• 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.

• Wind and Structures
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• 제23권1호
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• pp.75-90
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• 2016

A probabilistic approach that combines structural demand hazard analysis with cumulative damage assessment is presented and applied to a steel tower of a wind turbine. The study presents the step by step procedure to compare the reliability over time of the structure subjected to fatigue, assuming: a) a binomial Weibull annual wind speed, and b) a traditional Weibull probability distribution function (PDF). The probabilistic analysis involves the calculation of force time simulated histories, fatigue analysis at the steel tower base, wind hazard curves and structural fragility curves. Differences in the structural reliability over time depending on the wind speed PDF assumed are found, and recommendations about selecting a real PDF are given.

• Structural Engineering and Mechanics
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• 제88권3호
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• pp.287-299
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• 2023

This article describes experimental and numerical analyses of eccentrically loaded over the axially loaded circular concrete filled double-skinned steel tubular (CFDST) short columns. Tests on circular CFDST short columns under eccentric and concentric loading were conducted to assess their responses to the frequent intensity of 5-30 mm at the interval of each 5 mm eccentric loading conditions with constant cross-sectional proportions and width-to-thickness ratios of the outside and internal tubes. The non-linear finite-element analysis of circular CFDST short columns of eccentrically loaded over the axially loaded was performed using the ABAQUS to predict the structural behavior and compare the concentric loading capacity over the various eccentric loading conditions. The comparison outcomes show that the axial compressive strength of the circular CDFST short columns was 2.38-32.86%, lesser than the concentrically loaded short column with the inner circular section. Also, the influence of computer simulation employed is more efficient in forecasting the experimentally examined performance of circular CFDST stub columns.

• 한국식품과학회지
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• 제47권6호
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• pp.744-750
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• 2015

Purple sweet potatoes were dehydrated with maltodextrin with different dextrose equivalent (DE) values of 4-7, 13-17, 16.5-19.5, and 17-20. Maltodextrin was used as a molecular press dehydrating agent. The molecular dehydration rate of the purple sweet potatoes increased over time. As the DE of maltodextrin increased, the moisture content after 12 h of dehydration decreased from 65.7% to 40.8, 36.1, 34.9, and 28.6% for DE values of 4-7, 13-17, 16.5-17.5, and 17-20, respectively. Additionally, total phenolic content, anthocyanin, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities decreased as the DE value of maltodextrin increased. While maltodextrins with DE values of 16.5-19.5 and 17-20 effectively dehydrated the purple sweet potatoes, total phenolic, anthocyanin, and DPPH radical scavenging activities were lowered during dehydration. The DPPH radical scavenging activities correlated to both the total phenolic content ($r^2=0.96$) and anthocyanin contents ($r^2=0.95$) of the purple sweet potatoes. These results indicate that the purple sweet potatoes were effectively dehydrated with maltodextrin whose DE values ranged 16.5-20, although there were losses in the total phenolic and anthocyanin contents.

• 한국안전학회지
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• 제26권4호
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• pp.1-6
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• 2011

New methods for joining sheet of metal are being sought. One of the most promising methods is MPJ (mechanical press joining). It has been used in thin metal work because of its simple process and relative advantages over other methods, as it requires no fasteners such as bolts or rivets, consumes less energy than welding, and produces less ecological problems than adhesive methods. In this study, the joining process and static behavior of single overlap joints has been investigated. During fixed die type joining process for SPCC plates, the optimal applied punching force was found. The maximum tensile-shear strength of the specimen produced at the optimal punching force was 1.75 kN. The FEM analysis result on the tensile-shear specimen showed the maximum von-Mises stress of 373 MPa under the applied load of 1.7 kN, which is very close to the maximum tensile strength of the SPCC sheet(= 382 MPa). This suggests that the FEM analysis is capable of predicting the maximum tensile load of the joint.

• 한국언론정보학보
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• 제41권
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• pp.108-144
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• 2008

