• Journal of the Korean Ceramic Society
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• v.29 no.8
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• pp.651-659
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• 1992

Fracture toughness of alumina was determined by IF, IS, DT, SEPB methods, and the data were inter-compared. Round robin test on IF and IS methods was also conducted under the participitation of 4∼5 domestic institutes. Fracture toughness data determined by IF, IS, DT methods were similar, while those by SEPB method were smaller. Variation of toughness data determined by IS method using 98N of indentation load was significantly small compared to those determined by any other methods. Round robin test results showed that toughness data determined by IF method at various institutes do not coincide each other, while those by IS method do well coincide. Thus, it was concluded that inter-confidence on fracture toughness data, if determined by IS method at all institute, can be established between institutes.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.129.1-129.1
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• 2005

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.311-322
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• 1998

American Society for Testing and Materials (ASTM) standard test method PS 070-97 has been created for measuring fracture toughness of advanced ceramics. PS 070-97 includes three test methods which use beams in bending: chevron notch (CNB), single-edged precracked beam (SEPB), and surface crack in flexure (SCF). Supporting data has been collected through several Versailles Advanced Materials and Standards round robins. This paper discusses the evolution of the standard including the rationale for the choice of the three methods and the specifications in the standard. Progress on Standard Reference material 2100 which will have certified values of fracture toughness is presented.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.4-9
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• 2006

To test the fracture toughness of alumina; a Surface-Crack-in-Flexure (SCF) method, a Single-Edge-Precracked-Beam (SEPB) method and a Single-Edge-V-Notched-Beam (SEVNB) method were used at crosshead rates ranging from 0.005 mm/min to 2 mm/ min and relative humidity ranging from $15\%\;to\;80\%$. The results show that the fracture toughness tested by the SCF method increases with either an increasing loading rate or decreasing relative humidity; in contrast, the toughness by the SEPB method and the SEVNB method does not depend on the loading rate or the relative humidity. Theoretical analysis of the way slow crack growth affects the apparent fracture toughness indicates that the three testing methods have different effects with respect to the loading rate and the relative humidity; moreover, these differences are attributable to differences in the size of the cracks or notches.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.118-121
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• 2015

최근 세계적으로 이상기후나 지진 등의 자연재난이 증가하고 그 피해도 대형화되고 있는 추세로, 선진 여러 나라는 국민의 생명과 재산 보호를 위해 다양한 매체를 활용한 신속한 재난 예보와 지능적이고 맞춤식 경보 전달을 위해 노력하고 있다. 본고에서는 지능 맞춤형 경보발령 관련 해외 동향을 소개하고, 통합경보시스템의 구조와 통합경보시스템에서의 지능형 경보발령과 맞춤형 경보발령에 대한 정의, 통합경보시스템에서 지능 맞춤형 경보발령을 적용하는 방법에 대해 제시하였다.

• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1266-1273
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• 1998

Al2O3/(5~20vol%)LaAl11O18 composites in which the second phase was dispersed with a elongated grain shape were fabricated using Al2O3 and La2O3 composition by hot-pressing. In order investigate the in-fluence of LaAl11O18 on the toughening of LaAl11O18 on the toughening of Al2O3 matrix composites AE(acoustic emission) analysis was con-ducted together with an evaluation of fracture toughness using of SEPB technique. The degree of AE events occurred in composites were more than those in monolithic alumina. The occurrences of AE event increased with increasing the amount of LaAl11O18 phase in the Al2O3/LaAl11O18 composite is two times higher compared to monolithic alu-mina. The main toughening mechanism was attributed to the bridging of LaAl11O18 grains at tip of pro-pagating crack.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.197-199
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• 2015

세계적으로 이상기후나 지진 등의 자연재난이 증가하고 그 피해도 대형화되고 있으며, 선진 여러 나라는 국민의 생명과 재산 보호를 위해 다양한 매체를 활용한 신속한 재난 경보 전달을 위해 노력하고 있다. 본고에서는 재난이 발생한 경우 광고매체로 활용되고 있는 디지털 사이니지를 통해 사람들에게 재난정보를 효과적으로 전달하여 대피하는데 도움을 주기 위한 정보 제공을 위해 디지털 사이니지를 통한 재난경보 표시 방법을 제시하였다.

• Journal of the Korean Ceramic Society
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• v.34 no.11
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• pp.1129-1138
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• 1997

Al2O3/20 vol%YAG composite containing equiaxed grains and Al2O3/20 vol%LaAl11O18 composite containing elongated grains were fabricated using Al2O3-Y2O3 composition and Al2O3-La2O3 composition, respectively, by hot-pressing. In order to investigate the influence of microstructural control of second phase on toughening effect of toughened ceramic composites, AE (acoustic emission) measurements have been coupled with fracture toughness experiments(SENB and SEPB method). A separation of the fracture toughness and analysis of toughening mechanism was possible using the AE technique. The fracture toughness of hot-pressed materials was estimated to be 3.2 MPam0.5 for monolithic alumina, 4.7 MPam0.5 for Al2O3/20 vol%YAG composite and 6.2 MPam0.5 for Al2O3/20 vol%LaAl11O18 composite. In monolithic Al2O3, toughening does not occur as a result of either microcracking or grain bridging, whereas, composites exhibit toughening effects by both microcracking in the frontal zone and gain bridging in the wake zone, resulting in an improvement of fracture toughness as compared with monolithic Al2O3. The fracture toughness of Al2O3/20 vol%LaAl11O18 composite is higher than that of Al2O3/20 vol%YAG composite. It may be attributed to the elongated microstructure of Al2O3/20 vol%LaAl11O18 composite, resulting relatively greater bridging effect.