Constitutive Model Research And Microstructure Simulation Of Blade Cold Rolling Process

Rolling process is a new technology applying rolling deformation into forging process. It has stable working process, small equipment tonnage, fine work-piece mechanical properties and high production efficiency. Therefore, it has become one of the development trends of aviation blade manufacturing. But there are not further researches and regularity understandings of rolling process because of the complex shape of blade and difficult-to-deform performance of superalloys. The technical schedule and mould shape of blade rolling process are designed according to experience. Moreover, the polishing of blades and adjusting of moulds depend on workers’manual operation. As a result, the production efficiency and quality will not be guaranteed. So, researches on the material flow and forming mechanism of blade rolling process will provide guidance for the optimization design of mould and the select of technical parameters. This thesis carries out researches on the basis of the above situation. And the aim of this paper is to set up a numerical simulation platform for blade rolling process utilizing the software DEFORM-3D.The accurate material constitutive model is essential to ensure the reliability of the numerical simulation. Blade rolling is a process of large plastic deformation and the geometry, material and boundary conditions are all nonlinear. This thesis finds out that the Yoshida-Uemori constitutive model is appropriate for blade rolling process according to the study on constitutive theory. The material of the blade is nickel-based superalloy GH4169. Mechanical property tests of GH4169 under different conditions at ambient temperature are performed to identify the material parameters of the constitutive model. The deformation characters of GH4169 are analyzed and the parameters are identified according to the test results. Then the secondary development of DEFORM is carried out and the constitutive model of GH4169 is added to the material library of the software. The verification of the model is conducted by comparing the numerical simulation results and the test results of the cuboid compression. Then the new material model is adopted to simulate the blade rolling process and the flow rule of the material during the process is obtained. At last, this thesis simulates the microstructure evolution during blade rolling. The evolution of grain size, dislocation density and grain boundary are obtained.The shape of aviation blade is complex and the cross-sections of blade are ever-changing. As a result, blade rolling process belongs to variable cross-section rolling. The works of this thesis provide a new way for the research of the forming law, optimization of moulds and the selection of technical parameters in variable cross-section rolling.