Simulation analysis method for power battery box body structure of medium-volume rubber-tyred vehicle

Abstract

The invention provides a simulation analysis method for a power battery box body structure of a middle-volume rubber-tyred vehicle, which comprises the following steps: generating an original model of a power battery box body of the middle-volume rubber-tyred vehicle by utilizing three-dimensional modeling software, and optimizing the original model to obtain a model of the power battery box body structure; importing the model of the power battery box body structure into Hypermesh software, and establishing a finite element mechanical model of the power battery box body structure by utilizing the Hypermesh software; ansys software is used for conducting simulation verification on the static strength, the inherent frequency and the fatigue working condition of the power battery box body structure, the problems that due to the risk that verification fails when the box body structure is directly experimented, experiment product waste is caused, design efficiency is affected, and the design period is prolonged are solved, the calculation amount needed by simulation is greatly reduced, and the simulation efficiency is improved. The waste caused by experiment failure is reduced, the design efficiency is further improved, the production period is shortened to a great extent, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of simulation analysis of power batteries for medium-capacity rubber-wheeled vehicles, and in particular to a simulation analysis method for a box structure of a power battery for medium-capacity rubber-wheeled vehicles. Background Art

[0002] With the development of medium-capacity rubber-wheeled vehicles, the reliability of their power battery pack box structure is crucial. In related fields, it is necessary to verify the box structure of the battery pack of medium-capacity rubber-wheeled vehicles in accordance with the "Railway Vehicle Strength Design and Experimental Appraisal Specifications". However, there are many problems in directly testing the box structure according to the experimental conditions specified in the specifications. First of all, the actual working conditions are very complex and the specifications are extremely strict. During the experiment, when the box structure is subjected to a combination of various working conditions such as impact, vibration, temperature changes, etc., it is very likely that the structure will be deformed, damaged, and other situations that do not meet the requirements of the specifications will occur, resulting in verification failure.

[0003] From the perspective of cost and efficiency, the high risk of failure in direct experiments will result in a large waste of resources, because each experiment requires considerable manpower, material resources and time costs, including manufacturing experimental samples, setting up experimental environments, etc. Moreover, once the experiment fails, it needs to be redesigned and then tested again, which seriously affects the design efficiency and inevitably prolongs the product development cycle.

[0004] However, in the prior art, there is a lack of an effective method to reduce the risk, cost and improve the verification efficiency in the process of verifying whether the battery pack box structure of a rubber-wheeled vehicle meets the "Railway Vehicle Strength Design and Experimental Appraisal Specifications".

[0005] Therefore, the prior art needs to be further developed. Summary of the invention

[0006] The purpose of the present invention is to overcome the above technical deficiencies and provide a simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle to solve the problems existing in the prior art.

[0007] To achieve the above technical objectives, according to a first aspect of the present invention, the present invention provides a simulation analysis method for a power battery box structure of a medium-capacity rubber-wheeled vehicle, comprising: S100, using 3D modeling software to generate an original model of a power battery box of a medium-capacity rubber-wheeled vehicle, and optimizing the original model to obtain a model of the power battery box structure; S200, importing the model of the power battery box structure into the Hypermesh software, and using the Hypermesh software to establish a finite element mechanical model of the power battery box structure; S300. Based on the finite element mechanical model of the power battery box structure, use Ansys software to simulate and verify the static strength, natural frequency and fatigue conditions of the power battery box structure.

[0008] Specifically, the original model of the power battery box includes: Power battery box skeleton model, power battery pack model, high-voltage electrical control box model, and auxiliary sheet metal component model.

[0009] Specifically, the optimizing the original model to obtain an optimized model of the power battery box structure includes: In the 3D modeling software, the auxiliary sheet metal component model in the original model is deleted, and the power battery pack model and the high-voltage electrical control box model in the original model are removed to obtain the power battery box skeleton model of the original model, that is, the optimized power battery box structure model is obtained.

