High Performance Machining of Brittle Materials by Controlled Crack Propagation

由各种脆性材料制成的精密零件在医疗保健、生物医学、能源、光电子和汽车行业有着广泛的应用。高速加工脆性材料的一大挑战是获得高表面质量。在加工这些材料时遇到的一个主要问题是随机裂纹扩展到工件中，导致表面/亚表面裂纹，从而导致已加工零件的强度退化。现有的技术依赖于抛光，这是一个非常缓慢和昂贵的过程，以实现高表面质量。该奖项支持基础研究，为开发新的加工工艺提供必要的知识，以克服这一主要限制。新工艺将在不影响零件质量的情况下实现脆性材料的高效加工。这项研究的结果将为美国带来经济和社会效益。这项研究涉及多个学科，包括制造、激光和光学、断裂力学和生物材料。多学科性质将有助于招募代表性不足的群体进行研究，从而对工程教育产生积极影响。这项研究的目的是双重的。首先，将建立飞秒激光参数(例如，脉冲能量、光斑大小、脉冲数量)与微裂纹几何形状(例如，裂纹长度、裂纹方向、裂纹间隙)之间的关系。这一目标将通过执行激光微加工实验来实现，以在工件材料内部产生种子裂纹。从这项研究中获得的知识将被用来将种子裂纹注入到工件的切削区。其次，将确定工艺参数(例如，加工条件、刀具几何形状、裂纹几何形状)和零件质量(例如，表面/亚表面损伤、表面粗糙度)之间的关系。这一目标将通过进行机械加工实验，辅以数值建模，并使用表面轮廓术、光学显微镜、扫描电子显微镜和三维光学轮廓术来评估零件质量来实现。这项基础研究将推进脆性材料加工的知识库，并使基于受控裂纹扩展的新工艺开发成为可能。

Precision parts made from a wide variety of brittle materials have broad applications in healthcare, biomedical, energy, photonics, and automotive industries. A big challenge with high speed machining of brittle materials is to achieve high surface quality. A major problem encountered in machining these materials is random crack propagation into the workpiece, resulting in surface/subsurface cracks and thus strength degradation of the machined parts. Existing techniques rely on polishing, a very slow and costly process, to achieve high surface quality. This award supports fundamental research to provide needed knowledge for the development of a novel machining process to overcome this main limitation. The new process will enable high efficiency machining of brittle materials without compromising part quality. The results from this research will generate economic and societal benefits for the U.S. This research involves several disciplines including manufacturing, laser and optics, fracture mechanics, and biomaterials. The multi-disciplinary nature will help enlist underrepresented groups to conduct research and thus positively impact engineering education. The objectives of this research are twofold. First, the relationship between femtosecond laser parameters (e.g., pulse energy, spot size, number of pulses) and microcrack geometry (e.g., crack length, crack orientation, crack gap) will be established. This objective will be achieved by performing laser micromachining experiments to generate seed cracks inside the workpiece material. Knowledge gained from this research will be used to inject seed cracks into the cutting zone of a workpiece. Second, the relationship between process parameters (e.g., machining conditions, tool geometry, crack geometry) and part quality (e.g., surface/subsurface damage, surface roughness) will be determined. This objective will be accomplished by conducting machining experiments, assisted by numerical modeling, and assessing part quality using surface profilometery, optical microscopy, scanning electron microscopy, and three-dimensional optical profilometry. This basic research will advance the knowledge base in machining brittle materials and enable new process developments based on controlled crack propagation.