WO2021120624A1

WO2021120624A1 - Mars tire having shape-memory alloy lattice structure

Info

Publication number: WO2021120624A1
Application number: PCT/CN2020/104143
Authority: WO
Inventors: 张冬云; 陈润平; 李泠杉; 胡松涛
Original assignee: 北京工业大学
Priority date: 2019-12-20
Filing date: 2020-07-24
Publication date: 2021-06-24
Also published as: CN111003212A

Abstract

A Mars tire having a shape-memory alloy lattice structure, relating to the field of parts of space rovers. An effective part of the tire is a tire body, designed mainly for complex road surfaces on Mars that are likely to damage a tire. The tire body utilizes a lattice structure, allowing reduced weight while ensuring that the tire can bear a load. The lattice structure has damping and energy absorption capabilities, and ensures that the tire is stable over the course of the service life. Tire lugs are provided on a surface of the tire, used to increase the grip of the tire, thereby ensuring that a Mars rover passes over soft road surfaces. The hyperelasticity of NiTi alloy ensures that the tire, after being subjected to impacts from rocks, can still revert back to the original shape thereof . The tire is integrally formed by means of selective laser melting (SLM), thereby solving the problem where machining a lattice structure is difficult. In addition, a corresponding heat treatment process is adopted to control mechanical properties of the tire.

Description

A Martian tire with a lattice structure of shape memory alloy

Technical field

The invention relates to the technical field of parts and components of an aerospace exploration vehicle.

Background technique

A tire is a circular component that is installed on a vehicle or mechanical equipment, directly contacts the ground, and realizes the movement of the carrying object by rolling. The main functions of the tires are: to support the car body or mechanical equipment; to reduce the impact force generated when in contact with the road; to adhere to the ground to ensure the traction, braking and passing of the vehicle.

With the development of aerospace technology, the demand for outer space planetary exploration is gradually increasing. In order to meet the needs of fire planetary exploration, it is necessary to consider the complex climate and geographical environment of the fire planet to design the tire carcass of the Mars rover. Martian roads are dominated by bare rock and sandy roads. The temperature is between -46°C and 35°C. Rubber tires are not enough to serve the road environment and climatic conditions. Therefore, aerospace exploration vehicles of various countries mainly use metal tires. After investigating the structure of the tires of Valor and Curiosity that have been explored on Mars, and analyzing their tire failure mechanism, it was found that the main reasons for the damage to the wheels of the Mars rover were: sharp rocks pierced the tire surface; Metal tires are subject to impact and permanent deformation pits; wear and tear caused by long-term operation. The above problems have resulted in shorter service time of the Mars rover, poor road trafficability and operational stability, thus affecting the detection of the Martian surface.

Summary of the invention

The technical problem to be solved by the present invention is how to provide a new type of Martian tire that can solve the problems of puncture, pits and wear encountered by the Martian wheel.

In order to solve the above technical problems, the technical solution adopted by the present invention is to use additive manufacturing technology to integrally manufacture a metal Martian tire with an alloy lattice structure. The tire design is only the carcass part, and the carcass has a lattice structure. The characteristic is that the lattice structure can be filled with lattices of different parameters according to the actual load-bearing requirements and deformation resistance of the car body. The whole tire is integrated Forming, the lattice and the inner surface of the tire do not need to be mechanically connected, and the surface of the tire in contact with the ground has wheel spurs.

The lattice structure used for tire carcass filling is based on additive manufacturing. Additive manufacturing technology makes complex geometric processing easier than before, so the design limitations are lifted to a certain extent. The selection of the tire carcass filling structure can be topologically optimized according to the tire force. Due to the force on the tire surface It is periodic, so the carcass filling structure should theoretically have the consistency of radial mechanical properties.

The limitation of purely using topology optimization to optimize the carcass filling structure is that it may result in a small angle between part of the structure and the processing plane, so additional support is required, which increases manufacturing difficulty and manufacturing costs. Since the lattice structure is obtained from a single cell array, the processing consistency is good. At the same time, the lattice structure has the characteristics of energy absorption and light weight, which are highly consistent with the required attributes of the Mars rover tire. Therefore, the lattice is filled in the tire carcass .

A tire carcass with a metal lattice structure is characterized in that it comprises:

The interior of the tire carcass is filled with a lattice structure. The lattice structure is obtained from a single cell array. The lattice is covered by the outer skin of the tire. The tire tread has spurs that increase the grip.

Furthermore, the metal lattice structure tire carcass is integrally formed by additive manufacturing technology.

Further, the material is a shape memory alloy.

Furthermore, there are two rows of spurs for increasing the grip, one spur every 5°, for a total of 72 spurs.

Furthermore, two adjacent wheel spines are misaligned in the tire axial direction, and the dislocation angle is 9°, and the wheel spines are staggered over the tire surface.

