Method, device and equipment for determining tangential contact rigidity of bolting joint surface

Abstract

The invention discloses a method, a device and equipment for determining the tangential contact rigidity of a bolting joint surface. The method comprises the following steps: constructing a pre-tightening force relaxation model for representing the change relation of the pre-tightening force of a bolting structure along with time; respectively constructing a fractal dimension model and a surface roughness model for representing the change relation of the fractal dimension and the surface roughness of the bolted joint surface along with time based on the pre-tightening force relaxation model; based on the pre-tightening force relaxation model, the fractal dimension model and the surface roughness model, constructing a tangential contact rigidity model of the bolting joint surface, wherein the tangential contact rigidity of the bolting joint surface changes along with time; and inputting the assembly time of a to-be-evaluated target bolting structure into the tangential contact stiffness model, and calculating the tangential contact stiffness of the target bolting structure so as to evaluate the target bolting structure based on the determined tangential contact stiffness. Through the method, the tangential contact stiffness of the bolting joint surface can be calculated more accurately and reliably, and a basis is provided for accurate prediction of the time-varying characteristic of the dynamic performance of the whole machine.

Description

Technical Field

[0001] The present application relates to the technical field of dynamic analysis of bolt structures, and in particular to a method, device and equipment for determining the tangential contact stiffness of a bolted joint surface. Background Art

[0002] Bolt connection is a widely used connection method for construction machinery. The contact stiffness of its joint surface is crucial to ensure the dynamic characteristics and service reliability of the whole machine. As the weak link of the whole machine, the contact stiffness of the joint surface of the bolted structure (hereinafter referred to as the bolted joint surface) accounts for 30%-50% of the stiffness of the whole machine. Its assembly preload and surface roughness are the main factors affecting the contact stiffness of the joint surface.

[0003] At present, a lot of research has been carried out on the contact stiffness of bolted joints, and statistical, fractal and multi-scale models have been proposed to calculate the contact stiffness. This type of model can be used to predict the contact stiffness of bolted joints under quasi-static or slow running speeds, but it cannot accurately predict the contact characteristics under motion conditions. The assembly preload and the surface roughness under its action inevitably change over time, causing the contact stiffness of the joint surface to decrease, making it difficult for the dynamic characteristics and service reliability of the whole machine to meet the requirements. Long-term dynamic characteristic monitoring based on experimental tests is costly and difficult to operate. In addition, the contact stiffness of the bolted joint surface includes two components: normal and tangential. Among them, the tangential stiffness is related to the tangential load and normal load, and the modeling process is more complicated.

[0004] There is currently no effective solution to the problems of high cost and difficulty in tracking the dynamic characteristics tests of the above-mentioned complex mechanical products. Summary of the invention

[0005] The purpose of the embodiments of this specification is to provide a method, device and equipment for determining the tangential contact stiffness of a bolted joint surface, so as to solve the problem of high cost and difficult tracking of dynamic characteristic tests of complex mechanical products.

[0006] In order to solve the above technical problems, the first aspect of this specification provides a method for determining the tangential contact stiffness of a bolted joint surface, comprising:

[0007] Constructing a preload relaxation model, wherein the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time;

[0008] Based on the preload relaxation model, a fractal dimension model and a surface roughness model of the bolted joint surface are constructed, wherein the fractal dimension model and the surface roughness model are used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and the time variation;

[0009] Based on the preload relaxation model, the fractal dimension model and the surface roughness model, a tangential contact stiffness model of the bolted joint surface that varies with time is constructed;

[0010] The assembly time of the target bolted structure to be evaluated is input into the tangential contact stiffness model, and the tangential contact stiffness of the target bolted structure is calculated to evaluate the target bolted structure based on the determined tangential contact stiffness.

[0011] In some embodiments of this specification, constructing a preload relaxation model includes:

[0012] Simulate vibration conditions and record the preload relaxation data of bolted structures at different times;

[0013] The preload relaxation model is obtained by fitting based on the preload relaxation data and the corresponding time.

[0014] In some embodiments of the present specification, a fractal dimension model and a surface roughness model of the bolted joint surface are constructed based on the preload relaxation model, including:

[0015] Acquiring microscopic morphology data of the bonding surfaces of the plurality of bolted structures at the initial moment as initial microscopic morphology data;

[0016] Determine the preload simulation step length and preload simulation range corresponding to each bolted structure;

[0017] Based on the preload relaxation model and the preload simulation step length and preload simulation range corresponding to each bolted structure, a plurality of simulated preloads and corresponding simulation times corresponding to each bolted structure are determined;

[0018] Acquire simulated microscopic morphology data of the joint surface of each bolted structure under corresponding multiple simulated preloads and simulated times;

[0019] Based on the initial micro-morphology data and simulated micro-morphology data of multiple bolted structures, the fractal dimension data and surface roughness data corresponding to each bolted structure at different simulation times are determined;

[0020] The fractal dimension model and the surface roughness model are respectively constructed based on the fractal dimension data and the surface roughness data of each bolted structure at multiple simulation times.

[0021] In some embodiments of the present specification, based on the preload relaxation model, the fractal dimension model and the surface roughness model, a tangential contact stiffness model of the bolted joint surface that varies with time is constructed, including:

[0022] Based on the preload relaxation model, a tangential load time-varying characteristic model and a normal load time-varying characteristic model of the bolted joint surface are constructed;

[0023] The tangential contact stiffness model is constructed based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model.

[0024] In some embodiments of the present specification, the tangential contact stiffness model is constructed based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model, including:

[0025] Based on the fractal dimension model and the surface roughness model, a mapping model between each micro-convex body on the bolted joint surface and the fractal dimension and the surface roughness is constructed, and a coefficient related to the geometric shape of each micro-convex body is defined;

[0026] Based on the mapping model, the defined coefficients, the tangential load time-varying characteristic model and the normal load time-varying characteristic model, an elastic tangential contact stiffness sub-model, an elastic-plastic tangential contact stiffness sub-model and a plastic tangential stiffness sub-model are constructed;

[0027] The tangential contact stiffness model is constructed based on the elastic tangential contact stiffness sub-model, the elastoplastic tangential contact stiffness sub-model and the plastic tangential stiffness sub-model.

