A method for optimizing design of a sweating cooling structure based on gradient TPMS and a structure

Abstract

The application provides a sweating cooling structure optimization design method based on a gradient TPMS, comprising the following steps: constructing a uniform TPMS sweating cooling structure model; applying a preset service load to the uniform structure model, solving by using a pre-constructed damage analysis model, obtaining a cumulative damage field, and identifying a damage concentration area in a boundary transition area according to the cumulative damage field; mapping the cumulative damage field of the damage concentration area into a continuously changing wall thickness field, and the wall thickness value of the wall thickness field is positively correlated with the cumulative damage value of the corresponding position of the wall thickness field; adjusting the boundary transition area based on the continuously changing wall thickness field to obtain a gradient TPMS sweating cooling structure model. The application focuses on the boundary transition area between the TPMS porous section and the solid section, drives the wall thickness gradient design by using the cumulative damage field, positively correlates the wall thickness with the damage, avoids the limitation of the transient stress optimization, accurately relieves the damage concentration in the boundary area, and significantly improves the durability of the sweating cooling structure.

Description

Technical Field

[0001] This invention relates to the field of porous material structure optimization design, and in particular to a method and structure for optimizing a sweating cooling structure based on gradient TPMS. Background Technology

[0002] Sweating cooling is a highly efficient thermal protection method that uses a porous medium to uniformly deliver a cooling medium to a high-temperature wall surface, thereby forming a cooling protective layer near the wall surface. With the development of additive manufacturing technology, TriplyPeriodic Minimal Surface (TPMS) structures are widely used in sweating cooling, heat exchangers, lightweight load-bearing structures, and thermal protection structures due to their continuous smooth surfaces, high specific surface area, high interconnected porosity, and good mechanical load-bearing capacity. Unlike traditional lattice structures, TPMS structures have continuous pore walls and no obvious node connection defects, which can improve stress distribution and enhance fluid channel continuity to a certain extent.

[0003] Current mass-produced sweating cooling components generally employ a uniform TPMS structure with consistent wall thickness throughout, consisting of porous TPMS segments spliced ​​together with dense solid segments at both ends. The solid segments are dense and have high stiffness, while the porous TPMS segments are densely packed with pores and have relatively low equivalent stiffness. Due to significant differences in geometry, relative density, local stiffness, and thermal expansion response between the porous and solid TPMS segments, the transition zone between them is prone to localized stress concentration, plastic strain concentration, and damage concentration. Under long-term thermo-mechanical loading, the transition zone between the porous and solid TPMS segments often experiences abrupt changes in geometric stiffness, inducing localized stress concentration and becoming a dangerous area for crack initiation and structural failure.

[0004] Current optimization techniques use instantaneous stress values ​​as the benchmark, reducing peak stress by altering porosity and dimensions. However, instantaneous stress only represents the stress state at a single load step and cannot characterize the ductile cumulative damage caused by irreversible plastic accumulation and the growth of micropores in metallic materials. Under actual working conditions, instantaneous stress may not exceed allowable values ​​at some locations, but continuous plastic accumulation and damage buildup during long-term cyclic service lead to damage aggregation and microcrack initiation in the transition zone, ultimately causing premature failure of the sweating cooling structure.

[0005] Therefore, how to provide an optimized design method for a sweating cooling structure that relies on the cumulative damage field to drive the wall thickness gradient and effectively alleviate the concentration of cumulative damage in the transition zone between the porous and solid sections of TPMS is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this application is to provide an optimization design method and structure for a sweating cooling structure based on gradient TPMS. The optimization design method for a sweating cooling structure based on gradient TPMS provided in this application overcomes the technical problems of existing uniform TPMS sweating cooling structures, such as the accumulation of damage and premature crack initiation failure caused by the incoordination of stiffness and thermal deformation in the transition zone between the porous and solid sections of TPMS during service, as well as the misalignment between the optimization results and the actual damage danger area in traditional optimization.

[0007] The purpose of this invention is to provide an optimized design method for a sweating cooling structure based on gradient TPMS; The technical solution provided by this invention is as follows: An optimization design method for sweating cooling structures based on gradient TPMS includes: A uniform TPMS sweating and cooling structure model is constructed, which includes at least a porous TPMS segment, a solid segment, and a transition zone between the porous TPMS segment and the solid segment. A preset service load is applied to the uniform TPMS sweating cooling structure model, and the cumulative damage field is obtained by solving the pre-constructed damage analysis model. The damage concentration area in the boundary transition zone is then identified based on the cumulative damage field. The cumulative damage field of the damage concentration area is mapped to a continuously varying wall thickness field, and the wall thickness value of the wall thickness field is positively correlated with the cumulative damage value at the corresponding position of the wall thickness field. The boundary transition zone is adjusted based on the continuously changing wall thickness field to obtain a gradient TPMS sweating cooling structure model.

