Composite layer joint part modeling method, system, equipment and medium
Patent Information
- Application Number
- CN202511800229.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-03-03
AI Technical Summary
Existing methods cannot achieve efficient joint modeling when dealing with multiple series joints, resulting in a cumbersome modeling process and high computational costs.
The virtual material method is adopted, which treats the contact surface of each joint as an equivalent virtual material, and multiple joints and virtual materials as an equivalent composite layer joint. The model is then constructed by determining the fractal parameters and mechanical parameters.
It effectively reduced the modeling difficulty, improved simulation efficiency, and enhanced the accuracy and efficiency of modeling multiple series connections.
Smart Images
Figure CN121598702A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of mechanical engineering technology, and in particular to a method, system, device and medium for modeling composite layer joints. Background Technology
[0002] In mechanical joints, the characteristics of each contact surface determine the complexity of the structure, thus affecting the overall mechanical and dynamic properties of the model. Therefore, accurately describing the contact characteristics of the joint surfaces is a prerequisite for dynamic modeling and analysis of joints. While traditional joint modeling methods can predict the performance of joints to some extent, the modeling process often requires calculating a large number of theoretical parameters. When dealing with composite layer structures composed of multiple joints, the difficulty of solving for their contact characteristics usually increases exponentially, further exacerbating the problems of cumbersome joint modeling processes and high computational costs. Therefore, establishing an efficient and accurate standardized modeling process for multiple joints is gradually becoming a key technology for improving the simulation efficiency of joints in complex electromechanical systems.
[0003] Existing methods for modeling joints mainly fall into two categories: the spring-damped method and the virtual material method. The spring-damped method is a traditional approach for establishing dynamic models of joints in engineering practice. This method treats the contact interface as a set of springs and damping elements, simulating the mechanical response of the joint by setting its stiffness and damping coefficients. The core idea is to assume that the normal and tangential contact mechanical behavior of the joint can be described by linear or nonlinear mechanical elements, typically requiring fitting of parameters using experimental data or empirical formulas. While simple to implement, this method has significant limitations in engineering applications: First, it is highly sensitive to material type, processing conditions, and surface roughness, resulting in a lack of universality for the same parameters under different working conditions. This is fundamentally because the spring-damped method cannot accurately capture the complex nonlinear energy dissipation mechanisms in microscopic contact interfaces. Second, when multiple joints are connected in series, each interface parameter needs to be set and calibrated individually, leading to cumbersome model building, massive data volume, and easy accumulation of errors. This is because the method fails to construct a unified equivalent model structure for system-level structures. Therefore, although the spring-damped method still has reference value in single-interface analysis, it exhibits fundamental limitations when facing the modeling needs of multi-layered composite joints.
[0004] The virtual material method is a relatively advanced modeling approach for joints. Its basic idea is to treat the joint as a virtual material with specific mechanical properties, simulating actual contact behavior by constructing equivalent constitutive relations. Compared to the spring-damped method, the virtual material method has advantages such as a clear physical basis and strong scalability, making it particularly suitable for simulating microscopic contact behavior between rough surfaces. However, its main drawback is that current research focuses primarily on virtual joints in single-layer structures, and a modeling theory for composite layer structures composed of multiple series joints has not yet been developed. This means that when dealing with multi-joint systems commonly encountered in engineering, separate modeling is still required, preventing unified modeling and parameter merging, thus reducing its application efficiency in complex engineering structures.
[0005] In summary, existing methods cannot achieve efficient joint modeling when dealing with multiple series joints in actual engineering projects. Summary of the Invention
[0006] The purpose of this invention is to provide a method, system, device and medium for modeling composite layer joints, which can solve the problem that existing methods cannot achieve efficient joint modeling when faced with multiple series joints in actual engineering.
[0007] To address the aforementioned technical problems, embodiments of the present invention provide a method for modeling composite layer joints, comprising the following steps: For N series joints in a mechanical structure, obtain the surface morphology data of the contact surface of each joint; where N is greater than or equal to 1. Based on the surface morphology data, determine the fractal parameters of the contact surface of each joint; Based on the virtual material method, each contact surface of each joint is equivalent to a virtual material, and all joints and all virtual materials are equivalent to a composite layer joint; wherein, the composite layer joint consists of N joints and N+1 virtual materials; The mechanical parameters of the composite layer joint are determined based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint. The composite layer joint is modeled based on the mechanical parameters of the composite layer joint.
[0008] Furthermore, the fractal parameters include fractal dimension and fractal roughness.
[0009] Further, determining the fractal parameters of the contact surface of each joint based on surface morphology data includes: Based on the surface morphology data, Fourier transforms are performed on the autocorrelation functions corresponding to the following WM fractal functions: ; In the formula,L For rough surface sampling length, z ( x ) represents the surface profile height. This is the distance delay coefficient. D For fractal dimension, G For fractal roughness, γ For scale parameters, n For frequency coefficients, The spatial frequency coefficient corresponding to the lowest cutoff frequency; The power spectral density function of the WM fractal function is obtained as follows: ; In the formula, ω The frequency of the power spectral density function j The imaginary unit; Logarithmic transformation of the power spectral density function of the WM fractal function yields: ; Using the obtained formula as a linear expression in logarithmic coordinates, we can obtain the slope and intercept of the linear expression: ; ; In the formula, k The slope b The intercept; Substituting the slope and intercept into the formula obtained using logarithmic transformation, we get: ; The fractal dimension and fractal roughness are obtained as follows: ; ; In the formula, D For fractal dimension, G This refers to fractal roughness.
