A method for checking the bonding structure strength in the full service temperature range of a vehicle

Abstract

The present invention provides a method for checking the bonding structure strength in the full service temperature range of a vehicle. The method includes: obtaining the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working conditions; according to the basic material parameters and the pre-established finite element calculation model of the bonding structure under the most dangerous state working conditions, performing finite element simulation calculations under the pre-determined boundary conditions to obtain the failure stress nephogram; calculating the allowable equivalent stress under the most dangerous state working conditions according to the failure stress nephogram; performing simulation calculations on the corresponding locally refined model of the pre-established bonding structure under the working conditions to be detected to obtain the maximum equivalent stress under the working conditions to be detected; and checking the strength of the bonding structure according to the maximum equivalent stress and the allowable equivalent stress. By checking the strength of the bonding structure according to the allowable equivalent stress determined under the most dangerous state working conditions, the accuracy of strength checking can be effectively improved.

Description

Technical Field

[0001] This application belongs to the technical field of vehicle bonding structures, and particularly relates to a method for checking the strength of a bonding structure in the full service temperature range of a vehicle. Background Art

[0002] Compared with traditional connection technologies, the bonding connection technology has the advantages of uniform stress distribution, non-destruction of the plate structure, and anti-fatigue. In addition, elastic bonding also has the characteristics of good sealing, sound insulation, and noise reduction. Therefore, it has been widely used in the side windows of bullet trains.

[0003] In the prior art, the strength of the bonding structure is usually checked by the maximum nominal stress failure criterion or the secondary nominal stress failure criterion. However, in the failure process of the elastic bonding structure with a thick adhesive layer, due to large deformation, the cross-sectional area changes, and its failure stress cannot be simply obtained by dividing the failure strength by the bonding area. Therefore, the strength check result of the bonding structure in the prior art is inaccurate. Summary of the Invention

[0004] In view of this, the present invention provides a method for checking the strength of a bonding structure in the full service temperature range of a vehicle, aiming to solve the problem of poor stability in the process of checking the strength of the bonding structure in the full service temperature range of a vehicle.

[0005] The first aspect of the embodiment of the present invention provides a method for checking the strength of a bonding structure in the full service temperature range of a vehicle, including:

[0006] Design and manufacture a bonding structure that needs to be checked for strength;

[0007] Conduct aging experiments on the bonding structure under multiple aging cycles respectively, and conduct mechanical property tests on the bonding structure under each aging cycle to determine the most dangerous state working condition;

[0008] Obtain the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working condition;

[0009] Establish a finite element calculation model of the bonding structure according to the basic material parameters under the most dangerous state working condition, and determine the boundary conditions and failure load of the finite element calculation model;

[0010] Conduct finite element simulation calculations on the finite element calculation model according to the boundary conditions and the failure load under the most dangerous state working condition to obtain a failure stress nephogram;

[0011] Calculate the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram and embed it into the finite element calculation model for verification;

[0012] Establish a local refinement model and an overall model corresponding to the bonding structure;

[0013] Under the working conditions to be detected, perform simulation calculations on the overall model and the locally refined model to obtain the maximum equivalent stress under the working conditions to be detected;

[0014] According to the maximum equivalent stress and the verified allowable equivalent stress, perform strength check on the bonding structure.

[0015] The second aspect of the embodiments of the present invention provides a device for strength check of a bonding structure in the full service temperature range of a vehicle, including:

[0016] A preparation module, configured to design and manufacture a bonding structure that needs to be subjected to strength check;

[0017] An experiment module, configured to perform aging experiments on the bonding structure for multiple aging cycles respectively, and perform mechanical property tests on the bonding structure under each aging cycle to determine the most dangerous state working conditions;

[0018] An acquisition module, configured to acquire the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working conditions;

[0019] A first establishment module, configured to establish a finite element calculation model of the bonding structure according to the basic material parameters under the most dangerous state working conditions, and determine the boundary conditions and failure loads of the finite element calculation model;

[0020] A first simulation module, configured to perform finite element simulation calculations on the finite element calculation model according to the boundary conditions and the failure loads under the most dangerous state working conditions to obtain a failure stress nephogram;

[0021] A calculation module, configured to calculate the allowable equivalent stress under the most dangerous state working conditions according to the failure stress nephogram and embed it into the finite element calculation model for verification;

[0022] A second establishment module, configured to establish a locally refined model and an overall model corresponding to the bonding structure;

[0023] A second simulation module, configured to perform simulation calculations on the overall model and the locally refined model under the working conditions to be detected to obtain the maximum equivalent stress under the working conditions to be detected;

[0024] A strength check module, configured to perform strength check on the bonding structure according to the maximum equivalent stress and the verified allowable equivalent stress.

[0025] The third aspect of the embodiments of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for strength check of the bonding structure in the full service temperature range of the vehicle as described in the first aspect above are implemented.

[0026] The fourth aspect of the embodiments of the present invention provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the steps of the method for checking the bonding structure strength in the full service temperature range of the vehicle as described in the first aspect above.

[0027] The method for checking the bonding structure strength in the full service temperature range of the vehicle provided by the embodiments of the present invention includes: respectively performing aging experiments on the bonding structure for multiple aging cycles, and performing mechanical property tests on the bonding structure in each aging cycle to determine the most dangerous state working condition; obtaining the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working condition; performing finite element simulation calculations under the predetermined boundary conditions according to the basic material parameters and the pre-established finite element calculation model of the bonding structure under the most dangerous state working condition to obtain the failure stress nephogram; calculating the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram; performing simulation calculations on the locally refined model corresponding to the pre-established bonding structure under the working condition to be detected to obtain the maximum equivalent stress under the working condition to be detected; and checking the strength of the bonding structure according to the maximum equivalent stress and the allowable equivalent stress. By checking the strength of the bonding structure according to the allowable equivalent stress under the determined most dangerous state working condition, the accuracy of strength checking can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0029] Figure 1 is an application environment diagram of the method for checking the bonding structure strength in the full service temperature range of the vehicle provided by the embodiments of the present invention;

[0030] Figure 2 is a flowchart of the implementation of the method for checking the bonding structure strength in the full service temperature range of the vehicle provided by the embodiments of the present invention;

[0031] Figure 3 is a flowchart of the implementation of the method for checking the bonding structure strength in the full service temperature range of the vehicle provided by another embodiment of the present invention;

[0032] Figure 4 is a schematic structural diagram of the bonding structure provided by the embodiments of the present invention;

[0033] Figure 5 is a schematic diagram when the bonding structure is installed on the tooling fixture provided by the embodiments of the present invention;

[0034] Figure 6 It is the control curve diagram of the damp heat cycle aging test scheme provided by the embodiments of the present invention;

[0035] Figure 7 It is the structural schematic diagram of the Arcan fixture provided by the embodiments of the present invention;

[0036] Figure 8 It is the size schematic diagram of the adhesive dumbbell specimen provided by the embodiments of the present invention;

[0037] Figure 9 It is the schematic diagram of the finite element calculation model of the bonded joint under different stress states provided by the embodiments of the present invention;

[0038] Figure 10 It is the schematic diagram of the finite element calculation model under the boundary conditions provided by the embodiments of the present invention;

[0039] Figure 11 It is the failure stress nephogram provided by the embodiments of the present invention;

[0040] Figure 12 It is the division schematic diagram of the actual bonding boundary and the analysis boundary of the locally refined model provided by the embodiments of the present invention;

[0041] Figure 13 It is the schematic diagram of the grid quality recommendation standard of the locally refined model provided by the embodiments of the present invention;

[0042] Figure 14 It is the schematic diagram of the overall model simplified from the sliding plug door model provided by the embodiments of the present invention;

[0043] Figure 15 It is the schematic diagram of the constraint situation of the sliding plug door of the EMU provided by the embodiments of the present invention;

[0044] Figure 16 It is the schematic diagram of the finite element local model of the sliding plug door window body of the EMU provided by the embodiments of the present invention;

[0045] Figure 17 It is the displacement nephogram of the sub-model adhesive-A provided by the embodiments of the present invention;

