基于离散元理论的月尘颗粒接触力学特性研究

发布时间：2018-03-03 06:30

本文选题：月尘颗粒　切入点：力学特性　出处：《哈尔滨工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：月尘是月球表面附着的粉末状物质,由于具有较强的黏附性和静电特性,月尘容易在月球探测器各装置的表面上沉积,并有可能进入机构间隙,造成设备堵塞、机构卡死等问题。目前常用的颗粒接触力学本构模型将颗粒简化为光滑、均质的球形颗粒,不能对不规则月尘颗粒的接触特性进行合理描述,无法反应月尘颗粒进入机构间隙后的真实作用情况。基于以上问题,本文结合月尘性质对现有接触力学模型进行改进,提出基于形状描述的月尘颗粒接触力学模型,并利用该模型进行月尘颗粒对运动副运动特性的影响研究。结合月尘性质对现有接触力学模型局限性进行分析和改进,将不规则形状引入力学模型中,对月尘颗粒进行基于分形理论的形状建模和基于傅里叶理论的形状建模,同时对两种建模方法进行比较和选用,最终得到月尘颗粒形状描述数学模型。此外,进行模拟月尘样品颗粒图像采集,对得到的颗粒二维投影轮廓图像进行后处理和分布统计,得到模拟月尘颗粒形状分布概率模型。在月尘颗粒形状描述数学模型基础上建立基于形状描述的不规则月尘颗粒接触力学模型,并通过月尘颗粒法向力学特性测试试验对其加以验证。利用基于形状描述的不规则颗粒接触力学模型对不规则颗粒进行球颗粒等效,提出基于分段函数拟合的等效算法,并通过离散元软件二次开发平台编写力学模型插件,验证算法可靠性。采用不规则颗粒等效模型并按照模拟月尘颗粒形状分布概率生成大量颗粒,进行月尘颗粒对运动副运动特性影响的离散元仿真,通过仿真过程中转矩变化判断是否出现卡死现象,同时对比轮轴掩埋试验结果,分析仿真结果正确性。最终通过离散元仿真实现偏心距、转速以及配合表面性质等因素对转矩影响的仿真预测,结合仿真结果对未来月面探测器的设计提出理论性建议。
[Abstract]:Lunar dust is a powdered material attached to the surface of the moon. Because of its strong adhesion and electrostatic properties, lunar dust is easy to deposit on the surface of the lunar probe devices, and may enter the mechanism gap, resulting in equipment blockage. The current constitutive model of particle contact mechanics simplifies particles to smooth, homogeneous spherical particles, which can not reasonably describe the contact characteristics of irregular lunar dust particles. Based on the above problems, this paper improves the existing contact mechanics model based on the character of lunar dust, and puts forward the contact mechanics model of lunar dust particles based on shape description. The influence of lunar dust particles on the motion characteristics of motion pair is studied by using this model. The limitation of the existing contact mechanics model is analyzed and improved by combining the characteristics of lunar dust, and the irregular shape is introduced into the mechanical model. The shape modeling of lunar dust particles based on fractal theory and the shape modeling based on Fourier theory is carried out. At the same time, the two modeling methods are compared and selected. Finally, the mathematical model of the shape description of lunar dust particles is obtained. The particle images of the simulated lunar dust samples were collected, and the two dimensional projection contour images of the particles were processed and distributed statistically. The probability model of simulating the shape distribution of lunar dust particles is obtained. Based on the mathematical model of the shape description of lunar dust particles, the contact mechanics model of irregular lunar dust particles based on shape description is established. It is verified by the test of normal mechanical properties of lunar dust particles. The spherical particles are equivalent to irregular particles based on shape description, and an equivalent algorithm based on piecewise function fitting is proposed. The reliability of the algorithm is verified by compiling the mechanical model plug-in on the second development platform of discrete element software. The irregular particle equivalent model is adopted and a large number of particles are generated according to the probability of simulating the distribution of lunar dust particles. The discrete element simulation of the influence of lunar dust particles on the motion characteristics of the motion pair is carried out. The torque changes in the simulation process are used to judge whether the phenomenon of entrapment occurs or not, and the results of the wheel shaft burying test are compared at the same time. Finally, the influence of eccentricity, rotational speed and matching surface properties on torque is predicted by discrete element simulation, and some theoretical suggestions for the design of lunar detector in the future are put forward based on the simulation results.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V476.3

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