A high-efficiency energy absorption gradient surface structure

Abstract

The present invention discloses a high-efficiency energy absorption gradient curved surface structure. The curved surface structure adopts a sheet-based TPMS structure and has an internal relative density gradient variation structure. The sheet-based TPMS structure is constructed using the inequality ‑C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can result in TPMS structures with different volume fractions, and by changing the parameter C, the relative density of the TPMS structure can be controlled. The formula is as follows: where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in three directions can be controlled. The present invention changes the deformation form of the structure through the design of the relative density gradient variation, thereby optimizing the energy absorption capacity of the entire structure and improving its ability to withstand impact loads.

Description

Technical Field

[0001] The invention relates to an impact-resistant material, in particular to a high-efficiency energy absorption gradient curved surface structure. Background Art

[0002] Many devices and structures are often subjected to shock environments during their service life, such as car collisions. Without appropriate shock-resistant technology, structures and various components may be damaged or malfunction under shock conditions, causing the system to fail to operate normally, resulting in serious accidents and casualties. Research on shock-resistant technology aims to take measures to mitigate or disperse shock, protect equipment, and improve the reliability of equipment under extreme working conditions to ensure that it can continue to operate normally in harsh environments. Engineers often use load-reducing materials to reduce the shock peak transmitted to the device. Some commonly used load-reducing materials include disc springs, foam silicone rubber, foam aluminum, etc. These materials can absorb part of the energy when the projectile has a large acceleration, reducing the shock peak transmitted to the device, thereby protecting the device from impact damage.

[0003] Lattice structures based on triply periodic minimal surfaces (TPMS) are widely used in lightweight structural design and bioimplants due to their advantages such as light weight, high strength, good connectivity, and controllable topology. However, their mechanical properties are relatively poor. How to improve the elastic modulus, yield strength, stress fluctuation stability, and energy absorption capacity of TPMS structures has been a hot topic in this field. Summary of the Invention

[0004] To solve the above problems, the present invention provides a high-efficiency energy absorption gradient curved surface structure, which changes the deformation form of the structure by designing a relative density gradient change, thereby optimizing the energy absorption capacity of the entire structure and improving its ability to withstand impact loads.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A high-efficiency energy absorption gradient curved surface structure adopts a sheet-based TPMS structure and has an internal relative density gradient change structure.

[0007] Furthermore, the Sheet-based TPMS structure is constructed using the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can result in TPMS structures with different volume fractions. The relative density of the TPMS structure can be controlled by changing the parameter C, as shown in Formula 1:

[0008]

[0009] Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled.

[0010] Furthermore, the relative density of the relative density gradient variation structure varies in a range of 30% to 45%.

[0011] Furthermore, the construction process of the IWP-L structure can be realized by Equation 2;

[0012]

[0013] Furthermore, the construction process of the GL structure can be realized by formula 3;

[0014]

[0015] Furthermore, the gradient change of the double parabola structure is divided into two segments, so the function C(x, y, z) is a piecewise function, and C(x, y, z) is a quadratic function with respect to z. For the P-TP structure, its construction process is shown in Formula 4, for the IWP-TP structure, its construction process is shown in Formula 5; for the G-TP structure, its construction process is shown in Formula 6;

[0016]

[0017]

[0018]

[0019] Furthermore, the gradient change of the bilinear DXD structure is divided into two segments, so the function C(x, y, z) is a piecewise linear function. For the P-TL-DXD structure, its modeling process is shown in Formula 7; for the IWP-TL-DXD structure, its modeling process is shown in Formula 8; for the G-TL-DXD structure, its modeling process is shown in Formula 9;

[0020]

[0021]

[0022]

[0023] Furthermore, the gradient change of the bilinear XDX structure is divided into two segments, and the function C(x, y, z) is a piecewise linear function. For the P-TL-XDX structure, its modeling process is shown in Formula 10; for the IWP-TL-XDX structure, its modeling process is shown in Formula 11; for the G-TL-XDX structure, its modeling process is shown in Formula 12.

[0024]

[0025]

[0026]

[0027] The present invention provides a method for improving the mechanical properties of a TPMS structure. Specifically, the method changes the deformation form of the structure by designing a relative density gradient change, thereby optimizing the energy absorption capacity of the entire structure and improving its ability to withstand impact loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the relationship between the relative density of the gradient structure and the height L.

