Determination Method, Device and Equipment for Tangential Contact Stiffness of Bolted Joint Interface

Abstract

The present application discloses a method, device and equipment for determining the tangential contact stiffness of a bolted joint surface. The method includes: constructing a preload relaxation model that characterizes the relationship between the preload of the bolted structure and time; respectively constructing a fractal dimension model and a surface roughness model that characterize the relationship between the fractal dimension and surface roughness of the bolted joint surface and time based on the preload relaxation model; constructing a tangential contact stiffness model that characterizes the change of the tangential contact stiffness of the bolted joint surface with time based on the preload relaxation model, the fractal dimension model and the surface roughness model; inputting the assembly time of the target bolted structure to be evaluated into the tangential contact stiffness model, and calculating the tangential contact stiffness of the target bolted structure, so as to evaluate the target bolted structure based on the determined tangential contact stiffness. Through the above method, the tangential contact stiffness of the bolted joint surface can be calculated more accurately and reliably, providing a basis for the accurate prediction of the time-varying characteristics 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 particularly relates 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 in construction machinery, and the contact stiffness of its joint surface is crucial for ensuring the dynamic characteristics and service reliability of the whole machine. As a 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, and its assembly pre-tightening force and surface roughness are the main factors affecting the contact stiffness of the joint surface.

[0003] At present, a large number of studies have been carried out on the contact stiffness of bolted joint surfaces, and statistical, fractal, and multi-scale models for calculating contact stiffness have been proposed. These models can be used to predict the contact stiffness of bolted joint surfaces under quasi-static or slow operating speeds, but cannot accurately predict the contact characteristics under moving conditions. The assembly pre-tightening force and the surface roughness under its action inevitably change with time, resulting in a decrease in the contact stiffness of the joint surface, making it difficult to meet the requirements of the dynamic characteristics and service reliability of the whole machine. The long-term dynamic characteristic monitoring based on experimental testing is costly and not easy 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 the normal load, and the modeling process is more complex.

[0004] For the problems of high cost and difficulty in tracking the dynamic characteristics test of the above complex mechanical products, no effective solution has been found yet. 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 to solve the problems of high cost and difficulty in tracking the dynamic characteristics test of complex mechanical products.

[0006] 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, including:

[0007] Construct a pre-tightening force relaxation model, which is used to characterize the change relationship of the pre-tightening force of the bolted structure with time;

[0008] Based on the pre-tightening force relaxation model, construct a fractal dimension model and a surface roughness model of the bolted joint surface. The fractal dimension model and the surface roughness model are respectively used to characterize the change relationships of the fractal dimension and the surface roughness of the bolted structure with time;

[0009] Based on the pre-tightening force relaxation model, the fractal dimension model, and the surface roughness model, a tangential contact stiffness model for the bolted joint surface that changes with time is constructed.

[0010] 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.

[0011] In some embodiments of the present specification, constructing a pre-tightening force relaxation model includes:

[0012] Simulate the vibration condition and record the pre-tightening force relaxation data of the bolted structure at different times.

[0013] Based on the pre-tightening force relaxation data and the corresponding time, fit to obtain the pre-tightening force relaxation model.

[0014] In some embodiments of the present specification, based on the pre-tightening force relaxation model, constructing a fractal dimension model and a surface roughness model for the bolted joint surface includes:

[0015] Obtain the microscopic morphology data of the joint surface of multiple bolted structures at the initial moment as the initial microscopic morphology data.

[0016] Determine the pre-tightening force simulation step size and the pre-tightening force simulation range corresponding to each bolted structure.

[0017] Based on the pre-tightening force relaxation model, the pre-tightening force simulation step size, and the pre-tightening force simulation range corresponding to each bolted structure, determine the multiple simulated pre-tightening forces and the corresponding simulated times corresponding to each bolted structure.

[0018] Obtain the simulated microscopic morphology data of the joint surface of each bolted structure under the corresponding multiple simulated pre-tightening forces and simulated times.

[0019] Based on the initial microscopic morphology data and the simulated microscopic morphology data of multiple bolted structures, determine the fractal dimension data and the surface roughness data corresponding to each bolted structure at different simulated times.

[0020] Based on the fractal dimension data and the surface roughness data of each bolted structure at multiple simulated times, construct the fractal dimension model and the surface roughness model respectively.

[0021] In some embodiments of the present specification, based on the pre-tightening force relaxation model, the fractal dimension model, and the surface roughness model, constructing a tangential contact stiffness model for the bolted joint surface that changes with time includes:

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

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

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

[0025] Based on the fractal dimension model and the surface roughness model, a mapping model of each micro-convex body on the bolted joint surface with 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 coefficient, the time-varying characteristic model of the tangential load, and the time-varying characteristic model of the normal load, 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] Based on the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model, the tangential contact stiffness model is constructed.

