【作者】 韩宇；

【导师】 张锐；

【作者基本信息】 吉林大学 ， 仿生科学与工程， 2023， 硕士

【摘要】 我国国土辽阔,气象条件非常复杂,冰冻地区占据我国国土面积的比例高达75%,初春和冬季时节道路冰雪会严重影响交通安全。而不同于其它介质,冰雪在发生摩擦时,由于产生热量,表面会出现液膜,起到润滑作用,使得其具有较小的摩擦系数。而轮胎作为轮式车辆与地面直接接触的唯一部件,传递着地面对车辆所有的作用力,其表面结构可以直接影响汽车的操控稳定性、驾驶舒适性以及通过性。相较于常规的冬季路面环境,结冰且覆雪路面具有更复杂的力学特性,从而导致轮胎在结冰覆雪路面行驶时更容易产生巨大的滑移和下沉量。因此,本文以在冰雪上具有优秀运动能力的驯鹿和能够稳定攀附在固液表面的海马为仿生原型,将二者的生物学特征与轮面花纹相结合,并对设计的轮胎进行加工、试验测试以及仿真分析,以寻求攻克车辆在冰雪路面上的通过性问题,为轮胎表面花纹的仿生设计提供依据。对驯鹿足蹄进行形貌结构测量,并分析在其运动过程中足蹄的各部位功能。蹄壳和肉蹄均起到了支撑作用,同时硬度较大的蹄壳还具有切入冰雪层增大摩擦的功能,硬度较小的肉蹄具有较好的固雪功能。结合轮胎花纹的类型和课题组之前的研究,对仿生花纹进行优化和加工。探究冰雪的物理性质、力学特性和橡胶的摩擦理论,并根据密度将试验用雪分为松散雪和密实雪。通过UTM摩擦试验机分别在松散雪和密实雪下,考虑雪层厚度、施加压力和运行速度三种试验因素,对不同排列方式的橡胶块进行摩擦性能力学试验。试验结果表明,在密度为0.24 g/cm~3的松散雪下,夹角为77.57°排列方式的橡胶块B的动摩擦系数最大,是橡胶块A(夹角为85.75°)的1.06-1.22倍,是橡胶块C(夹角为59.24°)的1.19-1.46倍。在松散雪下,橡胶块B在60 N的载荷、雪层厚度为20 mm、速度为360 mm/min下的动摩擦系数最大为0.453。在密度为0.48 g/cm~3的密实雪下,依旧是夹角为59.24°排列方式的橡胶块B的动摩擦系数最大,是橡胶块A的1.04-1.16倍,是橡胶块C的1.10-1.39倍。在密实雪下,橡胶块B在60 N的载荷、雪层厚度为10 mm、速度为240mm/min下的动摩擦系数最大为0.364。当试验因素为同一水平时,松散雪下的动摩擦系数略高于密实雪。测量海马尾部的几何尺寸,对海马尾部进行大体解剖,通过扫描电镜对其结构进行观察分析,发现海马尾部具有39-41个节骨环,每个节骨环均由4个菱形骨片构成。根据节骨环在攀附过程中起到的作用,将其分为四类,分别为:骨片的凸起部位(棘凸)、骨片与骨片之间的重合部位、节骨环上骨片延伸到相邻节骨环上骨片的延伸结构和骨片的骨棱。在海马攀附在固液表面时,骨片的凸起部位与固体直接接触,具有增大摩擦的作用;重合部位类似于转动副,给予海马尾巴更高的自由度和更大的灵活性;另外两个结构起到支撑的作用。采用工程仿生思想,将海马骨片的凸起部位与轮胎花纹相结合,考虑到轮胎的变形不会超出Mooney Rivlin本构模型的使用范围,选用Mooney Rivlin作为橡胶的本构模型,利用Abaqus有限元软件,对仿生轮胎进行承压仿真分析,验证了仿生花纹不会对轮胎的承载性能产生影响。考虑到加工的难易程度,对仿生轮胎进行简化,利用3D打印技术将其加工出来,通过车轮力学测试台对轮胎进行滑转率测试试验。在松散雪和密实雪下,对两种仿生轮胎和对比轮胎在雪层厚度、载荷和速度三个试验因素下进行测试。试验结果表明,具有驯鹿和海马因素的仿生轮胎C滑转率最低,其次是只具有海马因素的仿生轮B,而对比轮A的滑转率最大,在松散雪下,是轮胎B的1.07-1.43倍,是轮胎C的1.42-1.67倍;在密实雪下,是轮胎B的1.24-1.5倍,是轮胎C的1.25-1.54倍,同时还发现雪的密度增大,会加剧车轮的滑转。车辆在松软路面行驶时,对雪粒的破坏力、扬雪量能反映出轮胎的力学性能,但由于试验条件有限,难以对雪的变化量进行分析。因此,借助EDEM离散元软件,从雪颗粒的角度出发,分析在同样的滑转率下,三种轮胎在相同厚度的雪层上行驶,对雪层的破坏。仿真结果表明,仿生轮的扬雪量最小,对雪层破坏程度最小,牵引性能最好。此外,还做了仿生轮分别在10 mm、15 mm和20 mm厚度下的仿真分析,仿真结果表明,雪层厚度增加,会加大扬雪量,降低轮胎的通过性能。车辆在冰雪路面上行驶时,除了载荷、速度和雪层厚度三种因素外,坡度对车辆的通过性也有重要的影响,但由于试验条件限制,无法控制冰雪面呈规则的坡度。因此,借助于ADAMS多体动力学软件,分析了装配三种车轮的车体在坡度为2°的冰雪路面上的滑转率、速度和地面的相互作用力。仿真发现装配有双仿生因素车轮A的车体A通过性最好,其次是装配有单仿生因素车轮C的车体C,最次为装配有对比轮的车体B。仿真结果表明,同样的车轮转速、运动时间下,车体A的位移是车体B的1.46倍,是车体C的1.01倍。更多还原

【Abstract】 China’s vast territory,meteorological conditions are very complex,frozen areas occupy up to 75%of China’s land area,early spring and winter season road snow and ice will seriously affect traffic safety.And unlike other media,snow and ice in the occurrence of friction,due to the heat generated,the surface will appear liquid film,play a lubricating effect,making it has a smaller coefficient of friction.The tires,as the only part of the wheeled vehicle in direct contact with the ground,transmit all the ground forces on the vehicle,and their surface structure can directly affect the handling stability,driving comfort and passability of the vehicle.Compared with the conventional winter road environment,icy and snow-covered roads have more complex mechanical characteristics,which makes tires more likely to produce huge amounts of slip and sink when driving on icy and snow-covered roads.Therefore,this paper takes reindeer,which has excellent athletic ability on snow and ice,and seahorse,which can climb steadily on solid-liquid surfaces,as bionic prototypes,combines their biological characteristics