The authors have no acknowledgements.

1.实验用较粗的颗粒或等于700微米<ol><li>实验装置的制备<ol><li>卸下套筒和解除真空室的顶盖。放置由在真空室中的期望的壁材料的底板。打开真空室侧身的下部在板小心地用手滑动。 </li><li>地方恰好与在底板的中心镊子被检查的颗粒中的一种。事后调整照相机与三角架的高度以这样的方式，该底板是在视场的最低季度和集中在颗粒上。 </li><li>使用镊子除去粒子。 </li></ol></li><li>实验步骤<ol><li>调整颗粒室的高度在到达颗粒的期望的冲击速度的方式。使用刻度上附连到保持板作为高度的指示棍。关闭与颗粒室吸移管通过向下推，使吸移管的圆周接触腔室的钻头孔的边缘的尖端。打开套筒并解除真空室的顶盖。 </li><li>把一个单一的球面用镊子粒子室中。球体可以是固体或（如在Louge 等人 14）液体填充的，这取决于应分析什么样颗粒。然而，在这项工作中仅固体颗粒被检查。放置在真空室（气缸）的下部顶盖和连接顶盖和真空室与套筒的下部。 </li><li>疏散用真空泵腔室，直到达到0.1毫巴（或任何其它期望的值）的电平。测量用真空计的压力。关闭阀在真空室的侧面和关闭真空泵。在真空条件下工作时佩戴护目镜。 </li><li>套用万fps的帧速率和调整相机设置（断定离子/缩放），以获得528点¯x396像素的分辨率。启动高速摄像机的记录和打开粒子腔的孔释放的粒子。同时拉并转动连接到吸移管，以避免粘滑问题的前端的棒由于棒和密封环之间的高摩擦力。 </li><li>冲击后直接停止照相机的记录，因为只有图像的有限数量可以保存并超过此限制，当第一那些被覆盖。切电影周围的在屏幕的影响的瞬间并保存在存储卡上。 </li><li>重复实验十次获得统计显著的效果。结果是统计学显著如果经过十次重复的平均值已不改变（这可能是取决于样品或其它颗粒形状的均匀性的其他材料不同）。 </li></ol></li><li>评估程序<ol><li>在知道校准软件的颗粒或者使用在步骤1.2.4取得的视频的一帧，以获得像素和距离之间的转换另一对象的n个大小。使用水平直径，因为它是不模糊的，由于粒子的运动。 <ol><li>算水平直径的像素的数量，然后通过像素的数量除以已知距离来获得的转换系数&#39;每像素距离"。校准过程的的图象示于图4。 </li></ol></li><li>设置运动的球体上的十帧之前和冲击来计算冲击速度前一帧的顶端的参考点; 图5表示运动的两个参考点。与来自步骤1.3.1的转换系数，使用两点之间的像素的数目，以获得行驶距离。由过去的时间（帧和时间步长的数量的产品）分的距离，以获得冲击速度。 </li><li>设置的参考点在球体的一帧的后顶部和冲击后十帧运动，计算回弹速度。类似确定回弹速度步骤1.3.2。 </li><li>计算COR为冲击速度回弹速度比。 </li><li>重复步骤1.3.1-1.3.4为所有录制的跌落测试视频的评价。 </li></ol></li></ol> 2.实验用更细的粉末或等于400微米<ol><li>实验装置的制备<ol><li>卸下套筒和解除真空室的顶盖。放置由在真空室中的期望的壁材料的底板。打开真空室侧身的下部在板小心地用手滑动。 </li><li>放置一个适当的参考对象，如与在利用镊子底板的中心的已知大小的颗粒。之后使用三脚架调整相机的高度以这样的方式，该底板是在最低的四分之一视野和重点参考对象。 </li><li>记录时，它躺在底板用完全相同的设置，如下面的实验参考对象的一个​​简短的视频。 </li><li>用镊子取下参考对象。 </li></ol></li><li>实验步骤<ol><li>调整颗粒室的高度在到达颗粒的期望的冲击速度的方式。使用刻度上附连到保持板作为高度的指示棍。用吸管的尖端向下推，使吸移管的圆周接触腔室的钻孔的边缘关闭粒子室中。打开套筒并解除真空室的顶盖。 </li><li>把50〜100球体的粒子室中。要引导球入颗粒室，首先将它们存放在一张折叠片。使用折叠的纸张作为槽到颗粒滑入腔室。对于T顶盖他真空室（气缸）的下部，并连接顶盖和真空室与套筒的下部。 </li><li>疏散用真空泵腔室，直到达到0.1毫巴（或任何其它期望的值）的电平。测量用真空计的压力。关闭阀在真空室的侧面和关闭真空泵。在真空条件下工作时佩戴护目镜。 </li><li>启动高速摄像机10,000 FPS和528点¯x396像素的分辨率的记录，并打开粒子室的孔解放颗粒。同时拉并转动连接到吸移管，以避免粘滑问题的前端的棒由于棒和密封环之间的高摩擦力。拉非常缓慢，以防止所有的粒子滴在同一时间。 </li><li>第一粒子的影响后停止相机5的记录为6秒，因为只有图像的有限数量可以保存和冷杉超过此限制时，为ST的人都将被覆盖。切电影屏幕中这样的方式至少10清楚地集中颗粒的影响是明显的，并将其保存在存储卡上。 </li></ol></li><li>评估程序<ol><li>与来自步骤2.1.3的视频的参考对象的已知尺寸校准软件，以获得像素和距离之间的转换。算基准对象的大小的像素的数量，然后通过像素的数量除以已知距离来获得的转换系数&#39;每像素距离"。 </li><li>在撞击前的第一个重点明确球体在视频前十帧的顶部和一帧设置动作的基准点来计算的冲击速度。类似计算冲击速度与转换系数从步骤2.3.1一起步骤1.3.2。 </li><li>设置运动的基准点上的第一个重点明确球体一帧的顶部之后和十帧船尾呃的影响来计算回弹速度。类似计算回弹速度步骤2.3.2。 </li><li>计算COR为冲击速度回弹速度比。 </li><li>对另外九个重点明确球体的影响评估重复步骤2.3.2-2.3.3。 </li></ol></li></ol>

