Han Gil Suk

A Study on the Composition Determination of Cu Alloys by Image Processing Technology

This study examined the application of color measurement to determining the chemical composition of Cu alloys such as Cu-Zn, Cu-Sn, and Cu-Al using a color recognition system. Measured data showed that the hue intensity changed exponentially when Zn, Sn, or Al in the Cu binary systems and fitted well with an exponential equation within the experimental error. This indicates that the obtained equations can be used for predicting the compositions of Cu-Zn, Cu-Sn, and Cu-Al systems by measuring the hue intensity.

Development of Abnormal Grain Growth in Cold Rolled and Recrystallized AA 5182 Sheet

Grain growth in the cold rolled and subsequently recrystallized AA 5182 sheets was investigated by means of microstructure observations and texture measurements. Grain growth behavior strongly depends on the annealing temperatures. Grain growth hardly took place at temperatures lower than 470°C, which is attributed to a low mobility of grain boundaries. Abnormal grain growth occurred at temperatures ranging from 480 to 530°C. Annealing above 560°C gave rise to the dissolution of inhibitor precipitates, which led to normal grain growth.

Evolution of texture and strain states in AA 3003 sheet during sandwich rolling

This work focuses on the strain states of the mid AA 3003 strip sandwiched in between either AA 3003 sheets or STS 430 sheets. For that purpose, the strain states at various through-thickness layers were analyzed by measurements of crystallographic texture and by simulations with the finite element method (FEM). During sandwich rolling, the material property of outer sheets of sandwich samples played an important role in the evolution of the strain states and the corresponding texture formation. In the mid AA 3003 sheets, rolling with the harder outer sheets gave rise to pronounced through-thickness texture gradients, whereas fairly uniform strain states prevailed during rolling with the outer sheets of the same AA 3003.

A study of the effect of residual stress on magnetic properties of Fe-Ni thin film using a synchrotron X-ray

Fe20Ni80 thin films, with a thickness of 0.7 μm, were sputtered onto Si (111) single crystal and 40-μm thick Ni79Fe21 ribbons were fabricated using the rapid solidification process (RSP). Annealing of Ni-Fe thin films and ribbons at various temperatures showed that the stress induced during the sample fabrication was relieved with a subsequent decrease in coercivity, which was determined from the measurements of magnetic properties using a vibrating sample magnetometer (VSM). Decrease in coercivity of Ni-Fe thin films and ribbons were strongly dependent on annealing temperatures. Also noted was a high correlation between residual stress reduction at different annealing temperatures and coercivity that magnetic properties are strongly influenced by residual stress induced in samples.

Study on the Corrosion Resistance of High Strength Bolt, Nut and Washer Aet (S10T)Related to the Surface Treatment Conditions

The reliability of quality assurance was undermined because the bridge and building were constructed with products that have “rust” after joining the bolts at the sites. Moreover some bolts used at several sites were stored outdoors for storge, or in extreme conditions, instead of room temperature as required in the specifications. So, it was necessary to analyze how the surface treatment that enhanced corrosion-resistance affected the high strength bolts, nuts and washers. This test focuses on the correlations between the coating thickness after surface treatments and the corrosion resistance of the surface treatments (Geomet, Dacro, Green Kote, Armor Galv.). The quality characteristics of the corrosion resistance required by the KS D9502 standards were discussed. Surface treatments were implemented on the S10T sets of bolts under the same environmental factors. All corrosion resistance after surface treatments meets the criterion required by the specifications. Although the coating thickness after surface treatment should be considered as its own characteristic of the surface treatment process, Armor Galv. was the highest at 52.7 μm ~ 57.6 μm and Dacro was the lowest at 10.6 μm ~ 12.1 μm. The coating thickness after surface treatment did not affect the corrosion resistance of these high strength bolts.