Three-dimensional Thermo-viscoplastic Finite Element Analysis of Cogging Process for Lange Ingots

Cogging is generally the initial and primary step in the manufacture of practically all large open-die forgings, and consists of forging and ingot by reducing the cross-section and simultaneously enlarging the body. A three-dimensional thermo-viscoplastic finite element model is used to study the distribution of internal stresses and strains of workpiece and temperature of workpiece and die during cogging process. Simulations are carried out on an circular ingot, using v-die and flat die, to study the effects of die configuration, die width, penetration depth, temperature gradient, die overlapping and pass design

Use of a Drawing Process to Manufacture a Large-Size Dome Shaped Forging-Produts

A new forming process of the large-size forging within the limit of forming loads is developed by introducing the drawing process, which usually used to apply to sheet forming. For the development of the forming process, corresponding numerical simulation are carried out. The approach is based on the Taguchi method, and utilize the DOE for design of FEM analyses. In this study, the important factors are chosen at first, and then the concept of signal-to-nose(S/N) rate is applied to evaluate the formability of large size forging-products, and each value of the design parameter is determined

3차원 열간단조의 열-점소성/유한요소해석

학위논문(박사) - 한국과학기술원 : 정밀공학과, 1993.8, [ [vii], 130 p. ]In order to design forging processes effectively and to prevent the defects, analysis of the processes is essential, for the die design and the die manufacture. For the complex problems, numerical method are commonly used for the modeling of forging processes. The effectiveness of the finite element method has long been proved for the prediction of metal flow and defects, forging load, stress and strain distributions, temperature gradients and tool distortion. Since materials at the elevated temperature are usually rate-sensitive, analysis of hot forging requires two considerations; the effect of the rate-sensitivity of materials and the coupling of the metal flow and heat transfer analysis. The material behavior that exhibits rate-sensitivity is called viscoplastic. A three-dimensional thermoviscoplastic finite element formulation is presented considering the heat transfer. An efficient three-dimensional finite element code of the workpiece and the die has been developed for the simulation of hot forging. The finite element method and the boundary element method are employed for the analysis of the heat transfer. The boundary element method is one of the efficient methods for the transient heat trasfer analysis, because element nodes are fined only on the extemal surface and intermal unknowns are not required. To show the effectiveness of the three-dimensional thermo-viscoplastic finite element method, forging processes which are useful in the industry such as cogging process and turbine blade forging are analyzed. Simulation of the cogging process focuses on the influence of various cogging paramenters on centerline consolidation such as die shape, die width ratio and temperature gradient of ingot. In turbine balde forging, the forging experiment was carried out in the laboratory condition and compared with the computation. It has been shownd that the results of the experment and the computation are in good agreements in forging load, temperature distribut...한국과학기술원 : 정밀공학과