Knee-joint-imitating anti-impact structure based on shear thickening fluid

Abstract

The utility model relates to a knee-joint-imitating anti-impact structure based on shear thickening fluid, and belongs to the technical field of buffering and energy absorption. The structure comprises a main body block body, a soft shell cavity and shear thickening liquid, the shear thickening fluid is sealed in the soft shell cavity, and the soft shell cavity is assembled and filled into the main body block; the main body block body is formed by connecting an upper block body, a lower block body and a thin-wall connecting curved beam and is integrally manufactured by a 3D printing technology; the bottom surfaces of the upper block body and the lower block body are square; the inner side interfaces of the upper block body and the lower block body are formed by stretching a cosine function curve of one cycle along the direction vertical to the paper surface; and the internal interface of the thin-wall connecting curved beam is formed by stretching a cosine function curve of one period along the direction vertical to the paper surface. The special rigidity characteristic of the knee joint structure is utilized, the shear thickening fluid is flexibly packaged, a deformation area is expanded, excellent impact resistance is achieved, and the knee joint structure has the advantages of being light in weight, controllable in size and easy to assemble.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of buffering and energy absorption, and particularly relates to a knee joint-imitating impact-resistant structure based on shear thickening fluid. BACKGROUND

[0002] In the field of modern structure design, in order to reduce the adverse effects of mechanical impact, the impact-resistant structure based on bionics has been widely applied in the industries of aerospace, ships and automobiles, bionic robots, etc.

[0003] In recent years, people have begun to pay attention to the application of shear thickening fluid in the field of impact-resistant energy absorption of liquid-solid coupling structures. Chinese patent CN218764864U (a high-performance soft bulletproof layer composite structure) discloses a high-performance soft bulletproof layer composite structure, which can be used in soft explosion-proof tanks, explosion-proof blankets and other safety protection products. Chinese patent CN209079840U (a rigid-flexible net-shaped automobile safety bumper) discloses a rigid-flexible net-shaped automobile safety bumper, which fills shear thickening fluid into a rubber airbag, and combines with a rigid base to form a structure for buffering and energy absorption after the automobile bumper is impacted. The existing impact-resistant structure based on shear thickening fluid has the following problems: the shear thickening fluid is not effectively encapsulated and is directly exposed to the air, causing the shear thickening fluid to denature; the hard thin-walled material encapsulation structure has the problems of small effective energy absorption area and poor stability of the structure; the volume and weight of the structure are too large, making it difficult to be lightweight. SUMMARY

[0004] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0005] A knee joint-imitating impact-resistant structure based on shear thickening fluid, comprising: a main block, a soft shell cavity and shear thickening fluid; the shear thickening fluid is enclosed in the soft shell cavity, and the soft shell cavity is assembled and filled into the main block.

[0006] The utility model has the advantages of:

[0007] The utility model sets a bionic liquid-solid coupling interface, expands the effective area of buffering and energy absorption, and improves the local failure problem of the pure solid structure; sets a thin-walled connecting curved beam and a soft shell cavity, avoids the denaturation of the shear thickening fluid, realizes a low-rigidity connection and a flexible encapsulation method, expands the deformation energy absorption area, enhances the stability of the structure, and improves the problems of large volume and high cost in the current liquid-solid coupling structure design. The utility model is simple to assemble, the weight of a single structure is not more than 10 grams, the cost is low, the parameters of the liquid-solid coupling interface can be adjusted, and excellent impact resistance is realized. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1For the three-dimensional view of the utility model, wherein, 1 - main body block, 2 - soft shell cavity, 3 - shear thickening fluid, 4 - liquid-solid coupling interface, 11 - upper block, 12 - lower block, 13 - the inner side interface of upper block and lower block, 14 - thin wall connecting curved beam, 15 - the external interface of thin wall connecting curved beam, 16 - the internal interface of thin wall connecting curved beam, 21 - the upper and lower interface of soft shell cavity, 22 - the two side interfaces of soft shell cavity;

[0009] Figure 2 For the oblique view of the utility model, wherein, 2 - soft shell cavity, 11 - upper block, 12 - lower block, 13 - the inner side interface of upper block and lower block, 14 - thin wall connecting curved beam, 15 - the external interface of thin wall connecting curved beam;

[0010] Figure 3 For the plan view of the utility model;

[0011] Figure 4 For Figure 3 The A-A direction half sectional view in the middle, wherein, 2 - soft shell cavity, 3 - shear thickening fluid, 4 - liquid-solid coupling interface, 11 - upper block, 12 - lower block, 13 - the inner side interface of upper block and lower block;

[0012] Figure 5 For Figure 4 The B-B direction half sectional view in the middle, wherein, 2 - soft shell cavity, 3 - shear thickening fluid, 4 - liquid-solid coupling interface, 11 - upper block, 12 - lower block, 13 - the inner side interface of upper block and lower block, 14 - thin wall connecting curved beam;

[0013] Figure 6 It is the viscosity variation curve of shear thickening fluid that the mass fraction of particle is 67%;

[0014] Figure 7 It is the protection effect schematic diagram of the knee joint impact resistance structure based on shear thickening fluid under 800 millimeter drop hammer impact;

[0015] Figure 8 It is the three-dimensional view when the amplitude of the inner side interface 13 of upper block and lower block of the utility model is set as 0 millimeter;

[0016] Figure 9 It is the three-dimensional view when the amplitude of the inner side interface 13 of upper block and lower block of the utility model is set as 3 millimeter. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the utility model clearer and more apparent, the utility model will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the utility model and not to limit the utility model. In addition, the technical features involved in each embodiment of the utility model described below can be combined with each other as long as they do not conflict with each other.

