Research On Residual Stress Relaxation Model Of 2024-T351 Aluminum Alloy Shot Peening

Fatigue life is an important index to evaluate the performance of components,and residual stress has a significant impact on the fatigue life of components.Shot peening is a surface strengthening technology that can effectively improve the fatigue resistance of components.Because of its low price and convenient operation,it is widely used in machinery,ships,aerospace and other fields.However,the residual stress introduced by shot peening cannot remain stable during the fatigue loading process,and will relax with the cycle.If the impact of residual stress relaxation on the fatigue life is not considered,the expected fatigue life will deviate from the reality,and the fatigue life will be predicted estimates bring uncertainty.In this paper,2024-T351 aluminum alloy material as the research object.Through the combination of theoretical analysis,simulation analysis and experimental verification,the distribution of residual stress induced on the surface of the component by shot peening along with the fatigue cycle period is explored.At the same time,the influence of factors such as the load condition and the degree of cold work hardening were considered,so that the residual stress relaxation model of shot peening was proposed and verified,the research work of this paper is as follows:(1)Based on the analysis of the existing residual stress relaxation empirical model and the pursuit of high efficiency and conciseness of the model,a model with a logarithmic linear model as the main frame is derived.The cold work hardening degree and other factors that have impact on the residual stress relaxation are introduced into the model,and a shot peening residual stress relaxation model is proposed.(2)According to the influence of the shot peening process parameters on the shot peening effect,the shot peening process was tested.The experiment obtained residual stress data through the combination of X-ray diffractometer,electrolytic polishing machine and corrosion liquid phase,obtained the distribution law of shot peening process parameters and residual stress,and determined the process parameters used in shot peening treatment.(3)According to the measured residual stress data of shot peening,it is polynomial fitting and imported into the finite element model through the SIGINI user subroutine of the Abaqus software.Then the model simulation test,using different load intensities to study the distribution of the residual stress of shot peening with the fatigue cycle period.Based on the experimental data,using the Newton-Raphson iterative algorithm of NLS(Non-Linear Least Squares)to calculate the unknown parameters of the residual stress relaxation model of the shot peening,and obtain the fitting data of the model.The comparison between the experimental data and the fitting data verifies The feasibility of the proposed residual stress relaxation model for shot peening.(4)A tensile fatigue test was carried out on the 2024-T351 aluminum alloy shot peened specimen.Based on the whole life test data,the unknown parameters of the residual stress relaxation model of shot peening are calculated using the Newton-Raphson iterative algorithm of NLS,and obtain the fitting data of the model.The comparison between the test data and the fitting data verifies the validity of proposed residual stress relaxation model of shot peening;the comparison between the phased test data and the full-life fitting data verified the applicability of proposed residual stress relaxation model of shot peening.