Hole surface strengthening mechanism and riveting fatigue life of CFRP/aluminum stacks in robotic rotary ultrasonic drilling  

作　　者：Song DONG Wenhe LIAO Kan ZHENG Feng XUE Lianjun SUN 

机构地区：[1]School of Mechanical Engineering,Nanjing University of Science and Technology,Nanjing 210094,China

出　　处：《Chinese Journal of Aeronautics》2023年第10期471-484,共14页中国航空学报（英文版）

基　　金：the the Project on the Technological Leading Talent Teams Led by Frontiers Science Center for Complex Equipment System Dynamics(No.FSCCESD220401);the Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2022ZB264).

摘　　要：Carbon fiber reinforced plastic(CFRP)and aluminum stacks are widely used in aviation industry due to light weight and high performance.Millions of rivet holes need to be drilled on body materials,and more than 80%of fatigue cracks occur at the connection holes,so the damage and residual stress of hole surface have crucial effect on the riveting fatigue life of CFRP/aluminum stacks and the flight performance.Recently,robotic rotary ultrasonic drilling(RRUD)technology is a promising method to machine the stacks.However,the hole surface strengthening mechanism in RRUD and the service performance of the riveting joint are not verified.Thus,in this paper,the hole surface strengthening mechanism of RRUD for CFRP/aluminum stacks is investigated,a theoretical residual stress model is established,and the fatigue life experiment of riveted joints is conducted.Firstly,analysis on residual stress in RRUD is carried out with consideration of strengthening force and cutting temperature.Residual stress model is established based on the calculation of elastic stress,plastic stress and stress release.Validation experiment results show that ultrasonic vibration changes residual stress from tensile stress to compressive stress.At the same time,comparative damage analysis of CFRP hole exit and hole surface in robotic conventional drilling(RCD)and RRUD is presented.Finally,fatigue strength experiments of riveted joints are conducted for performance verification.Experimental results indicate that fatigue life of single-hole riveted joints is increased by 68%with ultrasonic vibration,and four-hole riveted joint arranged according to aerospace design standards is increased by more than 86%.

关 键 词：CFRP/aluminum stacks Drilling damage Residual stress Riveting fatigue life Robotic rotary ultrasonic drilling 

分 类 号：V261.92[航空宇航科学与技术—航空宇航制造工程] TG938[金属学及工艺—钳工工艺]