Machining Process Simulation Of Aerospace Monolithic Component

Distortion of aero monolithic component is the most difficult problem to deal with in aeronautical industry. Due to the deformation some complicated straightening technologies have to be adopted. The improper correcting technics inevitably leads the poor quality and eventually discard of useless of distorted component. As a result, the research process of new prototype aircraft is delayed generally. To control the distortion of monolithic component, every phase of monolithic component machining procedure, such as quenching process of blank, pre-stretching to eliminate quenched residual stress, milling mechanism of aluminum alloy, and machining process of monolithic component, is simulated with FEM.Residual stress redistribution of blank due to part material removal is an important factor that results in the deformation of monolithic part. To get a blank with quenched residual stress, a quenching analysis of 7075 aluminum alloy is carried out by applying a sequentially coupled thermal and mechanical procedure. The changes of temperature and the resultant distribution of residual stress are investigated. Furthermore, disregarding the effect of machining loads, redundant material removal is simulated from the quenched blank, and a reduced scale monolithic component is obtained. To testify the finite element results, a reduced scale monolithic component is machined from a quenched blank. Good agreement is found between the finite element results and the experiment values. That indicates the original residual stress is the main element of causing deformation, and the reliability of sequentially coupled thermal and mechanical method is tested at the same time.Although the strength and toughness of aluminum alloy 7075 can be increased greatly by quenching, this process will result in large magnitude of residual stress. To eliminate quenched stress, pre-stretching is needed. Taking a blank with quenched residual stress, and considering different pre-stretching conditions (pre-stretching magnitude are 1%, 2% and 3%, respectively), some quenched-stress redistributions are obtained. The research shows that the magnitude of plastic strain is between 2.1%~2.6%, and the residual stress is removed about 86% while the blank is pre-stretched about 3%. With a pre-stretching of 3%, the deformation of workpiece reduced by 94.5% than that without stretching. There is just a little difference between pre-stretching of 2% and 3% to relax residual stress and to reduce workpiece deformation respectively. So, the magnitude of pre-stretching for 7075 alloy recommend that not larger than 3%. That is in good accord with technical requirements of aviation aluminum alloy.The second factor which causes monolithic component distortion is machining process. To realize the milling process simulation of monolithic component, dynamic loads must be considered, including cutting forces and cutting temperatures. Dynamic loads can be indirectly achieved through finite element model (FEM) of machining. There are lots of finite element models for simulating cutting process, but most of them are based on orthogonal cutting, and oblique cutting model is rarely studied, let alonedouble-edge-oblique cutting. In practice, double-edge oblique cutting model is much more closer to the reality than others. This research work aims to simulate three-dimensional milling operation of aluminum alloy with a double-edge tool. Commercial software DEFORM 3D is used. The simulation results such as milling loads in three directions, stress, strain and temperature distribution during milling process in the workpiece are analyzed and proved reasonably. Further more, there is a good agreement between the shape of chips obtained from FEM and experiment. The finite element model presented in this paper will be a shortcut for further parameter optimization and the improving of tool shape design, a base for the building of optimization parameters database, and also a new way to control distortion of monolithic aluminum structures.Dynamic loads of milling process and a quenched and pre-...