Study On Shaping Process Analysis And Modeling Method Of Metal Cutting-Extrusion

Metal cutting-extrusion compound shaping technology is a new-style machining method, in this method, with the metal layer cut by main cutting edge, and secondary plastic extruded by rake face and side edge, the function surfaces of different shapes and sizes are obtained, which makes the chips in traditional machining become a part of function surface. So, it is a widely applied promising green manufacturing technology. It is difficult to quantitatively study the cutting mechanism of cutting-extrusion compound shaping by the traditional analytical method and experimental method. By using the numerical simulation and the experiment, the mechanism of metal deformation and chip forming in the cutting process are quantitatively researched. Especially, the rules of metal deformation and modeling method of cutting process are studied.For the typical orthogonal cutting process, based on rigid-plastic FEM and Markov variation principle,the Lagrange description of static large displacement process is adopted, the Misses yield rules based on the rigid-plastic FEM is revised, a uniform constitutive equation is introduced, and the rigid-plastic FEM model of orthogonal metal cutting process based on plane strain hypothesis is constructed.Through on plane-four-node-quadrangle join-unit, the solution field is discretized. Using the bilinear displacement pattern, the relational expressions of unit interior geometry and physical perameter, which take nodes coordinates as parameters are built. The rigid-plastic finite element expression of solving orthogonal cutting is given according to the method of revising punish function.In this thesis, several key techniques in the process of cutting simulation are researched. (1) In the single–point contact problem, a mesh displacement is put forward, which improves the stability of calculating results; (2) The synthesis separation rules based on the geometry and the equivalent stress are adopted to deal with the separating problem between chip and workpiece; (3) A felting unit method is used to reduce calculating error caused by geometry rules; (4) Based on the compound criterion principle of geometry judgment and stress distribution, the release question of the chips restraint nodes and the front tools surface are solved; (5) In themesh rezoning, the arithmetic combining the average weight of areas and that of volumes is adopted, and the parameters transferred from the old mesh system to the new one are realized.The metal distortion characteristics of the workpiece in the metal cutting process are analyzed, the matrix saving and equation solution algorithm are designed which solve the overall rigidity matrix and the overall rigidity equation coefficient used in the programming computation process are designed.A rigid-plastic FEM analyzing program for the orthogonal cutting is developed.The hardening curve of aluminum alloy A6061 is obtained according to the regressing analysis of the uniaxial tensile test data. Taking the planning process as an example, with the aid of rigid-plastic FEM analyzing program developed by author, the aluminum alloy A6061 orthogonal cutting process is simulated in which the distributed result of velocity field, stress field, the strain field, and the cutting force-stroke curve about the deformable body interior are calculated, And then, a rule of variety which is the change of scrap geometry parameter along with change of cutting tool front angle and the friction coefficient are obtained.Based on the analysis of 2-D orthogonal cutting process numerical simulation method, the cutting-extrusion finite element simulation technology is analyzed. The contact relation of cutting tool and the work piece is studied. Using essential key method obtained in the process of 2-D finite element simulation, the cutting-extrusion finite element analysis model is established. Combined with the ANSYS software, the process is analyzed systematically, the distributing stress inside of workpiece is gained, and the fin separation criterion which is important to the feasibility forecast of cutting-extrusion process is presented.Based on the theory analysis, the 2-D cutting process and cutting-extrusion process test are operated, the results show that 2-D cutting simulatied results agreed well with the actual operation performace. The 3-D cutting-extrusion process simulated results accord with the actual operation performance on the whole, which can provide parameter choice for the actual operation performance.