• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.2 s.173
• /
• pp.394-402
• /
• 2000

Densification behavior of titanium alloy powder was investigated under hot isostatic pressing at various pressures and temperatures. Uniaxial creep responses of a dense specimen were also obtained at high temperatures. The densification model of Abouaf and co-workers was implemented into a Finite element program (ABAQUS) to compare with experimental data for titanium alloy powder. The agreements between finite element calculations and experimental data for deformation and densification of titanium alloy powder were good during hot isostatic pressing.

• Transactions of Materials Processing
• /
• v.8 no.5
• /
• pp.498-506
• /
• 1999

The metal forming processes of aluminum alloy wheel forging at elevated temperature are analyzed by the finite element method. A coupled thermo-mechanical model for analysis of plastic deformation and geat transfer is adapted in the finite element formulation. In order to consider the strain-rate effects on material properties and the flow stress dependence on temperatures, rigid-viscoplasticity is introduced in this formation. In this paper, several process conditions were applied to the dimulation such as die speed, rib thickness, and depth of die cavity. Simulation results are compared, and discussed with each case. Metal flow, die pressure distributions, temperature distributions, velocity fields and forging loads are summarized as basic data for process design and selection of a proper press equipment.

• Transactions of Materials Processing
• /
• v.28 no.1
• /
• pp.34-42
• /
• 2019

In this study, various alloying elements (Cr, Sr, Ca, Cd) were added to improve the mechanical properties of ADC12 fabricated by a die casting process. The effect of alloying elements on the microstructure and mechanical properties were investigated. The phase analysis results of the modified ADC12 alloy with conventional ADC12 alloy, showed the similar characteristics of Al matrix, Si phase, $CuAl_2$ phase and the Fe intermetallic phase. As a result of the microstructure observation, the secondary dendrite arm spacing (SDAS) was shown to have decreased after the addition of the alloying elements. The eutectic Si phase, which existed as flake form in the conventional ADC12 alloy, was modified finely as a fiber form in the modified ADC12 alloy. It was observed that the $CuAl_2$ phase as the strengthening phase was relatively finely distributed in the modified ADC12 alloy. The Fe intermetallic appeared as a Chinese script shaped $Al_6$ (Mn,Fe) which is detrimental to mechanical properties in conventional ADC12 alloy. On the other hand, in the modified ADC12 alloy, polyhedral ${\alpha}-Al_{15}Si_2$ $(Fe,Mn,Cr)_3$ was observed. The tensile properties were improved in the modified ADC12 alloy. The yield strength and tensile strength increased by 12.4% and 10.0%, respectively, in the modified ADC12 alloy, and the elongation was also seen to have been increased. As a result of the pin on disk wear test, the wear resistance properties were also improved by up to about 7% in the modified ADC12 alloy. It is noted that the wear deformation microstructures were also observed, and it was found that the fine eutectic Si and strengthening phases greatly improved abrasion resistance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.139-142
• /
• 2007

This study focuses on the manufacturing process of a magnesium alloy impeller used for the fuel cell car using the hot forging technology. The impeller has the very complicated shape with sharply curved blade and thus generally produced by mechanical machining or casting process. However, since these technologies give the high manufacturing cost or poor mechanical properties, the forging technology is required to make the high-quality impeller with the lower manufacturing cost. In order for production of the impeller by forging technology, the parametric studies using finite element analyses were carried out to find the optimal perform shape of impeller made of magnesium alloy AZ 31 and finally die design was proposed based on the simulation results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.357-360
• /
• 2007

The profile ring rolling process of Ti-6Al-4V alloy was designed by finite element(FE) simulation and experimental analysis. The design includes geometry design and optimization of process variables. The geometry design such as initial billet and blank sizes, and final rolled ring shape was carried out with the calculation method based on the uniform deformation concept between the wall thickness and ring height. FEM simulation was used to calculate the state variables such as strain, strain rate and temperature and to predict the formation of forming defects during ring rolling process. Finally, the mechanical properties of profiled Ti-6Al-4V alloy ring product were analyzed with the evolution of microstructures during the ring rolling process.

• Transactions of Materials Processing
• /
• v.17 no.7
• /
• pp.466-472
• /
• 2008

In this paper, tension tests and formability tests are performed to construct a database related to mechanical properties and the formability of the AZ31B Mg alloy sheet. A forming test with a hemi-spherical punch is conducted at varying temperatures to establish a forming limit diagram. In order to verify the applicability of the analysis using the conventional flow hardening model, a finite element analysis is performed on the hemi-spherical punch forming process and the results are compared with experimental ones. The study investigates problems involving a computational analysis that does not consider flow softening of the magnesium alloy at elevated temperatures.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.249-252
• /
• 1999

A numerical analysis was perfomed to predict flow curves and dynamic recrystallization behaviors of Al-5%Mg alloy on the basis of results of hot compression tests. The hot compression tests were carried out in the ranges of 350-50$0^{\circ}C$ and 5$\times${{{{ {10 }^{-3 } }}}}~3$\times${{{{ {10 }^{0 } }}}}/sec to obtain the Zener-Hollmon parameter. In the modelling equation the effects os strain hardening and dynamic recrystallization were taken into consideration. A model for predicting the evolution of microstructure in Al-5%Mg alloy during thermomechanical processing was developed in terms of dynamic recrystallization phenomena, The microstructure model was combined with finite element modeling(FEM) to predict microstructure development Model predictions showed good agreement with microstructures obtained in compression tests.

• Transactions of Materials Processing
• /
• v.8 no.3
• /
• pp.252-261
• /
• 1999

The 3-dimensional finite element program is developed to analyze the non-isothermal forming processes of aluminum-alloy sheet metals. Bishop's method is introduced to solve the heat balance and force equilibrium equations. Also, Barlat's non-quadratic anisotropic yield function depicts the planar anisotropy of the aluminum-alloy sheet. To find an appropriate constitutive equation, four different forms are reviewed. For the verification of the reliability of the developed program, the computational try-outs of the non-isothermal cylindrical cupping processes of AL5052-H32 and Al1050-H16 are carried out. As results, the constitutive equation relating to strain and strain-rate, in which the constants are represented by the 5th-degree polynomials of temperature, is in good agreement with measurement. The computational try-outs can predict optimal forming conditions in non-isothermal forming processes.

• Transactions of Materials Processing
• /
• v.16 no.4 s.94
• /
• pp.223-228
• /
• 2007

The profile ring rolling process of Ti-6Al-4V alloy was investigated by finite element(FE) simulation and experimental analysis. The process design of the profile ring rolling includes geometry design and optimization of process variables. The geometry design such as initial billet and blank sizes, and final rolled ring shape was carried out with the calculation method based on the uniform deformation concept between the wall thickness and ring height. FEM simulation was used to calculate the state variables such as strain, strain rate and temperature and to predict the formation of forming defects during ring rolling process. Finally, the mechanical properties of profiled Ti-6Al-4V alloy ring product were analyzed with the evolution of microstructures during the ring rolling process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.67-69
• /
• 2007

Unusual mechanical constitutive behavior of magnesium alloy sheets has been implemented into the finite element program ABAQUS via user material subroutine. For the verification purpose, the springback of AZ31B magnesium alloy sheet was measured using the unconstrained cylindrical bending test of Numisheet'2002. In addition to the developed constitutive models, the other two models based on isotropic constitutive equations with tensile and compressive properties were also considered. Preliminary comparisons have been made between simulated results by the finite element analysis and corresponding experiments and the newly proposed model showed enhanced prediction capability in springback prediction.