<ol>
	<li>Ennis, B. J., Green, J., Davies, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+legacy+of+neglect.">The legacy of neglect.</a> U.S. Chem. Eng. Prog. 90 (4), 32-43 (1994).</li><li>Nedderman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statics and Kinematics of Granular Materials. , (1992).</li><li>Seifried, R., Schiehlen, W., Eberhard, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Numerical+and+experimental+evaluation+of+the+coefficient+of+restitution+for+repeated+impacts.">Numerical and experimental evaluation of the coefficient of restitution for repeated impacts.</a> Int. J. Impact Eng. 32, 508-524 (2005).</li><li>Thornton, C., Ning, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+theoretical+model+for+the+stick/bounce+behaviour+of+adhesive,+elastic-plastic+spheres.">A theoretical model for the stick/bounce behaviour of adhesive, elastic-plastic spheres.</a> Powder Technol. 99, 154-162 (1998).</li><li>Antonyuk, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Energy+absorption+during+compression+and+impact+of+dry+elastic-plastic+spherical+granules.">Energy absorption during compression and impact of dry elastic-plastic spherical granules.</a> Granul. Matter. 12, 15-47 (2010).</li><li>G&#252;ttler, C., Hei&#223;elmann, D., Blum, J., Krijt, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Normal+Collisions+of+Spheres:+A+Literature+Survey+on+Available+Experiments.">Normal Collisions of Spheres: A Literature Survey on Available Experiments.</a> arXIV. , (2012).</li><li>Bharadwaj, R., Smith, C., Hancock, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+coefficient+of+restitution+of+some+pharmaceutical+tablets/compacts.">The coefficient of restitution of some pharmaceutical tablets/compacts.</a> Int. J. Pharm. 402, 50-56 (2010).</li><li>Fu, J., Adams, M. J., Reynolds, G. K., Salman, A. D., Hounslowa, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+deformation+and+rebound+of+wet+granules.">Impact deformation and rebound of wet granules.</a> Powder Technol. 140, 248-257 (2004).</li><li>Sommerfeld, M., Huber, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+analysis+and+modelling+of+particle-wall+collisions.">Experimental analysis and modelling of particle-wall collisions.</a> Int. J. Multiphas. Flow. 25, 1457-1489 (1999).</li><li>Foerster, S. F., Louge, M. Y., Chang, H., Allia, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+the+collision+properties+of+small+spheres.">Measurements of the collision properties of small spheres.</a> Phys. Fluids. 6 (3), 1108-1115 (1994).</li><li>Lorenz, A., Tuozzolo, C., Louge, M. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+Impact+Properties+of+Small,+Nearly+Spherical+Particles.">Measurements of Impact Properties of Small, Nearly Spherical Particles.</a> Exp. Mech. 37 (3), 292-298 (1997).</li><li>Fu, J., Adams, M. J., Reynolds, G. K., Salman, A. D., Hounslowa, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+deformation+and+rebound+of+wet+granules.">Impact deformation and rebound of wet granules.</a> Powder Technol. 140, 248-257 (2004).</li><li>Wong, C. X., Daniel, M. C., Rongong, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Energy+dissipation+prediction+of+particle+dampers.">Energy dissipation prediction of particle dampers.</a> J. Sound Vib. 319, 91-118 (2009).</li><li>Louge, M. Y., Tuozzolo, C., Lorenz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+binary+impacts+of+small+liquid-filled+shells.">On binary impacts of small liquid-filled shells.</a> Phys. Fluids. 9, 3670-3677 (1997).</li></ol>

The authors have nothing to disclose.

