Mechanisms and Characterisation of Explosions (MaCE)

高爆炸冲击荷载对结构的影响分析在运输安全、基础设施评估和国防保护等方面有着广泛的应用。工程师必须以高效和有效的方式利用材料，以减轻作用于毫秒级的极端载荷。但有一个基本问题阻碍了这一领域的研究和实践;我们仍然没有完全了解高爆炸冲击波产生的载荷。在上个世纪中期，爆炸载荷的科学表征是一个紧迫的问题，因为研究人员开发了预测大型常规爆炸和距离目标相对较远的原子武器的载荷的方法。这项工作花费了大量的精力，以及一些世界领先的物理学家和数学家（GI）的参与泰勒，约翰冯诺依曼）反映了这种威胁的存在性质。这项工作的主要基础是研究距离爆炸较远（远场）的目标上的爆炸载荷。在过去的几十年里，虽然在理解和设计材料以承受特殊载荷方面取得了很大进展，但爆炸载荷本身的实验特性在三个关键领域没有跟上步伐，这是本项目直接旨在解决的问题：首先，我们不知道非常接近高爆炸引爆的目标上的爆炸载荷的大小。今天的恐怖主义威胁往往来自较小的、集中的近距离爆炸。在将炸弹偷运到飞机上或对关键基础设施的关键项目进行有针对性的攻击等情况下，这种“近场”装载可能具有破坏性。但是，几乎完全没有高质量的实验工作，表征近场爆炸载荷。目前，对这些安全关键区域的预测依赖于简单远场模型的外推，或使用未经充分验证的数值模型。该项目将提供新的、经过适当验证的、基于高质量实验工作的数值模型来解决这一问题。我们目前的爆炸到冲击波机制模型是基于简化的假设，如爆炸时能量基本上是瞬间释放的。虽然这似乎对远场很有效，但在近场的有效性存在重大疑问。该项目将汇集爆炸工程师，高温实验学家和高能化学研究人员，以确定爆炸火球和大气氧气之间的早期爆炸后化学反应在释放能量中的作用，以及如何影响随后的爆炸载荷。该项目中收集的数据将允许基于新颖的实验分析创建新的概念性爆炸模型。最后一个知识缺口是，在控制良好的科学实验中，爆炸载荷本质上是确定性的还是混沌的。如果爆炸荷载研究界要进行相当于标准风洞或振动台试验的试验，解决这个问题是至关重要的。我们的初步工作已经导致了这样的假设，即在近场和远场之间的边界处存在一个区域，火球中的不稳定性将导致压力载荷的大的和随机的空间和时间变化，但是无论哪一边，载荷都应该是确定性的和可确定的。该项目将提供数据来验证这一假设，从而能够为该领域的其他研究人员提供指导，通过多学科实验研究方案填补这些空白，将使我们对爆炸载荷的理解和我们抵御爆炸威胁的能力发生重大变化。

Analysis of the effects of high explosive blast loading on structures has applications in transport security, infrastructure assessment and defence protection. Engineers must utilise materials in efficient and effective ways to mitigate loads of extreme magnitudes, acting over milliseconds. But there is a fundamental problem which hampers research and practice in this field; we still do not fully understand the loads generated by a high explosive blast.Scientific characterisation of blast loading was a pressing issue in the middle of the last century, as researchers developed methods to predict the loading from large conventional blasts, and from atomic weapons at relatively long distances from targets. The huge amount of effort expended on this work, and the involvement of some of the world's leading physicists and mathematicians (G.I. Taylor, John von Neumann) reflected the existential nature of that threat. This work was predominately based on studying blast loading on targets at relatively long distances from detonations (far-field). Over the past few decades, whilst great advances have been made in understanding and designing materials to withstand extraordinary loads, experimental characterisation of blast loading itself has not kept pace in three key areas, which this project directly aims to address:Firstly, we don't know the magnitudes of explosive loading on targets very close to a high explosive detonation. Today's terrorist threats are frequently from smaller, focused, close-range explosions. Scenarios such as bombs smuggled onto aircraft, or targeted attacks on key items of critical infrastructure are ones in which such "near-field" loading is potentially devastating. But there is an almost total absence of high quality experimental work on characterising near-field blast loading. Predictions in these safety-critical areas currently rely on extrapolation of simple far-field models, or the use of inadequately validated numerical models. The project will provide new, properly validated, numerical models based on high quality experimental work to address this.This raises the second knowledge gap. Our current models of detonation-to-blast-wave mechanisms are based on simplified assumptions, such as that energy is released essentially instantaneously on detonation. Whilst this appears to work well for the far-field, there are major doubts over its validity in the near-field. This project will bring together blast engineers, high-temperature experimentalists, and energetic chemistry researchers to identify the role of early-stage post-detonation chemical reactions between the explosive fireball and the atmospheric oxygen in releasing energy, and how that affects the subsequent blast loading. The data gathered in the project will allow a new conceptual blast model to be created based on novel experimental analysis. The final knowledge gap is the question of whether blast loading in well-controlled scientific experiments is essentially deterministic or chaotic in nature. Addressing this issue is vital if the blast loading research community is to have the equivalent of a standard wind tunnel or shaking table test. Our preliminary work has led to the hypothesis that there is a region at the boundary between the near- and far-fields, where instabilities in the fireball will lead to large and random spatial and temporal variations in pressure loading, but that either side of this, the loading should be deterministic and determinable. The project will provide the data to validate this hypothesis, thus being able to provide guidance to other researchers in the field.Addressing these gaps, through a programme of multi-disciplinary experimental research, will produce a step change in our understanding of blast loading and our ability to protect against blast threats.