[0028] In some embodiments of the present specification, the mapping model and the coefficients related to the geometric shape of each micro-protrusion are expressed by the following formula:

[0029]

[0030] Where h represents the height of a single microconvex body, h i represents the height of a single micro-convex body of the i-th bolted joint surface in multiple bolted structures, D(t) represents the fractal dimension of the bolted joint surface at time t, G(t) represents the surface roughness of the bolted joint surface at time t, γ represents the spectral density parameter, r represents the radius of the micro-convex cross section, and λ represents the coefficient related to the geometric shape of the micro-convex body.

[0031] In some embodiments of the present specification, the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model are respectively expressed by the following formulas:

[0032]

[0033] Among them, K e (t) represents the elastic tangential contact stiffness of the bolted structure at time t, K ep(t) represents the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) represents the plastic tangential stiffness of the bolted structure at time t, D(t) represents the fractal dimension of the bolted joint surface at time t, λ represents the coefficient related to the geometric shape of the micro-convex body, G 1 and G 2 represents the shear modulus of the rough surface, υ 1 and 2 represents the Poisson's ratio of the material of the bolted structure, ψ represents the domain expansion factor, and a l represents the maximum cross-sectional area of ​​the microconvex body, a 1c The critical cross-sectional area for the transition from elastic deformation to elastic-plastic deformation, a 2c The critical cross-sectional area for the transition from elastic-plastic deformation to plastic deformation, H g represents the coefficient related to the material and fractal parameters of the bolted structure, F τ (t) represents the tangential load of the bolted structure at time t, F n (t) represents the normal load of the bolted structure at time t, and μ represents the friction coefficient.

[0034] In some embodiments of the present specification, the tangential contact stiffness model is expressed by the following formula:

[0035]

[0036] Among them, K τ (t) represents the tangential contact stiffness of the bolted structure at time t, K e (t) represents the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) represents the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) represents the plastic tangential stiffness of the bolted structure at time t, a l represents the maximum cross-sectional area of ​​the microconvex body, a 1c The critical cross-sectional area for the transition from elastic deformation to elastic-plastic deformation, a 2c It represents the critical cross-sectional area where elastic-plastic deformation transforms into plastic deformation.

[0037] A second aspect of the present specification provides a device for determining the tangential contact stiffness of a bolted joint surface, comprising:

[0038] A first modeling module is used to construct a preload relaxation model, wherein the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time;

[0039] A second modeling module is used to construct a fractal dimension model and a surface roughness model of the bolted joint surface based on the preload relaxation model, wherein the fractal dimension model and the surface roughness model are used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and the time variation;

[0040] A third modeling module is used to construct a tangential contact stiffness model of the bolted joint surface in which the tangential contact stiffness varies with time based on the preload relaxation model, the fractal dimension model and the surface roughness model;

[0041] The calculation module is used to input the assembly time of the target bolted structure to be evaluated into the tangential contact stiffness model, calculate the tangential contact stiffness of the target bolted structure, and evaluate the target bolted structure based on the determined tangential contact stiffness.

[0042] The third aspect of this specification provides an electronic device, comprising: a memory and a processor, the processor and the memory are communicatively connected to each other, the memory stores computer instructions, and the processor implements the steps of the method described in the first aspect by executing the computer instructions.

[0043] The method, device and equipment for determining the tangential contact stiffness of the bolted joint surface provided in the embodiments of this specification are as follows: a preload relaxation model is constructed to characterize the relationship between the preload of the bolted structure and time; a fractal dimension model and a surface roughness model are constructed based on the preload relaxation model to characterize the relationship between the fractal dimension and the surface roughness of the bolted joint surface and time; a tangential contact stiffness model is constructed based on the preload relaxation model, the fractal dimension model and the surface roughness model to characterize the relationship between the fractal dimension and the surface roughness of the bolted joint surface and time; the assembly time of the target bolted structure to be evaluated is input into the tangential contact stiffness model, and the tangential contact stiffness of the target bolted structure is calculated to evaluate the target bolted structure based on the determined tangential contact stiffness. Through the above method, the characteristics of the preload of the bolted structure changing with time are considered in the component preload relaxation model, and then the fractal dimension model and the surface roughness model constructed based on the preload relaxation model also consider the characteristics of the fractal dimension and the surface roughness changing with time. Furthermore, the tangential stiffness model constructed on this basis can also consider the influence of assembly preload, fractal dimension and time-varying characteristics of surface roughness on the tangential contact stiffness of the bolted joint surface, and calculate a more accurate and reliable tangential contact stiffness of the bolted joint surface, which can solve the problems of long dynamic characteristics testing cycle and high cost, and provide a basis for the accurate prediction of the time-varying characteristics of the dynamic performance of the whole machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0045] Figure 1 It is a schematic diagram of a method for determining the tangential contact stiffness of a bolted joint surface provided in an embodiment of this specification;

[0046] Figure 2 Shown is a schematic diagram of the fractal dimension model and the surface roughness model construction method provided in the embodiments of this specification;

[0047] Figure 3 It is a schematic diagram of a method for predicting the nonlinear evolution of tangential contact stiffness of bolted joint surfaces based on statistics and fractals provided in an embodiment of this specification;

[0048] Figure 4 Shown is a schematic diagram of the three-dimensional microscopic morphology of the bolted joint surface provided in the embodiment of this specification;

[0049] Figure 5 Shown is a schematic diagram of a refined finite element model of a bolted structure provided in an embodiment of this specification;

[0050] Figure 6 It is a schematic diagram showing the comparison of time-varying curves of the first-order natural frequency considering the tangential contact stiffness provided in the embodiment of this specification;

[0051] Figure 7 Shown is a schematic diagram of a device for determining the tangential contact stiffness of a bolted joint surface provided in an embodiment of this specification;

[0052] Figure 8 Shown is a schematic diagram of an electronic device provided in an embodiment of this specification. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0054] As mentioned above, the current contact stiffness model of bolted joints can only be used to predict the contact stiffness of bolted joints under quasi-static or slow running speeds, but cannot accurately predict the contact characteristics under moving conditions. Long-term dynamic characteristic monitoring based on experimental tests is costly and difficult to operate.

