冲击机械应力波传递效率研究及在月壤采样机构上的应用

发布时间：2018-04-16 00:12

本文选题：冲击 + 应力波　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：冲击机械由于利用撞击而能产生强度极大的力流,与相同功率下的静压机械相比,其结构更为紧凑,在工业生产中有着广泛的应用并有着相似的动作原理:即冲锤部件在重力、液压、或蒸汽等力的作用下加速运动,并以一定的速度撞击工作对象,使得工作对象发生位移、变形和破坏。传统机械动力学分析将机械零部件作为刚体或质点,忽略了介质微单元体的惯性。波动力学理论考虑了以毫秒甚至纳秒计短暂时间尺度上发生的运动参量显著变化,是冲击机械系统能量传递过程分析所必须依赖的力学基础。受空间环境下月壤采样机构能源供给的限制,本文立足于一般化的冲击机械模型,在假定岩土动态加载刚度一定的条件下分析比较了不同入射波形对岩土介质作功过程中能量传递效率情况;以实现最优指数应力波形为目标,基于一维波动力学理论并使用?函数法对冲锤部件的波阻抗进行反演设计;使用正解计算和有限元仿真的方法验证反演设计的正确性;首次提出假设脱离法,基于线性叠加原理,分析了冲锤与击杆间的受力及运动状态,分析了冲锤几何外形无量纲参数影响下能量传递效率和冲锤冲击效率的变化规律并计算相关的最优参数。入射波在变波阻抗或是变截面杆形部件传播过程中必然会有反射波的产生。本文以应力波在变波阻抗杆形部件的透反射规律为研究对象,利用频域分析法及有限元程序,在击杆两端波阻抗比值给定且一端受到冲击载荷的情况下对不同波阻抗方案的能量透射效率给予分析与比较;使用泛函极值问题的变分法,兼顾能量透射效率,求解得到反对称波阻抗条件下使击杆部件具有质量最小的平原式几何方案;比较分析了该方案相对于其他方案的优势,有利于实际工程应用。将提高系统工作效率的相关措施应用在以空心为几何特征的月壤采样机构设计中。结合有限元仿真程序,对比优化设计前后的仿真结果,验证了文中理论研究所得到的优化设计方案可有效提高系统的工作效率。
[Abstract]:The impact machine can produce a strong force flow by using the impact. Compared with the static pressure machine with the same power, its structure is more compact, and it is widely used in industrial production and has similar action principle: namely, the impact hammer parts are in gravity.Under the action of hydraulic pressure or steam equal force accelerates motion and impinges the working object at a certain speed which causes displacement deformation and destruction of the working object.In the traditional mechanical dynamic analysis, the mechanical parts are regarded as rigid body or particle, and the inertia of dielectric microelement is ignored.The theory of wave mechanics takes into account the significant changes of motion parameters in millisecond or even nanosecond time-scales, which is the mechanical basis on which the analysis of energy transfer process of impact mechanical system depends.Limited by the energy supply of lunar soil sampling mechanism in the space environment, this paper is based on the general impact mechanical model.Under the assumption that the dynamic loading stiffness of rock and soil is constant, the energy transfer efficiency of different incident waveforms in the process of doing work on geotechnical medium is analyzed and compared, with the goal of realizing the optimal exponential stress waveform, based on the theory of one-dimensional wave mechanics and using?The function method is used to counter the wave impedance of hammer components for inversion design; the forward solution calculation and finite element simulation are used to verify the correctness of the inversion design; the hypothesis separation method is proposed for the first time, which is based on the principle of linear superposition.The force and motion state between impact hammer and hammer are analyzed. The energy transfer efficiency and impact efficiency of impact hammer under the influence of dimensionless parameters of impact hammer geometry are analyzed and the optimal parameters are calculated.The incident wave is bound to produce reflected waves during the propagation of variable impedance or rod-shaped parts with variable cross-section.In this paper, we take the law of the stress wave reflected in the variable wave impedance bar as the research object, and use the frequency domain analysis method and the finite element program.The energy transmission efficiency of different wave impedance schemes is analyzed and compared under the condition that the ratio of wave impedance at both ends of the rod is given and one end is subjected to impact load, and the energy transmission efficiency is taken into account by using the variational method of functional extremum problem.The plain geometry scheme with minimum mass of the hammer member is obtained under the condition of antisymmetric wave impedance, and the advantages of the scheme compared with other schemes are compared and analyzed, which is beneficial to practical engineering application.The related measures to improve the working efficiency of the system are applied to the design of the lunar soil sampling mechanism with hollow geometry.Combining with the finite element simulation program, the simulation results before and after the optimization design are compared, and it is verified that the optimal design scheme obtained in this paper can effectively improve the working efficiency of the system.
【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】：2015
【分类号】：P184.5

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