Effects of Machining Induced Residual Shear and Normal Stresses on Fatigue Life and Stress Intensity Factor of Inconel 718

Yang Hua,Zhanqiang Liu

doi:10.3390/app9224750

Abstract

Residual shear stresses and normal stresses induced by machining affect the fatigue performance of components. Thus, residual shear and normal stresses should be considered simultaneously when evaluating the influence of residual stress on fatigue performance. In the present paper, the influences of residual shear and normal stresses on the fatigue life and stress intensity factor (SIF) of turned Inconel 718 were investigated. Firstly, the cos α measurement method was utilized to calculate the residual shear stress and residual normal stress of turned Inconel 718. Then, the combined effects of residual shear and normal stresses on fatigue life were evaluated through uniaxial tension–tension fatigue tests. Thirdly, a prediction model for the SIF was proposed by taking the residual shear and normal stresses into account. Finally, the predicted SIF was validated by the published experimental data from the literature. The predicted results of the proposed model generally agreed well with the available experimental data.

Highlights

Inconel 718 has good mechanical properties such as high yield and high ultimate tensile strength, fatigue resistance as well as good corrosion resistance at a high temperature of 650 ◦ C
The combined effects of residual shear and normal stresses on fatigue life were evaluated through uniaxial tension–tension fatigue tests
Compressive residual stress (CRS) is beneficial to improving fatigue performance [7,8,9], whereas induced tensile residual stress is usually detrimental to the fatigue life of components [10,11]

Summary

Introduction

Inconel 718 has good mechanical properties such as high yield and high ultimate tensile strength, fatigue resistance as well as good corrosion resistance at a high temperature of 650 ◦ C. It has been widely employed in the aerospace industry for parts in turbine engines such as turbine disks, turbine shafts, and high-pressure compressor blades [1]. Once a failure is caused by a fatigue fracture occurring on the turbine disk, turbine shaft, or compressor blade, a larger amount of high-energy debris will be generated. Compressive residual stress (CRS) is beneficial to improving fatigue performance [7,8,9], whereas induced tensile residual stress is usually detrimental to the fatigue life of components [10,11]

Objectives

Methods

Results

Conclusion