[0010] Furthermore, the mechanical parameters include the elastic modulus and Poisson's ratio.
[0011] Furthermore, when N is 1, the elastic modulus of the composite layer joint is determined through the following steps: Obtain the area distribution function for the case where a rough surface is in contact with a plane: ; In the formula, This represents the theoretical contact area of the micro-contact point. To maximize the cross-sectional contact area, For the domain expansion coefficient; When subjected to normal loads at micro-contact points, the normal loads of individual elastic and plastic micro-contact points in each joint are as follows: ; ; In the formula, This is the equivalent elastic modulus of the contact surface of the corresponding joint. , H The hardness of soft materials, σ The yield strength of soft materials; By summing all the peaks and troughs of the surface topography data and making them dimensionless, the dimensionless normal load at the composite layer interface is obtained as follows: ; In the formula, , , , , A The apparent contact area, This represents the actual contact area of the fractal region. and These are the critical maximum cross-sectional contact area and the maximum cross-sectional contact area during the elastoplastic transition, respectively. and These are the actual critical area for the elastoplastic transition and the actual maximum elastic micro-contact area, respectively. , , ; Obtain the normal contact stiffness of a single microprotrusion in contact with a plane. k nV : ; In the formula, R eq The equivalent radius of curvature of the micro-contact point. δ For local interference quantities, The equivalent elastic modulus of the virtual layer; By summing all the peaks and troughs of the surface topography data, the normal stiffness of the virtual material is obtained as follows: ; Normal stiffness of composite layer joint K n With the normal stiffness of virtual materials K nv Normal stiffness of the joint K nR The relationship between them is: ; In the formula, KnV1 and K nv2 These are the normal stiffnesses of the two virtual materials, respectively. Substituting the normal stiffness of the virtual material into the relationship between the normal stiffness of the composite layer joint and the normal stiffness of the virtual material and the joint, the normal stiffness of the composite layer joint is obtained as follows: ; The overall normal strain energy generated by the normal stiffness of the composite layer joint is: ; In the formula, P For external loads; When converted to a virtual material, the overall normal strain energy of the unit is: ; In the formula, σ n σ is the mean normal stress of the virtual material. n = P / A , h The thickness of the composite layer joint, E The elastic modulus of the composite layer joint; ; In the formula, W 1= W 2.
[0012] The Poisson's ratio of the composite layer joint is determined by the following formula: Obtain the tangential contact stiffness of a single microprotrusion in contact with a plane: ; In the formula, Let be the equivalent shear modulus of the two contacting rough surfaces. f The static friction coefficient of the contact surface is . β The coefficient of dynamic friction of the contact surface; By summing all the peaks and troughs of the surface topography data, the tangential stiffness of the virtual material is obtained as follows: ; Tangential stiffness of composite layer joint K t Tangential stiffness of virtual materials K tv Tangential stiffness of the joint K tR The relationship between them is: ; In the formula, K tV1and K tv2 These are the tangential stiffnesses of the two virtual materials, respectively. Substituting the tangential stiffness of the virtual material into the relationship between the tangential stiffness of the composite layer joint and the tangential stiffness of the virtual material and the joint, the tangential stiffness of the composite layer joint is obtained as follows: ; When the virtual material is isotropic, the Poisson's ratio at the composite layer interface is: .
[0013] Embodiments of the present invention also provide a composite layer joint modeling system, comprising: The topography data acquisition module is used to acquire the surface topography data of the contact surface of each of N series-connected joints in a mechanical structure; where N is greater than or equal to 1. The fractal parameter determination module is used to determine the fractal parameters of the contact surface of each joint based on the surface morphology data. The joint equivalent module is used to, based on the virtual material method, equate each contact surface of each joint to a virtual material, and equate all joints and all virtual materials to a composite layer joint; wherein, the composite layer joint consists of N joints and N+1 virtual materials; The mechanical parameter determination module is used to determine the mechanical parameters of the composite layer joint based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint. The joint modeling module is used to model the joint of the composite layer based on the mechanical parameters of the joint.
[0014] Embodiments of the present invention also provide a computer device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the above-described composite layer junction modeling method.
[0015] Embodiments of the present invention also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described composite layer junction modeling method.
