Multi-scale strength prediction method and system for composite material mechanical structure

Abstract

The invention relates to a method and system for predicting the multi-scale strength of a composite material mechanical structure, and the method comprises the steps: obtaining the structural parameters of a to-be-predicted composite material, calculating the mechanical properties of carbon fibers on the microscopic scale through a local homogenization theory, and obtaining the average stress of the carbon fibers; the mechanical property of the magnetic powder adhesive film on the microscopic scale is calculated by adopting a unit cell structure theory; the carbon fibers and the magnetic powder adhesive film are overlapped and fitted into a single-layer magnetic composite material, and the mechanical property of the single-layer magnetic composite material on the mesoscale is calculated through the local constitutive law; the method comprises the following steps: fitting a multi-layer wound single-layer magnetic composite material into a layer of composite magnetic material, calculating the mechanical property of the magnetic composite material on a macroscopic scale by utilizing a classical lamination theory, calculating the stress distribution of a rotor structure, and analyzing whether the strength of the composite magnetic material rotor meets the design requirement or not; the method disclosed by the invention can truly reflect the influence of the material component change on the structural strength.

Description

Technical Field

[0001] This disclosure relates to the field of composite material performance testing technology, specifically to a multi-scale strength prediction method and system for composite material mechanical structures. Background Technology

[0002] Rotor strength is a major obstacle limiting the development of high-speed permanent magnet motors (HSPMMs) to higher operating speeds. Traditional HSPMMs use sintered NdFeB for their permanent magnets, which have a tensile strength limit of 80 MPa, requiring a protective sheath for high-speed rotation. A novel composite rotor replaces sintered NdFeB with a high-strength composite magnetic material. This new composite rotor comprises a shaft, sintered permanent magnets, a magnetic power film / carbon fiber (MPF / CF) unit, and a carbon fiber sheath. The MPF / CF is formed by combining hard magnetic powder and epoxy resin to create a magnetic powder film, which is then combined with pre-impregnated carbon fiber to form the MPF / CF composite material. This composite material is then uniformly wound layer by layer around the permanent magnet to form the novel composite rotor. The MPF / CF composite material primarily bears the load through the carbon fiber layers, significantly increasing the tensile strength of the magnetic material and allowing for a substantial increase in rotor linear speed.

[0003] Accurate analysis of rotor structural strength is required during the structural design phase. Currently, the commonly used strength analysis methods are based on the thick-walled cylinder theory of elasticity or the finite element method. These methods analyze the stress state of the sheath and permanent magnet from a macroscopic perspective to ensure that there is sufficient contact pressure between the permanent magnet and the sheath under the huge centrifugal force generated by the high-speed rotation of the permanent magnet rotor, and that the tensile stress on the sheath is within a reliable strength range. However, for new composite rotor structures containing multi-layer composite magnetic materials, the mechanical strength analysis methods differ from those of traditional HSPMM rotors. The changes in the microstructure and composition of composite materials determine the macroscopic mechanical properties of the rotor structure, and the currently used macroscopic elasticity theory is difficult to reflect the actual stress state of the composite rotor. Summary of the Invention

[0004] This disclosure provides a multi-scale strength prediction method and system for composite material mechanical structures, which can solve the problem that existing mechanical strength analysis methods cannot truly reflect the influence of material composition changes on structural strength. To solve the above technical problem, this disclosure provides the following technical solution: As one aspect of this disclosure, a method for predicting the multi-scale strength of composite mechanical structures is provided. It includes the following steps: S10. Obtain the structural parameters of the composite material to be predicted, establish a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculate the mechanical properties of the carbon fiber at the microscale, and obtain the average stress of the carbon fiber; establish a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculate the mechanical properties of the magnetic powder film at the microscale. S20. The carbon fiber and magnetic powder film are stacked and fitted into a single-layer magnetic composite material. The mechanical properties of the single-layer magnetic composite material at the mesoscale are calculated using the local constitutive law. S30. Fit the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, calculate the mechanical properties of the magnetic composite material on a macroscopic scale using classical laminated theory, calculate the stress distribution of the rotor structure, and analyze whether the strength of the composite magnetic material rotor meets the design requirements.

[0005] Optionally, the mechanical properties of the carbon fiber at the microscale are expressed as follows:

[0006] in, , This represents the microscopic elastic modulus of carbon fiber. , This represents the microscopic shear modulus of carbon fiber. This represents the microscopic Poisson's ratio of carbon fiber. , , , , This refers to the micro-compliance component.

[0007] Optionally, the average stress of the carbon fiber is expressed as:

[0008] in, This represents the average stress value. V For the volume of a micro-unit, V i For the first i A finite element volume, Let be the local stress at a certain point, where k for f or m , representing the average stress of the fiber and resin, respectively. y 2. y 3 represents the local coordinate value.

[0009] Optionally, the mechanical properties of the magnetic powder film at the microscale are expressed as follows:

[0010]

[0011]

[0012]

[0013] in, The longitudinal tensile modulus of the magnetic powder film. This refers to the transverse tensile modulus of the magnetic powder film. The longitudinal Poisson's ratio of the magnetic powder film. The shear modulus of the magnetic powder film. E m μ m These are the matrix elastic modulus and Poisson's ratio, respectively. A、A 1. A 2. A 3. A 4. A 5. A 6 is the constitutive transformation constant. This refers to the volume fraction of particles within a unit cell. The matrix shear modulus. The shear modulus of the magnetic powder particles. The component of the Eshelby tensor is the particle inclusion.