[0028] In some embodiments of the present specification, the mapping model and the coefficient related to the geometric shape of each micro-convex body are represented by the following formula:

[0029]

[0030] where h represents the height of a single micro-convex body, h i represents the height of a single micro-convex body of the i-th bolted joint surface among 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 cross-section of the micro-convex body, 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 represented by the following formula:

[0032]

[0033] where K e (t) represents the elastic tangential contact stiffness of the bolted structure at time t, K ep(t) represents the elastoplastic tangential contact stiffness of the bolted connection structure at time t, K p (t) represents the plastic tangential stiffness of the bolted connection 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 asperities, G1 and G2 represent the shear moduli of the rough surfaces, υ1 and υ2 represent the Poisson's ratios of the materials of the bolted connection structure, ψ represents the domain expansion factor, a l represents the maximum cross-sectional area of the asperity, a 1c represents the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c represents the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation, H g represents the coefficient related to the material and fractal parameters of the bolted connection structure, F τ (t) represents the tangential load of the bolted connection structure at time t, F n (t) represents the normal load of the bolted connection structure at time t, μ represents the friction coefficient.

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

[0035]

[0036] where, K τ (t) represents the tangential contact stiffness of the bolted connection structure at time t, K e (t) represents the elastic tangential contact stiffness of the bolted connection structure at time t, K ep (t) represents the elastoplastic tangential contact stiffness of the bolted connection structure at time t, K p (t) represents the plastic tangential stiffness of the bolted connection structure at time t, a l represents the maximum cross-sectional area of the asperity, a 1c represents the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c represents the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation.

[0037] The second aspect of this specification provides a device for determining the tangential contact stiffness of a bolted joint surface, including:

[0038] A first modeling module for constructing a pre-tightening force relaxation model, which is used to characterize the change relationship of the pre-tightening force of the bolted connection structure with time;

[0039] A second modeling module for constructing a fractal dimension model and a surface roughness model of the bolted joint surface based on the pre-tightening force relaxation model, where the fractal dimension model and the surface roughness model are respectively used to characterize the change relationships of the fractal dimension and the surface roughness of the bolted connection structure with time;

[0040] A third modeling module, configured to construct a tangential contact stiffness model of the bolted joint surface varying with time based on the pre-tightening force relaxation model, the fractal dimension model, and the surface roughness model;

[0041] A calculation module, configured 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] A third aspect of this specification provides an electronic device, including: a memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor realizes the steps of the method described in the first aspect by executing the computer instructions.

[0043] In the method, apparatus, and device for determining the tangential contact stiffness of a bolted joint surface provided in the embodiments of this specification, a pre-tightening force relaxation model for characterizing the variation relationship of the pre-tightening force of the bolted structure with time is constructed; a fractal dimension model and a surface roughness model for respectively characterizing the variation relationships of the fractal dimension and the surface roughness of the bolted joint surface with time are constructed based on the pre-tightening force relaxation model; a tangential contact stiffness model of the bolted joint surface varying with time is constructed based on the pre-tightening force relaxation model, the fractal dimension model, and the surface roughness model; 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. By the above method, the variation characteristics of the pre-tightening force of the bolted structure with time are considered when constructing the component pre-tightening force relaxation model, and further, the fractal dimension model and the surface roughness model constructed based on the pre-tightening force relaxation model also consider the variation characteristics of the fractal dimension and the surface roughness with time. Furthermore, the tangential stiffness model constructed on this basis can also consider the influence of the time-varying characteristics of the assembly pre-tightening force, the fractal dimension, and 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 characteristic test period and high cost, and provide a basis for accurately predicting the time-varying characteristics of the overall machine dynamic performance. Description of the Drawings

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1 The figure shows a schematic diagram of a method for determining the tangential contact stiffness of a bolted joint surface provided by an embodiment of this specification;

[0046] Figure 2 The figure shows a schematic diagram of a method for constructing a fractal dimension model and the surface roughness model provided by an embodiment of this specification;

[0047] Figure 3 The figure shows a schematic diagram of a method for predicting the non - linear evolution of the tangential contact stiffness of a bolted joint surface based on statistics and fractals provided by an embodiment of this specification;

[0048] Figure 4 The figure shows a schematic diagram of the three - dimensional microscopic morphology of a bolted joint surface provided by an embodiment of this specification;

[0049] Figure 5 The figure shows a schematic diagram of a refined finite - element model of a bolted structure provided by an embodiment of this specification;

[0050] Figure 6 The figure shows a schematic diagram of a comparison of the time - varying curve of the first - order natural frequency considering the tangential contact stiffness provided by an embodiment of this specification;

