frequency is 2 to 27 Hz, and the scanning step is 1 Hz; with the frequency change of 1 Hz as a unit, the relationship between the average strain, dynamic amplitude, sinusoidal frequency, stress amplitude, storage modulus, loss modulus, and loss factor of the rubber and the frequency change is output.

[0019] On the basis of the above technical solution, in step S1, in the finite element software Abaqus, the viscoelastic constitutive model adopts the generalized Maxwell model, and the Prony series is used to express the time-dependent characteristics of the rubber material. The expression of the shear relaxation modulus is:

[0020]

[0021] Where, G(t) is the instantaneous value of shear relaxation modulus;

[0022] G0——initial value of shear relaxation modulus;

[0023] ——dimensionless material constants;

[0024] - Relaxation time;

[0025] Divide the instantaneous value of the shear relaxation modulus by the initial value to obtain the dimensionless shear relaxation modulus:

[0026]

[0027] When identifying material parameters based on the test data of shear relaxation modulus, the test data can be normalized first, and then the least square method can be used to identify the material parameters according to formula (4). and The identification results are directly input into the finite element software Abaqus;

[0028] When using RPA equipment to obtain dynamic frequency sweep test data identification and When , the least squares method is also used, and the objective function is as follows:

[0029]

[0030] In the formula, G′(w i )、G″(w i )——Calculated storage modulus and loss modulus;

[0031] G′, G″——During the test, i Storage modulus and loss modulus measured at frequency;

[0032] w i - test frequency;

[0033] M——the number of data measured in the test;

[0034] The parameters identified according to formula (5) can be applied to the finite element software Abaqus after conversion;

[0035]

[0036] In formula (9), G ∞ is the long-term shear modulus, after conversion and It can be directly input into the Abaqus software viscoelastic material properties.

[0037] On the basis of the above technical solution, in step S2, UG is used for 3D modeling and geometry cleaning; and hypermesh is used as the finite element pre-processing software.

[0038] Based on the above technical solution, in step S3, the finite element analysis software is Abaqus; the material properties include setting density, hyperelastic properties and viscoelastic properties.

[0039] On the basis of the above technical solution, in step S4, a forced displacement is set for the rubber, and the static stiffness is calculated by taking the displacement and reaction force in the linear segment; the rubber is set to a swept frequency displacement excitation, and the dynamic stiffness is calculated according to the frequency-reaction force; and the dynamic-static ratio is obtained by dividing the dynamic stiffness value by the static stiffness value.

[0040] On the basis of the above technical solution, in step S5, correcting the material parameters mainly refers to correcting the rubber viscoelastic parameters, and selecting the Prony series fitting parameters of the shear modulus of rubber materials with different hardness to calibrate the measured values ​​so that the dynamic stiffness value and the dynamic-static ratio are close to the test values.

[0041] The beneficial effects of the present invention are:

[0042] (1) The prediction method of the present invention is fast and effective, requires almost no cost, and does not require processing, manufacturing, or testing of rubber shock-absorbing parts. It only requires the establishment of a three-dimensional model of the rubber body, which is processed in the software and submitted for calculation to simulate the high-frequency dynamic stiffness of the rubber shock-absorbing parts.

[0043] (2) The present invention enables the rubber shock-absorbing parts to be found out whether their high-frequency dynamic stiffness meets the standard during the development stage, without having to wait until the physical stage for improvement after testing. This can reduce development costs, reduce the time spent in testing steps, and reduce testing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a flow chart of the method for predicting high frequency dynamic stiffness of rubber shock absorbing parts of the present invention;

[0045] Figure 2 It is a schematic diagram of a three-dimensional model of the original model of the rubber shock-absorbing component of the present invention;

[0046] Figure 3 It is a mesh model of the rubber shock-absorbing part of the present invention after being simplified;

[0047] Figure 4 It is a rubber specimen testing tool. DETAILED DESCRIPTION

[0048] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions.