[0014] Optionally, the local constitutive law is expressed as:

[0015] The superscript "me" indicates the mesoscale. ~ Let be the normal stress along the three coordinate axes. ~ Where is the elastic constant. ~ For shear stress, ~ For normal strain in the three coordinate axes, ~ This represents shear strain.

[0016] Optionally, the mechanical properties of the single-layer magnetic composite material are expressed as follows:

[0017]

[0018]

[0019]

[0020] in, , For the meso-level elastic modulus, For mesoscopic shear modulus, For the mesoscopic Poisson's ratio, , , and This is the mesoscopic flexibility component.

[0021] Optionally, the mechanical properties of the magnetic composite material on a macroscopic scale are expressed as follows:

[0022]

[0023]

[0024]

[0025] The superscript "ma" represents the macroscopic scale. , For macroscopic elastic modulus, For macroscopic shear modulus, For macroscopic Poisson ratio, , , , This is the macroscopic flexibility component.

[0026] As another aspect of this disclosure, a multi-scale strength prediction system for composite mechanical structures is provided, comprising: The microscale calculation module obtains the structural parameters of the composite material to be predicted, establishes a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculates the mechanical properties of the carbon fiber at the microscale, and obtains the average stress of the carbon fiber; and establishes a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculates the mechanical properties of the magnetic powder film at the microscale. The mesoscale calculation module fits the superposition of the carbon fiber and the magnetic powder film into a single-layer magnetic composite material, and uses the local constitutive law to calculate the mechanical properties of the single-layer magnetic composite material at the mesoscale. The macroscopic-scale calculation and mechanical property analysis module fits the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, uses classical laminated theory to calculate the mechanical properties of the magnetic composite material on a macroscopic scale, calculates the stress distribution of the rotor structure, and analyzes whether the strength of the composite magnetic material rotor meets the design requirements.

[0027] As another aspect of the present disclosure, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described method for multi-scale strength prediction of composite mechanical structures.

[0028] As another aspect of the present disclosure, a computer-readable storage medium is provided having a computer program stored thereon, characterized in that the program, when executed by a processor, implements the above-described method for predicting the multi-scale strength of composite mechanical structures.

[0029] Compared to the prior art, the beneficial effects of this disclosure are as follows: 1. This disclosure provides a numerical method applicable to the strength analysis and design of novel composite rotors. It establishes the relationship between the properties of each component of the composite material and the mechanical properties of the material from the micro, meso and macro scales, and then obtains the material-structure interaction relationship, which can truly reflect the influence of changes in material composition on structural strength.

[0030] 2. This disclosure is based on efficient and accurate multi-scale calculation of structural strength, and studies the influence of micro to macro, internal to external, and material properties on the overall rotor strength. It not only realizes the mechanical prediction of rotor strength, but also facilitates the subsequent integrated design of micro and macro structures. That is, by changing the micro materials, the macro target can be improved, which has great significance for scientific research and engineering design. Attached Figure Description

[0031] Figure 1 This is a flowchart of a multi-scale strength prediction method for composite mechanical structures in Example 1; Figure 2 This is a schematic diagram of the three scale analysis structures of the multi-scale model in Example 1; Figure 3 This is a diagram of the carbon fiber unit interface in Example 1; Figure 4 This is a simplified equivalent schematic diagram of a representative structural unit in Example 1; Figure 5 This is a stress diagram of the carbon fiber unit in Example 1; Figure 6 This is a stress diagram of the magnetic powder adhesive film unit in Example 1; Figure 7 This is a schematic diagram of the stress in the composite material of the rotor structure at the microscale in Example 1; Figure 8 This is a schematic diagram of the stress in the composite material of the rotor structure at the mesoscale in Example 1; Figure 9 This is a schematic diagram of the stress in the composite material of the rotor structure at the macroscopic scale in Example 1; Figure 10 This is a load-displacement curve obtained from the longitudinal tensile test of the composite laminate in Example 1; Figure 11 This is a schematic block diagram of a multi-scale strength prediction system for composite mechanical structures in Example 2. Detailed Implementation

[0032] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0033] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0034] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0035] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0036] It is understood that the various method embodiments mentioned above in this disclosure can be combined with each other to form combined embodiments without violating the principle and logic. Due to space limitations, this disclosure will not elaborate further.

[0037] In addition, this disclosure also provides a method and system for predicting the multi-scale strength of composite mechanical structures. The above can all be used to implement any of the multi-scale strength prediction methods for composite mechanical structures provided in this disclosure. The corresponding technical solutions and descriptions are described in the relevant section of the method and will not be repeated here.

[0038] The execution entity of a method for predicting the multi-scale strength of composite mechanical structures can be a computer or other device capable of predicting the strength of composite mechanical structures at multiple scales. For example, the method can be executed by a terminal device, server, or other processing device. The terminal device can be a user equipment (UE), mobile device, user terminal, terminal, cellular phone, cordless phone, personal digital assistant (PDA), handheld device, computing device, vehicle-mounted device, wearable device, etc. In some possible implementations, the method for predicting the strength of composite mechanical structures can be implemented by a processor calling computer-readable instructions stored in memory.