[0046] Figure 18 It is the equivalent stress nephogram of the sub-model adhesive-A SDV3 provided by the embodiments of the present invention;

[0047] Figure 19 It is the displacement nephogram of the sub-model adhesive-B provided by the embodiments of the present invention;

[0048] Figure 20It is the equivalent stress nephogram of the sub-model adhesive-B SDV3 provided by the embodiments of the present invention;

[0049] Figure 21 It is the structural schematic diagram of the bonding structure strength checking device for the full service temperature range of the vehicle provided by the embodiments of the present invention;

[0050] Figure 22 It is the schematic diagram of the electronic device provided by the embodiments of the present invention. Detailed implementation manners

[0051] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0052] In order to further facilitate the travel needs of residents, high-speed trains have developed rapidly. Compared with traditional connection technologies, bonding connection technologies have the advantages of uniform stress distribution, non-destruction of the plate structure, and anti-fatigue, so they are gradually applied to high-speed trains. Elastic bonding structures also have the characteristics of good sealing, sound insulation, and noise reduction, and are widely used in the side windows of high-speed trains. When designing an elastic bonding structure, it is necessary to consider and select an appropriate adhesive layer thickness. If the thickness is too small, it cannot effectively insulate and reduce noise. If the thickness is too large, the deformation amount of the elastic bonding structure will also increase, which does not meet the safety requirements.

[0053] During the service process of high-speed trains, they will be in various harsh environments such as high and low temperatures and humidity for a long time, which puts higher requirements on the bonding structure strength. Different from metal materials, adhesives are prone to aging during use. As the service life increases, their performance continuously decays, and the decay degree is related to the use environment. Previous studies have shown that both the aging environment and the service temperature have a great impact on the mechanical properties such as the elastic modulus and Poisson's ratio of adhesives. However, it is difficult to distinguish the performance decay degree of adhesives macroscopically, and an effective prediction of their failure behavior is required through a certain checking method. Therefore, it is very urgent to seek a method for evaluating and checking the remaining strength of elastic bonding structures.

[0054] During the failure process of an elastic bonding structure with a thick adhesive layer, due to large deformation, the cross-sectional area changes, and its failure stress cannot be simply obtained by dividing the failure strength by the bonding area. Therefore, the maximum nominal stress failure criterion or the secondary nominal stress failure criterion cannot be used for checking. In addition, the failure criterion to be established cannot be limited to several specific environments and must have a certain degree of generality, that is, it is applicable to the failure behavior of elastic bonding structures in the full service temperature range after weather resistance tests.

[0055] In the prior art, the following steps are generally used to predict the mechanical properties of a bonding structure:

[0056] Step 1: Fabricate a test piece, which includes: Step 2: Place the test piece in a damp and hot environment chamber and conduct damp and hot cycling according to different temperature or humidity change cycles; Step 3: Take out the test piece for data testing every several cycles; Step 4: Calculate the approximate correlation between the discrete data related to the chemical properties and the discrete data of the mechanical properties by means of digital fitting, and combine the variation law of the aging coefficient with time and the variation law of the groups with time to obtain two sets of correlation indexes, thereby obtaining the mechanical property prediction result.

[0057] However, this method for predicting mechanical properties does not involve predicting the mechanical properties of the bonding structure within the full service temperature range. Moreover, it is unknown whether the designed bonding structure with an adhesive layer thickness of 0.2 mm is applicable to the performance prediction of a thick adhesive layer (≥5 mm) bonding structure.

[0058] In the prior art, when performing finite element modeling on the vehicle body, adhesive, glass, and window frame, a method combining overall modeling and local modeling is also generally used. The vehicle body is modeled using large-size elements, and the adhesive, glass, and window frame are modeled using small-size elements. First, the strength of the vehicle body is analyzed to obtain the displacement of the vehicle body deformation, then the triangular area interpolation method is used to realize the transfer of the vehicle body deformation displacement to the adhesive displacement, and finally the interpolated displacement is loaded onto the finite element models of the adhesive, glass, and window frame, considering the actual working conditions of the side window and submitting the calculation, so as to quickly analyze the bonding strength of the adhesive and lay a foundation for the subsequent strength verification and lightweight design of the bonding structure.

[0059] However, this method only considers the negative pressure effect and does not involve the influence of the aging environment and service temperature on the side window bonding structure. Moreover, an effective and accurate failure criterion has not been established to verify whether the strength of the elastic bonding structure meets the usage requirements.

[0060] The present invention conducts aging experiments on the bonding structure under multiple aging cycles respectively, and conducts mechanical property tests on the bonding structure under each aging cycle to determine the most dangerous state working condition; obtains the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working condition; conducts finite element simulation calculations under the predetermined boundary conditions according to the basic material parameters and the pre-established finite element calculation model of the bonding structure under the most dangerous state working condition to obtain the failure stress nephogram; calculates the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram; conducts simulation calculations on the locally refined model corresponding to the pre-established bonding structure under the working condition to be detected to obtain the maximum equivalent stress under the working condition to be detected; and verifies the strength of the bonding structure according to the maximum equivalent stress and the allowable equivalent stress.

[0061] Compared with the prior art, the present invention can achieve the following effects:

[0062] 1. The present invention can take into account the combined effects of two external factors, namely the aging environment and the service temperature, on the mechanical properties of the elastic bonding structure.

[0063] 2. The present invention is applicable to the strength check of bonding structures with thick adhesive layers (≥5 mm).

[0064] 3. The present invention establishes a failure criterion based on the dangerous working conditions of high-speed trains and can be applicable to the strength check of the elastic bonding structure of side windows.

[0065] Figure 1 It is an application environment diagram of the bonding structure strength check method for the full service temperature range of vehicles provided by the embodiments of the present invention. The bonding structure strength check method for the full service temperature range of vehicles provided by the embodiments of the present invention can be applied to this application environment but is not limited thereto. As Figure 1 shown, the system includes: a bonding structure 11, an electronic universal testing machine 12, and an electronic device 13.

[0066] The bonding structure 11 can be installed on the electronic universal testing machine 12, and the electronic universal testing machine 12 is connected to the electronic device 13. The electronic device 13 is used to instruct the electronic universal testing machine 12 to perform a quasi-static tensile test on the bonding structure 11, record the stress data during the experiment to determine the most dangerous state working condition, and the allowable equivalent stress under the most dangerous working condition. The electronic device 13 is also used to pre-establish a local refinement model of the bonding structure 11 to determine the maximum equivalent stress under the working condition to be detected, and perform a strength check on the bonding structure 11 according to the maximum equivalent stress and the allowable equivalent stress.

[0067] The bonding structure 11 can be a bonding structure at any position of the vehicle, such as the bonding structures at the plug door, roof panel, wheels, etc. of the vehicle, which are not limited herein. The material of the bonding structure 11 can be steel, aluminum alloy, etc., and the adhesives used can be polymer compound adhesives such as epoxy adhesives and nitrile rubber adhesives, which are not limited herein. The electronic device 13 can be a server, a terminal, etc., which are not limited herein. The terminal can include but is not limited to desktop computers, laptop computers, tablet computers, etc. The server can be an independent physical server, a cloud server, or a server cluster composed of multiple servers, which are not limited herein.

[0068] Figure 2 It is a flowchart of the implementation of the bonding structure strength check method for the full service temperature range of vehicles provided by the embodiments of the present invention. As Figure 2As shown, in this embodiment, the method for checking the bonding structure strength in the full service temperature range of the vehicle is applied to the electronic device 13 in the above embodiment, and includes:

[0069] S201, design and fabricate the bonding structure that needs to be checked for strength.

[0070] In this embodiment, the commonly used materials of the vehicle body structure are selected as the base materials of the bonding specimens, and the bonding surfaces are treated according to the usage requirements, including processes such as grinding, wiping, primer coating, and airing. The adhesive is applied to the bonding surfaces and the adhesive application amount is ensured to meet the bonding thickness requirements. Finally, the bonding joints are placed on the special fixtures to complete the butt joint assembly, and the bonding joints are cured according to the curing instructions of the adhesive.

