일반 구조용강 열간 압연 박판에 대한 K-R 곡선 결정

이억섭(Ouk Sub Lee),이계승(Gye Seung Lee),백준호(Joon Ho Baek),편장식(Jang Sik Pyun) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

Some materials exhibit a rising R curve, while the R curve for other materials is flat. The shape of the R curve depends on material behavior and, to a lesser extent, on the configuration of the cracked structure. The R curve for an ideally brittle material is flat because the surface energy is an invariant material property. When nonlinear material behavior accompanies fracture, however, the R curve can take on a variety of shapes. Five different hot-rolled thin plates are tested to investigate R-curve behavior. A special experimental apparatus is used to prevent specimen buckling.

R&D 성과창출 성공확률 예측모형 추정 및 민감도 실험설계분석 방법론 연구

박성민 한국경영컨설팅학회 2014 경영컨설팅연구 Vol.14 No.2

본 연구는 대한민국 정부의 기술혁신형 국가연구개발사업 중 하나인 “지식경제기술혁신사 업”을 대상으로 R&D 성과창출 성공확률의 예측모형을 추정하고, 추정된 예측모형의 민감도 검토를 위한 실험설계분석을 실시한다. 분석 대상 R&D 주관기관 유형은 “대기업”, “중소기 업”, 두 가지 영리기관이며, “국가R&D사업관리서비스”에 매년 등록 관리되는 여섯 가지 핵 심 R&D 성과 항목 중 특히, 특허등록, 매출액, 두 가지를 분석 대상으로 선정한다. 또한, 타 기관 간 R&D 협력 여부도 영향요인으로 본 연구에 포함한다. 일반적인 R&D 논리모형에 기 초하여 예측모형을 수립하며, 분석 샘플 n = 1,929개 종료 R&D 과제를 대상으로 분석 샘플 특성을 고려한 로짓 (Logit) 회귀분석을 실시한다. 실증분석 결과를 요약하면, 첫째, 정부지원 금액 대비 성과창출 성공확률의 양 (+)의 상관성은 확인되나, 그 영향력은 특허등록과 같은 단기적, 기술적 산출에서 매출액과 같은 중기적, 경제적 결과로 진행될수록 감소하였다. 둘째, 매출액 성과창출 여부는 직전 단계에 위치한 특허등록 창출 여부에 의존적임이 확인되었다. 셋째, “단독 R&D”와 비교할 때 “협력 R&D”에서 특허등록, 매출액 성과창출 성공확률이 더 높고, “대기업”보다 “중소기업”의 매출액 성과창출 성공확률이 더 높았다. 넷째, 민감도 실험 설계분석을 통해, 정부지원금액이 증가할수록 특허등록 성과창출 성공확률은 S자형 비선형 성장곡선 형태의 증가 추세를 명확히 보인 반면, 매출액 성과창출 성공확률은 상대적으로 선 형에 근사한 둔감한 증가 추세를 보였다. 본 연구가 제안하는 정책적 함의로서, 각 R&D 과 제별 순차적인 성과창출 유도, 타 기관 간 R&D 협력 활성화, 중소기업 친화적인 국가연구개 발사업의 기획 전개 관리 등이 바람직하다고 판단된다. 또한, 정부지원금액 증액을 통해 성 취 가능한 R&D 성과 항목은 한정적일 수 있으므로, 각 R&D 과제별 정부지원금액 규모의 적절성을 세밀히 검토하는 절차가 향후 좀 더 강화될 필요가 있다고 판단된다.