Furthermore, after the metal additive manufacturing process, heat treatment is required to reduce the residual stress of the tire.

Furthermore, the cell of the lattice structure is formed by four cylindrical rods intersecting at one point to form a cell, and the same cell is used to fill the space between the tire tread and the rim, and finally a tire with the lattice structure is obtained.

Furthermore, the cells that make up the lattice can adjust the density and mechanical properties of the lattice by adjusting the rod diameter ratio, that is, the ratio of the length of the cell rod to the radius of the rod.

Further, the included angle between the rod of the cell and the processing plane should not be less than 45°, and the diameter of the rod of the cell should not be less than 2mm.

A further technical solution is that the matrix structure of the carcass has 2 cells in the radial direction and 4 cells in the axial direction. The carcass part is selected by the software Creo5.0, and the parameters of a single cell are determined and then arrayed.

The further technical solution is that the cell is in a body-centered cubic configuration, specifically four round rods of the same length meet at a point in the center. The theoretical basis is the atomic close packing theory, which is deduced by Bravais A. through mathematical methods. It is concluded that the geometric structure of the body-centered cubic cell can be regarded as the geometric structure formed by the diagonal of a cube, so the side length of the cube constituting the cell is the cell size parameter.

The reason for choosing the body-centered cubic lattice is that the sandwich structure of the body-centered cubic lattice is anisotropic, and the deformation spreads uniformly in the body structure and is concentrated at the nodes, so it has the characteristics of uniform deformation; the superelasticity of NiTi alloy determines that it has 8 Deformation recovery ability of about ％; body-centered cubic lattice has large Young's modulus, shear modulus and elastic anisotropy, so energy absorption capacity is better; the two superimposed new tires have better energy absorption and deformation Recovery ability; and the stiffness of the tire (similar to the need for proper tire pressure) can be adjusted by changing the thickness of the beam in the lattice structure. Energy absorption capacity and rigidity are contradictory to each other, which is a bottleneck to traditional design and manufacturing. However, this tire achieves a balance between the two through performance customization.

A further technical solution lies in the superelasticity of the shape memory alloy, that is, after the deformation exceeds the elastic deformation limit, it can still return to its original shape within a certain range for a period of time. Therefore, the tire can be self-repaired when the tire is greatly deformed by the impact, so as to solve the problem of pits on the surface of the tire after the impact, which affects the smooth running of the rover.

The further technical solution lies in the high strength and super elasticity of NiTi alloy, combined with the advantages of energy absorption and vibration reduction of the lattice structure, and the combination of material advantages and structural advantages to further enhance the energy absorption and vibration reduction capabilities of the tire.

Description of the drawings

The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

1 is a schematic cross-sectional view of the structure of the metal Martian tire with the NiTi alloy lattice structure according to the present invention;

2 is a schematic diagram of the lattice cell of the metal Martian tire with the NiTi alloy lattice structure according to the present invention;

Among them: 10, dot matrix 20, round puncture 11, cell

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

In the following description, many specific details are explained in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described here, and those skilled in the art can do so without departing from the connotation of the present invention. Similar promotion, therefore, the present invention is not limited by the specific embodiments disclosed below.

As shown in FIG. 1, the embodiment of the present invention discloses a metal Martian tire with a NiTi alloy lattice structure, which includes a lattice 10 and tire surface spurs 20, and the entire tire carcass is integrally formed by SLM metal 3D printing. The present invention is different from the prior art in that the existing metal elastic tires mostly use solid or energy-absorbing and vibration-absorbing structures based on traditional processing technology to fill the tire carcass, and the material used is a softer and non-wearable aluminum alloy. The new metal tire proposed in this design is filled with a lattice structure to reduce the tire weight while ensuring tire elasticity. The energy absorption and vibration damping capacity of the lattice 10 structure is used to improve the running stability of the tire. NiTi shape memory alloy is used as the metal tire material. , It has better strength and wear resistance than the existing aluminum alloy tires. At the same time, the additive manufacturing technology ensures the feasibility of lattice structure processing.

Further, as shown in Fig. 1, referring to the tire size of the existing Mars rover (the Curiosity wheel diameter is 510mm), the tire has an outer diameter of 500mm, an inner diameter of 300mm, a wheel width of 200mm, and a tread thickness of 5mm (excluding the spur 11). thickness).

Further, as shown in FIG. 2, the cell 11 of the lattice 10 structure is composed of 4 cylindrical rods intersecting at one point to form a cell (which can be regarded as a cube consisting of 4 diagonal lines). The side length and rod diameter can be created and modified by Creo5.0.

