Name: a method for studying the temperature dependence of dynamic fracture and fragmentation
Uploaded: 2015-06-28T14:00:00.000+00:00
Duration: 9 min 12 s
Description: Watch this Scientific Journal Video about A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation at JoVE.com

The authors gratefully acknowledge continued funding and support for the project from the Atomic Weapons Establishment, AWE Plc. (UK) and Imperial College London.

1.目标制造和组装<ol><li>机目标油缸从固体股票所需的尺寸。 </li><li>通过去除加工痕迹准备滚筒表面。均匀的漫反射面最好的PDV反思。了良好的结果得到具有光水磨与&gt; 1200砂砾。 </li><li>表征目标成分， 即测量以下: 筒的长度，直径和壁厚（在多个位置） 弹的长度，直径 顶弧的长度，直径 所有的上述质量</li><li>安装在气缸安装环和手臂PDV。 </li><li>安装PDV探针运动的坐骑和到PDV手臂。 </li><li>插入对象气缸中的拱形体，使得拱形体的后部是与缸的后部平齐（这应该在一个车间平面来完成）。这三个M3螺丝的设计保持了弧顶的地方，同时允许缸&#39;剥离AW在扩展时，AY"。 </li><li>放置在目标气缸中的安装硬件，以使圆筒的入口是与安装环的前端面齐平。固定在气缸内到位6 M4平头螺钉。 </li><li>沿气缸外壁的长度安装的加热/冷却装置和键热电偶。 </li><li>清洁FC / APC（套圈连接器，倾斜的身体接触）接口PDV探头纤维纤维清洁布的结束和检查用光纤镜。这一点很重要，以减少背反射。 </li><li>使用可见光（660纳米）3R类激光大致对齐的探针，使它们垂直于所述气缸（ 即 ，反射光的探头落回）。 </li><li>安装使用循环基本反射率电路。 1类1550纳米激光连接至输入端1，对PDV探头输入2和功率计输入3.对齐PDV探针反过来使得返回的功率被最大化。 </li></ol><ol><li>使用桶塞和深度千分尺校准目标环到筒的末端，以减少冲击倾斜。 </li><li>安装片段减灾系统和门保护。 </li><li>放置在枪管的目标对准塞。 </li><li>安装目标组件和对准塞。 </li><li>在筒的端部安装在触发化妆配对并连接到定时硬件和诊断。从测量与触发到弧顶弹丸撞击接触的距离。 </li><li>安装高速摄影的转向镜。 </li><li>对准反射镜，得到通过目标箱口的汽缸的正交视图，并锁定就位。 </li><li>对准高速摄像机和闪光灯的目标槽外。俯视枪管，放置高速摄像机和一个闪光灯在3点钟相对于汽缸。将相机IVV在9点钟和另一个闪光灯在12点。在此配置中，高速相机将前光裂纹跟踪和IVV将提供映衬图像的边缘检测。 </li><li>连接加热/冷却设备的目标和真空馈电得来。 </li><li>注意:用合适的眼镜和其他注意事项打开IV级激光器，示波器和PDV系统。 </li><li>检查的功率电平被发送到PDV探针。与PDV系统，通常使用约5毫瓦每个探针与每通道1毫瓦为参考。 </li><li>检查PDV探头对准功率计。一旦满意的取向使用红外卡以测量那里的PDV探针正在寻找的圆柱体表面上。 </li><li>打开的参照用激光，并检查由每个探针给出的差拍信号的质量。调整激光（S）以设置所需的零速度差频的波长（设置此约5千兆赫）。 </li><li>一旦满意的目标阿里gnment，触发位置，摄像头和反光镜调整，PDV探头对准和位置，并缓解框架关闭目标坦克。 </li><li>取下对准插头;安装弹丸。 </li><li>安装摄像头和照明（帧速率，曝光，定时），并进行测试成像。典型的帧速率大约250,000帧/秒，这两款相机，拥有约0.5微秒曝光。第一图像通常定时为与冲击的瞬间重合。 </li></ol> 3.准备射击<ol><li>安装臀位隔膜是适用于需要烧制压力。 </li><li>关闭臀位，并开始在目标坦克撤离。目标为在50毫托的区域的真空度。 </li><li>执行所有诊断的最终设置（示波器延迟，触发器，相机设置等 ）。集示波器为PDV在50微秒每格，每点25皮秒和20％的预触发，得到500微秒的窗口。触发邻scilloscopes和摄像头，使得零时间恰逢影响的时间。 </li><li>最终触发测试;检查计时是否准确。 </li><li>打开激光器;手臂相机。 </li><li>关闭室;确保激光和高压互锁是在正确的位置。 </li><li>使用LabVIEW软件要求开始加热/冷却。 </li><li>充电枪所需的点火压力。 </li><li>当在压力下，做最后的检查，所有诊断系统武装。 </li><li>隔离的加热或冷却装置。 </li><li>倒计时"3，2，1火"。 </li><li>发泄目标和捕获的坦克。 </li><li>保存所有示波器和相机数据。 </li></ol> 4.前次拍摄<ol><li>关闭激光器和等待枪充分均衡在大气中。 </li><li>打开目标槽，收集所有的金属碎片和整理出的Ti-6AL-4V。 </li></ol> 5.数据分析<ol><li>执行STFT分析的PDV OScilloscope数据，以减少速度历史敖每刀郎和12的分析。 </li><li>与软件，如提到的设备表的过程的高速成像数据。高速摄像机镜头将提供时间和破坏应变，使裂纹的形成和生长分析。的映衬图像从IVV提供清晰边缘检查气缸的充分变形轮廓。 </li><li>测量和称重回收的片段。选择与有趣的功能片段，如逮捕骨折并准备显微镜。 <ol><li>节，安装，和波兰的片段;然后分析在电子显微镜。电子背散射衍射提供的质地和微观结构沿着二次电子成像信息探测断裂面，并确定故障模式。 </li></ol></li></ol>

