Electrostatic precursors to granular slip events

颗粒滑移事件的静电前兆

• 批准号: 1404792
• 负责人: Troy Shinbrot
• 金额: $ 36.5万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1404792&HistoricalAwards=false
• 关键词: Electrostatic; precursors; granular; slip; events

Non-Technical AbstractPowders and grains are used by the thousands of tons in the processing of polymers, catalysts, pharmaceuticals and building materials. Unfortunately, these materials exhibit unpredictable transitions between flow and jamming. On the large scale, these transitions manifest themselves in catastrophic slip events, causing the deaths of between 25 and 50 people annually in landslides in the US alone. On the small scale, slip events are intimately associated with material irregularities, which are far and away the dominant cause of rejections of manufactured ceramics. Recent work has demonstrated for the first time that electrical signals can be measured consistently and reproducibly as much as several seconds before any outward sign of a slip event in a powder bed. In this project, the research team will investigate the cause of these electrical precursors, establish what material properties the precursors depend on, and establish the groundwork to determine whether and when advance predictions of slip events can be made. This will certainly lead to improved understanding of an entirely new phenomenon in material science, and may conceivably have implications for earthquake and landslide prediction as well as for improved quality control for tightly regulated materials such as ceramics and pharmaceuticals.Technical AbstractThe mechanism underlying electrical voltage production in powder beds is not understood. The goal of this research is therefore to analyze this mechanism in carefully targeted experiments. In particular, questions that these experiments seek to answer are (1) what, mechanistically, occurs at the granular level to cause a transfer of charge leading to voltage production; (2) how do the electrical signals vary in space and in time; and (3) what material properties do the voltage signals depend on? The work that will be performed will be first to construct an experiment in which local charge and stress distributions can be mapped in space and in time, and second, to quantitatively evaluate how the voltage signals depend on material properties such as hardness, size and cohesivity. Measurements will be performed using electrostatic voltmeters arranged in a spatial array, complemented by visualization techniques. These measurement methods rely on existing and proven technologies, performed in unique ways designed to focus on the mechanism of interest.

粉末和谷物在聚合物、催化剂、药物和建筑材料的加工中被使用了数千吨。 不幸的是，这些材料在流动和堵塞之间表现出不可预测的转变。 在大范围内，这些转变表现为灾难性的滑动事件，仅在美国每年就有25至50人死于山体滑坡。 在小尺度上，滑动事件与材料不规则性密切相关，这是制造陶瓷被拒收的主要原因。 最近的工作首次证明，在粉末床中的任何滑动事件的向外迹象之前，可以一致地和可重复地测量电信号多达几秒钟。 在这个项目中，研究小组将调查这些电前兆的原因，确定这些前兆依赖于什么样的材料特性，并建立基础，以确定是否以及何时可以对滑动事件进行提前预测。 这肯定会导致更好地理解一个全新的现象，在材料科学，并可能会产生影响，地震和滑坡预测，以及为改善质量控制的严格管制的材料，如陶瓷和药品。 因此，本研究的目标是在仔细有针对性的实验中分析这种机制。 具体而言，这些实验试图回答的问题是：（1）在颗粒水平上发生了什么，导致电荷转移，从而产生电压;（2）电信号在空间和时间上如何变化;（3）电压信号取决于什么材料特性？ 将进行的工作将首先构建一个实验，其中局部电荷和应力分布可以在空间和时间上进行映射，其次，定量评估电压信号如何取决于材料特性，如硬度，尺寸和凝聚力。 测量将使用静电电压表安排在一个空间阵列，辅以可视化技术。 这些测量方法依赖于现有的和经过验证的技术，以独特的方式执行，旨在关注感兴趣的机制。