An efficient simulation method for honeycomb structures subjected to mixed compression and shear loading considering loading angle

Abstract

The present application belongs to the field of mechanical structure modeling and simulation analysis, and in particular relates to an efficient simulation method for the mixed compression and shear loading of honeycomb structures taking into account the loading angle. The efficient simulation method for the mixed compression and shear loading of honeycomb structures adopts a solid equivalent modeling method for honeycomb structures, ignores local details such as bending and folding of honeycomb cells, and determines simulation parameters that meet the conditions through simple sample tests, thereby obtaining an overall deformation mode and stress-strain history that are consistent with the actual test. The modeling is simple and the calculation efficiency is greatly improved. In the solid equivalent model of the efficient simulation method for the mixed compression and shear loading of honeycomb structures, the influence of the change of compression strength with the loading angle and the influence of shear action are taken into account, and the isotropic shear damage factor is defined. Therefore, it can be applied to complex working conditions such as head-on collision, oblique collision at different angles, overall plane collision, and local collision.

Description

Technical Field

[0001] The present application relates to the technical field of mechanical structure modeling and simulation analysis, and in particular to an efficient simulation method for honeycomb structure compression-shear mixed loading considering loading angle. Background Art

[0002] In collision devices such as ship collisions and car collisions, honeycomb structures have wide application potential due to their high specific energy absorption and specific strength. Compared with traditional materials, honeycomb structures can provide higher energy absorption capacity at a relatively light weight, thus playing an important role in collision events. Honeycomb structures are periodic array porous structures, and their cell scale is usually at the millimeter level. When simulating large-scale structures ranging from several meters to tens of meters, the use of fine modeling methods for honeycomb structures leads to a surge in the number of finite element model grids, extremely low computational efficiency, and a large amount of computing resources and time. In addition, in actual collision events, honeycomb structures may be impacted from different angles and affected by the irregular configuration of the impacting object, causing the honeycomb structure to be subjected to multiple forces such as compression and shear at the same time.

[0003] Liu Ming, Fei Jing, Fan Tiqiang and others from the China Automotive Engineering Research Institute Co., Ltd. filed a patent titled "An Equivalent Method for a Side Impact Barrier Honeycomb Model." The patent includes the following: Matching the equivalent cell side length after cell expansion based on the honeycomb model size and initial cell side length; Obtaining the equivalent cell theoretical wall thickness from the initial cell wall thickness based on cell expansion theory; Simulating the equivalent cell, performing equivalent analysis based on the mechanical properties of the honeycomb model before cell expansion to obtain the equivalent cell scaled wall thickness; Obtaining a scaling factor based on the initial cell wall thickness and the equivalent cell scaled wall thickness; Setting several coefficients and substituting them into the scaled wall thickness; and, through a barrier impact wall test, comparing the degree of similarity between the collision test data before and after cell expansion under different coefficients to obtain a correction factor; Obtaining the equivalent cell corrected wall thickness from the initial cell wall thickness based on the scaling factor and the correction factor. However, the following issues exist:

[0004] (1) When the equivalent cell expansion multiple is large, there is a significant difference in the deformation behavior of the honeycomb structure before and after cell expansion;

[0005] (2) This simulation method does not consider the effect of loading angle on cell expansion, and cannot consider the effects of compression shear mixing;

[0006] (3) In the simulation, each time the side length / wall thickness of the honeycomb is changed, the cell expansion theory needs to be recalibrated, which makes simulation modeling difficult.

[0007] Therefore, the study of equivalent simulation methods for honeycomb structures under large-scale collision conditions has become a key topic in current engineering. By developing an efficient and accurate simulation method, it is possible to effectively evaluate the performance of honeycomb structures in collision events, providing more reliable technical support for the design and optimization of collision devices. Summary of the Invention

[0008] The embodiments of the present application provide an efficient simulation method for the mixed compression and shear loading of honeycomb structures taking into account the loading angle, aiming to simplify the modeling difficulty, improve the calculation efficiency, and reduce the calculation cost.

[0009] To achieve the above objectives, the present application provides an efficient simulation method for the mixed compression and shear loading of a honeycomb structure taking into account the loading angle, comprising the following steps:

[0010] S1. Solid equivalent modeling: Use LS-DYNA simulation software to convert the entire honeycomb structure into a solid block;

[0011] S2. Define the plastic compression behavior of the honeycomb structure: Perform compression tests on three honeycomb specimens in the X, Y, and Z axes, obtain the stress-strain curves in the corresponding directions, and input them into the simulation software in the form of tables of (strain value, stress value) coordinate pairs. The three tables are defined as table X pressure, table Y pressure, and table Z pressure, respectively. During the simulation calculation, the corresponding table is called according to the actual compression direction and compression force value.

