Battery pack box optimization design method based on Optistruct

Abstract

This invention provides a battery pack enclosure optimization design method based on Optistruct, relating to the field of new energy vehicle battery pack structural optimization design. The invention first obtains an initial finite element model of the battery pack enclosure, divides the enclosure into zones, and identifies initial weak areas. A first structural optimization is performed on the battery pack enclosure to obtain a first optimized enclosure model. Modal verification is performed on the first optimized enclosure model to identify weak areas of mode shape migration. Secondary optimization is then performed using the weak areas of mode shape migration and adjacent connection transition zones as the secondary optimization design domain to obtain a second optimized enclosure model, and the structural design parameters of the battery pack enclosure are determined. This invention can reduce the risk of local vibration concentrations after the first optimization being carried over to the final design parameters.

Description

Technical Field

[0001] This invention relates to the field of battery pack structure optimization design for new energy vehicles, and in particular to a battery pack housing optimization design method based on Optistruct. Background Technology

[0002] Power battery packs are typically located near the vehicle chassis. The battery pack housing serves not only as a mounting platform for the battery modules but also as a structural protector against road excitation, braking loads, cornering loads, and bottom impact loads. Current research and development often employs finite element analysis (FEM) methods for structural verification of the battery pack housing. This involves setting up braking, bumpy, and sharp turning conditions to analyze the displacement, stress, and modal response of the housing's top cover, bottom plate, module mounting base, and side panels. For example, the existing literature "Optimization Design of Battery Pack Housing Based on Optistruct" (Journal of Jilin Chemical Engineering Institute, Vol. 37, No. 9, 2020) uses ANSYS Workbench for static and dynamic finite element analysis of the battery pack housing and Optistruct for optimizing the top cover morphology and the composite material design of the bottom housing. This literature states that uneven road surfaces subject the battery pack to vibration excitation, and the battery housing, as the carrier of the power battery system, directly impacts its vibration resistance, durability, and connection reliability.

[0003] In structural optimization design, existing methods typically begin by identifying weak points in the housing through finite element analysis, followed by reinforcement of local structures using topology optimization, morphology optimization, dimensional optimization, or composite material layup optimization. In the aforementioned literature, addressing the insufficient stiffness of the housing's top cover, Optistruct morphology optimization was used to obtain the layout and geometric parameters of rectangular and E-shaped convex hulls, and composite material layup thickness was optimized to meet the strength and lightweight requirements of the lower housing. Existing literature, in "Structural Optimization Design of Battery Pack Housing for Pure Electric Vehicles," also uses a battery pack housing for a specific vehicle model as an example. Based on stress and displacement analysis results under coupled conditions of emergency braking, bumpy roads, and sharp turns, the OptiStruct solver was used to perform topology optimization of the bottom load-bearing beam, morphology optimization of the housing's top cover, and dimensional optimization of thin-walled components, and the housing's geometry was reconstructed based on the optimization results.

[0004] However, existing optimization methods for battery pack enclosures typically use the maximum deformation region, maximum stress region, or low-order natural frequency deficiency region exposed before optimization as the main design basis. After optimization, the evaluation results are mostly based on whether the maximum displacement, maximum equivalent stress, weight, and first-order natural frequency meet the standards. In the aforementioned literature, the maximum deformation, maximum equivalent stress, and first-order natural frequency of the enclosure were all improved after optimization. However, the literature also records that the first five resonance regions of the enclosure still occurred in the upper cover after optimization, and the vibration mode of the enclosure shifted from the upper cover to the front and rear sides of the lower enclosure from the sixth mode onwards. This phenomenon indicates that after the stiffness of the original weak region is improved by optimization, the dominant vibration region of the enclosure may shift. Existing methods do not identify and perform secondary constraint optimization on this shifted vibration mode region as a new design domain, which can easily lead to the formation of new dynamic weak points in higher-order modes or local connection transition regions of the optimized enclosure, thereby affecting the long-term structural reliability of the battery pack enclosure under complex road surface excitation. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a battery pack enclosure optimization design method based on Optistruct. By identifying the enclosure partition with concentrated vibration outside the initial weak area after the first structural optimization, and incorporating the enclosure partition and the adjacent connection transition area into the secondary optimization design domain, the structural design parameters of the battery pack enclosure can be corrected for the weak area of ​​mode migration generated after optimization, thereby reducing the risk of local vibration concentration continuing into the final design parameters.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A battery pack housing optimization design method based on Optistruct includes:

[0008] Obtain the initial finite element model of the battery pack enclosure, divide the enclosure into sections according to the structural parts, and determine the initial weak areas based on the structural response of the initial finite element model.

[0009] Taking the initial weak area as the first optimization object, the battery pack box is structurally optimized using Optistruct to obtain the first optimized box model;

[0010] Modal verification was performed on the first optimized box model to obtain the optimized modal distribution of each box partition;

[0011] Based on the optimized modal distribution, the box section located outside the initial weak region and forming a vibration concentration is identified as the mode migration weak region;

[0012] The second optimized box model is obtained by taking the weak zone of mode migration and the adjacent connection transition zone connected to the weak zone of mode migration as the secondary optimization design domain and performing local structural optimization on the secondary optimization design domain through Optistruct.

[0013] The structural design parameters of the battery pack enclosure are determined based on the second optimized enclosure model.