[0010] Specifically, the finite element mechanical model of the power battery box structure is established using Hypermesh software, including: The mid-surface is extracted from the model of the optimized power battery box structure, and the thickness information of the original power battery box plate is retained. The power battery box structure adopts quadrilateral plate shell units and triangular plate shell units, and the unit sizes of the quadrilateral plate shell units and triangular plate shell units are set to the first preset value.

[0011] Specifically, the method of establishing a finite element mechanical model of the power battery box structure using Hypermesh software also includes: A mass point unit is used to replace the power battery pack and the high-voltage electrical control box in the original model of the power battery box. The mass point unit has the same weight as the power battery pack and the high-voltage electrical control box. It is used to simulate the weight exerted by the power battery pack and the high-voltage electrical control box on the power battery box structure, thereby obtaining a finite element mechanical model of the power battery box structure.

[0012] Specifically, the S300 includes: The finite element mechanical model is imported into the Ansys software. The power battery box skeleton model includes a mounting seat model. Boundary constraints are applied to the mounting seat model in the Ansys software to simulate the fixed connection between the power battery box and other structures of the medium-capacity rubber-wheeled vehicle.

[0013] Specifically, the S300 further includes: Applying a standard static strength load to the mounting seat model to determine whether the maximum equivalent stress of the power battery box structure is less than the yield strength of the raw material; if so, determining that the static strength of the current power battery box structure meets the standard requirements; If not, it is determined that the static strength of the current power battery box structure does not meet the requirements.

[0014] Specifically, the S300 further includes: The vibration frequency of the first preset order of the medium-capacity rubber-wheeled vehicle body is obtained, recorded as the first vibration frequency, and the modal vibration of the first preset order is applied to the power battery box skeleton model in the Ansys software to obtain the natural frequency of the first preset order of the power battery box structure, recorded as the first natural frequency, and it is determined whether the first natural frequency is greater than the first vibration frequency, and whether the natural frequency of the power battery box structure meets the standard requirements according to the judgment result.

[0015] Specifically, judging whether the natural frequency of the power battery box structure meets the standard requirements according to the judgment result includes: If the first natural frequency is greater than the first vibration frequency, it is determined that the natural frequency of the power battery box structure meets the standard requirements; If the first natural frequency is less than or equal to the first vibration frequency, it is determined that the natural frequency of the power battery box structure does not meet the standard requirements.

[0016] Specifically, the S300 further includes: Applying a standard fatigue load to the mounting seat model in the Ansys software, performing a random vibration analysis on the power battery box structure, calculating the root mean square equivalent stress, and determining whether the root mean square equivalent stress is less than the standard equivalent stress. If so, determining that the fatigue condition of the current power battery box structure meets the standard requirements; If not, it is determined that the fatigue condition of the current power battery box structure does not meet the standard requirements.

[0017] Beneficial effects: The present invention uses Hypermesh software to establish a finite element mechanical model of a power battery box structure; according to the finite element mechanical model of the power battery box structure, Ansys software is used to simulate and verify the static strength, natural frequency and fatigue conditions of the power battery box structure, thereby solving the technical problem that there is a risk of verification failure when directly conducting experiments on the box structure, thereby causing waste of experimental products, affecting design efficiency and extending the design cycle, greatly reducing the amount of calculation required for simulation, reducing waste caused by experimental failure, further improving design efficiency, greatly shortening the production cycle and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a simulation analysis method for a power battery box structure of a medium-capacity rubber-wheeled vehicle provided in a specific embodiment of the present invention; Figure 2is an optimized schematic diagram of a power battery box structure provided in a specific embodiment of the present invention; Figure 3 is a schematic diagram of a finite element model provided in a specific embodiment of the present invention; Figure 4 It is a static strength stress distribution cloud diagram provided in a specific embodiment of the present invention under the conditions of applying longitudinal 5g, lateral 0g, and vertical -1g loads. DETAILED DESCRIPTION In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making creative work should all fall within the scope of protection of this application. In addition, the directional words mentioned in the following embodiments, such as "up", "down", "left", "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional words used are used to illustrate rather than limit the invention.