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The authors have nothing to disclose.

此方法使材料在拉伸加载的高速率调查在宽的温度范围内，从低温到〜1000 K，独特这种设计。然而，这增加了一定的挑战实验设置和执行。首先，以优化温度控制的拱形插入件需要由合适的材料加工。 4340钢用在这里，虽然任何高温高硬度钢应该足够了。同样，因为整个扩张驱动器现在从聚合物弹丸始发此需要从一个非脆性塑料制成，如机级聚碳酸酯在此工作。 具有插入件和...

材料的动态破坏是其整体机械性能的一个重要方面，并具有关联到众多行业，包括汽车，航空航天和军事仅举几。而在低应变速率失败通常是通过常规的拉伸试验，在其中一个细长的样品在从端部张力加载，在高应变率研究这样的形状/配置需要一个样品是非常小的，以便保持一个整个试验伪机械平衡。在一个单一的裂缝的外观，周围的材料会放宽，有效地阻止了任何相邻失效站点的发展。这限制了可以在任一项实验中同时观察到骨折的人数，并防止有关故障的统计数据来确定的重要信息。 扩缸测试是一种行之有效的技术特征以何种方式魔石LS失败，并在高速负荷片段。在测试中，取得所关心的材料的圆筒沿其内圆周被均匀地加载，发射穿过壁的应力波和使所述圆筒膨胀。不久，这样的径向波消散和周围的圆周均匀拉伸环向应力占主导地位。为应力和应变率是断裂和破碎行为是由材料的性质完全支配气缸周围一样。测试缓解了上述问题，因为一般大样本的圆周均匀应力1下促进多个故障点开始。 在开发这种实验技术的主要目的是使温度在不断扩大的圆筒的断裂和碎裂行为中的作用的研究。的样品温度的控制将允许调查如何动态拉伸强度，断裂机制，fragm该材料的entation行为受到影响。例如在金属，温度的升高可引起从脆性转变为韧性断裂，最终失败之前容纳更多的塑料的工作。有些材料如Ti-6AL-4V也能表现出绝热剪切本地化2。而样品变形，塑性工作产生热。如果软化作为该温度升高的结果的速率大于工作从变形硬化的速率，不稳定性可以形成，其中有大量的塑性变形在一个非常局部频带（绝热剪切带）发生。这种反应被促进在钛一6A1-4V由于其导热性差，并有可能限制其有效性的应用，如轻型装甲。 这种新的测试方法必须满足两个主要标准。首先，该方法必须产生10 4秒-1的量级的径向应变率，通常见于弹道和影响的事件，让比较以往的研究多采用传统的装载方案。其次，驱动机构需要由样品温度下不受影响，以确保实验之间的一致性。最初的汽缸膨胀机构使用的炸药，要么干脆直接填充样品缸3-5或使用中间驱动程序。在后一种情况下，一个缓冲器用于6，其中样品被放置在一个钢筒，在依次包含炸药。的明显限制是，作为样品气缸装有驱动器的材料（在炸药的形式）加热缸也将加热的电荷。虽然这可能不是直接引起的电荷开始许多类型的爆炸性的含有聚合物粘合剂材料，将来自样品气缸融出。同样地，当冷却时一些炸药变得非常敏感。这意味着，炸药驱动器不适合于温度研究。另一种方法使用洛伦兹力扩张-样品被放置在一个驱动线圈7，8的高电流注入该驱动线圈（通常重型铜丝），诱导样品中的相对电流。