[0039] Example 1 This embodiment provides a multi-scale strength prediction method for composite material mechanical structures, such as... Figure 1 As shown, it includes the following steps: S10. Obtain the structural parameters of the composite material to be predicted, establish a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculate the mechanical properties of the carbon fiber at the microscale, and obtain the average stress of the carbon fiber; establish a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculate the mechanical properties of the magnetic powder film at the microscale. S20. The carbon fiber and magnetic powder film are stacked and fitted into a single-layer magnetic composite material. The mechanical properties of the single-layer magnetic composite material at the mesoscale are calculated using the local constitutive law. S30. Fit the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, calculate the mechanical properties of the magnetic composite material on a macroscopic scale using classical laminated theory, calculate the stress distribution of the rotor structure, and analyze whether the strength of the composite magnetic material rotor meets the design requirements.

[0040] The steps of each embodiment of this disclosure will be described in detail below.

[0041] S10. Obtain the structural parameters of the composite material to be predicted, establish a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculate the mechanical properties of the carbon fiber at the microscale, and obtain the average stress of the carbon fiber; establish a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculate the mechanical properties of the magnetic powder film at the microscale. This disclosure proposes a numerical method suitable for the strength analysis and design of novel composite rotors. From the microscopic, mesoscopic, to the macroscopic scale, it establishes the relationship between the properties of each component of the composite material and the material's mechanical properties, thereby obtaining the material-structure interaction relationship, such as... Figure 2 As shown.

[0042] In this embodiment, the microstructure of the fiber is represented by the four corner units of the periodic boundary, such as... Figure 3 As shown, the local stress distribution of the microstructure is calculated, and the relationship between displacement and stress is as follows:

[0043] in, Indicates the payload. This indicates local fluctuations caused by non-uniformity.

[0044] Meanwhile, assuming that the carbon fibers are uniformly distributed in the polymer matrix phase, and each cell obeys periodic boundary conditions:

[0045] in, u i For displacement, For strain components, t i For uniform strain boundary conditions, S This represents the boundary of a quadrilateral unit.

[0046] The average stress is obtained by integrating over the matrix domain of the micro-units. Therefore, the average stress of the carbon fiber is expressed as:

[0047] in, This represents the average stress value. V For the volume of a micro-unit, V i For the first i A finite element volume, Let be the local stress at a certain point, where k for f or m , representing the average stress of the fiber and resin, respectively. y 2. y 3 represents the local coordinate value.

[0048] Furthermore, based on the effective consistency matrix The effective engineering modulus of the composite magnetic material is derived. C The elastic modulus matrix (or stiffness matrix) can also be written as ,Right now

[0049]

[0050] The superscript "mi" represents the microscale. S is the flexibility matrix, which is the inverse of the stiffness matrix.

[0051] Optionally, the mechanical properties of the carbon fiber at the microscale are expressed as follows:

[0052] in, , This represents the microscopic elastic modulus of carbon fiber. , This represents the microscopic shear modulus of carbon fiber. This represents the microscopic Poisson's ratio of carbon fiber. , , , , This refers to the micro-compliance component.

[0053] In the microstructure, a three-dimensional finite element model of the magnetic powder film composite material was established using the unit cell structure theory, and its mechanical properties were calculated to obtain the elastic modulus at the microscale. shear modulus Poisson's ratio The value of , where the magnetic powder film is an isotropic material.

[0054] The average stress of the matrix in this unit cell structure is:

[0055] in, and These represent the disturbance stress and disturbance strain caused by the interaction between particles and the interface, respectively. L 0 represents the elastic constant tensor of the matrix material. , These represent the stress and strain of the homogeneous matrix medium, respectively.

[0056] Due to the difference in elastic properties between the magnetic powder particles and the resin matrix, the average stress of the inclusions, according to the Mori-Tanaka method, is expressed as:

[0057] in, Let be the equivalent intrinsic strain of the particle. Under the action of an external force, the average stress and average strain of the particle differ from the corresponding average values ​​in the matrix; this difference is denoted as . and .

[0058] According to Hooke's law, the mechanical properties of the magnetic powder film at the microscale are expressed as follows:

[0059]

[0060]

[0061]

[0062] in, The longitudinal tensile modulus of the magnetic powder film. This refers to the transverse tensile modulus of the magnetic powder film. The longitudinal Poisson's ratio of the magnetic powder film. The shear modulus of the magnetic powder film. E m μ m These are the matrix elastic modulus and Poisson's ratio, respectively. A、A 1. A 2. A 3. A 4. A 5. A 6 is the constitutive transformation constant. This refers to the volume fraction of particles within a unit cell. The matrix shear modulus. The shear modulus of the magnetic powder particles. The component of the Eshelby tensor is the particle inclusion.

[0063] The above is an analysis of the microstructure of magnetic powder film in composite materials.