To validate the functionality of the experimental setup in general, tests with similar material combinations as in other established setups (Antonyuk et al.5 and Wong et al.13) were performed. Since very similar results were obtained, the general procedure seems to work. Nevertheless, caution has to be taken towards the procedure and the analysis and further improvements are necessary.
The main limitation of the experimental setup is the quality of the videos. On the one hand, the images can be blurred because the particle is not exactly in the visual field of the camera. Here, the particle impacts not perfectly centric due to instability of the particle chamber during particle release. On the other hand, the resolution is responsible for the accuracy of determining the velocities, because the number of pixels limits the number of nuances. Therefore it is necessary to test different frame rates since the higher the frame rate the lower the resolution. To avoid calibration problems of the conversion between pixels and distances as in the experiments with 700 &#181;m particles, a standardized calibration with a video of a reference object with an adequate, known size should be taken with exactly the same camera settings as in the experiments. A recommendation for such an object could be a ruler placed at the impact position of the particle. This object would also be preferable for experiments with larger particles since larger reference distances reduce the calibration error.
To minimize the instability of the particle chamber during the release, the setup will be automated and the stick connected to the tip of the pipette will be guided by bushings. A wire is connected to the top of the stick and then guided over one pulley aligned above the stick to another pulley connected to a motor that pulls the wire. Therefore also a frame is constructed. The future setup is shown in Figure 8.
To be able to release powders inferior to 20 &#181;m several improvements will be made. For these fine particles adhesive forces much higher than the gravitational ones occur so that particles stick together and to walls. Therefore a vibration of the particle chamber and the needle could be a means to overcome the adhesive forces and make the particle leave the chamber. Another difficulty is that these particles are too small to be visible during the experiment. Therefore a sensor is required that indicates the instant when the particle falls because the high speed camera can only save a limited amount of pictures and overwrites the beginning of the video when this is exceeded. Moreover, a microscope objective will be mounted on the camera to be able to analyze particles down to 10 &#181;m.
Also the particle-particle contact needs to be examined to be able to characterize all collisions in DEM simulation. One possibility to evaluate this could be to place many particles on the baseplate and to carry out the drop experiment for an impact on a particle then. Another idea to analyze the particle-particle contact would be to modify this experimental setup and apply a similar technique to the one of Foerster et al.10 and Lorenz et al.11. In their experiments two particles were liberated with different initial heights and collide before the impact on the ground. Afterwards the results for the particle-particle and the particle-wall contact need to be compared.