[0051] Figure 7 The figure shows a schematic diagram of a device for determining the tangential contact stiffness of a bolted joint surface provided by an embodiment of this specification;

[0052] Figure 8 The figure shows a schematic diagram of an electronic device provided by an embodiment of this specification. Detailed implementation manners

[0053] In order to enable those skilled in the art to better understand the technical solutions in this application, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0054] As described above, at present, the contact stiffness model of bolted joint surfaces can only be used to predict the contact stiffness of bolted joint surfaces under quasi - static or slow operating speeds, but cannot accurately predict the contact characteristics under moving conditions. The long - term dynamic characteristic monitoring based on experimental tests has high costs and is not easy to operate.

[0055] To solve the above problems, an embodiment of this specification provides a method for determining the tangential contact stiffness of a bolted joint surface. When considering the component pre-tightening force relaxation model, the time-varying characteristics of the pre-tightening force of the bolted structure are taken into account. Furthermore, the fractal dimension model and the surface roughness model constructed based on the pre-tightening force relaxation model also consider the time-varying characteristics of the fractal dimension and the surface roughness. Further, the tangential stiffness model constructed on this basis can also consider the influence of the time-varying characteristics of the assembly pre-tightening force, the fractal dimension, and 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 characteristic test cycles and high costs, and provide a basis for the accurate prediction of the time-varying characteristics of the overall machine's dynamic performance.

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

[0057] First, the method for determining the tangential contact stiffness of a bolted joint surface provided in an embodiment of this application will be introduced with reference to the accompanying drawings.

[0058] Figure 1 Shown is a schematic diagram of the method for determining the tangential contact stiffness of a bolted joint surface 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, based on routine or non-creative labor, more or fewer operation steps or module units may be included in the method or device. In steps or structures where there is no necessary causal relationship logically, 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 is applied to an actual device, server, or terminal product, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or drawings (for example, in an environment of parallel processors or multi-threaded processing, and even including an implementation environment of distributed processing and server clusters). As Figure 1 Shown, the method may include:

[0059] S101: Construct a pre-tightening force relaxation model, where the pre-tightening force relaxation model is used to characterize the change relationship of the pre-tightening force of the bolted structure over time.

[0060] It can be understood that after the bolted structure is fastened, the pre-tightening force will decrease with time under the influence of excitations such as vibration, that is, the pre-tightening force relaxes. Specifically, the pre-tightening force relaxation data at different times can be obtained by simulating vibration excitation, and the pre-tightening force relaxation model can be constructed.

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

[0062] Among them, the vibration condition can be simulated by devices such as a fatigue tensile testing machine, and the pre-tightening force relaxation data and its corresponding times can be obtained through simulation, and the relationship between the pre-tightening force and time can be fitted to obtain the pre-tightening force relaxation model.

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

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

[0065] Among them, F(t) can represent the pre-tightening force of the bolted structure at time t, F(0) can represent the pre-tightening force of the bolted structure at the initial time, and a, b, c, d can represent coefficients.

[0066] It can be understood that the above relationship between the pre-tightening force and time in exponential form can be a mapping relationship between the pre-tightening force and time obtained by fitting in the embodiments of the present specification. In other embodiments, the pre-tightening force relaxation model can also be characterized as other forms of model structures, and the present application does not limit this.

[0067] S102: Construct a fractal dimension model and a surface roughness model of the bolted joint surface based on the pre-tightening force relaxation model, and the fractal dimension model and the surface roughness model are respectively used to characterize the change relationship of the fractal dimension and the surface roughness of the bolted structure with time.

[0068] It can be understood that the calculation of the fractal dimension and the surface roughness can be based on 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 pre-tightening force. And because the pre-tightening force has time-varying characteristics, the fractal dimension model and the surface roughness model can be constructed based on the constructed pre-tightening force relaxation model.

[0069] Specifically, since the relationship between the pre-tightening force and time in the pre-tightening force relaxation model is a continuous change 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 pre-tightening force relaxation model to determine the pre-tightening force and time corresponding to each point, and experimental simulations can be carried out. The microscopic three-dimensional morphology of the bolted joint surface under the pre-tightening force corresponding to each point can be measured and recorded. Then, based on the recorded microscopic three-dimensional morphology and the corresponding time of the pre-tightening force, a fractal dimension model of the relationship between the fractal dimension and time and a surface roughness model of the relationship between the surface roughness and time are constructed to reflect the time-varying characteristics of the fractal dimension and the surface roughness.

[0070] Reference Figure 2 As shown, in some embodiments of the present specification, constructing a fractal dimension model and a surface roughness model of the bolted joint surface based on the pre-tightening force relaxation model may include:

[0071] S201: Obtain the microscopic morphology data of the joint surface of multiple bolted structures at the initial moment as the initial microscopic morphology data.

