• Proceedings of the KSR Conference
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• 2004.06a
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• pp.754-760
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• 2004

Structural analysis and tests were conducted for a carbody manufactured by aluminum alloy. The results were compared, and structural safety was evaluated based on the results. Aluminum carbody in Kwangju turned out safe in terms of structural Strength.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.79-84
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• 2004

Strain energy due to the mechanical interaction between self-accommodation groups of martensitic phase transformation is called interaction energy. Evaluation of the interaction energy should be accurate since the energy appears in constitutive models for predicting the mechanical behavior of shape memory alloy. In this paper, the interaction energy is evaluated in terms of theoretical formulation and explicit finite element calculation. A simple example with two habit plane variants was considered. It was shown that the theoretical formulation assuming elastic interaction between the self-accommodation group and matrix gives larger interaction energy than explicit finite element calculation in which transformation softening is accounted for.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.122-125
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• 2005

Magnesium alloys are expected to be widely used for the parts of structural and electronic applications due to their lightweight and EMI shielding characteristics. While the die casting has been mainly used to manufacture the parts from the magnesium alloys, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. However, the magnesium alloy has low formability at room temperature and therefore, in many cases, forming at elevated temperatures is necessary to obtain the required material flow without failure. In the present study, square cup deep drawing tests using the magnesium alloy AZ31 sheet were experimentally conducted at various elevated temperatures as well as room temperature, and the corresponding finite-element simulations, which calculated the damage evolution based on the Oyane's criterion, were conducted using the stress-strain relations from the tensile tests at various temperatures. The formability predictability by the finite-element analysis was investigated by comparing the predicted damage distributions over the deformed AZ31 sheet at elevated temperatures with the corresponding experimental deformations with failures.

• Transactions of Materials Processing
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• v.33 no.3
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• pp.208-213
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• 2024

Ni-based superalloys have exceptional performance in high-temperature strength, corrosion resistance, etc, and it has been widely used in various applications that require corrosion resistance at high-temperature operations. However, the relatively expensive cost of the Ni-based superalloys is one of the major hurdles. The corrosion-resisted alloy(CRA) clad materials can be a cost-effective solution. In this study, finite element analysis of the hot rolling process for manufacturing of the Alloy 625/API X65 steel CRA clad plates is conducted. The stress-strain curves of the two materials are measured in compressive tests for various temperature and strain rate conditions, using the Gleeble tester. Then, strain hardening behavior is modeled following the modified Johnson-Cook model. Finite element analysis of the hot rolled cladding process is performed using this strain rate and temperature dependent hardening model. Finally, the thickness ratio of the CRA and base material is predicted and compared with experimental values.

• Transactions of Materials Processing
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• v.17 no.3
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• pp.189-196
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• 2008

Alloy718 is the nickel-base super alloy well used as gas turbine components under severe operating conditions because of its high strength at high temperature and excellent creep resistance. In this study, a coupling bolt for the gas turbine component is manufactured by hot heading process instead of whole machining in order to improve the mechanical properties. Die shape for the hot heading has been designed by general design rule of hot forging and also optimal process condition has been investigated by finite element method. The initial billet temperature and the punch speed have been determined by $1150^{\circ}C$ and 600mm/s on the basis of finite element analysis, respectively. The coupling bolt has been manufactured by 200ton screw press and evaluated by experiment in order to investigate the mechanical properties. As a result of experiment, the mechanical properties such as hardness, tensile strength and creep behavior have been superior to those manufactured by machining.

• Transactions of Materials Processing
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• v.33 no.1
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• pp.50-54
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• 2024

In this paper, the process of extruding Cu-10Fe alloy using a finite element analysis (FEA) was theoretically analyzed. To achieve this, the dependence of strain rate and temperature of the alloy required for the extrusion process was secured by utilizing databases for Cu and Fe and the KHL model. For microstructure analysis, FE-SEM with EDS was used to distinguish the phases present in Cu-10Fe alloy. The mechanical characteristics of Cu-10Fe alloy were secured using the results of fitting the mechanical properties of Copper and Steel from the Deform database to the KHL model. The deformation behavior within the alloy during hot extrusion was analyzed, providing insights into effective stress, effective strain, effective strain rate, and temperature. It was observed that the strain distribution was non-uniform. These research findings contribute to an improved understanding of the hot extrusion process of Cu-10Fe alloy and can aid in predicting the mechanical properties of the material.

• Transactions of Materials Processing
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• v.8 no.5
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• pp.482-490
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• 1999

7000 series Al alloy with good mechanical properties has been focused with tendency to reduce the components weight of aircraft and automobile. However, it is difficult to manufacture a sound extruded product because of segregation, grain growth, casting defect, surface defect, decreasing extrudability and so on. The objective of this study is to manufacture a new 7000 al alloy more than the extrudability of A7N01 and A7003 through controlling the weight (%) Mg, Zn, Si. Hot extrusion experiments on the axisymmetric rod are performed in 500℃ and also performed analysis of the same process using unmerical analysis method, a coupled rigid-thermoviscoplastic finite element method. Extrusion limit diagram was obtained for the developed alloy by FE-simulation in order to define the relationship of extrusion speed and initial billet temperature.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.1036-1046
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• 2016

We propose a primary water stress corrosion cracking (PWSCC) initiation model of Alloy 600 that considers the stress triaxiality factor to apply to finite element analysis. We investigated the correlation between stress triaxiality effects and PWSCC growth behavior in cold-worked Alloy 600 stream generator tubes, and identified an additional stress triaxiality factor that can be added to Garud's PWSCC initiation model. By applying the proposed PWSCC initiation model considering the stress triaxiality factor, PWSCC growth simulations based on the macroscopic phenomenological damage mechanics approach were carried out on the PWSCC growth tests of various cold-worked Alloy 600 steam generator tubes and compact tension specimens. As a result, PWSCC growth behavior results from the finite element prediction are in good agreement with the experimental results.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.24-27
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• 2008

For the development of superconducting fault current limiters(SFCLs) having large current capacity, we fabricated an SFCL element that consists of Bi-2212 superconductor and Cu-Ni alloy tubes. First, Ag was plated on the surface of the Bi-2212 for the enhancement of soldering process. On the Ag-plated Bi-2212 tube, a Cu-Ni alloy tube was soldered using optimized solders and soldering conditions. The BSCCO/Cu-Ni composite was processed mechanically to have a helical shape for the improvement of the SFCL characteristics. The total current path of the SFCL element was 1330 mm long with 12 turns, and had critical current of 340 A at 77 K. Finally, we carried out the fault test using the fabricated SFCL element. It showed successful current limiting performance under the fault condition of 50 $V_{rms}$ and 5.5 kA. From the results, the rated voltage of the SFCL element was decided to be 0.4 V/cm, and the power capacity was 12 kVA at 77 K. The fabrication process of the SFCL and the fault test results will be presented.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.142-145
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• 2008

A finite element analysis has been conducted to simulate direct/indirect extrusion process for AZ31 Mg alloy at various ram and die speeds. Uniaxial compression test on AZ31 Mg alloy was carried out at various strain rates and temperatures and the result was used as input data fur finite element analysis. It was found that ram speed affects the distribution of dead zone area during direct extrusion. The inhomogeneous temperature and strain distributions through the thickness direction can be simulated under the various extrusion process conditions.