[0064] S20. The carbon fiber and magnetic powder film are stacked and fitted into a single-layer magnetic composite material. The mechanical properties of the single-layer magnetic composite material at the mesoscale are calculated using the local constitutive law. In this embodiment, since the fiber orientation of the selected carbon fibers is consistent, the two microscale properties can be directly superimposed, and the mechanical properties of the composite material can be obtained through parallel calculation or energy method. Furthermore, using the local constitutive law, the monolayer composite magnetic material can be homogenized into anisotropic material. To simplify the calculation, a representative volumetric structure (RVE) composed of magnetic powder film and carbon fiber is extracted from the cylindrical composite structure wound with the composite rotor and homogenized into solid units, such as... Figure 4 As shown in the diagram. Here, X, Y, and Z are replaced by Cartesian coordinates 1, 2, and 3, respectively, and a, b, and h are the unit length, width, and thickness of the new simplified structure, respectively. Therefore, the single-layer magnetic composite material is simplified to a thin anisotropic plate with equivalent material properties. The local constitutive law is expressed as:

[0065] The superscript "me" indicates the mesoscale. ~ Let be the normal stress along the three coordinate axes. ~ Where is the elastic constant. ~ For shear stress, ~ For normal strain in the three coordinate axes, ~ This represents shear strain.

[0066] Based on the configuration of the RVE, a periodic boundary relationship is applied to the relevant points on the relative surface of each RVE, and calculated according to the following formula:

[0067] in, u , v , w These represent the displacements in the x, y, and z directions, respectively. W x , W y , W z This represents the distance between the original point and the image point in three directions. , , The strains are in the x, y, and z directions. , , This represents shear strain.

[0068] Similar to homogenization at the microscale, at the mesoscale, six variables are independently applied to the element model, with only one strain being non-zero and the rest fixed at zero. Through finite element analysis, the stress results of the composite material are obtained, and the simplified element is discretized into multiple elements. By integrating over the entire discretized element, the effective average stress of the structural RVE is finally calculated:

[0069] in, i , j =1,2,3, where num is the total number of units used. V k and V It is the first k The volume of a finite element and a simplified RVE, Let be the local stress at a certain point, where k for f or m , representing the average stress of the fiber and resin, respectively.

[0070] Therefore, the stiffness coefficient can be obtained from the stress / strain field described above, and the compliance matrix... and stiffness matrix Satisfying mutual relationships:

[0071]

[0072] Furthermore, the mechanical properties of the single-layer magnetic composite material are expressed as follows:

[0073]

[0074]

[0075]

[0076] in, , For the meso-level elastic modulus, For mesoscopic shear modulus, For the mesoscopic Poisson's ratio, , , and This is the mesoscopic flexibility component.

[0077] S30. Fit the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, calculate the mechanical properties of the magnetic composite material on a macroscopic scale using classical laminated theory, calculate the stress distribution of the rotor structure, and analyze whether the strength of the composite magnetic material rotor meets the design requirements.

[0078] In this embodiment, classical lamination theory is adopted at the macroscopic scale, and the multi-scale analysis process needs to consider the influence of composite material lamination effects on the structure. Based on the plane stress assumption, the constitutive relations of each orthotropic layer are as follows:

[0079] The superscript "ma" indicates a macroscopic scale. and These are the strain vector and stress vector existing in the principal coordinate system, respectively.

[0080] Stress and strain correspond to the components of the following equation, expressed using a compliance matrix:

[0081] Furthermore, the macroscopic mechanical properties of the magnetic composite material are obtained, expressed as follows:

[0082]

[0083]

[0084]

[0085] The superscript "ma" represents the macroscopic scale. , For macroscopic elastic modulus, For macroscopic shear modulus, For macroscopic Poisson ratio, , , , This is the macroscopic flexibility component.

[0086] This embodiment employs the above top-down multi-scale numerical analysis process. First, at the microscopic level, the composite material is considered as a composite material composed of carbon fibers and magnetic powder particles. The mechanical properties of transversely isotropic carbon fiber units are calculated using the local homogenization theory, while the mechanical properties of magnetic powder film units are calculated using the unit cell structure theory. The mechanical properties of the two homogenized materials are then fitted as a layer in the composite rotor structure for meso-scale analysis. Finally, the multi-layer wound magnetic composite material is fitted as a single layer, and the influence of different material proportions on the mechanical properties of the composite material at the three scales is analyzed. A finite element model of the rotor structure is established, and the stress distribution state of the rotor under different working conditions is analyzed to determine whether the structural strength meets the design requirements, thus realizing the integrated material-structure design of the rotor.

[0087] The multi-scale strength prediction method for composite mechanical structures based on this embodiment is further described through specific example 1. For instance, the selected carbon fiber is T700, the hard magnetic powder particle size is 100µm, and the matrix is ​​epoxy resin E20 material. The material properties of each component are shown in Table 1. The ratio of carbon fiber filaments to carbon fiber layers is selected as 58.80%, and the ratio of carbon fiber layers to composite magnetic materials is 54.8%. The ratio of magnetic powder particles to magnetic powder film layers is 61.16%, and the ratio of magnetic powder film layers to composite magnetic materials is 45.2%.

[0088] Table 1 Material Properties

[0089] A three-dimensional model of the carbon fiber microstructure was established, and the mechanical properties of the carbon fiber were calculated using the finite element method. The local stress distribution of the microstructure was simulated and analyzed to obtain the elastic modulus. =136.04 GPa, = =9.632GPa, shear modulus =3.037 GPa, Poisson's ratio =0.29. The microscale stress distribution is shown in [the image / description]. Figure 5 .Depend on Figure 5 It can be seen that the fiber filament bears the greatest stress in the carbon fiber unit, and the epoxy resin needs to bear some of the stress to prevent the carbon fiber from delaminating.

