车用纳米多孔材料液体系统的能量耗散机理研究

发布时间：2018-05-12 04:40

本文选题：防护材料 + 能量耗散　；参考：《清华大学》2015年博士论文

【摘要】：研发新型、智能、高效的能量耗散材料与结构是车辆被动安全领域的重要课题。本文所研究的纳米多孔材料液体系统基于全新的能量耗散形式,将憎水的纳米多孔材料与液体混合,通过液体在外压下渗入纳米孔道的固液作用过程消耗外界机械能,在车辆碰撞等领域具有广泛的应用前景,然而其物理机理及工程应用均尚未得到充分研究。本文对纳米多孔材料液体系统的能量耗散机理进行了系统的实验研究,阐明了水分子在分子尺度孔道内的渗入渗出行为及其影响机制,并研究了以纳米多孔材料液体系统为填充物的薄壁管件结构的轴向压溃力学特性。基于不同种类的纳米多孔材料,对水分子在外压下渗入分子尺度孔道的行为进行了系统的实验研究。通过采用孔道前处理、电解质调节与多孔径材料进行参数化研究,揭示了固液性质与孔径对渗入压强的影响。在此基础上,借鉴宏观尺度的Young Laplace方程提出等效接触角的概念,并证实了其能够定量描述分子尺度的固液相对作用。利用落锤实验的方法对纳米多孔材料液体系统的动态力学特性进行了研究,验证了渗入机制在动态下的有效性及率相关性。着眼于固液气三者的耦合作用,对水分子在外压撤除时渗出分子尺度孔道的行为进行了系统的实验研究。通过对渗出行为率相关性的观测,揭示了分子尺度孔道内气体分子对水分子渗出行为的影响及其失效机制。通过引入硅醇基团及添加电解质的方法分别对孔道性质及液体性质进行了调节,阐述了其对水分子渗出行为的影响。对应的渗出调节方法可有效提升纳米多孔材料液体系统的可重复使用性及吸能密度。利用实验及有限元模拟的方法,对纳米多孔材料液体系统填充管件的轴向压溃力学特性进行了系统的研究。通过准静态力学实验、落锤冲击实验以及霍普金森压杆冲击实验研究了填充管件在不同应变率下的力学特性,并对其能量吸收机理及失效形式进行了分析。建立了纳米多孔材料液体系统填充管件的有限元模型并进行了实验验证,通过对材料与结构的参数化研究揭示了纳米多孔材料液体系统与管壁的耦合作用机理。基于压溃力效率与吸能密度总结了纳米多孔材料液体系统填充管件的设计规律,为纳米多孔材料液体系统的工程应用及车用新型吸能部件的开发提供了参考。
[Abstract]:The research and development of new, intelligent and efficient energy dissipation materials and structures is an important subject in the field of vehicle passive safety. The liquid system of nano-porous material studied in this paper is based on the new energy dissipation form. The hydrophobic nano-porous material is mixed with liquid, and the external mechanical energy is consumed by the solid-liquid process of permeating into the nano-porous channel under the external pressure of liquid. It has a wide application prospect in the field of vehicle collision, but its physical mechanism and engineering application have not been fully studied. In this paper, the mechanism of energy dissipation in the liquid system of nano-porous materials has been systematically studied, and the infiltration and exudation behavior of water molecules in the pore channels at molecular scale and its influence mechanism have been elucidated. The axial crushing mechanical properties of thin-walled pipe fittings filled with nano-porous material liquid system were studied. Based on different kinds of nano-porous materials, the behavior of water molecules infiltrating into molecular scale channels under external pressure was systematically studied. The effects of solid-liquid properties and pore size on the infiltration pressure were revealed by parameterized study of porous pre-treatment, electrolyte adjustment and multi-pore materials. On this basis, the concept of equivalent contact angle is put forward by using the Young Laplace equation at macroscopic scale, and it is proved that it can quantitatively describe the solid-liquid relative action at molecular scale. The dynamic mechanical properties of liquid system of nano-porous materials were studied by drop weight test, and the validity of infiltration mechanism and the correlation of rate were verified. Based on the coupling of solid, liquid and gas, the behavior of porous channels at molecular scale during the removal of water molecules under external pressure was systematically studied. Based on the observation of the correlation of the exudation behavior rate, the influence of gas molecules in the pore channels on the exudation behavior of water molecules and its failure mechanism are revealed. The pore properties and liquid properties were adjusted by introducing silica groups and adding electrolytes respectively. The effects of silica groups and electrolytes on the exudation behavior of water molecules were discussed. The corresponding seepage regulation method can effectively improve the reusability and energy absorption density of the liquid system of nano-porous materials. By means of experiments and finite element simulation, the mechanical properties of axial crushing of pipes filled with nano-porous materials were studied systematically. The mechanical properties of filled pipe under different strain rates were studied by quasi-static mechanical experiment, drop hammer impact test and Hopkinson pressure bar impact test, and the energy absorption mechanism and failure mode were analyzed. The finite element model of the liquid system filled with nano-porous material is established and verified by experiments. The coupling mechanism between the liquid system of nano-porous material and the wall of the pipe is revealed by the parameterized study of the material and structure. Based on the crushing force efficiency and energy absorption density, the design rules of filled pipes for liquid systems of nano-porous materials are summarized, which provide a reference for the engineering application of liquid systems of nano-porous materials and the development of new energy absorption components for vehicles.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U465;TB383.1

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