A study of elastic precursor decay in FCC and HCP metals under shock loading

冲击载荷下 FCC 和 HCP 金属的弹性前驱体衰变研究

• 批准号: 2446208
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2446208
• 关键词: study; elastic; precursor; decay; FCC

The dynamic behaviour of crystalline solids subjected to shock compression is of relevance to a wide range of applications, influencing for example crashworthiness in the automobile industry, armour resistance in the defence industry, and resilience to foreign object damage in aerospace, etc. The decay of the elastic precursor wave formed under shock loading conditions contains rich information regarding the origins of dynamic yielding. Despite being a topic of study for over 40 years, the microstructural origins of its behaviour remain obscured and strongly material dependent. Efforts to analytically model the decay of the precursor wave based upon elementary dislocation theory has typically resulted in an over-prediction of the initial mobile dislocation density of at least 2 orders of magnitude. Previous studies of precursor decay have mostly concentrated on strain-rate and temperature dependence of various metals such as aluminium, iron and copper, typically in the idealised annealed or single-crystal conditions. The aim of this project is to address the lack of exploration into "real" engineering alloys, investigating the role of the initial microstructural state in dynamic material behaviour. Additionally, this work will supply much-needed characterisation of variations in initial defect density, crystal orientation distributions or material processing history, which is needed to fully appreciate defect behaviour under shock loading, and which has been sorely lacking in the literature.This project presents a series impact experiments on aluminium and magnesium using a single-stage gas gun, in which a range of initial microstructural states have been examined. In aluminium, both pure and alloyed samples with varying degrees of heavy prior cold working (swaging) of up to three passes are studied. In magnesium, the focus is on the effects of material texture and crystal orientation distributions. Both cases feature materials or processing routes which have yet to be studied under dynamic loading conditions. Electron microscopy capabilities (TEM and EBSD) are leveraged in order to provide in depth knowledge of the microstructural parameters influencing the dynamic response. As a whole, this study is able to provide a dataset which is unique in its range of materials under consideration, its use of modern velocimetry techniques and its delivery of detailed knowledge of the initial microstructural state. Together this will fill a crucial gap in the experimental data needed in order to advance our theoretical understanding of dynamic material response. A collaboration with Israel Institute of Technology researchers making use of this distinctive dataset in order to model the material behaviour is currently underway.This project falls within the EPSRC Physical Sciences research area and is partly funded by AWE plc through an iCASE studentship.

受到冲击压缩的结晶固体的动态行为与广泛的应用有关，例如影响汽车工业中的耐撞性，国防工业中的装甲抗性，以及航空航天中对异物损伤的弹性等。在冲击载荷条件下形成的弹性前驱波的衰减包含关于动态屈服起源的丰富信息。尽管是一个研究课题超过40年，其行为的微观结构起源仍然模糊和强烈的材料依赖性。基于基本位错理论对前驱波的衰减进行分析建模的努力通常导致至少2个数量级的初始移动的位错密度的过度预测。以前的前体衰变的研究主要集中在应变率和温度依赖性的各种金属，如铝，铁和铜，通常在理想化退火或单晶条件。这个项目的目的是解决缺乏对“真实的”工程合金的探索，研究初始微观结构状态在动态材料行为中的作用。此外，这项工作将提供急需的初始缺陷密度，晶体取向分布或材料加工历史的变化，这是需要充分了解冲击载荷下的缺陷行为，这是文献中严重缺乏的。其中已经检查了一系列初始微观结构状态。在铝，纯和合金样品与不同程度的重型前冷加工（模锻）多达三个通道进行了研究。在镁中，重点是材料织构和晶体取向分布的影响。这两种情况下的材料或工艺路线，还有待研究动态负载条件下。电子显微镜的能力（TEM和EBSD）的杠杆作用，以提供深入的知识的微观结构参数影响的动态响应。作为一个整体，这项研究能够提供一个数据集，这是唯一的在其范围内的材料正在考虑，其使用现代测速技术和其交付的详细知识的初始微观结构状态。总之，这将填补一个关键的空白，所需的实验数据，以促进我们的动态材料响应的理论理解。与以色列理工学院的研究人员合作，利用这一独特的数据集，以模拟材料的行为目前正在进行中。该项目属于EPSRC物理科学研究领域的福尔斯，部分由AWE plc通过iCASE学生资助。