Technical Research And Numerical Simulation Of B299 Doorframes

Stretch bending is a process of considerable importance for plastic bending and is widely applied to forming the workpieces of aircraft and car. Many parameters influence the spingback. Springback is one of the important factors that influence the forming quality of blanks. With the development of numerical simulation technology of plastic forming, it is widely applied to analyze the process parameters that influence the forming quality. Using numerical simulation technology ,many researches investigate the plastic forming process. So the paper is aimed at investigating stretch bending by numerical simulation.At first, this dissertation gives a deep analysis to the research actuality and the main research methods of stretch bending technology in the world. Next, it gives a detailed description to the loading and control process of the bending methods and the basic principle of stretch bending. The calculating process of the springback and the determining methods of all the parameters are strongly introduced.As for the doorframes of B299,according to the theory, by combining the 3D B-curve with the CAD software, using AutoLISP language, the contour of the bending die is obtained. The die is designed based on the contour. The bending technics of the workpieces is chosen on the basis of analysis of the die's 3D geometry. The die and the technics are perfected in the course of debugging.On the base of theoretic analysis, the Elastic-plastic FEM models of arm stretch bending are built. The rules of Pre-stretch force, Friction coefficient, Compensatory-stretch force ,Bending radius effect on springback radius are analyzed. In addition ,the author builds finite element model of rotary stretch bending, analyzes and studies the geometric imperfection of wrinkling and warping in stretch bending, obtained the rules between cross section distortion and time. After different forming conditions are analyzed, the influence between bending radius, pre-stretching and the value of section distortion were obtained. The research methods and results are helpful in such as design and optimization of the process and equipments of the stretch bending, improvement of the quality and efficiency of the stretch bending parts and the developments of the stretch bending technology both in theory and in practice...