[0016] The composite layer bonding modeling method provided by this invention has at least the following beneficial effects: For N series-connected joints in a mechanical structure, this approach first uses the virtual material method to represent each contact surface of each joint as an equivalent virtual material. Then, multiple series-connected joints and their corresponding virtual materials are represented as a single composite layer joint model. Next, based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint, the mechanical parameters of the composite layer joint are determined, leading to its modeling. This method, by constructing composite layer joints, avoids the tedious steps of analyzing each joint individually in traditional modeling, effectively reducing modeling difficulty and improving simulation efficiency. Attached Figure Description
[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:
[0018] Figure 1 A flowchart illustrating a composite layer junction modeling method provided by the present invention; Figure 2 A schematic diagram of a joint model provided by the present invention; Figure 3 A schematic diagram of a standardized process for modeling composite layer joints provided by the present invention; Figure 4 A schematic diagram of a composite layer bonding portion provided by the present invention; Figure 5 A schematic diagram of surface contour features at different scales provided by the present invention; Figure 6 A schematic diagram of the power spectral density function in a double logarithmic coordinate system provided by the present invention; Figure 7 A schematic diagram illustrating the theoretical solution calculation process for a composite layer joint provided by the present invention; Figure 8 A schematic diagram of a slider surface profile curve provided by the present invention; Figure 9 A schematic diagram of a logarithmic power spectral density plot and a fitting curve provided by the present invention; Figure 10 A schematic diagram of a lifting column for a lifting table with a composite layer joint provided by the present invention; Figure 11 A schematic diagram of a simulation modeling method for a lifting column provided by the present invention; Figure 12 A schematic diagram of a modal test node for a lifting table lifting column provided by the present invention; Figure 13A schematic diagram of a modal experimental frequency response curve provided by the present invention; Figure 14 This is a schematic diagram comparing the theoretical and experimental vibration modes of the lifting column of a height-adjustable table, provided by the present invention. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0020] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0021] One embodiment of the present invention relates to a method for modeling composite layer joints. The specific process of the composite layer joint modeling method in this embodiment can be as follows: Figure 1 As shown, it includes: Step 101: For N series-connected joints in the mechanical structure, obtain the surface morphology data of the contact surface of each joint; where N is greater than or equal to 1.
[0022] Step 102: Determine the fractal parameters of the contact surface of each joint based on the surface morphology data.
[0023] Step 103: Based on the virtual material method, each contact surface of each joint is equivalent to a virtual material, and all joints and all virtual materials are equivalent to a composite layer joint; wherein, the composite layer joint is composed of N joints and N+1 virtual materials.
[0024] Step 104: Determine the mechanical parameters of the composite layer joint based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint.
[0025] Step 105: Model the composite layer joint based on the mechanical parameters of the composite layer joint.
[0026] The following is a detailed description of the implementation details of the composite layer joint modeling method in this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.
[0027] In dealing with such Figure 2In linear problems involving joints, a commonly used method is the virtual material method. This method involves adding a virtual medium between substructures and adjusting the properties of the virtual material to approximate the dynamic characteristics of the joint, thus simulating its dynamic mechanical performance under different conditions. Specifically, the virtual material method can derive equivalent elastic modulus and Poisson's ratio based on the fractal characteristics of rough surfaces, actual material properties, and contact mechanics theory. These equivalent material properties are then embedded into the finite element model as an equivalent virtual layer, enabling continuous modeling of the joint.
[0028] Therefore, by introducing a virtual material model, the contact surface of the original layer (i.e., the joint) can be equivalent to a virtual material containing physical and geometric parameters. By analyzing the stress between the parts on both sides and the original layer, as well as the physical properties of the contact surface, corresponding mechanical performance parameters can be assigned to the virtual layers (i.e., virtual materials) on both sides. Subsequently, by connecting the stiffness of the virtual layer and the slider layer in series, the characteristics of these layers are equivalent to a composite layer, thereby achieving effective prediction of the dynamic performance of the entire structure.
[0029] like Figure 3 As shown, the original layer, the equivalent virtual material, and the parts on both sides together constitute the composite layer joint (taking one joint as an example; multiple joints connected in series are similar). This structure can simplify the handling of joints made of various materials and improve simulation efficiency by quickly adjusting structural parameters. Its mechanical performance parameters can be calculated from the equivalent model of the joint.
[0030] Based on this, this embodiment provides a method such as Figure 4 The standardized process for modeling composite layer joints shown mainly includes three key stages: preparation, theoretical calculation, and modeling and verification. In the preparation phase, before conducting finite element modeling of the composite layer interface, the primary task is to clarify the application of the composite layer. This aims to provide necessary information and data for subsequent modeling work. This step includes a comprehensive consideration of the dimensions, shape, material properties, and connection methods of each component. For any complex structure, the composite layer interface typically exists in the region where multiple components connect. Because these areas bear significant loads during actual use, their mechanical properties have a decisive impact on the simulation accuracy of the overall structure.
[0031] After determining the application of the composite layer, fractal parameter identification of the contact surface geometry is required. This involves acquiring surface topography data of the contact surfaces between the original layer and the corresponding two parts, and determining the fractal parameters of each contact surface of the original layer based on this data. The fractal parameters include fractal dimension and fractal roughness. According to the relevant definition of WM fractal functions, fractal parameters can be used to construct... Figure 5As shown, the microscopic contact morphology of any rough surface is illustrated. Therefore, in the preparation stage, a surface profilometer is needed to obtain two-dimensional profile data of the original layer contact surface and extract surface roughness features containing micro-protrusion distribution.
[0032] In practical implementation, due to the complex microscopic morphology of the original layer contact surface, traditional modeling methods struggle to accurately characterize its nonlinear contact properties. Therefore, it is necessary to obtain the surface morphology of the original layer experimentally, and then use the PSD method to identify the fractal parameters and fractal roughness of the original layer. The identification principle is based on the autocorrelation function corresponding to the WM fractal function:
[0033] ; In the formula, z ( x ) represents the surface profile height; L Indicates the sampling length of the rough surface; D Let fractal dimension be denoted as . z ( x Irregularities in scale; G Fractal roughness is mainly determined by z ( x The magnitude of the amplitude; γ This is a scale parameter, related to the profile frequency density; n For frequency coefficients; The spatial frequency coefficient corresponding to the lowest cutoff frequency; This represents the distance delay coefficient.
