Study On Residual Stresses And Distortion Theory Of Aeronautica Frame Structure In The Milling

The whole or local part machining distortion caused by cutting is a common problem in the machining filed, and it is more serious to aeronautic and astronautic products. For the large structure and a long period of time in machining, geometry distortion may be caused, which makes them not satisfy the design aim, sometimes, they maybe turn into waster, so the problem of machining distortion affects the throughput and operating costs of aeronautic and astronautic products seriously. That is, this thesis's work of the distortion theory as well as the theoretic and applied study for right technics step has greatly academic and engineer's value.Firstly, the main factor of the machining distortion was analyzed. According to the above results and the technique information appraising from the work place, the key method of solving machining distortion problem was determined by dominating the residual stress in part. By studying the machining residual stress and inherent residual stress in part, the thesis analyzed the law of machining distortion in detail for aeronautic and astronautic field, and advanced some new research methods for improving on machining technology.Secondly, the milling force model was founded for the material of aluminum alloy used in aeronautics, and the mathematics model was deduced for the regression-orthogonal experimental method of four factors and four standards. The models can not only be used in this thesis, but also can be used in similar experimental study for interrelated fields.Thirdly, the mathematics model showing the relationship between machining residual stress and milling parameters was founded by the modern elasto-plastic technique. This model can be applied to studying the quality of machining surface and controlling the part machining distortion.Fourthly, the law of machining route, i.e. tool paths, and working procedure effecting machining residual stress as well as the law of its releasing were analyzed systemically by using three-dimensional Elasto-plastic FEM, which can optimize the tool paths and make the working procedure more rational.In the course of FEM simulation, the birth-death element arithmetic was introduced into simulating material remove, and the kinetic Load-step was used to simulated tools work. While simulating, one load step acted on an element, first, loaded the element and solved, then unloaded the element and solved and killed the element using kill-element technology. And then, the same steps were used for the next element until all elements were "removed". By using this technology, the result of simulation was more precise and accorded with practicality engineering, and so can apply credible sustain in technique to designing reasonable technology route.Finally, the study conclusion in this thesis was validated by compared analysis example's distortion with the real part distortion. The results from the test examples havedemonstrated the feasibility and veracity of the proposed methods.