Research On High-precision Machining Process For Removing Oxide Scale On The Surface Of Titanium Alloy Bar By Turning

With the rapid development of the aerospace industry and the research and development of a large number of civil aircrafts,the aerospace fastener industry has received unprecedented attention.As an important link connecting various parts of aerospace products,aerospace fasteners are used in aerospace products.It has a wide range of applications.Aerospace products have extremely high requirements on the processing quality and processing accuracy of the fasteners;the processing and manufacturing of fasteners mostly use titanium alloy materials,and the processing process of titanium alloy materials is more complicated and difficult to process.Therefore,In order to ensure the quality and safety of the connection between components,it is particularly important to improve the processing quality and processing accuracy of titanium alloy materials.This article takes the titanium alloy blank before forming aerospace fasteners as the test object.Its surface has a certain thickness of oxide scale and initial surface defects.The fatigue performance of the final formed fasteners and their safety in use are mostly dependent on zero The surface quality of the components,and the oxide scale and initial surface defects formed on the surface of the titanium alloy bar greatly affect its surface quality and cannot be directly put into use.Therefore,a new and environmentally friendly lathe-a centerless lathe is used to remove the titanium alloy embryo The surface oxide scale of the material can improve the surface quality.Combining actual processing requirements and test conditions,this paper selects the basic characterization parameters of surface integrity:surface roughness,surface microhardness,and dimensional error as the analysis indicators of surface integrity;this paper focuses on the processing technology of titanium alloy bars.Analyze the influence law of turning process parameters(spindle speed,feed speed,cutting depth)on surface roughness,surface microhardness,dimensional error,and then use the influence law to reverse design process parameters to obtain feasible process parameter domains,Improve surface integrity,so as to meet processing requirements.At the same time,a prediction model of surface roughness and size error is established,which can be applied to the prediction of parts processing quality and accuracy,and provides guidance for the reasonable selection of processing parameters.This article focuses on the effect of turning process parameters on the surface integrity when removing the oxide scale on the surface of titanium alloy bars,and uses the multiple linear regression method to establish a surface integrity prediction model after rough cutting of titanium alloy.At the same time,the initial surface morphology defects of the titanium alloy bars were taken as one of the factors affecting the surface integrity,and titanium alloy bars with different initial surface morphology defects were selected(Initial surface morphology defects produced after precision forging and rolling processes)to conduct experiments to discuss whether different initial surface morphology defects will affect the change law of surface integrity.Finally,according to the change law of surface integrity and actual processing requirements,appropriate process parameters are determined to meet the processing requirements.The main work of the thesis and the results to be obtained are as follows:(1)When removing the oxide scale on the surface of titanium alloy bars by turning,taking into account the different initial morphological defects on the surface of titanium alloy bars,a comparative analysis of the titanium alloy bars with different initial surface morphology defects after turning processing,the same Whether the effect of turning process parameters on its surface integrity is consistent.According to the completely random design principle in the single factor analysis method,the turning process test is designed.Through sensitivity analysis and comparative analysis,the relationship between different initial surface morphology defects and surface integrity changes of titanium alloy bars is discussed.For titanium alloy bars with defective surface morphology,different selection ranges of process parameters are given to obtain the surface integrity that meets the processing requirements.(2)Determine the order in which the turning process parameters affect the surface integrity characterization parameters when removing the oxide scale on the surface of the titanium alloy bar by turning.Through a large number of cutting tests and surface integrity test tests,based on multiple linear regression analysis,the mapping relationship between the turning process parameters and the surface integrity characterization parameters is established:y_j=f_k(q_i);through the significance analysis,the influence factors on the surface integrity characterization parameters are obtained.The order:[X ₁,X ₂.,..X _i.,..]of influence can be adjusted by controlling the changes in the main influencing factors to adjust the changes in surface integrity.(3)The establishment and verification of the multi-factor coupling mechanism model of surface integrity.The multivariate linear regression method is used to establish the surface integrity prediction model,and the prediction value is combined with the test data and the method of comparison verification is used to verify the accuracy of the multi-factor coupling mechanism model:Y_j(28)F_j(Q_i).(4)Determine the feasible parameter range of the surface integrity of the titanium alloy bar after turning and removing the oxide scale on the surface of the titanium alloy bar.According to the processing requirements of surface integrity,set the upper limit of surface integrity in the processing process requirements,determine the feasible parameter domain of turning process parameters through the contour map:[Q₁?Q₂]?[P₁?P₂]?[M₁?M₂],and carry out the experimental verification of the feasible parameter domain to verify its effectiveness And feasibility,in order to meet the design requirements of surface integrity after machining,provide more selections of combinations of turning process parameters.