[0014] Preferably, the box is divided into sections according to its structural parts, including:

[0015] The battery pack enclosure is divided into an upper cover section, a lower bottom plate section, a lower side plate section, and a module mounting base section.

[0016] Set partition labels for each enclosure;

[0017] Make the partition identifier correspond to the same box structure part in the initial finite element model, the first optimized box model, and the second optimized box model.

[0018] Preferably, determining the initial weak region based on the structural response of the initial finite element model includes:

[0019] Obtain stress concentration, displacement concentration, and low-order mode concentration results in the structural response according to each box section;

[0020] Box sections with stress concentration results, displacement concentration results, or low-order mode concentration results are identified as candidate weak sections.

[0021] Candidate weak partitions that are interconnected and belong to the same bearer transmission path are merged into an initial weak region.

[0022] Preferably, taking the initial weak area as the first optimization object, the battery pack housing is structurally optimized using Optistruct to obtain the first optimized housing model, including:

[0023] Based on the location of the initial weak area in the box structure, the first optimization design domain is determined in Optistruct;

[0024] The topography of the primary optimization design domain located on the top cover of the box is optimized to obtain a local reinforcement structure for the top cover;

[0025] The size optimization, ply optimization, or local reinforcement optimization of the primary optimization design domain located in the lower box are performed to obtain the local load-bearing structure of the lower box.

[0026] Based on at least one of the top cover local reinforcement structure and the lower box local load-bearing structure, the first optimized box model is obtained.

[0027] Preferably, modal verification is performed on the first optimized box model to obtain the optimized modal distribution of each box partition, including:

[0028] Multimodal analysis was performed on the first optimized box model to obtain the vibration modes of each order.

[0029] Identify the location of vibration concentration and the direction of vibration deformation in each vibration mode according to the partition of each box;

[0030] The vibration concentration location and vibration deformation direction are associated with the corresponding box partitions to form an optimized modal distribution.

[0031] Preferably, based on the optimized modal distribution, the box section located outside the initial weak region and forming a vibration concentration is determined as the modal migration weak region, including:

[0032] Remove the enclosures that belong to the initial weak areas from each enclosure partition;

[0033] Based on the optimized modal distribution, identify the remaining box sections with continuous distribution of local mode deformation.

[0034] The box section with continuous distribution of local modal deformation is identified as the box section where vibration is concentrated and is determined as the weak area of ​​modal migration.

[0035] Preferably, the secondary optimization design domain is defined as the weak region of modal migration and the adjacent connection transition region connected to the weak region of modal migration, including:

[0036] Determine the connection boundary between the weak zone of mode migration and the adjacent box section;

[0037] Based on the connection boundary, at least one of the following is defined as the adjacent connection transition zone: the side plate transition zone, the bottom plate transition zone, and the adjacent zone of the mounting base, which bear the modal deformation transmission of the weak zone of modal migration.

[0038] The weak zone of mode migration and the transition zone of adjacent connection are defined as the secondary optimization design domain.

[0039] Preferably, the second optimized box model is obtained by performing local structural optimization on the secondary optimization design domain through Optistruct, including:

[0040] In Optistruct, the secondary optimization design domain is set as a local optimization region;

[0041] The optimization constraints are to reduce the vibration concentration in the secondary optimization design domain and maintain the stiffness transition of the adjacent connection transition zone. The local structural optimization parameters of the secondary optimization design domain are updated. The local structural optimization parameters include at least one of the local plate thickness parameters, local ply parameters and local strengthening structural parameters.

[0042] The corresponding region in the first optimized box model is replaced with the updated secondary optimized design domain to obtain the second optimized box model.

[0043] Preferably, based on the second optimized housing model, the structural design parameters of the battery pack housing are determined, including:

[0044] Obtain the structural parameters of the upper cover, lower box, and secondary optimization design domain from the second optimized box model;

[0045] Organize the structural parameters of the top cover, the bottom cover, and the secondary optimization design domain according to the structural parts of the box;

[0046] Based on the analysis results, the structural design parameters of the battery pack enclosure are determined. The structural design parameters of the battery pack enclosure include at least one of the following: local reinforcement structure arrangement parameters, plate thickness distribution parameters, ply distribution parameters, and connection transition zone parameters.

[0047] Preferably, determining the structural design parameters of the battery pack housing based on the second optimized housing model further includes:

[0048] The structural response of the second optimized box model was verified to obtain the verified structural response.

[0049] When there are box-shaped zones in the structural response that are outside the secondary optimization design domain and form vibration concentration, the box-shaped zones are updated as new weak areas of mode migration, and the secondary optimization design domain is redefined.

[0050] When there is no box section outside the secondary optimization design domain that forms a vibration concentration in the structural response of the verification structure, the structural design parameters of the battery pack box are determined according to the second optimized box model.

[0051] The present invention discloses the following beneficial effects:

[0052] (1) After obtaining the initial finite element model of the battery pack housing, the present invention first divides the housing into sections according to the structural parts of the housing, and determines the initial weak areas based on the structural response of the initial finite element model. As a result, different structural parts such as the housing cover, the lower housing bottom plate, the side plates, and the mounting base are no longer judged in the same overall evaluation result. The subsequent optimization object has a clear structural location source, which can avoid the problem of optimization position deviation when local reinforcement is carried out based only on the maximum stress point or the maximum displacement point of the whole housing.