[0055] In order to solve the above problems, a method for determining the tangential contact stiffness of a bolted joint surface is provided in an embodiment of the present specification. When constructing a component preload relaxation model, the time-varying characteristics of the preload of the bolted structure are considered, and then the fractal dimension model and the surface roughness model constructed based on the preload relaxation model also consider the time-varying characteristics of the fractal dimension and surface roughness. Furthermore, the tangential stiffness model constructed on this basis can also consider the influence of the assembly preload, fractal dimension and the time-varying characteristics of the surface roughness on the tangential contact stiffness of the bolted joint surface, and calculate a more accurate and reliable tangential contact stiffness of the bolted joint surface, which can solve the problems of long dynamic characteristics test cycle and high cost, and provide a basis for the accurate prediction of the time-varying characteristics of the dynamic performance of the whole machine.

[0056] In the method provided in the embodiment of the present application, the execution subject of each step may be an electronic device, which refers to an electronic device with data calculation, processing and storage capabilities. The electronic device may be a terminal such as a personal computer (PC), a tablet computer, a smart phone, a wearable device, an intelligent robot, etc.; or it may be a server. Among them, the server may be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0057] The following first introduces the method for determining the tangential contact stiffness of the bolted joint surface provided in the embodiment of the present application in conjunction with the accompanying drawings.

[0058] Figure 1 Shown is a schematic diagram of a method for determining the tangential contact stiffness of a bolted joint provided in an embodiment of this specification. Although this specification provides method operation steps or device structures as shown in the following embodiments or drawings, the method or device may include more or fewer operation steps or module units after partial combination based on routine or no creative labor. In steps or structures that do not logically have a necessary causal relationship, the execution order of these steps or the module structure of the device is not limited to the execution order or module structure shown in the embodiments or drawings of this specification. When the method or module structure described is applied in actual devices, servers or terminal products, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or drawings (for example, in a parallel processor or multi-threaded processing environment, or even in a distributed processing or server cluster implementation environment). As Figure 1 As shown, the method may include:

[0059] S101: constructing a preload relaxation model, wherein the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time.

[0060] It is understandable that after the bolted structure is tightened, the preload will decrease over time under the influence of excitations such as vibration, that is, the preload relaxes. Specifically, the preload relaxation data at different times can be obtained by simulating vibration excitation, and a preload relaxation model can be constructed.

[0061] In some embodiments of the present specification, constructing a preload relaxation model may include: simulating vibration conditions and recording preload relaxation data of the bolted structure at different times; and fitting the preload relaxation model based on the preload relaxation data and the corresponding times.

[0062] Among them, the vibration condition can be simulated by a fatigue tensile testing machine and other devices, and the preload relaxation data and its corresponding time can be obtained through simulation, and the relationship between the preload and time can be fitted to obtain a preload relaxation model.

[0063] In some embodiments of the present specification, the preload relaxation model can be expressed by the following formula:

[0064] F(t)=(ae bt +ce dt )F(0) Formula (1)

[0065] Wherein, F(t) may represent the preload force of the bolted structure at time t, F(0) may represent the preload force of the bolted structure at the initial time, and a, b, c, and d may represent coefficients.

[0066] It can be understood that the relationship between the preload force and time in the above exponential form can be a mapping relationship between the preload force and time obtained by fitting in the embodiments of this specification. In other embodiments, the preload force relaxation model can also be represented by other forms of model structures, and this application is not limited to this.

[0067] S102: constructing a fractal dimension model and a surface roughness model of the bolted joint surface based on the preload relaxation model, wherein the fractal dimension model and the surface roughness model are respectively used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and the time variation.

[0068] It can be understood that the calculation of fractal dimension and surface roughness can be based on the calculation of the microscopic three-dimensional morphology of the bolted joint surface, and the microscopic three-dimensional morphology of the bolted joint surface will change with the change of the preload force. And because the preload force has a time-varying characteristic, the fractal dimension model and the surface roughness model can be constructed based on the constructed preload relaxation model.

[0069] Specifically, since the relationship between the change of preload and time in the preload relaxation model is a continuously changing curve, in order to facilitate the construction of the fractal dimension model and the surface roughness model, multiple discrete points can be selected on the curve based on the preload relaxation model, and the preload and time corresponding to each point can be determined. Experimental simulation is carried out, and the microscopic three-dimensional morphology of the bolted joint surface under the preload corresponding to each point is measured and recorded. Then, based on the recorded microscopic three-dimensional morphology and the corresponding preload time, a fractal dimension model of the relationship between the fractal dimension and the time change and a surface roughness model of the relationship between the surface roughness and the time change are constructed to reflect the time-varying characteristics of the fractal dimension and the surface roughness.

[0070] refer to Figure 2 As shown, in some embodiments of this specification, constructing a fractal dimension model and a surface roughness model of a bolted joint surface based on the preload relaxation model may include:

[0071] S201: Acquire microscopic morphology data of bonding surfaces of a plurality of bolted structures at an initial moment as initial microscopic morphology data.

[0072] It can be understood that the multiple bolted structures can be multiple samples processed under the same process parameters, or multiple samples processed under the same process parameters. For the bolted structures that have been processed, a three-dimensional micro-topography instrument can be used to obtain the micro-topography data of the joint surface as the initial micro-topography data. That is, the initial moment is the moment when the bolted structure is not equipped with pre-tightening force. The initial micro-topography data can be understood as the three-dimensional topography data of the bolted joint surface without pre-tightening force, which can be recorded as z 1 (x,y).

[0073] S202: Determine the preload simulation step length and preload simulation range corresponding to each bolted structure.