[0072] It can be understood that the multiple bolted structures can be multiple specimens processed under the same process parameters, or multiple specimens processed under the condition that some process parameters are the same. For the processed bolted structures, a three-dimensional microscopic morphology instrument can be used to obtain the microscopic morphology data of their joint surfaces as the initial microscopic morphology data. That is, the initial moment is the moment when the bolted structure is not assembled with the pre-tightening force, and the initial microscopic morphology data can be understood as the three-dimensional morphology data of the bolted joint surface without the assembled pre-tightening force, which can be denoted as z1(x, y).

[0073] S202: Determine the pre-tightening force simulation step size and the pre-tightening force simulation range corresponding to each bolted structure.

[0074] It can be understood that the pre-tightening force simulation step size can characterize the step size between multiple pre-tightening forces used when simulating the simulated microscopic morphology data, and the pre-tightening force simulation range can be used to characterize the value range of multiple pre-tightening forces, which can include the upper limit and the lower limit of the value.

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

[0076] In some embodiments of the present specification, the pre-tightening force simulation step size can be calculated by the formula (F(0) - 0.55σ sA) / N is determined. Among them, F(0) can represent the pre-tightening force of the bolted structure at the initial moment, σ s 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 pre-tightening force simulation range can be based on (0.55 - F(0) / σ s A) times the yield strength σ s of the bolt material. That is, it can be within the range of (0.55 - F(0) / σ s A) times the yield strength σ s of the bolt material. Calculate multiple pre-tightening forces and their corresponding times at the step of (F(0) - 0.55σ s A) / N. Among them, the time corresponding to the pre-tightening force can substitute multiple simulated pre-tightening forces determined based on the pre-tightening force simulation step and the pre-tightening force simulation range into the constructed pre-tightening force relaxation model to obtain the simulated time corresponding to each pre-tightening force.

[0077] S203: Based on the pre-tightening force relaxation model, the pre-tightening force simulation step corresponding to each bolted structure, and the pre-tightening force simulation range, determine multiple simulated pre-tightening forces and corresponding simulated times corresponding to each bolted structure.

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

[0079] S204: Obtain the simulated microscopic topography data of the joint surface of each bolted structure under the corresponding multiple simulated pre-tightening forces and simulated times.

[0080] Specifically, the multiple simulated pre-tightening forces corresponding to each bolted structure can be sequentially loaded on the corresponding bolted structure, and then the bolted structure is disassembled, and the three-dimensional topography data of the bolted joint surface under different simulated pre-tightening forces is measured and recorded. The simulated microscopic three-dimensional topography data of each bolted structure can be respectively recorded as z2(x, y), z3(x, y), ……, z N (x, y).

[0081] S205: Based on the initial microscopic topography data and the simulated microscopic topography data of multiple bolted structures, determine the fractal dimension data and surface roughness data corresponding to each bolted structure at different simulated times.

[0082] Specifically, based on the initial microscopic morphology data and the simulated microscopic morphology data, combined with the mapping relationship between the fractal dimension and the microscopic morphology and the mapping relationship between the surface roughness and the microscopic morphology, the fractal dimension data and the surface roughness data corresponding to each microscopic morphology data can be calculated respectively. The fractal dimension data and the surface roughness data can be denoted as D(t1), D(t2), …, D(t N ) and G(t1), G(t2), …, G(t N ).

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

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

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

[0086] S103: Based on the preload relaxation model, the fractal dimension model, and the surface roughness model, construct a tangential contact stiffness model for the bolted joint surface that changes with time.

[0087] It can be understood that the tangential contact stiffness is affected by the preload, the fractal dimension, and the 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 constructed based on this.

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

[0089] Further, based on the refined finite element model simulation analysis of the bolted connection structure, the time-varying characteristics of the tangential load and the normal load on the bolted joint surface under the action of the pre-tightening force F(t) can be analyzed, and 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. Among them, the tangential load at time t can be expressed as F τ (t), and 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 time-varying characteristic model of the tangential load, the time-varying characteristic model of the normal load, the fractal dimension model, and the surface roughness model may include: constructing a mapping model of each micro-protrusion on the bolted joint surface with the fractal dimension and the surface roughness based on the fractal dimension model and the surface roughness model, and defining a coefficient 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 coefficient, the time-varying characteristic model of the tangential load, and the time-varying characteristic model of the normal load; 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 macroscopically, while it is a surface composed of multiple micro-protrusions microscopically. Therefore, before constructing the tangential contact stiffness model, a mapping model of each micro-protrusion with the fractal dimension and the surface roughness can be constructed based on the fractal dimension model and the surface roughness model, and a coefficient related to the geometric shape of each micro-protrusion can be defined. Furthermore, the tangential contact stiffness model can be constructed based on the defined coefficient and the mapping model, combined with the time-varying characteristic model of the tangential load and the time-varying characteristic model of the normal load.