[0053] (2) The present invention takes the initial weak area as the first optimization object and performs structural optimization on the battery pack housing through Optistruct to obtain the first optimized housing model. This process does not directly treat the entire housing area as the same optimization object, but first optimizes the weak parts that have been exposed by the structural response. This can retain the areas in the original battery pack housing that already meet the load-bearing requirements, reduce unnecessary modifications to non-weak areas, and provide a housing model with preliminary stiffness and strength adjustment for subsequent modal verification.

[0054] (3) After obtaining the first optimized box model, the present invention continues to perform modal verification on the first optimized box model to obtain the optimized modal distribution of each box partition. This step addresses the problem in the background art that the vibration position may shift from the original weak area to other structural parts after optimization. It can ensure that the optimized vibration concentration position falls back into the specific box partition, rather than using the first-order natural frequency as the basis for ending the optimization. Thus, the optimized modal changes can be incorporated into the subsequent design judgment process.

[0055] (4) Based on the optimized modal distribution, this invention identifies the box section located outside the initial weak area and forming a vibration concentration as the modal migration weak area. This limitation separately identifies the new vibration concentration area generated after strengthening the original weak area from the ordinary modal results, and can distinguish between the weak area that existed before the first optimization and the newly emerging vibration concentration area after the first optimization. For thin plate assembly structures such as battery pack boxes, there is a stiffness redistribution relationship between the top cover, side plates, bottom plate and connecting transitions. This identification method can form a clear secondary processing object for the modal migration phenomenon after stiffness adjustment.

[0056] (5) This invention uses the weak area of ​​the mode migration and the adjacent connection transition area connected to the weak area of ​​the mode migration as the secondary optimization design domain. Optistruct is used to perform local structural optimization on the secondary optimization design domain to obtain a second optimized box model. The structural design parameters of the battery pack box are then determined based on the second optimized box model. The secondary optimization object includes not only the box section with concentrated vibration but also the adjacent connection transition area connected to the box section, which can reduce the risk of sudden stiffness changes at the connection points caused by only locally thickening or strengthening the area with concentrated vibration. Compared with directly determining the design parameters after primary optimization, this invention can supplement and correct the weak area of ​​mode migration exposed after optimization without expanding the optimization scope to the entire box, so that the finally determined structural design parameters correspond to both the initial weak area and the weak area formed by the optimized migration. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 A flowchart of the method provided in an embodiment of the present invention;

[0059] Figure 2 This is a schematic diagram of the battery pack housing divided into sections according to structural parts, as provided in an embodiment of the present invention. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] The purpose of this invention is to provide a battery pack housing optimization design method based on Optistruct. On the basis of the initial weak area optimization, the non-initial weak housing partition that forms vibration concentration after optimization is further identified as the mode migration weak area. Local structural optimization is then performed around this area and the adjacent connection transition area, so that the battery pack housing structural design parameters simultaneously cover the original weak position and the weak position formed by the optimization migration.

[0062] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] Figure 1 The method flowchart provided in the embodiments of the present invention is as follows: Figure 1 As shown, this invention provides a battery pack housing optimization design method based on Optistruct, including:

[0064] Step 100: Obtain the initial finite element model of the battery pack enclosure, divide the enclosure into sections according to the structural parts of the enclosure, and determine the initial weak areas based on the structural response of the initial finite element model;

[0065] Step 200: Using the initial weak area as the first optimization object, perform structural optimization on the battery pack box using Optistruct to obtain the first optimized box model;

[0066] Step 300: Perform modal verification on the first optimized box model to obtain the optimized modal distribution of each box partition;

[0067] Step 400: Based on the optimized modal distribution, the box section located outside the initial weak area and forming a vibration concentration is identified as the mode migration weak area;

[0068] Step 500: Using the weak zone of mode migration and the adjacent connection transition zone connected to the weak zone of mode migration as the secondary optimization design domain, perform local structural optimization on the secondary optimization design domain through Optistruct to obtain the second optimized box model;

[0069] Step 600: Determine the structural design parameters of the battery pack enclosure based on the second optimized enclosure model.

[0070] Specifically, in step 100, the initial finite element model is first partitioned based on the actual structural parts of the battery pack housing. Specifically, the area within the battery pack housing responsible for enclosure, protection, and upper rigidity is designated as the top cover partition; the area bearing the weight of the battery modules and transmitting bottom loads is designated as the bottom plate partition; the area forming the circumferential boundary of the housing and connecting the top cover and bottom plate is designated as the side plate partition; and the area used for supporting, limiting, or fixing the battery modules is designated as the module mounting base partition. The side plate partition can be further subdivided into front, rear, left, and right side plates, but each subdivision still belongs to the side plate partition. After completing the above partitioning, partition identifiers are set for each housing partition. These identifiers indicate the fixed position of the corresponding housing partition within the housing structure and do not change with subsequent structural optimization processes involving local thickening, thinning, reinforcement, or ply adjustments.