粉末和颗粒到处都是我们身边。没有他们的生活是在现代社会中是不可能的。它们出现在食品和饮料，谷物或甚至面粉，糖，咖啡和可可。他们需要像碳粉激光打印机日常使用的对象。还塑料工业也不是没有它们可以想象，因为塑料在粒状形式运输它被熔化并赋予新的形状之前。之后的价值恩尼斯等 1至少40％加入美利坚合众国的居民消费价格指数化工行业（农业，食品，医药，矿产，弹药）连接到颗粒技术。 Nedderman 2甚至指出，产品和最小的原料的75％的约50％（重量）是在化学工业中的粒状固体。他还宣布，有关于出现颗粒状物料的储存和运输的许多问题。其中之一是在运输和handli期间NG多次碰撞发生。为了分析，描述和预测颗粒系统的行为，离散元法（DEM）模拟可以执行。对于该微粒系统的碰撞行为的这些模拟的知识是必要的。描述的DEM模拟这种行为的参数是归还（COR）的具有在实验确定的系数。 的COR是一个数字，如由SEIFRIED 等人描述的撞击期间表征动能的损失。3。他们解释说，这是由塑性变形，波传播和粘弹性现象造成的。桑顿和宁4还提到，一些能源可能受到因界面粘结工作消散。的COR取决于冲击速度，材料特性，颗粒大小，形状，粗糙度，水分含量，粘合性能和温度如在Antonyuk 等人说明。5。对于completelŸ弹性影响的所有吸收的能量碰撞后使接触合作伙伴之间的相对速度是之前和冲击后返回相等。这导致E = 1的COR期间完全塑性影响所有的初始动能被吸收和接触伙伴粘在一起从而导致E的COR = 0。此外，Güttler 等 6说明有两个类型的碰撞。一方面，有两个球体其也被称为颗粒与颗粒接触之间的碰撞。另一方面，有一个球体和一个板，其也被称为颗粒 - 壁接触之间的碰撞。与用于COR数据和类似的系数其它材料性质的摩擦，密度，泊松比和剪切模量的DEM模拟可以被执行以确定通过巴拉德瓦等 7所解释的粒子的碰撞后的速度和方向。由于笑WN在Antonyuk 等人 5，COR可以与回弹速度的比率来计算冲击速度。 因此，对于自由下落测试，以检查颗粒的直径为0.1mm至4mm的粒子壁接触的实验装置构成。相比加速实验中Fu等 8和索末菲和胡伯9的自由下落实验的优点在于，转动可能被淘汰。因此，可避免其影响COR旋转和平移动能之间的转移。非球面颗粒需要被标记为在Foerster的等 10或洛伦茨等人 11采取旋转考虑。作为COR取决于冲击速度，在实验中的冲击速度有以匹配实际运输和装卸过程中的那些。在大气压下自由落体实验中，冲击速度是有限受阻力，具有降低的粒度的影响越来越大。为了克服这个缺点，实验设置在真空条件下工作的。第二个挑战是因为那么有可能表征了影响COR预先，例如表面粗糙度和粘附的所有属性下降只是一个单一的粒子。有了这些知识，该COR可以根据颗粒的性质来决定。为此，新版本机制的发展。另一个问题是，其直径逊色于400微米的粉末的粘附力​​。因此，干式和环境温度的环境是必要的，以克服粘附力。 实验装置由几部分组成。现有的实验设置的外部视图中示出在图1中。首先，有真空室是由玻璃制成的。它是由一个下部（气缸）的，一个顶盖，一个密封环和套筒连接部分。下部具有用于与真空泵和真空计连接的两个开口。顶盖有四个孔。其中两个是必要的如下所述的释放机构的枝以及两个可用于实验的进一步的改进。所有这些开口可以与密封环和真空条件下工作时，螺旋盖被关闭。 此外，一个新的释放机构被自使用真空喷嘴的开发为在文献中记载了许多其它的实验（例如Foerster的等 10，洛伦茨等人 11，Fu等 12或Wong等人 13）是不可能在真空环境。该机构由与由板保持的锥形钻孔的圆筒形腔室来实现。这被连接到装配在真空室的顶盖的密封环中的一个，并保证了variab的调整棒勒初始高度自由下落实验。的比例可绘制在棍子测量高度。粒子室的关闭由被再次连接到棒的吸移管的圆锥尖来实现。新的释放机构可在图2中可以看出，并工作如下所述:在初始状态，使末端的圆周接触腔室的钻孔的边缘枪头被推下。该腔室是封闭的枪头使得没有空间的粒子通过该孔离开该室。为了释放颗粒，棒向上非常缓慢一起与连接到它的前端拉动。作为尖端的直径越来越小其圆周和钻孔的边缘之间的间隙产生，通过该粒子可以离开该室。虽然人们可能期望粒子的新开发的释放机制为颗粒可以&#39;滚&#39;出湛的旋转误码率，一个不同的行为显示在实验。 图3示出了非球面微粒的从50帧之前在25帧的步骤的影响后的影响，以50帧。从粒子的形状没有旋转的影响（1-3），而事后它明显旋转（4-5）之前是可见的。因此，声称非旋转释放正在与本次发布机制。 实验装置的另一部件是在底板上。事实上，有三种不同类型的由不同的材料的底板的。一个是由不锈钢制成，铝的第二和聚氯乙烯的第三（PVC）。这些底板代表例如在反应器和管工艺工程中经常用到的材料。 要确定影响速度和回弹速度，使用高速摄像机10,000 FPS和528点¯x396像素的分辨率。选择这种构总是有附近的冲击一张图片，也分辨率仍是令人满意的。相机连接到一个屏幕，示出了在瞬间视频它们被记录时。这是必要的，因为高速摄像机只能保存的图片数量有限，并超过这一数额时，将覆盖视频的开头。此外，需要高速照相机的视场的照明强光源。照明均匀度的技术图纸纸张被粘在真空室传播的光的背面。 最后，两阶段旋转叶片泵被用于建立0.1毫巴的真空和真空计测量的真空，以保证恒定的环境条件。 对于不同粒径（0.1-0.2，0.2-0.3，0.3-0.4，0.700，1.588，2.381，2.780，3.680和4.000毫米）所提出的在这里工作的玻璃珠被使用。珠粒是由碱石灰玻璃和是球形具有相当光滑的表面。