[0018] The utility model discloses Figure 1 、 Figure 2 、 Figure 3 As shown in the utility model discloses a knee joint impact resistance structure based on shear thickening fluid includes main body block 1, soft shell cavity 2 and shear thickening fluid 3. In which, shear thickening fluid 3 is enclosed in soft shell cavity 2, soft shell cavity 2 can be assembled and filled to main body block 1. Figure 2 It is the oblique view of the utility model knee joint impact resistance structure based on shear thickening fluid.

[0019] Main body block 1 is connected by upper block 11, lower block 12 and thin wall connecting curved beam 14, and is integrally made by 3D printing technology. Main body block 1 is solid full filling thermoplastic polyurethane elastomer (TPU 95A) or other polymer, which can keep lightweight while bearing external impact. The bottom surface shape of upper block 11 and lower block 12 is all square of 15mm × 15mm, and the height is 8mm, which can also be other sizes, such as the bottom surface of upper block 11 and lower block 12 is set to other sizes, and the size of soft shell cavity 2 also needs to be adjusted (see Figure 8 、 Figure 9 );The inside interface 13 of upper block and lower block is formed by stretching 15mm along the vertical paper direction by a periodic cosine function curve, and the amplitude of the cosine curve is 1.5mm, and the period is 15mm. The thickness of thin wall connecting curved beam 14 is 0.6mm, which is used to realize flexible support and high-efficiency energy consumption. The inside interface 16 of thin wall connecting curved beam is formed by stretching 15mm along the vertical paper direction by a periodic cosine function curve, and the parameters of the cosine curve are amplitude 4mm and period 24mm.

[0020] Soft shell cavity 2 is made of silicone elastomer (such as silicone rubber) or cured by thermoplastic elastomer material, which is suitable for large deformation scene and beneficial to fluid extension, and its shape is symmetrical along the central vertical line. The two side interfaces 22 of soft shell cavity and the upper and lower interfaces 21 of soft shell cavity are tightly combined with the inside interface 16 of thin wall connecting curved beam and the inside interface 13 of upper block and lower block. The shape of soft shell cavity 2, liquid-solid coupling interface 4 and internally filled shear thickening fluid 3 is as shown in Figure 4 、 Figure 5The inner space of the soft shell cavity 2 is formed by inwardly translating the inner interface 16 of the thin-walled connecting curved beam and the inner interface 13 of the upper and lower block bodies by 2 mm, respectively. The inner space of the soft shell cavity 2 is filled with the shear thickening liquid 3, and the shape of the soft shell cavity 2 determines the internal shape of the shear thickening liquid 3, as shown in Figure 1 .

[0021] The inner interface 16 of the thin-walled connecting curved beam and the inner interface 13 of the upper and lower block bodies are both formed by stretching a cosine curve in a direction perpendicular to a straight surface, and the shape thereof imitates the curved surface shape of the femur and tibia end portions. The upper and lower interfaces 21 of the soft shell cavity and the two side interfaces 22 of the soft shell cavity can be kept in close contact with the inner interface 13 of the upper and lower block bodies and the inner interface 16 of the thin-walled connecting curved beam, and the assembly can be achieved by directly filling the soft shell cavity 2 into the main block body 1.

[0022] The shear thickening liquid 3 has non-Newtonian viscosity dissipation characteristics and a high bulk modulus, and is used to absorb dynamic impact energy. The shear thickening liquid 3 filled in the soft shell cavity 2 is prepared by using polyethylene glycol with a molecular weight of 200 as a base liquid and spherical silica particles (with an average particle size of 0.3 microns) as a dispersed phase, and the mass fraction of the particles is 67%. The maximum stroke of the pressure receiving part of the shear thickening liquid 3 is 4 mm. The fluid has low viscosity at low shear rate and the viscosity rapidly increases at high shear rate, thereby absorbing impact energy.

[0023] The utility model mainly bears pressure load. When bearing pressure, the main block body 1 keeps the structure as a whole stable, the soft shell cavity 2 produces large deformation due to pressure, the shear thickening liquid 3 in the interior is extruded to produce shear flow and mainly flows into the two side cavities, so that the structure shows good impact resistance and stability.

[0024] Shear thickening liquid rheological property test: Figure 6 The viscosity change curve of the shear thickening liquid with a particle mass fraction of 67%. In order to determine the rheological property and material property of the shear thickening liquid, the viscosity change of the shear thickening liquid with a particle mass fraction of 67% at different shear rates is tested by using an MCR302 rheometer. The shear rate of the rheological test rotor is set to 0.01 / s to 120 / s, and the viscosity change curve of the shear thickening liquid is obtained as shown in Figure 6 .