[0071] like Figure 2 As shown, the battery pack housing 1 includes an upper housing cover section 11, a lower housing bottom plate section 12, a lower housing side plate section 13 that surrounds the upper housing cover section 11 and the lower housing bottom plate section 12 and connects them in the circumferential direction, and a module mounting base section 14 that is disposed inside the battery pack housing 1 to support and limit the installation position of the battery modules; wherein, the upper housing cover section 11 mainly corresponds to the upper closed protective structure of the housing, the lower housing bottom plate section 12 mainly corresponds to the bottom load-bearing structure of the housing, the lower housing side plate section 13 mainly corresponds to the circumferential enclosure and force transmission connection structure of the housing, and the module mounting base section 14 mainly corresponds to the module support and installation structure inside the housing. All sections together constitute the battery pack housing partition foundation for subsequent structural response analysis, initial weak area identification and optimization design.

[0072] During the use of partition identifiers, the initial finite element model, the first optimized box model, and the second optimized box model adopt the same correspondence between box structure parts. That is, the box top cover partition corresponds to the structural part of the box top cover in all three models; the lower box bottom plate partition corresponds to the structural part of the lower box bottom plate in all three models; the lower box side plate partition corresponds to the structural part of the lower box side plate in all three models; and the module mounting base partition corresponds to the structural part of the module mounting base in all three models. When geometric changes occur after model optimization, newly added local reinforcement structures, adjusted plate thickness areas, or adjusted ply areas are still classified back into their respective box partitions. This partition identifier retention method allows for comparison of the initial structural response, optimized modal distribution, and subsequent secondary optimization objects within the same structural part system, preventing the response results before and after optimization from losing their correspondence due to changes in model morphology.

[0073] When determining the initial weak region based on the structural response of the initial finite element model, stress concentration, displacement concentration, and low-order mode shape concentration results are read separately for each box section. Stress concentration results are determined based on high equivalent stress, significant stress gradient, or stress concentration location near the connection transition. Displacement concentration results are determined based on large deformation within a section or significant relative deformation between adjacent sections. Low-order mode shape concentration results are determined based on local continuous bending, local vertical vibration, or local torsional deformation concentrated in a specific box section within low-order modes. Box sections exhibiting stress concentration, displacement concentration, or low-order mode shape concentration results are identified as candidate weak regions. When multiple candidate weak regions are structurally interconnected, and the load can be continuously transferred along the same plate, bending transition, connection boundary, or mounting support path, these candidate weak regions are merged into a single initial weak region. Through this process, the initial weak region not only covers a single abnormal response location but also adjacent structural parts that share the load transfer with that abnormal location.

[0074] In step 200, a primary optimization design domain is determined based on the location of the initial weak area in the housing structure identified in step 100. Specifically, when the initial weak area is located in the upper cover section of the housing, the area in the upper cover section exhibiting displacement concentration, low-order vibration mode concentration, or continuous distribution of local bending deformation is identified as the primary optimization design domain; when the initial weak area is located in the lower housing bottom plate section, lower housing side plate section, or module mounting base section, the corresponding load-bearing plates, connecting transition parts, and mounting support parts are identified as the primary optimization design domain; when the initial weak area spans more than two housing sections, structural areas belonging to the same load transfer path in adjacent housing sections are included in the primary optimization design domain. The primary optimization design domain does not involve indiscriminate adjustment of the entire battery pack housing, but is limited to the weak structural parts identified by the initial structural response and their necessary force-transfer adjacent areas to ensure that subsequent optimization results correspond to the actual stress and deformation sources of the initial weak area.

[0075] When optimizing the morphology of the primary optimization design domain located on the top cover of the housing, without changing the basic installation boundary and sealing boundary of the top cover partition, a local reinforcement structure is formed in the top cover partition. The local reinforcement structure can be a raised reinforcement, a concave-convex rib, a ring reinforcement, or a locally formed reinforcement arranged along the vibration deformation direction. When optimizing the structure of the primary optimization design domain located in the lower housing, the thickness distribution, ply distribution, or arrangement of local reinforcement structures in the corresponding areas are adjusted according to the load-bearing method of the bottom plate partition, side plate partition, or module mounting base partition of the lower housing to form a local load-bearing structure of the lower housing. The local load-bearing structure of the lower housing is used to improve the load-bearing continuity and local deformation resistance of the corresponding parts of the lower housing. After completing the above optimization, at least one of the top cover local reinforcement structure and the lower housing local load-bearing structure is incorporated into the battery pack housing model, while keeping the housing partition correspondence determined in step 100 unchanged, to obtain the first optimized housing model.

[0076] Specifically, in step 300, when performing modal verification on the first optimized box model obtained in step 200, the box partitions and partition identifiers determined in step 100 are kept unchanged, so that the modal verification results can continue to correspond to the box top cover partition, lower box bottom plate partition, lower box side plate partition, and module mounting base partition. Modal verification includes extracting the natural frequencies of the first optimized box model within a preset order range and the mode shapes corresponding to each natural frequency. Each mode shape is used to characterize the structural deformation of the first optimized box model at the corresponding natural frequency. The structural deformation includes local bending, local vertical vibration, local torsion, and relative vibration between adjacent structural parts. After performing multi-order modal analysis, not only the lowest order natural frequency is recorded, but the mode shape distribution in multiple consecutive orders is also checked to avoid using the attainment of only the first order natural frequency as the end condition for modal verification. For each mode shape, the vibration concentration location and vibration deformation direction in the mode shape are identified according to the box body partitions. The vibration concentration location refers to the box body structure location where the displacement amplitude is significantly concentrated, the local deformation is continuously distributed, or the relative deformation of adjacent structural parts is relatively obvious in the same mode shape. The vibration deformation direction refers to the main deformation trend exhibited by the vibration concentration location in the mode shape, including vertical deformation towards the height of the box body, bending deformation along the length of the box body, lateral deformation along the width of the box body, or torsional deformation around the local connection parts.

