SMA-based non-inflatable tire structure

Abstract

The invention belongs to the field of automobile tire design, and particularly relates to an SMA (Shape Memory Alloy)-based non-inflatable tire structure, which is a non-inflatable tire structure with negative Poisson's ratio characteristic formed by utilizing spatial combination of chirality and fusiform cell elements, is integrally made of an NITI shape memory alloy material and is integrally formed by virtue of an additive manufacturing process. The characteristic of the shape memory alloy material and the characteristic of synchronous increase and decrease of the negative Poisson's ratio are mutually superposed, so that when the material is impacted or vibrated, energy can be effectively absorbed and dissipated, and a good vibration relieving effect is achieved. The innovative design is applied to the automobile tire, so that the bearing stability of the tire under complex road conditions can be ensured, the vibration absorption capacity of the tire can be greatly improved, and the stability and the riding comfort during driving are greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of automobile tire design, and in particular relates to a non-pneumatic tire structure based on SMA. Background Art

[0002] During everyday driving, especially when encountering bumpy roads, tires are frequently subjected to shock and vibration. While conventional tires incorporate internal shock-absorbing mechanisms, the comfort and handling stability they provide are often unsatisfactory. These deficiencies are particularly pronounced during emergency obstacle avoidance and quick turns, making them ineffective in ensuring the safety and comfort of drivers and passengers.

[0003] Given this situation, lightweight and versatile negative Poisson's ratio structures, with their unique properties, have shown great potential for application in the automotive industry. These materials combine numerous advantages, including excellent design flexibility, tensile expansion characteristics, high shear modulus and fracture toughness, strong impact resistance, and noise suppression, offering extraordinary potential for building high-performance, multi-purpose vehicle structures. Unlike ordinary materials, which tend to expand outward when subjected to pressure, negative Poisson's ratio materials experience a reverse contraction reaction, which increases the local density of the material. It is this unusual physical phenomenon that gives these materials their powerful energy absorption capabilities, enabling them to excel in resisting impact loads, effectively reducing the force of the impact and thereby enhancing their impact protection.

[0004] Shape memory alloy superelastic materials have a certain ability to absorb and dissipate energy during the stress-strain cycle. This is mainly because the alloy has a highly symmetrical crystal structure when it is in the austenite phase. When stress is applied, the austenite phase begins to transform into the martensite phase, which has many variants and a relatively complex structure. This phase transition process allows the material to produce a large deformation. When the stress disappears, the martensite phase will reversely transform back to the austenite phase, and the material will return to its original shape, accompanied by energy conversion during the phase transition.

[0005] When shape memory alloys are used to create negative Poisson's ratio structures, this energy absorption and dissipation capability is further enhanced. When subjected to an impact load, the negative Poisson's ratio structure first changes its shape, dispersing the impact energy within the structure. During this process, the shape memory alloy absorbs some of the energy through phase change, enabling the entire structure to better withstand impact and reducing energy reflection. This effectively absorbs and evenly distributes road impact force, significantly improving stability and safety during driving. Therefore, designing a negative Poisson's ratio structure using shape memory alloys is of great significance. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a non-pneumatic tire structure based on shape memory alloys (SMA), which has a negative Poisson's ratio characteristic to better achieve vibration reduction and isolation performance, so as to solve the vibration isolation problem in the vehicle tire structure.

[0007] To achieve the above object, the technical solution of the present invention is as follows: A non-pneumatic tire structure based on SMA is composed of multiple negative Poisson's ratio structural units arranged according to preset rules. The negative Poisson's ratio structural unit is formed by connecting four spindle-shaped unit cells with the top of a chiral unit cell to form a metamaterial chiral unit cell, and then symmetric through a mirror plane perpendicular to the plane of the major and minor axes of the spindle-shaped unit cell's minor axis. The spindle-shaped unit cell is a three-dimensional spindle-shaped unit cell obtained by forming a circular array around the major axis of a planar spindle-shaped unit cell. The chiral unit cell is composed of four ligaments, the central axis of the ligaments being perpendicular to the outer edge, and a rectangle is constructed through the middle, with adjacent ligaments in contact with each other.

[0008] Furthermore, after being bent and deformed by 22.5°, the negative Poisson's ratio structural units are arranged in a circular array with the bending center as the axis to form a non-pneumatic tire structure.

[0009] Furthermore, NITI shape memory alloy material is used.

[0010] Furthermore, the Young's modulus of austenite is 60 GPa, and the Young's modulus of martensite is 45 GPa.

[0011] Furthermore, the Poisson's ratio of austenite is 0.33, and the Poisson's ratio of martensite is 0.33.

[0012] Furthermore, the thermal expansion coefficient of austenite is 2.2e -6 ℃ -1 , the thermal expansion coefficient of martensite is 2.2e -6 ℃ -1 .

[0013] Furthermore, the austenite transformation starting temperature is 32°C and the ending temperature is 78°C.

