• Corrosion Science and Technology
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• 제3권3호
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• pp.118-126
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• 2004

The correlation between sensor output and corrosion rate of reinforcing steel was evaluated by laboratory electrochemical tests in saturated $Ca(OH)_2$ with 3.5 wt.% NaCl and confirmed in concrete environment. In this paper, two types of electrochemical probes were developed: galvanic cells containing of steel/copper and steel/stainless steel couples. Potentiodynamic test, weight loss measurement, monitoring of open-circuit potential, linear polarization resistance (LPR) measurement and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of steel bar embedded in concrete. Also, galvanic current measurements were conducted to obtain the charge of sensor embedded in concrete. In this study, steel/copper and steel/stainless steel sensors showed a good correlation in simulated concrete solution between sensor output and corrosion rate of steel bar. However, there was no linear relationship between steel/stainless steel sensor output and corrosion rate of steel bar in concrete environment due to the low galvanic current output. Thus, steel/copper sensor is a reliable corrosion monitoring sensor system which can detect corrosion rate of reinforcing steel in concrete structures.

• 센서학회지
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• 제11권3호
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• pp.138-144
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• 2002

스테인레스 봉입형 압력센서를 제작하기 위하여 먼저 반도체 제조 및 식각 공정을 통하여 반도체 압력센서를 제작하였다 그리고 이를 glass molding된 스테인레스 housing에 올려놓고 $50\;{\mu}m$ 두께의 스테인레스 박판을 용접한 후 실리콘 오일을 채워 넣고 봉입하여 압력 범위 10 bar 센서를 완성하였다. 이와 같이 제작한 센서와 XTR105 발신기 전용 회로를 결합하여 $4{\sim}20\;mA$ 출력의 압력 발신기를 제작하고 그 특성을 조사하였다. 온도 보상 전 정확도는 ${\pm}5%$ FS이었으나 보상 후 정확도 ${\pm}1%$ FS로 개선되었다.

• 전기학회논문지P
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• 제62권4호
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• pp.181-185
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• 2013

This paper deals with the electromagnetic loss characteristics of enclosures for a 24kV high voltage switchgear by using a finite element method (FEM). A study on the electromagnetic characteristics of enclosures for a high voltage switchgear should be conducted to minimize the size and the temperature rising of a switchgear. Generally, the enclosures made by stainless steel are used to minimize the eddy current loss caused by the transporting current in Bus bars due to its non-magnetic characteristics although the price of stainless steel is expensive compared with other metal for enclosures. Therefore, a switchgear made by stainless steel enclosures could be fabricated as a small size and are applied to a switchgear in urban substations. On the contrary, the switchgear enclosures made by steel could be fabricated with relatively cheap manufacturing price. However, the temperature easily rises due to the transporting current in Bus bars because steel is a ferromagnetic material. Therefore, the size of a switchgear made by steel enclosures is relatively massive and installed in rural substations. In this paper, the electromagnetic losses in the enclosures of a switchgear according to various enclosure thicknesses are calculated and compared with each other. Especially, we proposed a hybrid type enclosures for a switchgear made by stainless steel (top and bottom enclosure) and steel (left and right enclosure). It is concluded that the cost electromagnetic performance of applying the hybrid type enclosure is favorable to develop a high voltage switchgear.

• 한국구조물진단유지관리공학회 논문집
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• 제19권3호
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• pp.113-121
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• 2015

조적조 건축물은 국내 소규모 주택의 많은 부분을 차지하지만 취성적 거동 및 낮은 연성능력으로 현재에는 사용빈도가 많이 낮아졌다. 그럼에도 불구하고 조적조 건축물의 낮은 건축비, 재료의 친환경성은 국외를 중심으로 새롭게 각광 받으면서 구조적 단점을 해결하고자 많은 연구가 진행 중이다. 본 연구에서는 조적벽체 및 교차부 실험체를 제작하여 신축줄눈 유 무에 따른 구조적 거동의 차이를 확인하고, 연결철물 (스틸플레이트, 스테인리스 트위스트바) 삽입에 따른 보강효과를 검증하였다. 실험결과를 통해 스틸플레이트를 삽입한 실험체는 내력이 증가되어 실험체의 강성이 향상되었으며, 스테인리스 트위스트바를 삽입한 실험체는 연성능력이 향상되어 취성파괴가 발생하지 않아, 연결철물 삽입에 따른 보강효과는 우수한 것으로 나타났다.