[0077] After obtaining the vibration concentration location and vibration deformation direction in each mode shape, the vibration concentration location is correlated with the box section in step 100 to determine which section the vibration concentration location falls into: the box top cover section, the lower box bottom plate section, the lower box side plate section, or the module mounting base section. When the vibration concentration location spans more than two box sections, all spanned box sections are considered as associated sections for that mode shape, and the consistency of vibration deformation directions between adjacent box sections is recorded. Subsequently, the natural frequencies, corresponding mode shapes, vibration concentration locations, vibration deformation directions, and associated box sections are combined to form the optimized modal distribution. The optimized modal distribution is used to indicate the changes in vibration concentration locations and vibration directions of the first optimized box model after a structural optimization, including both vibration concentration results still located within the initial weak area and vibration concentration results transferred to areas outside the initial weak area. Through the above disclosure method, the optimized modal distribution obtained in step 300 can serve as a direct basis for identifying the weak area of ​​mode shape migration in step 400.

[0078] Optionally, in step 400, the optimized modal distribution is first screened based on the enclosure partitions and partition identifiers formed in step 100. Specifically, enclosure partitions that have been identified as initial weak areas are removed, and only the enclosure top cover partition, lower enclosure bottom plate partition, lower enclosure side plate partition, or module mounting base partition outside the initial weak areas are retained as enclosure partitions to be judged. For initial weak areas that span more than two enclosure partitions, the removal range is determined according to the partition identifiers actually covered by the initial weak areas; enclosure partitions that are only adjacent to the initial weak areas but have not been merged into the initial weak areas are not removed. Through the above processing, the subsequent judgment objects are limited to enclosure partitions where vibration concentration newly appears after one optimization, rather than repeatedly judging the original weak locations.

[0079] When performing vibration concentration judgment on the box section to be judged, the vibration concentration location and vibration deformation direction in the optimized modal distribution are read step by step. For any box section to be judged, the nodal displacement amplitude or element representative displacement amplitude under the same vibration mode is extracted first, and then it is judged whether the high displacement amplitude area forms a continuous distribution in space. Continuous distribution means that multiple adjacent nodes, adjacent elements or adjacent shell areas are continuously arranged along the same box structure part, and there is no obvious reverse jump in the vibration deformation direction between adjacent positions. For the lower box side plate section, the continuous distribution can be manifested as a bending deformation band extending along the height or length direction of the side plate; for the lower box bottom plate section, the continuous distribution can be manifested as a local deflection area extending along the middle of the bottom plate or the connection between the bottom plate and the side plate; for the module mounting base section, the continuous distribution can be manifested as a local deformation area in the same direction between the root of the mounting base and the adjacent bottom plate.

[0080] For ease of explanation, the continuous distribution of local vibration mode deformation in the box section to be judged can be determined according to the following formula:

[0081]

[0082] In the formula, For the first The undetermined enclosure section is in the first... Local mode shape concentration factor under a single mode shape; For the first The continuous local deformation areas within the undetermined box section are in the first... Average displacement amplitude under the mode shape; For the first The undetermined enclosure section is in the first... The average displacement amplitude under the first mode shape; the continuous local deformation region is the first... A region within a box section to be judged, consisting of adjacent nodes, adjacent units, or adjacent shell areas, and sharing a consistent main vibration and deformation direction. When The preset centralized judgment condition is met, and the continuous local deformation region is in the first... When the partition of the box to be judged has continuous geometric coverage, the first... The undetermined enclosure section is in the first... The mode shape is denoted as a box section with a continuous distribution of local mode shape deformation. The preset centralized judgment conditions can be determined based on the modal verification experience of similar box samples, the modal margin requirements in the design specifications, or the response dispersion of each box section in the same model, and do not need to be limited to fixed values.

[0083] When identifying box-type zones with continuous distribution of localized mode deformation, it is also necessary to consider the direction of vibration deformation. If a box-type zone to be judged only has a single isolated node with a sudden increase in displacement amplitude, and surrounding nodes or adjacent units do not form a continuous deformation area, this box-type zone is not considered a vibration concentration zone. If a high displacement amplitude area in a box-type zone to be judged is continuously distributed along the plate, bending transition, or mounting base root, and the main vibration deformation direction is consistent with or continuously transitions with adjacent positions, this box-type zone can be identified as a vibration concentration zone. For continuous localized deformation areas spanning more than two box-type zones to be judged, the continuous coverage within each box-type zone to be judged should be determined separately; if the continuous coverage is concentrated within one box-type zone to be judged, that box-type zone to be judged is identified as a vibration concentration zone; if the continuous coverage occupies two adjacent box-type zones to be judged simultaneously, both box-type zones to be judged are identified as vibration concentration zones.

[0084] After the above determination is completed, the box section where vibration concentration occurs is identified as a modal migration weak area. The determination of the modal migration weak area requires the simultaneous fulfillment of two conditions: first, the box section does not belong to the initial weak area determined in step 100; second, the box section has a continuous distribution of local modal deformations in the optimized modal distribution. Therefore, the modal migration weak area corresponds to a newly emerging or significantly shifted vibration concentration location after the first structural optimization, rather than a weak location already exposed in the initial structural response. Subsequent step 500 uses the modal migration weak area and the adjacent connection transition area as the secondary optimization design domain, and can directly inherit the determination result of step 400.