[0019] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0020] See also Figure 1 This embodiment provides a simulation analysis method for a power battery box structure of a medium-capacity rubber-wheeled vehicle, including: S100, using 3D modeling software to generate an original model of a power battery box of a medium-capacity rubber-wheeled vehicle, and optimizing the original model to obtain a model of the power battery box structure; It should be noted here that the first preset value and the first preset order are pre-set before step S100. It can be understood that the present invention does not limit the specific numerical values ​​of the first preset value and the first preset order, as long as the simulation method of the power battery box structure of the medium-capacity rubber-wheeled vehicle proposed in the present invention can be applied. Preferably, the present invention sets the first preset value to 10 mm. The above setting helps to control the number of grids, can reduce the number of grids, further reduce the amount of calculation required for simulation, and greatly improve the efficiency of simulation calculation, so that simulation results can be obtained faster with limited computing resources; the present invention sets the first preset order to 6, and the first 6 modal vibration modes can more comprehensively describe the vibration characteristics of the power battery box structure of the medium-capacity rubber-wheeled vehicle, further improving the accuracy of the simulation verification of the present invention.

[0021] Specifically, the original model of the power battery box includes: Power battery box skeleton model, power battery pack model, high-voltage electrical control box model, and auxiliary sheet metal component model.

[0022] In some specific embodiments, in order to ensure the normal operation of the rubber-wheeled vehicle, the complete power battery box system includes a power battery frame, a power battery pack, a high-voltage electrical control box, and some auxiliary sheet metal components. The main structure of the power battery box is mainly assembled by welding aluminum alloy profiles and sheet metal parts.

[0023] Specifically, the optimizing the original model to obtain an optimized model of the power battery box structure includes: In the 3D modeling software, the auxiliary sheet metal component model in the original model is deleted, and the power battery pack model and the high-voltage electrical control box model in the original model are removed to obtain the power battery box skeleton model of the original model, that is, the optimized power battery box structure model is obtained.

[0024] In some specific embodiments, CATIA software can be used to optimize the original model. After removing the power battery pack model and the high-voltage electrical control box model in the original model, auxiliary sheet metal component models such as chamfers, fillets, and round holes that have little impact on the load-bearing capacity of the power battery box structure in the original model can be appropriately deleted, and angular shapes can be directly used instead, thereby simplifying the model and further improving the efficiency of the simulation. In addition, 3D modeling software such as NX (Unigraphics), SolidWorks, Pro / Engineer (Creo), and AutoCAD can be used to generate the original model of the power battery box structure. The present invention does not impose further restrictions on the 3D modeling software used.

[0025] S200, importing the model of the power battery box structure into the Hypermesh software, and using the Hypermesh software to establish a finite element mechanical model of the power battery box structure.

[0026] Specifically, the finite element mechanical model of the power battery box structure is established using Hypermesh software, including: The mid-surface is extracted from the model of the optimized power battery box structure, and the thickness information of the original power battery box plate is retained. The power battery box structure adopts quadrilateral plate shell units and triangular plate shell units, and the unit sizes of the quadrilateral plate shell units and triangular plate shell units are set to the first preset value.

[0027] It should be further explained that for the optimized power battery box structure model, extracting the mid-surface is an effective means of simplification and analysis. Extracting the mid-surface can convert the three-dimensional solid model into a two-dimensional plate and shell model, which helps to greatly reduce the complexity of the model and the amount of calculation while ensuring accurate analysis of the mechanical properties of the box structure.

[0028] Furthermore, the thickness information of the original power battery box plate is crucial for accurately analyzing the mechanical properties of the box structure. The thickness of the plate directly affects its mechanical properties such as stiffness and strength. Retaining the thickness information after extracting the mid-surface can enable the subsequently established plate and shell unit model to correctly reflect the mechanical response of the plate under actual conditions.