[0071] S202, conduct aging experiments on the bonding structure under multiple aging cycles respectively, and conduct mechanical property tests on the bonding structure under each aging cycle to determine the most dangerous state working condition.

[0072] In this embodiment, the multiple aging cycles can be a set of pre-set aging cycles. An aging experiment is conducted on a bonding structure under each aging cycle, and thus the bonding structures in different aging situations can be obtained. Mechanical property tests are conducted on these bonding structures, and the working condition corresponding to the bonding structure with the lowest performance is the most dangerous state working condition.

[0073] S203, obtain the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working condition.

[0074] In this embodiment, each working condition can include an aging cycle and a service temperature. Under the aging cycle and service temperature corresponding to the most dangerous state working condition, the bonding structure is most likely to fail. The basic material parameters can include the elastic modulus E and Poisson's ratio v of the adhesive.

[0075] S204, establish a finite element calculation model of the bonding structure according to the basic material parameters under the most dangerous state working condition, and determine the boundary conditions and failure load of the finite element calculation model.

[0076] In this embodiment, finite element models with different loading angles are established respectively, and the mechanical parameters of the adhesive and bonding joints under dangerous conditions are introduced. Appropriate element types are selected. Considering that the deformation mainly comes from the adhesive layer and the stress distribution of the adhesive layer is focused on, the mesh division of the adhesive layer needs to be further refined. The boundary conditions of the simulation model are established according to the actual force conditions of the bonding joints. Considering that there are many uncertain factors in engineering structures, a certain safety factor usually needs to be considered when determining the failure load in strength design. The performance consistency of the bonding structure is relatively poor compared with the metal structure. Therefore, it is recommended that the safety factor is not less than 1.5.

[0077] S205. Under the most dangerous state working condition, perform finite element simulation calculations on the finite element calculation model according to the boundary conditions and failure loads to obtain the failure stress nephogram.

[0078] In this embodiment, the failure load applied to the bonding structure can be determined according to the boundary conditions. When the bonding structure is subjected to an actual load greater than the failure load, it will fail. Before performing the finite element simulation calculations, multiple stress loading angles can be simulated to obtain finite element calculation models under multiple stress loading states, and perform simulation calculations on the multiple obtained finite element calculation models respectively, so that the determined allowable equivalent stress can more accurately judge the failure of the bonding structure.

[0079] S206. Calculate the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram and embed it into the finite element calculation model for verification.

[0080] In this embodiment, the established failure criterion is written as a program with the help of a programming language, and the written failure criterion is embedded into the bonding structure simulation model by using the user subroutine of the simulation software. When the combined stress of the adhesive layer element is greater than or equal to the allowable equivalent stress [σ eq max at failure, the element will fail and be deleted. As the failure elements are deleted in sequence, the propagation process of the adhesive layer crack and the failure process of the bonding structure can be shown, and the failure process of the bonding structure obtained from the experiment is compared and analyzed with the simulation results of the finite element simulation model.

[0081] S207. Establish a locally refined model and an overall model corresponding to the bonding structure.

[0082] In this embodiment, when establishing the overall model, it is necessary to ensure the displacement mapping relationship between the sub-model nodes and the overall model nodes. A layer of virtual shell elements is established along this boundary, and its element thickness should be as thin as possible, which can be taken as 1 mm. The size of the virtual shell element is slightly wider than the boundary size, and its elastic modulus E1 is 2 to 3 orders of magnitude smaller than the elastic modulus E0 of the overall model, that is, E1 = (0.01 - 0.001)E0, to avoid the influence of the virtual element on the structural displacement and stress. To facilitate the extraction of boundary node displacements for subsequent calculations, the virtual elements at the cutting boundary need to be established as a set.

[0083] S208. Perform simulation calculations on the locally refined model corresponding to the pre-established bonding structure under the working condition to be detected to obtain the maximum equivalent stress under the working condition to be detected.

[0084] In this embodiment, an overall model and a locally refined model (sub-model of the overall model) are established for the bonding structure, where the overall model corresponds to the target component of the vehicle, and the locally refined model is obtained by dividing and refining the overall model and corresponds to the bonding structure.

[0085] When performing simulation calculations, boundary conditions are applied to the overall model under the working conditions to be detected, and the deformation displacement information of the nodes at the boundary of the sub-model in the overall model is extracted. The displacement information of the outermost nodes in the locally refined model of the window is calculated by applying a node-based difference mapping method, and this is used as the initial forced displacement condition and applied to the corresponding nodes to calculate the maximum equivalent stress under the working conditions to be detected.

[0086] S209. According to the maximum equivalent stress and the allowable equivalent stress, the strength of the bonding structure is checked.

[0087] In this embodiment, the allowable equivalent stress under the most dangerous state working conditions will be used as the criterion for the failure of the bonding structure under each working condition.

[0088] In this embodiment, by obtaining the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working conditions; according to the basic material parameters and the pre-established finite element calculation model of the bonding structure under the most dangerous state working conditions, finite element simulation calculations are carried out under the pre-determined boundary conditions to obtain the stress cloud diagram of failure; the allowable equivalent stress under the most dangerous state working conditions is calculated according to the stress cloud diagram of failure; simulation calculations are carried out on the locally refined model corresponding to the pre-established bonding structure under the working conditions to be detected to obtain the maximum equivalent stress under the working conditions to be detected; according to the maximum equivalent stress and the allowable equivalent stress, the strength of the bonding structure is checked. By checking the strength of the bonding structure according to the allowable equivalent stress determined under the most dangerous state working conditions, the accuracy of the strength check can be effectively improved.

[0089] Figure 3 It is the implementation flowchart of the method for checking the strength of the bonding structure in the full service temperature range of the vehicle provided by another embodiment of the present invention. As Figure 3 shown, in some embodiments, S206 may include:

[0090] S301. Determine multiple first stress components of the initial failure point of the bonding structure according to the stress cloud diagram of failure.

[0091] In this embodiment, calculation of allowable stress. After being processed and applied to the finite element calculation model of the bonding structure, the finite element analysis method is used to calculate the stress of the adhesive layer and analyze the stress state of the adhesive layer of the adhesive. A Python script is written to extract the basic stress components in the area of the initial failure point of the adhesive layer elements of the bonding structure for subsequent calculations. The basic stress components are six stress components: σ 11 , σ 22 , σ 33 , τ 12 , τ 13 , τ 23 ; three principal stresses: σ1, σ2, σ3 and Mises stress.

[0092] Based on the six basic stress components extracted, the maximum shear stress τ is obtained using formulas (1)-(7) max , three stress invariants (I1, I2, I3) of the total stress, and the stress sphere tensor σ m , the second invariant of deviatoric stress J2 * and the third invariant J3 of the deviatoric stress * , used to expand the amount of stress that can be combined.

[0093] The multiple first stress components in this embodiment may be part or all of the stress amounts in the above six basic stress components and the stress amounts expanded on the basis of the six basic stress components.

[0094] Among them, formulas (1)-(7) are as follows:

[0095] τ max =σ1-σ3 (1)

[0096]

[0097] I1=σ 11 +σ 22 +σ 33 (3)

[0098]

[0099]

[0100]

[0101]

[0102] S302, unifying the dimensions of the plurality of first stress components to obtain a plurality of second stress components.

[0103] In this embodiment, there are multiple stress components at the failure point of the adhesive layer unit, and the failure of the adhesive layer is not the result of a single stress component, but is determined by multiple stress components. In order to find the equivalent stress that can accurately predict the failure process of the adhesive structure, it is necessary to linearly combine multiple stress components. Therefore, it is necessary to unify the dimensions of the first stress component obtained in the previous step before linear combination. For example, for the MPa dimension 2 Stress (I2, J2 * ) and MPa 3 Stress (I3, J3 * ) The ratio method, product ratio method and power reduction method are used to reduce the dimensions of the obtained stress quantities to MPa, in preparation for the subsequent linear combination of multiple stress quantities.