这些对立的电流有关联的磁场而相互采取行动，磁压力的内面驱动向外样本。再次，加热该材料将产生不利的样品内的铜驱动线圈的影响。自从20世纪70年代晚9气体枪已被用于气缸膨胀。在这些实验中使用的缸中的插入件的材料是一种聚合物，所述驱动未来既是弹丸的结果，并插入变形在冲击。此插入通常是橡胶或塑料10中，强度和延展性，其中将受到严重影响的温度。暖气会使插入太软了，散热会使其行为在脆性的方式，以便它失败过早。 实验几何由拱形体安装在目标气缸内，与位于大约沿着圆筒的长度中途尖端一个钢。单级光气枪然后用于向上发射的聚碳酸酯弹丸的凹面进入气缸的速度下，以1000米/秒-1。靶的轴线是圆筒小心地对准到气体枪管的轴线，以便于可重复和一致的负载。宝的影响和随后的流周围的伪刚性钢风帽lycarbonate弹，带动缸到从内壁扩张。小心使用拱形体插入件和弹丸的凹面的几何形状进行了优化的水力代码的计算机模拟，以产生气缸所需的扩张。使用4340合金钢为拱形体使实验与汽缸在温度作为其强度比聚碳酸酯弹丸在感兴趣的温度范围高得多，从而确保该驱动机构保持一致。 Ogives从加热和冷却实验只追回表现出最小的变形的影响的结果。 样品圆筒的加热和冷却是通过温度控制硬件安装完成到在拱形体插入件的后部的机加工凹槽。用于冷却样品到低温（〜100 K），在拱形体的凹部是密封的铝盖和液氮为flowed通过空腔。作为目标气缸具有与样品通过传导冷却的拱形体接触面积大。来加热对象气缸到温度接近1000 K，陶瓷和镍铬合金电阻加热器被放置在拱形凹槽。高电流电源提供高达1千瓦，加热顶弧和缸体。气缸和卵形被热从目标隔离在单级气 - 炮架通过使用MACOR陶瓷隔板。该坦克还适度真空（&lt;0.5托）下这有助于热操纵实验期间举行。 为了诊断气缸的碎裂过程中，实验设计包括变频PDV多个通道，以测量在沿着汽缸点的膨胀速度。 PDV是一个相对较新的11，基于光纤的干涉技术，该技术使得能在高动态事件表面速度的测定。在一个PDV测量，多普勒频移从感兴趣的移动表面用光纤探针是结合未移位的光，产生一个拍频成正比的移动表面的速度的反射光。从本质上讲，PDV系统是使用在近红外（1550纳米）的通信技术的进步，以在GHz范围记录的拍频快速迈克尔逊干涉仪。在当前研究中使用100毫米焦距PDV探针的安装系统可确保它们从滚筒的温度分离和提供更容易对齐。用100毫米焦距的探针的另一优点是，它们提供足够的光学访问启用高速摄影测量整个汽缸的膨胀轮廓。四个探针，AD的排列和位置，沿着汽缸示于图1的两个高速摄像机这里采用。高速摄像机幻影V16.10操作25万FPS和IVV超高速集成电路12/24幅相机，捕捉24幅图像。该IVV照相机背光，使得气缸被照亮的剪影使气缸的径向扩大的边缘被精确地跟踪。幽灵相机正面受光影像的失败并开始分段处理。高速摄影然后可以与测速相关，得到应变和应变率沿整个样本。高速成像也允许精确测量破坏应变及断裂模式沿表面。 实验方法在下面的协议部分中提供提供了一种控制在膨胀汽缸的实验中，通过该不同断裂机理可以被激活或抑制样品温度的手段。该技术会导致温度的动态负载情况下的作用，更全面的了解。