[0034] Performing a Fourier transform on this equation, we obtain the power spectral density function of the WM fractal function as follows: ; After processing the power spectral density function of the WM fractal function using a logarithmic transformation, we obtain: ; In the formula, ω The frequency of the power spectral density function j The imaginary unit is used to represent the number. ω When the independent variable is used, the above equation can be viewed as a linear expression in a double logarithmic coordinate system, where the slope and intercept correspond to the fractal dimension and fractal roughness parameter, respectively. Figure 6 As shown.
[0035] Its corresponding slope k and intercept b They are respectively: ; ; slope k and interceptb Substituting into the expression processed using the logarithmic transformation method, we can see that: ; Rearranging this formula, we can obtain the fractal dimension. D and fractal roughness parameters G The expressions are as follows: ; .
[0036] In the theoretical calculation stage, based on the established fractal parameters of the original layers, multiple joints can be equivalently represented as composite layer joints using the virtual material method and the principle of strain energy conservation. This allows for the calculation of the contact stiffness, elastic modulus, and Poisson's ratio (i.e., mechanical parameters) of the composite layer joints. Specifically, this step requires, after determining the relevant material parameters, applying the fractal dimension identified in the preparation stage... D and fractal roughness parameters G Substituting these values into the formulas derived from theoretical calculations—namely, the analytical formulas for dimensionless normal load, elastic modulus, and Poisson's ratio—is used to determine the modeling parameters for the subsequent composite layer joint.
[0037] Specifically, based on the fractal parameters of each contact surface of the original layer and the material parameters of the composite layer joint, the normal contact stiffness and tangential contact stiffness of the composite layer joint are determined respectively; based on the normal contact stiffness, the elastic modulus of the composite layer joint is determined, and based on the tangential contact stiffness, the Poisson's ratio of the composite layer joint is determined.
[0038] In practical implementation, the derivation process of the theoretical formula is as follows: According to the relevant definitions in fractal theory, the area distribution function for the contact between a rough surface and a plane is: ; In the formula, This represents the theoretical contact area of the micro-contact point; This represents the maximum cross-sectional contact area. The field extension coefficient can be obtained from the fractal dimension D, and the corresponding mathematical expression is: ; In the formula, and These are the critical maximum cross-sectional contact area and the maximum cross-sectional contact area during the elastoplastic transition, respectively. and These are the actual critical area for the elastic-plastic transition and the actual maximum elastic micro-contact area, respectively. Since the cross-sectional area is twice the actual contact area, therefore: ; ; In the formula, The correlation coefficient; H Hardness of soft materials; σ The yield strength of soft materials; Material properties; A r This represents the actual contact area of the fractal region.
[0039] When subjected to a normal load at the micro-contact point, the normal loads of a single elastic micro-contact point and a single plastic micro-contact point in the joint are respectively: ; ; In the formula, This is the equivalent elastic modulus of the contact surface of the corresponding joint. , and These are the elastic moduli of the two contact surface materials, respectively. μ 1 and μ 2 represents the Poisson's ratio of the two contact surface materials.
[0040] By summing all the peaks and troughs of the contact surface morphology and making them dimensionless, the dimensionless normal load of the composite layer joint can be obtained. for: ; In the formula, each dimensionless expression is: ; ; ; ; A This represents the apparent contact area.
[0041] Based on the definition of normal stiffness of the joint, the normal contact stiffness of a single microprotrusion in contact with a plane can be obtained. k nV for: ; In the formula, R eq The equivalent radius of curvature of the micro-contact point. δ For local interference quantities, It is the equivalent elastic modulus of the virtual layer.
[0042] By summing all the peaks and troughs of the contact surface morphology, the normal stiffness of the virtual layer can be obtained as follows: ; Since the virtual layer in the composite layer joint is bound to the original layer, the total normal stiffness of the composite layer joint is... K n With virtual layer normal stiffnessK nV and original layer normal stiffness K nR The relationship is: ; Based on the normal stiffness of the virtual layer K nV Total normal stiffness at the interface with the composite layer K n The formula can be used to obtain the total normal stiffness of the composite layer joint. K n for: ; According to the principle of equal strain energy, under external load P Under the action, the normal stiffness of the composite layer slider joint is K n The generated global normal strain energy W 1 is: ; When converted to a continuous equivalent virtual elastic material, the unit's overall normal strain energy W 2 can be represented as: ; In the formula, σ n σ is the mean normal stress of the virtual material. n = P / A , h The thickness of the composite layer joint, E This represents the elastic modulus of the composite layer interface.
[0043] Depend on W 1= W As can be seen from 2, the elastic modulus of the composite layer joint is E for: ; Poisson's ratio is the ratio of lateral deformation to longitudinal deformation of a material under external force. It is an important parameter in studying the material properties of joints. For materials subjected to tangential loads... T Micro-bumps, tangential contact stiffness k tv It can be calculated as:
[0044] ; In the formula, G’ Let be the equivalent shear modulus of the two contacting rough surfaces. , G 1 , μ1 and G 2 , μ 2 These are the shear modulus and Poisson's ratio of the materials on both sides, respectively. f The static friction coefficient of the contact surface; β is the coefficient of kinetic friction of the contact surface.