[0029] Figure 2 is the relationship between the structure volume fraction and the parameter C.

[0030] Figure 3 This is a gradient TPMS structure sample;

[0031] In the figure: (a) PL structure; (b) P-TP structure; (c) P-TL-DXD structure; (d) P-TL-XDX structure; (e) IWP-L structure; (f) IWP-TP structure; (g) IWP-TL-DXD structure; (h) IWP-TL-XDX structure; (i) GL structure; (j) G-TP structure; (k) G-TL-DXD structure; (l) G-TL-XDX structure.

[0032] Figure 4 The repeatability of the experimental results of the P structure.

[0033] Figure 5 Stress-strain curves for uniform and gradient TPMS structures;

[0034] In the figure: (a) P structure and gradient P structure; (b) IWP structure and gradient IWP structure; (c) G structure and gradient G structure.

[0035] Figure 6 Specific energy absorption-displacement curves of uniform and gradient TPMS structures;

[0036] In the figure: (a) P structure and gradient P structure; (b) IWP structure and gradient IWP structure; (c) G structure and gradient G structure.

[0037] Figure 7 This is the SEM analysis of the P sample;

[0038] In the figure: (a) magnified 7 times; (b) magnified 12 times; (c) magnified 23 times; (d) magnified 160 times.

[0039] Figure 8 This is the SEM analysis of the IWP sample;

[0040] In the figure: (a) magnified 7 times; (b) magnified 14 times; (c) magnified 30 times; (d) magnified 160 times.

[0041] Figure 9 is the SEM analysis picture of sample G;

[0042] In the figure: (a) magnified 7 times; (b) magnified 11 times; (c) magnified 20 times; (d) magnified 160 times.

[0043] Figure 10 This is the deformation diagram of the TPMS structure under the second impact load;

[0044] In the figure: (a) G structure; (b) GL structure. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0046] Example 1

[0047] (1) TPMS structural dimensions and relative density gradient change design

[0048] This embodiment selects three TPMS structures (G structure, IWP structure and P structure) for relative density gradient design. The design of TPMS structure size and relative density takes into account the requirements of SHPB experiment and metal 3D printing process and accuracy. The maximum length of the cross section of the rectangular sample should be less than the diameter of the waveguide rod. The maximum length of the cross section of the structure designed in this embodiment is The waveguide rod diameter is 50 mm. To better reflect the impact of the TPMS structure's relative density gradient on its mechanical properties, this embodiment adopts a height design of L = 35 mm. The relative density of the uniform TPMS structure is 37.5%, and the relative density of the gradient TPMS structure varies from 30% to 45%. The dimensions of all structures are 21 mm × 21 mm × 35 mm.

[0049] This embodiment designs 4 kinds of relative density gradient gradual change forms, such as Figure 1 As shown. Linear means that the relative density of the structure changes monotonically along the height direction. The three linear gradient TPMS structures are named PL, IWP-L and GL. Double parabola means that the relative density of the structure changes parabolically with a gradually increasing slope within 0-0.5L, and changes parabolically with a gradually decreasing slope within 0.5L-L. Overall, it increases monotonically along the height direction. The three double parabola gradient TPMS structures are named P-TP, IWP-TP and G-TP. Double linear DXD means that the relative density of the structure changes linearly from 45% to 30% within 0-0.5L, and from 30% to 45% within 0.5L-1L. Overall, it first decreases and then increases along the height direction. The three double linear DXD gradient TPMS structures are named P-TL-DXD, IWP-TL-DXD and G-TL-DXD. The bilinear XDX indicates that the relative density of the structure changes linearly from 30% to 45% within 0-0.5L, and from 45% to 30% within 0.5L-1L. As a whole, it first increases and then decreases along the height direction. The three bilinear XDX gradient TPMS structures are named P-TL-XDX, IWP-TL-XDX and G-TL-XDX.