<table><tbody><tr><td>1,550 nm CW Laser</td><td>NKT Photonics</td><td>Koheras Adjustik</td><td>x 2</td></tr><tr><td>1,550 nm Power Amplifier</td><td>NKT Photonics</td><td>Koheras Boostik HPA</td><td></td></tr><tr><td>Delay Generators</td><td>Quantum Composers</td><td>9500+ Digital Delay Pulse Generator</td><td>8 output version</td></tr><tr><td>Stanford Research Systems</td><td>DG535 Digital Delay Generator</td><td></td><td></td></tr><tr><td>16 Channel Digitiser</td><td>Agilent Technologies</td><td>U1056B Chassis + 4 X U1063A Digitiser</td><td></td></tr><tr><td>High Bandwidth Oscilloscopes</td><td>Teledyne LeCroy</td><td>WaveMaster 816Zi-A</td><td>Expansion Velocity, Gen 3 PDV</td></tr><tr><td>Tektronix</td><td>DPO71604C</td><td>Projectile Velocity, Gen 1 PDV</td><td></td></tr><tr><td>High Speed Imaging Systems</td><td>Vision Research</td><td>Phantom v16.10</td><td></td></tr><tr><td>Invisible Vision</td><td>IVV UHSi-24</td><td></td><td></td></tr><tr><td>Zeiss Optics</td><td>Planar T* 1,4/85</td><td>85 mm Prime Lens</td><td></td></tr><tr><td>Nikon</td><td>AF-S Nikkor 70-200 mm f/2.8 ED VR II</td><td>70-200 mm Telephoto Lens</td><td></td></tr><tr><td>Flash Lamp</td><td>Bowens</td><td>Gemini Pro 1500 W</td><td>x 2</td></tr><tr><td>PDV Probe</td><td>Laser 2000</td><td>LPF-04-1550-9/125-S-21.5-100-4.5AS-60-3A-3-3</td><td>x 4 (Custom order)</td></tr><tr><td>PDV System</td><td>Built in-house by the Institute of Shock Physics</td><td>Custom Build</td><td>3&lt;sup&gt;rd&lt;/sup&gt; Generation (Upshifted) 8 Channel Portable PDV System</td></tr><tr><td>Control Software</td><td>National Instruments</td><td>LabVIEW 2013</td><td></td></tr><tr><td>Control Hardware for heating</td><td>National Instruments</td><td>NI-DAQ 6009 USB</td><td></td></tr><tr><td>Heating Power Supply</td><td>BK Precision</td><td>BK1900</td><td></td></tr><tr><td>Thermocouple Logger</td><td>Pico Technology</td><td>TC-08</td><td></td></tr><tr><td>100 mm Single Stage Light Gas Gun</td><td>Physics Applications, Inc. (PAI)</td><td>Custom Build</td><td>Capable of at least 1,000 m/sec with ~2 kg projectile</td></tr><tr><td>Image analysis software</td><td>National Institutes of Health</td><td>ImageJ</td><td>Open source, free</td></tr><tr><td>Image analysis software</td><td>Mathworks</td><td>MATLAB r2014a</td><td>With image processing toolboxes</td></tr><tr><td>Material sectioning saw</td><td>Struers</td><td>Accutom-50</td><td></td></tr><tr><td>Electron Microscope</td><td>Zeiss</td><td>Auriga</td><td></td></tr><tr><td>Electron Backscatter Diffraction</td><td>Bruker</td><td>e-Flash 1000</td><td></td></tr><tr><td>EBSD software</td><td>Bruker</td><td>eSprit</td><td></td></tr></tbody></table>

a method for studying the temperature dependence of dynamic fracture and fragmentation