[0045] By summing all the peaks and troughs of the contact surface morphology, the tangential stiffness of the virtual layer can be obtained. K tv for: ; Based on the bonding relationship, the tangential stiffness of the composite layer joint... K t Tangential stiffness of virtual layer K tv and original layer tangential stiffness K tR The relationship is: ; Based on the tangential stiffness of the virtual layer K tv Tangential stiffness at the interface with the composite layer K t The formula can be used to obtain the total tangential stiffness of the composite layer joint. K t for: ; Assuming the equivalent virtual material is isotropic, the Poisson's ratio at the composite layer interface can be derived. μ for: ; When solving, relevant material parameters and fractal parameters need to be substituted into the formula for the dimensionless normal load at the composite layer interface. After obtaining the contact rate, substitute the corresponding variables into the formula for the elastic modulus of the composite layer joint. E Poisson's ratio at the interface of the composite layer and formula μ The elastic modulus and Poisson's ratio of the composite layer joint can be obtained from the above calculation. The calculation process is as follows: Figure 7 As shown.
[0046] In the modeling and verification phase, after establishing the theoretical model of the composite layer joint and determining the relevant mechanical performance parameters, the finite element modeling phase begins. For components without composite layer joints, their actual material properties can be set in the custom material property module. However, for composite layer joints, based on the previously calculated mechanical performance parameters, they need to be treated as an equivalent virtual material, and the corresponding elastic modulus, Poisson's ratio, and other parameters need to be assigned to them in the finite element model. Furthermore, conditions such as fixed constraints and dynamic loads need to be determined based on the actual operating conditions of the target structure. Finally, the finite element model is solved, and the corresponding finite element simulation results are saved.
[0047] Meanwhile, to verify the accuracy of the finite element model, a corresponding modal testing platform needs to be built. Modal testing is an important technical means to study the dynamic characteristics of engineering structures. Based on modal analysis theory, this test artificially applies certain excitations to the engineering structure system, causing it to vibrate, and measures the vibration response of the structure at different frequencies, thereby determining the natural frequencies and mode shapes of the measured object. The testing platform should be able to simulate the stress and boundary conditions of the target structure under actual working conditions, such as load type, application mode, and constraint method, to ensure the representativeness and reliability of the test results.
[0048] If it is inconvenient to strike parts of the object under test with a force hammer, a force hammer excitation method with a fixed excitation point and a moving response point can be used in the measurement process. This method can simultaneously measure the structure's response in multiple directions, reducing repetitive operations and improving testing efficiency, and is suitable for field testing. Before conducting actual modal testing, a wireframe model of the structure under test needs to be established. This model consists of nodes and connecting lines, with the node positions corresponding to vibration measurement points or excitation points.
[0049] Finally, by comparing the simulation results with the experimental data, if the simulation results match the measured data well, it indicates that the theoretical model and material equivalent method have high accuracy and engineering applicability; if there is a large deviation, it is necessary to trace back the composite layer modeling assumptions, material parameter inputs or boundary condition settings, identify the source of error and correct it, so as to ensure the accuracy of the finite element model established by the standardized modeling of the composite layer joint.
[0050] The following specific embodiment illustrates the implementation process of the composite layer joint modeling method of the present invention: Taking the lifting column joint of a certain height-adjustable desk as an example, the slider and the desk tube in this joint will bear a large load when working. The mechanical properties of the connection between the two have a significant impact on the overall performance of the desk. Therefore, it can be considered as an application object for composite layer joints.
[0051] Considering that the slider is a key component connecting the transmission mechanism and the support structure in the lifting column of the electric height-adjustable desk, and mainly undertakes three major functions: motion guidance, load transmission and vibration suppression, its dynamic characteristics will directly affect the stability and vibration performance of the entire desk. Therefore, this embodiment selects the slider as the research object of the subsequent composite layer joint.
[0052] To further investigate the characteristics of the actual surface profile, this embodiment uses a Talysurf200 surface roughness tester to obtain the surface profile curve of the slider of the electric lifting table. The slider is made of POM and needs to be fixed to the measuring table during measurement. The surface profile data is obtained by contact measurement using a stylus. This method can be used for rapid measurement of the surface roughness profile of various parts and has the advantage of high measurement accuracy. The slider measurement length is 4 mm, the sampling interval is 2 μm, and the number of sampling points is 2000.
[0053] To reduce measurement errors in the slider surface contour data, the experiment used a multiple sampling method to obtain the slider contour data and plotted a two-dimensional contour curve of the horizontal distance of the micro-protrusions. Figure 8 The corresponding slider surface profile curve is shown.
[0054] Using the power spectral density method, the fractal dimension and fractal roughness parameters of the contact surface can be calculated based on the slope and intercept of the power spectral density function, preparing for the next stage of theoretical model calculation of the composite layer interface. During identification, the acquired two-dimensional contour curve needs to be treated as a random signal, and its power spectral density can be obtained by performing a Fourier transform. Subsequently, a double logarithmic coordinate curve is plotted and fitted using the least squares method. Figure 9 The fitted curve after frequency domain analysis is displayed. The slope and intercept are analyzed using the PSD method to determine the distribution pattern of the horizontal distance profile of the micro-protrusion. Finally, the fractal parameters of the slider contact surface are identified as D=1.5787 and G=4.5127×10⁻⁶. -10 m.
