서지주요정보
세라믹 재료에서의 되풀이 피로 균열 성장 특성 = Characteristics of cyclic fatigue crack growth in ceramic materials
서명 / 저자 세라믹 재료에서의 되풀이 피로 균열 성장 특성 = Characteristics of cyclic fatigue crack growth in ceramic materials / 허용학.
발행사항 [대전 : 한국과학기술원, 1998].
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소장정보

등록번호

8008300

소장위치/청구기호

학술문화관(문화관) 보존서고

DME 98004

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초록정보

Cyclic fatigue crack growth behavior in four kinds of aluminas, monolithic silicon carbide and TiB2 particulates reinforced silicon carbide composite ceramic is investigated, paying special attention to crack closure, and the effect of grain size in alumina ceramics is discussed. Cyclic fatigue tests were carried out by using four-point bend specimens and the load-strain and load-differential strain curves were monitored. These curves show non-linearities due to crack closure and hysteresis loop, probably due to frictional sliding of bridging grains. The crack opening load is determined from the load- differential strain curve by using a method introduced in this study. The newly defined crack opening ratio, U*, is nearly constant with increase of the maximum stress intensity factor, Kmax, at a given stress ratio, R, and can be expressed as a function of stress ratio, R. Crack in these ceramics shows a susceptibility to cyclic fatigue loading. Fracture surfaces and morphology of crack path in these ceramics were observed by SEM. It is shown that intergranular fracture mode is dominant for the cyclic fatigue crack and grains at the crack interface are bridged with the surrounding matrix. Thus, fatigue crack growth for monolithic silicon carbide and silicon carbide composite ceramics, as well as for aluminas, can be explained by grain bridging mechanism Growth rates can be successfully described by the relationship $ da/dN = C [ΔK_eff /(1-K_max/K_IC)]^m $ proposed in this study to account for the effects of crack closure and maximum stress intensity factor. The effect of grain size on growth rates in alumina ceramics can be well explained by the above relationship. The growth rate curve based on the proposed relationship shows a sigmoidal form for ceramic materials ,like metals. Back-face elastic strain(BFS) compliance in four-point bend(FPB) specimen was calibrated by finite element analysis and experiment. The normalized BFS compliance values, E'BCW, can be well expressed with a 6th-order polynomial function of crack ratio, a/W. The back-face strain analysis shows that the gage length less than 0.2W is useful for measurement of back face strain compliance of the FPB specimen.

서지기타정보

서지기타정보
청구기호 {DME 98004
형태사항 xiii, 144 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Yong-Hak Huh
지도교수의 한글표기 : 송지호
지도교수의 영문표기 : Ji-Ho Song
학위논문 학위논문(박사) - 한국과학기술원 : 기계공학과,
서지주기 참고문헌 : p. 65-70
주제 알루미나
탄화 규소
균열 닫힘
되풀이 피로 균열 성장
입자 크기 영향
Alumina
Silicon carbide
Crack closure
Cyclic fatigue crack growth
Grain size effect
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