一体的动态断裂是晚期现象通常简化条件下，在其中将样品均匀的应力和应变速率下变形下研究。这可以通过均匀地装入一个圆筒的内表面来制造。由于轴对称，随着气缸膨​​胀壁被置于拉伸箍应力即围绕圆周均匀。虽然有多种技术来产生这种扩张例如爆炸物，电磁驱动器，和现有的气枪技术它们都限定在一个事实，即样品气缸必须在室温下进行。我们提出使用气体喷枪便于实验上从150 K至800ķ缸具有一致的，可重复加载的新方法。这些高度诊断实验用来检验温度对断裂机制负责故障，以及它们对碎片统计所得的影响的效果。实验几何形状采用了钢卵形位于靶圆筒内，与位于大约一半的小费。单级光气枪，然后用于启动聚碳酸酯弹丸进入气缸在1000米/秒-1。弹丸冲击和周围的刚性顶弧流，找到从内侧样品圆柱体。使用一个不变形的拱形插入件使我们能够安装温度控制硬件缸体的后部内。液氮（LN 2）用于冷却和电阻高电流负载进行加热。的换高档光子多普勒测速（PDV）的多个信道跟踪沿气缸使直接比较计算机模拟的膨胀速度，而高速成像用于测量断裂应变。将回收筒片段也受到光学和电子显微镜，以确定失效机理。

数据的质量将首先取决于实验定时。如果延迟从触发到影响都是正确的那么闪光灯会产生足够的光线在目标缸开始变形，使高速摄像机，以产生清晰的图像。在这种情况下，从取景相机的图像将有一个明确的映衬边缘可用于跟踪整个圆柱体的变形。软件如ImageJ的可用于提取线路输出对各帧数据，生成一个图像， 如图2。理想情况下，PDV就能追踪膨胀速度为〜100微秒，这将取决于圆筒的...

Watch this Scientific Journal Video about A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation at JoVE.com

A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

Fracture and fragmentation are late stage phenomena in dynamic loading scenarios and are typically studied using explosives. We present a technique for driving expansion using a gas gun which uniquely enables control of both loading rate and sample temperature.

为研究动态断裂及破碎的温度敏感性的方法

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform ...

a-method-for-studying-temperature-dependence-dynamic-fracture

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Unit 1

Concept of Stress

Temperature and Heat

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8.5K 次观看.  Imperial College London. Fracture and fragmentation are late stage phenomena in dynamic loading scenarios and are typically studied using explosives. We present a technique for driving expansion using a gas gun which uniquely enables control of both loading rate and sample temperature.

视频: A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

在极端的压力和温度的合成和Microdiffraction

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

科研

工程学

High-pressure, High-temperature Deformation Experiment Using the New Generation Griggs-type Apparatus

In order to address geological processes at great depths, rock deformation should ideally be tested at high pressure (&#62; 0.5 GPa) and high temperature (&#62; 300 &#176;C). However, because of the low stress resolution of current solid-pressure-medium apparatuses, high-resolution measurements are today restricted to low-pressure deformation experiments in the gas-pressure-medium apparatus. A new generation of solid-medium piston-cylinder (&#34;Griggs-type&#34;) apparatus is here described. Able to perform high-pressure deformation experiments up to 5 GPa and designed to adapt an internal load cell, such a new apparatus offers the potential to establish a technological basis for high-pressure rheology. This paper provides video-based detailed documentation of the procedure (using the &#34;conventional&#34; solid-salt assembly) to perform high-pressure, high-temperature experiments with the newly designed Griggs-type apparatus. A representative result of a Carrara marble sample deformed at 700 &#176;C, 1.5 GPa and 10-5 s-1 with the new press is also given. The related stress-time curve illustrates all steps of a Griggs-type experiment, from increasing pressure and temperature to sample quenching when deformation is stopped. Together with future developments, the critical steps and limitations of the Griggs apparatus are then discussed.

Rock deformation needs to be quantified at high pressure. A description of the procedure to perform deformation experiments in a newly designed solid-medium Griggs-type apparatus is here given. This provides technological basis for future rheological studies at pressures up to 5 GPa.

新一代格雷型装置高压高温变形试验

In order to address geological processes at great depths, rock deformation should ideally be tested at high pressure (&#62; 0.5 GPa) and high temperature ...