[0050] (2) Gradient TPMS structure modeling

[0051] according to Figure 1 The relative density gradient form designed in the paper is used to model the TPMS structure using the sheet-based TPMS structure modeling method. Among them, the sheet-based TPMS structure can be constructed by the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can obtain TPMS structures with different volume fractions. The relationship between the volume fraction of the G structure, P structure and IWP structure and the parameter C is as follows: Figure 2 As shown in the figure, the volume fraction of the TPMS structure is linearly related to the parameter C. For TPMS structures made of the same material, the same volume fraction means the same relative density. Therefore, the relative density of the TPMS structure can be controlled by changing the parameter C, as shown in Formula 1:

[0052]

[0053] Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled.

[0054] The three TPMS structures all have four gradient change forms, so there are a total of 3×4=12 gradient structures. The modeling process of various gradient change forms of TPMS structures is described below.

[0055] For the IWP-L structure, when the relative density is 30%, the parameter C = 1.135, and when the relative density is 45%, the parameter C = 1.678. C(x, y, z) is a linear function of z. Based on the relationship between relative density and parameter C, we obtain C(x, y, z) = 543 / 35000 × z + 1.135. Therefore, the IWP-L structure construction process can be implemented using Equation 2. For the GL structure, when the relative density is 30%, the parameter C = 0.466, and when the relative density is 45%, the parameter C = 0.694. C(x, y, z) is a linear function of z. Based on the relationship between relative density and parameter C, we obtain C(x, y, z) = 57 / 8750 × z + 0.466. The GL structure construction process is shown in Equation 3.

[0056]

[0057]

[0058] The gradient change of the double parabola structure is divided into two segments, so the function C(x, y, z) is a piecewise function, and C(x, y, z) is a quadratic function about z. For the P-TP structure, when the relative density of the structure is 37.5%, the parameter C = 0.656, then in the interval [0, 0.5L], C(x, y, z) = 13 / 30625×z 2 +0.526, on the interval [0.5L, L], C(x, y, z) = -131 / 306250×z 2 +131 / 4375×z+0.263, the construction process of the P-TP structure is shown in Formula 4. For the IWP-TP structure, when the relative density of the structure is 37.5%, the parameter C=1.406, then in the interval [0,0.5L], C(x,y,z)=271 / 306250×z 2 +1.135, on the interval [0.5L, L], C(x, y, z) = -136 / 153125×z 2+272 / 4375×z+0.59, the construction process of the IWP-TP structure is shown in Formula 5. For the G-TP structure, when the relative density of the structure is 37.5%, the parameter C=0.58, then in the interval [0,0.5L], C(x,y,z)=57 / 153125×z 2 +0.466, on the interval [0.5L, L], C(x, y, z) = -57 / 153125×z 2 +114 / 4375×z+0.238, the construction process of the G-TP structure is shown in Formula 6.

[0059]

[0060]

[0061]

[0062] The gradient change of the bilinear DXD structure is divided into two segments, so the function C(x, y, z) is a piecewise linear function. For the P-TL-DXD structure, on the interval [0, 0.5L], C(x, y, z) = -261 / 17500 × z + 0.787, and on the interval [0.5L, L], C(x, y, z) = 261 / 17500 × z + 0.265. The modeling process of the structure is shown in Equation 7. For the IWP-TL-DXD structure, on the interval [0, 0.5L], C(x, y, z) = -543 / 17500 × z + 1.678, and on the interval [0.5L, L], C(x, y, z) = 543 / 17500 × z + 0.592. The modeling process of the structure is shown in Equation 8. For the G-TL-DXD structure, on the interval [0, 0.5L], C(x, y, z) = -57 / 4375×z + 0.694, and on the interval [0.5L, L], C(x, y, z) = 57 / 4375×z + 0.238. The modeling process of the structure is shown in Formula 9.

[0063]

[0064]

[0065]

[0066] The gradient change of the bilinear XDX structure is divided into two segments, so the function C(x, y, z) is a piecewise linear function. For the P-TL-XDX structure, on the interval [0, 0.5L], C(x, y, z) = 261 / 17500 × z + 0.526, and on the interval [0.5L, L], C(x, y, z) = -261 / 17500 × z + 1.048. The modeling process of the structure is shown in Equation 10. For the IWP-TL-XDX structure, on the interval [0, 0.5L], C(x, y, z) = 543 / 17500 × z + 1.135, and on the interval [0.5L, L], C(x, y, z) = -543 / 17500 × z + 2.221. The modeling process of the structure is shown in Equation 11. For the G-TL-XDX structure, on the interval [0, 0.5L], C(x, y, z) = 57 / 4375 × z + 0.466, and on the interval [0.5L, L], C(x, y, z) = -57 / 4375 × z + 0.922. The modeling process of the structure is shown in Formula 12.

