• 한국세라믹학회지
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• 제28권8호
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• pp.654-660
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• 1991

Stabilized Zirconia (3 mol % Yttria, 3Y-TZP) was joined with intermetallic compound NiTi which has similar thermal expansion coefficient. The optimum bonding condition was determined by the Taguchi Method. Under the optimum bonding condition, the 4-point bending strength was as high as 400 MPa. bonding interfaces were examined by optical microscope, SEM, and TEM; reaction products were identified by XRD and TEM, The relationship between products and strength was examined.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.103-108
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• 2000

Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.

• 열처리공학회지
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• 제7권3호
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• pp.160-168
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• 1994

This was studied about mechanical characteristic of AC4A/SiCw 10-30% reinforced composites. Tensile strength of pressed base metal(base metal) with SiCw preform was higher than without pressed base metal(AC4A). If SiCw whisker volume fraction was increased, tensile strength at room temperature was increased. And tensile strength of SiCw 30% was about $35kg/mm^2$. Tensile strength of SiCw 30 % $400^{\circ}C$ at same time aging was the most excellence, about $40kg/mm^2$. The fracture energy value of composite material at three point bending test was higher than AC4A. Dislocation at matrix of composite material was evenly distributed. But dislocation around whisker of composite material was more existed than matrix. The reasom was thought of pile-up around whisker.

• 구강회복응용과학지
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• 제16권3호
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• pp.221-227
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• 2000

Provisional fixed partial dentures(FPDs) are an important part of many prosthodontic treatment procedures. These provisional fixed prostheses must fulfill biologic, mechanical, and esthetic requirements to be considered successful. Consideration of all these factors and requirements are important because provisional resin restorations may be worn over a long period to assess the results of periodontal and endodontics therapies, and also during the restorative phase of implant reconstructive procedures. This in vitro study examined flexual strength of four resins commonly used for fixed provisional prostheses. The effects of polymerization conditions were also evaluated. The four resins tested were : Caulk Temporary bridge resin(L.D. Caulk Co. Dentsply International Millford), Jet(Lang Dental Mfg. Co. Chicago. ILL. U.S.A), Alike (Coe Laboratories. Inc. Chicago. ILL. U.S.A) and Tokuso Curefast (Coe Laboratories. Inc. Chicago. ILL. U.S.A) The test specimens were 65mm long, 14mm wide, and 3.5mm thickness. 10 specimens of four resins were cured for 15 minutes at atmospheric pressure and 10 specimens of four resins were cured at an additional pressure of approximately 20 psi. A total of 80 specimens were prepared. The flexual strength was determined by three-point bending test. Data were analysed with the Paired samples T-test and Tukey student-range test Within the limitations imposed in this study, the following conclusions can be drawn : 1. Under the condition of bench curing, Caulk Temporary bridge resin showed the highest flexual strength. In decreasing order, the flexual strength of the other materials was as follows : Jet, Tokuso Curefast, Alike, and Caulk Temporary bridge resin demonstrated significantly higher strength than other resins. 2. Under the condition of pressure curing, Jet showed the highest flexual strength. In decreasing order, the flexual strength of the other materials was as follows : Caulk Temporary bridge resin, Tokuso Curefast, and Alike. There were all statistically significant differences among four resins 3. There was a statistically significant difference between bench- and pressure-cured specimens in all four materials.

• 한국세라믹학회지
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• 제30권4호
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• pp.309-315
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• 1993

Gas pressure sintering is a promising process in various densification methods of high strength Si3N4 ceramics. Environmental influences on gas pressure sintering of Si3N4 was investigated with the variationof packing powder, specimen container and N2 gas pressure. The specimens had higher density, larger weight loss and inhomogeneous color in graphite specimen container than in SN26 crucible. The variations of sintering densities in various packing powders (Si3N4, SN26, AlN, BN) were very small but SiC powder was synthesised in graphite crucible with Si3N4 packing powder, aluminium oxynitride compounds were synthesised in SN26 crucible with AlN packing power. Also N2 gas pressure over 20kg/$\textrm{cm}^2$ reduced the densification of Si3N4 in one step-gas pressure sintering. As the result of two step-gas pressure sintering at 700kg/$\textrm{cm}^2$ for 15min., relative density of 99.9% and 3-point bending strength of 1090MPa and dense microstructure of 3~4${\mu}{\textrm}{m}$ grain size were obtained.

• 한국안전학회지
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• 제25권3호
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• pp.34-39
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• 2010

Unidirectional Carbon Fiber Reinforced Plastics (CFRP) are advanced materials which combine the characteristics of the light weight, high stiffness and strength. For those reasons, the use of the unidirectional CFRP has increased in jet fighters, aerospace structures. However, unidirectional CFRP composites have a lot of problems, especially delamination, compared with traditional materials such as steels and aluminums, and so forth. Therefore, the interlaminar fracture toughness for a laminate CFRP composite is very important. In this study, The mode II interlaminar fracture toughness was measured by using center notched flexure(CNF) test specimen. The CNF specimens using unidirectional carbon prepreg were fabricated by a hot-press with the gage pressure and temperature controller. And three kinds of a/L ratio was applied to these specimens. Here, we discuss the relations of the crack growth and the mode II interlaminar fracture under the four point bending CNF test. From the results, we shows that mode II interlaminar was occurred when the more $a_0$/L ratio, the less load. And $G_{IIC}$ also were obtained as 5.33, 2.9 and $0.58kJ/m^2$ according to $a_0$/L ratio=0.2, 0.3 and 0.4.

