M. S. Joun

Quadrilateral finite‐element generation and mesh quality control for metal forming simulation

An improved looping method for quadrilateral finite element generation, effective especially for automatic metal forming simulation, was presented in this paper. A new splitting criterion to improve the conventional looping method, an artificial boundary scheme to reduce mesh transition regions and an optimal nodal placement scheme to enhance local and global mesh quality were introduced in the standpoint of metal forming engineering. Various application examples were given, which show versatility and applicability of the presented approaches and the developed mesh generator. Application examples including automatic computer simulation of a forging process showed that the presented approaches are powerful for metal forming simulation.

An axisymmetric forging approach to preform design in ring rolling using a rigid–viscoplastic finite element method

Abstract In this paper, a new method for approximately predicting the deformation of material in ring rolling is presented. The plastic flow of material in ring rolling is assumed to be axisymmetric and thus the ring rolling process is considered as a sequence of consecutive forging processes. The problem, having tool velocity as well as material velocity field as unknown variables, is formulated by an axisymmetric rigid–viscoplastic finite element method. The unknown tool velocity is determined by making the circumferential stress on the ring cross-section exist in the range of user-specified values. The approach is applied to preform shape design in ring rolling of bearing races. The predicted results are compared with the experimental ones. It has been shown that the approximate approach presented is useful for engineering design of preform in ring rolling of bearing race-like rings.

Mechanics of femoral head osteonecrosis using three-dimensional finite element method.

Abstract. A three-dimensional finite element model of a femoral head was developed using a surface modeling technique. The distribution of the stress index S (S = effective stress / yield strength,

Automatic Simulation of a Sequence of Hot-Former Forging Processes by a Rigid-Thermoviscoplastic Finite Element Method

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Pass schedule optimal design in multi-pass extrusion and drawing by finite element method

) in various sizes of segmental osteonecrosis was assessed. The stress index of the femoral head was within physiological limits when the necrotic angle was less than 110°. Within both the subchondral region and the deep necrotic region adjacent to the necrotic-viable interface, values of the stress index significantly higher than the normal physiological level (>0.1) appeared when the necrotic angle was 110° or more. In the analysis of 28 osteonecrotic femoral head specimens, fracture appeared in two major locations: the deep necrotic region near the underlying necrotic-viable interface (19 femoral heads) and the subchondral region (7 femoral heads). In 2 femoral heads, the fracture involved both regions. Both sites of fracture coincided with the region of stress index greater than 0.1 in the finite element model study. These results may provide baseline information for predicting the collapse of the femoral head and determining the treatment modality of early stage osteonecrosis.

Finite element analysis of a multi-stage axisymmetric forging process having a spring-attached die for controlling metal flow lines

Abstract In this paper, a computer aided process design technique, based on a forging simulator and commercial CAD software, is presented together with its related design system for the cold-former forging of ball joints. The forging sequence design and its detail designs are generated through user–computer interaction using templates, design databases, knowledge-based rules and some basic laws. The forging simulation technique is used to verify the process design. The detail designs, including die set drawings and die manufacturing information, are generated automatically. It has been shown that engineering and design productivity is much improved by the presented approach from the practical standpoint of process design engineers.

Adaptive triangular element generation and optimization-based smoothing, Part 1: On the plane

A fully automatic forging simulation technique in hot-former forging is presented in this paper. A rigid-thermoviscoplastic finite element method is employed together with automatic simulation techniques. A realistic analysis model of the hot-former forging processes is given with emphasis on thermal analysis and simulation automation. The whole processes including forming, dwelling, ejecting, and transferring are considered in the analysis model and various cooling conditions are embedded in the analysis model. The approach is applied to a sequence of three-stage hot former forging process. Nonisothermal analysis results are compared with isothermal ones and the effect of heat transfer on predicted metal flows is discussed.

Hot Deformation Behavior of Bearing Steels

An application-oriented finite-element approach to forging die structural analysis is presented in this paper. The die set structural analysis problem is formulated as a contact problem with both shrink fit and preloaded clamping considered, solved iteratively by a varying penalty method. The loading condition is extracted automatically from forging simulation. A predicted solution is compared with analytical one and two application examples are given, which show the applicability of the approach.