[0074] It can be understood that the preload force simulation step size can represent the step size between multiple preload forces used to simulate the simulated microscopic morphology data, and the preload force simulation range can be used to represent the value range of multiple preload forces, which may include an upper limit and a lower limit.

[0075] Specifically, the preload simulation step and preload simulation range can be determined based on the parameters of the bolted structure. When determining the preload simulation step and preload simulation range, the friction coefficient standard, mechanical design manual, etc. can be combined to determine the relationship between the simulation step and simulation range and the parameters of the bolted structure, and then based on the determined relationship and the values ​​of the parameters of each bolted structure, the preload simulation step and preload simulation range corresponding to each bolted structure can be determined.

[0076] In some embodiments of the present specification, the preload simulation step length can be calculated by the formula (F(0)-0.55σ s A) / N. Among them, F(0) can represent the preload force of the bolted structure at the initial moment, σ s It can represent the yield strength of the material of the bolted structure, A can represent the cross-sectional area of ​​the bolted structure, and N can represent the number of bolted structures. The preload simulation range can be based on the yield strength of the bolt material σ s (0.55-F(0) / σ s A) times the range. That is, the yield strength of the bolted structural material σ s (0.55-F(0) / σ s A) times, calculate (F(0)-0.55σ s A) multiple preload forces and their corresponding times under the step size of / N. The time corresponding to the preload force can be obtained by substituting multiple simulated preload forces determined based on the preload force simulation step size and the preload force simulation range into the constructed preload force relaxation model to obtain the simulation time corresponding to each preload force.

[0077] S203: Determine a plurality of simulated preloads and corresponding simulation times corresponding to each bolted structure based on the preload relaxation model and the preload simulation step length and preload simulation range corresponding to each bolted structure.

[0078] Specifically, multiple simulated preloads corresponding to each bolted structure can be determined based on the preload simulation step and the preload simulation range, and the multiple determined simulated preloads are respectively substituted into the preload relaxation model to obtain the simulation time corresponding to each preload.

[0079] S204: Acquire simulated microscopic morphology data of the joint surface of each bolted structure under corresponding multiple simulated preload forces and simulated times.

[0080] Specifically, multiple simulated preloads corresponding to each bolted structure can be sequentially loaded on the corresponding bolted structure, and then the bolted structure can be disassembled to measure and record the three-dimensional morphology data of the bolted joint surface under different simulated preloads. The simulated microscopic three-dimensional morphology data of each bolted structure can be recorded as z 2 (x,y),z 3 (x,y), ..., z N (x,y).

[0081] S205: Based on the initial microscopic morphology data and the simulated microscopic morphology data of the plurality of bolted structures, the fractal dimension data and the surface roughness data corresponding to each bolted structure at different simulation times are determined.

[0082] Specifically, based on the initial micro-morphology data and the simulated micro-morphology data, the mapping relationship between the fractal dimension and the micro-morphology, and the mapping relationship between the surface roughness and the micro-morphology can be combined to calculate the fractal dimension data and the surface roughness data corresponding to each micro-morphology data. The fractal dimension data and the surface roughness data can be recorded as D(t 1 )、D(t 2 ),…,D(t N ) and G(t 1 )、G(t 2 ),…,G(t N ).

[0083] S206: constructing the fractal dimension model and the surface roughness model respectively based on the fractal dimension data and the surface roughness data of each bolted structure at multiple simulation times.

[0084] It can be understood that when constructing a fractal dimension model, the fractal dimension data at multiple simulation times can be used to fit the mapping relationship between the fractal dimension and time to obtain a fractal dimension model. When constructing a surface roughness model, the surface roughness data at multiple simulation times can be used to fit the mapping relationship between the surface roughness and time to obtain a surface roughness model.

[0085] It should be noted that when different methods are used to calculate fractal dimension data and surface roughness data, the function forms corresponding to the fitted fractal dimension model and surface roughness model are also different. This application does not limit the specific calculation methods of fractal dimension data and surface roughness data, as well as the expression forms of fractal dimension models and surface roughness models.

[0086] S103: Based on the preload relaxation model, the fractal dimension model and the surface roughness model, a tangential contact stiffness model of the bolted joint surface that varies with time is constructed.

[0087] It can be understood that the tangential contact stiffness is affected by the preload, fractal dimension and surface roughness. Since the constructed preload relaxation model, fractal dimension model and surface roughness model are all time-varying models, a time-varying tangential contact stiffness model can be obtained based on this construction.

[0088] In some embodiments of the present specification, a tangential contact stiffness model of the bolted joint surface that varies with time is constructed based on the preload relaxation model, the fractal dimension model, and the surface roughness model. This may include: constructing a tangential load time-varying characteristic model and a normal load time-varying characteristic model of the bolted joint surface based on the preload relaxation model; and constructing the tangential contact stiffness model based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model, and the surface roughness model.

[0089] Furthermore, the time-varying characteristics of the tangential load and the normal load on the bolted joint surface under the action of the preload F(t) can be simulated and analyzed based on the refined finite element model of the bolted structure, and the corresponding mathematical equations, namely the time-varying characteristic model of the tangential load and the time-varying characteristic model of the normal load, can be established based on the analysis results. The tangential load at time t can be expressed as F τ (t), the normal load at time t can be expressed as F n (t).

[0090] In some embodiments of the present specification, constructing the tangential contact stiffness model based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model may include: constructing a mapping model between each micro-protrusion on the bolted joint surface and the fractal dimension and surface roughness based on the fractal dimension model and the surface roughness model, and defining coefficients related to the geometric shape of each micro-protrusion; constructing an elastic tangential contact stiffness sub-model, an elastic-plastic tangential contact stiffness sub-model and a plastic tangential stiffness sub-model based on the mapping model, the defined coefficients, the tangential load time-varying characteristic model and the normal load time-varying characteristic model; constructing the tangential contact stiffness model based on the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model and the plastic tangential stiffness sub-model.