[0008] Preferably, the damage analysis model is an elastoplastic-damage coupled constitutive model; The elastoplastic-damage coupled constitutive model includes the J2 isotropic hardening plastic sub-model and the Lemaitre ductile damage evolution sub-model; The J2 isotropic hardening plastic sub-model is used to describe the plastic deformation process of the material in the sweating cooling structure; The Lemaitre ductile damage evolution sub-model is used to describe the cumulative damage evolution process of the material in the sweating cooling structure during plastic deformation.

[0009] Preferably, the preset service load includes strain increment and temperature increment; The J2 isotropic hardening plastic sub-model is used to obtain the effective equivalent stress, cumulative equivalent plastic strain, and equivalent plastic strain increment based on the strain increment and the temperature increment.

[0010] Preferably, the Lemaitre ductile damage evolution sub-model is used to obtain the cumulative damage field based on the effective equivalent stress, the cumulative equivalent plastic strain, and the equivalent plastic strain increment.

[0011] Preferably, mapping the cumulative damage field of the damage concentration area to a continuously varying wall thickness field includes: The cumulative damage field within the damage concentration area is normalized to obtain a normalized damage variable. The normalized damage variable is mapped using a preset mapping function to obtain the initial wall thickness field; The initial wall thickness field is smoothed and subjected to geometric continuity constraints to obtain the continuously varying wall thickness field.

[0012] Preferably, the preset mapping function is specifically:

[0013] In the formula, Let x be the local wall thickness value at position x in the boundary transition zone. This is the minimum allowable wall thickness value. This is the maximum permissible wall thickness value; The normalized damage variable is denoted as .

[0014] Preferably, after adjusting the boundary transition zone based on the continuously varying wall thickness field to obtain the gradient TPMS sweating cooling structure model, the method further includes: Under the same service load, damage comparison analysis is performed on the gradient TPMS sweating cooling structure model and the uniform TPMS sweating cooling structure model to obtain the damage optimization effect. If the damage optimization effect meets the preset cooling mitigation index, the target gradient transition TPMS sweating cooling structure is obtained.

[0015] Preferably, the damage optimization effect meets a preset cooling mitigation index, including: The maximum damage value of the transition zone of the gradient TPMS sweating cooling structure model is lower than that of the uniform TPMS sweating cooling structure model. The damage distribution in the transition zone of the gradient TPMS sweating cooling structure model is uniform, and there are no newly added damage concentration areas.

[0016] Preferably, before constructing the uniform TPMS sweating cooling structure model, the method further includes: The structure of the uniform TPMS sweating cooling structure model is determined; wherein the structure of the uniform TPMS sweating cooling structure model includes one or more of the Diamond, Gyroid, Schwarz P or I-WP structures.

[0017] The second objective of this invention is to provide a gradient TPMS sweating cooling structure; The technical solution provided by this invention is as follows: A gradient TPMS sweating cooling structure, the sweating cooling structure being designed based on the aforementioned gradient TPMS-based sweating cooling structure optimization design method, the sweating cooling structure comprising: The TPMS porous segment, the solid segment, and the boundary transition zone between the TPMS porous segment and the solid segment; wherein the boundary transition zone is a transition zone with a continuously changing gradient, and the wall thickness value at any point in the boundary transition zone is positively correlated with the cumulative damage value generated at that point under a preset service load.

[0018] This invention provides an optimization design method for a sweating cooling structure based on gradient TPMS, comprising: A uniform TPMS sweating cooling structure model is constructed. A preset service load is applied to the uniform TPMS sweating cooling structure model, and a pre-constructed damage analysis model is used to solve the problem, obtaining the cumulative damage field. Based on the cumulative damage field, damage concentration areas in the transition zone are identified. The cumulative damage field of the damage concentration areas is mapped to a continuously varying wall thickness field, where the wall thickness value is positively correlated with the cumulative damage value at the corresponding position. The transition zone is adjusted based on the continuously varying wall thickness field to obtain a gradient TPMS sweating cooling structure model. Compared to existing technologies, this invention focuses on the transition zone between the porous and solid sections of the TPMS, using the cumulative damage field to drive the wall thickness gradient design, making the wall thickness positively correlated with damage. This avoids the limitations of instantaneous stress optimization, thereby accurately alleviating damage concentration in the transition zone and significantly improving the durability of the sweating cooling structure.

