• 한국소음진동공학회논문집
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• 제25권5호
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• pp.329-336
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• 2015

This paper presents a sorting method of mode vectors and natural frequencies about a rotor-journal bearing system. The rotor is solved by the finite element method, the bearing stiffness and damping coefficient are solved by the finite difference method. At any rotation speed section through the eigenvalue analysis of the system, mode vectors and natural frequencies not sorted are confirmed via the Campbell diagram and the MAC(modal assurance criterion). To sort mode vectors and natural frequencies of the section, a mode sorting method is presented through a method of rearranging the MAC of the mode vectors. Finally, the mode vectors and the natural frequencies are sorted by using the presented method, these are verified through the MAC.

• 한국정밀공학회지
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• 제28권3호
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• pp.265-274
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• 2011

This paper presents current state of the prediction simulator of structural characteristics of machinery equipment accuracy. Developed accuracy prediction simulator proceeds and estimates the structural analysis between the designer and simulator through the internet for convenience of designer. 3D CAD model which is input to the accuracy prediction simulator would simplified by the process of removing the small hole, fillet and chamfer. And the structural surface joints would be presented as the spring elements and damping elements for the structural analysis. The structural analysis of machinery equipment joints, containing rotary motion unit, linear motion unit, mounting device and bolted joint, are presented using Finite Element Method and their experiment. Finally, a general method is presented to tune the static stiffness at a rotation joint considering the whole machinery equipment system by interactive use of Finite Element Method and static load experiment.

• Steel and Composite Structures
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• 제26권3호
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• pp.315-328
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• 2018

Built-up Double-I (BD-I) columns consist of two hot rolled IPE sections and two cover plates which are welded by fillet welds. In Iran, this type of column is commonly used in braced frames with simple connections and sometimes in low-rise Moment Resisting Frames (MRF) with Welded Flange Plate (WFP) beam-column detailing. To evaluate the seismic performance of WFP connection of I-beam to BD-I column, traditional and modified exterior MRF connections were tested subjected to cyclic prescribed loading of AISC. Test results indicate that the traditional connection does not achieve the intended behavior while the modified connection can moderately meet the requirements of MRF connection. The numerical models of the connections were developed in ABAQUS finite element software and validated with the test results. For this purpose, moment-rotation curves and failure modes of the tested connections were compared with the simulation results. Moreover to avoid improper failure modes, some improvements of the connections were evaluated through a numerical study.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.247-269
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• 2020

A finite strip formulation was developed for buckling and free vibration analysis of laminated composite plates based on different shear deformation plate theories. The different shear deformation theories such as Zigzag higher order, Refined Plate Theory (RPT) and other higher order plate theories by variation of transverse shear strains through plate thickness in the parabolic form, sine and exponential were adopted here. The two loaded opposite edges of the plate were assumed to be simply supported and remaining edges were assumed to have arbitrary boundary conditions. The polynomial shape functions are applied to assess the in-plane and out-of-plane deflection and rotation of the normal cross-section of plates in the transverse direction. The finite strip procedure based on the virtual work principle was applied to derive the stiffness, geometric and mass matrices. Numerical results were obtained based on various shear deformation plate theories to verify the proposed formulation. The effects of length to thickness ratios, modulus ratios, boundary conditions, the number of layers and fiber orientation of cross-ply and angle-ply laminates were determined. The additional results on the same effects in the interaction of biaxial in-plane loadings on the critical buckling load were determined as well.

• 한국기계가공학회지
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• 제17권1호
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• pp.122-129
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• 2018

This study conducted a seismic qualification analysis of small savonius style vertical axis wind turbine(VAWT) using finite element method(FEM). The modal analysis was performed on the wind turbine structure to check the occurrence of resonance caused by the rotation of gearbox and windmill blades. Next, it conducted a seismic response spectrum analysis due to horizontal and vertical seismic load of required response spectrum of safe shutdown earthquake with 5 % damping(RRS/SSE 5%) of KS C IEC 61400 and conducted a static analysis due to deadweight and wind load. The total maximum stress of the VAWT structure was calculated by adding the maximum stresses due to each load case using the square root of the sum of the squares(SRSS) method. Finally, the structural safety of the VAWT structure was verified by comparing the total maximum stress and the allowable stress.

