• Transactions of Materials Processing
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• v.7 no.6
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• pp.562-569
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• 1998

The limit drawing ratio (LDR) is a major process parameter in the process design of deep drawing. If the actual drawing ratio is greater than the LDR for a particular stage then an intermediate stage has to b added the process sequence to avoid failure during the drawing operation and the optimal process design considering for the first-drawing and redrawing by using finite element method combined with ductile fracture criterion. From the results of finrte element analysis the optimal value of drawing ratio is obtained which contributes to the more uniform distribution of thickess and the smaller values of the ductile fracture infinal cup.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.727-734
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• 2014

This paper describes multi-scale based ductile fracture simulation using finite element (FE) damage analysis. The maximum and crack initiation loads of cracked components were predicted using proposed virtual testing method. To apply the local approach criteria for ductile fracture, stress-modified fracture strain model was adopted as the damage criteria with modified calibration technique that only requires tensile and fracture toughness test data. Element-size-dependent critical damage model is also introduced to apply the proposed ductile fracture simulation to large-scale components. The results of the simulation were compared with those of the tests on SA333 Gr. 6 full-scale pipes at $288^{\circ}C$, performed by the Battelle Memorial Institute.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.253-253
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• 2008

• Journal of the Korean Society for Precision Engineering
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• v.13 no.11
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• pp.114-123
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• 1996

The major objective of the present paper is to estabilish analytical technique in order to closely understand and analyze the actual shearing process. First of all, isothermal and non-isothermal FE-simulation of the shearing process are carried out using finite element software DEFORM. Based on preliminary simulation using DEFORM, the finite element program to analyze two dimensional shearing process is developed. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. It can be seen that the developed program combined with the ductile fracture criterion and element kill method has enabled the achievement of FE-simulation from initial stage to final stage of shearing process. The effects of punch-die clearance on shearing process are also investigated. In order to verify the effectiveness of the proposed technique the simulation results are compared with the known expermental data. It is found that the results of the present work are in close agreement with the published experimental results.

• Structural Engineering and Mechanics
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• v.91 no.5
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• pp.427-441
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• 2024

Large-scale cantilever reinforced concrete (RC) columns with footing/stub were examined to determine their seismic response under a quasi-static increasing-magnitude cyclic lateral loading. Three-dimensional (3D) numerical models of RC columns with ductile and non-ductile reinforcement arrangements were developed in a Finite Element (FE) software, i.e., ABAQUS, to corroborate them with the experimental study conducted by the author. Both simulated models were validated with the experimental results in all respects, and the theoretical axial capacity of columns under concentric axial load (P₀) was calculated. Subsequently, a detailed parametric study was conducted by adopting the force and reinforcement variables. These variables include axial compression ratios (ACR) varying from 0.35P₀ to 0.7P₀ and the amount of lateral reinforcements taken as 0.33% and 1.31% representing the non-ductile and ductile columns, respectively. This research outcome conclusively quantifies the combined effect of ACR levels and lateral reinforcement spacing on the flexural response and ductility characteristics of RC columns. The comparative analysis reveals that increased ACR levels resulted in a severe reduction in strength, deformability and ductility characteristics of both ductile and non-ductile columns. Structural response of ductile columns at higher ACR levels was comparable to the non-ductile columns, nullifying the beneficial effects of ductile design provisions. Higher ACR levels caused decline in pre-peak and post-peak response trajectories, leading to an earlier attainment of peak response at lower drift levels.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.230-235
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• 2000

By using the finite element method, the Oyane's ductile fracture integral I was calculated from the histories of stress and strain according to every element and then the forming limit of hydroforming process could be evaluated. The fracture initiation site and the forming limit fer two typical hydroforming processes, tee extrusion and bumper rail under different forming conditions are predicted in this study. For tee extrusion hydroforming process, the pressure level has significant influence on the forming limit. When the expansion area is backed by a supporter and bulged, the process would be more stable and the possibility of bursting failure is reduced. For bumper rail, the ductile fracture integral I is not only affected by the process parameters, but also by the shape of preforming blank. Due to no axial feeding on the end side of the blank, the possibility of cracking in hydroforming of the bumper rail is influenced by the friction condition more strongly than that of the tee extrusion. All the simulation results show reasonable plastic deformation, and the applications of the method could be extended to a wide range of hydroforming processes.

