Study On Numerical Simulation Of Multi-stage Deep Drawing Process Of Sheet Metal

Multi-stage deep drawing process is used widely in a variety of industrial fields, such as automotive applications, aerospace parts, as well as a wealth of other products. In multi-stage deep drawing process, the total amount of deformation is divided several parts, and formed sequentially in several deep drawing steps. In this process, the blank of later steps'has experience several deformation, the material mechanics and the part's geometry has changed, so multi-stage deep drawing has some difference from first deep drawing, the deformation mechanism is very complicated and the mechanical properties for the final product are difficult to predict, the process design is not easy for the manufacturing of a product of desired shape. But now, most research on sheet metal forming are focus on one step deep drawing process, and many theories and experiences are derived from hypothesis and simplification of first deep drawing process, so the multi-stage deep drawing has many difficulties. And still now, few articles cover this problem. A comprehensive research is performed in this paper by the way of numerical simulation. The research in this paper is very valuable in guiding multi-stage practice and physical simulation and forwarding the using of advanced manufacture technology in the sheet metal forming field. In this dissertation, the basic finite element theory based on non-liner finite deformation is elaborated. The elastic-plastic finite element equations and their scope of application of several kinds of finite deformation based on T.L. and U.L. formulation are compared. The characteristic of implicit, dynamic and synthetical algorithm is analyzed, and the numerical performance of all sorts of shell element and contact friction model which is fit for simulation of drawing is introduced, and the article analyzes Hill's quadratic anisotropic yield function and Barlat's quadratic anisotropic yield function, and discusses how to choose yield function. The article also points out that BT element is fit for multi-stage deep drawing process. The article has a complete research on multi-stage cup drawing process. The key technologies in multi-stage deep drawing process numerical simulation, such as selection of anisotropic yield criterion, selection of shell element types, dealing with the boundary condition, contact and friction on the tool surface, plotting grid, building the geometry of second deep drawing process'binder and passing the history information from one stage to another one, etc. It is a future trend using advanced manufacturing technologies, such as numerical simulation to solve the problems produced in industry. Based on the above work, and taking the tube bracket as an example, the author has studied the law of multi-stage deep drawing by playing a lot of numerical simulation of different technical parameters and material performance, such as punch corner profile, the clearance of die and punch, the friction of die, punch and binder surface, the blank-holder force, etc. Finally, the research results indicate that the numerical simulation can forecast the shortcoming in drawing, such as wrinkle, split, low strain and optimize the die and drawing process. As a result, the trial can be decreased or even be canceled, and the drawing quality can be improved greatly.