[0090] A Relationship Optimal Element (RVE) model of the magnetic powder adhesive film was established. A three-dimensional finite element model of the magnetic powder adhesive film composite material was established using the unit cell structure principle, and the elastic modulus of the magnetic powder adhesive film at the microscale was calculated. =8.54GPa, shear modulus =4.17 GPa, Poisson's ratio =0.27. The microscale stress distribution of the magnetic powder film is shown in [the figure]. Figure 6 . Figure 6 In the diagram, (a) represents radial stress. Figure 6 In the diagram, (b) represents the tangential stress. (From...) Figure 6 It can be seen that the magnetic powder film layer in the composite magnetic material is protected by the carbon fiber layer, and the stress is about 5.5 MPa; the epoxy resin bears a large stress in the magnetic powder film, but the overall stress distribution is relatively uniform.

[0091] A mesoscale model of the composite material was established. Carbon fiber pre-impregnated fabric and magnetic powder film were stacked in parallel, and the elastic modulus of the MPF / CF composite material was obtained using the energy method. =78.44 GPa, =8.07 GPa, shear modulus =3.06 GPa, Poisson's ratio =0.28.

[0092] To more intuitively analyze the main stress distribution of the composite material component in the novel rotor structure at three scales, and to calculate the structural strength of the composite material at these three scales, such as... Figures 7-9 As shown. Figure 7 The image shows the radial stress cloud diagram of the composite material layer in the rotor structure at the microscale. It can be seen that the main stress location of the composite material is the carbon fiber portion in each layer. This indicates that the carbon fiber effectively protects the magnetic powder film layer. The maximum radial stress is concentrated in the innermost layer at 12.263 MPa, which is much lower than the ultimate stress of the carbon fiber. The magnetic powder film layer mainly bears compressive stress. Figure 8 The images show radial and tangential stress contours of the composite magnetic material at the mesoscale. The maximum radial stress is 9.366 MPa, which is 23.6% lower than at the microscale. The overall trend of decreasing radial stress along the radius is the same as that of the microstructure. Furthermore, each layer of the composite material is under tensile stress, but it cannot be determined whether the tensile stress is part of the magnetic powder film. Figure 9 At the macroscopic scale, the radial stress cloud diagram of the composite material shows a maximum radial stress of 6.025 MPa, which represents a decrease of 50.8% and 33.8% respectively compared to the maximum radial stress at the microscopic scale. Furthermore, the maximum radial stress value only indicates that it covers the multi-layer composite structure, making it impossible to predict its specific location. Meanwhile, the maximum radial stress at the microscopic scale is concentrated only in the carbon fiber portion of the first layer.

[0093] The prediction method in this embodiment maintains the stress location with minimal variation across three scales. While a more detailed and accurate analysis is possible at the microscale, the precise location of the rotor's maximum stress cannot be distinguished at the mesoscale or macroscale. Furthermore, as the observation scale shifts from micro to macro, the maximum radial stress of the composite material decreases, and the internal material of the structure becomes more idealized, indicating that traditional macroscopic calculation methods are not precise enough.

[0094] Tensile tests were conducted on the composite material according to ISO 527-5. The failure mode of the composite material was explosive, with simultaneous matrix rupture, similar to the failure mode of traditional carbon fiber composites.

[0095] Figure 10 This is the load-displacement curve obtained from a longitudinal tensile test of the composite laminate. The carbon fiber was completely torn, and the load was between 24-25 kN. The general trend of the load-displacement curve is that the tensile force increases with the increase of displacement, and the overall trend is approximately linear until the specimen is completely destroyed, the magnetic composite material fractures, and the material fails.

[0096] Based on the displacement-load tensile test, the mechanical tensile strength of the composite material was calculated to be 1452 MPa, which is much greater than the 80 MPa of the sintered permanent magnet. Table 2 compares the tensile test results with the calculation method in this embodiment.

[0097] Table 2 Comparison of Simulation Calculation Methods and Tensile Test Values

[0098] According to ISO 527-5, the test results of the samples were processed. The test value of the elastic modulus was 83.78 GPa, and the test value of Poisson's ratio was 0.276, as shown in Table 2. The comparison error between the average value of the five samples and the macroscopic mechanical parameters was approximately 1.9%, and the average error of Poisson's ratio was 5%, verifying the accuracy of the model.

[0099] Example 2 As another aspect of the embodiments of this disclosure, a multi-scale strength prediction system 100 for composite material mechanical structures is also provided, such as... Figure 11 As shown, it includes the following steps: Microscale calculation module 1 obtains the structural parameters of the composite material to be predicted, establishes a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculates the mechanical properties of the carbon fiber at the microscale, and obtains the average stress of the carbon fiber; establishes a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculates the mechanical properties of the magnetic powder film at the microscale. Mesoscale calculation module 2 fits the superposition of carbon fiber and magnetic powder film into a single-layer magnetic composite material, and calculates the mechanical properties of the single-layer magnetic composite material at the mesoscale using the local constitutive law. Module 3, Macroscale Calculation and Mechanical Performance Analysis, fits the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, calculates the mechanical properties of the magnetic composite material on a macroscale using classical laminated theory, calculates the stress distribution of the rotor structure, and analyzes whether the strength of the composite magnetic material rotor meets the design requirements.

[0100] The various modules of the embodiments of this disclosure will be described in detail below.

