Semi-Empirical Prediction And Deformation Study Of Machining Residual Stress In Aviation Thin-Walled Part

During the machining process of aviation thin-walled parts,due to the thermal-mechanical coupling load,the machining residual stress is distributed on the machining surface and subsurface area of the part,thereby leading tolerance errors of the part.This thesis proposes a new semi-empirical prediction method.This method combines empirical prediction,finite element prediction and statistical prediction to predict the turning-induced residual stress distribution curve.Based on semi-empirical prediction results,the sensitivity analysis of the residual stress distribution is carried out.Based on the results of semi-empirical prediction and sensitivity analysis,an axisymmetric rapid prediction model for the deformation of rotary thin-walled parts is established,and the deformation is optimized to solve tolerance error problems.The main research contents are as follows:1.Semi-empirical model of residual stress is established.In the semi-empirical prediction,the bimodal Gaussian fitting method is utilized to fit the residual stress distribution curve calculated by the turning finite element model.The fitting process obtains the coefficient data set of the bimodal Gaussian function.This data set is used as the training set and the random forest algorithm is used as the regression method,establishing the statistical prediction model of cylindrical turning and end turning residual stress distribution curve.In order to ensure the accuracy of the finite element model,which is the source of the training set,an experimental study is carried out.This semi-empirical prediction model follows the modeling process of a general empirical prediction,but it can reduce the amount of experiments and add a finite element analysis module,achieving the purpose of accurately and quickly predicting the residual stress distribution curve.2.Experiments on turning and residual stress measurement are carried out.The experimental research in the semi-empirical prediction model includes the hardness test of the turning material Inconel 718,the turning experiment,the electrolytic corrosion experiment and the residual stress measurement experiment.The residual stress measurement adopts the X-ray diffraction method.Hardness testing improves material property information.The turning experiment aims to introduce the residual stress on the material surface and subsurface.The combination of electrolytic corrosion experiment and residual stress measurement experiment measures the residual stress distribution data.The experimental data is used to correct the finite element model.3.The sensitivity analysis of the residual stress distribution index of the processed surface layer was carried out.According to the residual stress distribution of the cylindrical surface and the end surface,the sensitivity analysis is carried out by the analysis of variance(ANOVA).The influence of cutting parameters on the.The influence of cutting parameters on the four residual stress distribution indicators is analyzed.The four residual stress distribution indicators are surface residual stress(SRS),maximum compressive residual stress(MCRS),depth of maximum compressive residual stress(DMCS)and depth of settling(DS).4.A deformation prediction model for an aviation casing-assembly part is established.Based on the semi-empirical prediction model,combined with the process route,geometric dimensions and structural characteristics of aviation casing-assembly part,which is a kind of rotary thin-walled part,the machining residual stress field of the part is constructed to establish an efficient deformation prediction model with axisymmetric elements;On the basis of the residual stress sensitivity analysis results,the cutting parameters are adjusted,especially the feed rate,to optimize the residual stress distribution of the end turning.Finally,the tolerance error problems are fixed.