• Structural Engineering and Mechanics
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• 제75권1호
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• pp.101-108
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• 2020

The present study intends to analyze damage in thin-walled steel cylinders undergoing constant internal pressure and thermal cycles through use of anisotropic continuum damage mechanics (CDM) model coupled with nonlinear kinematic hardening rule of Chaboche. Materials damage in each direction was defined based on plastic strain and its direction. Stress and strain distribution over wall-thickness was described based on the CDM model and the return mapping algorithm was employed based on the consistency condition. Plastic zone expansion across the wall thickness of cylinders was noticeably affected with change in internal pressure and temperature gradients. Expansion of plastic zone over wall-thickness at inner and outer surfaces and their boundaries demarking elastic and plastic regions was attributed to the magnitude of damage induced over thermomechanical cycles on the thin-walled samples tested at various pressure stresses.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.357-362
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• 2001

The pipe fracture tests were performed on 102mm-Sch.80 carbon steel pipe with various local wall thinning shapes, in order to understand failure behavior of thinned pipe. Pipe specimens were subjected to monotonic bending moment, using 4-points loading system, under internally pressurized condition. From the results of experiment, the failure mode, load carrying capacity, and deformability of local wall thinning pipe were investigated. Failure mode of thinned pipe depended on magnitude of internal pressure and thinning length as well as loading direction and thinning depth and angle. The variation in load carrying capacity and deformability of thinned pipe with length of thinned area was determined by stress type appled to thinning region and circumferential thinning angle. Also, the effect of internal pressure on failure behavior was dependent on failure mode of thinned pipe, and it promoted crack occurrence and mitigated local buckling at thinned area.

• 환경위생공학
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• 제12권3호
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• pp.95-102
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• 1997

The process which can stabilize water quality of treatment and improve nitrogen removal rate under the condition of high organic loading was developed by charging fibrous HBC media to single sludge nitrification-denitrification process. This process was operated easier, minimized the treatment cost, and shortened the retention time. To improve T-N removal rate, a part of nitrifing liquid at aerobic zone was recycled to anoxic zone by approximate internal recycle ratio. The experimental results are as follows ; T-N removal efficiency in the organic volumetric loading 0.14-0.19 kg/COD/m$^{3}$·d was obtained asmaxium of 85% at internal recycle ratio 2.5 and in more ratio than this it was decreased. Organic removal efficiency was about 91% under the overall experimental conditions and not influenced by recycle ratio.

• 대한기계학회논문집A
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• 제28권4호
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• pp.402-409
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• 2004

The purpose of this study is to investigate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear three-dimensional finite element analyses were performed to obtain the collapse moment of elbow containing various wall thinning defects located at intrados and extrados under two loading modes (closing and opening modes) with internal pressure. From the results of analysis, the effect of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependence of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

• 소성∙가공
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• 제31권3호
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• pp.143-150
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• 2022

The purpose of this study was to investigate an innovative hydroforming process for the cost-effective manufacturing of double layered tube with circumferentially corrugated patterns. Conventional double pipe heat exchanger has relatively poor heat transfer efficiency because of the limited contact area resulting from the concentrically arranged simple cylindrical structure. As a promising alternative to enhance heat transfer efficiency, double layered tube with corrugated internal pattern was considered in this study. To fabricate corrugated inner tube, innovative tube hydroforming system was developed. The customized loading paths were established using the simulated forming pressure and contracting stroke at various bar diameters. Experimentally obtained cross-sectional profiles were analyzed to evaluate the reliability and applicability of the hydroformed tube with various patterns. The results demonstrate that the proposed hydroforming process can be a feasible alternative for manufacturing high-performance double-tube heat exchangers.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.268-273
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• 2004

This study is conducted to clarify the effect of internal pressure on the deformation and collapse behaviors of wall thinned elbow under in-plane bending moment. Thus the nonlinear three-dmensional finite element analyses were performed to obtain the moment-rotation curve of elbow contatining various wall thinning defects located at intrados and extrados under in-plane bending (closing and opening modes) with internal pressure of $0{\sim}15MPa.$ From the results of analysis, the effect of internal of collapse moment of elbow on the global deformation behavior of wall thinned elbow was discussed, and the dependence of collapse moment of elbow on the magnitude of internal pressure was investigated under different loading mode, defect location, and defect shape.

• 한국안전학회지
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• 제9권3호
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• pp.3-12
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• 1994

This study employed the Eshelby's equivalent inclusion method incorporated with mean field theory to investigate the Internal stress of short fiber-reinforced metal matrix composites during static loading and the dynamic finite element analysis by using alternative unit cell model to investigate the impact behaviors during the impact loading. Using the 2124 Al-SiC system as an example, the general effects of parameters such as fiber's aspect ratio, content and modulus were examined.

• Structural Engineering and Mechanics
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• 제8권4호
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• pp.421-438
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• 1999

In this paper a practical limit load estimating procedure is proposed for general pipe-elbow structures subjected to complex loading (in-plane and out-of-plane bending, internal pressure and axial force). The explicit calculating formulae are presented on the basis of theoretical analysis combined with numerical simulation. Von Mises' yield criterion is adopted in both analytical and numerical calculation. The finite element examination shows that the method provides a simple but satisfactory prediction of pipe structures in engineering plastic analysis.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.295-297
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• 2003

Cryogenic systems is requirement for the operation of HTS power cables. In general, HTS power cables require temperature below 77K, a temperature that can be achieved from the liquid nitrogen or sub-cooled LN2. HTS power cable is needed for sufficient refrigeration to overcome its low temperature heat loading. This loading typically comes in two forms : (1) heat leaks from the surroundings and (2) internal heat generation. This paper is a explanation for the cooling test of 10m HTS power cable.

• 한국전산구조공학회논문집
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• 제24권3호
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• pp.267-274
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• 2011

본 연구에서는 K형 관이음부의 내부에 단일 및 이중 환보강재를 설치할 경우에 발생하는 보강효과를 수치적으로 평가하였다. 지부재에 축하중을 받는 비보강 이음부와 환보강 이음부의 국부적 최대응력을 평가하기 위해 유한요소해석을 수행하였다. 작용하중과 내부 환보강재의 기하학적 형상이 이음부 거동에 미치는 영향을 평가하고 보강효과를 산정하였다. 또한 단일 환보강재와 이중 환보강재를 비교 평가하여 배치에 따른 응력분포 변화 및 응력의 분산효과를 산정하였다. 수치해석 결과로부터 이음부의 보강설계 자료에 활용 가능한 환보강재의 경제적 규격을 제시하였다.