[0012] S3. Conduct tests on honeycomb specimens at various loading angles and compressive strength along the primary loading direction of the honeycomb structure. Obtain a compressive strength-angle relationship curve. This curve is input into the simulation software as a table of (angle value, compressive strength value) coordinate pairs. During simulation calculations, this table is used based on the actual loading angle and compressive strength values.

[0013] S4. Define the plastic shear behavior of the honeycomb structure: Perform shear tests on three honeycomb specimens in the XY, YZ, and XZ planes, respectively, and obtain the shear stress-strain curves for the corresponding planes. Convert the softening segments in the shear stress-strain curves for each plane into damage coefficients and input them into the simulation software in the form of tables of (strain value, damage coefficient value) coordinate pairs. Define the three tables as Table XY Shear, Table YZ Shear, and Table XZ Shear, respectively. During simulation calculations, call the corresponding tables based on the actual shear plane and shear force values.

[0014] S5. Input the isotropic shear strength and hydrostatic strength of the honeycomb structure into the simulation software to ensure that the equivalent solid block remains stable when subjected to stress in different directions.

[0015] Optionally, in step S2, compression tests are performed on the three honeycomb samples in the X, Y, and Z axes respectively, and the force-displacement curves of the compression in the corresponding directions are measured, which are converted into stress-strain curves in the corresponding directions through force / area and displacement / total length.

[0016] Optionally, in step S3, the main load direction is the force direction of the honeycomb structure when it is actually used for collision.

[0017] Optionally, the main load direction is the axial direction of the cells in the honeycomb structure.

[0018] Optionally, in step S4, the shear stress-strain curve of the honeycomb structure is shaped like a parabola, the shear stress increases monotonically with the strain, and drops rapidly after reaching the maximum value. The entire drop process is called the softening section. The softening section is represented in the simulation in the form of a damage coefficient curve. The horizontal coordinate of the damage coefficient curve is the shear strain value, and the vertical coordinate of the damage coefficient curve is a value between 0 and 1. In the simulation software, the (strain value, damage coefficient value) coordinate group is input to represent the shear damage.

[0019] Optionally, the efficient simulation method for the honeycomb structure subjected to mixed compression and shear loading is applicable to aluminum honeycomb structures and steel honeycomb structures.

[0020] Optionally, the efficient simulation method for honeycomb structure subjected to mixed compression and shear loading is applicable to anisotropic nonlinear materials.

[0021] The beneficial effect of the efficient simulation method for mixed compression and shear loading of honeycomb structures considering the loading angle provided by the present application is that: compared with the existing technology, the efficient simulation method for mixed compression and shear loading of honeycomb structures of the present application adopts a solid equivalent modeling method for honeycomb structures, and there is no need to model the pores of the honeycomb. The LS-DYNA simulation software is used to equate the entire structure to a solid block, and local details such as bending and folding of the honeycomb cells are ignored. The simulation parameters that meet the conditions are determined through simple sample tests, and the overall deformation mode and stress-strain history consistent with the actual test are obtained. The modeling is simple and the calculation efficiency is greatly improved.

[0022] This efficient simulation method for mixed compression and shear loading in honeycomb structures incorporates a solid equivalent model that accounts for the effect of compression strength as a function of loading angle, making it applicable to collisions with large plastic deformation at various impact angles. By accounting for the effects of shear and defining isotropic shear damage factors, it can simulate complex loading patterns during impact. Consequently, it is applicable to complex collisions, including head-on collisions, oblique collisions at various angles, full-plane collisions, and localized collisions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] in:

[0025] Figure 1 It is a three-dimensional schematic diagram of a honeycomb structure;

[0026] Figure 2 is the shear stress-strain curve of the honeycomb structure;

[0027] Figure 3 This is a compression test diagram of a honeycomb sample on the Z axis in an efficient simulation method for a honeycomb structure subjected to compression and shear mixed loading, as shown in one embodiment of the present application;

[0028] Figure 4 This is a diagram of an oblique compression test of a honeycomb sample in the main loading direction in an efficient simulation method for a honeycomb structure subjected to compression and shear mixed loading, as shown in one embodiment of the present application;