한국판 Psychopathy Checklist-Revised(PCL-R)의 구성타당도 연구

이수정,고려진,김재경 한국사회및성격심리학회 2009 한국심리학회지 사회 및 성격 Vol.23 No.3

Psychopathy has emerged as one of the most important criminal figures in the criminal justice system and criminological psychology in Korea. One reason for the surge is the need to predict criminal recidivism. Many studies have shown psychopathic traits-callousness, impulsivity, irresponsibility, lack of empathy, guilt, or remorse, and so forth-are closely related to criminal behaviors and recidivism. The PCL-R: Korean Version was accomplished the standardization by Eunkyung Jo and Soo Jung Lee in 2008. This study conducted the construct validation study of the PCL-R: Korean Version. As the result of the study, first, the PCL-R: Korean Version had significant positive correlation with Static-99(r=.48, p<.01) and MnSOST-R(r=.55, p<.01), sex offender risk assessment scales. Second, the PCL-R score significantly correlated with the total number of criminal records, the first arrest age and correctional officials' assessment of offenders. Third, follow-up prediction study by tracing recidivism was conducted to produce the optimal cutoff-score. The PCL-R score had significant positive correlation with the recidivism of the subjects. The present study identified new cutoff-score based on whether reoffending or not after release. As the result of ROC analysis, the score of 26 as an optimal cutoff-score had the highest accuracy(71.5%), sensitivity .61 and specificity .74. Finally, using the confirmatory analysis, it was yielded that 4-factor models of the PCL-R: Korean Version fitted to the current data. Therefore, we concluded that the ability of the PCL-R: Korean Version to predict recidivism is considerable, so we proposed that this assessment tool apply to Korean criminal justice system. 여러 연구들을 통해 사이코패스의 기본적인 요소- 냉담함, 충동성, 죄책감 · 후회 · 공감 부족 · 무책임성 등 -가 재 범과 밀접한 관련이 있다고 지적한다. 본 연구에서는 조은경과 이수정이 번안한 한국판 PCL-R의 재범예측을 포함한 구성타당도를 확인하고자 하였다. 연구 결과에 의하면, 우선 한국판 PCL-R은 Static-99 및 MnSOST-R 등 유사 측 정치들과 높은 상관관계를 보였다(각각 r=.48, r=.55, 모두 p<.01). 또한 PCL-R은 범죄와 관련된 변수인 범법 건수와 최초 경찰입건 연령과도 높은 상관관계를 보였으며, 죄질에 대한 또 다른 평정지표라고 할 수 있는 교도관의 수용자 평정치와도 높은 상관을 보였다. 다음으로 PCL-R의 재범 예측력 확인을 위해서 조사대상자들이 출소한 후 재범여부 를 확인하였다. 외국 연구물과 다르지 않게 국내 범죄자를 대상으로 하여서도 PCL-R 점수와 재범여부 사이에는 유 의미한 정적 상관이 나타났다(rpbis=.28, p<.01). 본 연구에서는 실제 재범여부를 바탕으로 재범 예측을 위한 새로운 변 별 기준점을 산출하였으며, 그 결과 PCL-R 총점 26점이 가장 예측력 있는 변별 기준점으로 산출되었다. 26점을 변별 기준점으로 정했을 때, 예측 정확성이 가장 높았으며(71.5%), ROC 분석 결과, 민감도는 .61 그리고 특이도는 .74로 나 타났다. 마지막으로 확인적 요인분석을 통해, 본 연구의 자료에서 4요인 모델이 적합하다는 것을 확인하였다. 따라서 우리는 한국판 PCL-R의 구성타당도는 우수하며, 형사정책 현장에서 활용될 수 있을 것이라 결론지었다.

R-Curve Behavior of Silicon Nitride at Elevated Temperatures

Sakaguchi, Shuji The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.4

R-curve, of three kinds of silicon nitride-based ceramics were measured, using single edge notched beam (SENB) method at room and at elevated temperatures, up to $1200^{\circ}C$. Stable fraacture was seen on ceramic materials with SENB specimens if the machined notch is deep enough, even though the crack resistance did not increase with crack length. Hot pressed silicon nitride did not show the rising R-curve behavior at room temperature, but it showed some rising at $1000^{\circ}C$ and above. Si3N4 reinforced with SiC whiskers showed no rising behavior at room and elevated temperatures, as it has smaller grain size, compare to the monolithic specimen. Gas pressure sintered silicon nitride had very large and elongated grains, and it showed rising R-curve even at room temperature. However, it showed some creep behavior at $1200^{\circ}C$ and the calculated R-curve on this condition did not show a good result. We cannot apply this technique on this condition for obtaining the R-curve.