[0029] It can be understood that the present invention sets the unit size of the above-mentioned quadrilateral plate and shell units and triangular plate and shell units to preferably 10 mm, which helps to control the number of grids and can reduce the number of grids. A larger unit size means that in the same model space, the number of divided units is relatively small. This is because the larger the unit size, the larger the area covered by a single unit, so that the total number of units required in the overall model will be reduced. Reducing the number of grids also reduces the complexity of the model. Simpler models are easier to handle in subsequent simulation calculations, and can reduce the consumption of computing resources, including memory usage and computing time. Due to the significant reduction in the number of grids, the amount of data that the computer needs to process during simulation calculations is also reduced accordingly. In finite element analysis, each grid needs to be calculated. The reduction in the number of grids means that the number of units that need to be analyzed and calculated is reduced, thereby directly reducing the amount of calculation required for the simulation, so that simulation results can be obtained faster with limited computing resources, greatly improving the efficiency of simulation calculations.

[0030] Specifically, the method of establishing a finite element mechanical model of the power battery box structure using Hypermesh software also includes: A mass point unit is used to replace the power battery pack and the high-voltage electrical control box in the original model of the power battery box. The mass point unit has the same weight as the power battery pack and the high-voltage electrical control box. It is used to simulate the weight exerted by the power battery pack and the high-voltage electrical control box on the power battery box structure, thereby obtaining a finite element mechanical model of the power battery box structure.

[0031] It should be noted here that the mass point unit is an idealized model element. It only has mass properties but no actual geometric shape. By setting the weight of the mass point unit to be the same as that of the power battery pack and the high-voltage electrical control box, it is possible to accurately simulate the weight effect they exert on the power battery box structure in the finite element model and simplify the model complexity. Using mass point units instead can effectively simplify the model and improve the efficiency of modeling and analysis without affecting the accuracy of the analysis of the mechanical properties of the box structure.

[0032] Furthermore, in the original model of the power battery box structure, it is necessary to determine the position of the mass point unit, which should correspond to the center of gravity of the power battery pack and the high-voltage electrical control box in the actual box. For example, if the power battery pack is located in the center of the bottom of the box and the high-voltage electrical control box is located in the middle of one side of the box, then the mass point unit should be placed in the finite element mechanics model according to the corresponding position relationship.

[0033] Furthermore, in the finite element modeling software, the mass point unit can be accurately located through the coordinate system. For example, a Cartesian coordinate system is established with a specific corner point of the box structure as the origin, and the coordinate value of the mass point unit in the coordinate system is determined according to the actual layout size. The mass point unit simulates the weight applied to the power battery box structure by applying a gravity load. In the finite element analysis software, according to the set gravity acceleration (usually 9.8m / s²), the mass point unit will generate a corresponding gravity force according to its mass value. The finite element mechanical model obtained by replacing the mass point unit can more accurately reflect the mechanical properties of the power battery box structure under actual conditions affected by the weight of the battery pack and the electrical control box.

[0034] S300. Based on the finite element mechanical model of the power battery box structure, use Ansys software to simulate and verify the static strength, natural frequency and fatigue conditions of the power battery box structure.

[0035] Specifically, the S300 includes: The finite element mechanical model is imported into the Ansys software. The power battery box skeleton model includes a mounting seat model. Boundary constraints are applied to the mounting seat model in the Ansys software to simulate the fixed connection between the power battery box and other structures of the medium-capacity rubber-wheeled vehicle.

[0036] Furthermore, the mounting base model plays a key role in connecting the power battery box body with other structures of the medium-capacity rubber-wheeled vehicle. Imposing boundary constraints on the mounting base model in the Ansys software is a key step in simulating the actual connection situation. The type of boundary constraints needs to be determined according to the actual fixed connection method. For example, if the mounting base is connected to other structures through bolts in actual situations, then in the Ansys software, fixed constraints can be imposed on the corresponding bolt hole positions on the mounting base model to limit its displacement in certain directions.

[0037] Specifically, the S300 further includes: Applying a standard static strength load to the mounting seat model to determine whether the maximum equivalent stress of the power battery box structure is less than the yield strength of the raw material; if so, determining that the static strength of the current power battery box structure meets the standard requirements; If not, it is determined that the static strength of the current power battery box structure does not meet the requirements.