[0067]

[0068]

[0069]

[0070] The gradient TPMS structure was modeled in the mathematical software Mathematica. For a gradient structure where C(x, y, z) is a piecewise function, this method was used to generate two submodels, each 17.5 mm high. These submodels were then imported into HyperMesh for assembly and contact surface meshing, ultimately resulting in a complete gradient structure. Ultimately, the geometric models of 12 different gradient TPMS structures were obtained.

[0071] 3D printing to prepare TPMS structure

[0072] (1) Sample preparation

[0073] The gradient TPMS structure is prepared using Selective Laser Melting (SLM) technology. During the sample preparation process, the molding chamber needs to be filled with nitrogen or argon to protect the molten metal powder from oxidation. The main steps of SLM are: first, the grid model needs to be divided into a series of parallel slice models, and then a filling scanning path is generated according to the boundary contour of the slice model. Finally, the laser selectively melts the metal powder along the path to construct a two-dimensional slice that constitutes the three-dimensional model. After the scan is completed, the building platform will drop, and then a new layer of metal powder will be laid, and the laser will scan a new layer. These steps are repeated until the sample is printed. This embodiment uses the EP-M250 metal 3D printer produced by Yijia 3D Technology Co., Ltd. to prepare the experimental parts. The printing material is AlSi10Mg. The molding chamber size of this model machine is 262×262×370mm 3 , ensuring that printed experimental parts belong to the same batch, minimizing the impact of the preparation environment on the mechanical properties of the structure; the laser power is 200W, the spot diameter is 70μm, the maximum scanning speed is 8m / s, and the powder layer thickness is 20-100μm. The small spot diameter and layer thickness ensure high sample density, high dimensional accuracy, and good print quality. After printing, the sample is heat treated to improve strength and rigidity, while also increasing the sample's ductility.

[0074] 12 kinds of gradient TPMS structures were prepared using SLM technology. Figure 3 As shown. Figure 3 It can be seen that metal 3D printing better reflects the unique geometric surface characteristics of the TPMS structure. There are no obvious defects on the surface of the sample when observed with the naked eye. The internal pores are interconnected, and the gradient change of the structure can be clearly seen. Overall, the printing effect is good.

[0075] (2) Sample size and surface morphology analysis

[0076] In order to evaluate the final printing effect of the gradient TPMS structure and meet the needs of subsequent SHPB experimental data processing and mechanical property analysis, the geometric dimensions and mass of the gradient TPMS sample were measured in this example and compared with the model design quality, as shown in Table 1.

[0077] Table 1 Geometric dimensions and mass of gradient TPMS samples

[0078]

[0079] The design size of the gradient TPMS structure is 21×21×35mm 3The data in the table shows that the dimensions of the 12 gradient TPMS samples in the xy plane are nearly identical to those of the CAD models, with a difference of no more than 0.15mm. However, the z-axis dimensions of the gradient structures are generally 0.2 to 0.3mm larger than the CAD models. This is primarily due to the fact that the printed samples were parallel to the z-axis, leaving some margin when the printed samples were cut from the build platform. Therefore, the z-axis dimensions of the gradient structures are larger than the designed dimensions. Since the dimensional errors of the samples in the x, y, and z directions all exceeded 1%, falling within an acceptable range, the sample dimensions met the experimental requirements. Regarding structural quality, the three gradient TPMS structures all exceeded the designed mass due to excess metal particles and unmelted metal powder on the sample surfaces. With the exception of the gradient IWP structure, the quality errors of the other two gradient TPMS structures were all within 5%. Due to their larger internal pores and simpler geometric configurations compared to the IWP structure, these structures have fewer metal particles attached to their surfaces, resulting in smaller errors. The gradient IWP structure, however, has a more complex spatial topology and larger surface area, making it more susceptible to the presence of excess metal particles and unmelted metal powder on the surface and boundaries of the structure during printing, leading to larger errors. The metal particles and powder attached to the gradient specimens did not significantly affect their mechanical properties and remained within an acceptable range.

