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、光子学和汽车行业有着广泛的应用。脆性材料高速加工的一大挑战是实现高表面质量。在加工这些材料时遇到的主要问题是随机裂纹扩展到工件中，导致表面/亚表面裂纹，从而导致加工零件的强度降低。现有技术依赖于抛光，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所需的知识，以克服这一主要限制。新工艺将实现脆性材料的高效加工，而不会影响零件质量。这项研究的结果将为美国带来经济和社会效益。这项研究涉及制造、激光和光学、断裂力学和生物材料等多个学科。多学科的性质将有助于争取代表性不足的群体进行研究，从而积极影响工程教育。这项研究的目的是双重的。首先，飞秒激光参数（例如，脉冲能量、光斑尺寸、脉冲数）和微裂纹几何形状（例如，裂纹长度、裂纹方向、裂纹间隙）将被建立。这一目标将通过进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注入种子裂纹到工件的切割区。第二，工艺参数之间的关系（例如，加工条件、工具几何形状、裂纹几何形状）和部件质量（例如，表面/次表面损伤、表面粗糙度）。这一目标将通过进行机械加工实验，辅助数值建模，并使用表面轮廓仪，光学显微镜，扫描电子显微镜和三维光学轮廓术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基础，并使新的工艺开发的基础上控制裂纹扩展。

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.