<table><tbody><tr><td>High-speed camera Olympus i-SPEED 3</td><td>Olympus</td><td></td><td>High-speed camera to capture the particle impact</td></tr><tr><td>Screen Olympus i-SPEED CDU</td><td>Olympus</td><td></td><td>Screen to work with the high-speed camera</td></tr><tr><td>Light source Olympus ILP-2</td><td>Olympus</td><td></td><td>Light source necessary for taking videos at high frame rates</td></tr><tr><td>Vacuum pump Alcatel Pascale 2005 D</td><td>Alcatel</td><td></td><td>Vacuum pump to generate the vacuum during the experiments</td></tr><tr><td>Vacuum gauge Alcatel CFA 212</td><td>Alcatel</td><td></td><td>Vacuum gauge to measure the vacuum level</td></tr><tr><td>i-SPEED Software Suite (Control version)</td><td>Olympus</td><td></td><td>Software to evaluate the videos</td></tr><tr><td>Glass beads</td><td>Sigmund Lindner GmbH</td><td></td><td>SiLibeads Type P (0.700, 1.588, 2.381, 2.780, 3.680, 4.000 mm)&lt;br/&gt; SiLibeads Type S (0.1-0.2, 0.2-0.3, 0.3-0.4&amp;nbsp;mm)&lt;br/&gt; http://www.sigmund-lindner.com (see supplier&#039;s website for more information about the glass properties)</td></tr><tr><td>Safety goggles</td><td></td><td></td><td></td></tr></tbody></table>

development of an experimental setup for the measurement of the coefficient of restitution under vacuum conditions

离散元方法被用于微粒系统的仿真来描述和分析它们，以预测和事后优化其为一个过程的单一阶段或甚至整个进程的行为。用于模拟与存在颗粒 - 颗粒和颗粒壁的接触，需要恢复系数的值。它可以通过实验确定。恢复系数取决于几个参数，如冲击速度。尤其是对细颗粒的冲击速度取决于空气压力和大气压力下，不能达到高的冲击速度。对于这一点，对于在真空条件下自由下落测试一个新的实验装置显影。恢复系数与它们通过高速摄像机检测出的冲击和回弹速度决定。到不妨碍视图，真空室由玻璃制成。又一个新的释放机制回落真空下一个单一的粒子条件构造。由于是，所述颗粒的所有属性可以预先表征。