[0085] In step 500, the connection boundary is first determined based on the modal migration weak zone identified in step 400. The connection boundary is not the outer contour boundary of the model, but rather the structural interface between the modal migration weak zone and the adjacent box section where load transfer or modal deformation transfer actually occurs. Specifically, it can be a plate bend, a connection between a side plate and a bottom plate, the root of the mounting base, a transition point at the end of a reinforcing rib, or a connection overlap between adjacent plates. If the modal migration weak zone is located in the lower box side plate section, the interface between the lower box side plate section and the lower box bottom plate section, the box top cover section, or the module mounting base section is used as a candidate connection boundary. If the modal migration weak zone is located in the lower box bottom plate section, the interface between the lower box bottom plate section and the lower box side plate section, or the module mounting base section is used as a candidate connection boundary. If the modal migration weak zone is located in the module mounting base section, the interface between the module mounting base section and the lower box bottom plate section or the adjacent reinforcing structure is used as a candidate connection boundary.

[0086] When determining the adjacent connection transition zone, not all adjacent box sections are included in the secondary optimization design domain. Instead, structural regions that bear the modal deformation transfer of the weak modal migration zone are selected from the candidate connection boundaries. Specifically, candidate transition zones can be formed by extending along the candidate connection boundaries into the adjacent box sections, and whether a candidate transition zone belongs to the adjacent connection transition zone is determined based on the connection scale and modal deformation correlation between the candidate transition zone and the weak modal migration zone. In one embodiment, the following formula is used to determine the first... Mode transfer participation of each candidate transition zone:

[0087]

[0088] in, For the first Mode transfer participation in each candidate transition zone; For the first The effective connection scale between the candidate transition zone and the weak zone of the mode migration, wherein the effective connection scale is the equivalent value of the connection boundary length or the connection area; This is the sum of the effective connection dimensions between the weak region of the mode migration and each candidate transition region; For the first The average modal displacement amplitude of each candidate transition zone near the connection boundary; This represents the average modal displacement amplitude in the weak region of modal migration. When the... When the modal transmission participation of the candidate transition zone reaches the preset participation judgment condition, the first... Each candidate transition zone is determined as an adjacent connection transition zone. The preset participation determination criteria can be determined based on the ranking of the mode transfer participation of each candidate transition zone in the same model, the importance of the box structure parts, or the connection form of adjacent plates.

[0089] When determining the secondary optimization design domain, the weak area of ​​modal migration and the already selected adjacent connection transition area are jointly used as the secondary optimization design domain. The adjacent connection transition area may include at least one of the side plate transition area, bottom plate transition area, and mounting seat proximity area. The side plate transition area mainly corresponds to the plate wall area, bending area, or vertical reinforcement area near the connection boundary in the lower box side plate partition; the bottom plate transition area mainly corresponds to the local area of ​​the bottom plate or the bottom plate reinforcement area near the connection boundary in the lower box bottom plate partition; the mounting seat proximity area mainly corresponds to the root of the module mounting seat partition and the local area of ​​the bottom plate connected to the mounting seat. The scope of the secondary optimization design domain is based on the continuous distribution area of ​​local modal deformation in the weak area of ​​modal migration and the main deformation transmission area in the adjacent connection transition area, excluding the far-end box partitions unrelated to modal deformation transmission from the secondary optimization design domain.

[0090] When performing local structural optimization on the secondary optimization design domain, the local structural optimization parameters in the secondary optimization design domain are updated while maintaining the installation boundaries of the battery pack housing, the module installation positioning boundaries, and the outer envelope constraints of the housing. These local structural optimization parameters include at least one of local plate thickness parameters, local ply parameters, and local reinforcement structure parameters. For secondary optimization design domains located in the plate area, the local plate thickness parameters or local ply parameters can be adjusted to match the local bending stiffness of the plate area with the stiffness change of the adjacent connection transition zone. For secondary optimization design domains located at the bending transition or the root of the mounting base, the local reinforcement structure parameters can be adjusted to ensure that the end extension direction of the reinforcement structure corresponds to the vibration deformation direction, and to prevent the end of the reinforcement structure from terminating directly at a high vibration concentration position. The local structural optimization aims to reduce the degree of local mode shape deformation concentration in the secondary optimization design domain, while simultaneously constraining the stiffness change between the weak mode shape migration area and the adjacent connection transition zone to remain continuous, avoiding the formation of new stiffness abrupt changes at the connection boundary after individually reinforcing the weak mode shape migration area.

[0091] After completing the local structural optimization, the corresponding regions in the first optimized box model are replaced with the updated secondary optimization design domain to obtain the second optimized box model. During the replacement process, the modal migration weak areas, the adjacent connection transition areas, and the secondary optimization design domain still use the box partition identifiers from step 100, so that the second optimized box model can continue to maintain the same structural part correspondence as the initial finite element model and the first optimized box model. For box partitions not included in the secondary optimization design domain, the second optimized box model retains the corresponding structures in the first optimized box model; for areas included in the secondary optimization design domain, the second optimized box model adopts updated local plate thickness parameters, local ply parameters, or local strengthening structural parameters. Thus, the second optimized box model does not regenerate the entire box structure, but rather completes local corrections for the modal migration weak areas and adjacent connection transition areas based on the first optimized box model.