[0019] This invention also provides a gradient TPMS sweating cooling structure, which solves the structural defects of uniform TPMS sweating cooling structures, such as the lack of damage correlation in wall thickness and the susceptibility to damage and failure in the transition zone. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of an optimized design method for a sweating cooling structure based on gradient TPMS in an embodiment of the present invention; Figure 2The load and damage distribution cloud diagrams of a uniform Diamond TPMS structure without gradient transition in the embodiments of the present invention are as follows: (a) stress, (b) strain, (c) damage, (d) equivalent plastic strain; Figure 3 The load and damage distribution cloud diagrams of the gradient transition Diamond TPMS structure in the embodiments of the present invention are as follows: (a) stress, (b) strain, (c) damage, and (d) equivalent plastic strain. Figure 4 The following are comparison diagrams of the maximum load damage of a uniform Diamond TPMS structure without gradient transition and a Diamond TPMS structure with gradient transition in the embodiments of the present invention: (a) maximum stress comparison, (b) maximum strain comparison, (c) maximum damage comparison, (d) maximum equivalent plastic strain comparison. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] like Figure 1 As shown, this embodiment of the invention provides an optimization design method for a sweating cooling structure based on gradient TPMS, including: S1. Construct a uniform TPMS sweating cooling structure model. The uniform TPMS sweating cooling structure model shall include at least a porous TPMS segment, a solid segment, and a transition zone between the porous TPMS segment and the solid segment. In this embodiment, implicit modeling software, such as nTop, is used to establish a three-dimensional model of a sweating cooling structure with uniform wall thickness based on the implicit surface equations of the TPMS (Porous TPMS) structure selected according to the actual working conditions. The model is sequentially configured along the loading direction as a solid segment, a porous TPMS segment, and another solid segment, with a reserved transition zone at the connection between the porous TPMS segment and each solid segment. The geometric characteristics of the transition zone are between those of a periodic porous structure and a fully dense solid structure, and its wall thickness is consistent with that of the porous TPMS segment. By constructing the transition zone, the scope of subsequent gradient design is focused on the region with the most drastic stiffness change, avoiding unnecessary computational overhead caused by comprehensive modifications to the overall structure. This provides a quantifiable and subsequently optimizable basic structural model, enabling high-risk damage areas in the structure to be accurately captured in finite element analysis, laying the geometric foundation for damage-driven gradient design.

[0024] Preferably, before constructing the uniform TPMS sweating cooling structure model, the following steps are also included: Determine the structure of the uniform TPMS sweating cooling structure model; wherein the structure of the uniform TPMS sweating cooling structure model includes one or more of the Diamond, Gyroid, Schwarz P or I-WP structures.

[0025] In this embodiment, based on the specific application scenario and performance requirements of the sweating cooling structure, one or more TPMS structures such as Diamond, Gyroid, Schwarz P, or I-WP are selected as the geometric basis for the porous section. For example, when higher heat transfer efficiency and flow capacity are required, the Diamond structure is preferred; when isotropic mechanical load-bearing capacity is required, the Schwarz P structure is preferred; and when continuous and unobstructed fluid channels are required, the Gyroid structure is preferred. Different TPMS types have different surface curvatures, pore connectivity, and stiffness characteristics. Selecting a suitable structural type can lay a favorable geometric foundation for subsequent damage mitigation in the early stages of design, enabling the final designed gradient TPMS sweating cooling structure to simultaneously consider cooling performance, mechanical load-bearing capacity, and damage mitigation effects, thus improving the adaptability and flexibility of the method to different operating conditions.

[0026] In one specific implementation, the uniform TPMS sweating cooling structure model constructed in step S1 is a DiamondTPMS structure. The implicit surface equation of the Diamond TPMS is:

[0027] Where C is the isosurface constant. By adjusting C, the porosity, wall thickness, and relative density of the Diamond TPMS structure can be changed.

[0028] A uniform Diamond TPMS sweating cooling structure model was established using nTop software based on the aforementioned implicit surface equations. This structure, along the loading direction, includes a central porous Diamond TPMS segment, two solid segments at either end, and a transition zone between them. The transition zone is the location where the stiffness and geometry of the porous TPMS segment and the solid segment undergo significant changes, and it is also the target area for subsequent damage mitigation design in this invention.

[0029] After completing the geometric modeling, the model was meshed using Magics preprocessing software, and an .inp file readable by Abaqus was exported. The finite element model must retain the complete geometric features of the TPMS porous segment, solid segment, and transition zone to accurately analyze the stress, plastic strain, and damage distribution in the transition zone.

[0030] S2. Apply a preset service load to the uniform TPMS sweating cooling structure model, solve the problem using the pre-built damage analysis model to obtain the cumulative damage field, and identify the damage concentration area in the boundary transition zone based on the cumulative damage field. In this embodiment, the finite element model of the uniform TPMS structure established in step S1 is imported into the solver, and mechanical and / or thermal loads corresponding to the actual service state of the sweating cooling structure are applied. Using a pre-constructed damage analysis model, such as a constitutive model based on continuous damage mechanics, incremental step-by-step solving is performed, updating the cumulative damage variable at each integration point. After the solution is completed, the cumulative damage field of the entire structure is output. By observing the spatial distribution of the damage field, locations where the damage variable values ​​in the transition zone are significantly higher than those in the surrounding area are identified as damage concentration zones. The cumulative damage field comprehensively reflects the accumulation of plastic deformation and stiffness degradation of the material during the loading history, and is more representative of the actual failure risk of the structure than the instantaneous stress field. It can accurately locate the most likely dangerous area to fail in a uniform structure, providing a quantitative basis for the spatial location and damage degree for subsequent targeted gradient design, avoiding the blindness of judging dangerous areas based on experience in traditional methods.

[0031] Preferably, the damage analysis model is an elastoplastic-damage coupled constitutive model; The elastoplastic-damage coupled constitutive model includes the J2 isotropic hardening plastic sub-model and the Lemaitre ductile damage evolution sub-model; The J2 isotropic hardening plastic submodel is used to describe the plastic deformation process of materials in sweating cooling structures; The Lemaitre ductile damage evolution sub-model is used to describe the cumulative damage evolution process of materials in sweat-cooled structures during plastic deformation.

