非连续剪切增稠液冲击条件下的液-固转换机理研究

Discontinuous shear thickening fluid is a kind of rate-sensitive smart soft materials. As it has the energy absorption capacity and is good in resistance to shock, this material has wide application in vibration control, body protection ect. However, our understanding of the mechanism of the liquid-solid transformation is not yet well known. Based on the changing process of the attractive energy between the particles, this proposed project is aimed to develop a method to analyze the relations between the macro liquid-solid transformation and the micro structure evolution, than brought forward a mechanism of the liquid-solid transformation. Primary coverage of this proposed project include: (1) On the side of the mechanical test, the Hopkinson bar technology is be used to test the mechanical response and the critical occurrence of the liquid-solid transformation. (2) On the side of the microstructure observation, the ultrasound technology and the X-ray technology are used to get the evolution of the force chain and the information of the grain deformation. (3) On the side of the theoretical analysis, based on the jamming mode for attractive particles, the relationship between the shear rate and the attractive energy between the particles is established. When this proposed project is successfully accomplished, the research results will help to the have a deeper understanding of the liquid-solid transformation and further improve its application in the engineering areas. Also, the research results will help to understand the nature of the glassy state by jamming and develop the glass transition theory.

非连续剪切增稠液是一种率敏智能软材料，具有能量吸收、抗冲击等优异性能，在振动控制、人体防护等领域具有重要应用，然而目前对其液-固转换发生机理的认识仍不全面。本项目申请拟以颗粒间吸引能变化关系为桥梁，发展分析宏观液-固转换与微观颗粒演化之间关系的方法，提出新的液-固转换机理。研究内容包括：在力学测试方面，基于Hopkinson杆技术，测试力学响应，研究转换发生的临界条件。在微结构观测方面，基于超声波技术，获得整体力链演化信息；基于X-ray技术，获得局部颗粒形状变化信息。在理论分析方面，根据颗粒间微结构信息，基于接触理论，建立应变率与颗粒间吸引能的关系；基于吸引堵塞模型，证实其玻璃化转变实质上是颗粒间强相互吸引下的堵塞转变。本申请项目研究工作的开展，可以深化认识其液-固转换现象，进而合理有效地解决该材料的工程应用；同时，有望探索出一条以堵塞转变认识玻璃态本质的新途径，发展玻璃化转变理论。

非连续性剪切增稠液是一类率敏智能颗粒悬浮液，在高速冲击下其力学性能发生急剧变化，由液态变为固态。流体润滑力引起的粒子簇模型由于没有引入颗粒间的接触力已无法解释液-固转换现象。建立新的描述液-固转换机理关键在于：测得颗粒间接触力并分析其演化过程。本项目主要研究内容包括：建立测试高速加载条件下表征非连续性剪切增稠液力学性能方法；得到完整的剪切速率、剪切应力和法向力力学响应；定义剪切角描述力链的形成及发展过程，解释液-固转换机理；分析固态非连续性剪切增稠液的特性，划分相变过程，得到相变图。. 通过上述工作的开展，将流变仪的采集信号从10Hz提高到10kHz，得到准确、致密的力学响应信号；处理上述力学响应信号得到剪切应力-剪切应变曲线，总结得到破坏应力与体积分数呈线性关系；分析力链角演化过程，证实液-固转换机理是颗粒间接触形成力链网状结构；研究固态非连续性剪切增稠液特性，将其划分为脆性阶段与稳定阶段；绘制剪切应力-体积分数相变图，归纳总结液-固转换过程。本项目得到的液-固机理结论，可为血液堵塞、泥石流等发生机制提供参考。