• Journal of Korea Foundry Society
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• v.28 no.6
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• pp.268-272
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• 2008

Interfacial characteristics of aluminum borate whisker reinforced AS52 matrix composite was investigated. Peak hardness of AS52 composite was obtained aging at $170^{\circ}C$ for 15h and the aging process was accelerated by the presence of the aluminium borate whisker. The MgO layer, which was the interfacial reaction product between the reinforcement and the Mg matrix, was produced with 20 nm thickness in as-cast condition. As the aging time increased, the thickness of the interfacial reaction layer increased to 50 nm in peak aged condition. The nano-indentation test results indicated that the strength of interface was improved by the aging but over-aging degraded the reinforcement and decreased the interfacial strength which resulted in the decrease of overall composite strength.

• Journal of Korea Foundry Society
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• v.28 no.3
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• pp.136-140
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• 2008

A new concept of salt core, a melting temperature of which is lower than the solidus temperature of cast alloy, was introduced to produced an integrated casting part having a complicated inner shape or requiring under-cut in high pressure die casting or squeeze casting process. The main goal of this study is to develop a new integrated net-shape forming technology using fusible core of lower melting temperature than that of a casting alloy. This integrated net-shape forming technology would be very successful and cost-effective for producing the integrated products having a complicated inner shape or requiring under-cut. The technology for measuring and evaluating a various property of fusible core such as a thermal conductivity and thermal expansion coefficient, melting temperature was established. Also, the work space can be cleaned without a pollution inducing products.

• Resources Recycling
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• v.3 no.1
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• pp.25-31
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• 1994

This paper was focused to optimize hot extrusion condition of Mg machined chips and scraps as fundamental basic research for the recycle of Mg alloy. We have been performed to extrude at $300~380^{\circ}C$ temperature range under the extrusion ratio of 25:1 after cold-pressing AZ91 Mg machined chips and scraps. AZ91 Mg ingots was used as reference materials. Microstructure observation showed that the extruded machined chips were perfectly bonded and extruded materials became fine grain size($20\mu\textrm{m}$) by recrystallization during hot extrusion. The specimens extruded from the machined chips, scraps and Mg ingot indicated tensile strength of 330MPa and the elongation of 10% at room temperature.

• Journal of Technologic Dentistry
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• v.45 no.3
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• pp.81-86
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• 2023

Purpose: This study aimed to observe the effect of laminate veneer on patient's teeth based on the manufacturing of laminate veneer restorations, which are produced by fabricating a ceramic cast body using IPS Empress, a pressure casting method and then forming the veneer by layering. Subsequently, we assessed the potential of its clinical application. Methods: This study discusses and preserves various treatment plans, such as diagnostic wax-up and treatment room diagnosis, for patients who visit the hospital to improve the appearance of teeth due to diastema of maxillary teeth, inexperienced resin filling, lack of esthetics, and external teeth. A ceramic cast body is constructed using IPS Empress, which is an effective and aesthetic restoration pressure casting method to restore the veneer with a laminate made by layering. Results: Compared with the preoperative state, the frontal view of the patient after the final restoration showed the formation of a natural smile line; the space between the central and lateral incisors was filled in synchronously with the adjacent teeth. In addition, the emergence profile is maintained by reducing the over-contour as much as possible. Conclusion: The patient's quality of life is improved by providing them with a satisfactory natural smile.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.3
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• pp.223-232
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• 2012

The purpose of this study was to investigate the effect of various thickness of porcelain on shear bond strength between metal coping and porcelain. So, various thickness of feldspathic porcelain and heat-pressed porcelain were built up and compared. 120 metal cube($4{\times}4{\times}4mm$) specimens were prepared. 60 specimens were applied to feldspathic porcelain and the others were applied to heat-pressed porcelain by 1mm, 1.5mm, 2mm, 2.5mm, 3mm and 3.5mm thickness. The measurement of shear bond strength was performed by Instron universal testing machine. The following results were obtained from this study. 1. As thickness of feldspathic porcelain increases, shear bond strength has decreased. Feldspathic specimens with 1mm porcelain thickness were significantly stronger than other feldspathic subgroups. 2. There was no significant difference of shear bond strength according to porcelain thickness in heat-pressed porcelain group. 3. In comparison between subgroups with same thickness, feldspathic porcelain group had stronger shear bond strength than heat-pressed porcelain. There were significant difference between 1mm and 3mm porcelain thickness group. 4. In almost cases, fracture surface was found on both metal and porcelain surfaces. As thickness of porcelain was increased, metal exposure was decreased.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.250-253
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• 2004