[0092] It can be understood that the contact stiffness is related to the elastic, elastic-plastic, and plastic deformations between the bolted joint surfaces. Therefore, different tangential contact stiffness sub-models with different deformation characteristics can be constructed based on the defined coefficient and the mapping model, combined with the time-varying characteristic model of the tangential load and the time-varying characteristic model of the normal load, and then the tangential contact stiffness model can be obtained.

[0093] In some embodiments of the present specification, the mapping model and the coefficient 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 micro-protrusion, h iThe height of a single asperity that can represent the i-th bolted joint surface among 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 cross-section of the asperity, and λ can represent the coefficient related to the geometric shape of the asperity.

[0096] In some embodiments of the present specification, the elastic tangential contact stiffness sub-model, the elastoplastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model can be respectively represented 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 elastoplastic 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 asperity, G1 and G2 can represent the shear modulus of the rough surface, υ1 and υ2 can represent the Poisson's ratio of the material of the bolted structure, ψ can represent the domain expansion factor, a l can represent the maximum cross-sectional area of the asperity, a 1c can represent the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c can represent the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation, H g 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 can be represented 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 elastoplastic 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 lIt can represent the maximum cross-sectional area of the asperity, a 1c It can represent the critical cross-sectional area at which elastic deformation transitions to elastoplastic deformation, a 2c It can represent the critical cross-sectional area at which elastoplastic deformation transitions to plastic deformation.

[0102] S104: 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.

[0103] Specifically, the assembly time can be substituted into the above formulas (3) and (4) to obtain the tangential contact stiffness of the target bolted structure at this assembly time. Furthermore, the accuracy, performance, etc. 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 this specification, after constructing the tangential contact stiffness model, the accuracy and reliability of the model can be verified through experiments to achieve accurate prediction of the tangential contact stiffness of the bolted joint surface. Specifically, a hammering experiment can be used for model verification.

[0105] This specification embodiment also provides a non-linear evolution prediction method for the tangential contact stiffness of bolted joint surfaces based on statistics and fractals. This method will be further described below with reference to the accompanying drawings.

[0106] In this embodiment, 6 specimens with the same processing parameters are trial-produced. Among them, 1 specimen is used for the pre-tightening force relaxation test of the bolted structure and a pre-tightening force relaxation model is constructed, and the other 5 specimens are used for modeling the fractal dimension D(t) and surface roughness G(t). Refer to Figure 3 As shown, the non-linear evolution prediction method for the tangential contact stiffness of bolted joint surfaces based on statistics and fractals can include the following steps:

[0107] S1: Construct a data-driven assembly pre-tightening force relaxation model under vibration excitation.

[0108] Simulate the vibration condition on a fatigue tensile testing machine, record the pre-tightening force of the bolted structure at different times, and fit it into an expression in software as F(t)=(0.03603e -0.002362t +0.9639e -6.088E-7t )×60, which is the pre-tightening force relaxation model of the bolted structure.

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

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

[0111] S21. Machine 5 specimens under the same process parameters, and use a three-dimensional profiler to obtain the microscopic topography data as shown in Figure 4 . Define the height of the micro-protrusion as z1(x,y);

[0112] S22. Calculate the bolt pre-tightening force at a step of 1 kN for (F(0) - 0.55σ s A) / N = (60 - 0.55 * 640 * 157 / 1000) / 5 ≈ 1 kN. Substitute it into the pre-tightening force relaxation model of the bolted structure to obtain the corresponding times for each stress as 0 s, 258 s, 1004 s, 23855 s, and 52904 s;

[0113] S23. Apply the calculated pre-tightening forces, namely 60 kN, 59 kN, 58 kN, 57 kN, and 56 kN, to 5 bolted structures;

[0114] S24. Disassemble the bolted structure, measure and record the three-dimensional topography of the joint surface under different pre-tightening forces, denoted as z2(x,y), z3(x,y), ……, z N (x,y);

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

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

[0117] Specifically, based on the Figure 5 refined finite element model of the bolted structure shown, simulate and analyze the time-varying characteristics of the tangential and normal loads on the joint surface under 60 kN, and establish the corresponding mathematical equations, namely F τ (t) and F n (t).

[0118] S4. Propose a calculation method for the non-linear evolution of the tangential contact stiffness of the bolted joint surface based on three-dimensional fractal.