[0032] In this embodiment, the damage analysis model is an elastoplastic-damage coupled constitutive model, which unifies the plastic deformation and damage degradation of the material within the same constitutive framework. This model includes: the J2 isotropic hardening plasticity sub-model and the Lemaitre ductile damage evolution sub-model. The J2 sub-model is a metal plasticity model based on von Mises equivalent stress, used to describe the plastic deformation behavior of the material after yielding. Isotropic hardening indicates that the material's yield surface expands uniformly with the accumulation of equivalent plastic strain. The Lemaitre sub-model is a continuous damage mechanics model that uses damage variables to describe the weakening of load-bearing capacity due to the accumulation of irreversible damage such as micropores and microcracks within the material. Based on the von Mises yield criterion and the isotropic hardening rule, the J2 sub-model is responsible for determining whether the material has entered a plastic state and calculating the plastic strain and accumulated equivalent plastic strain. The Lemaitre ductile damage evolution sub-model is activated after plastic accumulation reaches a certain threshold, quantifying the evolution of micro-defects within the material through damage variables. The two sub-models are coupled in the order of "plasticity first, damage later". The results of plasticity calculation are used as input for damage calculation, and the damage variables are fed back to the stress update for stiffness degradation. This allows the finite element analysis to output both the plastic region and the damage region at the same time. The cumulative damage field directly reflects the evolution history of material failure and provides a more accurate driving force for subsequent gradient wall thickness mapping than simple plastic strain or instantaneous stress.

[0033] Preferably, the preset service load includes strain increment and temperature increment; The J2 isotropic hardening plastic submodel is used to obtain the effective equivalent stress, cumulative equivalent plastic strain, and equivalent plastic strain increment based on the strain increment and temperature increment.

[0034] In this embodiment, in each finite element increment step, the J2 sub-model first receives the strain increment Δε and temperature increment ΔT from the solver. The mechanical strain increment is obtained by subtracting the thermal strain increment (calculated from the coefficient of thermal expansion and ΔT). Then, an elastic test is performed to calculate the test stress and von Mises equivalent stress. The yield function is used to determine whether the current integration point has entered the plastic state. If it has entered the plastic state, the equivalent plastic strain increment is iteratively solved using a radial regression algorithm, and the cumulative equivalent plastic strain and effective equivalent stress are updated accordingly. This accurately accounts for the cumulative plastic deformation under the thermo-mechanical coupling effect, providing key parameters related to the elastoplastic change for the Lemaitre sub-model, thereby improving the accuracy and reliability of the cumulative damage field calculation.

[0035] In practical applications, the J2 sub-model first uses strain decomposition relationships to describe the composition of the total strain of the material. The total strain is decomposed as follows:

[0036] in, For the total strain tensor, For elastic strain tensor, For plastic strain tensor, This is the thermal strain tensor. When only isothermal mechanical loads are considered, the thermal strain term can be taken as zero or treated as the initial thermal strain.

[0037] After obtaining the elastic strain, the effective stress is calculated using the elastic relationship in the effective stress space:

[0038] in, For the effective stress tensor, This is the elastic stiffness matrix.

[0039] Subsequently, the J2 yield function is used to determine whether the material has entered the plastic state. The J2 yield function is:

[0040] Where f is the yield function, The von Mises equivalent stress in effective stress space. The yield stress varies with equivalent plastic strain. This represents the equivalent plastic strain. The formula takes the effective equivalent stress and the current yield stress as inputs and outputs the yield threshold value f. When f ≤ 0, the current integration point is in an elastic state; when f > 0, the current integration point enters a plastic state and requires plastic correction. The effective equivalent stress is calculated according to the von Mises criterion, and its expression is as follows:

[0041] in, The deviatoric stress component of the effective stress tensor is represented by a colon (:), which indicates the tensor double dot product. This formula takes the effective deviatoric stress tensor as input and outputs the effective equivalent stress. This is used to substitute into the J2 yield function for yield determination.

[0042] When a material enters a plastic state, the plastic strain is updated according to the plastic flow law:

[0043] in, For the plastic multiplier increment, This represents the increment of plastic strain. The formula takes the plastic multiplier increment and the direction of plastic flow as inputs, and outputs the increment of plastic strain. This output is further used to update the plastic strain and cumulative equivalent plastic strain, and serves as an important input for subsequent damage evolution calculations.

[0044] The effective stress, plastic strain increment, plastic strain, cumulative equivalent plastic strain, and yield state judgment results for the current increment step can be obtained from the J2 sub-model described above.

[0045] Preferably, the Lemaitre ductile damage evolution sub-model is used to obtain the cumulative damage field based on the effective equivalent stress, cumulative equivalent plastic strain, and equivalent plastic strain increment.