• Structural Engineering and Mechanics
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• v.89 no.2
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• pp.199-211
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• 2024

The loading capacity of engineering structures/components reduces after the initiation and propagation of crack eventually leads to the final failure. Hence, it becomes essential to deal with the crack and its effects at the design and simulation stages itself, by detecting the prone area of the fracture. The phase-field (PF) method has been accepted widely in simulating fracture problems in complex geometries. However, most of the PF methods are formulated with second order continuity theoryinvolving C⁰ continuity. In the present study, PF method based on fourth-order (i.e., higher order) theory, maintaining C¹ continuity has been proposed for ductile fracture simulation. The formulation includes fourth-order derivative terms of phase field variable, varying between 0 and 1. Applications of fourth-order PF theory to ductile fracture simulation resulted in novelty in this area. The proposed formulation is numerically solved using a two-dimensional finite element (FE) framework in 3-layered manner system. The solutions thus obtained from the proposed fourth order theory for different benchmark problems portray the improvement in the accuracy of the numerical results and are well matched with experimental results available in the literature. These results are also compared with second-order PF theory and a comparison study demonstrated the robustness of the proposed model in capturing ductile behaviour close to experimental observations.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.125-133
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• 1998

The objective of this study is to propose a new approach for modelling of burr formation process during orthogonal cutting when the tool exits the workpiece. This approach is based on the rigid-plastic finite element method combined with the ductile fracture criterion and the element kill method. This approach is applied to orthogonal cutting process to predict the fracture location and the fracture angle as well as the cutting force. To validate this approach, orthogonal cutting tests inside SEM(scanning electron microscope) at very low speed are carried out using A16061-T6 to observe the behavior of the material during the chip and the burr formation. The results of the experiment are compared with those of the finite element simulation.

• Transactions of Materials Processing
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• v.32 no.2
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• pp.92-99
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• 2023

In this study, shear fracture specimens are designed using finite element analyses for the characterization of ductile fracture criteria of metal sheets. Many recently suggested ductile fracture criteria require experimental fracture data at the shear stress states in the model parameter identification. However, it is challenging to maintain shear stress states in tension-based specimens from the initial yield to the final fracture, and the loading path can be different for the different materials even with the same shear specimen geometries. To account for this issue, two different shear fracture specimens for low ductility/high ductility metal sheets are designed using the sensitivity tests conducted by finite element simulations. Priorly mechanical properties including the Hosford-Coulomb fracture criterion of the aluminum alloy 7075-T6 and DP590 steel sheets are used in the simulations. The results show that shear stress states are well-maintained until the fracture at the fracture initiation points by optimizing the notch geometries of the shear fracture specimens.

• Transactions of Materials Processing
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• v.21 no.7
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• pp.447-452
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• 2012

This paper is concerned with forming of Al-Zn-Mg-Sc aluminum alloy bolts, focusing on the effects of heat treatment and age-hardening on the formability and ductile damage evolution. Both experimental and finite element studies were performed. From the experiments, it is observed that the heat treatment or the normalization of Al-Zn-Mg-Sc aluminum alloy increases its formability dramatically resulting in successful bolt forming, while the effects of age-hardening at room temperature on the stress-strain relationship and formability are not very critical. Deformation characteristics such as distribution of effective stress and strain, material flow, and ductile damage evolution during bolt forming are examined using a commercial finite element package, Deform-2D. It should be noted that the extrusion load predicted by the finite element method matches well the experiment results. The finite element predictions on the deformation characteristics support the experimental observations such as fracture of bolt head flange, material flow, and distribution of hardness.