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

[0120] S41. Construct a mapping relationship model between the height of a single micro-protrusion and the fractal dimension D(t) and surface roughness parameter G(t), and define the coefficient λ related to the geometric shape parameters;

[0121] S42. Establish the elastic tangential contact stiffness K e (t), the elastic-plastic tangential contact stiffness K ep (t) and the plastic tangential contact stiffness Kp (t) Model;

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

[0123] The constructed model can be referred to the formulas (2) to (4) shown in the previous text, which will not be elaborated here.

[0124] S50. Test and verify this method to achieve accurate prediction of the tangential contact stiffness of the bolted joint surface.

[0125] Perform hammer tests on 5 specimens under different pre-tightening forces, collect their first-order natural frequencies, and compare them with the simulation analysis results to obtain Figure 6 the curve in Figure 6 It can verify the effectiveness of the above method.

[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 devices (including distributed systems), software (applications), modules, plugins, servers, clients, etc. that use the method described in the embodiments of this specification and are combined with the necessary implementation hardware. Based on the same innovative concept, the devices in one or more embodiments provided by the embodiments of this specification are as described in the following embodiments. Since the implementation solutions for the device to solve problems are similar to the method, the implementation of the specific device in the embodiments of this specification can refer to the implementation of the foregoing method, and the repeated parts will not be elaborated. As used below, the term "unit" or "module" may be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated. Figure 7 The following shows a schematic diagram of the device for determining the tangential contact stiffness of the bolted joint surface provided by the embodiment of the present application. As Figure 7 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 pre-tightening force relaxation model, and the pre-tightening force relaxation model is used to characterize the change relationship of the pre-tightening force of the bolted structure over 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 pre-tightening force relaxation model. The fractal dimension model and the surface roughness model are respectively used to characterize the change relationships of the fractal dimension and the surface roughness of the bolted structure over time.

[0129] The third modeling module 703 is configured to construct a tangential contact stiffness model that changes with time for the tangential contact stiffness of the bolted joint surface based on the pre-tightening force relaxation model, the fractal dimension model, and the surface roughness model.

[0130] The calculation module 704 is configured 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 may specifically be configured to: simulate the vibration condition and record the pre-tightening force relaxation data of the bolted structure at different times; and fit the pre-tightening force relaxation model based on the pre-tightening force relaxation data and the corresponding times.

[0132] In some embodiments of the present specification, the pre-tightening force relaxation model may be expressed by the following formula:

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

[0134] Wherein, F(t) may represent the pre-tightening force of the bolted structure at time t, F(0) may represent the pre-tightening force of the bolted structure at the initial time, and a, b, c, and d may represent coefficients.

[0135] In some embodiments of the present specification, the second modeling module 702 may specifically be configured to: obtain the microscopic morphology data of the joint surface of multiple bolted structures at the initial time as the initial microscopic morphology data; determine the pre-tightening force simulation step length and the pre-tightening force simulation range corresponding to each bolted structure; determine multiple simulated pre-tightening forces and the corresponding simulated times corresponding to each bolted structure based on the pre-tightening force relaxation model and the pre-tightening force simulation step length and the pre-tightening force simulation range corresponding to each bolted structure; obtain the simulated microscopic morphology data of the joint surface of each bolted structure under the corresponding multiple simulated pre-tightening forces and simulated times; determine the fractal dimension data and the surface roughness data corresponding to each bolted structure at different simulated times based on the initial microscopic morphology data and the 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 the surface roughness data of each bolted structure at multiple simulated times.

[0136] In some embodiments of this specification, the third modeling module 703 constructs a tangential contact stiffness model of the bolted joint surface that changes with time based on the pre-tightening force 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 pre-tightening force 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 this specification, when 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, it may specifically be used for: constructing a mapping model of each micro-protrusion on the bolted joint surface with the fractal dimension and surface roughness based on the fractal dimension model and the surface roughness model, and defining a coefficient 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 coefficient, 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 this specification, the mapping model and the coefficient related to the geometric shape of each micro-protrusion may be represented by the following formula:

[0139]

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

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

[0142]

[0143] where K e(t) can represent the elastic tangential contact stiffness of the bolted structure at time t, K ep (t) can represent the elastoplastic 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 asperities, G1 and G2 can represent the shear moduli of the rough surfaces, υ1 and υ2 can represent the Poisson's ratios of the materials of the bolted structure, ψ can represent the domain expansion factor, a l can represent the maximum cross-sectional area of the asperities, a 1c can represent the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c can represent the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation, H g 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, μ can represent the friction coefficient.

[0144] In some embodiments of this specification, the tangential contact stiffness model can be represented by the following formula:

[0145]

[0146] where, 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 elastoplastic 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 can represent the maximum cross-sectional area of the asperities, a 1c can represent the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c can represent the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation.