[0046] In this embodiment, the Lemaitre sub-model receives the effective equivalent stress, cumulative equivalent plastic strain, and equivalent plastic strain increment output by the J2 sub-model as input. First, it determines whether the cumulative equivalent plastic strain exceeds a preset damage initiation threshold: if it does not, the damage increment for this increment step is zero; if it does, the damage driving force Y is calculated according to the damage driving force formula, and then the damage increment ΔD for the current increment step is calculated using the damage evolution law. Finally, the damage variables are updated. = +ΔD. The above calculation is performed independently at each finite element integration point to obtain the damage variable value at that point. After post-processing interpolation, the damage variables at all integration points form a spatially distributed cumulative damage field D(x). It should be noted that the damage does not occur instantaneously, but rather evolves gradually with the accumulation of plasticity; the Lemaitre sub-model links the current stress level with the plasticity increment through the damage driving force, truly reflecting the physical mechanism of ductile damage. The obtained cumulative damage field not only identifies regions in the structure where stiffness degradation has occurred, but its magnitude is also positively correlated with the degree of plastic damage experienced by that region during the loading history, thus providing a directly quantifiable basis for subsequently mapping the damage value to the wall thickness gradient.

[0047] In practical applications, the effective stress and cumulative equivalent plastic strain increment are further input into the Lemaitre ductile damage sub-model to calculate the damage driving force and damage increment. The Lemaitre ductile damage sub-model uses the damage variable D to describe the weakening of load-bearing capacity due to the accumulation of irreversible damage such as micropores and microcracks within the material. In this model, the nominal stress and effective stress satisfy the following relationship:

[0048] in, For nominal stress, The effective stress is represented by D, which is the damage variable. D=0 indicates that the material is not damaged; the larger the D is, the more severe the degradation of the material's load-bearing capacity.

[0049] Damage evolution is controlled by damage driving forces, which are:

[0050] Where Y is the damage driving force, which characterizes the driving effect of the current stress state on damage growth; and E is Young's modulus.

[0051] When the cumulative equivalent plastic strain exceeds the damage initiation threshold, the damage evolves according to the following formula:

[0052] when hour:

[0053] in, For the increase in damage, Here, s is the damage intensity parameter, and s is the damage index. The damage initiation threshold, This represents the equivalent plastic strain increment. When the cumulative equivalent plastic strain has not reached the damage initiation threshold... When the cumulative equivalent plastic strain exceeds zero, the damage increment is zero; when the cumulative equivalent plastic strain exceeds zero... At that time, the damage increment is calculated.

[0054] The damage update relationship is as follows:

[0055] in, The damage variable from the previous increment step. For the damage variable in the current increment step, This represents the upper limit of damage. This formula guarantees that the damage variable is monotonically irreversible, meaning that damage can only increase or remain unchanged, and cannot be recovered.

[0056] The cumulative damage field D(x) is composed of the damage variable D at each integration point in the finite element model. For any integration point xi, the damage variable D(xi) at that point is calculated. The SDV1 data at all integration points are interpolated after finite element post-processing to form the cumulative damage field D(x) at the structural scale.

[0057] S3. Map the cumulative damage field of the damage concentration area to a continuously changing wall thickness field. The wall thickness value of the wall thickness field is positively correlated with the cumulative damage value at the corresponding position of the wall thickness field. In this embodiment, the cumulative damage value distribution within the damage concentration area identified in step S2, i.e., the damage field, is extracted, and a mapping relationship from damage value to wall thickness value is established: spatial locations with larger damage values ​​are assigned larger local wall thickness values; locations with smaller damage values ​​are assigned smaller local wall thickness values. This mapping adopts a linear function form to maintain the positive correlation between wall thickness and damage value, which increases monotonically. After mapping, an initial continuous wall thickness field is obtained, realizing reinforcement according to the degree of cumulative damage. The damage concentration area is strengthened by increasing the wall thickness to improve the local load-bearing capacity, while the slightly damaged area maintains a thinner wall thickness to control the structural quality. This allows the material distribution to match the damage risk, maximizing the mitigation of local damage concentration without significantly increasing the overall quality.

[0058] Preferably, mapping the cumulative damage field of the damage concentration zone to a continuously varying wall thickness field includes: The cumulative damage field within the damage concentration area is normalized to obtain the normalized damage variable. The normalized damage variable is mapped using a preset mapping function to obtain the initial wall thickness field; By applying smoothing filters and geometric continuity constraints to the initial wall thickness field, a continuously varying wall thickness field is obtained.

[0059] In this embodiment, firstly, the cumulative damage values ​​of all integration points within the damage concentration region are extracted and compressed to the [0,1] interval through normalization to eliminate the influence of absolute damage values, obtaining a normalized damage variable reflecting the relative strength of the damage. Then, a linear mapping function is used to convert the normalized damage variable into local wall thickness values, so that the wall thickness is larger at locations with greater damage, thus obtaining an initial wall thickness field. Finally, Gaussian smoothing filtering is applied to the initial wall thickness field to remove local burrs introduced by the discretization of the finite element mesh, and geometric constraints with continuous wall thickness values ​​and continuous first derivatives are applied at the connection boundaries between the transition zone and the porous and solid segments of the TPMS, resulting in a final continuously varying wall thickness field. The final wall thickness field reflects both the core distribution characteristics driven by the cumulative damage field (larger wall thickness for higher damage) and has the advantage of smoothness and continuity, providing high-quality input for subsequent gradient structure modeling.