[0029] Figure 5 This is a shear test diagram of a honeycomb sample in the XY plane in an efficient simulation method for a honeycomb structure subjected to compression and shear mixed loading, as shown in one embodiment of the present application;

[0030] Figure 6 This is a test diagram of a honeycomb sample being compressed by a curved indenter on the Z axis in an efficient simulation method for a honeycomb structure subjected to compression-shear mixed loading, as shown in one embodiment of the present application;

[0031] Figure 7 2. It is a schematic diagram of the comparison between the cambered surface compression test and the high-efficiency simulation method of the honeycomb structure compression-shear mixed loading in the present application;

[0032] Figure 8 This is an equivalent method verification and calculation efficiency diagram of an efficient simulation method for a honeycomb structure subjected to compression and shear mixed loading, as shown in one embodiment of the present application, wherein: Figure 8 (a) Stress-strain curves of honeycomb structure under plane hammer compression under test, solid equivalent modeling and shell element fine modeling, and calculation time histograms under solid equivalent modeling and shell element fine modeling; Figure 8 (b) The stress-strain curves of the honeycomb structure under the compression of the cambered hammer head under the test, solid equivalent modeling and shell element fine modeling, and the calculation time histogram under solid equivalent modeling and shell element fine modeling;

[0033] Figure 9 This is the overall technical roadmap of an efficient simulation method for a honeycomb structure subjected to mixed compression and shear loading, as shown in one embodiment of the present application;

[0034] Figure 10 This is a comparison diagram of impact force-displacement curves of a series honeycomb under a curved pressure head in a comparative test and simulation, shown in an embodiment of the present application;

[0035] Figure 11 This is a comparison diagram of deformation modes of a series honeycomb under a curved pressure head in a comparative test and simulation, shown in an embodiment of the present application;

[0036] Figure 12 : is a diagram of the structural deformation pattern in the composite structure drop hammer test and simulation shown in one embodiment of the present application, wherein: Figure 12 (a) is a diagram of the test device; Figure 12 (b) is the structural deformation pattern diagram in the simulation; Figure 12 (c) is the structural deformation pattern diagram during the test;

[0037] Figure 13 1 is a schematic diagram of an impact force-time curve and a hammer displacement-time curve obtained from experiments and simulations according to an embodiment of the present application.

[0038] Description of main component symbols:

[0039] 1. Honeycomb sample; 2. Flat hammer head; 3. Support steel plate; 4. Left steel plate; 5. Right steel plate; 6. Curved hammer head. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many other forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0041] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0042] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0044] The embodiment of the present application provides an efficient simulation method for honeycomb structure compression-shear mixed loading considering the loading angle, comprising the following steps:

[0045] S1. Solid equivalent modeling: Use LS-DYNA simulation software to convert the entire honeycomb structure into a solid block;

[0046] S2. Define the plastic compression behavior of the honeycomb structure: perform compression tests on the three honeycomb samples in the X, Y, and Z axes, obtain the stress-strain curves in the corresponding directions, and input them into the simulation software in the form of a table of (strain value, stress value) coordinate groups. The three tables are defined as Table X压 ,surface Y压 ,surface Z压 ,During simulation calculation, the corresponding table is called according to the actual compression direction and compression force value;

[0047] S3. Conduct tests on honeycomb specimens at various loading angles and compressive strength along the primary loading direction of the honeycomb structure. Obtain a compressive strength-angle relationship curve. This curve is input into the simulation software as a table of (angle value, compressive strength value) coordinate pairs. During simulation calculations, this table is used based on the actual loading angle and compressive strength values.

[0048] S4. Define the plastic shear behavior of the honeycomb structure: perform shear tests on the three honeycomb samples in the XY, YZ, and XZ planes, obtain the shear stress-strain curves of the corresponding planes, convert the softening section in the shear stress-strain curve of each plane into a damage coefficient, and input it into the simulation software in the form of a table of (strain value, damage coefficient value) coordinate groups. The three tables are defined as Table XY剪 ,surface YZ剪 ,surface XZ剪 ,During simulation calculation, the corresponding table is called according to the actual shear plane and shear force value;

[0049] S5. Input the isotropic shear strength and hydrostatic strength of the honeycomb structure into the simulation software to ensure that the equivalent solid block remains stable when subjected to stress in different directions.