본 연구는 언론의 기능을 언급할 때 가장 핵심적인 권력과 사회에 대한 감시 비판자로서의 파수견(Watchdog) 개념이 어떻게 생성되었고 발전되었는가를 분석하였다. 일반적으로 파수견 개념은 자유주의적 언론이론에서 파생된 것으로 인식되어 왔다. 그러나 이러한 인식과는 달리 파수견 개념은 언론의 필요성에 의해 주장되고 법원에 의해서 수용되어진 일종의 면책특권으로 언론의 공익적 활동에 당위성을 부여하는 것이라는 시각이 제기되었다. 미국의 경우 파수견 개념은 19세기 말 명예훼손법의 발전과 함께 형성되었고 법원에서 그 개념을 수용하면서 현재의 파수견의 이미지, 즉 권력에 대한 감시 비판자의 모습을 갖추게 되었다. 이러한 시각에 근거하여 한국에서의 파수견 개념의 형성과 발전과정을 관련 판례를 통해서 추적하였다. 우리나라의 경우 판결례를 분석한 결과 우리 법원은 비록 그 개념의 수용에는 대단히 늦었지만, 파수견 개념을 언론의 공익적 기능의 측면에서 받아들이고 있는 것으로 파악되었다. 이러한 사법부외 판단은 미국의 경우와 달리 언론의 끈질긴 주장에 의한 것이라기보다는 법원의 언론 활동의 복잡성과 오류 발생의 불가피성을 인정하면서 기능했다고 하겠다. 이러한 법원의 인식은 언론의 감시 및 비판의 기능을 정치인이나 국가기관뿐만 아니라 공적인 역할을 하는 사인에게까지 확대해서 적용하고 있는데 이는 파수견 개념을 상당히 광범위하게 인정하는 것이라고 할 수 있다. 그러나 우리 사법부는 보도의 내용이 상당하고 악의가 없어야 한다는 데 일치하고 있는데 이는 미국의 경우처럼 파수견 개념을 하나의 면책특권으로서는 아직 인정하고 있지 않음을 의미하는 것이라고 하겠다.

• Wind and Structures
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• 제36권2호
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• pp.75-90
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• 2023

Turbulent wind flow over hilly terrains has been extensively investigated in the scientific literature and main findings have been included in technical standards. In particular, turbulent wind flow over nominally two-dimensional hills is often adopted as a benchmark to investigate wind turbine siting, estimate wind loading, and dispersion of particles transported by the wind, such as atmospheric pollutants, wind-driven rain, windblown snow. Windblown sand transport affects human-built structures and natural ecosystems in sandy desert and coastal regions, such as transport infrastructures and coastal sand dunes. Windblown sand transport taking place around any kind of obstacle is rarely in equilibrium conditions. As a result, the modelling of windblown sand transport over complex orographies is fundamental, even if seldomly investigated. In this study, the authors present a wind-sand tunnel test campaign carried out on a nominally two-dimensional sinusoidal hill. A first test is carried out on a flat sand fetch without any obstacle to assess sand transport in open field conditions. Then, a second test is carried out on the hill model to assess the sand flux overcoming the hill and the morphodynamic evolution of the sand sedimenting over its upwind slope. Finally, obtained results are condensed into a dimensionless parameter describing its sedimentation capability and compared with values resulting from other nominally two-dimensional obstacles from the literature.

• Geomechanics and Engineering
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• 제15권3호
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• pp.919-925
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• 2018

Stress-strain responses of weak-to-strong carbonate rocks used for tunnel construction were studied. The analysis of applicability of exponential stress-strain models based on Haldane's distribution function is presented. It is revealed that these exponential equations presented in transformed forms allow us to predict stress-strain relationships over the whole pre-failure strain range without mechanical testing of rock samples under compression using a press machine and to avoid measurements of axial failure strains for which relatively large values of compressive stress are required. In this study, only one point measurement (small strain at small stress) using indentation test and uniaxial compressive strength determined by a standard Schmidt hammer are considered as input parameters to predict stress-strain response from zero strain/zero stress up to failure. Observations show good predictive capabilities of transformed stress-stress models for weak-to-strong (${\sigma}_c$ <100 MPa) heterogeneous carbonate rocks exhibiting small (< 0.5 %), intermediate (< 1 %) and large (> 1 %) axial strains.

• 소성∙가공
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• 제19권4호
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• pp.203-209
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• 2010

In the hot press forming process (HPF), a martensitic structure is obtained by controlling the cooling rate when cooling a boron sheet that is heated up to over $900^{\circ}C$. The HPF process has various advantages such as the improvement in formability and material properties and minimal spring back of the deformed materials. The factors related to the cooling rate depend on the heat transfer characteristics between heated materials and dies. Therefore, in this study, the cooling rate is controlled by adjusting the heat transfer coefficient of the material at the pressing process. And, the mechanical properties and microstructure of the deformed material is demonstrated during the HPF process where cold dies are used to form the heated steel plate. This is achieved by varying the major forming conditions that control the cooling rate regarded as the most important process parameter.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.94-96
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• 2014

Press machine has advantage over other manufacturing machine which can produce large quantities of products in short time so it is widely used in lots of industrial sectors. However, vibration problems may occur when operating a high pressure. It has been subjected to the condition monitoring vibration sensors attached to the main point. We perform the maintenance before a failure occurs, the system receives a high load. In this paper, in order to determine the structural characteristics for the transport system to conduct the vibaration and shock analysis.