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KMID : 1035320220490030111
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Korean Society for Dental Materials
2022 Volume.49 No. 3 p.111 ~ p.120
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Fracture behavior of ceramic restorative materials in the active environments
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Bae Tae-Sung
Lee Min-Ho
Yoon Sun-Jung
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Abstract
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When tensile stress is applied to metal, the fracture occurs after the shape changes due to plastic deformation, and also the crack velocity resulting from defects is very slow, so that the defects do not significantly affect the fracture behavior. Ceramic materials, on the other hand, are brittle and rarely plastic deformation so the stress concentration occurs at the crack tip of the most dominant flaw in the material, so that the crack progresses rapidly and the defect greatly affects the fracture. Therefore, when evaluating the fracture behavior of ceramic materials, a measurement of the fracture toughness is required, considering the effects of the defect. Since ceramic materials have excellent resistance to water and erosion is difficult to occur even by acids or alkalis, their strength is not significantly reduced even after prolonged exposure to these environments. However, in the active environment in which erosion due to stress corrosion proceeds, a problem arises in which the survival life is shortened. If crack growth caused by stress corrosion occurs in the active environment, it is not a problem because the crack growth caused by stress corrosion is very slow when the stress level is low compared to the strength. However, when the level of applied stress level is high compared to the strength, the crack growth is fast and the service life may be greatly reduced, so the use of a ceramic materials having high strengths are required.
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KEYWORD
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Flexural strength, Fracture toughness, Slow crack growth
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