SiC와 $ZrO_2$를 함유하는 ${Al_2}{O_3}$ 입자복합체의 균열저항거동 : I. 실험

박관수,이승환,이재형 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.4

Particulate composites of Al2O3/SiC, Al2O3/ZrO2 and Al2O3/ZrO2/SiC have been fabricated to investigate their R-curve behaviors and toughening mechanisms. Al2O3 containing 30 vol% SiC particles of 3${\mu}{\textrm}{m}$ showed rising R-curve behavior owing to the strong crack bridging by SiC particles. The fracture toughness reached 9.1 MPa {{{{ SQRT {m} }} at the crack length of 1000${\mu}{\textrm}{m}$. On the other hand, ZrO2-toughened Al2O3 had a high flat R-curve since it rose steeply in the short crack region due to the well known transformation toughening. For Al2O3/ZrO2/SiC composites, the R-curve behavior was similar to that of Al2O3/SiC but with slightly higher toughness. The SiC particles in this composite decreased the amount of transformable tetragonal phase to reduce the effect of transformation toughening by 50%. It was also found that the fracture toughness of this composite with two different toughening mechanisms was markedly lower than that estimated by the simple addition of two contributions.

R-Curve에 의한 SUS 410 鋼의 波壤靭成 評價

양광영,이상호 조선대학교 생산기술연구소 1988 生産技術硏究 Vol.10 No.1

The Irwin's R-Curve Method shows the function of stress intensity factor K_(RC) anti Crack extension △α. The R-Curve was plotted with contains both stable crack growth and unstable crack growth, and it is applied only when plastic behavior happen around crack tip. It is known that the R-Curve is not influenced byload control, specimen shape and initial crack length etc, but by specionen thickness and temperature. In this paper, we intend to classify the plates of SUS 410 steel as welding material and non welding material, find out fracture Toughness with the R-Curve method define the characteristics of each part of a welding specimen and investigate the influence of initial crack length. The main conclusions are as follows. (1) In non-welding material and welding material, the values of K_(RC) in welding metal part. H.A.Z part and Base metal part were 160~170, 175~200. 180~200㎏/㎜◁수식삽입▷ (원문을 참조하세요) (2) R-Curve and critical stress intensity factor K_(RC) are not influenced by the change of initial crack length with a constant thickness. (3) The curve of compliance with EB2V₁/P and α/w shows a steep positive slope.

On geometry dependent R-curve from size effect law for concrete-like quasibrittle materials

Yanhua Zhao,Jian-mei Chang,Hong-bo Gao 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.4

R-curve based on the size effect law previously developed for geometrically similar specimens (geometry type III) is extended to geometries with variable depth (geometry type I) as well as with variable notch (geometry type II), where the R-curve is defined as the envelope of the family of critical strain energy release rates from specimens of different sizes. The results show that the extended R-curve for type I tends to be the same for different specimen configurations, while it is greatly dependent on specimen geometry in terms of the initial crack length. Furthermore, the predicted load-deflection responses from the suggested R-curve are found to agree well with the testing results on concrete and rock materials. Besides, maximum loads for type II specimen are predicted well from the extended R-curve.

초고온가스로 중간 열교환기용 Alloy 617의 장시간 크리프 변형률-시간 곡선 모델링

김우곤 ( Woo Gon Kim ),윤송남 ( Song Nan Yin ),김용완 ( Yong Wan Kim ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.10

The Kachanov-Rabotnov (K-R) creep model was proposed to accurately model the long-term creep curves above 10(5) hours of Alloy 617. To this end, a series of creep data was obtained from creep tests conducted under different stress levels at 950℃. Using these data, the creep constants used in the K-R model and the modified K-R model were determined by a nonlinear least square fitting (NLSF) method, respectively. The K-R model yielded poor correspondence with the experimental curves, but the modified K-R model provided good agreement with the curves. Log-log plots of ε*-stress and ε*-time to rupture showed good linear relationships. Constants in the modified K-R model were obtained as λ=2.78, and κ=1.24, and they showed behavior close to stress independency. Using these constants, long-term creep curves above 10(5) hours obtained from short-term creep data can be modeled by implementing the modified K-R model.