环境科学

Stress Distribution During Cold Compression of Rocks and Mineral Aggregates Using Synchrotron-based X-Ray Diffraction

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) coupled with synchrotron X-radiation. A cube-shaped sample assembly is prepared and compressed, at room temperature, by a set of four X-ray transparent sintered diamond anvils and two tungsten carbide anvils, in the lateral and the vertical planes, respectively. All six anvils are housed within a 250-ton hydraulic press and driven inward simultaneously by two wedged guide blocks. A horizontal energy dispersive X-ray beam is projected through and diffracted by the sample assembly. The beam is commonly in the mode of either white or monochromatic X-ray. In the case of white X-ray, the diffracted X-rays are detected by a solid-state detector array that collects the resulting energy dispersive diffraction pattern. In the case of monochromatic X-ray, the diffracted pattern is recorded using a two-dimensional (2-D) detector, such as an imaging plate or a charge-coupled device (CCD) detector. The 2-D diffraction patterns are analyzed to derive lattice spacings. The elastic strains of the sample are derived from the atomic lattice spacing within grains. The stress is then calculated using the predetermined elastic modulus and the elastic strain. Furthermore, the stress distribution in two-dimensions allow for understanding how stress is distributed in different orientations. In addition, a scintillator in the X-ray path yields a visible light image of the sample environment, which allows for the precise measurement of sample length changes during the experiment, yielding a direct measurement of volume strain on the sample. This type of experiment can quantify the stress distribution within geomaterials, which can ultimately shed light on the mechanism responsible for compaction. Such knowledge has the potential to significantly improve our understanding of key processes in rock mechanics, geotechnical engineering, mineral physics, and material science applications where compactive processes are important.

We report detailed procedures for compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus coupled with synchrotron X-radiation. Such experiments allow quantification of the stress distribution within samples, that ultimately sheds light on compaction processes in geomaterials.

基于同步辐射 x 射线衍射的岩石和矿物团聚体冷压缩应力分布

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) ...

Laser-heating and Radiance Spectrometry for the Study of Nuclear Materials in Conditions Simulating a Nuclear Power Plant Accident

Major and severe accidents have occurred three times in nuclear power plants (NPPs), at Three Mile Island (USA, 1979), Chernobyl (former USSR, 1986) and Fukushima (Japan, 2011). Research on the causes, dynamics, and consequences of these mishaps has been performed in a few laboratories worldwide in the last three decades. Common goals of such research activities are: the prevention of these kinds of accidents, both in existing and potential new nuclear power plants; the minimization of their eventual consequences; and ultimately, a full understanding of the real risks connected with NPPs. At the European Commission Joint Research Centre&#39;s Institute for Transuranium Elements, a laser-heating and fast radiance spectro-pyrometry facility is used for the laboratory simulation, on a small scale, of NPP core meltdown, the most common type of severe accident (SA) that can occur in a nuclear reactor as a consequence of a failure of the cooling system. This simulation tool permits fast and effective high-temperature measurements on real nuclear materials, such as plutonium and minor actinide-containing fission fuel samples. In this respect, and in its capability to produce large amount of data concerning materials under extreme conditions, the current experimental approach is certainly unique. For current and future concepts of NPP, example results are presented on the melting behavior of some different types of nuclear fuels: uranium-plutonium oxides, carbides, and nitrides. Results on the high-temperature interaction of oxide fuels with containment materials are also briefly shown.

We present experiments in which real nuclear fuel, cladding, and containment materials are laser heated to temperatures beyond 3,000 K while their behavior is studied by radiance spectroscopy and thermal analysis. These experiments simulate, on a laboratory scale, the formation of a lava-phase following a nuclear reactor core meltdown.

核材料在核电厂事故模拟条件下的激光加热和辐射光谱研究

Major and severe accidents have occurred three times in nuclear power plants (NPPs), at Three Mile Island (USA, 1979), Chernobyl (former USSR, 1986) and ...

化学

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and increasing the recovery of coalbed methane. A visualized and constant-volume gas-solid coupling system is introduced here to investigate the influence of CO2 sorption on the physical and mechanical properties of coal. Being able to keep a constant volume and monitor the sample using a camera, this system offers the potential to improve instrument accuracy and analyze fracture evolution with a fractal geometry method. This paper provides all steps to perform a uniaxial compression experiment with a briquette sample in different CO2 pressures with the gas-solid coupling test system. A briquette, cold-pressed by raw coal and sodium humate cement, is loaded in high-pressure CO2, and its surface is monitored in real-time using a camera. However, the similarity between the briquette and the raw coal still needs improvement, and a flammable gas such as methane (CH4) cannot be injected for the test. The results show that CO2 sorption leads to peak strength and elastic modulus reduction of the briquette, and the fracture evolution of the briquette in a failure state indicates fractal characteristics. The strength, elastic modulus, and fractal dimension are all correlated with CO2 pressure but not with a linear correlation. The visualized and constant-volume gas-solid coupling test system can serve as a platform for experimental research about rock mechanics considering the multifield coupling effect.