[0091] It can be understood that the bolted joint surface is a relatively smooth surface at the macroscopic level, but is a surface composed of multiple micro-asperities at the microscopic level. Therefore, before constructing the tangential contact stiffness model, a mapping model between each micro-asperity and the fractal dimension and surface roughness can be constructed based on the fractal dimension model and the surface roughness model, and coefficients related to the geometric shape of each micro-asperity can be defined. Then, based on the defined coefficients and the mapping model, the tangential contact stiffness model can be constructed in combination with the tangential load time-varying characteristic model and the normal load time-varying characteristic model.

[0092] It can be understood that the contact stiffness is related to the elastic, elastoplastic and plastic deformations between the bolted joint surfaces. Therefore, based on the defined coefficients and mapping model, the tangential contact stiffness sub-model with different deformation characteristics can be constructed in combination with the tangential load time-varying characteristic model and the normal load time-varying characteristic model to obtain the tangential contact stiffness model.

[0093] In some embodiments of the present specification, the mapping model and the coefficients related to the geometric shape of each micro-protrusion can be expressed by the following formula:

[0094]

[0095] Among them, h can represent the height of a single microconvex body, h i can represent the height of a single micro-convex body of the i-th bolted joint surface in multiple bolted structures, D(t) can represent the fractal dimension of the bolted joint surface at time t, G(t) can represent the surface roughness of the bolted joint surface at time t, γ can represent the spectral density parameter, r can represent the radius of the micro-convex cross section, and λ can represent the coefficient related to the geometric shape of the micro-convex body.

[0096] In some embodiments of the present specification, the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model can be respectively expressed by the following formulas:

[0097]

[0098] Among them, K e (t) can represent the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) can represent the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) can represent the plastic tangential stiffness of the bolted structure at time t, D(t) can represent the fractal dimension of the bolted joint surface at time t, λ can represent the coefficient related to the geometric shape of the micro-convex body, G 1 and G 2 It can represent the shear modulus of the rough surface, υ 1 and 2 can represent the Poisson's ratio of the material of the bolted structure, ψ can represent the domain expansion factor, and a l It can represent the maximum cross-sectional area of ​​the microconvex body, a 1c It can represent the critical cross-sectional area where elastic deformation changes to elastic-plastic deformation, a 2c It can represent the critical cross-sectional area of ​​the transition from elastic-plastic deformation to plastic deformation, H g It can represent the coefficient related to the material and fractal parameters of the bolted structure, F τ (t) can represent the tangential load of the bolted structure at time t, F n(t) can represent the normal load of the bolted structure at time t, and μ can represent the friction coefficient.

[0099] In some embodiments of the present specification, the tangential contact stiffness model may be expressed by the following formula:

[0100]

[0101] Among them, K τ (t) can represent the tangential contact stiffness of the bolted structure at time t, K e (t) can represent the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) can represent the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) can represent the plastic tangential stiffness of the bolted structure at time t, a l It can represent the maximum cross-sectional area of ​​the microconvex body, a 1c It can represent the critical cross-sectional area where elastic deformation changes to elastic-plastic deformation, a 2c It can represent the critical cross-sectional area where elastic-plastic deformation transforms into plastic deformation.

[0102] S104: inputting the assembly time of the target bolted structure to be evaluated into the tangential contact stiffness model, calculating the tangential contact stiffness of the target bolted structure, and evaluating the target bolted structure based on the determined tangential contact stiffness.

[0103] Specifically, the assembly time can be substituted into the above formula (3) and formula (4) to obtain the tangential contact stiffness of the target bolted structure at the assembly time. Then, the accuracy and performance of the bolted structure can be calculated based on the calculated tangential contact stiffness to evaluate whether the target bolted structure meets the preset requirements and whether it will affect the entire machine.

[0104] In some embodiments of the present specification, after the tangential contact stiffness model is constructed, the accuracy and reliability of the model can be verified by experiment to achieve accurate prediction of the tangential contact stiffness of the bolted joint surface. Specifically, a hammer test can be used to verify the model.

[0105] The embodiments of this specification also provide a method for predicting the nonlinear evolution of the tangential contact stiffness of the bolted joint surface based on statistics and fractals. The method is further described below in conjunction with the accompanying drawings.

[0106] In this embodiment, six samples with the same processing parameters were trial-produced, one of which was used to conduct a bolted structure preload relaxation test and construct a preload relaxation model, and the other five were used to model the fractal dimension D(t) and surface roughness G(t). Figure 3As shown in FIG. 1 , the statistical and fractal-based prediction method for the nonlinear evolution of the tangential contact stiffness of the bolted joint surface can include the following steps:

[0107] S1. Construct a data-driven assembly preload relaxation model under vibration excitation.

[0108] The vibration condition was simulated on the fatigue tensile testing machine, and the preload force of the bolted structure at different times was recorded. The expression F(t)=(0.03603e -0.002362t +0.9639e -6.088E-7t )×60, which is the preload relaxation model of bolted structure.

[0109] S2. Establish the statistical equation of the time-varying law of fractal dimension D and surface roughness parameter G.

[0110] Specifically, the above step S2 may include the following steps:

[0111] S21. Process 5 samples under the same process parameters and use a 3D profilometer to obtain the following Figure 4 The microscopic topography data shown, the height of the microconvex body is defined as z 1 (x,y);

[0112] S22, calculate (F(0)-0.55σ s A) / N=(60-0.55*640*157 / 1000) / 5≈1kN bolt preload under step size, which is substituted into the bolted structure preload relaxation model, and the time corresponding to each stress is 0s, 258s, 1004s, 23855s, 52904s;

[0113] S23. Apply the calculated preload forces, i.e., 60 kN, 59 kN, 58 kN, 57 kN and 56 kN, to the five bolted structures;

[0114] S24, disassemble the bolted structure, measure and record the three-dimensional morphology of the joint surface under different preload forces, and record them as z 2 (x,y),z 3 (x,y), ..., z N (x,y);

[0115] S25. Calculate the fractal dimensions and surface roughness parameters corresponding to N groups of three-dimensional morphologies using the power spectral density method, and fit them into time-varying equations D(t) and G(t).