[0055] The necessary material parameters for the calculation process can be obtained by consulting material handbooks or relevant literature, such as the elastic modulus, Poisson's ratio, and density. When the data in the material handbook is inaccurate or inapplicable, experimental testing should be conducted to obtain the material parameters to ensure the reliability of the model. To verify the dynamic modeling method for the composite layer joint based on the virtual material method, the slider of the electric lifting table can be defined as the original layer based on the characteristics and geometric dimensions of the lifting column. The composite layer joint model is as follows: Figure 10As shown, the model originally consisted of three layers of material: isotropic virtual material layers with uniform cross-sections on both sides, and a solid slider layer in the middle. The virtual layer, the table tube layer, and the slider layer were all fixedly connected. By adopting the composite layer joint method, it can be equivalent to a single-layer structure, effectively reducing the difficulty of simulation modeling.
[0056] A slider needs to be installed between the outer tube, middle tube, and inner tube to meet relative lifting requirements. However, in actual production, there are design-allowed gaps between the mating surfaces of the table tube and the slider. These gaps can cause changes in contact force, thus affecting the dynamic characteristics of the kinematic pair and potentially even causing vibration and impact. Furthermore, the material properties of both the table tube and the slider affect the contact stiffness and friction characteristics, thereby altering the actual contact conditions at the joint and significantly increasing the difficulty of modeling. Therefore, accurately calculating the elastic modulus E and Poisson's ratio μ of the composite layer joint of the lifting column provides crucial parameters for establishing an accurate finite element model and is also significant for the optimized design and performance improvement of the electric lifting table.
[0057] Based on the parameter identification results, the fractal dimension D Take 1.5787, fractal roughness parameter G Take 4.5127×10 -10 m. Given that the table tube material is Q195, its elastic modulus is... E 1 represents 200 GPa, Poisson's ratio μ 1 is 0.3, density ρ 1 is 7.85 × 10 3 kg / m 3 Yield strength σ 1 is 195 MPa, Brinell hardness. H 1 is 130 MPa. The slider material is POM, and its elastic modulus is... E 2 is 2.6 GPa, Poisson's ratio μ 2 is 0.37, and density ρ2 is 1.51 × 10 3 kg / m 3 Yield strength σ 2 is 70 MPa, Brinell hardness H 2 is 100MPa. Normal load on the lifting table tube and slider. P Approximately 150N, contact area A a 8332mm 2 static friction coefficient f Set to 0.3, coefficient of kinetic friction β Then, a static friction coefficient of 0.9 is taken, and the composite layer density is defined as the average of the densities of the two layers, with a thickness of... h The slider parameters are the same as the original layer, set to 1mm.
[0058] According to the definition of equivalent elastic modulus, the equivalent elastic modulus of the composite layer joint can be obtained as follows: ; By calculating the material parameters, the shear moduli of the table tube and the slider can be obtained as follows: ; ; By defining the equivalent shear modulus, the equivalent shear modulus of two contacting rough surfaces can be obtained as follows: ; The correlation coefficients and material properties of the composite layer interface are as follows: ; ; Based on the relevant parameters, the normal stiffness and tangential stiffness of the slider can be obtained as follows: ; ; Substitute the normal load P into the dimensionless normal load of the composite layer joint. From the expression, the contact rate at the joint of the composite layer can be obtained. for: ; Contact rate at the joint of composite layers Substitute the total normal stiffness of the composite layer joint K n Expression and total tangential stiffness at the composite layer junction K t In the expression, the normal stiffness and tangential stiffness of the composite layer joint are obtained as follows: ; ; Substituting the normal stiffness and tangential stiffness of the composite layer joint into the elastic modulus of the composite layer joint, respectively. E Expression and Poisson's ratio at the composite layer junction μ From the expression, the elastic modulus and Poisson's ratio of the composite layer joint can be obtained as follows: ; ; The upright column of a height-adjustable desk is a key structure, typically composed of a desk tube, a slider, and a transmission assembly. The desk tube comprises an outer tube, a middle tube, and an inner tube. The slider, acting as a transition component, connects the outer, middle, and inner tubes of the desk tube through preload. These components exhibit complex kinematic relationships and interactions, and their contact behavior directly affects the system's stiffness and dynamic characteristics. Therefore, this embodiment focuses on the contact between the desk tube and the slider in the upright column as the research object of the composite layer joint. Figure 11 This is the finite element model of the lifting column studied in this embodiment, with the middle part being the joint of the lifting column.
[0059] To ensure the accuracy of the composite layer bonding characteristics, modal testing was used for verification. The number of nodes for the modal test of the lifting column of the electric lifting table was set to 24, with node 5 as the excitation point. The number of nodes for the entire table test was set to 19, with node 6 as the excitation point. The node arrangement for the corresponding lifting column is as follows. Figure 12 As shown.
[0060] Taking the lifting column as an example, the modal test requires suspending the lifting column on a fixed platform using two elastic ropes to simulate a free suspension state. The test uses the hammer impact method to excite the specimen, and data is collected by an accelerometer. Each data acquisition node is subjected to three effective excitations, and the average value is taken to analyze the first four free modal frequencies and their mode shape changes of the lifting column of the lifting table.
[0061] Based on the above modal parameter settings, frequency response tests were performed on 24 nodes of the lifting column of the electric lifting table using an excitation hammer. The collected excitation and response signals were then processed using ModelVIEW software to obtain... Figure 13 The modal experiment frequency response curve is shown.
