A Novel Single-Step Superfinish Hole Making Process for Maximum Fatigue Life

孔是机械加工中最常见的特征。 制造高质量孔的传统工艺包括许多步骤：定心钻、粗钻、淬火、镗孔、铰孔、磨削、抛光或冷扩。 孔洞会引起严重的应力集中。 因此，疲劳失效通常起源于诸如飞机和汽车等循环载荷结构中的孔，这可能是灾难性的并且代价高昂。 一个新的概念，使用单步加工预加应力的加工表面，这是以前被证明有能力提高滚动接触的疲劳寿命超过30倍，应用在这个研究项目。 该项目的目标是实现显着的潜在好处，使用单步加工，以预加应力的加工表面钻孔，以最大的疲劳寿命，降低成本。 要执行的任务包括：（1）开发将钻孔条件与残余应力分布相关联的过程模型;（2）开发将残余应力分布与疲劳寿命相关联的性能模型;以及（3）将过程模型与性能模型相关联，使得最终残余应力分布（因此疲劳）可以被优化。 研究结果将对飞机、汽车等承受循环载荷的结构的制造业有所裨益。 由于钻井作业的规模很大，即使效率略有提高，也会产生重要的实际和经济效益。

A hole is the most common feature in machining. The conventional process for making quality holes consists of many steps: centering drill, rough drill, hardening, boring, reaming, grinding, burnishing or cold expansion. A hole gives rise to severe stress concentration. As a result, fatigue failure often originates at the hole in cyclically loaded structures such as aircraft and automobiles, which can be catastrophic as well as costly. A new concept of using single-step machining to pre-stress the machined surface, which was previously shown to have the capability of improving the fatigue life of rolling contact over thirty times, is applied in this research project. The objective of the project is to realize the significant potential benefits of using single-step machining to pre-stress the machined surface in hole drilling for maximum fatigue life at a reduced cost. The tasks to be performed include: (1) developing a process model that relates the drilling conditions to the residual stress distribution; (2) developing a performance model that relates the residual stress distribution to fatigue life; and (3) linking the process model to the performance model so the final residual stress distribution, thus the fatigue, can be optimized. The research results will benefit the industries manufacturing aircraft, automobiles, and other structures subject to cyclic loading. Because of the vast scale on which drilling operations are carried out, even a slight increase in the efficiency would yield important practical and economic benefits.