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

This protocol demonstrates how to prepare a briquette sample and conduct a uniaxial compression experiment with a briquette in different CO2 pressures using a visualized and constant-volume gas-solid coupling test system. It also aims to investigate changes in terms of coal&#8217;s physical and mechanical properties induced by CO2 adsorption.

使用可视化和恒定体积气体-固体耦合测试系统使用 CO2轴承煤的单轴压缩实验

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and ...

Conducting Elevated Temperature Normal and Combined Pressure-Shear Plate Impact Experiments Via a Breech-end Sabot Heater System

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The method enables elevated temperature plate-impact experiments aimed towards probing dynamic behavior of materials under thermomechanical extremes, while mitigating several special experimental challenges faced while performing similar experiments using the conventional plate impact approach. Custom adaptations are made to the breech-end of a single-stage gas-gun at Case Western Reserve University; these adaptations include a precision-machined extension piece made from SAE 4340 steel, which is strategically designed to mate the existing gun-barrel while providing a high tolerance match to the bore and keyway. The extension piece contains a vertical cylindrical heater-well, which houses a heater assembly. A resistive coil heater-head, capable of reaching temperatures of up 1200 &#176;C, is attached to a vertical stem with axial/rotational degrees of freedoms; this enables thin metal specimens held at the front-end of a heat-resistant sabot to be heated uniformly across the diameter to the desired test temperatures. By heating the flyer plate (in this case, the sample) at the breech-end of the gun-barrel instead of at the target-end, several critical experimental challenges can be averted. These include: 1) severe changes in the alignment of the target plate during heating due to the thermal expansion of the several constituents of the target holder assembly; 2) challenges that arise due to the diagnostics elements, (i.e., polymer holographic gratings, and optical probes) being too close to the heated target assembly; 3) challenges that arise for target plates with an optical window, where crucial tolerances between the sample, bond layer, and window become increasingly difficult to maintain at high temperatures; 4) in the case of combined compression-shear plate impact experiments, the need for high-temperature resistant diffraction gratings for the measurement of transverse particle velocity at the free surface of the target; and 5) limitations imposed on the impact velocity necessary for unambiguous interpretation of the measured free surface velocity versus time profile due to thermal softening and possibly yielding of the bounding target plates.By utilizing the adaptations mentioned above, we present results from a series of reverse geometry normal plate impact experiments on commercial purity aluminum at a range of sample temperatures. These experiments show decreasing particle velocities in the impacted state, which are indicative of material softening (decrease in post-yield flow stress) with increasing sample temperatures.

Here, we present a detailed protocol of a new approach for conducting elevated temperature reverse normal plate impact, and combined pressure-and-shear plate impact. The approach involves the use of a breech-end resistive coil heater to heat a sample held at the front-end of a heat-resistant sabot to the desired temperature.

采用臀端穿甲弹加热系统进行高温常压联合压力-剪切板冲击试验

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

结构转换的原位和原位研究方法: 金属玻璃结晶的实例

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

The Role of Fabric in Frictional Properties of Phyllosilicate-Rich Tectonic Faults