[0116] S3. Establish an analytical method to characterize the time-varying characteristics of tangential and normal loads.

[0117] Specifically, it can be based on Figure 5The refined finite element model of the bolted structure shown in the figure is used to simulate and analyze the time-varying characteristics of the tangential and normal loads on the joint surface under 60 kN, and the corresponding mathematical equation is established, namely, F τ (t) and F n (t).

[0118] S4. A three-dimensional fractal-based calculation method for the nonlinear evolution of tangential contact stiffness of bolted joints is proposed.

[0119] Specifically, the calculation method of the nonlinear evolution of tangential contact stiffness can introduce the time-varying characteristic equations of tangential and normal loads, as well as the fractal dimension D(t) and the surface roughness parameter G(t). The modeling process can specifically include:

[0120] S41, constructing a mapping relationship model between the height of a single micro-convex body and the fractal dimension D(t) and the surface roughness parameter G(t), and defining a coefficient λ related to the geometric shape parameter;

[0121] S42, establish elastic tangential contact stiffness K e (t), elastic-plastic tangential contact stiffness K ep (t) and plastic tangential contact stiffness K p (t) Model;

[0122] S43. Establish the tangential contact stiffness model of bolted joint surface under different conditions.

[0123] The model constructed here can refer to the above formulas (2) to (4), which will not be described in detail here.

[0124] The S50 test verifies this method to achieve accurate prediction of the tangential contact stiffness of bolted joints.

[0125] Hammer tests were carried out on five specimens with different preloads, and their first-order natural frequencies were collected and compared with the simulation analysis results. Figure 6 The curve in Figure 6 The effectiveness of the above method can be verified.

[0126] Based on the above-mentioned method for determining the tangential contact stiffness of the bolted joint surface, one or more embodiments of this specification also provide a device for determining the tangential contact stiffness of the bolted joint surface. The device may include a device (including a distributed system), software (application), module, plug-in, server, client, etc. that uses the method described in the embodiments of this specification and is combined with necessary implementation hardware. Based on the same innovative concept, the device in one or more embodiments provided in the embodiments of this specification is as described in the following embodiments. Since the implementation scheme and method of the device to solve the problem are similar, the implementation of the specific device in the embodiments of this specification can refer to the implementation of the aforementioned method, and the repetitions will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived. Figure 7 FIG. 1 is a schematic diagram of a device for determining the tangential contact stiffness of a bolted joint surface provided in an embodiment of the present application. Figure 7 As shown, the device 700 for determining the tangential contact stiffness of the bolted joint surface may include:

[0127] The first modeling module 701 is used to construct a preload relaxation model, wherein the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time.

[0128] The second modeling module 702 is used to construct a fractal dimension model and a surface roughness model of the bolted joint surface based on the preload relaxation model. The fractal dimension model and the surface roughness model are used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and the time variation.

[0129] The third modeling module 703 is used to construct a tangential contact stiffness model of the bolted joint surface in which the tangential contact stiffness varies with time based on the preload relaxation model, the fractal dimension model and the surface roughness model.

[0130] The calculation module 704 is used to input the assembly time of the target bolted structure to be evaluated into the tangential contact stiffness model, calculate the tangential contact stiffness of the target bolted structure, and evaluate the target bolted structure based on the determined tangential contact stiffness.

[0131] In some embodiments of the present specification, the first modeling module 701 can be specifically used to: simulate vibration conditions and record preload relaxation data of the bolted structure at different times; and fit the preload relaxation model based on the preload relaxation data and the corresponding time.

[0132] In some embodiments of the present specification, the preload relaxation model can be expressed by the following formula:

[0133] F(t)=(ae bt +ce dt )F(0);

[0134] Among them, F(t) can represent the preload force of the bolted structure at time t, F(0) can represent the preload force of the bolted structure at the initial time, and a, b, c, and d can represent coefficients.

[0135] In some embodiments of the present specification, the second modeling module 702 can be specifically used to: obtain microscopic morphology data of the bonding surfaces of multiple bolted structures at the initial moment as initial microscopic morphology data; determine the preload simulation step and preload simulation range corresponding to each bolted structure; determine multiple simulated preloads and corresponding simulation times corresponding to each bolted structure based on the preload relaxation model and the preload simulation step and preload simulation range corresponding to each bolted structure; obtain simulated microscopic morphology data of the bonding surfaces of each bolted structure under the corresponding multiple simulated preloads and simulation times; determine the fractal dimension data and surface roughness data corresponding to each bolted structure at different simulation times based on the initial microscopic morphology data and simulated microscopic morphology data of multiple bolted structures; and construct the fractal dimension model and the surface roughness model respectively based on the fractal dimension data and surface roughness data of each bolted structure at multiple simulation times.

[0136] In some embodiments of the present specification, the third modeling module 703 constructs a tangential contact stiffness model of the bolted joint surface in which the tangential contact stiffness varies with time based on the preload relaxation model, the fractal dimension model and the surface roughness model, which may include: constructing a tangential load time-varying characteristic model and a normal load time-varying characteristic model of the bolted joint surface based on the preload relaxation model; constructing the tangential contact stiffness model based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model.

[0137] In some embodiments of the present specification, the third modeling module 703 constructs the tangential contact stiffness model based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model, and can be specifically used for: constructing a mapping model between each micro-protrusion on the bolted joint surface and the fractal dimension and surface roughness based on the fractal dimension model and the surface roughness model, and defining coefficients related to the geometric shape of each micro-protrusion; constructing an elastic tangential contact stiffness sub-model, an elastic-plastic tangential contact stiffness sub-model and a plastic tangential stiffness sub-model based on the mapping model, the defined coefficients, the tangential load time-varying characteristic model and the normal load time-varying characteristic model; constructing the tangential contact stiffness model based on the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model and the plastic tangential stiffness sub-model.