[0104] The results after dimension unification are shown in Table 1:

[0105] Table 1 Results after dimension unification

[0106]

[0107] S303, randomly select any number of the second stress components for linear combination, and screen the linear combinations that meet the preset conditions to obtain the first linear combination.

[0108] In this embodiment, linear combination is performed on the second stress components obtained from Table 1. Select n non-repeating second stress components from Table 1: σ 01 (x), σ 02 (x), …, σ 0n (x), where (x = θ1, θ2, …, θ w ), and θ w is the w-th stress application angle. The new stress quantity is linearly combined as: a 01 *σ 01 (x) + a 02 *σ 02 (x) + … + a 0n *σ 0n (x) = k i , that is, the first linear combination is obtained. Among them, (a ∈ R, k i ≥0, i = 1, 2, …, w).

[0109] S304, use the first linear combination that meets the preset equivalent stress calculation formula as the allowable equivalent stress.

[0110] In this embodiment, calculations are performed separately for the loading joints in different stress loading states (θ1, θ2, ..., θ w ). For each determined coefficient α j (j = 1, 2, …, n), a set of k i will be obtained. When the standard deviation δ of k i ≤0.01, α j is the required value. At this time, the equivalent stress σ eq = a 01 *σ 01 + a 02 *σ 02 + … + a 0n *σ 0n .

[0111] In addition, to ensure that the finally obtained equivalent stress can effectively serve as the judgment basis for the bonding structure, the stress combination quantity obtained after linear combination (i.e., the above equivalent stress σ eq ) also needs to meet the following conditions:

[0112] (1) The maximum value of the equivalent stress is non - negative;

[0113] (2) It is satisfied under simple stress states;

[0114] (3) The failure points and non - failure points in the adhesive layer can be distinguished by the equivalent stress;

[0115] (4) The magnitude of the equivalent stress is independent of the stress state at the failure location;

[0116] (5) The magnitude of the equivalent stress varies approximately linearly with the change of the failure load.

[0117] In some embodiments, the formula for calculating the equivalent stress is:

[0118]

[0119] where k is the safety factor, γ is the equivalent stress coefficient, α j is the coefficient of the j - th stress component, σ j is the j - th stress component, and Δ j represents the expansion form corresponding to the j - th stress component.

[0120] In this embodiment, multiplying the obtained combined stress σ eq by the equivalent stress coefficient γ can obtain the allowable equivalent stress under the most dangerous state working condition at the i - th aging cycle t i and the j - th service temperature τ j : And combined with the finite - element calculation model, verify whether the above 5 judgment conditions are met. If they are met, use this allowable equivalent stress as the criterion for subsequent simulation failure, that is, as the failure criterion for determining the failure of the bonding structure.

[0121] In this embodiment, the maximum value of the calculated equivalent stress can be used as the allowable equivalent stress. When there are multiple stress loading states, the maximum value of the equivalent stress calculated under each stress loading state can be used as the equivalent stress of that loading state, and the minimum value of the equivalent stresses of each loading state can be used as the allowable equivalent stress.

[0122] In some embodiments, S209 may include:

[0123] If the maximum equivalent stress is less than the allowable equivalent stress, the bonding structure can work safely under the most dangerous state working condition;

[0124] If the maximum equivalent stress is not less than the allowable equivalent stress, the bonding structure cannot work safely under the most dangerous state working condition.

[0125] In this embodiment, after establishing the failure criterion of the bonding structure, it is necessary to embed the failure criterion into the simulation model to verify the accuracy of the failure criterion. The established failure criterion is written as a program with the help of a programming language, and the written failure criterion is embedded into the bonding structure simulation model by using the user subroutine of the simulation software. When the combined stress of the adhesive layer element is greater than or equal to the equivalent stress at failure (i.e., the allowable equivalent stress), the element will fail and be deleted. As the failed elements are sequentially deleted, the propagation process of the adhesive layer crack and the failure process of the bonding structure can be demonstrated, and the failure process of the bonding structure obtained from the test is compared and analyzed with the simulation results of the finite element simulation model of the bonding structure.

[0126] In some embodiments, the most dangerous working conditions include the most dangerous aging cycle and the most dangerous service temperature. S202 may include:

[0127] Obtain a plurality of preset experimental conditions; wherein, each preset experimental condition includes a preset aging cycle and a preset service temperature;

[0128] Conduct quasi-static tensile tests on the bonding structure under each preset experimental condition to obtain the load-displacement curves corresponding to each preset experimental condition;

[0129] Determine the remaining strength of the bonding structure under each preset experimental condition according to the load-displacement curves of each preset experimental condition;

[0130] Take the preset experimental condition corresponding to the lowest remaining strength as the most dangerous state working condition.

[0131] In this embodiment, referring to the standard DIN 6701-2-2006(E), the damp heat cycle working condition is selected to simulate the natural aging environment of the EMU for artificial accelerated aging test. The total duration of the aging test is initially set as T, and starting from the 0 cycle (without damp heat cycle), a group of bonding joints is taken out of the damp heat environment chamber every N cycle periods, and a total of M groups are taken out, where the aging cycles are t1, t2,..., t M . At each aging stage, the taken bonding specimens are used for m service temperature measurement points (the service temperature range is -40°C - 80°C), and the service temperature measurement points are respectively taken as τ1, τ2,..., τ m . To ensure the data validity, n elastic bonding joints should correspond to each test condition.

[0132] Conduct quasi-static tensile tests on the above M×m×n bonding joints to obtain the load-displacement curves and the remaining strength, and it is found that the remaining strength of the bonding joints is the lowest under the test conditions of aging cycle t i and service temperature τ j . At this time, the bonding joints are in a dangerous state.

[0133] In some embodiments, S204 may include:

[0134] Obtain a plurality of preset stress loading angles; wherein, each stress loading angle corresponds to a finite element calculation model of the bonding structure under a stress state;

[0135] Under the most dangerous state working condition, according to the basic material parameters and the finite element calculation models of the bonding structure under various stress states established in advance, perform finite element simulation calculations under the pre-determined boundary conditions to obtain the failure stress nephograms corresponding to each stress loading angle.

[0136] S206 may include:

[0137] Extract the maximum value from the failure stress nephograms corresponding to each stress loading angle;

[0138] Take the minimum value among the maximum values as the allowable equivalent stress.

[0139] In some embodiments, S208 may include:

[0140] Under the working condition to be detected, perform simulation calculations on the locally refined model corresponding to the bonding structure established in advance according to the equivalent stress calculation formula to obtain the maximum equivalent stress under the working condition to be detected.

[0141] S207 may specifically include:

[0142] Establishment of the locally refined model: According to the characteristics of the specific structure and the actual service working condition, simplify the original geometric model on the basis of comprehensively considering the calculation efficiency and calculation accuracy, remove sharp corners, feature holes, etc., and reconstruct complex feature surfaces. According to Saint-Venant's principle, in order to reduce the influence brought by the loading displacement deviation, when establishing the local model, the analysis boundary range should be larger than the actual bonding boundary. Generally, the outward expansion distance is at least more than 2 times the width of the adhesive layer, and the extended area is used as the local model boundary. When establishing the sub-model, high-quality meshes need to be divided. It is recommended that the mesh type consists of fully integrated 8-node hexahedral solid elements and 4-node shell elements. The size of the element is related to the thickness of the adhesive layer. Generally, the size of the adhesive layer element is not greater than one-third of the thickness of the adhesive layer, and the mesh is divided into smaller size meshes to ensure that the elements are regular to ensure the analysis accuracy. After the division is completed and the unit quality inspection is run, there are no unqualified meshes in both models.

[0143] Establishment of the overall model: The overall model needs to be calculated under various working conditions. The finite element element division method and size of the model should be determined according to the actual vehicle calculation. When establishing, to meet the refinement requirements of the subsequent local model, the boundaries of the local refinement model need to be separately represented in the overall model. Therefore, it is necessary to import the sub-model boundaries into the overall model and cut the overall model into two parts along the local model boundaries. To achieve the displacement mapping between the sub-model nodes and the overall model nodes, a layer of virtual shell elements is established along this boundary. The element thickness should be as thin as possible, and 1 mm can be taken. The size of the virtual shell elements is slightly wider than the boundary size, and the material properties are 2 - 3 orders of magnitude smaller than the normal values to avoid the virtual elements affecting the structural displacement and stress. To facilitate the extraction of the boundary node displacements for subsequent calculations, the virtual elements at the cutting boundary need to be established as a set.

