CAREER: Material Removal Mechanism of Ceramic Materials in Ultra-Precision Machining

该学院早期职业发展（Career）计划的研究将对纳米级加工过程中陶瓷材料的去除产生基本的理解。陶瓷，如蓝宝石、氧化锆、氟化钙等，具有许多优异的机械、化学、生物医学和光学性能，但由于其高硬度和脆性，制造陶瓷部件非常困难。然而，在微观尺度上，陶瓷可以像金属一样被加工，尽管解释这一现象的机制尚不清楚。一般的机械加工会在陶瓷表面产生裂纹，因为材料的晶体结构容易断裂。每个晶体结构都有多个断裂系统；每个裂缝系统都可以在某些条件下启动，特别是在高压下。本研究将探讨切削作用产生的力如何引发断裂，并将利用这一理解，使切削可以在不产生裂纹的情况下进行。这项研究将允许陶瓷在各种行业中使用，包括消费电子、生物医学和国防应用以及光学元件。因此，研究直接而有利地影响着经济福利和国家安全。本项目所产生的知识将通过先进的CNC（计算机数控）机床培训计划、在线专家系统和公共媒体传播，并整合到本科和研究生课程中。该项目的目标是了解陶瓷的微观晶体结构如何影响加工过程中的材料行为。该研究将明确陶瓷的韧性剪切和脆性断裂的激活机制。这些知识将导致加工策略的发展，以抑制脆性断裂，并使陶瓷的延性模式加工具有广泛的应用。该研究将首先测试三个潜在参数（分解剪切应力、断裂能和应力强度因子）在激活塑性变形或裂纹萌生中的作用。具体贡献将包括：(1)蓝宝石和氧化锆的每个独特晶体平面的所有方向的韧脆性转变发生的临界切割深度的数据生成；(2)滑移系统或断裂系统激活的触发参数识别；(3)陶瓷加工建模。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) Program research will create a fundamental understanding of ceramic material removal during nanoscale machining. Ceramics, such as sapphire, zirconia, calcium fluoride, etc., have many superior mechanical, chemical, biomedical and optical properties, but fabricating ceramic components is very difficult due to their high hardness and brittleness. However, at a microscopic scale, ceramics can be machined like metals, although the mechanism explaining this phenomenon is not yet known. General machining creates cracks on ceramic surfaces because the crystal structure of the material is prone to fracture. Each crystal structure has multiple fracture systems; each fracture system can be initiated under some conditions, especially high pressure. This study will explore how the force generated by cutting action initiates fracture and will use this understanding so that cutting can be done without generating cracks. The research will allow the use of ceramics in various industries, including consumer electronics, biomedical and defense applications, and optical elements. Thus, the research directly and favorably affects economic welfare and national security. The knowledge generated from this project will be distributed through the advanced CNC (Computer Numerical Control) machine training program, online expert system, and public media in addition to journal publication and integration into undergraduate and graduate courses. The project goal is to understand how the microscopic crystal structure of ceramics influences material behavior during machining. The research will identify the activation mechanisms of ductile shear and brittle fracture of ceramics. This knowledge will lead to the development of machining strategies to suppress brittle fracture and to enable ductile mode machining on ceramics for a wide range of applications. The research will initially test the role of three potential parameters (resolved shear stress, fracture energy, and stress intensity factor) in activating plastic deformation or crack initiation. Specific contributions will include: (1) data generation on critical depth of cut where ductile to brittle transition occurs for all orientations for each distinctive crystal plane of sapphire and zirconia; (2) identification of triggering parameter(s) on activation of slip system or fracture system; and (3) modeling of ceramic machining.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.