[0138] In some embodiments of the present specification, the mapping model and the coefficients related to the geometric shape of each micro-protrusion can be expressed by the following formula:

[0139]

[0140] Among them, h can represent the height of a single microconvex body, h i can represent the height of a single micro-convex body of the i-th bolted joint surface in multiple bolted structures, D(t) can represent the fractal dimension of the bolted joint surface at time t, G(t) can represent the surface roughness of the bolted joint surface at time t, γ can represent the spectral density parameter, r can represent the radius of the micro-convex cross section, and λ can represent the coefficient related to the geometric shape of the micro-convex body.

[0141] In some embodiments of the present specification, the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model can be respectively expressed by the following formulas:

[0142]

[0143] Among them, K e (t) can represent the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) can represent the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) can represent the plastic tangential stiffness of the bolted structure at time t, D(t) can represent the fractal dimension of the bolted joint surface at time t, λ can represent the coefficient related to the geometric shape of the micro-convex body, G 1 and G 2 It can represent the shear modulus of the rough surface, υ 1 and 2can represent the Poisson's ratio of the material of the bolted structure, ψ can represent the domain expansion factor, and a l It can represent the maximum cross-sectional area of ​​the microconvex body, a 1c It can represent the critical cross-sectional area where elastic deformation changes to elastic-plastic deformation, a 2c It can represent the critical cross-sectional area of ​​the transition from elastic-plastic deformation to plastic deformation, H g It can represent the coefficient related to the material and fractal parameters of the bolted structure, F τ (t) can represent the tangential load of the bolted structure at time t, F n (t) can represent the normal load of the bolted structure at time t, and μ can represent the friction coefficient.

[0144] In some embodiments of the present specification, the tangential contact stiffness model may be expressed by the following formula:

[0145]

[0146] Among them, K τ (t) can represent the tangential contact stiffness of the bolted structure at time t, K e (t) can represent the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) can represent the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) can represent the plastic tangential stiffness of the bolted structure at time t, a l It can represent the maximum cross-sectional area of ​​the microconvex body, a 1c It can represent the critical cross-sectional area where elastic deformation changes to elastic-plastic deformation, a 2c It can represent the critical cross-sectional area where elastic-plastic deformation transforms into plastic deformation.

[0147] The description and functions of the above modules can be understood by referring to the content of the method for determining the tangential contact stiffness of the bolted joint surface, which will not be repeated here.

[0148] The present application also provides an electronic device, such as Figure 8 As shown, the electronic device may include a processor 801 and a memory 802, wherein the processor 801 and the memory 802 may be connected via a bus or other means. Figure 8 The example of connecting through bus is taken in the following.

[0149] The processor 801 may be a central processing unit (CPU). The processor 801 may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or a combination of the above chips.

[0150] The memory 802 is a non-transitory computer-readable storage medium that can be used to store non-transitory software programs, non-transitory computer executable programs and modules, such as the program instructions / modules corresponding to the method for determining the tangential contact stiffness of the bolted joint surface in the embodiment of the present invention (for example, Figure 7 The processor 801 executes various functional applications and data processing of the processor by running the non-transient software programs, instructions and modules stored in the memory 802, that is, the method for determining the tangential contact stiffness of the bolted joint surface in the above method embodiment is implemented.

[0151] The memory 802 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required by at least one function; the data storage area may store data created by the processor 801, etc. In addition, the memory 802 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 802 may optionally include a memory remotely arranged relative to the processor 801, and these remote memories may be connected to the processor 801 via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0152] The one or more modules are stored in the memory 802, and when executed by the processor 801, the following method for determining the tangential contact stiffness of the bolted joint surface is performed:

[0153] A preload relaxation model is constructed, and the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time. A fractal dimension model and a surface roughness model of the bolted joint surface are constructed based on the preload relaxation model, and the fractal dimension model and the surface roughness model are respectively used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and time. A tangential contact stiffness model is constructed based on the preload relaxation model, the fractal dimension model and the surface roughness model, and the tangential contact stiffness of the bolted joint surface changes with time. The assembly time of the target bolted structure to be evaluated is input into the tangential contact stiffness model, and the tangential contact stiffness of the target bolted structure is calculated, so as to evaluate the target bolted structure based on the determined tangential contact stiffness.

[0154] The specific details of the above electronic device can be understood by referring to the corresponding descriptions and effects in the above method embodiments, and will not be repeated here.

[0155] The present specification also provides a computer storage medium, wherein the computer storage medium stores computer program instructions, and when the computer program instructions are executed, the steps of the method for determining the tangential contact stiffness of the bolted joint surface are implemented.

[0156] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, the storage medium can be a disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (HDD) or a solid-state drive (SSD), etc.; the storage medium can also include a combination of the above-mentioned types of memory.

[0157] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0158] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions.

[0159] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0160] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute certain parts of the methods of each implementation method of the present application.

[0161] The present application can be used in many general or special computer system environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc.

[0162] The present application may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media, including storage devices.

[0163] Although the present application has been described through embodiments, those skilled in the art will appreciate that there are many modifications and variations to the present application without departing from the spirit of the present application, and it is intended that the appended claims include these modifications and variations without departing from the spirit of the present application.

Claims

1. A method for determining the tangential contact stiffness of a bolted joint surface, characterized in that: include: Constructing a preload relaxation model, wherein the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time; Based on the preload relaxation model, a fractal dimension model and a surface roughness model of the bolted joint surface are constructed, wherein the fractal dimension model and the surface roughness model are used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and the time variation; Based on the preload relaxation model, the fractal dimension model and the surface roughness model, a tangential contact stiffness model of the bolted joint surface that varies with time is constructed; The assembly time of the target bolted structure to be evaluated is input into the tangential contact stiffness model, and the tangential contact stiffness of the target bolted structure is calculated to evaluate the target bolted structure based on the determined tangential contact stiffness.

2. The method for determining the tangential contact stiffness of a bolted joint surface according to claim 1, characterized in that: Construct a preload relaxation model, including: Simulate vibration conditions and record the preload relaxation data of bolted structures at different times; The preload relaxation model is obtained by fitting based on the preload relaxation data and the corresponding time.