[0144] When performing simulation calculations on the local refinement model, it is necessary to first perform finite element simulation calculations on the overall model.

[0145] Finite element simulation calculation of the overall model: During the actual service process of the EMU, it faces various working conditions, and all working conditions should be considered when calculating the overall model. Submit the calculation to obtain the result file of the overall model, and extract the node displacements at the boundaries of the local refinement model through the set of virtual elements at the cutting boundary.

[0146] The finite element simulation calculation of the local refinement model is specifically as follows: Embed the calculation method of the equivalent stress in the established adhesive structure failure criterion into the simulation software. Define the constraint conditions for each working condition of the overall model respectively, and the relevant load application and boundary constraints are exactly the same as those of the overall model. Extract the boundary displacements of the corresponding working conditions in the overall model, and link the boundary conditions of the sub-model with the calculated displacement values of the cutting boundary of the overall model. Check the results of the overall model to determine the output of the driving variables of the sub-model, and especially pay attention that there should be no local unreasonable phenomena around the area used to drive the sub-model.

[0147] After completing the simulation calculations, the equivalent stress of the adhesive layer in the sub-model result file can be viewed, and its maximum value is compared with the allowable equivalent stress. When the maximum stress is less than the allowable stress, the bonding structure is strong and safe and can work normally. When it is greater than the allowable stress, it indicates that there is a safety risk in the bonding structure strength, and it is recommended to conduct a safety assessment and subsequent improvement.

[0148] In some embodiments, the boundary condition is to adopt a fixed support constraint at one end of the finite element calculation model and apply the failure load obtained from the test at the other end;

[0149] The applied failure load is:

[0150]

[0151] Among them, F0′ is the test average failure load; F0 is the initially applied failure load.

[0152] The consistency of the performance of the bonding structure is relatively poor compared to the metal structure. Therefore, it is recommended that the safety factor be not less than 1.5. During the simulation of this embodiment, the test failure load needs to be divided by 1.5 before application.

[0153] The following provides an implementation example to illustrate the method for checking the bonding structure strength in the full service temperature range of the vehicle of the present invention of the present application, but it is not intended as a limitation. In this implementation example, the steps of the method for checking the bonding structure strength in the full service temperature range of the vehicle and the related preparatory work are as follows:

[0154] Step 1: Design and fabricate the bonding structure.

[0155] Figure 4 It is a schematic diagram of the bonding structure provided by the implementation example of the present invention. Figure 5 It is a schematic diagram when the bonding structure is installed on the tooling fixture provided by the implementation example of the present invention. As Figure 4 and Figure 5 shown, the bonding structure is an aluminum alloy bonding specimen, and the specific dimensions are as shown in the figure. The fabrication steps are as follows:

[0156] (I) Clean the aluminum alloy bonding surface with Sika Remover-208 in a dust-free and stable environment (temperature at 25 ± 5°C, humidity at 50 ± 5%), and air dry for 10 minutes.

[0157] (II) Cross-grind the aluminum alloy specimen with 80-mesh sandpaper at 45°.

[0158] (III) Clean the ground aluminum alloy specimen with Sika Remover-208 again, and air dry for 10 minutes.

[0159] (IV) Wipe the bonding surface of the aluminum alloy specimen with Sika Aktivator to activate the surface, and air dry for 10 minutes.

[0160] (V) Apply a layer of Sika Primer-206 GP primer on the bonding surface of the aluminum alloy specimen, and air dry for 30 minutes.

[0161] (VI) Place the groove of the tooling fixture flat on the horizontal platform, and apply a certain amount of adhesive on the bonding surface of one end 1 of the aluminum alloy test bar.

[0162] (VII) Put one end 1 of the aluminum alloy test bar into the groove, and use the fastening screw to control the metal pressing strip to press the aluminum alloy test bar tightly.

[0163] (VIII) Put the other end 2 of the aluminum alloy test bar into the groove, and use the fastening screw to control the metal pressing strip to be preliminarily pre-tightened.

[0164] (IX) Rotate the top core, press the aluminum alloy test bar 2 to move towards the aluminum alloy test bar 1, so that the two sections of aluminum alloy test bars are butted, and extrude the adhesive until the test bonding thickness is reached. The thickness of the bonded structural adhesive layer is jointly controlled by two methods: the dimension scale line and the vernier caliper. Then lock the fastening screws at the two parts of the aluminum alloy test bar, place the fixture after completing the bonding work in an environment with a temperature of 25 ± 5 °C and a humidity of 50 ± 5%, and let it stand for 30 days until the adhesive layer is cured.

[0165] (X) Remove the test piece and clean the remaining glue.

[0166] Step 2, determine the most dangerous state working condition.

[0167] Figure 6 It is the control curve graph of the damp heat cycle aging test scheme provided by the embodiment of the present invention. As Figure 6 shown, the horizontal axis is time, and the vertical axis is temperature or relative humidity. Carry out artificial accelerated aging test according to this control curve, and conduct mechanical property tests on the bonded structure in the full service temperature range after aging to determine the most dangerous state working condition.

[0168] The total duration of the aging test is initially set to 120 cycles (60 days), and starting from cycle 0 (without damp heat cycle), a group of bonded joints is taken out of the damp heat environment chamber every 20 cycle periods (10 days), and a total of 7 groups are taken out. Among them, the aging cycles are cycle 0, cycle 20, cycle 40, cycle 60, cycle 80, cycle 100, and cycle 120. At each aging stage, the taken bonded test pieces are used for 7 service temperature measurement points (which are -40 °C, -20 °C, 0 °C, 20 °C, 40 °C, 60 °C, 80 °C) respectively. In order to ensure the validity of the data, 10 elastic bonded joints are corresponding to each test condition.

[0169] Figure 7 It is the structural schematic diagram of the Arcan fixture provided by the embodiment of the present invention. As Figure 7 shown, after the aging test is completed, the above-mentioned 7×7×10 pairs of elastic bonded joints are installed on the Arcan fixture in the Figure 7 shown manner to conduct a quasi-static tensile test in an electronic universal testing machine, and obtain the load-displacement curve. It is found that the remaining strength of the elastic bonded joint is the lowest at the aging of 120 cycles and the service temperature of 80 °C. At this time, the bonded joint is most likely to fail. Therefore, it is determined as the most dangerous state working condition. In order to further determine which stress state of the elastic bonded joint is more likely to break at the aging of 120 cycles and the service temperature of 80 °C, tensile tests are also carried out under 7 stress states (0°, 15°, 30°, 45°, 60°, 75°, 90°) respectively. The control of the stress state is carried out in the Arcan fixture.

[0170] Step 3, Obtaining basic material parameters.

[0171] Figure 8 It is a schematic diagram of the size of the dumbbell specimen of the adhesive provided by the embodiment of the present invention. The bonding structure in this embodiment can be made with reference to Figure 8 the schematic diagram of the dumbbell specimen size.

[0172] Since the adhesive is temperature-sensitive and its mechanical properties vary greatly under different temperature conditions, it can be seen from the above weather resistance test of the elastic bonding joint that the performance of the adhesive drops most significantly when the service temperature is 80°C, and it is in the most dangerous state. Therefore, only the quasi-static tensile test of the adhesive dumbbell specimen can be selected at the service temperature of 80°C, and the VIC-3D non-contact full-field strain measurement system can be used to measure its non-contact deformation and strain, so as to obtain the stress-strain curve and transverse-longitudinal strain of the adhesive, and then calculate the elastic modulus E and Poisson's ratio v.

[0173] Step 4, Establishing a finite element calculation model of the bonding structure.