对于一个直径为100微米至4.0毫米分析玻璃颗粒从200毫米的初始高度上一个不锈钢基板的厚度为20毫米丢弃。 图6示出了用于根据粒径为大气压力和真空的COR的平均值，以及最大值和最小值。的COR的平均值被发现是大约E = 0.9的颗粒大于或等于700微米的独立的空气压力的。 对于直径的颗粒小于400微米的COR保持随e的值= 0.9在真空条件下几乎不变。在大气压力下的COR以减小粒径减小。其原因可能是，在粒子的前部的空气中的自由下落的wh期间被压缩ICH结果在那种阻尼碰撞，吸收动能的衬垫的，并且由于其导致较低的COR。在这两种情况下的偏差比粗颗粒更高。为对此的解释可能是，微粒只有在视频几个像素的大小。因此，在一个模糊图像，由于像素的选择的错误非常激烈。 为根据不同的粒径为大气压力和真空的冲击速度的结果示于图7中;对于冲击速度的平均值，最大和最小显示。冲击速度的平均值与大约V I = 2毫秒-1评价大于700微米的独立的空气压力的颗粒。异常出现的700微米的粒径，其中冲击速度是显著低真空条件下即使在大气压下稍多。要减小粒径在大气压下减少的冲击速度预期。与此相反的是，冲击速度应保持在真空条件下是相同的。具有的评价方法，可以看出，对于具有的直径为700微米的校准像素和距离之间的转换粒子细看是，对于较粗的颗粒的不同。每毫米像素的比率是显著较高，这导致在低的速度。一种用于假校准原因可能是，相机不能够正确地识别该细颗粒的形状。使用相同的标准的校准作为粗粒子的冲击速度仍大致相同的范围和异常值可以被消除。 对于直径逊色于400微米的冲击速度减小粉末显著在常压下减少的粒径。空气摩擦力和重力，也沉降速度的平衡，是较早对细颗粒到达。在对比的是，在真空条件下，冲击速度是几乎恒定也为粉末。这证明一个无限加速粒子的理论，当没有空气，可能导致由于该力的平衡被从未达到一个阻力和。它还显示的真空条件的必要性，因此，也对新开发的释放机构用的细颗粒达到高的冲击速度。在这些实验中只冲击速度的轻微下降是可识别的，可以通过以下事实，只有0.1毫巴的真空达到这不是一个完美的真空进行说明。用于与0.113毫米的中值直径的颗粒的高得多的发生偏差作为误差的影响，由于像素的一个BL选择urred图片是较低的速度更高。 <img alt="图1" src="/files/ftp_upload/53299/53299fig1.jpg" /> 图1.在真空室的外观图。该图表示从侧面真空室。人们可以看到，其两个开口的下部用于与真空泵和真空计连接。此外，与密封环和螺丝帽四个开口顶盖可见。密封环是下部和上部之间。套筒在这张照片已被删除。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/53299/53299fig2.jpg" /> 图2.释放机制，颗粒室和吸管的一角。这个数字说明了新ðeveloped释放装置真空实验。首先，板保持圆筒形腔室的锥形钻孔中可以看出。此外，两根棍子一个变量初始高度的调整，到吸管的锥尖的连接介绍。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/53299/53299fig3.jpg" /> 图3.非旋转的释放。该图表示从一系列的非球面微粒的照片50（1）和25帧（2）之前的影响，以及在冲击（3），并在25（4）和50 （5）的影响后帧。颗粒上的冲击的相同形状揭示非转动释放。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig3large.jpg" target="_blank">请CLI</a>这里完蛋查看此图的放大版本。 <img alt="图4" src="/files/ftp_upload/53299/53299fig4.jpg" /> 图4.该软件的校准。该图表示从记录的自由落体实验的一个视频的粒子。红线代表粒子的大小和拥抱必要计算转换系数的像素数。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图5" src="/files/ftp_upload/53299/53299fig5.jpg" /> 图5.运动的参考点。该图呈现在记录自由落体实验的视频粒子。两个红色十字说明关于在各个帧中的球体的顶部运动的两个参考点:上部上E在冲击前十帧，并在之前的冲击一帧的较低的一个。两点之间的距离来计算粒子的撞击速度。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig5large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图6" src="/files/ftp_upload/53299/53299fig6.jpg" /> 图6.对COR粒径和空气压力的影响。该图示出的平均值以及最大值与依赖于粒径的误差棒为COR最小值。蓝色菱形表示在大气压下实验结果而橙色圆圈显示为在真空条件下的实验结果。玻璃颗粒从200毫米的初始高度下落到不锈钢底板。每个数据点代表10 repetiti的平均值实验的附件。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig6large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图7" src="/files/ftp_upload/53299/53299fig7.jpg" /> 图7.粒径和气压的冲击速度的影响。该图表示了根据不同的粒度的影响的速度的平均值。此外由误差条示出的最大值和最小值介绍。填充的蓝色的钻石表明在大气压下实验结果而充满橙色圆圈显示在真空条件下的实验结果。空钻石和空圈说明由于校准问题离群值。在实验中的玻璃颗粒从200毫米的初始高度下落到不锈钢底板。每个数据点代表平均值的实验十重复。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig7large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图8" src="/files/ftp_upload/53299/53299fig8.jpg" /> 图8.未来的实验装置，图中描绘了未来的实验装置的释放期间以最小化颗粒腔的不稳定性。与由轴套导引棒，以及用于粘到电动机经由两个滑轮连接导线的自动化设置中示出。还显示框。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53299/53299fig8large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions at JoVE.com

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

恢复系数是描述碰撞时的动能的损失的参数。这里，在真空条件下自由下落设置被显影以能够确定归还参数的系数为在微米范围内的颗粒的高的冲击速度。

实验装置的研制归还系数在真空条件下测量

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

development-an-experimental-setup-for-measurement-coefficient

Nanyang Technological University

Research

Education

JoVE Journal

JoVE Core

Physics

Engineering

Unit 1

Linear Momentum, Impulse and Collisions

SCIENTISTS IN ACTION

8.1K 次观看.  University of Technology of Compiègne. 恢复系数是描述碰撞时的动能的损失的参数。这里，在真空条件下自由下落设置被显影以能够确定归还参数的系数为在微米范围内的颗粒的高的冲击速度。 

视频: Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids&#160;and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data.
The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.1&#160;Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.

This paper demonstrates the experimental procedure to measure terminal settling velocities of spherical particles in surfactant-based shear thinning viscoelastic fluids. Fluids over a wide range of rheological properties are prepared and settling velocities are measured for a range of particle sizes in unbounded fluids and fluids between parallel walls.

无约束和封闭表面活性剂中球形粒子沉降速度的实验测量 剪切变薄粘性流体

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic ...