with wheel tread patterns,and processes,tests and simulates the designed tires in order to seek to overcome the problem of vehicle passability on snow and ice,and to provide a basis for the bionic design of tire surface patterns.The morphological and structural measurements of reindeer hooves were conducted and the functions of each part of the hooves during their movement were analyzed.Both the hoof shell and the fleshy hoof play a supporting role,while the harder hoof shell also has the function of cutting into the ice and snow layer to increase friction,and the less hard fleshy hoof has a better function of snow fixation.Combining the type of tire tread pattern and the previous research of the group,the bionic tread pattern is optimized and processed.The physical properties of snow and ice,mechanical properties and friction theory of rubber were investigated,and the snow for the test was divided into loose snow and dense snow according to the density.The mechanical tests on the friction properties of rubber blocks with different arrangements were conducted by UTM friction testing machine under separate loose snow and dense snow,considering three test factors of snow thickness,applied pressure and running speed.The test results show that under the loose snow with density of 0.24 g/cm~3,the dynamic friction coefficient of rubber block B with 77.57°angle arrangement is the largest,which is 1.06-1.22 times that of rubber block A(85.75°angle)and 1.19-1.46 times that of rubber block C(59.24°angle).Under loose snow,the coefficient of dynamic friction of rubber block B is 0.453 at a load of 60 N,a snow thickness of 20 mm,and a speed of 360 mm/min.Under dense snow with a density of 0.48 g/cm~3,the coefficient of dynamic friction of rubber block B,which is still arranged at an angle of 59.24°,is 1.04-1.16 times higher than that of rubber block A and 1.10-1.39 times higher than that of rubber block C.1.10-1.39 times higher than that of rubber block C.Under dense snow,the maximum coefficient of kinetic friction of rubber block B was 0.364 at a load of 60 N,a snow thickness of 10mm,and a speed of 240 mm/min.When the test factors were at the same level,the coefficient of kinetic friction under loose snow was slightly higher than that under dense snow.The geometry of the seahorse tail was measured,the seahorse tail was grossly dissected,and its structure was observed and analyzed by sweeping electron microscopy,and it was found that the seahorse tail had 39-41 articular rings,each of which was composed of four diamond-shaped bone fragments.The rings were classified into four categories according to the role they played in the climbing process:the projection of the bony lamellae(spiny convexity),the overlap between the bony lamellae and the bony lamellae,the extension of the bony lamellae on the bony ring to the bony lamellae on the adjacent bony ring,and the bony ribs of the bony lamellae.When the seahorse climbs on the solid-liquid surface,the projection of the bone piece is in direct contact with the solid,which has the effect of increasing friction;the overlapping part is similar to the rotating part,which gives the seahorse tail higher freedom and greater