• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.269-269
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• 2007

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.385-397
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• 2016

Scaffolds are essential in bone tissue engineering, as they provide support to cells and growth factors necessary to regenerate tissue. In addition, they meet the mechanical function of the bone while it regenerates. Currently, the multiple methods for designing and manufacturing scaffolds are based on regular structures from a unit cell that repeats in a given domain. However, these methods do not resemble the actual structure of the trabecular bone which may work against osseous tissue regeneration. To explore the design of porous structures with similar mechanical properties to native bone, a geometric generation scheme from a reaction-diffusion model and its manufacturing via a material jetting system is proposed. This article presents the methodology used, the geometric characteristics and the modulus of elasticity of the scaffolds designed and manufactured. The method proposed shows its potential to generate structures that allow to control the basic scaffold properties for bone tissue engineering such as the width of the channels and porosity. The mechanical properties of our scaffolds are similar to trabecular tissue present in vertebrae and tibia bones. Tests on the manufactured scaffolds show that it is necessary to consider the orientation of the object relative to the printing system because the channel geometry, mechanical properties and roughness are heavily influenced by the position of the surface analyzed with respect to the printing axis. A possible line for future work may be the establishment of a set of guidelines to consider the effects of manufacturing processes in designing stages.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.20-29
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• 2018

Ti and its alloys show the excellent corrosion resistance to chloride environments, but they show less corrosion resistance in HCl, $H_2SO_4$, NaOH, $H_3PO_4$, and especially HF environments at high temperature and concentration. In this study, we used the commercially pure titanium and Ti-6Al-4V alloy, and evaluated the effect of the manufacturing process on the electrochemical properties. We used commercial products of rolled and forged materials, and made additive manufactured materials by DMT (Directed Metal Tooling) method. We annealed each specimen at $760^{\circ}C$ for one hour and then air cooled. We performed anodic polarization test, AC impedance measurement, and Mott-Schottky plot to evaluate the electrochemical properties. Despite of the difference of its microstructure of CP-Ti and Ti-6Al-4V alloys by the manufacturing process, the anodic polarization behavior was similar in 20% sulfuric acid. However, the addition of 0.1% hydrofluoric acid degraded the electrochemical properties. Among three kinds of the manufacturing process, the electrochemical properties of additive manufactured CP-Ti, and Ti-6Al-4V alloys were the lowest. It is noted that the test materials showed a Warburg impedance in HF acid environments.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.3
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• pp.114-120
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• 2024

AA 2026, which is used as an aviation material, is an improved version of 2024 and has higher physical properties, and is a material that has the potential to be applied to supersonic aircraft to be developed in the future. However, when an aircraft exceeds supersonic speeds, the surface heats up and the material must be resistant to this. Therefore, this study confirmed the high-temperature properties of AA 2026, an aviation structural material. AA 2026, solution treated at 500℃ for 4hr, was naturally aged at room temperature for more than 168 hr. Changes in microstructure and physical properties were confirmed over several hours of exposure to 100℃, 200℃, and 300℃, respectively. As a result of microstructure analysis, there was no significant change at 100℃, and from 200℃, GPB, a strengthening mechanism, grew and formed an S Phase. It was confirmed that the S Phase grew as the exposure time increased. Through a tensile test, it was confirmed that physical properties deteriorated as the precipitates grew. However, it was confirmed that the properties were stably maintained at 100℃, which is the temperature when the speed of a supersonic aircraft is less than Mach 2.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.3-9
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• 2008

The ion implantation technology is generally used in order to improve surface mechanical properties, especially tribological properties, of engineering metals. In this study, experimental works were carried out to investigate the surface properties, such as hardness, wear quantity, wear rate and friction force, of a nitrogen ion implanted tool steel STD11 under dry condition. Specimens for the wear test were made to investigate the influences of the initial ion implantation temperature and the total ion radiation. Wear properties, such as the wear quantity and the wear rate, of the nitrogen ion implanted tool steel were considerably improved, especially under the low sliding speed and the low applied load.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.108-114
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• 1998

Development on the mechanical properties of steel sheet for the automobile body panel is very important in the BAF(Batch annealing furnace) annealing process. Because of the heat treatment method in the BAF, mechanical properties was decided on the heat treatment method of the coil. So, we tested on the development of mechanical properties according to heat treatment method at the annealing furnace using the Ax(H$_2$75%, $N_2$25%) atmospheric gas and the HNx(H$_2$4%, $N_2$96%) atmospheric gas. As a result of several investigations. We confirmed the following characteristics ; mechanical properties was changed under the influence of the annealing cycle, the heat treatment method and the atmospheric gas. And, elongation in the HNx BAF was better than the Ax BAF. Finally, most important thing in the BAF is using of proper annealing cycle in order to get a good quality.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.1
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• pp.9-16
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• 2008

It is important not only to reduce the casting defects of piston but also to improvement in the mechanical properties(hardness) of piston for the air compressor. The blow hole is typical casting defects in the conventional cast of aluminium alloy(AC8A-T6) piston. Because of the heat treatment method, mechanical properties of the aluminium alloy for piston was decided on the heat treatment method and cycle. Therefore, we tested on the development of mechanical properties and on the casting defects of piston for the air compressor in accordance with the heat treatment and casting condition. After the heat treatment and casting was carried out as several times, and was compared with the imported piston. As a result of several investigations; microstructure, hardness and casting defects of piston was changed under the influence of the heat treatment and casting method. When the cooling rate was controlled and the uni-cast method used, it bas the same mechanical properties and microstructure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.17-25
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• 2021

In this study, the mechanical properties of railway-vehicle aluminum under frame was investigated based on the metal inert gas (MIG) welding conditions. An aluminum-alloy (6005A-T6) extruded material used in the lower panel of a railway vehicle was connected through MIG welding to determine the mechanical properties of MIG welds. Argon shielding gas and filler materials, such as ER5356 and ER4043, were used as consumable welding materials. For the welding conditions of the test specimen, welding frequencies of 2.5 and 4.5 Hz were applied using the SynchroPuls function, and the root faces were 1.0 and 1.5 mm. The mechanical properties of the MIG welds were determined through tensile, bending, and fatigue tests.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.48.1-48.1
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• 2007

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.821-826
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• 2003

The Purpose of this paper is to automate the representation of manufacturing line using Petri net model. In the manufacturing cell, the line can be represented using workflow which is composed of Bill of Material (BOM) and Bill of Processes (BOP). BOP shows the precedence of processes and the relationship between assembly and disassembly. As a modeling scheme, generalized stochastic Petri net is adopted. For a problem domain with flexible manufacturing cell, Petri net model is made and behavioral properties are analyzed.