[0050] Among them, in step S2, the three honeycomb samples are subjected to compression tests in the three axes of X, Y, and Z, respectively, and the force-displacement curves of the compression in the corresponding directions are measured, which are converted into stress-strain curves in the corresponding directions through force / area and displacement / total length.

[0051] In the embodiment of the present application, the efficient simulation method for the mixed compression and shear loading of the honeycomb structure adopts a solid equivalent modeling method for the honeycomb structure. There is no need to model the pores of the honeycomb. The LS-DYNA simulation software is used to equate the entire structure to a solid block, and local details such as bending and folding of the honeycomb cells are ignored. Through simple sample tests, the simulation parameters that meet the conditions are determined, and the overall deformation mode and stress-strain history consistent with the actual test are obtained. The modeling is simple and the calculation efficiency is greatly improved.

[0052] This efficient simulation method for mixed compression and shear loading in honeycomb structures takes into account the influence of compression strength as a function of loading angle in its physical equivalent model, making it applicable to collisions with large plastic deformation at various impact angles. By considering the effects of shear and defining isotropic shear damage factors, it can simulate the complex loading patterns during an impact. Therefore, it is applicable to complex conditions such as head-on collisions, oblique collisions at various angles, overall planar collisions, and localized collisions, taking into account the effects of loading angle and mixed compression and shear loading, resulting in improved applicability.

[0053] The entity equivalent modeling method of the present application is not only applicable to aluminum honeycombs, but also to honeycomb structures of other alloy materials (such as steel honeycombs); it is also applicable to other anisotropic nonlinear materials, such as foamed aluminum, polyurethane foam materials, etc.

[0054] Comparison with existing cellular equivalent patents:

[0055] First, it should be clarified that the most basic and mature honeycomb simulation method currently uses shell element modeling. This involves replicating the actual honeycomb geometry at a 1:1 scale within finite element software. This method offers good computational accuracy, but is computationally inefficient for large-scale models. A comparison of some currently published / authorized patents with this invention is as follows:

[0056] 1) A method and system for determining failure mechanical parameters of honeycomb aluminum materials

[0057] Difference: This patent focuses on the failure parameters of the honeycomb parent material (aluminum alloy) and the failure simulation method of aluminum honeycomb. The finite element model used is a 1:1 honeycomb geometry with shell elements and does not involve the concept of "equivalence." In other words, the focus of this patent is on how to accurately simulate, while the focus of this application's efficient simulation method for honeycomb structures subjected to mixed compression and shear loading is on how to achieve equivalence for the honeycomb structure.

[0058] 2) An equivalent method for the honeycomb model of a side impact barrier

[0059] Differences: This patent performs cell expansion equivalence on honeycombs (for example, a honeycomb with a side length of 10mm is equivalent to a honeycomb with a side length of 100mm, while adjusting other parameters to approximate the mechanical properties before and after equivalence). In finite element modeling, shell elements are still used, while the present application's efficient simulation method for mixed compression and shear loading of honeycomb structures uses solid elements, which is fundamentally different in principle. In addition, different loading conditions affect cell expansion equivalence (for example, the cell expansion formulas for uniaxial loading and oblique loading differ). Therefore, it is difficult to expand cells using a single formula for complex loads, while the present application can simulate complex loads.

[0060] 3) A cellular equivalent unit and a parameter calculation method based on the cellular equivalent unit

[0061] This patent proposes an equivalent calculation method for honeycomb sandwich panels. The upper panel, lower panel and honeycomb are taken as a whole to obtain key parameters such as torsional stiffness and bending stiffness, and at the same time, a very small "Y" unit in the honeycomb is taken to be equivalent using the energy method. This solution lacks a clear and systematic method for obtaining simulation parameters; the honeycomb can be regarded as an array of many "Y" units, but under complex loads, the deformation modes of the "Y" units at different positions are coupled with each other, and it is difficult to use the energy method to obtain a universal force-displacement relationship. This patent is suitable for working conditions with simple forces (such as uniaxial compression and overall bending), and it is difficult to simulate local loads and mixed compression and shear loads.