[0174] Currently, mainstream research institutions at home and abroad usually use ABAQUS software for the simulation of the bonding structure. Therefore, in this embodiment, this software is used as the finite element simulation tool. Finite element models of seven loading states are established respectively, and the relevant material parameters at 80°C after introducing 120 aging cycles (60 days) are introduced for finite element simulation calculation. Figure 9 It is a schematic diagram of the finite element calculation model of the bonding joint under different stress states provided by the embodiment of the present invention. As Figure 9 shown. Both the elastic glue layer and the aluminum alloy base material adopt solid elements (C3D8). Considering that the deformation mainly comes from the glue layer and the stress distribution of the glue layer is the key concern, the mesh division of the glue layer is refined. To save computing resources, each aluminum rod is 100 mm long in the experiment, and only 25 mm of the aluminum rod closer to the glue layer is selected in the simulation model, and the cross-sectional size is 25 mm × 25 mm. To simulate the stress of the glue layer under different stress states, an equivalent rigid body model is used to simulate the Arcan fixture on the basis of the simulation model of the joint at different angles for simulation.

[0175] Step 5, Determining boundary conditions and calculation loads.

[0176] Figure 10 It is a schematic diagram of the finite element calculation model under the boundary conditions provided by the embodiment of the present invention. As Figure 10As shown in the figure, RP reference points are established at both ends of the model, and Coupling is used to establish the constraint between the reference points and the model. One end of the model is fixed, and the failure load obtained from the test is applied to the other end. Considering that there are many uncertain factors in engineering structures, a certain safety factor k usually needs to be considered when determining the allowable stress in strength design. Therefore, the failure load formula in the calculation is as shown in formula (9). The performance consistency of the bonded structure is relatively poor compared to the metal structure. Therefore, it is recommended that the safety factor is not less than 1.5. During simulation, the test failure load needs to be divided by 1.5 before application.

[0177] Step 6, finite element calculation of the elastic bonded joint.

[0178] Figure 11 is the failure stress nephogram provided by the embodiment of the present invention. As Figure 11 shown, taking the 0° angle joint at 80°C as an example, finite element simulation calculations are performed on seven different loading angle joints at 80°C after hygrothermal cycling aging by applying the test failure stress and boundary conditions under the corresponding conditions to output the failure stress nephogram of the model.

[0179] Step 7, calculation of the failure criterion and the equivalent stress.

[0180] The calculation of the equivalent stress in this embodiment is Figure 3 roughly the same as the calculation process in the embodiment shown in

[0181] In this embodiment, the above-established failure criterion has been written into a subroutine. Before submitting the calculation, this program is embedded in the Job-General-User subroutine file interface, and this step can be automatically completed during the calculation. After the calculation is completed, the equivalent stress nephogram of SDV3 is output on the result page. The maximum value of the SDV3 stress is extracted as the maximum equivalent stress for this loading state. The minimum value of the equivalent stress in the seven states is taken as the allowable equivalent stress.

[0182] Step 8, boundary division.

[0183] Figure 12 is the schematic diagram of the division of the actual bonding boundary and the analysis boundary of the locally refined model provided by the embodiment of the present invention. As Figure 12 shown, according to the characteristics of the specific structure and the actual service conditions, the original geometric model is simplified on the basis of comprehensively considering the calculation efficiency and calculation accuracy, removing sharp corners, feature holes, etc., and reconstructing complex feature surfaces. According to Saint-Venant's principle, in order to reduce the influence brought by the loading displacement deviation, when establishing the local model, the analysis boundary range should be larger than the actual bonding boundary, and the outward expansion distance should be at least more than 2 times the width of the adhesive layer. The extended area is used as the local model boundary.

[0184] When establishing the sub-model, high-quality meshes need to be divided. It is recommended that the mesh type consists of fully integrated 8-node hexahedral solid elements and 4-node shell elements. The mesh is divided into smaller-sized meshes, with the size of the adhesive layer elements within 2 mm, ensuring that the elements are regular to guarantee the analysis accuracy. Figure 13 It is a schematic diagram of the mesh quality recommendation standard for the locally refined model provided by the embodiment of the present invention. As Figure 13 shown, in different regions, the recommended division methods of the high-quality meshes of the locally refined model are different. After the division, when running the element quality inspection, there are no unqualified meshes in both models.

[0185] Step 9, establish the overall model.

[0186] Figure 14 It is a schematic diagram of the overall model simplified from the sliding plug door model provided by the embodiment of the present invention. As Figure 14 shown, based on the geometric model of the sliding plug door of the high-speed multiple unit train after simplification, a finite element simulation model is established. The overall model uses a 4-mm mesh division. Among them, for the inner and outer windows of the sliding plug door, the adhesive structure, the foam filled between the inner and outer doors, the window frame, the upper window frame, and some structures of the left window frame, 8-node hexahedral solid elements are used, and the remaining parts are divided using 4-node quadrilateral elements. The specific division situation is shown in Table 2:

[0187] Table 2 Division of the bonding structure

[0188] Serial number Description Remarks 1 Outer window - A Tempered glass with a thickness of 5 mm 2 Adhesive - A Window glass and window frame adhesive with a thickness of 3 mm 3 Foam Polyurethane filler 4 Outer door Aluminum outer door panel with a thickness of 1 mm 5 Surface Sub - model geometric boundary 6 Outer window - B Low - conductivity glass 7 Inner window Inner layer glass 8 Window frame Aluminum window frame with a thickness of 1 mm 9 Inner door Aluminum inner door panel with a thickness of 1 mm

[0189] According to the geometric model structure, different thicknesses are assigned to each part, and a total of 1,259,593 nodes and 5,161,485 elements are divided. The mesh quality inspection results show that the mesh elements of the drawn finite element model have ideal quality and high calculation accuracy. To facilitate the establishment of the node mapping relationship of the sub-model and provide interpolation for the cutting boundary, a layer of Surface boundary is established at the intersection part of the sub-model and the overall model, and the attribute is given to be consistent with the filled foam, minimizing its influence on the structural strength.

[0190] Step 10, apply boundary conditions to the overall model.

[0191] According to the relevant content of EN 12663 "Railway applications - Structural requirements for railway vehicle bodies" defined for the tunnel working conditions, following the principle that the magnitude of the stress in the window bonding adhesive layer caused by the test load is consistent with the actual working stress. The window bonding structure is calculated according to the working conditions and the pneumatic uniform load specified in the EN 12663 standard, and a finite element analysis model is established for the window. The most dangerous pneumatic uniform load for the tunnel working conditions of the high-speed multiple unit train is 6000 Pa.

[0192] Figure 15 It is a schematic diagram of the restraint situation of the sliding plug door of the multiple unit train provided by the embodiment of the present invention. As Figure 15As shown in the figure, fixed constraints are applied to the position of the upper window frame rocker arm to restrict its six degrees of freedom in all directions. A pneumatic uniform load of 6000 Pa is applied to the window position area, and the general static analysis method is used for solution and calculation.

[0193] Step 11, perform finite element simulation calculation on the locally refined model.

[0194] Figure 16 It is a schematic diagram of the finite element local model of the plug door window body provided by the embodiment of the present invention. As Figure 16 shown in the figure, the key area containing the window bonding structure is segmented on the overall model, and a locally refined model of the window bonding structure is established in the finite element analysis software. The locally refined model (sub-model) mainly consists of seven parts: Adhesive A, Adhesive B, Inner window, Outer window-A, Outer window-B, Window frame, and Surface. The aluminum alloy window frame adopts four-node shell elements, and the rest of the structure adopts eight-node hexahedron elements. Finally, the number of elements in this local bonding structure model is 2,062,956, including 52,248 shell elements and 2,010,708 solid elements, and the number of nodes is 2,444,249.

[0195] Step 12, check the simulation model of the plug door. According to the working condition of pneumatic negative pressure, load and constraint are applied to the internal window of the sub-model, and the deformation displacement information of the nodes at the boundary of the sub-model in the overall model is extracted. The displacement information of the outermost nodes in the locally refined model of the window is calculated by applying the node-based difference mapping method and is used as the initial forced displacement condition to be applied to the corresponding nodes. The locally refined model of the window is simulated and calculated and analyzed by using the failure criterion based on equivalent stress established above, and the displacement and equivalent stress distribution nephograms of the adhesive layer elements in the bonding structure are obtained.