[0080] The surface morphology of the sample was observed using a desktop scanning electron microscope (SEM), the model of the SEM was HITACHI SU3500. In this embodiment, the surface morphology of the uniform P sample, IWP sample and G sample was analyzed. The SEM analysis images of the three TPMS structures are shown in Figure 1. Figure 7 , Figure 8 and Figure 9 As shown. Figures 7 to 9 As can be seen from Figure (a), the three TPMS samples have a very smooth surface as a whole, with obvious minimal surface geometric features, and no defects such as holes, cracks, and warping caused by printing were observed, indicating that the metal 3D printing technology used in this paper has good complex structure manufacturing capabilities. Figures 7 to 9Figure (b) shows the SEM images of the unit cells of the three TPMS structures. The surface of the unit cell is relatively rough and excess metal particles are observed at the boundary, as shown in the circle in the figure. Among them, the metal particles on the surface of the P structure and the G structure are relatively small and small in size, while the IWP structure has many large-volume metal particles at the boundary along the horizontal direction, and the surface of the nearby area is uneven. The main reason is that the boundary is parallel to the building platform. When performing unsupported printing, the loose metal powder cannot support the solidified metal particles at the horizontal interface, resulting in the accumulation of more metal particles. This is the main reason for the significant increase in the mass of the IWP sample and is also the technical difficulty that needs to be solved in SLM manufacturing. Figures 7 to 9 Figure (c) is an enlarged view of the local boundary of the unit cell, where the attached spherical metal particles can be observed more clearly. Figures 7 to 9 Figure (d) is an SEM image of the smooth surface of the TPMS sample, with a magnification of 160 times. It can be observed that the sample has a high degree of densification, without manufacturing defects such as pores and cracks, and the printing effect is good.

[0081] In summary, the geometric shape and structural dimensions of the TPMS specimen are well consistent with the CAD design model, the gradient change characteristics are obvious, the specimen surface is smooth and has no macro defects, which meets the experimental requirements and can be used for SHPB impact testing.

[0082] SHPB dynamic impact test

[0083] (1) Experimental methods

[0084] Using Split Hopkinson Pressure Bar (SHPB) technology, the specimen is placed between an incident and transmission bar, keeping them in close contact. A gas cannon acts as a driving device, applying an initial velocity to the impact bar. When the impact bar strikes the incident bar, a rectangular stress pulse is generated. This pulse propagates along the incident bar until it strikes the specimen. Due to material impedance mismatch, part of the incident pulse is reflected at the incident bar / specimen interface, while another portion propagates through the specimen, reaching the transmission bar as a transmission pulse that continues to propagate until it reaches the end of the transmission bar. Strain gauges located on the incident and transmission bars collect the pulse signals. High-speed photography is used to capture the specimen's deformation and failure at the moment of impact. Using the three-wave method, the temporal evolution of stress, strain, and strain rate on the specimen is determined.

[0085] First, single impact tests were conducted on 12 gradient TPMS structures and 3 uniform TPMS structures. The stability and reliability of the data measurement were guaranteed while maintaining the maximum inflation pressure of the experimental device. The inflation pressure in the high-pressure chamber was 0.17 MPa. At this pressure, the muzzle velocity of the impact rod was 12.7 m / s, corresponding to an average engineering plastic strain rate of 228 s.-1 , the sampling frequency is set to 5MHz, and the number of sampling points is set to 10000. Then, the mechanical performance responses of the G structure and GL structure under multiple impact loads are analyzed at the same inflation pressure.

[0086] SHPB impact test results

[0087] (1) Analysis of single impact test results

[0088] In order to verify the repeatability of the experimental results, this embodiment conducted two impact tests on the P structure printed in the same batch. The results are as follows: Figure 4 As shown in the figure, when the strain is greater than 0.01, the stress-strain curves of the two impact tests follow the same trend and have little difference. There is a significant difference between the two experimental results in the early stages of structural deformation, primarily due to the fact that the mechanical properties of the samples produced using SLM technology are not completely identical. However, this difference has little impact on the overall mechanical properties of the structure. Therefore, the current experimental method can produce reliable and reproducible experimental results.