• 한국세라믹학회지
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• 제39권7호
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• pp.675-679
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• 2002

강화유리를 제조하기 위해서, 디스플레이 기판으로 사용되는 soda-lime-silicate 유리를 대상으로 단일이온교환 특성에 대하여 3점곡강도와 잔류응력을 조사하였다. 단일이온교환을 47$0^{\circ}C$에서 1시간 처리 후, 45$0^{\circ}C$에서 24시간 행하였을 때, 62.5$\times$10$_{6}$ kg/$m^2$의 최대 강도 값을 나타내었다. 또한, 곡강도 측정 후 얻어진 시편의 파단면에 존재하는 잔류응력층을 파괴분석을 통하여 관찰한 결과, 이 잔류응력층이 외부하중에 대한 탄성 변형에너지를 흡수하여 유연성을 증가시킴을 알 수 있었다 또한, 탄성변형에너지 흡수는 만곡변화, 균열가지수 및 취성특성 분석에서도 관찰되었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.25-28
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• 2006

This paper dealt with the LPS process for the development of high performance SiC materials, based on the detailed analysis of their microstructure and mechanical properties. The submicron SiC powder was used for the fabrication of LPS-SiC materials. A mixture of $Al_2O_3$ and $Y_2O_3$ particles was also used as a sintering additive in the LPS process. LPS-SiC materials were fabricated at different temperatures, using various additive composition ratio ($Al_2O_3/Y_2O_3$). The total amount of additive materials ($Al_2O_3+Y_2O_3$) was fixed as 10 wt%. The characterization Of LPS-SiC materials was investigated by means of SEM, XRD and three point bending test. The LPS-SiC material represented a relative density of about 98 % and a flexural strength of about 800MPa, when it was fabricated at the temperature of $1820^{\circ}C$ and the additive compositional ratio of 1.5.

• 한국세라믹학회지
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• 제34권7호
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• pp.758-766
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• 1997

Non-brittle fracture behaviour of the two composite structures made of two different brittle materials was investigated using 3-point bending test. First, the layered and fibrous macro-composites were fabricated using the material easily formed, yet showing a brittle fracture behaviour similar to ceramics. The layered and fibrous Al2O3 /Al2O3 composites with weak interface were also fabricated using plate of 2 mm thickness and rod of 3 mm diameter respectively. Comparison of the mechanical properties between these two structures was performed in the lights of flexural strength and work of fracture for the composites consisting of Al2O3 and simulated materials respectively. The strength ratio of layered structure to the monolith of same volume was 0.6 and the ratio of fibrous one was about 0.2 for the composites made of simulated brittle material. The ratio of the work of fracture of the fibrous to the layered was 0.47. For Al2O3/Al2O3 composites, the strength ratio of layered and fibrous structures to the monolith with same volume were about 0.6 and 0.2 respectively. The ratio of work of fracture of the fibrous to the layered was 0.6. These confirmed that the layered structure was superior to the fibrous one in terms of flexural strength and work of fracture.

• 대한치과교정학회지
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• 제33권2호
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• pp.131-140
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• 2003

본 연구는 전기도금을 이용하여 각형 선재의 굵기를 증가시킨 후 기존의 선재와 물성을 비교함으로써 이의 임상적 적용 가능성을 알아보고자 시행되었다. 한 변의 길이가 0.016 인치인 정사각형 스테인레스 스틸 교정용 선재에 니켈 전기도금을 시행하여 굵기를 0.001 인치 증가시켜 한 변의 길이가 0.017인치인 정사각형 선재로 만들었고 도금층의 밀착성을 증진시키기 위해 $400^{\circ}C$의 전기로에서 10분간 열처리를 시행하였다 시편의 물성변화를 알아보기 위하여 전기도금을 이용하여 제작된 15개의 시편을 실험군(016P군)으로, 기존의 0.016 인치 (016군), 0.017 인치 (017군) 스테인레스 스틸 교정용 선재를 대조군으로 설정한 후 3점 굴곡 시험과 비틀림 시험을 시행하여 다음과 같은 결과를 얻었다. 1. 3점 굴곡 시험 결과 0l6P군이 016군에 비해 강성과 항복강도, 극한강도 모두 증가하는 경향을 보였으며, 강성과 극한강도는 통계적으로 유의한 차이가 있었다(p<0.05). 2. 3점 굴곡 시험 결과 0l6P군이 017군보다 강성과 항복강도, 극한강도 모두 낮은 경 향을 보였으며, 강성은 통계적으로 유의한 차이가 있었다(p<0.05). 3. 비틀림 시험 결과 016P군이 016군에 비해 비틀림 강성과 항복 비틀림 모멘트, 최대 비틀림 모멘트 모두 높았으며, 통계적으로 유의한 차이가 있었다(p<0.05). 4. 비틀림 시험 결과 016P군이 017군에 비해 비틀림 강성과 항복 비틀림 모멘트, 최대 비틀림 모멘트 모두 낮은 경향을 보였으며, 이 중 항복 비틀림 모멘트와 최대 비틀림 모멘트에서 통계적으로 유의한 차이가 있었다(p<0.05). 이상의 결과를 요약해 보면 각형 선재에 도금을 시행하여 굵기를 증가시키고 물성이 증가될 수 있음을 알았다. 비록 도금을 시행한 016P군이 기존의 017군보다 강성이 낮았으나 이는 반대로 016P군이 017군보다 탄성이 높음을 나타내며 토크조절이 부족한 경우 브라켓 슬롯에 쉽게 삽입되어 교정력을 발휘할 것으로 기대된다.