Papers by Keyword: Rigid Viscoplastic

Abstract: Combining element free Galerkin method with rigid/visco-plastic flow theory, the paper establishes the three-dimensional rigid/visco-plastic element free Galerkin method, and introduces it to analyze three-dimensional bulk metal forming processes. The velocity field is approximated by MLS method. Employing the incomplete generalized variation principle, stiffness matrix equation and solution formulas are derived. And STL format discrete triangular patches are used to describe the mould cavity. An analysis program for simulating three-dimensional bulk metal forming processes is developed. The program is capable of simulating three-dimensional unsteady bulk metal forming processes with severe deformation and arbitrarily shaped dies. A numerical example is analyzed. Numerical results such as material flow patterns and distributions of the effective stress are obtained. The effectiveness and validity of the proposed method and techniques are demonstrated by comparing with results obtained by using commercial finite element software.

Abstract: In order to describe scale effects in rigid-viscosity-plastic deformation at micro scale, a strain rate gradient model with couple stress is proposed. In the constitutive equation, couple stress, strain rate gradient are introduced on the assumption that the potential energy depends upon the scalar invariants of the strain rate tensor and strain rate gradient tensor, at the same times, the influences of length scale of body, grain size and temperature are also considered. A FEM-based program based on this strain rate gradient model is used to simulate the process of high temperature gas pressure forming, and the value of length scale 2 l is evaluated by simulation pilot calculation. It is indicated that rigid-viscosity-plastic deformation can be more accurately simulated by the present strain gradient rate model as long as the material parameters in constitutive equation are selected suitably.

Abstract: Analysis of the forging of gas turbine rotor blades is a complex operation because of the complicated three-dimensional geometry and the non-steady state contact between the workpiece and the die surface. As a result, the simulation of blade forging performed so far has been restricted to two-dimensional plane-strain problems or simplified three-dimensional deformational cases throughout which some simplifications and assumptions are employed. In this paper a three-dimensional analysis of the non-isothermal multi-stage forging process of a gas turbine rotor blade from a cylindrical billet to a complicated product is presented, using 3D rigid-viscoplastic FEM. The simulation results of the blade forging processes are summarized in terms of deformed configurations, the material flow net pattern of typical cross-sections, the distribution of different field variables such as strain and stress, and the load-stroke relationships for each operational stage, in this way the forming laws during forging process of a gas turbine rotor blade being revealed. The validity of simulation results has been verified through comparisons with forging tests, which show good agreements with numerical simulation results. The simulation results may be effectively applied to other types of three-dimensional turbine blade forging processes.