[0014] Furthermore, the martensitic transformation starting temperature is 45°C and the ending temperature is -7°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) When the structure of the present invention is subjected to load, the chiral unit cells twist, causing the structure to shrink and deform inward, increasing the overall density. This change helps to better resist load impact, effectively reducing the maximum stress on the structure, and preventing fatigue and damage to the tire material under high loads.

[0016] (2) When an external force is applied to the structure of the present invention, it exhibits a unique negative Poisson's ratio behavior. Specifically, when compressed perpendicular to the direction of the force, it exhibits a contraction tendency in the lateral direction; and when tensile, it exhibits an expansion state. During the deformation of the negative Poisson's ratio structure, the shape and size of the internal voids change. The superelasticity of shape memory alloys can adapt to such complex deformations because they can maintain elasticity over a large strain range. In addition, when the shape memory alloy is present in the negative Poisson's ratio structure, it can provide the structure with additional elastic recovery force, making it easier for the negative Poisson's ratio structure to return to its original state after deformation.

[0017] (3) The structure of the present invention combines the excellent performance of the negative Poisson's ratio structure in terms of tensile and compressive resistance, sound absorption and vibration isolation, as well as the advantages of the chiral structure in enhancing the mechanical properties of the material and improving the material life, further improving the mechanical properties of the support structure and enhancing the overall strength and stability of the structure.

[0018] (4) The properties of the memory alloy material and the synchronous increase and decrease of the negative Poisson's ratio structure are superimposed on each other, which enables the material to effectively absorb and dissipate energy when subjected to impact or vibration, thereby achieving a better vibration reduction effect. Applying this innovative design to automobile tires can not only ensure the tires have load-bearing stability under complex road conditions, but also significantly improve their vibration absorption capacity, greatly improving driving stability and ride comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the spindle-shaped unit cell in the present invention.

[0020] Figure 2 Schematic diagram of the chiral unit cell in the present invention.

[0021] Figure 3 Schematic diagram of the chiral unit cell of the metamaterial in the present invention.

[0022] Figure 4 Schematic diagram of the negative Poisson's ratio structural unit in the present invention.

[0023] Figure 5 Schematic diagram of the non-pneumatic tire structure of the present invention.

[0024] Figure 6 This is the relationship between axial compression and material Poisson's ratio during the negative Poisson's ratio performance verification process.

[0025] Figure 7 This is the relationship diagram between axial compression and axial pressure during the elastic performance verification process.

[0026] Figure 8 This is the relationship between axial compression and axial pressure during the shape memory performance verification process. Detailed implementation mode

[0027] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Embodiment

[0029] A non-inflatable tire structure based on SMA is composed of a plurality of negative Poisson's ratio structural units arranged according to a preset rule; the negative Poisson's ratio structural unit is formed by connecting the tops of four spindle-shaped unit cells and one chiral unit cell respectively to form a metamaterial chiral unit cell ( Figure 3 ), and then obtained by symmetry through a mirror plane passing through the short axis of the spindle-shaped unit cell and perpendicular to the plane where the long and short axes are located ( Figure 4 ), wherein the spindle-shaped unit cell is a three-dimensional spindle-shaped unit cell obtained by performing a circular array of a planar spindle-shaped unit cell along the long axis ( Figure 1 ), the chiral unit cell is composed of four ligaments, the central axis of the ligament is perpendicular to the outer side, a rectangle is constructed in the middle, and adjacent ligaments are in contact with each other in pairs ( Figure 2 ).

[0030] The overall structure adopts NITI shape memory alloy material and is integrally formed by means of additive manufacturing technology, which ensures the stability of the structure and the uniformity of the material.

[0031] The negative Poisson's ratio structural unit is bent by 22.5° and then undergoes a circular array around the bending center to form a non-inflatable tire structure ( Figure 5 ).

[0032] The long axis of the spindle-shaped unit cell is a1, the short axis is b1, the radian of the curved ligament is θ1, a three-dimensional spindle-shaped unit cell is obtained by performing a circular array of a planar spindle-shaped unit cell along the long axis, the side length of the chiral unit cell is a2, the side length of the rectangle constructed in the middle is a3 (<a2), the central axis of the ligament is perpendicular to the outer side, a rectangle is constructed in the middle, and adjacent ligaments are in contact with each other in pairs. The thickness of the ligament is t1.

[0033] The numerical simulation software Abaqus is used to verify the negative Poisson's ratio performance of the negative Poisson's ratio structural unit. The unit used is a solid entity unit, the three-dimensional entity mesh type is C3D10 unit, and the global seed size is 0.3mm. Using the performance parameters of NiTi alloy materials, the negative Poisson's ratio structural unit is placed between two rigid plates coupled to corresponding reference points. The bottom plate fixes six degrees of freedom, and the top plate applies a displacement constraint corresponding to the downward material height direction. Symmetric boundary conditions are added to the surface perpendicular to the rigid plate. The longitudinal and transverse strains of the negative Poisson's ratio structural unit are extracted respectively, and the results are as follows. Figure 6 shown.

