Dynamics of Brittle Fracture

[01:10 . 30]玛德：我们将在单晶硅上进行研究，以找出快速运行裂纹的速度如何取决于加载大小、加载方式、晶体平面、取向和温度。这些研究将包括首次在低于100K的温度下对晶体断裂的研究。我们还将提供裂缝后留下的结构的仔细测量，包括裂缝表面上和下面的结构。此外，我们将研究聚合物、玻璃、离子晶体和合金的脆性-韧性转变，并研究晶体和非晶态材料裂纹路径的规律。当飞机或桥梁发生故障时，罪魁祸首往往是断裂。裂缝在接近声速的固体结构中快速穿行，将它们撕成两半。与此同时，断裂是许多用于塑造材料的过程的基础，例如切割、打磨或抛光。因此，研究裂缝的第一个动机是保护工程结构，第二个动机是学习操纵和形成裂缝的新方法。我们一直在进行实验，以获得在精确控制条件下断裂如何进行的详细信息。我们的实验将在温度低于室温200摄氏度的单晶硅中进行。从这些实验中获得的信息将告诉我们物质的结构在原子尺度上是如何影响断裂的，并将检验那些声称能预测可能的原子效应的理论。随着硅实验的完成，我们将扩大我们的研究范围，以研究其他晶体和玻璃材料的裂纹运动。

0101030 Marder We will carry out studies in single crystal silicon to find how the speed of a rapidly running crack depends upon loading magnitude, loading mode, crystal plane, orientation, and temperature. The studies will include the first investigations of crystalline fracture at temperatures below 100K. We will also provide careful measurements of the structures left behind the cracks, both on and below the fracture surface. In addition, we will investigate the brittle-ductile transition for polymers, glasses, ionic crystals, and alloys, and study the laws governing crack paths in crystalline and amorphous materials.%%%When airplanes or bridges fail, the culprit is often fracture. Cracks race across solid structures near the speed of sound, ripping them in two. At the same time, fracture underlies many processes used to shape materials, such as cutting, sanding, or polishing. The first motivation to study fracture is therefore to protect engineering structures, and the second is to learn new ways to manipulate and form them. We have been constructing experiments to obtain detailed information on how fracture proceeds under precisely controlled conditions. Our experiments will be performed in single crystals of silicon at temperatures that are 200 degrees C below room temperature. The information from these experiments will tell us how the structure of matter at the atomic scale affects fracture, and will test theories claiming to make predictions about possible atomic effects. As the experiments in silicon are completed, we will broaden our studies to investigate crack motion in other crystalline and glassy materials.