[0101] Microscale calculation module 1 obtains the structural parameters of the composite material to be predicted, establishes a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculates the mechanical properties of the carbon fiber at the microscale, and obtains the average stress of the carbon fiber; establishes a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculates the mechanical properties of the magnetic powder film at the microscale. This disclosure proposes a numerical method suitable for strength analysis and design of novel composite rotors. It establishes the relationship between the properties of each component of the composite material and the mechanical properties of the material from the micro, meso and macro scales, and then obtains the material-structure interaction relationship.

[0102] In this embodiment, the microstructure of the fiber is represented by the four corner elements of the periodic boundary. The local stress distribution of the microstructure is calculated, and the relationship between displacement and stress is as follows:

[0103] in, Indicates the payload. This indicates local fluctuations caused by non-uniformity.

[0104] Meanwhile, assuming that the carbon fibers are uniformly distributed in the polymer matrix phase, and each cell obeys periodic boundary conditions:

[0105] in, u i For displacement, For strain components, t i For uniform strain boundary conditions, S This represents the boundary of a quadrilateral unit.

[0106] The average stress is obtained by integrating over the matrix domain of the micro-units. Therefore, the average stress of the carbon fiber is expressed as:

[0107] in, This represents the average stress value. V For the volume of a micro-unit, V i For the firsti A finite element volume, Let be the local stress at a certain point, where k for f or m , representing the average stress of the fiber and resin, respectively. y 2. y 3 represents the local coordinate value.

[0108] Furthermore, based on the effective consistency matrix The effective engineering modulus of the composite magnetic material is derived. C The elastic modulus matrix (or stiffness matrix) can also be written as ,Right now

[0109]

[0110] The superscript "mi" represents the microscale. S is the flexibility matrix, which is the inverse of the stiffness matrix.

[0111] Optionally, the mechanical properties of the carbon fiber at the microscale are expressed as follows:

[0112] in, , This represents the microscopic elastic modulus of carbon fiber. , This represents the microscopic shear modulus of carbon fiber. This represents the microscopic Poisson's ratio of carbon fiber. , , , , This refers to the micro-compliance component.

[0113] In the microstructure, a three-dimensional finite element model of the magnetic powder film composite material was established using the unit cell structure theory, and its mechanical properties were calculated to obtain the elastic modulus at the microscale. shear modulus Poisson's ratio The value of , where the magnetic powder film is an isotropic material.

[0114] The average stress of the matrix in this unit cell structure is:

[0115] in, and These represent the disturbance stress and disturbance strain caused by the interaction between particles and the interface, respectively. L 0 represents the elastic constant tensor of the matrix material. , These represent the stress and strain of the homogeneous matrix medium, respectively.

[0116] Due to the difference in elastic properties between the magnetic powder particles and the resin matrix, the average stress of the inclusions, according to the Mori-Tanaka method, is expressed as:

[0117] in, Let be the equivalent intrinsic strain of the particle. Under the action of an external force, the average stress and average strain of the particle differ from the corresponding average values ​​in the matrix; this difference is denoted as . and .

[0118] According to Hooke's law, the mechanical properties of the magnetic powder film at the microscale are expressed as follows:

[0119]

[0120]

[0121]

[0122] in, The longitudinal tensile modulus of the magnetic powder film. This refers to the transverse tensile modulus of the magnetic powder film. The longitudinal Poisson's ratio of the magnetic powder film. The shear modulus of the magnetic powder film. E m μ m These are the matrix elastic modulus and Poisson's ratio, respectively. A、A 1. A 2. A 3. A 4. A 5. A 6 is the constitutive transformation constant. This refers to the volume fraction of particles within a unit cell. The matrix shear modulus. The shear modulus of the magnetic powder particles. The component of the Eshelby tensor is the particle inclusion.

[0123] The above is an analysis of the microstructure of magnetic powder film in composite materials.

[0124] Mesoscale calculation module 2 fits the superposition of carbon fiber and magnetic powder film into a single-layer magnetic composite material, and calculates the mechanical properties of the single-layer magnetic composite material at the mesoscale using the local constitutive law. In this embodiment, since the fiber orientation of the selected carbon fibers is consistent, the two microscale properties can be directly superimposed, and the mechanical properties of the composite material can be obtained through parallel calculation or energy method. Furthermore, using the local constitutive law, the monolayer composite magnetic material can be homogenized into anisotropic material. To simplify the calculation, a representative volumetric structure (RVE) composed of magnetic powder film and carbon fiber is extracted from the cylindrical composite structure wound with the composite rotor and homogenized into solid units. Here, X, Y, and Z are replaced by Cartesian coordinates of 1, 2, and 3, respectively, and a, b, and h are the unit length, width, and thickness of the new simplified structure, respectively. Therefore, the monolayer magnetic composite material is simplified into a thin anisotropic plate with equivalent material properties. The local constitutive law is expressed as:

[0125] The superscript "me" indicates the mesoscale. ~ Let be the normal stress along the three coordinate axes. ~ Where is the elastic constant. ~ For shear stress, ~ For normal strain in the three coordinate axes, ~ This represents shear strain.

[0126] Based on the configuration of the RVE, a periodic boundary relationship is applied to the relevant points on the relative surface of each RVE, and calculated according to the following formula:

[0127] in, u , v , w These represent the displacements in the x, y, and z directions, respectively. W x , W y , W z This represents the distance between the original point and the image point in three directions. , , The strains are in the x, y, and z directions. , , This represents shear strain.