• 대한기계학회논문집A
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• 제36권7호
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• pp.769-776
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• 2012

본 논문의 유한요소 손상해석기법은 재료 인장물성과 파괴기준을 필요로 한다. 기존에 연구된 재료들은 노치인장 시험결과로부터 하나의 인장물성과 파괴기준을 구할 수 있었다. 그러나 본 논문에서 사용된 cast stainless steel(CF8M)의 경우, 동일한 조건의 노치인장 시험결과들에 분산이 존재하여 해석자에 따라 다른 인장물성과 파괴기준이 구해질 수 있다. 따라서 해석자에 관계없이 일관된 인장물성 및 파괴기준을 구할 수 있는 적절한 절차가 필요하다. 본 논문에서는 노치반경 16mm 의 인장시편 시험결과로부터 평균 인장물성을 구하였고, 이를 유한요소 해석에 적용하여 3 개의 파괴기준을 구하였다. 구해진 인장물성과 파괴기준을 적용하여 J-R 파괴인성 시험에 대한 손상해석을 수행하였고, 시험결과와 비교함을 통해 제시된 절차의 타당성을 검증하였다.

• 한국세라믹학회지
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• 제51권5호
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• pp.516-521
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• 2014

This paper describes the development of a new piezoelectric unimorph cantilever structure intended to improve electrical output power, compared to a conventional cantilever. The proposed structure employs a cylindrical bar attached to one side of a steel plate, which is a significant factor in forced vibration mode. The feasibility of the proposed methodology was assessed experimentally and theoretically. The influence of three different types of bar material (i.e., stainless steel, silicon rubber, and urethane), and bar position, on the output voltage were examined and compared with those without the bar. The optimal position and material for the bar were identified through experimental and theoretical analyses. It appears that the electrical output power of the proposed cantilever is about 40% higher than that of a conventional unimorph cantilever.

• 한국기계가공학회지
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• 제7권4호
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• pp.56-61
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• 2008

Cropping metal materials is widely used for feeding processes of various forming method, such as forging, extrusion, drawing, and upsetting. However, cropping has many weak points, which are material loss in part of cutting, chip creation, and much use of lubrication oil, etc. In this study, instead of cropping, a novel process is proposed to cut metal materials, especially stainless steel bar which is known very difficult to crop. Results of FE-analysis will be shown to verify the proposed method comparing with those of the conventional cropping process. Also, fitting products were successfully forged using the fabricated billet by the proposed process.

• 한국생산제조학회지
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• 제20권2호
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• pp.129-132
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• 2011

This paper presents small hydrogen regulator for the mobile fuel cell. Mobile fuel cell is generally classified into open-end type and dead-end type. In the open-end type, flow rate of hydrogen is constantly controlled, while pressure of hydrogen is constantly maintained in the dead-end type. Considering the efficiency and stability of the fuel usage, dead-end type is more suitable with mobile fuel cell. Mobile fuel cell operated by dead-end mode requires hydrogen regulator which controls the hydrogen pressure from 0.1bar to 0.5bar within 3% error. In this paper, small hydrogen regulator (volume of 2.6cc) was fabricated by stainless steel. Regulation characteristics was experimentally evaluated.

• 대한기계학회논문집A
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• 제22권3호
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• pp.595-602
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• 1998

Specimens of 304 stainless steel were tested to failure at elevated temperatures under multiaxial stress states, uniaxial tension using smooth bar specimens, biaxial shearing using double shear bar specimens, and triaxial tension using notched bar specimens. Rupture times are compared for uniaxial, biaxial, and triaxial stress states with respect to the maximum principal stress, the von Mises effective stress, and the principal facet stress. The results indicate that the principal facet stress gives the best correlation for the material investigated, and this parameter can predict creep life data under multiaxial stress states with rupture data obtained with specimens under uniaxial stresses. The results also suggest that grain boundary cavitation, coupled with localized deformation processes such as grain boudary sliding, controls the lifetimes of the specimens.

• Steel and Composite Structures
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• 제49권1호
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• pp.1-17
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• 2023

Based on Ahmadzadeh-Varvani hardening rule (A-V model), multiaxial ratcheting effect of Z2CND18.12N austenitic stainless steel is simulated by ABAQUS with user subroutine UMAT. The results show that the predicted results of the origin multiaxial A-V model are lower than the experimental data, and it is difficult to control ratcheting strain rate. In order to improve the predicted capability of A-V model, the A-V model is modified. In this study. Moreover, under the assumption of the von Mises yield criterion and normal plasticity flow rule, we develop a numerical algorithm of plastic strain with the improved model to implement the finite element calculation of the model. Internal iteration in the numerical algorithm was implemented with the Euler backward method, which calculated the trial strain for each equilibrium iteration using the consistent tangent matrix. With a user subroutine, the proposed model is programmed into ABAQUS for a user - executable version. By simulating the uniaxial ratcheting of a round bar made of Z2CND18.12N austenitic stainless steel, we observe that the predicted results simulated by ABAQUS with UMAT are compared with the experimental data. The predicted results of the improved multiaxial A-V model are consistent well with the experimental data.