[0062] Differences: The object equivalent to the efficient simulation method for mixed compression and shear loading of honeycomb structures in this application is the honeycomb structure, while the object equivalent to this patent is the panel + honeycomb in the sandwich structure; the specific equivalent implementation methods are different, especially the plastic behavior methods are different, this patent uses the energy method to obtain the force-displacement relationship to describe the plastic behavior, and this application obtains the stress-strain relationship based on triaxial compression test and triaxial shear test; the scope of equivalence is different, this application takes into account the load angle, shear effect, and shear damage accumulation, while this patent does not. The energy method proposed in this patent is only applicable to simple stress conditions, while the efficient simulation method for mixed compression and shear loading of honeycomb structures in this application is applicable to more complex stress conditions; the force-displacement acquisition method of this patent requires iteration, in other words, it requires a lot of trial and error and debugging, which is actually a fitting, while the parameters of this application are all obtained through experiments, reflecting the mechanical nature of the structure.

[0063] In short, compared with some existing patents, the significant uniqueness of the efficient simulation method of honeycomb structure compression and shear mixed loading in this application lies in: different equivalent principles and different scope of application.

[0064] This application simulates the plastic behavior of metal honeycomb structures under oblique loading and mixed compression and shear loads, characterizing their overall mechanical properties through solid equivalent simulation while ignoring local details such as bending and folding of honeycomb cells. The key to this application is how to determine simulation parameters that meet the conditions based on simple sample tests, obtain an overall deformation pattern and stress-strain history that are consistent with real experiments, and significantly improve computational efficiency. The specific implementation methods are as follows:

[0065] It should be noted that the equivalent parameter definition methods in this application are all obtained through experimental tests, including compression tests, shear tests and hydrostatic strength tests. Such tests have professional testing equipment and are mature testing methods.

[0066] 1) Define the plastic compression behavior of honeycomb structures

[0067] The honeycomb structure is a two-dimensional periodic regular hexagonal structure, such as Figure 1 As shown in Figure 2, the key parameters affecting honeycomb strength are the length of the regular hexagon, wall thickness, and material. When instability is not considered and the number of honeycomb cells is greater than 7×7, the effect of overall size on the strength of the honeycomb structure can be ignored.

[0068] It should be noted that the embodiment of the present application proposes an equivalent simulation method for the universality of honeycomb structures and honeycomb-like structures, not for a specific honeycomb. The method proposed in this application can be used to perform equivalence on honeycombs of any size, dimension, or material. Therefore, when designing an experiment, it is sufficient to determine the parameters based on the actual honeycomb structure you want to simulate. For ease of understanding, a case is provided where the honeycomb structure parameters are: side length 4mm, wall thickness 0.08mm, and material aluminum alloy AL5052.

[0069] First, the honeycomb structure needs to be subjected to axial compression tests in three directions. The test can measure the force-displacement curve of the corresponding compression direction, which can be converted into a stress-strain curve through force / area and displacement / total length. The stress-strain curves in the corresponding directions are input into the simulation model in the form of a table of (strain value, stress value) coordinate groups. During the simulation calculation, the three-dimensional compressive plastic behavior of the honeycomb can be defined by calling the table and updating the stress according to the strain state of the structure.

[0070] Based on the above, further tests were conducted on the relationship between different loading angles and compressive strength in the main loading direction. A strength-angle relationship curve was obtained, and the (angle value, compressive strength value) coordinate table was input into the simulation model.

[0071] The test method of flat pressure mechanical performance is as follows Figure 3 As shown in the figure, the performance test methods for different loading angles are as follows Figure 4 shown.

[0072] 2) Define the plastic shear behavior of honeycomb

[0073] The honeycomb structure was subjected to shear tests in three planes (e.g. Figure 5 As shown in the figure, the shear stress-strain curve of the corresponding plane is obtained. The shear stress-strain curve of the honeycomb structure is a parabola. The stress increases monotonically with the strain and drops rapidly after reaching the maximum value. The falling section of the curve represents shear damage in the honeycomb structure, indicating that part of the honeycomb structure has been torn and sheared. The entire falling process is called the "softening section". Figure 2 shown.

[0074] The softening stage is represented in the simulation using a damage coefficient curve. The horizontal axis of the damage coefficient curve represents strain, with the first point corresponding to the strain at the maximum value in the figure below. The vertical axis of the damage coefficient curve is a number between 0 and 1, with 1 corresponding to the maximum stress in the figure below and a damage coefficient of 0 corresponding to a stress of 0. This effectively maps the softening stage between 0 and -1. In the simulation, the coordinate pair (strain value, damage coefficient value) is input to represent shear damage.