[0060] In practical applications, after obtaining the cumulative damage field of a uniform TPMS structure, the cumulative damage field D(x) is used as the driving force for gradient wall thickness design. Here, D(x) represents the cumulative damage variable value at spatial location x. The damage field in the transition zone is normalized to obtain the normalized damage variable. :

[0061] in, and These represent the maximum and minimum damage values ​​in the boundary transition zone, respectively. This is a normalized damage variable.

[0062] Preferably, the preset mapping function is as follows:

[0063] In the formula, Let x be the local wall thickness value at location x in the boundary transition zone. This is the minimum allowable wall thickness value. This is the maximum permissible wall thickness value; This is a normalized damage variable.

[0064] S4. Based on the continuously changing wall thickness field, the boundary transition zone is adjusted to obtain the gradient TPMS sweating cooling structure model.

[0065] In this embodiment, the continuously varying wall thickness field obtained in step S3 is applied to the boundary transition zone in the uniform structure established in step S1: the original geometry of the TPMS porous segment and the solid segment remains unchanged, and only the uniform wall thickness of the boundary transition zone is replaced with a gradient wall thickness that varies continuously with spatial position. After the replacement, the wall thickness of the boundary transition zone changes smoothly from the side closer to the TPMS porous segment to the side closer to the solid segment (or in the opposite direction), without any abrupt changes in wall thickness. Finally, a complete gradient TPMS sweating cooling structure model is obtained. By introducing a wall thickness gradient in the boundary region where stiffness changes abruptly, the local stiffness, stress transmission path, and plastic deformation distribution of the structure tend to be smoother, thereby suppressing the localized accumulation of damage in this region. Compared to the uniform TPMS structure, the gradient TPMS structure can significantly reduce the damage peak value in the boundary transition zone under the same service load, making the damage distribution more uniform, while maintaining the cooling performance of the TPMS porous segment and the connection strength of the solid segment, ultimately improving the overall durability and reliability of the sweating cooling structure in high-temperature complex environments.

[0066] Preferably, after adjusting the boundary transition zone based on a continuously varying wall thickness field to obtain a gradient TPMS sweating cooling structure model, the method further includes: Under the same service load, damage comparison analysis was performed on the gradient TPMS sweating cooling structure model and the uniform TPMS sweating cooling structure model to obtain the damage optimization effect. If the damage optimization effect meets the preset cooling mitigation index, the target gradient transition TPMS sweating cooling structure is obtained.

[0067] In this embodiment, the gradient TPMS structural model and the uniform TPMS structural model are placed in the same finite element analysis environment (including the same mesh density, boundary conditions, load application method, material parameters, damage analysis model, and solver settings) and solved separately. After solving, the maximum damage value, damage distribution cloud map, and equivalent plastic strain distribution of the transition zone between the two structures are extracted. If the maximum damage value of the gradient structure is lower than that of the uniform structure, and the damage distribution is more uniform, the optimization effect is considered to meet the preset index, and the gradient structure is identified as the target gradient transition TPMS sweating cooling structure; otherwise, the upper and lower limits of wall thickness or smoothing parameters in the mapping function are adjusted, and the mapping and adjustment steps are repeated until the index is met. This forms a closed-loop optimization process of "analysis-mapping-adjustment-verification," ensuring that the final output gradient structure does indeed achieve the damage mitigation purpose, improving the credibility of the design results and the engineering reliability.

[0068] Preferably, the damage optimization effect meets the preset cooling mitigation index, including: The maximum damage value in the transition zone of the gradient TPMS sweating cooling structure model is lower than that of the uniform TPMS sweating cooling structure model. The damage distribution in the transition zone of the gradient TPMS sweating cooling structure model is uniform, and there are no newly added damage concentration areas.

[0069] In this embodiment, by comparing and analyzing the results, it is determined whether the gradient structure simultaneously meets the following two conditions: First, the maximum damage variable value of the gradient structure in the transition zone is less than that of the uniform structure in the same region. This condition quantitatively reflects the reduction effect of the damage peak value. Second, from the damage cloud map, the area of ​​the high-damage region in the transition zone of the gradient structure is reduced and the distribution is more gradual. At the same time, no new high-damage points or obvious local concentration zones appear in the porous section of TPMS, the solid section, and other areas without gradient design. By using the dual indicators of peak reduction and homogenization, the effectiveness of the gradient design is comprehensively evaluated to ensure that the final structure has better overall durability, rather than simply transferring damage from one location to another.

