• Advances in Computational Design
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• 제3권2호
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• pp.113-132
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• 2018

This paper presents the vibration and harmonic analysis of orthotropic laminated composite plate. The response of plate is determined using Finite Element Method. The eight noded shell 281 elements are used to analyze the orthotropic plates and results are obtained so that the right choice can be made in applications such as aircrafts, rockets, missiles, etc. to reduce the vibration amplitudes. Initially the model response for orthotropic plate and harmonic response for isotropic plate is verified with the available literature. The results are in good agreement with the available literature. Numerical results for the natural frequency and harmonic response amplitude are presented. Effects of boundary conditions, thickness to width ratio and number of layers on natural frequency and harmonic response of the orthographic plates are also investigated. The natural frequency, mode shape and harmonic analysis of laminated composite plate has been determined using finite element package ANSYS.

• Steel and Composite Structures
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• 제12권4호
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• pp.275-289
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• 2012

In this paper the influence of stiffener location, rise/span ratio and fibre orientation on vibration behavior of corner supported hypar shells is studied by using a four-node hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. Benchmark problems are solved to validate the approach and free vibration response of stiffened orthotropic hypar shells is studied both with respect to fundamental frequency and mode shapes by varying the location of stiffeners, rise/span ratio and fiber orientation.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.501-506
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• 2012

Many innovative design features are employed in the reactor vessel internals of SMART, a small integral-type pressurized water reactor, one of which is the flow skirt, which uniformly distributes flow and horizontally restrains the lower part of the core support barrel. This new design requires a comprehensive investigation of vibration characteristics. Therefore, in this study, modal characteristics of flow skirts are investigated with finite element analysis. Specifically, we investigate how the presence of holes, the presence of three rings attached to the flow skirt, and the thickness of the lowest shell effect vibration characteristics. In addition, the fluid effect is addressed, since the flow skirt is submerged in the fluid.

• Steel and Composite Structures
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• 제6권3호
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• pp.221-236
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• 2006

The objective of this work is to describe the main steps involved in the derivation of a GBT (Generalised Beam Theory) formulation to analyse the vibration behaviour of loaded cold-formed steel members and also to illustrate the application and capabilities of this formulation. In particular, the paper presents and discusses the results of a detailed investigation about the local and global free vibration behaviour of lipped channel simply supported columns. After reporting some relevant earlier GBT-based results dealing with the buckling and vibration behaviours of columns and load-free members, the paper addresses mostly issues concerning the variation of the column fundamental frequency and vibration mode nature/shape with its length and axial compression level. For validation purposes, some GBT-based results are also compared with values obtained by means of 4-node shell finite element analyses performed in the code ABAQUS.

• 디지털콘텐츠학회 논문지
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• 제18권6호
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• pp.1135-1142
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• 2017

본 논문에서는 사각지대의 범죄를 예방하고, 예측하지 못한 화재 또는 위험을 예방하기 위하여 IoT 기반의 스마트 CCTV 방범 서비스를 제안한다. 제안 방식에서는 라즈베리파이를 이용하여 RC(Radio Control)카를 만들고 RC카에 카메라 및 각종 모듈을 장착하였으며 방범 서비스 처리는 Raspbian O/S, Apach Web Server, Shell script, Python, PHP, HTML, CSS, Javascript를 사용하여 구현되었다. RC카는 영상, 음성 그리고 온도 등의 모듈로 현장의 위험을 판단하여 관리자에게 상황을 알려주는 방범 서비스를 제공한다. 실험 결과 영상과 음성 정보의 전달 시간이 0.1초 내에서 처리되었을 뿐 아니라 AVG, 위급 상황, 수동 모드에도 실시간 상태 전송이 가능하였다. 스마트시티 구현에 무인자동차, 드론 등에도 적용하여 제안 방식이 활용할 수 있을 것으로 기대한다.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.521-528
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• 2008

중공사막 접촉기에 적절한 PVDF 중공사막을 상전이 공정에 의하여 제조하였으며, SEM 과 기체투과도에 의하여 그 특성을 분석하였다. 벤치규모 중공사막 접촉기에서 $SO_2$ 제거를 위한 흡수제는 수산화나트륨 수용액을 사용하였다. 기체는 shell side, 액체는 lumen side로 흐르는 counter-current로 실험하였으며, 흡수제의 농도, 기체의 유속, 액가스비, 유입 $SO_2$ 농도에 따른 영향을 알아보았으며, 수학적 모델링에 의해 막 물질전달계수($k_m$)를 측정하였다. 흡수제의 농도와 액기비가 증가함에 따라 기-액 계면에서 충분한 알칼리도가 제공되므로, 액체막 저항이 감소하며, 총괄물질전달 용량계수는 증가하였다. 기체유속이 증가함에 따라 기체막저항은 감소하게 되므로 총괄물질전달 용량계수는 증가하였다.