[0075] 3) Anti-distortion of units under mixed compression and shear loads

[0076] To prevent distortion of the equivalent unit under low stress, the isotropic shear strength and hydrostatic strength of the honeycomb structure are further input. Shear strength is determined through the shear test described in 2) above, while hydrostatic strength is determined through hydrostatic strength testing. Both shear and hydrostatic tests are conventional testing methods. They ensure that the equivalent unit remains stable when subjected to stress in different directions.

[0077] Figure 7 A comparative analysis of the effect of unit anti-distortion treatment is given. It can be found that the traditional shell unit fine modeling is consistent with the experimental deformation mode. When the unit distortion is not treated, the structural deformation mode is distorted, and local unit over-stretching and macroscopic non-realistic lateral deformation occur. After the unit distortion is treated, the simulation results of the solid equivalent model are consistent with the experimental and traditional shell unit fine model results.

[0078] 4) Verification of equivalent methods

[0079] To verify the calculation accuracy, the plane compression test ( Figure 3 ) and compression-shear mixed compression test ( Figure 6 ) for comparison. Figure 8 To verify the results, it is shown that the efficient simulation method of the honeycomb structure under compression and shear mixed loading of the present application has high accuracy while greatly reducing the calculation efficiency.

[0080] The specific application process is as follows:

[0081] 1. Such as Figure 9As shown, the overall technical route of the efficient simulation method for the honeycomb structure compression and shear mixed loading is shown.

[0082] 2. Specific process

[0083] 1) Constitutive type

[0084] In LS-DYNA, there are two types of solid honeycomb constitutive models available: MAT26 and MAT126.

[0085] ①MAT26: The main use of this material model is for cellular and foam materials with realistic anisotropic behavior. Nonlinear elastic-plastic material behavior can be defined separately for all normal and shear stresses. These are considered to be fully decoupled.

[0086] ②MAT126: This material model is commonly used for aluminum crushable foam materials with anisotropic behavior. Three yield surfaces are available. The first yield surface defines the nonlinear elastic-plastic material behavior for all normal stresses and shear stresses, respectively, which are assumed to be completely decoupled. The second yield surface accounts for the effects of eccentric loads and is isotropic. However, due to this definition of the second yield surface, the material may collapse in shear mode due to low shear resistance. There is no obvious way to increase the shear resistance without changing the pure uniaxial compression behavior. Therefore, for the third yield surface, the model is modified to specify the shear resistance and hydrostatic resistance of the material without affecting the uniaxial performance. The third yield surface is labeled ECCU, which is the initial stress yield limit in simple shear.

[0087] When LCA is set to negative, the second yield surface is activated, and when ECCU is simultaneously set to negative, the third yield surface is activated.

[0088] 2) Unit type

[0089] Previous studies have shown that for solid honeycomb elements, it is recommended to use a fully integrated element type for calculations to avoid excessive hourglass energy. In addition, the LS-DYNA user manual recommends element type 0 (nonlinear spring element) for MAT126.

[0090] 3) Working condition verification analysis

[0091] Considering the mechanical behavior of honeycombs under mixed compression and shear, two types of working conditions are designed: plane compression (uniaxial compression behavior) and arc surface compression (mixed compression and shear behavior). Based on the available constitutive types and element types, the available combinations of honeycomb models are as follows:

[0092] ①MAT26 constitutive + full integration unit

[0093] ②MAT126 constitutive model (do not activate the second and third yield surfaces) + full integration unit

[0094] ③MAT126 constitutive model (activate the second and third yield surfaces) + full integration unit

[0095] ④MAT126 constitutive model (do not activate the second and third yield surfaces) + nonlinear spring element

[0096] ⑤MAT126 constitutive (activate the second and third yield surfaces) + nonlinear spring element

[0097] 4) Constitutive + element type selection

[0098] According to the working condition analysis results in 3), we can get:

[0099] MAT26 + Full Integration - MAT126 does not activate the second and third yield surfaces + Full Integration Unit: It can better reflect the deformation mode during flat compression. The impact force rises slightly before densification (unreasonable). Under the action of the curved surface, unreasonable lateral distortion occurs.

[0100] MAT126 activates the second and third yield surfaces + full integration unit - both flat compression and arc compression can better reflect the deformation mode and impact force curve

[0101] MAT126 does not activate the second and third yield surfaces + nonlinear spring unit - it can better reflect the deformation mode during flat compression. The impact force rises slightly before densification (unreasonable). Under the action of the curved surface, unreasonable lateral distortion occurs.