科研

工程学

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

一个测试平台为聚合物的耐久性研究，并在同期Hygrothermo机械刺激纤维增强聚合物复合材料

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

使用超声波润滑实验一压电辅助摩擦试验机和光学轮廓

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various characteristic length scales can result in pressure fluctuations over a wide frequency range. This property of turbulence requires sensing devices to have sufficient sensitivity over a wide range of frequencies. Furthermore, the small characteristic length scales of turbulent structures require small sensing areas and the ability to place the sensors in very close proximity to each other. The complex geometries of the solid bodies, often including large surface curvatures or discontinuities, require the probe to have the ability to be set up in very limited spaces. The development of a remote microphone probe, which is inexpensive, consistent, and repeatable, is described in the present communication. It allows for the measurement of pressure fluctuations with high spatial resolution and dynamic response over a wide range of frequencies. The probe is small enough to be placed within the interior of typical wind tunnel models. The remote microphone probe includes a small, rigid, and hollow tube that penetrates the model surface to form the sensing area. This tube is connected to a standard microphone, at some distance away from the surface, using a "T" junction. An experimental method is introduced to determine the dynamic response of the remote microphone probe. In addition, an analytical method for determining the dynamic response is described. The analytical method can be applied in the design stage to determine the dimensions and properties of the RMP components.

Here, we present a protocol to measure, with high spatial resolution, the unsteady surface pressure in turbulent flows. This method demonstrates the construction of a remote microphone probe (RMP) and the determination of its frequency-dependent, complex transfer function. An analytical determination of the dynamic response is presented and validated.

非定常表面压力的使用远程麦克风探头测量

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various ...

How to Build a Vacuum Spring-transport Package for Spinning Rotor Gauges

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to 1.0 Pa. In this application, the SRGs are frequently transported to laboratories for calibration. Events can occur during transportation that change the rotor surface conditions, thus changing the calibration factor. To assure calibration stability, a spring-transport mechanism is often used to immobilize the rotor and keep it under vacuum during transport. It is also important to transport the spring-transport mechanism using packaging designed to minimize the risk of damage during shipping. In this manuscript, a detailed description is given on how to build a robust spring-transport mechanism and shipping container. Together these form a spring-transport package. The spring-transport package design was tested using drop-tests and the performance was found to be excellent. The present spring-transport mechanism design keeps the rotor immobilized when experiencing shocks of several hundred g (g = 9.8 m/sec2 and is the acceleration due to gravity), while the shipping container assures that the mechanism will not experience shocks greater than about 100 g during common shipping mishaps (as defined by industry standards).

Here we describe how to build a robust spring-transport mechanism for a spinning rotor gauge. This device securely immobilizes the rotor and keeps it under vacuum during transportation. We also describe packaging that minimizes the risk of damage during transport. Tests show our design works for typical shocks during transport.

如何建立一个真空Spring的运输包装为纺转子规

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to ...

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10&#8722;11 Pa m3 sec&#8722;1 m&#8722;2) can be routinely measured using relatively small samples.

A protocol for the measurement of outgassing rates of hydrogen from ordinary steel vacuum chambers using the rate-of-pressure rise method is presented.

钢的出气率的测量

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

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 ...

环境科学

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a standard fluid dynamic diagnostic, particle image velocimetry (PIV), to measure: i) velocities of individual particles (grains), extant on short, grain-collision time-scales, ii) velocities of systems of particles, on both short collision-time- and long, continuum-flow-time-scales, iii) collective hydrodynamic modes known to exist in dense molecular fluids, and iv) short- and long-time-scale velocity autocorrelation functions, central to understanding particle-scale dynamics in strongly interacting, dense fluid systems. The basic system is composed of an imaging system, light source, vibrational sensors, vibrational system with a known media, and PIV and analysis software. Required experimental measurements and an outline of the theoretical tools needed when using the analog technique to study molecular-scale hydrodynamic processes are highlighted. The proposed technique provides a relatively straightforward alternative to photonic and neutron beam scattering methods traditionally used in molecular hydrodynamic studies.

An experimentally accessible analog method for studying molecular hydrodynamic processes in dense fluids is presented. The technique uses particle image velocimetry of vibrated, high-restitution grain piles and allows direct, macroscopic observation of dynamical processes known and predicted to exist in strongly interacting, high density gases and liquids.