[0092] Further, in one embodiment of step 600, based on the second optimized housing model obtained in step 500, structural design parameters related to the actual manufacturing and structural definition of the battery pack housing are extracted. Specifically, the structural parameters of the housing top cover include the location of local reinforcement structures in the housing top cover partition, the extension direction of the local reinforcement structures, the forming contour of the local reinforcement structures, and the plate thickness settings of the housing top cover partition; the structural parameters of the lower housing include the plate thickness distribution, ply distribution, arrangement of local reinforcement structures, and structural form of the mounting support parts in the lower housing bottom plate partition, lower housing side plate partition, and module mounting base partition; the structural parameters of the secondary optimization design domain include local plate thickness parameters, local ply parameters, or local reinforcement structure parameters in the mode shape migration weak area, as well as the connection transition area parameters in the adjacent connection transition area. All of the above parameters are derived from the structural parts in the second optimized housing model that have already undergone local structural optimization, and no control parameters unrelated to the housing structure are introduced separately.

[0093] When organizing the structural parameters of the upper cover, lower box, and secondary optimization design domain, the structural parameters are categorized according to the box structure parts determined in step 100. Parameters belonging to the upper cover partition are organized as upper cover structural parameters; parameters belonging to the lower box bottom plate partition, lower box side plate partition, or module mounting base partition are organized as lower box structural parameters; and parameters belonging to the modal migration weak zone and adjacent connection transition zone determined in step 500 are organized as secondary optimization design domain structural parameters. When the same structural part belongs to both the lower box structural parameters and the secondary optimization design domain structural parameters, the secondary optimization design domain structural parameters are used as the final local parameters for that structural part, and the corresponding box partition identifier is retained in the parameter record. Through this organization method, various structural adjustments in the second optimized box model can be returned to specific box structural parts, avoiding local reinforcement structures, plate thickness distribution, and ply distribution becoming isolated parameters without a clear affiliation in the specification.

[0094] When determining the structural design parameters of the battery pack enclosure based on the processing results, at least one of the following parameters—local reinforcement structure layout parameters, plate thickness distribution parameters, ply distribution parameters, and connection transition zone parameters—is used as the final structural design parameters. The local reinforcement structure layout parameters define the specific structural locations of the reinforcement structure within the enclosure's upper cover zone, lower enclosure bottom plate zone, lower enclosure side plate zone, module mounting base zone, or secondary optimization design domain. The plate thickness distribution parameters define the plate thickness variation relationships between different enclosure zones. The ply distribution parameters define the ply position and ply direction of the composite material region. The connection transition zone parameters define the transition structure range, transition plate thickness relationship, or transition reinforcement structure layout between the mode shape migration weak zone and the adjacent connection transition zone. Therefore, the battery pack enclosure structural design parameters determined in step 600 are not simply saved model results, but rather form a set of structural parameters that can be used for subsequent structural modeling, prototype design, or drawing representation.

[0095] In another implementation, step 600 further includes a structural response verification of the second optimized box model. The structural response verification can be performed using the same box partitioning system as steps 100 and 300, and the verification content includes stress concentration, displacement concentration, and modal distribution in the second optimized box model. Verifying the structural response is used to determine whether, after secondary optimization, the second optimized box model still has box partitions located outside the secondary optimization design domain that form vibration concentration areas. If the verified structural response shows that the new vibration concentration area is still within the original secondary optimization design domain, it indicates that the local structural optimization in step 500 has corresponded to the previously identified weak area of ​​mode migration; if the verified structural response shows that the vibration concentration area has shifted to other box partitions outside the secondary optimization design domain, then this box partition is not directly included in the final structural design parameters, but instead enters the new weak area of ​​mode migration determination.

[0096] When a box-type partition with concentrated vibration is found outside the secondary optimization design domain in the structural response during verification, this box-type partition is updated as a new weak area for modal migration, and a new secondary optimization design domain is redefined according to step 500. When redefining the new secondary optimization design domain, the scope remains the new weak area for modal migration and the adjacent transition area connected to it, without expanding to repeated optimization of the entire box. When no box-type partition with concentrated vibration is found outside the secondary optimization design domain in the structural response during verification, the structural design parameters of the battery pack box are determined based on the second optimized box model. The above verification process can be used as a supplementary implementation in step 600 to confirm that the vibration concentration after secondary optimization has not continued to migrate to other box-type partitions. After successful verification, the structural parameters of the upper cover, lower box, and secondary optimization design domain in the second optimized box model together constitute the final structural design parameters of the battery pack box.

[0097] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0098] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A battery pack case optimization design method based on Optistruct, characterized in that, include: Obtain the initial finite element model of the battery pack enclosure, divide the enclosure into sections according to the structural parts of the enclosure, and determine the initial weak areas based on the structural response of the initial finite element model. Using the initial weak area as the first optimization object, the battery pack housing is structurally optimized using Optistruct to obtain the first optimized housing model; Modal verification is performed on the first optimized box model to obtain the optimized modal distribution of each box partition; Based on the optimized modal distribution, the box section located outside the initial weak region and forming a vibration concentration is identified as the mode migration weak region; Using the weak zone of the mode migration and the adjacent connection transition zone connected to the weak zone of the mode migration as the secondary optimization design domain, the second optimized box model is obtained by performing local structural optimization on the secondary optimization design domain through Optistruct. The structural design parameters of the battery pack enclosure are determined based on the second optimized enclosure model.

