Dong-Joo Yoon

An Analysis on the Properties of Designed High-Strength Ti Alloys Using the Density Functional Theory Method

Titanium and its alloys offer the highest strength, excellent corrosion resistance and the highest strength to weight, but their disadvantage is a higher cost. This study was made to obtain useful information on their high-strength properteis for designing beta type titanium alloys using the DV-Xα method. To lower prices low-cost elements (Mo, Al, Fe) were used. The Mechanical properties of these alloys are compared to commercial alloys in order to investigate the characteristics of the alloys. The results showed strength of the titanium alloys was somewhat higher (30-90 MPa) than conventional alloys. †(Received September 28, 2012)

Surface Characterization According to the Bias Voltage of the TiAgN Coating Film Layer Formed by the AIP Process

The implanting of metal products is performed with numerous surface treatments because of toxicity and adhesion. Recently, the surface modification of metal products has been actively studied by coating the surface of the TiC or TiN film. We prepared a Ti(10%)Ag Target which may be used in dental oral material by, using the AIP(arc ion plating) system TiAgN coating layer that was deposited on Ti g.23. The purpose of this study was to establish the optimal bias voltage conditions of the coated TiAgN layer formed by the AIP process. The TiAgN coatings were prepared with different bias voltage parameters (0V to -500V) to investigate the effect of bias voltage on their mechanical and chemical properties. The SEM(scanning electron microscope), EDS(energy dispersive X-ray spectrometer), XRD(X-ray diffraction), micro-hardness, and potentiodynamic polarization were measured and the surface characteristics of the TiAgN coating layers were evaluated. The TiAgN coating layer had different mechanical characteristics based on the bias voltage, which also showed differences in thickness and composition.

A Study on the Properties of Design for the Biomaterial Ti-Ag-Zr Alloys Using DV-Xα Molecular Orbital Method

Abstract Ti and Ti alloys have been extensively used in the medical and dental fields because of their good corrosionresistance, high strength to density ratio and especially, their low elastic modulus compared to other metallic materials. Recenttrends in biomaterials research have focused on development of metallic alloys with elastic modulus similar to natural bone,however, many candidate materials also contain toxic elements that would be biologically harmful. In this study, new Ti basedalloys which do not contain the toxic metallic components were developed using a theoretical method (DV-Xα). In addition,alloys were developed with improved mechanical properties and corrosion resistance. Ternary Ti-Ag-Zr alloys consisting ofbiocompatible alloying elements were produced to investigate the alloying effect on microstructure, corrosion resistance,mechanical properties and biocompatibility. The effects of various contents of Zr on the mechanical properties andbiocompatibility were compared. The alloys exhibited higher strength and corrosion resistance than pure Ti, had antibacterialproperties, and were not observed to be cytotoxic. Of the designed alloys’ mechanical properties and biocompatibility, the Ti-3Ag-0.5Zr alloy had the best results.Key wordsbiomaterial, Ti alloy, DV-Xα method, mechanical properties, biocompatibility

Modeling and Analysis of Radiation Patterns of High Power LED Package for Luminarie

Today`s research has been focused on changing the light source from filament to LED for luminarie illumination to overcome the shortcoming of a filament. The purpose of this research is to make an appropriate high power LED package structure for luminarie. We simulated radiation patterns of the various structures by the ray tracing simulator (Light Tools), and also analyzed the radiation patterns using an LED test system (OL770). As we increased an inner reflector angle, the radiation pattern split into two peaks and the angle between two peaks became larger. In addition, when we increased an outer reflector angle, the angle between side peaks gradually decreased, while it increased again when the angle reach . These results could be understood from the ray tracing of the light reflected from two reflectors. We made the high power LED package for luminarie on the condition of the optimized structure which was made by ray tracing simulation results, and we measured the radiation patterns by using an LED test system, and these results were well matched to the simulation results.

Microstructure and Mechanical Properties of A3003 Aluminium Alloy Welds by Heat-treatment

The present work was aimed to examine the variation of microstructure and mechanical properties by annealing(, ) in A3003 Al alloy welded pipes. The A3003 Al alloy pipes with 34 mm in external diameter and 1.3 mm in thickness were manufactured by high frequency induction welding with the V shaped convergence angle and power input 50 kW. The tensile and yield strength decreased with increasing the annealing temperature remarkably, but elongation increased remarkably. Vickers hardness in welds decreased with increasing the annealing temperature remarkably. The primary intermetallic compound of was precipitated in welds as the same base metal. In a certain experimental condition, the welds line in A3003 alloys disappeared at for 2 hr because of the same mechanical property and structure between welds and base metal.