[0062] To verify the correctness of the dynamic modeling method proposed in this embodiment, the composite layer method and the binding method in traditional modeling were used to perform dynamic simulation analysis on the lifting column system of the lifting table. The relative error of the natural frequencies between the simulation analysis and modal test results was calculated, and the consistency of the vibration modes was quantitatively evaluated. Finally, the simulation results of the two methods were systematically compared and analyzed with the experimental modal test results. Table 1 and... Figure 14 The results shown are the modal test and finite element simulation results of the corresponding lifting column.
[0063] Table 1 shows a significant difference in modal frequency prediction accuracy between the composite layer modeling method and the conventional binding method. The composite layer modeling method achieves an error of only 2.13% in the high-order mode f4, while the conventional binding method exhibits larger errors in modes f1, f3, and f4, reaching 19.15%, 21.2%, and 35.25%, respectively. Simulation results indicate that the error of the conventional binding method increases significantly with frequency, reaching 21.20% in mode f3 and a maximum of 35.25% in mode f4. This reflects the method's insufficient ability to capture the dynamic characteristics of high-order modes, while the composite layer method, by accurately simulating the interlayer contact characteristics of the material, better reflects the actual stiffness distribution of the structure. Analyzing the average error data, the binding method has an average error of 20.25%, while the composite layer method has an average error of 7.55%, representing a 62.72% reduction in simulation error. In summary, compared with the conventional binding method, the composite layer method exhibits higher accuracy in modal simulations of all orders, further verifying the accuracy of the modeling method proposed in this embodiment.
[0064] Table 1. Comparison of Simulation and Experimental Results of Natural Frequency of Lifting Column from Figure 14 It can be seen that the simulated vibration modes obtained by the binding method and the composite layer method are consistent with the experimental results, namely, vertical bending, lateral bending, combined bending, and axial torsion modes. The results show that the composite layer method not only performs well in frequency prediction but also exhibits good matching in mode shape reconstruction. Although the conventional binding modeling method has some errors in frequency prediction, its mode shape characteristics still maintain the correct structure, indicating that this method still has some reference value in qualitative research. In summary, the composite layer method has good accuracy and reliability in simulating structural vibration characteristics, can meet the needs of engineering analysis, and further verifies the accuracy of the modeling method proposed in this embodiment.
[0065] The composite layer joint modeling method of this invention proposes the concept of composite layer joints. By constructing composite layer joints, the cumbersome steps of analyzing each joint individually in traditional modeling can be avoided, effectively reducing modeling difficulty and improving simulation efficiency. Following the modeling process of composite layer structures, a standardized modeling process based on composite layer joints is proposed, and an electric height-adjustable table is selected as an engineering case to conduct multi-dimensional dynamic characteristic verification, demonstrating certain engineering application value.
[0066] The steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they include the same logical relationship, they are all within the protection scope of this invention. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, without changing the core design of the algorithm and process, are also within the protection scope of this invention.
[0067] Another embodiment of the present invention relates to a composite layer joint modeling system. The implementation details of this composite layer joint modeling system are described below. The following details are provided for ease of understanding and are not essential for implementing this solution. The composite layer joint modeling system of this embodiment includes: The topography data acquisition module is used to acquire the surface topography data of the contact surface of each of N series-connected joints in a mechanical structure; where N is greater than or equal to 1. The fractal parameter determination module is used to determine the fractal parameters of the contact surface of each joint based on the surface morphology data. The joint equivalent module is used to, based on the virtual material method, equate each contact surface of each joint to a virtual material, and equate all joints and all virtual materials to a composite layer joint; wherein, the composite layer joint consists of N joints and N+1 virtual materials; The mechanical parameter determination module is used to determine the mechanical parameters of the composite layer joint based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint. The joint modeling module is used to model the joint of the composite layer based on the mechanical parameters of the joint.
[0068] It is not difficult to see that this embodiment is a system embodiment corresponding to the above method embodiments, and this embodiment can be implemented in conjunction with the above method embodiments. The relevant technical details and technical effects mentioned in the above embodiments are still valid in this embodiment, and will not be repeated here to reduce repetition. Accordingly, the relevant technical details mentioned in this embodiment can also be applied to the above embodiments.
[0069] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this invention, this embodiment does not introduce units that are not closely related to solving the technical problem proposed by this invention; however, this does not mean that other units are absent from this embodiment.
[0070] Another embodiment of the present invention relates to a computer device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the composite layer junction modeling method in the above embodiments.
[0071] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other systems over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.
[0072] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.
[0073] Another embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the method embodiments described above.
[0074] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0075] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.
Claims
1. A method for modeling the joint of composite layers, characterized in that, The method includes: For N series joints in a mechanical structure, obtain the surface morphology data of the contact surface of each joint; where N is greater than or equal to 1. Based on the surface morphology data, determine the fractal parameters of the contact surface of each joint; Based on the virtual material method, each contact surface of each joint is equivalent to a virtual material, and all joints and all virtual materials are equivalent to a composite layer joint; wherein, the composite layer joint consists of N joints and N+1 virtual materials; The mechanical parameters of the composite layer joint are determined based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint. The composite layer joint is modeled based on the mechanical parameters of the composite layer joint.
2. The composite layer joint modeling method according to claim 1, characterized in that, The fractal parameters include fractal dimension and fractal roughness.
