SIMULATION OF ORBITAL FORMING PROCESS
In this study the feasibility of 3D FEM simulation of the orbital forming process was investigated by evaluating the simulation time. Commercial FEA software DEFORM 3D v4.0 that has an efficient computation algorithm for simulating incremental forming process was used for the simulations and the savings in computation time was determined. In order to provide reliable flow stress for the simulation, a finite element based inverse analysis technique has been introduced. Results show that developed inverse analysis technique is efficient and accurate for use in 3D FEM simulation for process optimization.
Sensitivity analysis based preform die shape design for net-shape forging
A sensitivity analysis method for preform die shape design in net-shape forging processes is developed in this paper using the rigid viscoplastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of B-spline are used as the design variables. The optimization problem is to minimize the zone where the realized and desired final forging shapes do not coincide. The sensitivities of the objective function, nodal coordinates and nodal velocities with respect to the design variables are developed in detail. A procedure for computing the sensitivities of history-dependent functions is presented. The remeshing procedure and the interpolation/transfer of the history-dependent parameters, such as effective strain, are stated. The procedures of sensitivity analysis based preform die design are also described. In addition, a method for the adjustment of the volume loss resulting from the finite element analysis is given in order to make the workpiece volume consistent in each optimization iteration. The method developed in this paper is used to design the preform die shape of H-shaped forging processes, including plane strain and axisymmetric deformations. The results show that a flashless forging with a complete die fill is realized using the optimized preform die shape.
New formula for calculating flow curves from high temperature constitutive data for 300 austenitic steels
Abstract The high temperature flow curves for 301, 304 and 317 stainless steels can be calculated up to the peak stress σ p and peak strain ϵ p by : σ/σ p =[(ϵ/ϵ p exp (1−1ϵ/ϵ p )] c . The values of σ p may be derived from the sinh-Arrhenius constitutive equation for which the constants have already been published based on torsion tests. ϵ p is shown to be linearly related to σ p for each alloy. The values of the shape constant c are shown to have averages of 0.203 for 301, 0.216 for 304 and 0.200 for 317 with average errors of less than 2.6%. The value of c decreases only slightly with rising strain rate and declining temperature. An average value of 0.204 (including 316 with c = 0.193 previously published) may be employed for all the steels without significant increase in the error.