[0102] MAT126 activates the second and third yield surfaces + nonlinear spring unit - it can better reflect the deformation mode and impact force curve when flat, but under the action of the curved surface, unreasonable lateral distortion occurs

[0103] Therefore, MAT126 activates the second and third yield surfaces + full integration unit, which is more applicable.

[0104] 5) Constitutive parameters

[0105] MAT126 constitutive model, parameter setting method when activating the second and third yield surfaces (LCA<0, ECCU<0) Since there are many variables that need to be set in MAT126, they are explained in separate lines.

[0106] MAT126 parameter Card1

[0107] Card1 1 2 3 4 5 6 7 8 variable MID RO E PR SIGY VF MU BULK default value None None None None None None 0.05 0

[0108] ①Card1 setting method

[0109] The specific method of setting the parameters of this line is as follows:

[0110] MID: Material ID.

[0111] RO: mass density.

[0112] E: Young's modulus of the honeycomb material.

[0113] PR: Poisson's ratio of the cellular material.

[0114] SIGY: Yield stress of fully compacted honeycomb.

[0115] VF: relative volume when the cell is fully compacted.

[0116] MU: Material viscosity coefficient. The default value of 0.05 is recommended.

[0117] BULK: Bulk viscosity. It is recommended to set it to 0, that is, not use bulk viscosity.

[0118] ②Card2 setting method

[0119] MAT126 parameter Card2

[0120] Card2 1 2 3 4 5 6 7 8 variable LCA LCB LCC LCS LCAB LCBC LCCA LCSR default value None LCA LCA LCA LCS LCS LCS Optional

[0121] The specific method of setting the parameters of this line is as follows:

[0122] LCA: Set to negative to activate the second yield surface. In this case, LCA is a function of the yield stress and the loading angle.

[0123] LCB: is the function between strong axis hardening stress and volume strain.

[0124] LCC: is the function between weak axis hardening stress and volume strain.

[0125] LCS: Gives the shear stress coefficient as a damage curve for the shear strain component. To set up a three-dimensional orthotropic model, define LCAB, LCBC, and LCCA separately.

[0126] LCAB: Function between the shear stress coefficient and the shear strain component in the AB direction.

[0127] LCBC: Function between the shear stress coefficient and the shear strain component in the BC direction.

[0128] LCCA: Function between the shear stress coefficient and the shear strain component in the CA direction.

[0129] LCSR: strain rate curve.

[0130] ③Card3 setting method

[0131] MAT126 parameter Card3

[0132] Card3 1 2 3 4 5 6 7 8 variable EAAU EBBU ECCU GABU GBCU GCAU AOPT MACF

[0133] The specific method of setting the parameters of this line is as follows:

[0134] EAAU: Elastic modulus of the strong axis of the honeycomb when it is not compressed.

[0135] EBBU: weak axis elastic modulus of the honeycomb when it is not compressed.

[0136] ECCU: Set to negative to activate the third yield surface. In this case, the absolute value of ECCU is the simple shear strength.

[0137] GABU: strong-weak axis shear modulus.

[0138] GBCU: weak-weak axis shear modulus.

[0139] GCAU: hydrostatic ultimate strength of honeycomb.

[0140] AOPT: Set to 2 to give the cell orthotropic anisotropy, with the direction given by the parameters in Card4 and Card5.

[0141] MACF: Material axial modification parameter, not used.

[0142] ④Card4 setting method

[0143] MAT126 parameter Card4

[0144] Card4 1 2 3 4 5 6 variable XP YP ZP A1 A2 A3

[0145] ⑤Card5 setting method

[0146] MAT126 parameter Card5

[0147] Card5 1 2 3 4 5 6 7 8 variable D1 D2 D3 TSEF SSEF VREF TREF SHDFLG

[0148] 6) Test verification

[0149] ① Comparison of series honeycomb arc pressure head test

[0150] Impact force curve Figure 10-11 As shown in Figure 1, the deformation process in the test and simulation is compared using G1 as an example. In the simulation, solid elements are used to simulate the honeycomb, and strain contours are drawn to more intuitively reflect the deformation area. Comparing the experimental and simulation curves, both the rising and plateau sections show a high degree of agreement, demonstrating that the simulation constitutive model and simulation method have good simulation accuracy.

[0151] ②Comparison of composite structure drop hammer test

[0152] Figure 12The structural deformation patterns in the test and simulation are given, and typical deformation locations are extracted for comparison.