3. The composite layer joint modeling method according to claim 2, characterized in that, The step of determining the fractal parameters of the contact surface of each joint based on surface morphology data includes: Based on the surface morphology data, Fourier transforms are performed on the autocorrelation functions corresponding to the following WM fractal functions: ； In the formula, L For rough surface sampling length, z ( x ) represents the surface profile height. This is the distance delay coefficient. D For fractal dimension, G For fractal roughness, γ For scale parameters, n For frequency coefficients, The spatial frequency coefficient corresponding to the lowest cutoff frequency; The power spectral density function of the WM fractal function is obtained as follows: ； In the formula, ω The frequency of the power spectral density function j The imaginary unit; Logarithmic transformation of the power spectral density function of the WM fractal function yields: ； Using the obtained formula as a linear expression in logarithmic coordinates, we can obtain the slope and intercept of the linear expression: ； ； In the formula, k The slope b The intercept; Substituting the slope and intercept into the formula obtained using logarithmic transformation, we get: ； The fractal dimension and fractal roughness are obtained as follows: ； ； In the formula, D For fractal dimension, G This refers to fractal roughness.
4. The composite layer joint modeling method according to claim 3, characterized in that, The mechanical parameters include elastic modulus and Poisson's ratio.
5. The composite layer joint modeling method according to claim 4, characterized in that, When N is 1, the elastic modulus of the composite layer joint is determined by the following steps: Obtain the area distribution function for the case where a rough surface is in contact with a plane: ； In the formula, This represents the theoretical contact area of the micro-contact point. To maximize the cross-sectional contact area, For the domain expansion coefficient; When subjected to normal loads at micro-contact points, the normal loads of individual elastic and plastic micro-contact points in each joint are as follows: ； ； In the formula, This is the equivalent elastic modulus of the contact surface of the corresponding joint. , H The hardness of soft materials, σ The yield strength of soft materials; By summing all the peaks and troughs of the surface topography data and making them dimensionless, the dimensionless normal load at the composite layer interface is obtained as follows: ； In the formula, , , , , A The apparent contact area, This represents the actual contact area of the fractal region. and These are the critical maximum cross-sectional contact area and the maximum cross-sectional contact area during the elastoplastic transition, respectively. and These are the actual critical area for the elastoplastic transition and the actual maximum elastic micro-contact area, respectively. , , ; Obtain the normal contact stiffness of a single microprotrusion in contact with a plane. k nV : ； In the formula, R eq The equivalent radius of curvature of the micro-contact point. δ For local interference quantities, The equivalent elastic modulus of the virtual layer; By summing all the peaks and troughs of the surface topography data, the normal stiffness of the virtual material is obtained as follows: ； Normal stiffness of composite layer joint K n With the normal stiffness of virtual materials K nv Normal stiffness of the joint K nR The relationship between them is: ； In the formula, K nV1 and K nv2 These are the normal stiffnesses of the two virtual materials, respectively. Substituting the normal stiffness of the virtual material into the relationship between the normal stiffness of the composite layer joint and the normal stiffness of the virtual material and the joint, the normal stiffness of the composite layer joint is obtained as follows: ； The overall normal strain energy generated by the normal stiffness of the composite layer joint is: ； In the formula, P For external loads; When converted to a virtual material, the overall normal strain energy of the unit is: ； In the formula, σ n σ is the mean normal stress of the virtual material. n = P / A , h The thickness of the composite layer joint, E The elastic modulus of the composite layer joint; ； In the formula, W 1= W 2.
6. The composite layer joint modeling method according to claim 5, characterized in that, The Poisson's ratio of the composite layer joint is determined by the following formula: Obtain the tangential contact stiffness of a single microprotrusion in contact with a plane: ； In the formula, Let be the equivalent shear modulus of the two contacting rough surfaces. f The static friction coefficient of the contact surface is . β The coefficient of dynamic friction of the contact surface; By summing all the peaks and troughs of the surface topography data, the tangential stiffness of the virtual material is obtained as follows: ； Tangential stiffness of composite layer joint K t Tangential stiffness of virtual materials K tv Tangential stiffness of the joint K tR The relationship between them is: ； In the formula, K tV1 and K tv2 These are the tangential stiffnesses of the two virtual materials, respectively. Substituting the tangential stiffness of the virtual material into the relationship between the tangential stiffness of the composite layer joint and the tangential stiffness of the virtual material and the joint, the tangential stiffness of the composite layer joint is obtained as follows: ； When the virtual material is isotropic, the Poisson's ratio at the composite layer interface is: 。 7. A modeling system for composite layer joints, characterized in that, The system includes: The topography data acquisition module is used to acquire the surface topography data of the contact surface of each of N series-connected joints in a mechanical structure; where N is greater than or equal to 1. The fractal parameter determination module is used to determine the fractal parameters of the contact surface of each joint based on the surface morphology data. The joint equivalent module is used to, based on the virtual material method, equate each contact surface of each joint to a virtual material, and equate all joints and all virtual materials to a composite layer joint; wherein, the composite layer joint consists of N joints and N+1 virtual materials; The mechanical parameter determination module is used to determine the mechanical parameters of the composite layer joint based on the fractal parameters of each contact surface, the material parameters of each joint, and the material parameters of the two parts connected by the composite layer joint. The joint modeling module is used to model the joint of the composite layer based on the mechanical parameters of the joint.
8. A computer device, characterized in that, include: At least one processor; And a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the composite layer junction modeling method as described in any one of claims 1 to 6.
9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the composite layer junction modeling method as described in any one of claims 1 to 6.