• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.312-318
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• 1992

Two kinds of alumina specimens with different grain size (1 and 51 $\mu\textrm{m}$) but same density were prepared by hot-pressing. Fracture strength and fracture toughness of these specimens at low strain rate, sonic velocity, and elastic property were evaluated. Ballistic performance against Cal. 50 AP projectile was characterized by thick-backing method by using A16061-T6 reference block. Mechanical properties measured at low strain rate showed that the specimen with samll grain (SG) were better than specimen with large grain (LG). Fracture strength and fracture toughness of LG specimen were 131 MPa and 3.01 MPa{{{{ SQRT { m} }}, but those of SG specimen were 349 and 4.23, respectively. Sonic velocity and elastic properties of these specimen were similar, but bulk velocity and bulk modulus were different at amount of 4 and 9%. The tendency of ballistic performance was not consistent with the mechnaical properties at low strain rate. The ballistic performance based on quantitative efficiency revealed that the LG specimen (5.13) was ballistically better than the SG specimen (4.00) in spite of their lower mechanical properties.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.950-955
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• 2005

This paper describes an intelligent filler wire feeding device which can control 3- dimensional seam tracking and the filler wire speed by measuring the gap position and the joint gap width in laser welding. By means of visual sensor controlled filling the missing material into the joint gap and 3 dimensional seam tracking, lineup errors from manufacturing tolerances and the repeatability of lineup jigs and weld robot can be balanced and at an even seam quality which avoids weld defects. In this paper, we assessed weld quality in 2mm sheets of A16061 which had various gap width by using the intelligent filler wire feeding device.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2070-2077
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• 2001

An experimental investigation of the effect of composite patching repair was conducted to characterize the fatigue crack growth behavior in thick A16061-T6 (6mm) panels with single bonded patch by fiber reinforced composite patch. Four patch lengths and no patch plate were examined. An analytical procedure, involving three-dimensional finite element method having three layers to model cracked aluminum plate, epoxy by adhesive and composite Patch, is calculated the stress intensity factors. From the calculated stress intensity factors, the fatigue crack growth rates are obtained. At the single patching type, different fatigue crack growth ratios through the palate thickness were investigated by using the experimental and analytical results. The results demonstrated that there was a definite variation in fatigue life depending on the size of composite patch. While crack reached the patch end, retardation of crack growth was also revealed in the bonded repair.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1480-1487
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• 2005

Metal matrix composites(MMCs) have been rapidly becoming one of the strongest candidates for structural materials fur many high temperature application. However, among the various high temperature environments in which metal matrix composites was applied, thermal shock is known to cause significant degradation in most MMC system. Due to the appreciable difference in coefficient of thermal expansion(CTE) between reinforcement and metal matrix, internal stresses are generated following temperature changes. Infernal stresses affect degradation of mechanical properties of MMC by causing microscopic damage in interface and matrix during thermal cycling. Therefore, the nondestructive evaluation on thermal shock damage behavior of SiC/A16061 composite has been carried out using ultrasonics. For this study, SiC fiber reinforced metal matrix composite specimens fabricated by a squeeze casting technique were thermally cycled in the temperature range 298$\~$673 K up to 1000cyc1es. Three point bending test was conducted to investigate the efffct of thermal shock damage on mechanical properties. The relationship between thermal shock damage behavior and the propagation characteristics of surface wave and SH-ultrasonic wave was discussed by considering the result of SEM observation of fracture surface.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.292-298
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• 2001

An experimental investigation of the effect of composite patching repair was conducted to characterize the fatigue crack growth behavior in thick A16061-T6 (6mm) panels with single bonded patch by fiber reinforced composite patch. Four patch lengths and no patch plate were examined. An analytical procedure, involving three-dimensional finite element method having three layers to model cracked aluminum plate, epoxy by adhesive and composite patch, is calculated the stress intensity factors. From the calculated stress intensity factors, the fatigue crack growth rates are obtained. At the single patching type, different fatigue crack growth ratios through the plate thickness were investigated by using the experimental and analytical results. The results demonstrated that there was a definite variation in fatigue life depending on the size of composite patch. While crack reached the patch end, retardation of crack growth was also revealed in the bonded repair.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.22-27
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• 2007

This study aims to find the optimal cutting conditions, when ellipse mirrors consisted Aluminum alloy were made it the Millimeter-Wave Interferometer System mirror with several tools on the High-Speed Machine. Machining technique for precision machining characteristics of ellipse mirrors consisted Al6061 matter by Ball endmill is reported in this paper., Results of machining on the High-Speed Machine(using NCD(Natural Crystalline diamond), WC and coated TiAlN ${\phi}6mm$ ball endmill tool) had measurement of surface roughness and form accuracy with cutting conditions(the Feed rate, the Depth of cut and the Cutting speed). the Millimeter-Wave Interferometer System ellipse mirror had been machined foundational precision machining characteristics of aluminum.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.38-45
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• 2004

Ultrasonic signals transmitted through adhesively bonded plates were used to evaluate parameters related to attenuation and frequency in the adhesively bonded joint. The kinds of bonding materials with a different bonding thickness of constant pressure were used. And ultrasonic diagnosis was evaluated by p-wave sensor of 10MHz. FFT has been performed to determine bond-layer parameters such as effective thickness and frequency for adhesively bonded joint of A16061 plates in comparison with measured to theoretical ratios. When variable thickness exists, the ultrasonic spectrum was changed the frequency wave. The more materials thickness and the higher the frequency, the larger shift was observed. Measured ratios for cases of bond thickness and variety bonding materials are then used to determine bond parameters. The results show that the technique can be applied to the characterization of adhesively bonded joint.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.7 s.184
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• pp.59-66
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• 2006

In laser welding, automatic seam tracking is important to adjust the laser head position in real time as it moves along the seam. Also if the joint gap is occurred, filling the missing material into the joint gap is necessary to prevent welding defects and bad welding quality. In general, the joint gap width is not constant along the seam due to a variety of reason. So it is essential to control the filler wire speed into the joint gap to acquire good welding quality. This paper describes an intelligent filler wire feeding device which can control 3-dimensional seam tracking and the filler wire speed by measuring the gap position and the joint gap width in laser welding. We call this device as Smart Micro Control system(SMC). To achieve this objective, we assessed weld quality in 2mm sheets of A16061 which had various gap width by using the developed device. From the experimental results, It was found the possibility that the developed device could be used in welding various 3-dimensional structures.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.139-145
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• 2010

Bending fatigue of aluminium alloy was characterized by acoustic nonlinearity of narrow band laser-generated surface wave. The higher harmonic components generated intrinsically by arrayed line laser beam were analyzed theoretically and acoustic nonlinearity was measured successfully on the surface of fatigue damaged aluminium 6061 alloy. The acoustic nonlinearity increased as a function of fatigue cycles and has close relation with damage level. Consequently, the nonlinear acoustic technique of laser-generated surface wave could be potential to characterize surface damages subjected to fatigue.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.254-257
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• 2007

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $200^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $200^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.