3. The method for determining the tangential contact stiffness of a bolted joint according to claim 1, characterized in that: Based on the preload relaxation model, a fractal dimension model and a surface roughness model of the bolted joint surface are constructed, including: Acquiring microscopic morphology data of the bonding surfaces of the plurality of bolted structures at the initial moment as initial microscopic morphology data; Determine the preload simulation step length and preload simulation range corresponding to each bolted structure; Based on the preload relaxation model and the preload simulation step length and preload simulation range corresponding to each bolted structure, a plurality of simulated preloads and corresponding simulation times corresponding to each bolted structure are determined; Acquire simulated microscopic morphology data of the joint surface of each bolted structure under corresponding multiple simulated preloads and simulated times; Based on the initial micro-morphology data and simulated micro-morphology data of multiple bolted structures, the fractal dimension data and surface roughness data corresponding to each bolted structure at different simulation times are determined; The fractal dimension model and the surface roughness model are respectively constructed based on the fractal dimension data and the surface roughness data of each bolted structure at multiple simulation times.

4. The method for determining the tangential contact stiffness of a bolted joint according to claim 1, characterized in that: Based on the preload relaxation model, the fractal dimension model and the surface roughness model, a tangential contact stiffness model of the bolted joint surface that varies with time is constructed, including: Based on the preload relaxation model, a tangential load time-varying characteristic model and a normal load time-varying characteristic model of the bolted joint surface are constructed; The tangential contact stiffness model is constructed based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model.

5. The method for determining the tangential contact stiffness of the bolted joint surface according to claim 4, characterized in that: Based on the tangential load time-varying characteristic model, the normal load time-varying characteristic model, the fractal dimension model and the surface roughness model, the tangential contact stiffness model is constructed, including: Based on the fractal dimension model and the surface roughness model, a mapping model between each micro-convex body on the bolted joint surface and the fractal dimension and the surface roughness is constructed, and a coefficient related to the geometric shape of each micro-convex body is defined; Based on the mapping model, the defined coefficients, the tangential load time-varying characteristic model and the normal load time-varying characteristic model, an elastic tangential contact stiffness sub-model, an elastic-plastic tangential contact stiffness sub-model and a plastic tangential stiffness sub-model are constructed; The tangential contact stiffness model is constructed based on the elastic tangential contact stiffness sub-model, the elastoplastic tangential contact stiffness sub-model and the plastic tangential stiffness sub-model.

6. The method for determining the tangential contact stiffness of a bolted joint surface according to claim 5, characterized in that: The mapping model and the coefficients associated with the geometry of each asperity are expressed by the following formula: Where h represents the height of a single microconvex body, h i represents the height of a single micro-convex body of the i-th bolted joint surface in multiple bolted structures, D(t) represents the fractal dimension of the bolted joint surface at time t, G(t) represents the surface roughness of the bolted joint surface at time t, γ represents the spectral density parameter, r represents the radius of the micro-convex cross section, and λ represents the coefficient related to the geometric shape of the micro-convex body.

7. The method for determining the tangential contact stiffness of a bolted joint according to claim 5, characterized in that: The elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model and the plastic tangential stiffness sub-model are respectively expressed by the following formulas: K p (t)=0 Among them, K e (t) represents the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) represents the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) represents the plastic tangential stiffness of the bolted structure at time t, D(t) represents the fractal dimension of the bolted joint surface at time t, λ represents the coefficient related to the geometric shape of the micro-asperity, G1 and G2 represent the shear modulus of the rough surface, υ1 and υ2 represent the Poisson's ratio of the material of the bolted structure, ψ represents the domain expansion factor, and a l represents the maximum cross-sectional area of ​​the microconvex body, a 1c The critical cross-sectional area for the transition from elastic deformation to elastic-plastic deformation, a 2c The critical cross-sectional area for the transition from elastic-plastic deformation to plastic deformation, H g represents the coefficient related to the material and fractal parameters of the bolted structure, F τ (t) represents the tangential load of the bolted structure at time t, F n (t) represents the normal load of the bolted structure at time t, and μ represents the friction coefficient.

8. The method for determining the tangential contact stiffness of a bolted joint surface according to claim 5, characterized in that: The tangential contact stiffness model is expressed by the following formula: Among them, K τ (t) represents the tangential contact stiffness of the bolted structure at time t, K e (t) represents the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) represents the elastic-plastic tangential contact stiffness of the bolted structure at time t, K p (t) represents the plastic tangential stiffness of the bolted structure at time t, a l represents the maximum cross-sectional area of ​​the microconvex body, a 1c The critical cross-sectional area for the transition from elastic deformation to elastic-plastic deformation, a 2c It represents the critical cross-sectional area where elastic-plastic deformation transforms into plastic deformation.

9. A device for determining the tangential contact stiffness of a bolted joint surface, characterized in that: include: A first modeling module is used to construct a preload relaxation model, wherein the preload relaxation model is used to characterize the relationship between the preload of the bolted structure and time; A second modeling module is used to construct a fractal dimension model and a surface roughness model of the bolted joint surface based on the preload relaxation model, wherein the fractal dimension model and the surface roughness model are used to characterize the relationship between the fractal dimension and the surface roughness of the bolted structure and the time variation; A third modeling module is used to construct a tangential contact stiffness model of the bolted joint surface in which the tangential contact stiffness varies with time based on the preload relaxation model, the fractal dimension model and the surface roughness model; The calculation module is used to input the assembly time of the target bolted structure to be evaluated into the tangential contact stiffness model, calculate the tangential contact stiffness of the target bolted structure, and evaluate the target bolted structure based on the determined tangential contact stiffness.

10. An electronic device, characterized in that: include: A memory and a processor, wherein the processor and the memory are communicatively connected to each other, the memory stores computer instructions, and the processor implements the steps of the method according to any one of claims 1 to 8 by executing the computer instructions.

Images