Many rock deformation experiments used to characterize the frictional properties of tectonic faults are performed on powdered fault rocks or on bare rock surfaces. These experiments have been fundamental to document the frictional properties of granular mineral phases and provide evidence for crustal faults characterized by high friction. However, they cannot entirely capture the frictional properties of faults rich in phyllosilicates.
Numerous studies of natural faults have documented fluid-assisted reaction softening promoting the replacement of strong minerals with phyllosilicates that are distributed into continuous foliations. To study how these foliated fabrics influence the frictional properties of faults we have: 1) collected foliated phyllosilicate-rich rocks from natural faults; 2) cut the fault rock samples to obtain solid wafers 0.8-1.2 cm thick and 5 cm x 5 cm in area with the foliation parallel to the 5x5cm face of the wafer; 3) performed friction tests on both solid wafers sheared in their in situ geometry and powders, obtained by crushing and sieving and therefore disrupting the foliation of the same samples; 4) recovered the samples for microstructural studies from the post experiment rock samples; and 5) performed microstructural analyses via optical microscopy, scanning and transmission electron microscopy. 
Mechanical data show that the solid samples with well-developed foliation show significantly lower friction in comparison to their powdered equivalents. Micro- and nano-structural studies demonstrate that low friction results from sliding along the foliation surfaces composed of phyllosilicates. When the same rocks are powdered, frictional strength is high, because sliding is accommodated by fracturing, grain rotation, translation and associated dilation. Friction tests indicate that foliated fault rocks may have low friction even when phyllosilicates constitute only a small percentage of the total rock volume, implying that a significant number of crustal faults are weak.

Friction of phyllosilicates-rich faults sheared in their in situ geometry is significantly lower than friction of their powdered equivalents.

织物在富含植物硅酸盐构造断层摩擦特性中的作用

Many rock deformation experiments used to characterize the frictional properties of tectonic faults are performed on powdered fault rocks or on bare rock ...

Full-field Strain Measurements for Microstructurally Small Fatigue Crack Propagation Using Digital Image Correlation Method

A novel measurement approach is used to reveal the cumulative deformation field at a sub-grain level and to study the influence of microstructure on the growth of microstructurally small fatigue cracks. The proposed strain field analysis methodology is based on the use of a unique pattering technique with a characteristic speckle size of approximately 10 &#181;m. The developed methodology is applied to study the small fatigue crack behavior in body centered cubic (bcc) Fe-Cr ferritic stainless steel with a relatively large grain size allowing a high spatial measurement accuracy at the sub-grain level. This methodology allows the measurement of small fatigue crack growth retardation events and associated intermittent shear strain localization zones ahead of the crack tip. In addition, this can be correlated with the grain orientation and size. Thus, the developed methodology can provide a deeper fundamental understanding of the small fatigue crack growth behavior, required for the development of robust theoretical models for the small fatigue crack&#160;propagation in polycrystalline materials.

Microstructurally small fatigue crack growth behavior is investigated using a novel methodological approach combining crack growth rate measurement and strain-field analysis to reveal the cumulative deformation field at sub-grain level.

基于数字图像相关的微结构小疲劳裂纹扩展的全场应变测量

A novel measurement approach is used to reveal the cumulative deformation field at a sub-grain level and to study the influence of microstructure on the ...

Performing Microscope-Mounted Y-Shaped Cutting Tests

Y-shaped cutting has recently been shown to be a promising method by which to understand the threshold length scale and failure energy of a material, as well as its failure response in the presence of excess deformation energy. The experimental apparatus used in these studies was vertically oriented and required cumbersome steps to adjust the angle between the Y-shaped legs. The vertical orientation prohibits visualization in standard optical microscopes. This protocol presents a Y-shaped cutting apparatus that mounts horizontally over an existing inverted microscope stage, can be adjusted in three dimensions (X-Y-Z) to fall within the objective&#39;s field of view, and allows easy modification of the angle between the legs. The latter two features are new for this experimental technique. The presented apparatus measures the cutting force within 1 mN accuracy. When testing polydimethylsiloxane (PDMS), the reference material for this technique, a cutting energy of 132.96 J/m2 was measured (32&#176; leg angle, 75 g preload) and found to fall within the error of previous measurements taken with a vertical setup (132.9 J/m2 &#177; 3.4 J/m2). The approach applies to soft synthetic materials, tissues, or bio-membranes and may provide new insights into their behavior during failure. The list of parts, CAD files, and detailed instructions in this work provide a roadmap for the easy implementation of this powerful technique.

Y-shaped cutting measures fracture-relevant length scales and energies in soft materials. Previous apparatuses were designed for benchtop measurements. This protocol describes the fabrication and use of an apparatus that orients the setup horizontally and provides the fine positioning capabilities necessary for in situ viewing, plus failure quantification, via an optical microscope.

执行显微镜安装的Y形切割测试

Y-shaped cutting has recently been shown to be a promising method by which to understand the threshold length scale and failure energy of a material, as ...