[0196] Figure 17 It is the displacement nephogram of sub-model adhesive-A provided by the embodiment of the present invention. Figure 18 It is the equivalent stress nephogram of sub-model adhesive-A SDV3 provided by the embodiment of the present invention. Figure 19 It is the displacement nephogram of sub-model adhesive-B provided by the embodiment of the present invention. Figure 20 It is the equivalent stress nephogram of sub-model adhesive-B SDV3 provided by the embodiment of the present invention. As Figures 17 - 20As shown, the maximum displacement of the stepped adhesive layer adhesive-A is 0.45 mm, and the maximum equivalent stress of SDV3 is 0.14 MPa. The maximum displacement of the regular adhesive layer adhesive-B is 0.0825 mm, and the maximum equivalent stress of SDV3 is 0.0103 MPa. The dangerous areas are all generated at the inner edge of the adhesive layer. Under the negative pressure, a deformation of 4.17 mm occurs at the center of the inner window, and stress concentration occurs at the interface of the stepped adhesive layer due to further extrusion in the contact area between the side edge and the inner window. The shape of the adhesive layer adhesive-B is relatively regular, and the stress distribution is relatively uniform. For the bonding structure under the most dangerous working condition, that is, after 60 days of damp heat cycle and at the test condition of 80 °C, the allowable stress of the adhesive layer is MPa. The maximum equivalent stresses of the stepped adhesive layer adhesive-A and the regular adhesive layer adhesive-B are both less than the allowable values. Therefore, the structure is safe under this aging condition.

[0197] It should be noted that: Although the method for strength checking of the bonding structure of the present invention is a general method, due to the great differences in the performance of bonding structures using different adhesives, when using the same adhesive, only one failure criterion needs to be established, while when using bonding structures with different adhesives, a failure criterion needs to be established for each corresponding adhesive.

[0198] The beneficial effects of the present invention are as follows:

[0199] 1. The present invention can perform strength checking on the elastic bonding structure of the EMU, predict and evaluate the aging failure behavior of the bonding structure, and provide experimental and theoretical support for the strength design of the bonding structure of high-speed EMUs.

[0200] 2. By formulating and implementing relevant tests, the present invention can determine the most dangerous conditions of the elastic bonding structure in the full service temperature range after the weather resistance test.

[0201] 3. The failure criterion proposed by the present invention is also applicable to the strength checking of the elastic bonding structure with a thick adhesive layer (6 mm).

[0202] 4. The failure criterion established by the present invention is applicable to the strength checking of the elastic bonding structure of the high-speed EMU sliding plug door, providing a reference for the subsequent design improvement of the sliding plug door structure.

[0203] 5. The present invention uses the submodel method to establish the overall model of the high-speed EMU sliding plug door and the local refined model of the sliding plug door window respectively, reducing the computational time cost while ensuring the simulation accuracy.

[0204] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0205] Figure 21 This is a schematic structural diagram of a bonding structure strength checking device for the full service temperature range of a vehicle provided by an embodiment of the present invention. As Figure 21 shown, in some embodiments, the bonding structure strength checking device 21 for the full service temperature range of a vehicle includes:

[0206] A preparation module 2110, configured to design and fabricate a bonding structure that needs to be subjected to strength checking;

[0207] An experiment module 2120, configured to perform aging experiments on the bonding structure under multiple aging cycles respectively, and perform mechanical property tests on the bonding structure under each aging cycle to determine the most dangerous state working condition;

[0208] An acquisition module 2130, configured to acquire the basic material parameters of the bonding structure in the target component of the vehicle under the most dangerous state working condition;

[0209] A first establishment module 2140, configured to establish a finite element calculation model of the bonding structure according to the basic material parameters under the most dangerous state working condition, and determine the boundary conditions and failure loads of the finite element calculation model;

[0210] A first simulation module 2150, configured to perform finite element simulation calculations on the finite element calculation model according to the boundary conditions and the failure loads under the most dangerous state working condition to obtain a failure stress nephogram;

[0211] A calculation module 2160, configured to calculate the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram and embed it into the finite element calculation model for verification;

[0212] A second establishment module 2170, configured to establish a local refinement model and an overall model corresponding to the bonding structure;

[0213] A second simulation module 2180, configured to perform simulation calculations on the overall model and the local refinement model under the working condition to be detected to obtain the maximum equivalent stress under the working condition to be detected;

[0214] A strength checking module 2190, configured to perform strength checking on the bonding structure according to the maximum equivalent stress and the verified allowable equivalent stress.

[0215] Optionally, the calculation module 2160 is specifically configured to determine multiple first stress components of the initial failure point of the bonding structure according to the failure stress nephogram;

[0216] Perform dimensional homogenization on the multiple first stress components to obtain multiple second stress components;

[0217] Randomly select any number of second stress components for linear combination, and screen the linear combinations that meet the preset conditions to obtain a first linear combination;

[0218] Take the first linear combination that satisfies the preset equivalent stress calculation formula as the allowable equivalent stress.

[0219] Optionally, the equivalent stress calculation formula is:

[0220]

[0221] where k is the safety factor, γ is the equivalent stress coefficient, α j is the coefficient of the j-th stress component, σ j is the j-th stress component, Δ j represents the expansion form corresponding to the j-th stress component.

[0222] Optionally, the strength checking module 2190 is specifically configured to: if the maximum equivalent stress is less than the allowable equivalent stress, the bonding structure can work safely under the most dangerous state working conditions;

[0223] if the maximum equivalent stress is not less than the allowable equivalent stress, the bonding structure cannot work safely under the most dangerous state working conditions.

[0224] In some embodiments, the most dangerous working conditions include the most dangerous aging period and the most dangerous service temperature.

[0225] The experiment module 2120 is used to obtain a plurality of preset experiment conditions; wherein, each preset experiment condition includes a preset aging period and a preset service temperature;

[0226] Perform a quasi-static tensile test on the bonding structure under each preset experiment condition to obtain a load-displacement curve corresponding to each preset experiment condition;

[0227] Determine the remaining strength of the bonding structure under each preset experiment condition according to the load-displacement curves of each preset experiment condition;

[0228] Take the preset experiment condition corresponding to the lowest remaining strength as the most dangerous state working condition.

[0229] Optionally, the first simulation module 2150 is specifically configured to obtain a plurality of preset stress loading angles; wherein, each stress loading angle corresponds to a finite element calculation model of the bonding structure under a stress state;

[0230] Under the most dangerous state working conditions, perform finite element simulation calculations according to the basic material parameters and the finite element calculation models of the bonding structure under various stress states established in advance under the pre-determined boundary conditions to obtain a failure stress nephogram corresponding to each stress loading angle.

[0231] The calculation module 2160 is specifically configured to extract the maximum value in the failure stress nephogram corresponding to each stress loading angle;

[0232] Take the minimum value among the maximum values as the allowable equivalent stress.

[0233] Optionally, the second simulation module 2170 is specifically configured to perform simulation calculations on the locally refined model corresponding to the bonding structure established in advance according to the equivalent stress calculation formula under the working conditions to be detected, and obtain the maximum equivalent stress under the working conditions to be detected.

[0234] Optionally, the boundary condition is to adopt a fixed support constraint at one end of the finite element calculation model and apply the failure load obtained from the test at the other end;

[0235] The applied failure load is:

[0236]

[0237] where F0′ is the average test failure load; F0 is the initially applied failure load.

[0238] The bonding structure strength checking device for the full service temperature range of the vehicle provided in this embodiment can be used to execute the method embodiment of the bonding structure strength checking method for the full service temperature range of the vehicle. The implementation principle and technical effects are similar, and will not be elaborated here in this embodiment.