[0038] It should be further explained that applying standard static strength load to the mounting seat model is a necessary operation to evaluate the static strength of the power battery box structure, that is, the components inside and outside the power battery box and its imprisoned parts should be assessed according to the standard static strength. The determination of the standard static strength load needs to refer to EN 12663-1:2010 "Railway Vehicle Strength Design and Experimental Evaluation Specification". These loads may include loads in different directions under different working conditions, including longitudinal loads, transverse loads, and vertical loads.

[0039] Specifically, the S300 further includes: The vibration frequency of the first preset order of the medium-capacity rubber-wheeled vehicle body is obtained, recorded as the first vibration frequency, and the modal vibration of the first preset order is applied to the power battery box skeleton model in the Ansys software to obtain the natural frequency of the first preset order of the power battery box structure, recorded as the first natural frequency, and it is determined whether the first natural frequency is greater than the first vibration frequency, and whether the natural frequency of the power battery box structure meets the standard requirements according to the judgment result.

[0040] Specifically, judging whether the natural frequency of the power battery box structure meets the standard requirements according to the judgment result includes: If the first natural frequency is greater than the first vibration frequency, it is determined that the natural frequency of the power battery box structure meets the standard requirements; If the first natural frequency is less than or equal to the first vibration frequency, it is determined that the natural frequency of the power battery box structure does not meet the standard requirements.

[0041] Furthermore, the present invention can select the vibration frequencies of the first 6 modal vibration modes and compare them with the natural frequencies of the power battery box structure, that is, when the first natural frequency is greater than the first vibration frequency, it is determined that the natural frequency of the power battery box structure meets the standard requirements. This is because when the natural frequency of the box structure is higher than the vibration frequency of the vehicle body, under normal operation, the vibration of the vehicle body is not easy to excite the box structure to resonate, and the box structure can maintain a relatively stable vibration state to avoid excessive vibration amplitude due to resonance, thereby ensuring the integrity of the box structure and the normal operation of internal components such as batteries. On the contrary, the vibration of the vehicle body is likely to excite the box structure to resonate, and the resonance will cause the vibration amplitude of the box structure to increase sharply, which may cause serious damage to the box structure.

[0042] Specifically, the S300 further includes: Applying a standard fatigue load to the mounting seat model in the Ansys software, performing a random vibration analysis on the power battery box structure, calculating the root mean square equivalent stress, and determining whether the root mean square equivalent stress is less than the standard equivalent stress. If so, determining that the fatigue condition of the current power battery box structure meets the standard requirements; If not, it is determined that the fatigue condition of the current power battery box structure does not meet the standard requirements.

[0043] It should be further explained that the setting of standard fatigue load is crucial for accurately evaluating the fatigue working condition of the power battery box structure. The setting of standard fatigue load refers to the specific provisions in EN 12663-1:2010 "Railway Vehicle Strength Design and Experimental Qualification Specification", that is, to ensure that the power battery box structure meets the fatigue working condition specified in EN 12663-1:2010 "Railway Vehicle Strength Design and Experimental Qualification Specification". The standard fatigue load specifically includes accelerations applied in different directions, namely longitudinal acceleration, lateral acceleration, vertical acceleration, etc. The second standard displacement and the second standard equivalent stress are both within the standard range specified in EN12663-1:2010 "Railway Vehicle Strength Design and Experimental Qualification Specification".

[0044] Furthermore, the root mean square equivalent stress is a key indicator for evaluating the fatigue condition of the power battery box structure. Random vibration refers to the random process of vibration excitation and response. In actual engineering, many vibration sources are random. This analysis can simulate the vibration conditions that the power battery box may encounter in the actual use environment. After the random vibration analysis, the root mean square equivalent stress is calculated. The root mean square equivalent stress is a stress indicator that comprehensively considers the stress fluctuation. It is obtained by calculating the root mean square of the function of stress changing with time. It can be used to evaluate the stress level of the structure under random vibration, indicating that under the action of fatigue load, the stress level of the power battery box structure is within the safe range that the material can withstand, which means that the box structure will not undergo plastic deformation or fatigue failure, and can ensure its normal operation throughout the fatigue life cycle. On the contrary, if the requirements are not met, the box structure may undergo plastic deformation, resulting in a decrease in its strength and stiffness, which will seriously affect the safety and reliability of the battery box.

