• Design & Manufacturing
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• v.2 no.2
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• pp.43-47
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• 2008

This paper is concerned with the analysis of material flow characteristics of stepped rod forming. The analysis in this paper concentrated on the evaluation of the design parameters for deformation patterns of tube forming, load characteristics, extruded length, and die pressure. The design factors such as punch nose radius, die corner radius, friction factor, and punch face angle are involved in the simulation. The stepped rod forming is analyzed by using a commercial finite element code. This simulation makes use of stepped rod material and punch geometry on the basis of punch geometry recommended by International Cold Forging Group. As radius ratio is large, forming load was reduced but extruded length ratio was increased.

• Journal of Welding and Joining
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• v.26 no.4
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• pp.66-72
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• 2008

Because of high intensity and easy controllability of the heat source, high frequency induction heating has been concerned and studied for the steel forming process in the ship building industry. However, the heating and forming characteristics have to be further properly modelled and analyzed for the process to be utilized with its optimal working parameters. In this study, a modelling with thermo-elasto-plastic analysis is performed using the FEM to study heat flow and deformation of the steel plate during the forming process with the electro-magnetic induction heating. The numerical model is then used to study the effect of the inductor shape on the magnitude of angular deformation of the plate during the forming process. It is revealed that the square shape of inductor induces the largest deformation among the rectangular inductors.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.156-164
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocity and temperature fields during rheology forming process, the earth governing equation correspondent to the liquid and solid region are adapted. Therefore, each numerical models considering the solid and liquid region existing within the semi-solid material have been developed to predict the deflect of rheology forming gnarls. The Arbitrary Boundary Maker And Cell (ABMAC) method is employed to solve the two-phase flow model of the Navier-Stokes equation. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity. The liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.656-662
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• 2015

In the present study, multi-layered Si DLC (Silicon Diamond-Like Carbon) coatings with HMDSO (Hexamethyldisiloxane) buffer layers are applied on SKD 11 substrates by PECVD (Plasma Enhanced Chemical Vapor Deposition) with different HMDSO gas flow rates, while the gas flow rate of $C_2H_2$ is fixed to enhance the electric resistivity of forming dies for electrically assisted forming. The HMDSO buffer layer is introduced to increase adhesion between the base metal and Si-DLC layers. The result of evaluation of electric resistivity and adhesion strength shows that the properties are affected by the flow rate of HMDSO, while the flow rate of 80 sccm results in the coating with the highest electric resistivity and adhesion strength among the selected flow rates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1971-1981
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• 2002

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocities and temperature fields during rheology forming process, the each governing equations correspondent to the liquid and solid region are adapted. Therefore, each numerical model considering the solid and liquid coexisting region within the semi-solid material have been developed to predict the defects of rheology forming parts. The Arbitrary Boundary Maker And Cell(ABMAC) method is employed to solve the two-Phase flow model of the Navier-Stokes equation. Theoretical model basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on using the liquid and solid viscosity. The Liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.124-128
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum ahoy has been studied Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The unposed mathematical model is applied to the die shape of the two type. To calculate the velocities and temperature fields during rheology forming process, the each governing equation correspondent to the liquid and solid region are adapted. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.190-193
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• 2004

Ever since the ideal forming theory has been developed fur process design purposes, application has been limited to sheet forming and, for bulk forming, to two-dimensional steady flow. Here, application for the non-steady case was performed under the plane-strain condition based on the theory previously developed. In the ideal flow, material elements deform following the minimum plastic work path (or mostly proportional true strain path) so that the ideal plane-strain flow can be effectively described using the two-dimensional orthogonal convective coordinate system. Besides kinematics, for a prescribed final part shape, schemes to optimize a preform shape out of a class of initial configurations and also to define the evolution of shapes and boundary tractions were developed. Discussions include the two problematic issues on internal tractions and the non-monotonous straining. For demonstration purposes, numerical calculations were made for a bulk part under forging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.450-453
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• 2009

In order to overcome drawbacks of the advanced high strength steel such as inferior formability and large springback, the hot press forming process(HPF) has been being applied for forming of automotive sheet parts. Good formability and dimensional accuracy without springback as well as good crash performance of final products are the advantages of the HPF process. In this work, a method to characterize the mechanical properties of the HPF steel was developed based on the simple tension test at high temperatures and its finite element analysis, while it was applied to obtain strain rate and temperature dependent flow curves of the HPF steel. The final flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.401-402
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• 2007

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.96-100
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• 2000

It is difficult to predict material behavior of forming process because the plastic instable flow phenomenon happens in practical forming process I. e. upsetting backward extrusion piercing indentation. In view of the direct relationship between instable material flow and quality defects of the products we should find out their phenomena, In this study we introduced the plastic spin and the kinematic hardening considering the kinematic hardening constitutive equation for rate-dependent material. Also analysis of upset forging is carried out using the rigid plastic FEM with Al7075