[0239] Figure 22 It is a schematic diagram of the electronic device provided in the embodiment of the present invention. Figure 22 It is a schematic diagram of the electronic device provided in the embodiment of the present invention. As Figure 22 shown, the electronic device 22 in this embodiment includes: a processor 2200, a memory 2210, and a computer program 2220 stored in the memory 2210 and executable on the processor 2200. When the processor 2200 executes the computer program 2220, the steps in the above-mentioned method embodiments of the bonding structure strength checking method for the full service temperature range of the vehicle are implemented, such as Figure 2 the steps 201 to 205 shown. Alternatively, when the processor 2200 executes the computer program 2220, the functions of each module / unit in the above-mentioned device embodiments are implemented, such as Figure 21 the functions of the module 2110 to the module 2150 shown.

[0240] Exemplarily, the computer program 2220 can be divided into one or more modules / units. One or more modules / units are stored in the memory 2210 and executed by the processor 2200 to complete the present invention. One or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program 2220 in the electronic device 22.

[0241] The electronic device 22 can be a conventional electronic device or a dedicated electronic device serving a power dispatching center. Those skilled in the art can understand that Figure 22 are merely examples of the electronic device 22 and do not constitute a limitation on the electronic device 22. It may include more or fewer components than those shown in the figure, or combine certain components, or different components.

[0242] The so-called processor 2200 can be a central processing unit (CPU), or can 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. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc.

[0243] The memory 2210 can be an internal storage unit of the electronic device 22, such as the hard disk or memory of the electronic device 22. The memory 2210 can also be an external storage device of the electronic device 22, such as a plug-in hard disk equipped on the electronic device 22, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the memory 2210 can also include both the internal storage unit and the external storage device of the electronic device 22. The memory 2210 is used to store computer programs and other programs and data required by the terminal. The memory 2210 can also be used to temporarily store data that has been output or will be output.

[0244] An embodiment of the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps in the embodiment of the above-mentioned method for checking the bonding structure strength in the full service temperature range of the vehicle are implemented.

[0245] The computer-readable storage medium stores a computer program 2220, and the computer program 2220 includes program instructions. When the program instructions are executed by the processor 2200, all or part of the processes in the methods of the above embodiments are implemented. It can also be completed by instructing relevant hardware through the computer program 2220. The computer program 2220 can be stored in a computer-readable storage medium. When the computer program 2220 is executed by the processor 2200, the steps of the above various method embodiments can be implemented. Among them, the computer program 2220 includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice within the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0246] The computer-readable storage medium can be the internal storage unit of the terminal in any of the foregoing embodiments, such as the hard disk or memory of the terminal. The computer-readable storage medium can also be an external storage device of the terminal, such as a plug-in hard disk equipped on the terminal, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the computer-readable storage medium can also include both the internal storage unit and the external storage device of the terminal. The computer-readable storage medium is used to store the computer program and other programs and data required by the terminal. The computer-readable storage medium can also be used to temporarily store the data that has been output or will be output.

[0247] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0248] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiments can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of this application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated here.

[0249] In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0250] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in the form of hardware or software depends on the specific application and design constraints of the technical solution. Professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0251] In the embodiments provided by the present invention, it should be understood that the disclosed device / terminal and method can be implemented in other ways. For example, the device / terminal embodiments described above are only illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical or other forms.

[0252] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0253] In addition, in each embodiment of the present invention, each functional unit may be integrated into a processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0254] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above method embodiments of the present invention, it may also be completed by instructing relevant hardware through a computer program. The computer program may be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code may be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0255] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for checking the bonding structure strength in the full service temperature range of a vehicle, characterized in that Including: Design and fabricate an adhesive structure that requires strength verification; Conduct aging experiments on the adhesive structure for multiple aging cycles respectively, and conduct mechanical property tests on the adhesive structure under each aging cycle to determine the most dangerous state working condition; Obtain the basic material parameters of the adhesive structure in the target component of the vehicle under the most dangerous state working condition; wherein, the basic material parameters include the elastic modulus and Poisson's ratio of the adhesive; Establish a finite element calculation model of the adhesive structure based on the basic material parameters under the most dangerous state working condition, and determine the boundary conditions and failure load of the finite element calculation model; Conduct finite element simulation calculations on the finite element calculation model according to the boundary conditions and the failure load under the most dangerous state working condition to obtain a failure stress nephogram; wherein, the failure stress in the failure stress nephogram is obtained by linearly combining multiple stress quantities and is used to represent the equivalent stress in the failure process of the adhesive structure; Calculate the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram and embed it into the finite element calculation model for verification; Establish a local refinement model and an overall model corresponding to the adhesive structure; Conduct simulation calculations on the overall model and the local refinement model under the working condition to be detected to obtain the maximum equivalent stress under the working condition to be detected; Conduct strength verification on the adhesive structure according to the maximum equivalent stress and the verified allowable equivalent stress; The most dangerous state working condition includes the most dangerous aging cycle and the most dangerous service temperature; the conducting aging experiments on the adhesive structure for multiple aging cycles respectively, and conducting mechanical property tests on the adhesive structure under each aging cycle to determine the most dangerous state working condition includes: Obtain multiple preset experimental conditions; wherein, each preset experimental condition includes a preset aging cycle and a preset service temperature; Conduct quasi-static tensile tests on the adhesive structure under each preset experimental condition to obtain a load-displacement curve corresponding to each preset experimental condition; Determine the remaining strength of the adhesive structure under each preset experimental condition according to the load-displacement curves of each preset experimental condition; Take the preset experimental condition corresponding to the lowest remaining strength as the most dangerous state working condition.

2. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 1, characterized in that, The calculating the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram includes: Determine multiple first stress components of the initial failure point of the adhesive structure according to the failure stress nephogram; Perform dimensional homogenization on the multiple first stress components to obtain multiple second stress components; Randomly select any number of second stress components for linear combination, and screen the linear combinations that meet the preset conditions to obtain a first linear combination; Take the first linear combination that meets the preset equivalent stress calculation formula as the allowable equivalent stress.

3. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 2, characterized in that The equivalent stress calculation formula is: where k is the safety factor, γ is the equivalent stress coefficient, and α j is the coefficient of the j-th stress component, σ j is the j-th stress component, and Δ j represents the expansion form corresponding to the j-th stress component.

4. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 1, wherein Conduct strength verification on the adhesive structure according to the maximum equivalent stress and the verified allowable equivalent stress, including: If the maximum equivalent stress is less than the verified allowable equivalent stress, the adhesive structure can work safely under the most dangerous state working condition; If the maximum equivalent stress is not less than the verified allowable equivalent stress, the adhesive structure cannot work safely under the most dangerous state working condition.

5. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 1, characterized in that, Under the most dangerous state working condition, perform finite element simulation calculation on the finite element calculation model according to the boundary conditions and the failure load to obtain a failure stress nephogram, including: Obtain a plurality of preset stress loading angles; wherein, each stress loading angle corresponds to a finite element calculation model of the bonding structure under a stress state; Under the most dangerous state working condition, perform finite element simulation calculation on the finite element calculation model according to the boundary conditions and the failure load to obtain failure stress nephograms corresponding to each stress loading angle.

6. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 5, characterized in that Calculating the allowable equivalent stress under the most dangerous state working condition according to the failure stress nephogram includes: Extract the maximum value in the failure stress nephogram corresponding to each stress loading angle; Take the minimum value among the maximum values as the allowable equivalent stress.

7. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 1, characterized in that There is a displacement mapping relationship between the nodes of the local refinement model and the nodes of the overall model.

8. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to claim 1, characterized in that, After establishing the local refinement model and the overall model corresponding to the bonding structure, it further includes: Establish a layer of virtual shell elements along the boundary of the local refinement model; the size of the virtual shell elements is larger than the boundary size of the local refinement model, and the elastic modulus of the virtual shell elements is 2 to 3 orders of magnitude smaller than the elastic modulus of the overall model.

9. The method for checking the bonding structure strength in the full service temperature range of a vehicle according to any one of claims 1-8, characterized in that, The boundary condition is to adopt a fixed support constraint at one end of the finite element calculation model and apply the failure load obtained from the test at the other end; The applied failure load is: Wherein, F0′ is the test average failure load; F0 is the initially applied failure load.

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