[0089] In this embodiment, single impact tests were conducted on 12 gradient TPMS structures and 3 uniform TPMS structures. The stress-strain curves of the structures are shown in Figure 2. Figure 5 In order to meet the requirements of 3D printing for sample size and wall thickness, the TPMS structure designed in this embodiment has a higher relative density, resulting in greater strength and stiffness. Under this experimental condition, the compression deformation of the structure is small. Figure 5 It can be seen that the maximum compressive strain is about 0.055, so the stress-strain curve does not show a plateau stage and a densification stage. In order to facilitate the analysis and comparison of the mechanical properties of different structures, the specific energy absorption of the structure is as follows Figure 6 shown.

[0090] Depend on Figure 6 (a) It can be seen that when the compression displacement is greater than 0.74 mm, the SEA of the P-TP structure is always greater than that of the P structure, but the SEA of the other three gradient structures is always lower than that of the P structure; when the compression displacement is greater than 1.4 mm, the SEA of the P-TL-XDX structure is greater than that of the P-TL-DXD structure, and the PL structure has the smallest SEA. Figure 6 (b) It can be seen that the SEA difference between the uniform IWP structure and the gradient IWP structure is small, mainly due to two reasons. On the one hand, the deformation of the structure is small; on the other hand, the IWP structure has a large surface area. Within the same relative density change range, the wall thickness of the structure changes less. The SEA curves of the four gradient IWP structures all intersect with the SEA curve of the IWP structure. Among them, the SEA curve of the IWP-TL-XDX structure is closer to the IWP structure. Figure 6As shown in Figure (c), the SEA of the G-TL-XDX structure is consistently greater than that of the G structure. The SEA curves of the other three gradient G structures intersect with the G structure and are all greater than those of the G structure at the initial stage of compression deformation. When the compression displacement exceeds 1.2 mm, the SEA of the GL structure is greater than that of the G-TP structure, and the G-TL-DXD structure has the smallest SEA. The above analysis demonstrates that relative density gradients can improve the mechanical properties of structures, and the optimal design solutions vary for different TPMS structures.

[0091] This embodiment uses a high-speed photography system to record the impact deformation process of the structure. The three uniform TPMS structures show an overall uniform deformation pattern without obvious damage or destruction. For structures with linear relative density changes, plastic deformation mainly occurs in the low-density area, among which the unit cells with low relative density of the PL structure are completely destroyed, and metal blocks fall off. The lowest density area of ​​the IWP-L structure is compacted, but the unit cells are not completely destroyed; the GL structure mainly undergoes plastic deformation, and the overall structure is relatively intact. For structures with biparabolic relative density changes, plastic deformation mainly occurs in the low-density area, the lowest density area of ​​the IWP-TP structure is compacted, and the low-density area structures of P-TP and G-TP remain relatively intact. For structures with bilinear relative density DXD changes, obvious plastic deformation can be observed in the middle area of ​​the three gradient TPMS structures, among which the area with the lowest relative density in the middle of the IWP-TL-DXD structure breaks and cannot continue to bear the load. For the structure with bilinear relative density XDX variation, plastic deformation mainly occurs in the low-density area near the end face of the transmission rod. Among them, the unit cell near the transmission rod of the P-TL-XDX structure is completely destroyed, while the unit cell near the incident rod is less deformed and the overall structure is relatively intact; the structure near the transmission rod area of ​​the IWP-TL-XDX undergoes plastic deformation first, followed by the structure near the incident rod area; the structure near the transmission rod area of ​​the G-TL-XDX structure undergoes larger deformation, and the structure near the incident rod area undergoes smaller deformation.

[0092] In summary, the relative density gradient change design can change the deformation form of the structure, and the energy absorption capacity of the partial gradient structure is better than that of the uniform structure.