[0045] Furthermore, in GB / T 21563-2018 "Shock and vibration test for railway rolling stock equipment", the calculation of standard equivalent stress value usually involves the yield strength and safety factor of the material. First, the yield strength of the material used needs to be determined. The yield strength is the stress value when the material begins to undergo plastic deformation, which can usually be obtained from the technical specifications of the material or relevant standards. In order to ensure the safety of the structure in practical applications, a safety factor is usually applied. The safety factor is a value greater than 1, which is used to reduce the yield strength of the material to a more conservative design value. The selection of the safety factor is usually based on experience, design specifications or requirements of specific applications. Calculation of standard equivalent stress value The standard equivalent stress value can be calculated by dividing the yield strength of the material by the safety factor. It should be noted that the calculation of the standard equivalent stress value is a conservative estimate designed to ensure that the structure will not fail under the expected working conditions. In actual design, other factors such as fatigue life, stress concentration, etc. may also need to be considered to ensure the reliability and safety of the structure.

[0046] See also Figure 2-Figure 4 The working principle of the present invention is described below by using specific examples: At present, the box structure of the battery pack of a medium-capacity rubber-wheeled vehicle needs to undergo the experimental conditions specified in the "Railway Vehicle Strength Design and Experimental Identification Specification". In order to verify whether the box structure meets the design requirements, the present invention proposes a joint simulation analysis method of Ansys and Hypermesh. For the box structure that needs to pass the conditions specified in the "Railway Vehicle Strength Design and Experimental Identification Specification", there is a risk of verification failure if the box structure is directly tested. The simulation verification method in the present invention can reduce the amount of calculation required for simulation, reduce the waste caused by experimental failure, improve design efficiency, shorten the production cycle, and reduce costs. The specific implementation process is as follows: 1. Achieve your goals (1) When finite element modeling is performed, the frame structure of the power battery box as the load-bearing body is mainly considered. Under the premise of ensuring that the simulation main model of the power battery box is consistent with the actual power battery box, auxiliary sheet metal parts such as chamfers, fillets, and circular holes that have little impact on the load-bearing structure are appropriately optimized; (2) Ensure that the power battery box structure meets the static strength load specified in EN 12663-1:2010 "Railway Vehicle Strength Design and Test Evaluation Specification", that is, the components inside and outside the power battery box and their fastening parts should be tested for strength according to the inertia force equivalent to the acceleration shown in Table 1; Table 1 Static strength analysis conditions (3) When a rubber-tyred vehicle is driving, the collision between the wheels and the road causes the entire train to vibrate. When the natural frequency of the battery box is the same as the vibration frequency of the train, resonance will occur, which will cause serious damage to the box body. Therefore, it is necessary to ensure that the first-order natural frequency of the power battery box is greater than the first-order vibration frequency of the vehicle body during operation.

[0047] (4) Ensure that the power battery box structure meets the fatigue conditions specified in EN 12663-1:2010 "Railway Vehicle Strength Design and Test Evaluation Specification" as shown in Table 2; Table 2 Fatigue strength analysis conditions 2. Structural scheme To ensure the normal operation of the rubber-wheeled vehicle, the complete power battery box system usually includes a power battery frame, a power battery pack, and a high-voltage electrical control box, which are assembled by welding aluminum alloy profiles and sheet metal parts.

[0048] The main components and weight of the power battery box are: 6 battery packs (K boxes), including the first battery pack (K box) - the sixth battery pack (K box), each weighing 140kg; 2 battery packs (J boxes), including the first battery pack (K box) and the second battery pack (K box), each weighing 160kg; high-voltage electrical control box, weighing 200kg.

