서지주요정보
의탄성회복현상으로 해석된 Cyclic creep 변형기구의 규명 = (The) interpretation of cyclic creep deformationmechanism in terms of the anelastic recovery
서명 / 저자 의탄성회복현상으로 해석된 Cyclic creep 변형기구의 규명 = (The) interpretation of cyclic creep deformationmechanism in terms of the anelastic recovery / 진근찬.
저자명 진근찬 ; Jin, Keun-Chan
발행사항 [서울 : 한국과학기술원, 1982].
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등록번호

4101889

소장위치/청구기호

학술문화관(문화관) 보존서고

DMS 8202

SMS전송

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초록정보

The cyclic creep behaviors have been studied with various stress frequencies, amplitudes and unloading times in the temperature range of 0.4-0.5 $T_m$. The cyclic creep conditions such as peak stress, amplitude and frequency were kept constant during creep deformation. Creep tests have been carried out at stress frequency ; f=0.2-3 cpm, ratio of amplitude to peak stress ; Δσ =0-0.9 and ratio of unloading time to a period ; $t_u/t_p=0-0.7$. The creep rate and activation energy for creep deformation in the steady state have been measured from each creep test. For high peak stress, frequency and large amplitude, creep rate ($&εgrave;$_c$) was noticeably higher and activation energy for cyclic creep($Q_c$) decreased in the range of cyclic creep acceleration, while those changed slightly in the range of retardation. The effect of varying the unloading time to a period ($t_u/t_p$) on the ratio of creep rate ($&εgrave;$_c/$&εgrave;$_s$) and activation energy were examined at the condition of constant frequency and amplitude in the vicinity of 0.4 $T_m$. The activation energy and the ratio of creep rate were minimum and maximum at $t_u/t_p$ 0.5, respectively. These indicate that the recovery process during the unloaded period (anealstic recovery) operates more effectively than that during the loaded period (dynamic recovery). After specimens were allowed to attain the steady state, unloading tests were carried out and anelastic strain was measured with unloading time. The activation energy for anelastic deformation ($Q_a$) was about the same as that for cyclic creep ($Q_c$). The difference in activation energy for static and cyclic creep ($ΔQ=Q_s-Q_c$) were formulated in terms of unloading time (half a period) and amplitude. $Δ{Q}=0.9V(Δσ- σ_o) exp(-Kt)$ ΔQ is an additionally mechanical work term which increased with amplitude and frequency. The calculated values of ΔQ were nearly consistent with experimental values. From the test results of stress mode change in differential creep tests, it seems clear that the accelerated creep rate is associated with the development of softer substructure which allows more creep deformation by anelastic recovery in the cyclic creep. Based on a consideration of mechanistic model mentioned above, it may be concluded that cyclic creep deformation is controlled by anelastic recovery occurred under repeated stress.

서지기타정보

서지기타정보
청구기호 {DMS 8202
형태사항 iv, 77 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Keun-Chan Jin
지도교수의 한글표기 : 남수우
지도교수의 영문표기 : Soo-Woo Nam
학위논문 학위논문(박사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 74-77
주제 Internal friction.
Deformations (Mechanics)
크리프. --과학기술용어시소러스
활성화 에너지. --과학기술용어시소러스
의탄성. --과학기술용어시소러스
반복 응력. --과학기술용어시소러스
Creep.
Recovery of metals.
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