Micro-Scale Laser Shock Processing with Controlled Mechanical Properties, Microstructure and Fatigue Performance

激光冲击处理（LSP），也被称为激光喷丸，是一种通过定向激光脉冲将有益的压缩残余应力施加到金属零件表面层中的工艺。 部件在容易过早失效的特定区域进行处理。 它是在70年代初开始的，目前正在生产的零件，如涡轮机叶片使用毫米大小的激光束。 受微系统设计和制造的快速发展的推动，对微尺度LSP（即，使用几微米的激光光斑尺寸）已经显示出可行性。 虽然微系统中的主要材料是硅，但金属厚膜和薄膜结构通常是不可分割的一部分。 这些金属微结构中的一些，例如MEMS致动器、金属涂层微齿轮、微型医疗植入物、微动开关和继电器，在使用中经历循环载荷。 因此，该项目的目标是提高微尺度LSP技术的知识水平，并发展可靠的能力，以修改微系统中的金属结构，控制机械性能，微观结构和疲劳性能。 更具体地说，本项目的目标是：（1）通过适当考虑对有关微尺度重要的现象，并考虑块体、厚膜和薄膜材料，发展对微尺度LSP的更好理解和可靠预测能力;以及（2）设计并正确执行一个积极的实验计划，以补充建模工作，并为进一步的研究积累实验数据。发展 该项目将研究适用于相关微观尺度的表征方法，以测量残余应力分布;以及量化LSP引起的微观结构变化的方法。这项研究对工业界具有重大意义，IBM、LSP Technologies和布鲁克海文国家实验室将提供知识和表征交流。通过纽约市地区专业协会的地方分会，对不同的本科生群体进行教育推广，将加强招聘和留住这些工程专业学生的努力。

Laser shock processing (LSP), also known as laser peening, is a process in which beneficial compressive residual stress is imparted into surface layer of metallic parts by directed laser pulses. Parts are treated the specific areas prone to premature failures. It was incepted in early 70's and is currently in production for parts such as turbine blades using millimeter-sized laser beams. Motivated by the rapid progress being made in microsystem design and fabrication, preliminary studies on micro-scale LSP (i.e., using laser spot size of a few microns) have shown feasibility. While the dominant material in microsystems is silicon, metallic thick- and thin-film structures are often an integral part. Some of these metallic microstructures, such as MEMS actuators, metal-coated micro-gears, micro medical implants, micro-switches, and relays, experience cyclic loads in service. The goal of the project is thus to advance the state of knowledge in micro-scale LSP technology, and to develop reliable ability to modify metallic structures in microsystems, with controlled mechanical proper-ties, microstructures and fatigue performance. More specifically, the aims of this project are (1) to de-velop better understanding and reliable prediction capabilities for the micro-scale LSP by properly consid-ering phenomena important to the micro scale concerned, and by considering both bulk, thick- and thin-film materials; and (2) to design and properly execute an aggressive experimental program to complement the modeling effort and to accumulate experimental data for further development. This program will in-vestigate characterization methods appropriate for the micro-scale concerned to measure residual stress distribution; and methods to quantify microstructure change caused by LSP. This research is of substantial interest to industry, and support from IBM, LSP Technologies and Brookhaven National Lab will provide intellectual and characterization exchanges. Education outreach to a diverse group of undergraduate stu-dents through local chapters of professional societies in the New York City area will enhance efforts to recruit and retain these students in engineering.