[0049] 3. Digital-analog solution (1) Use CATIA software to optimize the original model, appropriately optimize the auxiliary sheet metal parts such as chamfers, fillets, and round holes that have little impact on the load-bearing structure, and optimize the skeleton model Figure 2 As shown; (2) Use Hypermesh software to establish a finite element mechanical model for the box structure, such as Figure 3 As shown in the figure, the mid-surface is extracted from the simplified geometric model, and the original sheet thickness information is retained. The sheet metal parts are mainly quadrilaterals with a unit size of 10 mm, and very few are triangular plate and shell units. The electrical components, namely the battery packs and the high-voltage electrical control box, are replaced by mass point units. This modeling method can reduce the number of grids by 70%, thereby reducing the amount of calculation required for simulation.

[0050] 4. Static strength simulation (1) Apply boundary constraints to the power battery box mounting bracket; (2) According to EN 12663-1:2010 "Railway Vehicle Strength Design and Experimental Qualification Specification", a static strength load as shown in Table 1 is applied to the mounting seat to observe the maximum equivalent stress of the power battery box and compare whether the maximum equivalent stress of the power battery box is less than the yield strength of the raw material. For example, the yield strength of grade 6063 aluminum alloy is 240MPa, the safety factor is 1.15, and the allowable yield strength is 240÷1.15=209MPa. Then, it is judged whether the static strength simulation is qualified.

[0051] 5. Modal simulation Apply the first 6 modal vibrations to the main frame of the power battery box, select the vibration frequencies and natural frequencies of the first 6 modal vibration modes of the box to observe whether the vibration frequencies of the first 6 modal vibration modes are far away from the natural frequencies of the vehicle body. Generally speaking, the natural frequency of the vehicle body is 25Hz, so as to judge whether the modal simulation verification is qualified; 6. Fatigue simulation (1) Apply boundary constraints to the power battery box mounting bracket; (2) For some vibration motions, their motion law shows considerable randomness and cannot be expressed by a definite function, but can only be described by probability and statistics. This kind of vibration is called random vibration. During random vibration, within a given frequency range, although the amplitude of the excitation still changes, the average value of the amplitude tends to a relatively stable constant. Based on this feature, the power spectral density (PSD) can be used to describe the statistical characteristics of random vibration excitation. According to random vibration theory, for a single input PSD value, the output is S XX (ω) = (|H(m)|)2S F‴F‴ (m); (1) Among them, S XX (ω) is the power spectral density response, SF‴F‴(m) is the power spectral density input, and H(m) is the frequency response function. The input PSD is actually the ratio of the mean square value of the excitation to the frequency bandwidth, so the output response including displacement, stress, strain and other values ​​are all corresponding mean square values. The root mean square (RMS) is obtained by taking the square root of the mean square value. The root mean square is a standard deviation response (1σ). Because the response of random vibration satisfies the normal distribution, the probability that the response is within the range of 3σ is 99.7%. In engineering analysis, the 3σ value can be used.

[0052] Random vibration analysis is performed under the power spectrum density specified in GB / T 21563-2018 "Shock and vibration test for railway rolling stock equipment", and the RMS equivalent stress values ​​in the X, Y, and Z directions are obtained respectively. The standard equivalent stress value is calculated using the yield strength of the material for comparison. The simulation result should be less than the standard equivalent stress.

[0053] The simulation analysis method of medium-capacity rubber-wheeled vehicle power battery was carried out by Ansys and Hypermesh to obtain some simulation results. Figure 4 As shown, it can be seen that the maximum equivalent stress of the power battery pack is 180.48Mpa, which is less than the yield strength of the material and meets the design requirements of the "Railway Vehicle Strength Design and Experimental Appraisal Specifications".

[0054] It should be noted here that the present invention uses Hypermesh software to establish a finite element mechanical model of the power battery box structure; according to the finite element mechanical model of the power battery box structure, Ansys software is used to simulate and verify the static strength, natural frequency and fatigue conditions of the power battery box structure, which solves the technical problem that there is a risk of verification failure when directly experimenting on the box structure, thereby causing waste of experimental products, affecting design efficiency and extending the design cycle, greatly reduces the amount of calculation required for simulation, reduces the waste caused by experimental failure, further improves design efficiency, greatly shortens the production cycle and reduces costs.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0056] The various technical features described above can be combined arbitrarily. Although all possible combinations of these technical features are not described, any combination of these technical features should be considered to be covered by this specification as long as there is no contradiction in such combination.