[0128] Similar to homogenization at the microscale, at the mesoscale, six variables are independently applied to the element model, with only one strain being non-zero and the rest fixed at zero. Through finite element analysis, the stress results of the composite material are obtained, and the simplified element is discretized into multiple elements. By integrating over the entire discretized element, the effective average stress of the structural RVE is finally calculated:

[0129] in, i , j =1,2,3, where num is the total number of units used. V k and V It is the first k The volume of a finite element and a simplified RVE, Let be the local stress at a certain point, where k for f or m , representing the average stress of the fiber and resin, respectively.

[0130] Therefore, the stiffness coefficient can be obtained from the stress / strain field described above, and the compliance matrix... and stiffness matrix Satisfying mutual relationships:

[0131]

[0132] Furthermore, the mechanical properties of the single-layer magnetic composite material are expressed as follows:

[0133]

[0134]

[0135]

[0136] in, , For the meso-level elastic modulus, For mesoscopic shear modulus, For the mesoscopic Poisson's ratio, , , and This is the mesoscopic flexibility component.

[0137] Module 3, Macroscale Calculation and Mechanical Performance Analysis, fits the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, calculates the mechanical properties of the magnetic composite material on a macroscale using classical laminated theory, calculates the stress distribution of the rotor structure, and analyzes whether the strength of the composite magnetic material rotor meets the design requirements.

[0138] In this embodiment, classical lamination theory is adopted at the macroscopic scale, and the multi-scale analysis process needs to consider the influence of composite material lamination effects on the structure. Based on the plane stress assumption, the constitutive relations of each orthotropic layer are as follows:

[0139] The superscript "ma" indicates a macroscopic scale. and These are the strain vector and stress vector existing in the principal coordinate system, respectively.

[0140] Stress and strain correspond to the components of the following equation, expressed using a compliance matrix:

[0141] Furthermore, the macroscopic mechanical properties of the magnetic composite material are obtained, expressed as follows:

[0142]

[0143]

[0144]

[0145] The superscript "ma" represents the macroscopic scale. , For macroscopic elastic modulus, For macroscopic shear modulus, For macroscopic Poisson ratio, , , , This is the macroscopic flexibility component.

[0146] This embodiment employs the above top-down multi-scale numerical analysis process. First, at the microscopic level, the composite material is considered as a composite material composed of carbon fibers and magnetic powder particles. The mechanical properties of transversely isotropic carbon fiber units are calculated using the local homogenization theory, while the mechanical properties of magnetic powder film units are calculated using the unit cell structure theory. The mechanical properties of the two homogenized materials are then fitted as a layer in the composite rotor structure for meso-scale analysis. Finally, the multi-layer wound magnetic composite material is fitted as a single layer, and the influence of different material proportions on the mechanical properties of the composite material at the three scales is analyzed. A finite element model of the rotor structure is established, and the stress distribution state of the rotor under different working conditions is analyzed to determine whether the structural strength meets the design requirements, thus realizing the integrated material-structure design of the rotor.

[0147] Based on the description of the above embodiments, it can be seen that the embodiments of this disclosure can achieve the following technical effects: (1) This disclosure is applicable to the numerical method for strength analysis and design of novel composite rotors. It establishes the relationship between the properties of each component of the composite material and the mechanical properties of the material from the micro, meso and macro scales, and then obtains the material-structure interaction relationship, which can truly reflect the influence of material composition changes on structural strength.

[0148] (2) Based on the efficient and accurate calculation of the structure strength at multiple scales, this disclosure studies the influence of micro to macro, internal to external, and material properties on the overall rotor strength. It not only realizes the mechanical prediction of rotor strength, but also facilitates the subsequent integrated design of micro and macro structures. That is, by changing the micro materials, the macro target can be improved, which is of great significance to scientific research and engineering design.

[0149] Example 3 This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the multi-scale strength prediction method for composite mechanical structures in Embodiment 1.

[0150] Embodiment 3 of this disclosure is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this disclosure.

[0151] Electronic devices can take the form of general-purpose computing devices, such as server devices. Components of an electronic device may include, but are not limited to: at least one processor, at least one memory, and buses connecting different system components (including memory and processor).

[0152] The bus includes a data bus, an address bus, and a control bus.

[0153] The memory may include volatile memory, such as random access memory (RAM) and / or cache memory, and may further include read-only memory (ROM).

[0154] The memory may also include program tools having a set (at least one) of program modules, including but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0155] The processor performs various functional applications and data processing by running computer programs stored in memory.

[0156] Electronic devices can also communicate with one or more external devices (such as keyboards, pointing devices, etc.). This communication can be achieved through input / output (I / O) interfaces. Furthermore, electronic devices can communicate with one or more networks (such as local area networks (LANs), wide area networks (WANs), and / or public networks, such as the Internet) via network adapters. The network adapter communicates with other modules of the electronic device via a bus. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with the electronic device, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, and data backup storage systems.

[0157] It should be noted that although several units / modules or sub-units / modules of the electronic device have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to the embodiments of this application, the features and functions of two or more units / modules described above can be embodied in one unit / module. Conversely, the features and functions of one unit / module described above can be further divided and embodied by multiple units / modules.

[0158] Example 4 This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the multi-scale strength prediction method for composite mechanical structures in Embodiment 1.