Double Cantilever Beam 방법을 이용한 다결정 알루미나의 Bridging 응력효과 해석

손기선,이선학,백성기 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.5

In this study a new analytical model which can describe the relationship between the bridging stress and microstructure has beenproposed in order to investigate the microstructural effect on the R-curve behavior in polycrystalline aluminas since the R-curve can be derived via the bridging stress function. In the currently developed model function the distribution of grain size is considered as a microstructural factor in modeling of bridging stress function and thus the bridging stress function including three constants PM, n, and Cx, can be established analytically and quantitatively. The results indicate that the n value is closely related to the grain size distribution thereby providing a reliability of the current model for the bridging stress analysis. Thus this model which explains the correlation of the bridging stress distribution and microstructual parame-ters is useful for the systematic interpretation of microfracture mechanism including the R-curve behavior in polycrystalline aluminas.

SiC와 TiC 입자를 함유하는 Al₂O₃ 입자복합체의 균열저항거동과 기계적 성질

나상웅,이재형,Na, Sang-Woong,Lee, Jae-Hyung 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.4

Particulate composites of $Al_2O_3$/TiC/SiC, $Al_2O_3$/TiC and $Al_2O_3$/SiC have been fabricated by hot pressing and their R-curve behaviors and mechanical properties were investigated. $Al_2O_3$ containing 30 vol% TiC particles showed higher toughness by 8% than that for monolithic alumina and its fracture strength was increased significantly by approximately 30%. On the other hand, the addition of 30 vol% SiC of $3{\mu}m$ in $Al_2O_3$ decreased the fracture strength slightly but induced a rising R-curve behavior owing to the strong crack bridging of SiC particles. In case of $Al_2O_3$/TiC/SiC, arising R-curve behavior was also observed and the fracture toughness reached 6.6 MPa${\cdot}\sqrt{m}$ at the crack length of $1000{\mu}m$, which was lower than that of $Al_2O_3$/SiC, however, while the fracture strength was higher by about 20%. The fracture toughness seemed to be decreased as smaller TiC particles roughened the SiC interface and pullout of the SiC particles for crack bridging became less active. $Al_2O_3$/TiC/SiC, $Al_2O_3$/SiC 및 $Al_2O_3$/TiC 복합체들을 고온가압소결로 제조하여 이들의 균열저항거동과 기계적 성질을 비교해 보았다. $Al_2O_3$에 $0.8{\mu}m$의 TiC가 30vol% 첨가된 $Al_2O_3$/TiC는 단일체 $Al_2O_3$와 비슷한 균열저항거동을 보이며 파괴인성은 전반적으로 10% 이내의 증가를 보이는데 그쳤지만 강도는 약 30% 증가하였다. $Al_2O_3$에 $3{\mu}m$ SiC가 30vol% 첨가된 $Al_2O_3$/SiC는 SiC 입자의 균열 접속으로 인해 증가하는 균열저항거동을 뚜렷이 보이면서 파괴인성이 긴 균열에서 약 75% 증가하였으나 강도는 다소 감소했다. $Al_2O_3$/TiC에 SiC 입자가 30 vol% 첨가된 $Al_2O_3$/TiC/SiC 복합체의 경우 단일체 $Al_2O_3$에 비해 긴 균열 거리에서 파괴인성이 50% 이상 증가된 6.6 MP${\cdot}\sqrt{m}$에 이르렀으며 강도 값도 약 20% 상승하였다. 그러나 큰 SiC 입자의 첨가로 인해 TiC 입자만 첨가된 $Al_2O_3$/TiC 복합체보다는 강도가 다소 낮았다. 또한 SiC 입자만 첨가된 $Al_2O_3$/SiC 복합체보다는 파괴인성이 다소 낮았는데, 이는 작은 TiC 입자들이 SiC 입계를 거칠게 만들어 균열접속을 일으키는 SiC 입자의 뽑힘 현상을 방해하였기 때문이다.