[0057] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle, characterized in that: include: S100, using 3D modeling software to generate an original model of a power battery box of a medium-capacity rubber-wheeled vehicle, and optimizing the original model to obtain a model of the power battery box structure; S200, importing the model of the power battery box structure into the Hypermesh software, and using the Hypermesh software to establish a finite element mechanical model of the power battery box structure; S300. Based on the finite element mechanical model of the power battery box structure, use Ansys software to simulate and verify the static strength, natural frequency and fatigue conditions of the power battery box structure.

2. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 1 is characterized in that: The original model of the power battery box includes: Power battery box skeleton model, power battery pack model, high-voltage electrical control box model, and auxiliary sheet metal component model.

3. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 2 is characterized in that: The optimizing the original model to obtain an optimized model of the power battery box structure includes: In the 3D modeling software, the auxiliary sheet metal component model in the original model is deleted, and the power battery pack model and the high-voltage electrical control box model in the original model are removed to obtain the power battery box skeleton model of the original model, that is, the optimized power battery box structure model is obtained.

4. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 3 is characterized in that: The finite element mechanical model of the power battery box structure is established by using Hypermesh software, including: The mid-surface is extracted from the model of the optimized power battery box structure, and the thickness information of the original power battery box plate is retained. The power battery box structure adopts quadrilateral plate shell units and triangular plate shell units, and the unit sizes of the quadrilateral plate shell units and triangular plate shell units are set to the first preset value.

5. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 4 is characterized in that: The method of establishing a finite element mechanical model of the power battery box structure using Hypermesh software also includes: A mass point unit is used to replace the power battery pack and the high-voltage electrical control box in the original model of the power battery box. The mass point unit has the same weight as the power battery pack and the high-voltage electrical control box. It is used to simulate the weight exerted by the power battery pack and the high-voltage electrical control box on the power battery box structure, thereby obtaining a finite element mechanical model of the power battery box structure.

6. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 5 is characterized in that: The S300 includes: The finite element mechanical model is imported into the Ansys software. The power battery box skeleton model includes a mounting seat model. Boundary constraints are applied to the mounting seat model in the Ansys software to simulate the fixed connection between the power battery box and other structures of the medium-capacity rubber-wheeled vehicle.

7. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 6 is characterized in that: The S300 further includes: Applying a standard static strength load to the mounting seat model to determine whether the maximum equivalent stress of the power battery box structure is less than the yield strength of the raw material; if so, determining that the static strength of the current power battery box structure meets the standard requirements; If not, it is determined that the static strength of the current power battery box structure does not meet the requirements.

8. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 6 is characterized in that: The S300 further includes: The vibration frequency of the first preset order of the medium-capacity rubber-wheeled vehicle body is obtained, recorded as the first vibration frequency, and the modal vibration of the first preset order is applied to the power battery box skeleton model in the Ansys software to obtain the natural frequency of the first preset order of the power battery box structure, recorded as the first natural frequency, and it is determined whether the first natural frequency is greater than the first vibration frequency, and whether the natural frequency of the power battery box structure meets the standard requirements according to the judgment result.

9. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 8 is characterized in that: The determining, based on the determination result, whether the natural frequency of the power battery box structure meets the standard requirements includes: If the first natural frequency is greater than the first vibration frequency, it is determined that the natural frequency of the power battery box structure meets the standard requirements; If the first natural frequency is less than or equal to the first vibration frequency, it is determined that the natural frequency of the power battery box structure does not meet the standard requirements.

10. The simulation analysis method for the power battery box structure of a medium-capacity rubber-wheeled vehicle according to claim 6 is characterized in that: The S300 further includes: Applying a standard fatigue load to the mounting seat model in the Ansys software, performing a random vibration analysis on the power battery box structure, calculating the root mean square equivalent stress, and determining whether the root mean square equivalent stress is less than the standard equivalent stress. If so, determining that the fatigue condition of the current power battery box structure meets the standard requirements; If not, it is determined that the fatigue condition of the current power battery box structure does not meet the standard requirements.

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