[0070] Compared to existing technologies, this invention constructs a uniform TPMS structural model, obtains the cumulative damage field after applying load, and identifies damage concentration areas. It then maps the damage field to a continuous wall thickness field that is positively correlated with the damage value, adjusting the transition zone to obtain a gradient structure. This ensures that the wall thickness distribution directly corresponds to the actual damage evolution history, effectively reducing the damage peak value in the transition zone and avoiding misjudgments easily caused by traditional stress optimization. The invention employs a constitutive model coupling the J2 isotropic hardening plasticity sub-model and the Lemaitre ductile damage evolution sub-model, enabling finite element analysis to simultaneously output both the plastic and damage zones. This provides a precise driving force reflecting the loading history for gradient design, solving the problem of the inability to directly obtain the damage field. Furthermore, this invention, through the accumulation of damage in the damage concentration area... The cumulative damage field is normalized sequentially, and an initial wall thickness field is obtained through a preset mapping function. Then, a continuous wall thickness field is obtained through smoothing filtering and geometric continuity constraints. This retains the core driving logic of "higher damage means larger wall thickness" while eliminating numerical noise and geometric abrupt changes, making the gradient wall thickness field smooth and continuous. After obtaining the gradient structure, the present invention performs damage comparison analysis with a uniform structure under the same service load. "Reduction of maximum damage value in the transition zone" and "uniform damage distribution with no new concentrated areas" are used as dual judgment indicators. If the indicators are met, the target structure is output; otherwise, the parameters are adjusted and the mapping is repeated. This closed-loop process forms an optimization chain of "analysis-mapping-verification-feedback" to ensure that the final design truly achieves the purpose of damage mitigation and avoids the blindness of single design.

[0071] To demonstrate the effectiveness of the optimization method of this invention, a comparative experiment was also conducted in this embodiment. Specifically, the same service load was applied to a uniform Diamond TPMS sweating cooling structure with the same material parameters and without gradient transition, and to a Diamond TPMS sweating cooling structure optimized by the gradient wall thickness design of this invention, respectively, for comparative experiments. The experimental results are as follows: Figure 2 This paper presents stress, strain, damage, and equivalent plastic strain distribution contour maps of a uniform Diamond TPMS sweating cooling structure with no gradient transition under service loads. The results show that in the transition zone between the porous and solid sections of the TPMS, the damage contour map (…) Figure 2 (c) and equivalent plastic strain contour plot ( Figure 2 (d) All of them showed obvious high value concentration areas, indicating that the area became a damage concentration area due to abrupt change in geometric stiffness and plastic accumulation, which is a dangerous location for structural failure.

[0072] Figure 3 The diagram shows the analytical contour plot of the Diamond TPMS sweating cooling structure after the gradient wall thickness optimization design of this invention under the same service load. (Compared to...) Figure 2 compared to, Figure 3(c) shows a significant decrease in the concentration of damage cloud maps in the transition zone, and a reduction in the area of ​​high-damage regions. Figure 3 (d) The concentration of moderately effective plastic strain was also alleviated, indicating that the gradient wall thickness design effectively improved the local deformation and damage state of the transition zone.

[0073] Figure 4 A quantitative comparison was made between the maximum stress, maximum strain, maximum damage, and maximum equivalent plastic strain of a uniform TPMS structure without gradient and a gradient TPMS structure. Figure 4 It can be seen that the maximum damage value of the gradient structure ( Figure 4 (c) is significantly lower than that of the structure without gradient, and the maximum equivalent plastic strain ( Figure 4 (d) also decreased; at the same time, the maximum stress and maximum strain did not increase abnormally, indicating that the gradient design did not introduce new structural weak links while mitigating damage.

[0074] in conclusion: The gradient TPMS sweating cooling structure design method based on cumulative damage field driven proposed in this invention can make the wall thickness distribution correspond to the actual damage evolution history of the material, effectively reduce the damage peak value in the transition zone between the porous section and the solid section of TPMS, and make the damage distribution more gradual, thereby improving the durability and reliability of the sweating cooling structure in high-temperature complex service environment. It can be proved that the optimization design method of this invention can effectively alleviate the concentration of cumulative damage in the transition zone.

[0075] This invention also provides a gradient TPMS sweating cooling structure, which is designed based on the above-mentioned gradient TPMS-based sweating cooling structure optimization design method. The sweating cooling structure includes: The TPMS porous segment, solid segment, and the boundary transition zone between the TPMS porous segment and solid segment; wherein, the boundary transition zone is a transition zone with a continuously changing gradient, and the wall thickness value at any point in the boundary transition zone is positively correlated with the cumulative damage value generated at that point under a preset service load.

[0076] Compared to existing technologies, the gradient TPMS sweating cooling structure designed according to the above method, protected by this invention, exhibits a positive correlation between the wall thickness at any point in the transition zone and the cumulative damage value generated at that point under service loads. This structure, integrally formed through additive manufacturing, achieves a larger wall thickness in high-risk damage areas to improve local durability, and a smaller wall thickness in low-risk damage areas to control quality, thus realizing an optimal match between material distribution and failure evolution. Compared to a uniform TPMS structure, the damage peak value in the transition zone is significantly reduced, and the damage distribution is more uniform.

[0077] For specific limitations on the design of a gradient TPMS sweating cooling structure, please refer to the limitations on the optimization design method of a gradient TPMS-based sweating cooling structure mentioned above, which will not be repeated here.