A finite element model is developed for the process of squeeze casting of metal matrix composites. The fluid flow and the heat transfer are fundamental phenomena in squeeze casting. The equations for the clear fluid flow and the flow in porous media are used to simulate the transient metal flow. To describe heat transfer in the solidification of molten aluminum, the energy equation is written in terms of temperature and enthalpy. A direct iteration technique is used to solve the resulting nonlinear algebraic equations. The cooling curves and temperature distribution during infiltration and solidification were calculated for a simplified model with pure aluminum. The developed program can be used for squeeze casting process of complex geometry, boundary conditions and processing parameter optimization.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.78-83
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• 2004

Environmental fatigue crack propagation of CF8M and CF8A steels used in the domestic PWR were investigated on the simulated PWR condition(Temperature: $316^{\circ}C$, Pressure: 15MPa). The test equipment for environmental fatigue(high temperature-high pressure loop, autoclave, load frame, measurement system) were designed. As-received and 60-year aged specimens were used in the test. To compare with environmental fatigue test, another test was performed in the air condition. The fracture surface of specimens were difficult to verify the fracture modes such as striation, intergranular crack and cleavage and so on. As the ferrite content of CF8M is increased, more particles covered fracture surface were peeled.

• Journal of the KSME
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• v.32 no.1
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• pp.46-56
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• 1992

이 글에서는 현재까지 개발된 금속복합재료의 제조공법 중에서 비교적 보편화되어 있는 분말야 금법, 가압용침법, 복합주조법 등에 대하여 소개하였고, 제조된 재료가 가지는 일반적인 기계적 성질에 대하여 설명하였다. 그리고 금속복합재료의 대표적인 응용분야와 현재 국내에서도 큰 관심을 끌고 있는 자동차엔진의 부품소재로서 금속복합재료의 응용기술에 대해 소개하였다. 국 내에서 금속복합재료의 관련 연구는 주로 학교와 연구소를 중심으로 발전되어 왔으나 근년에 자동차 산업의 비약적인 발전과 항공산업 분야에서 잠재적인 수요가 예측되면서 일부 기업체에서 응용 연구를 시작하였다. 그러나 금속복합재료의 기초 소재가 되는 경합금과 보강재의 제도기 술은 선진국에 비해 크게 뒤져 있다. 현재까지 국내에서의 연구동향은 주로 금속복합재료의 제조공정개발과 물성 평가에 치중하여 왔다. 기계공업이 발전하면서 점점 더 고기능성 소재가 요구되어지는 현황을 감안할 때 금속복합재료의 실질적 응용분야의 개척과 함께 기초 소재의 개발 연구는 시급한 과제이다.

• Composites Research
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• v.16 no.3
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• pp.75-84
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• 2003

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/A12O3/Al and Saffil/SiC/Al hybrid metal matrix composites fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, $\textrm{Al}_2\textrm{O}_3$ particles and SiC particles on the wear behavior of the composites were investigated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction(COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffi1/$\textrm{Al}_2\textrm{O}_3$/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.

• Composites Research
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• v.22 no.5
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• pp.15-23
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• 2009

The lubricant tribological characteristics of $Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) fabricated by squeeze casting method was investigated using a pin-on-disk wear tester. The wear tests of the MMCs were performed according to fiber/particle hybrid ratio in the planar-random (PR) and normal (N) orientations sliding against a counter steel disk at a fixed speed and $25\;kg_f$ loading under different sliding distances and temperatures. The test results showed that the wear behavior of MMCs varied with fiber orientation and hybrid ratio. At room temperature, the lubricant wear behavior of F20P0 unhybrid PR-MMCs was superior to that of N-MMCs while the hybrid composites exhibited the reverse lubricant wear behavior. It was also revealed that the wear resistance of PR-MMCs was superior to that of the N-MMCs due to the joint action of reinforcements and lubricant film between the friction surfaces at an elevated temperature of $100^{\circ}C$ for both fiber only and hybrid cases. In case of $150^{\circ}C$, although the trend of weight loss was similar to that of others, the wear resistance of PR-MMCs was better than that of N-MMCs for hybrid MMCs.