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。制造优质孔的传统工艺包括许多步骤：定心钻、粗钻、硬化、钻孔、铰刀、磨削、抛光或冷膨胀。孔洞会引起严重的应力集中。因此，疲劳破坏往往起源于飞机和汽车等周期性载荷结构的孔洞，这可能是灾难性的，也可能是代价高昂的。该研究项目采用了一种利用单步加工对已加工表面施加应力的新概念，该概念以前被证明能够将滚动接触的疲劳寿命提高30倍以上。该项目的目标是实现在孔钻孔中使用单步加工对已加工表面施加预应力以降低成本、延长疲劳寿命的显著潜在好处。要执行的任务包括：(1)开发将钻削条件与残余应力分布相关联的工艺模型；(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)将工艺模型与性能模型相关联，从而可以优化最终的残余应力分布，从而优化疲劳。研究结果将有利于飞机、汽车和其他受循环载荷作用的结构的制造行业。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.