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제강 슬래그 잔골재가 혼입된 초속경 시멘트 기반 스마트 보수재료의 전기역학적 특성
김태욱,김민경,김동주,Tae-Uk Kim,Min-Kyoung Kim,Dong-Joo Kim 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 논문집 Vol.27 No.4
This study investigated the electromechanical properties of cement based smart repair materials (SRMs) according to the different amounts of fine steel slag aggregates (FSSAs). SRMs can self-diagnose the quality of repairing and self-sense the damage of repaired zone. The replacement ratios of FSSAs to sand for SRMs were 0% (FSSA00), 25% (FSSA25), and 50% (FSSA50) by sand weight. The electrical resistivity of SRMs generally decreased as the compressive stress of SRMs increased: the electrical resistivity of FSSA25 at the age of 7 hours decreased from 78.16 to 63.68 kΩ-cm as the compressive stress increased from 0 to 22.37 MPa. As the replacement ratio of FSSAs by weight of sand increased from 0% to 25%, the stress sensitivity coefficient (SSC) of SRM at the age of 7 h increased from 0.471 to 0.828 %/MPa owing to the increased number of partially conductive paths in the SRMs. However, as the replacement ratio of FSSAs further increased up to 50%, the SSC decreased from 0.828 to 0.649 %/MPa because some of the partially conductive paths changed to continued conductive ones. SRMs are expected to self-sense the quality and future damage of repaired zone only by measuring the electrical resistivity of the repaired zone in addition to fast recovery in the mechanical resistance of structures.
휨하중을 받는 스마트 초고강도 섬유보강 콘크리트의 전기역학적 거동 조사
김태욱,김민경,김동주,Kim, Tae-Uk,Kim, Min-Kyoung,Kim, Dong-Joo 한국구조물진단유지관리공학회 2022 한국구조물진단유지관리공학회 논문집 Vol.26 No.5
This study investigated the electromechanical response of smart ultra-high performance fiber reinforced concretes (S-UHPFRCs) under flexural loading to evaluate the self-sensing capacity of S-UHPFRCs in both tension and compression region. The electrical resistivity of S-UHPFRCs under flexural continuously changed even after first cracking due to the deflection-hardening behavior of S-UHPFRCs with the appearance of multiple microcracks. As the equivalent bending stress increased, the electrical resistivity of S-UHPFRCs decreased from 976.57 to 514.05 kΩ(47.0%) as the equivalent bending stress increased in compression region, and that did from 979.61 to 682.28 kΩ(30.4%) in tension region. The stress sensitivity coefficient of S-UHPFRCs in compression and tension region was 1.709 and 1.098 %/MPa, respectively. And, the deflection sensitivity coefficient of S-UHPFRCs in compression region(30.06 %/mm) was higher than that in tension region(19.72 %/mm). The initial deflection sensing capacity of S-UHPFRCs was almost 50% of each deflection sensitivity coefficient, and it was confirmed that it has an excellent sensing capacity for the initial deflection. Although both stress- and deflection-sensing capacity of S-UHPFRCs under flexural were higher in compression region than in tension region, S-UHPFRCs are sufficient as a self-sensing material to be applied to the construction field.
김태욱,Kim, Tae-Uk 대한양돈협회 2006 養豚 Vol.28 No.12
본고는 본회 인터넷 홈페이지(www.koreapork.or.kr)'양돈법류상담코너'에 게시된 질문과 답변을 정리한 것입니다.ㆍㆍㆍ편집자주
김태욱,전의진,이우일,Kim, Tae-Uk,Jeon, Ui-Jin,Lee, U-Il 한국기계연구원 1988 기계연구원소보 Vol.18 No.-
Impregnation of molten thermoplastic resin into continuous unidirectional fiber bundles was investigated. The degree of impregnation is defined as the ratio between the number of impregnated fibers and the total number of fibers of a bundle. The degree of impregnation was modeled as a function of time, impregnation pressure, temperature and tow size assuming the radial inward flow through the fiber bundle is governed by the Darcy's law. The permeability was assumed to be constant. Experiments were performed to evaluate the validity of the medel. Today's T300 graphite fiber bundles and Polyetheretherketone(PEEK) resin was used. A fiber bundle and resin powder were put into a mold and pressure and temperature were applied. After a predetermined time, the sample was taken out and microphotographs of the cross-section were taken. From the microphotographs, the number of impregnated fibers was counted and then the degree of impregnation was determined. Experiments were also performed for different tow sizes. Good agreements were found between the model and the experiments rendering a confidence in the model.