[0049] The following is a further description of the specific embodiments of the present invention in conjunction with the drawings of the specification, so that the technical solution and its beneficial effects of the present invention are clearer and more explicit. The following description of the embodiments with reference to the drawings is exemplary and intended to explain the present invention, but cannot be understood as limiting the present invention.

[0050] See also Figure 1 to Figure 4 As shown in Table 1, the embodiment of the present invention provides a method for predicting the high-frequency dynamic stiffness of a rubber shock-absorbing part:

[0051] Step 1: Prepare a sample of a rubber shock-absorbing part, and conduct rubber uniaxial tension and compression deformation (UT and UC) tests and rubber dynamic mechanical tests by MTS equipment and RPA equipment respectively; fit the Mooney-Rivlin hyperelastic constitutive model and the rubber Prony viscoelastic model;

[0052] In one embodiment of the present invention, a rubber uniaxial tension and compression deformation (UT and UC) test is performed by using an MTS material dynamic mechanical testing device, the prepared square rubber test is glued into a fixture, and the rubber uniaxial tension and compression deformation test is performed to fit the Mooney-Rivlin hyperelastic constitutive model; the Mooney-Rivlin hyperelastic constitutive model is expressed as

[0053] W=C 10 (I B -3)+C 01 (H B -3)(1)

[0054] Where, μ is the initial shear modulus of the rubber material, μ = 2(C 10 +C 01 );

[0055] The nominal principal stress of the Mooney-Rivlin model in the three basic deformation modes is:

[0056]

[0057] Where PS refers to pure shear test; λ is the principal elongation ratio of rubber; σ is the nominal principal strain of rubber.

[0058] By identifying C 10 and C 01The parameters of the Mooney-Rivlin hyperelastic constitutive model are obtained.

[0059] In one embodiment of the present invention, a dynamic mechanical test of rubber is carried out; at room temperature, RPA equipment is used to take samples with Shore A hardness of 42, 46, 50, 63, and 67, 3 samples for each hardness, a total of 15 samples; the test temperature is 100 degrees; the strain is 7%; the typical frequency is 2 to 27 Hz, and the scanning step is 1 Hz; with the frequency change of 1 Hz as the unit, the relationship between the average strain of the rubber, dynamic amplitude, sinusoidal frequency, stress amplitude, storage modulus, loss modulus, and loss factor as a function of frequency is output (the output data is a numerical value).

[0060] According to claim 1, a viscoelastic constitutive model fitting of a rubber shock-absorbing part is characterized by identifying viscoelastic parameters in the finite element software Abaqus. In Abaqus, the viscoelastic constitutive model adopts a generalized Maxwell model, and the Prony series is used to express the time-dependent characteristics of the rubber material. The expression of the shear relaxation modulus is:

[0061]

[0062] Where, G(t) is the instantaneous value of shear relaxation modulus;

[0063] G0——initial value of shear relaxation modulus;

[0064] ——dimensionless material constants;

[0065] - Relaxation time;

[0066] Divide the instantaneous value of the shear relaxation modulus by the initial value to obtain the dimensionless shear relaxation modulus:

[0067]

[0068] When identifying material parameters based on the test data of shear relaxation modulus, the test data can be normalized first, and then the least square method can be used to identify the material parameters according to formula (4). and The identification results are directly input into the finite element software Abaqus.

[0069] When using RPA equipment to obtain dynamic frequency sweep test data identification and When , the least squares method is also used, and the objective function is as follows:

[0070]

[0071] In the formula, G′(wi )、G″(w i )——Calculated storage modulus and loss modulus;

[0072] G′, G″——During the test, i Storage modulus and loss modulus measured at frequency;

[0073] w i - test frequency;

[0074] M——the number of data measured in the test;

[0075] The parameters identified according to formula (5) can be applied to the finite element software Abaqus after conversion.