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

[0148] This application embodiment also provides an electronic device, as Figure 8 shown, this electronic device may include a processor 801 and a memory 802, where the processor 801 and the memory 802 may be connected through a bus or other means, Figure 8 taking the connection through the bus as an example.

[0149] The processor 801 may be a Central Processing Unit (CPU). The processor 801 may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. chips, or combinations of the above types of chips.

[0150] The memory 802, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as program instructions / modules corresponding to the method for determining the tangential contact stiffness of the bolted joint surface in the embodiments of the present invention (for example, Figure 7 the first modeling module 701, the second modeling module 702, the third modeling module 703, and the calculation module 704 in ). By running the non-transitory software programs, instructions, and modules stored in the memory 802, the processor 801 executes various functional applications and data processing of the processor, that is, implements the method for determining the tangential contact stiffness of the bolted joint surface in the above method embodiments.

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

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

[0153] Construct a pre-tightening force relaxation model, which is used to characterize the variation relationship of the pre-tightening force of the bolted structure with time; construct a fractal dimension model and a surface roughness model of the bolted joint surface based on the pre-tightening force relaxation model, where the fractal dimension model and the surface roughness model are respectively used to characterize the variation relationship of the fractal dimension and the surface roughness of the bolted structure with time; construct a tangential contact stiffness model of the bolted joint surface that changes with time based on the pre-tightening force relaxation model, the fractal dimension model, and the surface roughness model; input the assembly time of the target bolted structure to be evaluated into the tangential contact stiffness model, and calculate the tangential contact stiffness of the target bolted structure, so as to evaluate the target bolted structure based on the determined tangential contact stiffness.

[0154] For the specific details of the above electronic device, reference can be made to the corresponding relevant descriptions and effects in the above method embodiments for understanding, and details are not described herein again.

[0155] This specification also provides a computer storage medium, which stores computer program instructions, and when the computer program instructions are executed, the steps of the above method for determining the tangential contact stiffness of the bolted joint surface are realized.

[0156] Those skilled in the art can understand that to implement all or part of the processes in the above method embodiments, it can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. Among them, the storage medium can be a magnetic 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 types of memories.

[0157] Each embodiment in this specification is described in a progressive manner. The same or similar parts between each embodiment can be referred to each other, and the key points of each embodiment are the differences from other embodiments.

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

[0159] For the convenience of description, when describing the above device, various units are described separately according to their functions. Of course, when implementing the present application, the functions of each unit can be realized in one or more software and / or hardware.

[0160] From the description of the above embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of this application, in essence, or the part that makes contributions to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods of certain parts of various embodiments of this application.

[0161] This application can be used in many general-purpose or special-purpose computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multi-processor 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, and so on.

[0162] This application can 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. This application can also be practiced in a distributed computing environment where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0163] Although this application has been depicted through embodiments, those of ordinary skill in the art know that this application has many variations and changes without departing from the spirit of this application. It is hoped that the appended claims will cover these variations and changes without departing from the spirit of this application.

Claims

1. A method for determining the tangential contact stiffness of a bolted joint surface, characterized in that Including: Constructing a pre-tightening force relaxation model, which is used to characterize the relationship between the pre-tightening force of a bolted structure and time; Based on the pre-tightening force relaxation model, constructing a fractal dimension model and a surface roughness model of the bolted joint surface, where the fractal dimension model and the surface roughness model are respectively used to characterize the change relationship between the fractal dimension and the surface roughness of the bolted structure with time; Based on the pre-tightening force relaxation model, constructing a time-varying characteristic model of the tangential load and a time-varying characteristic model of the normal load of the bolted joint surface; Based on the fractal dimension model and the surface roughness model, constructing a mapping model between each micro-protrusion on the bolted joint surface and the fractal dimension and the surface roughness, and defining coefficients related to the geometric shape of each micro-protrusion; Based on the mapping model, the defined coefficients, the time-varying characteristic model of the tangential load, and the time-varying characteristic model of the normal load, constructing an elastic tangential contact stiffness sub-model, an elastic-plastic tangential contact stiffness sub-model, and a plastic tangential stiffness sub-model, which are represented by the following formulas: K p (t) = 0 Among them, K e (t) represents the elastic tangential contact stiffness of the bolted connection structure at time t, K ep (t) represents the elastoplastic tangential contact stiffness of the bolted connection structure at time t, K p (t) represents the plastic tangential stiffness of the bolted connection 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 asperities, G1 and G2 represent the shear moduli of the rough surfaces, υ1 and υ2 represent the Poisson's ratios of the materials of the bolted connection structure, ψ represents the domain expansion factor, a l represents the maximum cross-sectional area of the asperity, a 1c represents the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c represents the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation, H g represents the coefficient related to the material and fractal parameters of the bolted connection structure, F τ (t) represents the tangential load of the bolted connection structure at time t, F n (t) represents the normal load of the bolted connection structure at time t, and μ represents the friction coefficient; Based on the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model, constructing a tangential contact stiffness model, which is represented by the following formula: Among them, K τ (t) represents the tangential contact stiffness of the bolted structure at time t; 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.