[0034] Numerical simulation software was used to verify the pseudo-elastic performance of the negative Poisson's ratio structural unit. The unit used is a solid entity unit, and the three-dimensional entity mesh type is C3D10: a ten-node quadratic tetrahedron unit with a global seed size of 0.3mm. Using the performance parameters of NiTi alloy materials, the negative Poisson's ratio structural unit is placed between two rigid plates coupled to corresponding reference points. The bottom plate is fixed with six degrees of freedom, and symmetric boundary conditions are added to the surface perpendicular to the rigid plate. Among them, NiTi alloy will produce a phase transformation between the austenite phase and the martensite phase when subjected to external force or temperature changes, and different phases have different physical properties. The Young's modulus of austenite is 60Gpa, the Poisson's ratio is 0.33, and the thermal expansion coefficient is 2.2e -6 ℃ -1 The phase transition starting temperature is 32°C and the ending temperature is 78°C. The Young's modulus of martensite is 45GPa, the Poisson's ratio is 0.33, and the thermal expansion coefficient is 2.2e -6 ℃ -1 The phase transformation starting temperature is 45℃ and the ending temperature is -7℃. Set the temperature above the austenite transformation ending temperature and apply displacement load to the material again. After the material passes through the initial elastic stage, the stress induces the austenite phase to begin to transform into the martensite phase. At this time, after unloading, the martensite returns to the austenite state and elastic deformation recovery is achieved. The force and displacement curve is shown as follows: Figure 7 shown.

[0035] Numerical simulation software was used to verify the shape memory performance of the negative Poisson's ratio structural unit. The unit used is a solid entity unit, and the three-dimensional entity mesh type is C3D10: a ten-node quadratic tetrahedron unit with a global seed size of 0.3mm. Using the performance parameters of NiTi alloy materials, the negative Poisson's ratio structural unit is placed between two rigid plates coupled to corresponding reference points. The bottom plate is fixed with six degrees of freedom, and symmetric boundary conditions are added to the surface perpendicular to the rigid plate. Among them, NiTi alloy will produce a phase transformation between the austenite phase and the martensite phase when subjected to external force or temperature changes, and different phases have different physical properties. The Young's modulus of austenite is 60Gpa, the Poisson's ratio is 0.33, and the thermal expansion coefficient is 2.2e-6 ℃ -1 The phase transition starting temperature is 32°C and the ending temperature is 78°C. The Young's modulus of martensite is 45GPa, the Poisson's ratio is 0.33, and the thermal expansion coefficient is 2.2e -6 ℃ -1 The phase transformation starting temperature is 45℃ and the ending temperature is -7℃. The initial temperature is set between the austenite transformation starting temperature and the martensite transformation starting temperature, and the displacement load is applied to the material again. After the material passes through the initial elastic stage, the stress induces the austenite phase to begin to transform into the martensite phase. After unloading, the elastic deformation recovers and a small amount of plastic deformation occurs. After that, the temperature is raised to above the austenite transformation ending temperature, and the plastic deformation is completely recovered. Its force and displacement curve is as follows: Figure 8 shown.

[0036] The above description is only for better explanation of the embodiments of the present invention and is not intended to limit the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are intended to be within the scope of the present invention.

Claims

1. A non-pneumatic tire structure based on SMA, characterized in that: It is composed of multiple negative Poisson's ratio structural units arranged according to preset rules; the negative Poisson's ratio structural unit is formed by four spindle-shaped unit cells connected to the top of a chiral unit cell to form a metamaterial chiral unit cell, and then symmetrically obtained through a mirror plane of the short axis of the spindle-shaped unit cell and perpendicular to the plane where the long and short axes are located; wherein, the spindle-shaped unit cell is a three-dimensional spindle-shaped unit cell obtained by making a circular array through the long axis of a planar spindle-shaped unit cell, and the chiral unit cell is composed of four ligaments, the central axis of the ligament is perpendicular to the outer edge, and a rectangle is constructed through the middle, and adjacent ligaments are in contact with each other.

2. The non-pneumatic tire structure based on SMA according to claim 1, characterized in that: After being bent and deformed by 22.5°, the negative Poisson's ratio structural units are arranged in a circular array with the bending center as the axis to form a non-pneumatic tire structure.

3. The non-pneumatic tire structure based on SMA according to claim 1, characterized in that: Made of NITI shape memory alloy material.

4. The non-pneumatic tire structure based on SMA according to claim 3, characterized in that: The Young's modulus of austenite is 60GPa, and the Young's modulus of martensite is 45GPa.

5. The non-pneumatic tire structure based on SMA according to claim 3, characterized in that: The Poisson's ratio of austenite is 0.33, and the Poisson's ratio of martensite is 0.

33.

6. The non-pneumatic tire structure based on SMA according to claim 3, characterized in that: The thermal expansion coefficient of austenite is 2.2e -6 ℃ -1 , the thermal expansion coefficient of martensite is 2.2e -6 ℃ -1 .

7. The non-pneumatic tire structure based on SMA according to claim 3, characterized in that: The austenite transformation starts at 32°C and ends at 78°C.

8. The non-pneumatic tire structure based on SMA according to claim 3, characterized in that: The martensitic transformation starts at 45°C and ends at -7°C.

Images