[0025] Impact resistance test: to verify the impact resistance of the utility model, the following test is carried out. The drop hammer test device is used to study the knee joint impact resistance structure based on shear thickening fluid. The knee joint impact resistance structure based on shear thickening fluid is placed on the impact test bench. During the experiment, the drop hammer with a mass of 0.54 kg freely falls from a height of 800 mm. The impact force is detected by the force sensor placed below the knee joint impact resistance structure based on shear thickening fluid. The friction is ignored. The oscilloscope is used to record the force signal during the impact process. The test results are shown in Figure 7 Figure 7 The test results show that the shear thickening characteristics of the shear thickening fluid significantly reduce the energy transmitted to the block by the impact. The peak force attenuation of the interface below the knee joint impact resistance structure based on shear thickening fluid is more than 85%.

[0026] Preferably, to further improve the applicability in multiple scenarios, the utility model can be flexibly adjusted according to the specific application requirements. For example, changing the shape: by changing the shape parameters of the inner interface 13 of the upper block and the lower block and the liquid-solid coupling interface 4, the equivalent stiffness and damping performance of the utility model can be changed.

[0027] The shape of the cosine function curve of the inner interface 13 of the upper block and the lower block is designed according to the stiffness optimization. By adjusting the parameters of the shape of the cosine function curve, different equivalent stiffnesses are achieved. The amplitude of the cosine function curve of the inner interface 13 of the upper block and the lower block can be as low as 0. As shown in Figure 8 The amplitude of the inner interface 13 of the upper block and the lower block is set to 0 mm. As shown in Figure 9 The amplitude of the inner interface 13 of the upper block and the lower block is set to 3 mm.

[0028] The mass fraction of the dispersed phase in the shear thickening fluid can be changed, such as 67% to 72%. The dispersion medium of the shear thickening fluid can be changed, such as setting it to polyethylene glycol with a molecular weight of 200 to 1000, ethylene glycol, sodium chloride, water, glycerol. The dispersed phase of the shear thickening fluid can be changed, such as setting it to silica particles with a particle size of 50 nm to 1000 nm, calcium carbonate, starch, polymethyl methacrylate.

[0029] The utility model is suitable for aerospace, ships, automobiles and bionic robots and other fields.​

Claims

1. A knee-joint-like impact-resistant structure based on shear-thickening fluid, characterized in that, include: The main body (1), the soft shell cavity (2) and the shear thickening liquid (3) are enclosed in the soft shell cavity (2), and the soft shell cavity (2) is assembled and filled into the main body (1).

2. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 1, characterized in that, The main block (1) is composed of an upper block (11), a lower block (12) and a thin-walled connecting curved beam (14), and is manufactured in one piece by 3D printing technology; the bottom shape of the upper block (11) and the lower block (12) are both square; the inner interface (13) of the upper block and the lower block is formed by stretching a cosine function curve of one period along the direction perpendicular to the paper; the inner interface (16) of the thin-walled connecting curved beam (14) is formed by stretching a cosine function curve of one period along the direction perpendicular to the paper.

3. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 1, characterized in that, The soft shell cavity (2) is made of silicone elastomer through curing.

4. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 2, characterized in that, The shape of the soft shell cavity (2) is symmetrical along the central vertical line; the two side interfaces (22) of the soft shell cavity and the upper and lower interfaces (21) of the soft shell cavity are closely fitted with the internal interface (16) of the thin-walled connecting curved beam and the inner side interface (13) of the upper block and the lower block, respectively.

5. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 2, characterized in that, The main block (1) is a solid, fully filled thermoplastic polyurethane elastomer.

6. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 1, characterized in that, The soft shell cavity (2) is made of silicone elastomer or thermoplastic elastomer material.

7. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 1, characterized in that, The shear thickening fluid (3) uses polyethylene glycol, ethylene glycol, sodium chloride, water or glycerol as the base liquid, and silica, calcium carbonate, starch and polymethyl methacrylate particles with a particle size of 50 nm to 1000 nm as the dispersed phase, with a mass fraction of 67% to 72%; its maximum stroke of the pressure-bearing part is 4 mm, exhibits low viscosity at low shear rates, and rapidly increases viscosity at high shear rates, thereby absorbing impact energy.

8. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 2, characterized in that, The shape of the cosine function curve of the inner interface (13) of the upper block and the lower block is designed according to the stiffness optimization. Different equivalent stiffnesses are achieved by adjusting the parameters of the shape of the cosine function curve.

9. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 8, characterized in that, The amplitude of the cosine function curve of the inner interface (13) of the upper block and the lower block is set to 0.

10. The knee-joint-like impact-resistant structure based on shear-thickening fluid according to claim 8, characterized in that, In the shear thickening liquid (3), the particle size of the dispersed phase particles ranges from 0.1 to 10 micrometers.

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