2. The Optistruct-based battery pack case optimization design method of claim 1, wherein, The enclosure is divided into sections according to its structural components, including: The battery pack housing is divided into a housing top cover section, a lower housing bottom plate section, a lower housing side plate section, and a module mounting base section. Set partition identifiers for each of the aforementioned enclosure partitions; The partition identifier corresponds to the same box structure part in the initial finite element model, the first optimized box model, and the second optimized box model.

3. The Optistruct-based battery pack enclosure optimization design method of claim 1, wherein, The initial weak regions are determined based on the structural response of the initial finite element model, including: According to each of the box sections, obtain the stress concentration results, displacement concentration results, and low-order mode concentration results in the structural response; The box section containing the stress concentration result, the displacement concentration result, or the low-order mode concentration result is identified as a candidate weak section. The candidate weak partitions that are interconnected and belong to the same bearer transmission path are merged into the initial weak region.

4. The Optistruct-based battery pack enclosure optimization design method of claim 1, wherein, Using the initial weak area as the primary optimization target, the battery pack housing is structurally optimized using Optistruct to obtain a first optimized housing model, including: Based on the location of the initial weak area in the box structure, an optimization design domain is determined in Optistruct; The topography of the first-order optimization design domain located on the top cover of the box is optimized to obtain a local reinforcement structure for the top cover; The primary optimization design domain located in the lower box is subjected to size optimization, ply optimization, or local reinforcement optimization to obtain the local load-bearing structure of the lower box. The first optimized box model is obtained based on at least one of the above-top partial reinforcement structure and the below-box partial load-bearing structure.

5. The battery pack housing optimization design method based on Optistruct according to claim 1, characterized in that, Modal verification is performed on the first optimized box model to obtain the optimized modal distribution of each box partition, including: Multimodal analysis was performed on the first optimized box model to obtain the vibration modes of each order; Identify the vibration concentration location and vibration deformation direction in each of the described vibration modes according to the respective box-type partitions; The vibration concentration location and the vibration deformation direction are associated with the corresponding box partition to form the optimized modal distribution.

6. The battery pack housing optimization design method based on Optistruct according to claim 1, characterized in that, Based on the optimized modal distribution, the box section located outside the initial weak region and forming a vibration concentration is identified as the modal migration weak region, including: Remove the box sections that belong to the initial weak area from each of the box sections; Based on the optimized modal distribution, determine the remaining box-shaped partitions that have a continuous distribution of local mode deformation. The box section with the continuous distribution of local mode deformation is taken as the box section where vibration is concentrated, and is identified as the weak area of ​​mode migration.

7. The battery pack housing optimization design method based on Optistruct according to claim 1, characterized in that, The secondary optimization design domain is defined by the weak region of modal migration and the adjacent connection transition region connected to the weak region of modal migration, including: Determine the connection boundary between the weak zone of the vibration mode migration and the adjacent box section; Based on the connection boundary, at least one of the side plate transition area, the bottom plate transition area, and the mounting base adjacent area that bears the modal deformation transmission of the modal migration weak area is determined as the adjacent connection transition area; The weak zone of mode migration and the adjacent connection transition zone are defined as the secondary optimization design domain.

8. The battery pack housing optimization design method based on Optistruct according to claim 1, characterized in that, The second optimized box model is obtained by performing local structural optimization on the secondary optimization design domain using Optistruct, including: In Optistruct, the secondary optimization design domain is set as a local optimization region; With the optimization constraint of reducing vibration concentration in the secondary optimization design domain and maintaining stiffness transition in the adjacent connection transition zone, the local structural optimization parameters of the secondary optimization design domain are updated. The local structural optimization parameters include at least one of local plate thickness parameters, local ply parameters, and local reinforcement structural parameters. The corresponding region in the first optimized box model is replaced with the updated secondary optimized design domain to obtain the second optimized box model.

9. The battery pack housing optimization design method based on Optistruct according to claim 1, characterized in that, Based on the second optimized enclosure model, the structural design parameters of the battery pack enclosure are determined, including: Obtain the structural parameters of the upper cover, lower box, and secondary optimization design domain from the second optimized box model; The structural parameters of the upper cover, the lower cover, and the secondary optimization design domain are organized according to the structural parts of the box. Based on the sorting results, the structural design parameters of the battery pack housing are determined. The structural design parameters of the battery pack housing include at least one of the following: local reinforcement structure arrangement parameters, plate thickness distribution parameters, ply distribution parameters, and connection transition zone parameters.

10. A battery pack housing optimization design method based on Optistruct according to claim 1, characterized in that, Determining the structural design parameters of the battery pack housing based on the second optimized housing model also includes: The structural response of the second optimized box model was verified to obtain the verified structural response. When there is a box section in the verification structure response that is outside the secondary optimization design domain and forms a vibration concentration, the box section is updated as a new weak area of ​​mode migration, and the secondary optimization design domain is redefined. When there is no box section outside the secondary optimization design domain that forms a vibration concentration in the verification structural response, the structural design parameters of the battery pack box are determined according to the second optimized box model.

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