一种研究稠密气体和液体分子流体力学过程的模拟宏观技术

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

A Friction Testing-Bioreactor Device for Study of Synovial Joint Biomechanics, Mechanobiology, and Physical Regulation

In primary osteoarthritis (OA), normal 'wear and tear' associated with aging inhibits the ability of cartilage to sustain its load-bearing and lubrication functions, fostering a deleterious physical environment. The frictional interactions of articular cartilage and synovium may influence joint homeostasis through tissue level wear and cellular mechanotransduction. To study these mechanical and mechanobiological processes, a device capable of replicating the motion of the joint is described. The friction testing device controls the delivery of reciprocal translating motion and normal load to two contacting biological counterfaces. This study adopts a synovium-on-cartilage configuration, and friction coefficient measurements are presented for tests performed in a phosphate-buffered saline (PBS) or synovial fluid (SF) bath. The testing was performed for a range of contact stresses, highlighting the lubricating properties of SF under high loads. This friction testing device can be used as a biomimetic bioreactor for studying the physical regulation of living joint tissues in response to applied physiologic loading associated with diarthrodial joint articulation.

The present protocol describes a friction testing device that applies simultaneous reciprocal sliding and normal load to two contacting biological counterfaces.

一种摩擦试验-用于研究滑膜关节生物力学、机械生物学和物理调节的生物反应器装置

In primary osteoarthritis (OA), normal 'wear and tear' associated with aging inhibits the ability of cartilage to sustain its load-bearing and lubrication ...

生物工程

Experimental Multiscale Methodology for Predicting Material Fouling Resistance

The buildup of fouling deposits in energy systems degrades their ability to transfer heat, reducing efficiency and causing operational issues such as localized corrosion. Each application presents its own challenges. In nuclear power generation, the buildup of CRUD (Chalk River Unidentified Deposits) induces unique, negative effects ranging from reduced heat transfer, to axial power shifting, to CRUD-induced localized corrosion (CILC), the last of which can cause sudden fuel failure. Knowledge of why CRUD forms and how to prevent its adhesion to nuclear fuel rods represents a major step towards eliminating it. This paper demonstrates a methodology to ascertain which materials may resist CRUD adhesion, thereby preventing its initiation and growth. It presents experiments targeted at multiple length scales: pool boiling (macroscale), which simulates CRUD initiation processes in a nuclear reactor, and atomic force microscope (AFM) force spectroscopy (microscale), which yields quantitative measurements of the adhesion between CRUD constituents and candidate CRUD-resistant materials. Early data from both sets of experiments show some correlation, suggesting that AFM force spectroscopy (AFM-FS) may be used to pre-screen materials for fouling resistance. So far, it appears that CRUD constituents adhere well to oxides, while carbides show both greatly reduced adhesion and no adherent CRUD in pool boiling experiments. The relationship between the AFM-FS measurements and the growth of CRUD in the pool boiling experiments may provide insight into the possible factors affecting fouling in nuclear reactors, eventually leading to its elimination.

Fouling, or corrosion product deposition, plagues numerous fields of energy production. At its core is adhesion between dissimilar materials. Understanding and controlling adhesion could reduce or eliminate fouling. This paper demonstrates pool boiling experiments (macroscale) and atomic force microscope force-spectroscopy measurements (microscale), which when in agreement, indicate fouling-resistance.

The buildup of fouling deposits in energy systems degrades their ability to transfer heat, reducing efficiency and causing operational issues such as ...

实验装置的研制归还系数在真空条件下测量

摘要

探索更多视频

此视频中的章节

无约束和封闭表面活性剂中球形粒子沉降速度的实验测量剪切变薄粘性流体

一个测试平台为聚合物的耐久性研究，并在同期Hygrothermo机械刺激纤维增强聚合物复合材料

使用超声波润滑实验一压电辅助摩擦试验机和光学轮廓

非定常表面压力的使用远程麦克风探头测量

如何建立一个真空Spring的运输包装为纺转子规

钢的出气率的测量

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

一种研究稠密气体和液体分子流体力学过程的模拟宏观技术

一种摩擦试验-用于研究滑膜关节生物力学、机械生物学和物理调节的生物反应器装置

Experimental Multiscale Methodology for Predicting Material Fouling Resistance

实验装置的研制归还系数在真空条件下测量

摘要

探索更多视频

此视频中的章节

无约束和封闭表面活性剂中球形粒子沉降速度的实验测量 剪切变薄粘性流体

一个测试平台为聚合物的耐久性研究，并在同期Hygrothermo机械刺激纤维增强聚合物复合材料

使用超声波润滑实验一压电辅助摩擦试验机和光学轮廓

非定常表面压力的使用远程麦克风探头测量

如何建立一个真空Spring的运输包装为纺转子规

钢的出气率的测量

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

一种研究稠密气体和液体分子流体力学过程的模拟宏观技术

一种摩擦试验-用于研究滑膜关节生物力学、机械生物学和物理调节的生物反应器装置

Experimental Multiscale Methodology for Predicting Material Fouling Resistance

无约束和封闭表面活性剂中球形粒子沉降速度的实验测量剪切变薄粘性流体

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