[0078] In the embodiments provided in this application, it should be understood that the disclosed methods and systems can be implemented in other ways. The system embodiments described above are merely illustrative. For example, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple modules or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, and can be electrical, mechanical, or other forms.

[0079] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by program instructions and related hardware. The aforementioned program instructions can be stored in a computer-readable storage medium. When the program instructions are executed, they perform the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0080] It should be understood that the use of terms such as "system," "apparatus," "unit," and / or "module" in this application is only applicable to distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0081] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0082] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" or "several" means two or more, unless otherwise explicitly specified.

[0083] If a flowchart is used in this application, it is used to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for optimizing the design of a sweating cooling structure based on gradient TPMS, characterized in that, include: A uniform TPMS sweating and cooling structure model is constructed, which includes at least a porous TPMS segment, a solid segment, and a transition zone between the porous TPMS segment and the solid segment. A preset service load is applied to the uniform TPMS sweating cooling structure model, and the cumulative damage field is obtained by solving the pre-constructed damage analysis model. The damage concentration area in the boundary transition zone is then identified based on the cumulative damage field. The cumulative damage field of the damage concentration area is mapped to a continuously varying wall thickness field, and the wall thickness value of the wall thickness field is positively correlated with the cumulative damage value at the corresponding position of the wall thickness field. The boundary transition zone is adjusted based on the continuously changing wall thickness field to obtain a gradient TPMS sweating cooling structure model.

2. The sweating cooling structure optimization design method according to claim 1, characterized in that, The damage analysis model is an elastoplastic-damage coupled constitutive model; The elastoplastic-damage coupled constitutive model includes the J2 isotropic hardening plastic sub-model and the Lemaitre ductile damage evolution sub-model; The J2 isotropic hardening plastic sub-model is used to describe the plastic deformation process of the material in the sweating cooling structure; The Lemaitre ductile damage evolution sub-model is used to describe the cumulative damage evolution process of the material in the sweating cooling structure during plastic deformation.

3. The sweating cooling structure optimization design method according to claim 2, characterized in that, The preset service load includes strain increment and temperature increment; The J2 isotropic hardening plastic sub-model is used to obtain the effective equivalent stress, cumulative equivalent plastic strain, and equivalent plastic strain increment based on the strain increment and the temperature increment.

4. The sweating cooling structure optimization design method according to claim 3, characterized in that, The Lemaitre ductile damage evolution sub-model is used to obtain the cumulative damage field based on the effective equivalent stress, the cumulative equivalent plastic strain, and the equivalent plastic strain increment.

5. The method for optimizing the sweating and cooling structure according to claim 1, characterized in that, The step of mapping the cumulative damage field of the damage concentration area to a continuously varying wall thickness field includes: The cumulative damage field within the damage concentration area is normalized to obtain a normalized damage variable. The normalized damage variable is mapped using a preset mapping function to obtain the initial wall thickness field; The initial wall thickness field is smoothed and subjected to geometric continuity constraints to obtain the continuously varying wall thickness field.

6. The sweating cooling structure optimization design method according to claim 5, characterized in that, The preset mapping function is specifically as follows: In the formula, Let x be the local wall thickness value at position x in the boundary transition zone. This is the minimum allowable wall thickness value. This is the maximum permissible wall thickness value; The normalized damage variable is denoted as .

7. The method for optimizing the sweating and cooling structure according to claim 1, characterized in that, After adjusting the boundary transition zone based on the continuously varying wall thickness field to obtain the gradient TPMS sweating cooling structure model, the method further includes: Under the same service load, damage comparison analysis is performed on the gradient TPMS sweating cooling structure model and the uniform TPMS sweating cooling structure model to obtain the damage optimization effect. If the damage optimization effect meets the preset cooling mitigation index, the target gradient transition TPMS sweating cooling structure is obtained.

8. The sweating cooling structure optimization design method according to claim 7, characterized in that, The damage optimization effect meets the preset cooling mitigation index, including: The maximum damage value of the transition zone of the gradient TPMS sweating cooling structure model is lower than that of the uniform TPMS sweating cooling structure model. The damage distribution in the transition zone of the gradient TPMS sweating cooling structure model is uniform, and there are no newly added damage concentration areas.

9. The method for optimizing the design of a sweating cooling structure according to any one of claims 1-8, characterized in that, Before constructing the uniform TPMS sweating cooling structure model, the following is also included: The structure of the uniform TPMS sweating cooling structure model is determined; wherein the structure of the uniform TPMS sweating cooling structure model includes one or more of the Diamond, Gyroid, Schwarz P or I-WP structures.

10. A gradient TPMS sweating cooling structure, characterized in that, The structure is designed based on the method of any one of claims 1 to 9, and the sweating cooling structure includes: The TPMS porous segment, the solid segment, and the boundary transition zone between the TPMS porous segment and the solid segment; wherein the boundary transition zone is a transition zone with a continuously changing gradient, and the wall thickness value at any point in the boundary transition zone is positively correlated with the cumulative damage value generated at that point under a preset service load.

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