[0093] (2) Analysis of multiple impact test results

[0094] First, we selected two TPMS structures, G and GL, which had undergone the first impact. Then, we conducted a second impact test on these two structures at the same inflation pressure. We used high-speed photography to record the deformation and failure process of the structures. Figure 10 shown.

[0095] exist Figure 10In the figure, the left side is the incident rod and the right side is the transmission rod. Under the second impact load, the G structure undergoes a large compression deformation and obvious shear failure. The shear band is as follows: Figure 10 As shown in the dotted box in (a), the structure can no longer withstand the impact load. The deformation and damage of the GL structure under the second impact load mainly occurs in the low-density area, and the structure shows a layer-by-layer damage pattern. The damage area is as follows: Figure 10 As shown in the dotted box in (b), the structure can still continue to withstand the impact load at this time.

[0096] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A high-efficiency energy absorption gradient curved surface structure, characterized by: The curved surface structure adopts a sheet-based TPMS structure with a relative density gradient change structure inside; The sheet-based TPMS structure is constructed using the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can yield TPMS structures with different volume fractions. By changing the parameter C, the relative density of the TPMS structure can be controlled, as shown in Formula 1: Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled. The construction process of IWP-L structure can be realized by formula 2; 2. A high-efficiency energy absorption gradient curved surface structure, characterized by: The curved surface structure adopts a sheet-based TPMS structure with a relative density gradient change structure inside; The sheet-based TPMS structure is constructed using the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can yield TPMS structures with different volume fractions. By changing the parameter C, the relative density of the TPMS structure can be controlled, as shown in Formula 1: Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled. The construction process of the GL structure can be achieved through formula 3; 3. A high-efficiency energy absorption gradient curved surface structure, characterized by: The curved surface structure adopts a sheet-based TPMS structure with a relative density gradient change structure inside; The sheet-based TPMS structure is constructed using the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can yield TPMS structures with different volume fractions. By changing the parameter C, the relative density of the TPMS structure can be controlled, as shown in Formula 1: Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled. The gradient change of the double parabola structure is divided into two segments, so the function C(x, y, z) is a piecewise function, and C(x, y, z) is a quadratic function with respect to z. For the P-TP structure, its construction process is shown in Formula 4, for the IWP-TP structure, its construction process is shown in Formula 5; for the G-TP structure, its construction process is shown in Formula 6; ， Where L is the structure height.

4. A high-efficiency energy absorption gradient curved surface structure, characterized by: The curved surface structure adopts a sheet-based TPMS structure with a relative density gradient change structure inside; The sheet-based TPMS structure is constructed using the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can yield TPMS structures with different volume fractions. By changing the parameter C, the relative density of the TPMS structure can be controlled, as shown in Formula 1: Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled. The gradient change of the bilinear DXD structure is divided into two segments, so the function C(x, y, z) is a piecewise linear function. For the P-TL-DXD structure, its modeling process is shown in Formula 7; for the IWP-TL-DXD structure, its modeling process is shown in Formula 8; for the G-TL-DXD structure, its modeling process is shown in Formula 9; ， Where L is the structure height.

5. A high-efficiency energy absorption gradient curved surface structure, characterized by: The curved surface structure adopts a sheet-based TPMS structure with a relative density gradient change structure inside; The sheet-based TPMS structure is constructed using the inequality -C≤φ≤C, where φ is the implicit function equation of the minimal surface and C (C>0) is a constant used to control the offset of the minimal surface. Setting different C values ​​can yield TPMS structures with different volume fractions. By changing the parameter C, the relative density of the TPMS structure can be controlled, as shown in Formula 1: Where C(x,y,z) represents a function related to the spatial coordinates x,y,z. By designing the function C(x,y,z), the variation of the relative density of the TPMS structure in the three directions can be controlled. The gradient change of the bilinear XDX structure is divided into two segments, so the function C(x, y, z) is a piecewise linear function. For the P-TL-XDX structure, its modeling process is shown in Formula 10; for the IWP-TL-XDX structure, its modeling process is shown in Formula 11; for the G-TL-XDX structure, its modeling process is shown in Formula 12. Where L is the structure height.

6. The high-efficiency energy absorption gradient curved surface structure according to any one of claims 1 to 5, characterized in that: The relative density of the relative density gradient variation structure varies in a range of 30% to 45%.

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