[0159] The readable storage medium may be more specifically adopted, including but not limited to: portable disk, hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0160] In a possible implementation, this disclosure can also be implemented as a program product comprising program code that, when the program product is run on a terminal device, causes the terminal device to perform the steps of implementing the multi-scale strength prediction method for composite mechanical structures described in Embodiment 1.

[0161] The program code for executing this disclosure can be written in any combination of one or more programming languages, and the program code can be executed entirely on a user device, partially on a user device, as a stand-alone software package, partially on a user device and partially on a remote device, or entirely on a remote device.

[0162] Although embodiments of the present disclosure have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-scale strength prediction method for composite mechanical structures, characterized in that, Includes the following steps: The structural parameters of the composite material to be predicted are obtained. A three-dimensional model of the carbon fiber microstructure is established using the local homogenization theory. The mechanical properties of the carbon fiber at the microscale are calculated, and the average stress of the carbon fiber is obtained. A three-dimensional finite element model of the magnetic powder film composite material is established using the unit cell structure theory, and the mechanical properties of the magnetic powder film at the microscale are calculated. The carbon fiber and magnetic powder film were superimposed and fitted to form a single-layer magnetic composite material. The mechanical properties of the single-layer magnetic composite material at the mesoscale were calculated using the local constitutive law. Multilayer wound single-layer magnetic composite material is fitted into a single-layer composite magnetic material. The mechanical properties of the magnetic composite material on a macroscopic scale are calculated using classical laminated theory. The stress distribution of the rotor structure is calculated, and it is analyzed whether the strength of the composite magnetic material rotor meets the design requirements.

2. The multi-scale strength prediction method for composite mechanical structures as described in claim 1, characterized in that, The mechanical properties of the carbon fiber at the microscale are expressed as follows: in, , This represents the microscopic elastic modulus of carbon fiber. , This represents the microscopic shear modulus of carbon fiber. This represents the Poisson's ratio at the microscopic level of carbon fiber. , , , , This refers to the micro-compliance component.

3. The multi-scale strength prediction method for composite mechanical structures as described in claim 2, characterized in that, The average stress of the carbon fiber is expressed as: in, This represents the average stress value. V For the volume of a micro-unit, V i For the first i A finite element volume, Let be the local stress at a certain point, where k for f or m , representing the average stress of the fiber and resin, respectively. y 2. y 3 represents the local coordinate value.

4. The multi-scale strength prediction method for composite mechanical structures as described in claim 1, characterized in that, The mechanical properties of the magnetic powder film at the microscale are expressed as follows: in, The longitudinal tensile modulus of the magnetic powder film. The lateral tensile modulus of the magnetic powder film. The longitudinal Poisson's ratio of the magnetic powder film. The shear modulus of the magnetic powder film. E m μ m These are the matrix elastic modulus and Poisson's ratio, respectively. A、A 1. A 2. A 3. A 4. A 5. A 6 is the constitutive transformation constant. This refers to the volume fraction of particles within a unit cell. The matrix shear modulus. The shear modulus of the magnetic powder particles. The component of the Eshelby tensor is the particle inclusion.

5. The multi-scale strength prediction method for composite mechanical structures as described in claim 1, characterized in that, The local constitutive law is expressed as: The superscript "me" indicates the mesoscale. ~ Let be the normal stress along the three coordinate axes. ~ Where is the elastic constant. ~ For shear stress, ~ For normal strain in the three coordinate axes, ~ This represents shear strain.

6. The multi-scale strength prediction method for composite mechanical structures as described in claim 1, characterized in that, The mechanical properties of the single-layer magnetic composite material are expressed as follows: in, , For the meso-level elastic modulus, For mesoscopic shear modulus, For the mesoscopic Poisson's ratio, , , and This is the mesoscopic flexibility component.

7. The multi-scale strength prediction method for composite mechanical structures as described in claim 6, characterized in that, The mechanical properties of the magnetic composite material on a macroscopic scale are expressed as follows: The superscript "ma" represents the macroscopic scale. , For macroscopic elastic modulus, For macroscopic shear modulus, For macroscopic Poisson ratio, , , , This is the macroscopic flexibility component.

8. A multi-scale strength prediction system for composite material mechanical structures, characterized in that, include: The microscale calculation module obtains the structural parameters of the composite material to be predicted, establishes a three-dimensional model of the carbon fiber microstructure using the local homogenization theory, calculates the mechanical properties of the carbon fiber at the microscale, and obtains the average stress of the carbon fiber; and establishes a three-dimensional finite element model of the magnetic powder film composite material using the unit cell structure theory, and calculates the mechanical properties of the magnetic powder film at the microscale. The mesoscale calculation module fits the superposition of the carbon fiber and the magnetic powder film into a single-layer magnetic composite material, and uses the local constitutive law to calculate the mechanical properties of the single-layer magnetic composite material at the mesoscale. The macroscopic-scale calculation and mechanical property analysis module fits the multi-layer wound single-layer magnetic composite material into a single-layer composite magnetic material, uses classical laminated theory to calculate the mechanical properties of the magnetic composite material on a macroscopic scale, calculates the stress distribution of the rotor structure, and analyzes whether the strength of the composite magnetic material rotor meets the design requirements.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the multi-scale strength prediction method for composite mechanical structures according to any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the multi-scale strength prediction method for composite mechanical structures according to any one of claims 1 to 7.

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