[0153] Figure 13 The impact force-time curve and hammer displacement-time curve obtained from the experiment and simulation were compared. At the beginning of the impact, an initial peak appeared in the curve. Since the hammer has an arc-shaped configuration, the contact area with the sample continues to increase during the impact, so the impact force increases accordingly and gradually reaches the maximum peak. Finally, due to the decrease in the speed of the sample, the hammer rebounds and unloads quickly. The comparison results show that the experimental and simulation trends are highly consistent, whether it is the impact force or the hammer displacement curve. Among them, the error of the maximum peak impact force is 6.4%, the error of the impact response time (as of the start of unloading) is 7%, and the error of the maximum displacement of the hammer is 3%. Overall, the errors of key indicators such as impact force and hammer displacement in simulation and experiment are less than 8%, indicating that the simulation method has high accuracy.

[0154] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0155] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. An efficient simulation method for the mixed compression and shear loading of honeycomb structures considering the loading angle, characterized by: The following steps are involved: S1. Solid equivalent modeling: Use LS-DYNA simulation software to convert the entire honeycomb structure into a solid block; S2. Define the plastic compression behavior of the honeycomb structure: perform compression tests on the three honeycomb samples in the X, Y, and Z axes, obtain the stress-strain curves in the corresponding directions, and input them into the simulation software in the form of a table of (strain value, stress value) coordinate groups. The three tables are defined as Table X压 ,surface Y压 ,surface Z压 ,During simulation calculation, the corresponding table is called according to the actual compression direction and compression force value; S3. Conduct tests on honeycomb specimens at various loading angles and compressive strength along the primary loading direction of the honeycomb structure. Obtain a compressive strength-angle relationship curve. This curve is input into the simulation software as a table of (angle value, compressive strength value) coordinate pairs. During simulation calculations, this table is used based on the actual loading angle and compressive strength values. S4. Define the plastic shear behavior of the honeycomb structure: perform shear tests on the three honeycomb samples in the XY, YZ, and XZ planes, obtain the shear stress-strain curves of the corresponding planes, convert the softening section in the shear stress-strain curve of each plane into a damage coefficient, and input it into the simulation software in the form of a table of (strain value, damage coefficient value) coordinate groups. The three tables are defined as Table XY剪 ,surface YZ剪 ,surface XZ剪 ,During simulation calculation, the corresponding table is called according to the actual shear plane and shear force value; S5. Input the isotropic shear strength and hydrostatic strength of the honeycomb structure into the simulation software to ensure that the equivalent solid block remains stable when subjected to stress in different directions.

2. The high-efficiency simulation method for the compression-shear mixed loading of honeycomb structures according to claim 1 is characterized in that: In step S2, compression tests are performed on the three honeycomb samples in the X, Y, and Z axes respectively, and the force-displacement curves of the compression in the corresponding directions are measured. The force / area and displacement / total length are converted into stress-strain curves in the corresponding directions.

3. The high-efficiency simulation method for the compression-shear mixed loading of honeycomb structures according to claim 1 is characterized in that: In step S3, the main load direction is the force direction of the honeycomb structure when it is actually used for collision.

4. The high-efficiency simulation method for the compression-shear mixed loading of honeycomb structures according to claim 3 is characterized in that: The main load bearing direction is the axial direction of the cells in the honeycomb structure.

5. The high-efficiency simulation method for the compression-shear mixed loading of honeycomb structures according to claim 1 is characterized in that: In step S4, the shear stress-strain curve of the honeycomb structure is similar to a parabola. The shear stress increases monotonically with the strain and drops rapidly after reaching the maximum value. The entire drop process is called the softening section. The softening section is represented in the simulation in the form of a damage coefficient curve. The horizontal coordinate of the damage coefficient curve is the shear strain value, and the vertical coordinate of the damage coefficient curve is a value between 0 and 1. In the simulation software, the (strain value, damage coefficient value) coordinate group is input to represent the shear damage.

6. The high-efficiency simulation method for the compression-shear mixed loading of honeycomb structures according to claim 1 is characterized in that: The efficient simulation method for the compression-shear mixed loading of honeycomb structures is applicable to aluminum honeycomb structures and steel honeycomb structures.

7. The high-efficiency simulation method for the compression-shear mixed loading of honeycomb structures according to claim 1 is characterized in that: The efficient simulation method for honeycomb structure subjected to compression-shear mixed loading is applicable to anisotropic nonlinear materials.

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