flexibility;the other two structures play the role of support.The engineering bionic idea is adopted to combine the raised part of the seahorse bone piece with the tire tread pattern,and considering that the deformation of the tire will not exceed the range of the Mooney Rivlin intrinsic model,Mooney Rivlin is chosen as the intrinsic model of rubber,and the Abaqus finite element software is used to simulate the pressure-bearing analysis of the bionic tire,which verifies that the bionic tread pattern will not affect the load-bearing performance of the tire.Considering the difficulty of machining,the bionic tires were simplified and machined out using 3D printing technology,and the tires were tested for skid rate test by wheel mechanics test bench.The two bionic tires and the comparison tire were tested under loose snow and dense snow with three test factors:snow thickness,load and speed.The test results showed that bionic tire C with reindeer and seahorse factors had the lowest slip rate,followed by bionic wheel B with only seahorse factors,while comparison wheel A had the largest slip rate,1.07-1.43 times that of tire B and 1.42-1.67 times that of tire C under loose snow;1.24-1.5 times that of tire B and 1.25-1.54times that of tire C under dense snow,it was also found that the increased density of snow increases wheel slip.The damage force to snow particles and the amount of snow lift when the vehicle is driven on a soft road surface can reflect the mechanical properties of the tire,but the limited test conditions make it difficult to analyze the amount of snow variation.Therefore,with the help of EDEM discrete element software,the damage to the snow layer is analyzed from the perspective of snow particles when three kinds of tires are driven on the same thickness of snow layer under the same slip rotation rate.The simulation results show that the bionic wheel raises the least amount of snow,damages the snow layer the least and has the best traction performance.In addition,the simulation analysis of the bionic wheel was also done at 10 mm,15 mm and 20 mm thicknesses respectively,and the simulation results showed that the increase of snow layer thickness would increase the snow lifting and reduce the passing performance of the tire.When the vehicle is driven on the ice and snow road,besides the three factors of load,speed and snow thickness,the slope also has an important influence on the vehicle passability,but due to the limitation of the test conditions,it is impossible to control the ice and snow surface in a regular slope.Therefore,with the help of ADAMS multi-body dynamics software,the slip rate,velocity and ground interaction force of the vehicle body assembled with three kinds of wheels on the ice and snow surface with a slope of2°were analyzed.The simulation found that the vehicle body A with dual bionic factor wheel A had the best passability,followed by vehicle body C with single bionic factor wheel C,and the next best was vehicle body B with contrast wheels.simulation results showed that the displacement of vehicle body A was 1.46 times that of vehicle body B and 1.01 times that of vehicle body C for the same wheel speed and motion time.更多还原