Research On The Turning-forming Of Thin And Complicated Contour Surface

Modern turning technology, an advanced plastic forming process widely used in aerospace and military industry, has become an important shaping method for flexible manufacturing of small-lot rotary thin shells.At present internal and external production on the above aspect mainly offered the experiment data and the summarize of experience. But there are many effect factors in turning technology, and the process is very flexible, only consulting the experiment data and depending on the experience are difficult to increase the forming quality and processing efficiency. So it is necessary to start with the continuous plastic deformation of turning, adopt computer numerical simulation, theory analysis combining with practice, investigating and understanding systemically the rule of multitrack turning deformation, look after engineering mechanics modern model which accords with practice, make the process of multitrack turning forming base on quantitative description and analysis to the deformation rule and the movement track of turning wheel, fix on the reasonable movement track of turning wheel, apply applied science foundation for setting down turning process.This research mainly aimed at tube-shaped workpiece with curly generatrix which the base metal is LY12, investigated its turning technology with computer numerical simulation combining with process experiment, analyzed the turnability and plastic deformation mechanism during turning, sought the effect rule that the process parameter and so on to turning forming precision, carried out optimizing the process parameter and the process project.Based on analysis of the forming of characteristics of shrink-turning, the four-node quadrilateral axial-symmetric element is used for potting the blank, and some methods to treat loading and dynamic boundary conditions effectively have been proposed. Then ,a mechanical model corresponding to reality is established for elastic-plastic FEM simulation of shrink-turning. Accordingly, the distributions of stress and strain in the forming have been achieved from the FEM simulation. The results of the simulation in different temperature have beencompared in this paper. The results indicated:a) According with simulating results, turning when the temperature was up to 20, the degree of roughcast rigidification was large, the resistance was distinct larger than the turning results when the temperature was 300, and that during simulating the equivalent stress of normal temperature machining was nearer even exceed critical value when material happened to break, defect and rupture easily took place, it was indicated that the turning workpiece gained at this temperature has defects such as "scale", crinkle, "orange", "craze", so cold turning was not suitable to adopt.b) Turning at the temperature about 300, the plasticity of the roughcast increased and the strength of the roughcast decreased, from the simulation results the equivalent stress during processing fell 1.6 times in comparison with processing at normal temperature. During experiment the formability at 300 was obviously better than normal temperature, however, exorbitant temperature could affect the optimal combination the strength and plasticity of material, and straightly affected the forming, and that distortion was produced on the forming sect of the curly generatrix, departed from the working axes line, appeared the phenomena such as conglutination of the surface metal layer, extrusion crinkle without good turning capability.c) Base on experiment of the forming with shrink-turning, the technological conditions of turning have been chosen and optimized. With those technological parameters, the thin-complicated contour surface can be achieved with fine dimensions and excellent shape.