2. The method for determining the tangential contact stiffness of the bolted joint surface according to claim 1, characterized in that Constructing a pre-tightening force relaxation model, including: Simulating the vibration condition and recording the pre-tightening force relaxation data of the bolted structure at different times; Based on the pre-tightening force relaxation data and the corresponding time, fitting to obtain the pre-tightening force relaxation model.

3. The method for determining the tangential contact stiffness of the bolted joint surface according to claim 1, wherein Based on the pre-tightening force relaxation model, constructing a fractal dimension model and a surface roughness model of the bolted joint surface, including: Obtaining the microscopic morphology data of the joint surface of multiple bolted structures at the initial time as the initial microscopic morphology data; Determining the pre-tightening force simulation step and the pre-tightening force simulation range corresponding to each bolted structure; Based on the pre-tightening force relaxation model, the pre-tightening force simulation step, and the pre-tightening force simulation range corresponding to each bolted structure, determining multiple simulated pre-tightening forces and the corresponding simulated times corresponding to each bolted structure; Obtaining the simulated microscopic morphology data of the joint surface of each bolted structure under the corresponding multiple simulated pre-tightening forces and simulated times; Based on the initial microscopic morphology data and the simulated microscopic morphology data of multiple bolted structures, determining the fractal dimension data and the surface roughness data corresponding to each bolted structure at different simulated times; Based on the fractal dimension data and the surface roughness data of each bolted structure at multiple simulated times, respectively constructing the fractal dimension model and the surface roughness model.

4. The method for determining the tangential contact stiffness of the bolted joint surface according to claim 1, characterized in that, The mapping model and the coefficients related to the geometric shape of each micro-protrusion are represented by the following formulas: where h represents the height of a single asperity, h i represents the height of a single asperity of the i-th bolted joint surface among multiple bolted joint 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 cross-section of the asperity, and λ represents the coefficient related to the geometric shape of the asperity.

5. A device for determining the tangential contact stiffness of a bolted joint surface, characterized in that, Including: The first modeling module is used to construct a pre-tightening force relaxation model, which is used to characterize the relationship between the pre-tightening force of a bolted structure and time; A second modeling module, configured to construct a fractal dimension model and a surface roughness model of the bolted joint surface based on the pre-tightening force relaxation model, where the fractal dimension model and the surface roughness model are respectively used to characterize the variation relationships of the fractal dimension and the surface roughness of the bolted structure with time; A third modeling module, configured to: Based on the pre-tightening force relaxation model, construct a time-varying characteristic model of the tangential load and a time-varying characteristic model of the normal load of the bolted joint surface; Based on the fractal dimension model and the surface roughness model, construct a mapping model of each micro-protrusion on the bolted joint surface with the fractal dimension and the surface roughness, and define coefficients related to the geometric shapes of the respective micro-protrusions; Based on the mapping model, the defined coefficients, the time-varying characteristic model of the tangential load, and the time-varying characteristic model of the normal load, construct an elastic tangential contact stiffness sub-model, an elastic-plastic tangential contact stiffness sub-model, and a plastic tangential stiffness sub-model, which are represented 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 elastoplastic 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 a coefficient related to the geometric shape of asperities, G1 and G2 represent the shear moduli of the rough surfaces, υ1 and υ2 represent the Poisson's ratios of the materials of the bolted structure, ψ represents the domain expansion factor, a l represents the maximum cross-sectional area of the asperity, a 1c represents the critical cross-sectional area for the transition from elastic deformation to elastoplastic deformation, a 2c represents the critical cross-sectional area for the transition from elastoplastic deformation to plastic deformation, H g represents a 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, μ represents the friction coefficient; Based on the elastic tangential contact stiffness sub-model, the elastic-plastic tangential contact stiffness sub-model, and the plastic tangential stiffness sub-model, construct a tangential contact stiffness model, which is represented by the following formula: Among them, K τ (t) represents the tangential contact stiffness of the bolted structure at time t;; A calculation module, configured 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, so as to evaluate the target bolted structure based on the determined tangential contact stiffness.

6. An electronic device, characterized in that, Comprising: A memory and a processor, where the processor and the memory are communicatively connected to each other, the memory stores computer instructions, and the processor realizes the steps of the method according to any one of claims 1 to 4 by executing the computer instructions.

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