[0076]

[0077] In formula (9), G ∞ is the long-term shear modulus, after conversion and It can be directly input into the Abaqus software viscoelastic material properties.

[0078] Step 2: In the 3D modeling software, create a 3D model of the rubber part of the rubber shock-absorbing part, import it into the finite element pre-processing software after geometric cleaning, and mesh the rubber.

[0079] In one embodiment of the present invention, UG is used for 3D modeling and geometry cleaning.

[0080] In one embodiment of the present invention, the finite element pre-processing software is hypermesh.

[0081] In one embodiment of the present invention, in order to ensure that the finite element calculation can accurately express the large deformation of the rubber, a high-quality hexahedral mesh is drawn in the software.

[0082] In one embodiment of the present invention, the grid size is set to about 2 mm to ensure calculation efficiency and result convergence.

[0083] In one embodiment of the present invention, the hybrid equation is checked in the mesh type setting of the rubber.

[0084] Step 3: Import the mesh model into the finite element analysis software and set the material properties.

[0085] In one embodiment of the present invention, the finite element analysis software is Abaqus. In one embodiment of the present invention, the material properties include setting density, hyperelastic properties and viscoelastic properties.

[0086] Step 4: Set the analysis step in the finite element analysis software, and make sure to check the large deformation in the Abaqus analysis step; set the contact, preload, constraint and load, and calculate the static and dynamic stiffness; obtain the dynamic-static ratio based on the ratio of dynamic stiffness to static stiffness.

[0087] Specifically, a forced displacement is set for the rubber, and the static stiffness is calculated by taking the displacement and reaction force in the linear segment; the rubber is set to a swept frequency displacement excitation, and the dynamic stiffness is calculated based on the frequency-reaction force; the dynamic-static ratio is obtained by dividing the dynamic stiffness value by the static stiffness value.

[0088] Step 5: Compare the simulated dynamic stiffness values ​​and dynamic-to-static ratio of the rubber shock-absorbing parts with the measured values ​​of dynamic stiffness values ​​and dynamic-to-static ratio, and modify the material parameters until the difference in the results is less than 15%.

[0089] Specifically, the modified material parameters mainly refer to the modified rubber viscoelastic parameters, and the shear modulus Prony series fitting parameters of rubber materials with different hardness (Shore hardness 40 / 50 / 55 / 60 / 70) are selected to calibrate the measured values, so that the dynamic stiffness value and dynamic-static ratio are close to the test values.

[0090] In summary, the present invention can obtain the dynamic stiffness curve by setting a three-dimensional model of the rubber setting through finite element analysis simulation, and can realize the prediction of dynamic stiffness in the product design stage, which has strong practical significance and economic value for enterprises.

[0091] Table 1 Static stiffness, dynamic stiffness and dynamic-static ratio data of rubber shock-absorbing parts simulation and test

[0092]

[0093] In the description of the specification, the description with reference to the terms "one embodiment", "preferably", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention, and the schematic expressions of the above terms in this specification do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0094] The present invention is not limited to the above-mentioned embodiments. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for predicting high frequency dynamic stiffness of a rubber shock absorbing part, characterized in that: The following steps are involved: Step S1. preparing a sample of a target rubber shock-absorbing part, and performing a rubber uniaxial tension and compression deformation test and a rubber dynamic mechanical test on the sample; fitting a Mooney-Rivlin hyperelastic constitutive model and a rubber Prony viscoelastic model; Step S2. In a three-dimensional modeling software, a three-dimensional model of the rubber part of the rubber shock-absorbing component is established, and after geometric cleaning, the model is imported into a finite element pre-processing software to mesh the rubber; Step S3. Import the mesh model into the finite element analysis software and set the material properties; Step S4. Setting the analysis step in the finite element analysis software; Set contact, preload, constraint and load, calculate static stiffness and dynamic stiffness; obtain dynamic-static ratio based on the ratio of dynamic stiffness to static stiffness; Step S5. Compare the simulated dynamic stiffness values ​​and dynamic-to-static ratio of the rubber shock-absorbing component with the measured values ​​of the dynamic stiffness values ​​and dynamic-to-static ratio, and correct the material parameters until the result difference is less than 15%.

2. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S1, the rubber uniaxial tension and compression deformation test is carried out by using the MTS material dynamic mechanical testing device, the prepared square rubber test is glued into the fixture, the rubber uniaxial tension and compression deformation test is carried out, and the Mooney-Rivlin hyperelastic constitutive model is fitted; the Mooney-Rivlin hyperelastic constitutive model is expressed as: W=C 10 (I B -3)+C 01 (H B -3)(1) Where, μ is the initial shear modulus of the rubber material, μ = 2(C 10 +C 01 ); The nominal principal stresses of the Mooney-Rivlin model in the three basic deformation modes are: Wherein, PS refers to pure shear test; λ is the principal elongation ratio of rubber; σ is the nominal principal strain of rubber; By identifying C 10 and C 01 The parameters of the Mooney-Rivlin hyperelastic constitutive model are obtained.

3. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S1, the dynamic mechanical test of rubber includes: at room temperature, using RPA equipment, taking samples with Shore A hardness of 42, 46, 50, 63, and 67, 3 samples for each hardness, a total of 15 samples; the test temperature is 100 degrees; the strain is 7%; the typical frequency is 2 to 27 Hz, and the scanning step is 1 Hz; with the frequency change of 1 Hz as a unit, the relationship between the average strain, dynamic amplitude, sinusoidal frequency, stress amplitude, storage modulus, loss modulus, and loss factor of the rubber and the frequency change is output.

4. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S1, in the finite element software Abaqus, the viscoelastic constitutive model adopts the generalized Maxwell model, and the Prony series is used to express the time-dependent characteristics of the rubber material. The expression of the shear relaxation modulus is: Where, G(t) is the instantaneous value of shear relaxation modulus; G0——initial value of shear relaxation modulus; ——dimensionless material constants; - Relaxation time; Divide the instantaneous value of the shear relaxation modulus by the initial value to obtain the dimensionless shear relaxation modulus: When identifying material parameters based on the test data of shear relaxation modulus, the test data can be normalized first, and then the least square method can be used to identify g according to formula (4). i p and τ i p ; Input the identification results directly into the finite element software Abaqus; When using RPA equipment to obtain dynamic frequency sweep test data to identify g i p and τ i p When , the least squares method is also used, and the objective function is as follows: In the formula, G′(w i )、G″(w i )——Calculated storage modulus and loss modulus; G′, G″——During the test, i Storage modulus and loss modulus measured at frequency; w i - test frequency; M——the number of data measured in the test; The parameters identified according to formula (5) can be applied to the finite element software Abaqus after conversion; In formula (9), G ∞ is the long-term shear modulus, after conversion and It can be directly input into the Abaqus software viscoelastic material properties.

5. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S2, UG is used for 3D modeling and geometry cleaning; hypermesh is used as the finite element pre-processing software.

6. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S3, the finite element analysis software is Abaqus; the material properties include setting density, hyperelastic properties and viscoelastic properties.

7. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S4, a forced displacement is set for the rubber, and the displacement and reaction force in the linear segment are taken to calculate the static stiffness; the rubber is set to a swept frequency displacement excitation, and the dynamic stiffness is calculated according to the frequency-reaction force; and the dynamic-static ratio is obtained by dividing the dynamic stiffness value by the static stiffness value.

8. The method for predicting high frequency dynamic stiffness of a rubber shock absorbing component according to claim 1, characterized in that: In step S5, correcting the material parameters mainly refers to correcting the rubber viscoelastic parameters, and selecting the Prony series fitting parameters of the shear modulus of rubber materials with different hardness to calibrate the measured values ​​so that the dynamic stiffness value and the dynamic-static ratio are close to the test values.

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