Research On The Mechanism Of Micro-milling Thin-walled Micro-structured Component And The Effect On Its Mechanical Properties

The rapid development of the aerospace field requires instruments and apparatus with the properties of miniaturization,high-precision and long-service.The research objective of this article is the core component of a novel accelerometer,namely thin-walled micro-structured component.The characteristics of this thin-walled micro-structured component mainly instantiate at three aspects:(1)The material of this component is imported Elgiloy alloy which belongs to hard-to-machine material with high tensile strength.(2)The feature sizes and the thickness of the microstructure of this component are tiny and a minuteness tool is required.The effect of a small diametral tool should then be considered in the micro-milling process.(3)The requirement of the surface quality and mechanical properties is very high.Taking into account these characteristics,this paper analyzes the micro-milling mechanism and the mechanical properties of the thin-walled micro-structured component.The main research includes the analysis of micro-milling force,the formation mechanism and the changing law of the burrs at exit position,the analysis and improvement of the machined surface traits,and the changing law of the mechanical properties.Micro-milling force is a critical physical quantity which reflects the micro-milling process,so this paper starts from the analysis of micro-milling force and introduces the influence of slight diametral tool in the micro-milling force model.As the feed per tooth is on the same order of tool runout displacement,the micro-milling force model considers the effect of tool runout displacement.Based on the analysis above,the micro-milling force model considers the interaction between historical paths of tool teeth.Then,we analyze the influence of the size effect on the micro-milling force.The experimental results show that there is good agreement between the predicted micro-milling force and the measured micro-milling force.The research on micro-milling force lays a foundation for studying the formation mechanism of burrs at exit position.In the process of micro-milling thin-walled micro-structured component,the feature size of the burrs at exit position approaches that of the microstructure of the component.It not only decreases machining accuracy and surface quality,but also affects the mechanical properties.Thus,this paper proposes a modified burr feature extraction method based on the Canny operator-changing threshold to solve the issue that the burr features at exit position are discontinuous.Then the influence degrees of machining parameters and their interaction on the burrs at exit position are studied.Based on the principle of conservation of energy and combining the conclusion that the tool runout has great impacts on micro-milling force,feature models of the burrs at exit position considered tool runout are established.The features models of the burrs at exit position are evaluated through comparison experiments.The experimental results show that the predicted results of the established models have a good agreement with the experimental results.This study provides significant evidence for studying the method of inhibiting the burrs at exit position.Based on the formation mechanism of the burrs at exit position,this paper firstly analyzes the changing law of exit burr height with the condition of using a supporting structure in the micro-milling process.Aiming at the current clamping type of thin-walled micro-structured component,we investigate the deformation of the low-stiffness part which may appear in the machining process.Based on the analysis above,we propose a non-polluting auxiliary method which improves machining quality,to improve surface quality,dimension accuracy and to inhibit burr formation at exit position.To further improve surface quality,we conduct studies with taking MQCL as an auxiliary method.In the study,Isopar H,ethyl alcohol and distilled water are used as coolants,and dry machining is also considered as a reference.The influence of physical properties of coolants on the above indexes is analyzed though contrastively analyzing surface quality,surface accuracy,tool wear and mechanical properties under various coolants.This research offers references for improving surface quality and mechanical properties of the thin-walled micro-structured component.Besides improving surface quality and mechanical properties of the thin-walled micro-structured component,engineering applications pay close attention to obtaining the mechanical properties.Now,the mechanical properties of the thin-walled micro-structured component are obtained by destructive tensile test,and the component cannot be used anymore.Considering the thin-walled feature of the component,the effect of surface traits on mechanical properties is significant.Thus,this paper proposes a damage-free acquisition method of mechanical properties based on surface traits.To keep the surface feature information as complete as possible,we characterize surface structure traits firstly and verify its validity through correlation analysis.The surface quality,surface structural traits,and surface anisotropy are extracted from the machined surface.The influence of machining parameters on surface traits is analyzed by correlation analysis.As the space dimension composed of extracted surface traits from machined surfaces is comparatively high,this paper adopts the principal component analysis(PCA)to reduce the surface traits dimensions from three to two.Then we contrastively analyze polynomial regression and SVR method to verify the validity of predicting the mechanical properties.The residual analysis shows that this method can predict the mechanical properties well and it realizes obtaining the mechanical properties of the thin-walled micro-structured component without damage.