• 대한토목학회논문집
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• 제32권6A호
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• pp.379-387
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• 2012

본 연구에서는 새로운 에너지 수확용 Multi-layer 블록 구조를 제시하고 고체 및 Shell 유한 요소를 사용하여 다양한 기하학적 형상 변화에 대한 자유진동 특성을 분석하고 압전 성능을 실험적으로 평가한다. 본 연구에서 제시하는 블록 구조에 대한 2차원 및 3차원 유한요소 모델은 해석의 정확성 뿐 만 아니라 전체 진동 모드를 정확히 보여준다는 점에서 장점을 갖는다. ABAQUS가 적용된 유한요소 모델은 다양한 Tip mass 및 PZT 변화에 따른 Multi-layer 블록 구조의 자유진동을 분석하기 위하여 사용되었다. 특히, 본 연구에서 제시한 결과는 블록구조 전체의 기하학적 형상, Tip mass 및 Hole의 유무, Tip mass 및 PZT의 위치변화 등에 대하여 국부 및 전체 진동 모드에 미치는 중요한 영향들에 대하여 초점을 둔다. 또한, 실험실 규모의 실제 모형 실험을 수행하여 개발한 에너지 블록구조의 발전성능을 평가하였다.

• Wind and Structures
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• 제25권2호
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• pp.131-156
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• 2017

This paper deals with the dynamic stability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced micro cylindrical shells. The structure is subjected to harmonic non-uniform temperature distribution and 2D magnetic field. The CNT reinforcement is either uniformly distributed or FG along the thickness direction where the effective properties of nano-composite structure are estimated through Mixture low. The viscoelastic properties of structure are captured based on the Kelvin-Voigt theory. The surrounding viscoelastic medium is considered nonhomogeneous with the spring, orthotropic shear and damper constants. The material properties of cylindrical shell and the viscoelastic medium constants are assumed temperature-dependent. The first order shear deformation theory (FSDT) or Mindlin theory in conjunction with Hamilton's principle is utilized for deriving the motion equations where the size effects are considered based on Eringen's nonlocal theory. Based on differential quadrature (DQ) and Bolotin methods, the dynamic instability region (DIR) of structure is obtained for different boundary conditions. The effects of different parameters such as volume percent and distribution type of CNTs, mode number, viscoelastic medium type, temperature, boundary conditions, magnetic field, nonlocal parameter and structural damping constant are shown on the DIR of system. Numerical results indicate that the FGX distribution of CNTs is better than other considered cases. In addition, considering structural damping of system reduces the resonance frequency.

• 한국구조물진단유지관리공학회 논문집
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• 제9권1호
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• pp.271-281
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• 2005

외부유체를 유한요소화 할 경우 경계조건을 만족시키도록 무한반경까지를 모델링 할 수 없으므로 이를 보정하기 위하여 유한경계에서의 경계조건으로 발산경계조건을 사용하였다. 외부유체의 모델링에서 적용한 수치모델은 쉘 요소 및 유체요소를 축대칭 구조물의 특성을 이용한 링요소로 모델화하여 자오방향 모우드와 주변방향의 파형 모우드를 변수분리함으로써 지진하중 등의 해석에서도 수십 개의 링요소에 의해 정해에 근사한 값을 얻을 수 있도록 하였다. 축대칭 쉘 구조물과 유체-구조물의 상호관계는 접촉면에서 구조물의 가속도와 유체의 압력관계를 이용한 부가질량을 유체를 비점성, 비압축 및 비회전으로 가정하여 유한요소법에 의해 구하였다. 이에 따라 구조물의 변형에 따른 외부유체 효과를 고려한 부가질량매트릭스를 얻을 수 있었으며, 이에 대한 수치해석을 통하여 고유진동해석 및 지진하중을 주하중으로 한 동적해석을 실시하였다.

• Tribology and Lubricants
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• 제32권3호
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• pp.82-87
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• 2016

We performed an experimental research on lubricant oil in dual fuel medium-speed engines. It is important to select the appropriate lubricant oil because it could significantly affect engine lifetime and performance. We generally recommend the selection of the lubricant oil according to the fuel grades as contents in the project guide. However, it is a considerable challenge for shipyards to implement this concept because of the lack of space to install the complicated lubricating oil system for dual fuel engines. Therefore, we determine the adaptability of one-common lubricant oil for HiMSEN dual fuel engine through this experimental research. To check abnormality in gas mode operation and durability of engine components when a lubricating oil with high BN (base number) is used, overhaul inspections and lubricant oil analysis are carried out two times, and four times, respectively, during an operation of approximately 300 h. We investigated the variations in kinematic viscosity, base number, element quantity, pentane insoluble and sulfated ash in lubricant oil analysis. Moreover, we also investigated whether the deposit formation or wear occurred in various bearings, injectors, exhaust valves, intake valves, piston rings and so on through the overhaul inspections. There are no problems in the lubricant analysis and the overhaul inspections. Through the experimental research, we confirm that one-common lubricant oil should be selected according to the higher sulfur content of fuel oil in dual fuel engines.