Study On The Machining Deformation And Residual Stress Of Thin-walled Aluminum Alloy Structure

The number of thin-walled structures applied in aerospace industry is increasing.But with the improvement of machining requirements,the difficulty and the cost of the machining process have increased.The thin-walled structures of aluminum alloy is the main research object in this paper.As the main sources of the machining deformation of the thin-walled structures,the milling force and residual stress are researched.The study of deformation mechanism of thin-walled parts can help to control the deflection of the thin-walled structures in the machining process.So that,the reliable theory can be provided to reduce the deformation by optimizing the machining process.In this paper,the deflection of the cantilever slab and the machining error caused by the axial milling force are discussed.The deformation changes with the direction of the axial cutting force.The structure of milling cutter as the important factor of the axial cutting force also cannot be ignored when the deflection of the thin-walled part is discussed.Using flat-end milling cutter as the main research object,the influence of milling parameters on the deformation of cantilever is studied in this paper.In addition,in order to predict the deformation and machining error of the cantilever plate,a new analytical method is provided in this paper.In this method,the cutting process is discretized into many deformation elements.Based on the theory of symmetrical bending of rectangular plate,the deflection function of cantilever plate is combined with the empirical formula of milling force to predict the deflection of every element.Finally,the deformation and surface error caused by the axial cutting force can be predicted by adding up the deflection of all elements.The research on residual stress of aluminum alloy is divided into two parts.Firstly,the cavity milling test is implemented on aluminum alloy thin-walled part.The influence of different milling cutter on the residual compressive stress of the bottom surface of cavity is analyzed.So that,a reasonable machining strategy can be proposed to improve the stress state of the cavity surface.Secondly,the initial residual stress along the depth of a 25 mm thick aluminium alloy sample is measured using the crack compliance method.The surface residual stress of the sample is compressive stress,and the internal residual stress of the sample is tensile stress.Based on the finite element method,the relationship between the deformation of thin wall part and the removal of material and the effect of reinforcing bar on the deformation of thin part are analyzed.Thus,the theoretical basis is provided for optimizing the placement angle of reinforcing bars of grid-type members.