Further, as shown in Figure 2, the lattice 10 structure cell 11 parameters are a cube with a side length of 50mm and a rod diameter of 10mm. Create a single cell in the software Creo5.0, and select the inner surface of the tire skin And the outer surface of the rim, then add the cells that have been created, select the array filling, and finally get the dot matrix filling part of the tire.

It should be noted that the cell size of the tire can be adjusted according to the load-bearing conditions of the specific tire. If the tire is required to have greater rigidity, the cell side length can be shortened and the cell rod diameter can be thickened; if the tire is required to have Better elasticity, can make the side length of the cell longer and the diameter of the cell rod thin; also can shorten the side length of the cell and the rod diameter of the cell becomes thinner, or the side length of the cell becomes longer and the rod diameter of the cell The purpose of thickening is to change the bearing capacity and elasticity of the tire. This function can be debugged by Creo5.0 software, so the dot matrix size here is not limited to the set of parameters of side length 50mm and cell rod diameter 10mm.

Further, as shown in Figure 1, the tire surface has spurs 20 every 5° angle, and the spurs 20 are staggered along the axial direction. The spurs are rectangular parallelepiped, with a length of 100mm, a width of 8mm, and a height of 5mm. The chamfering treatment has a fillet radius of 3mm and a total of 72. The purpose is to ensure that the rover has sufficient grip while running smoothly.

Further, as shown in Figure 1, the lattice 10 structure is processed by SLM additive manufacturing technology, and the rod diameter of its cell 11 should not be less than 2mm. 2mm is the processing limit of conventional additive manufacturing equipment. If the rod diameter is less than 2mm , It may cause the rod of the cell to be unable to form, and eventually lead to processing failure.

Further, as shown in Fig. 1, the tires are modeled by software Creo5.0, saved in STL format, and then imported into professional additive manufacturing slicing software (for example, Materialise Magics) for slicing, and after triangular slicing Perform slicing. Finally, the slice file is imported into the additive manufacturing equipment to complete the processing and manufacturing.

When the rover is running on a hard road, the NiTi alloy lattice structure provides it with a good energy absorption and vibration reduction effect. The acceleration generated by the tire hitting the hard rock on the road is absorbed by the multi-layer lattice, and the energy transmitted to the rover will be Significantly reduced; after the tire is deformed by an impact, the pits on the tire can be automatically restored after a period of time, so that the operation of the detection wheel remains stable; NiTi alloy (tensile strength>800MPa) itself is compared with the current use of Mars As far as the aluminum alloy (tensile strength <500MPa) of the rover is concerned, it has higher strength and wear resistance, so it will have a very significant advantage in dealing with the high-stress impact load and wear of the tire.

The NiTi alloy lattice structure metal Mars tire is integrally formed with SLM metal 3D printing technology, which reduces the difficulty of manufacturing the lattice structure, makes the lattice and the tread formed at the same time, reduces the processing steps, reduces the manufacturing cost, and the SLM technology itself It can make the mechanical properties of the processed materials far exceed the castings and basically reach the level of forgings, so the processing quality of the tires can be guaranteed.

Claims

A tire carcass with a metal lattice structure is characterized in that it comprises:

The interior of the tire carcass is filled with a lattice structure. The lattice structure is obtained from a single cell array. The lattice is covered by the outer skin of the tire. The tire tread has spurs that increase the grip.
The tire carcass of a metal lattice structure according to claim 1, wherein:

The tire carcass of metal lattice structure is integrally formed by additive manufacturing technology.
The tire carcass of a metal lattice structure according to claim 1, wherein:

The material is shape memory alloy.
The tire carcass of a metal lattice structure according to claim 1, wherein:

There are two rows of spurs to increase the grip, one spur every 5°, for a total of 72 spurs.
The tire carcass of a metal lattice structure according to claim 1, wherein:

Two adjacent wheel spurs are misaligned in the tire axial direction, the dislocation angle is 9°, and the wheel spurs are staggered to cover the tire surface.
The tire carcass of a metal lattice structure according to claim 1, wherein:

After the metal additive manufacturing process, heat treatment is required to reduce the residual stress of the tire.
A metal lattice structure tire carcass according to claim 1, characterized in that: the cell element of the lattice structure is formed by four cylindrical rods intersecting at one point to form a cell element, and the same cell element is used to fill the tire tire The space between the surface and the rim, and finally a lattice structure of the tire.
A tire carcass with a metal lattice structure as claimed in claim 7, characterized in that:

The cells that make up the lattice adjust the density and mechanical properties of the lattice by adjusting the rod diameter ratio, that is, the ratio of the length of the cell rod to the radius of the rod.
A tire carcass with a metal lattice structure as claimed in claim 7, characterized in that:

The angle between the rod of the cell and the processing plane should not be less than 45°, and the diameter of the rod of the cell should not be less than 2mm.