• 대한치과교정학회지
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• 제15권1호
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• pp.7-22
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• 1985

The purpose of this study was to analyze the stress distribution and the displacement in the maxillary complex after the application of the reverse headgear. The direction of force was parallel to the occlusal plane. Orthopedic force,300gm, was applied to the maxilla of the dry human skull in a forward direction. The stress distribution and the displacement within the maxillary Complex was analyzed by a 3-dimensional finite element method. The results were as follows: 1. The stress distribution at the molar region was greater than that at the anterior. 2. The stress distribution at the lateral side of the premaxilla was greater than that at the middle aide, especially high stress was noted at the canine eminence. 9. Compressive stress was noted only at the frontozygomatic suture of the zygomatic arch. 4. A forward, upward, and sideward displacement was noted at the entire nodal points of the zygomaticomaxillary suture portion. A displacement with a slight rotation was observed on the transverse palatine suture. 5. The maximum stress was observed at the lateral side of the maxillary tuberosity area, and generally the forward and downward displacement was noted at all this area.

• 전산구조공학
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• 제7권4호
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• pp.69-83
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• 1994

평면 뼈대구조물의 매우 큰 변형에 대하여 정확한 비선형 유한요소의 정식화 과정을 나타내었다. 유한요소의 구성은 변화되는 재료의 기준 물성치에 근거를 두고 형성하였으며 매우 큰 변형을 받는 재료의 성질을 명확하게 특정지어 진응력-변형율 관계식을 직접 적용할 수 있도록 하였다. 큰회전과 작은 변형율을 받는 문제들을 형성하기 위하여 Co-rotation 접근 방법을 사용하였다. 큰 변형을 일으키는 요소의 문제를 해결하기 위하여 직선보 형태의 유한요소를 사용하였으며 개개의 유한요소의 정식화는 축방향력의 영향을 고려하여 미소 처짐보이론을 바탕으로 형성하였다. 본 연구에서 형성된 큰 변형에 대한 비선형 유한요소의 타당성을 확인하기 위해 몇몇 수치해들을 해석하고 검토하였다.

• Steel and Composite Structures
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• 제3권1호
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• pp.47-64
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• 2003

In a nonlinear finite element study on the mechanical behavior of simple beam connections to continuous concrete-filled steel tube columns, two principally different connection types were analyzed: one with plates attached to the outside of the tube wall, relying on shear transfer, and one with an extended plate inserted through the steel section to ensure bearing on the concrete core. The load was applied partly at the connection within the column length and partly at the top, representing the load from upper stories of a multistory building. The primary focus was on the increased demand for load transfer to ensure composite action when concrete with higher compressive strength is used. The results obtained from the analyses showed that the design bond strength derived from push tests is very conservative, mainly due to the high frictional shear resistance offered by pinching and contraction effects caused by connection rotation. However, with higher concrete strength the demand for load transfer increases, and is hard to fulfill for higher loads when connections are attached only to the steel section. Instead, the connection should penetrate into the concrete core to distribute load to the concrete by direct bearing.

• Smart Structures and Systems
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• 제21권3호
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• pp.349-358
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• 2018

This paper investigates the free vibration analysis of double-beam system coupled by a two-degree-of-freedom mass-spring system. In order to generalize the model, the main beams are assumed to be elastically restrained against translation and rotation at one end and free at the other. Furthermore, the mass-spring system is elastically connected to the beams at adjustable positions by means of four translational and rotational springs. The governing differential equations of the beams and the mass-spring system are derived and analytically solved by using the Fourier transform method. Moreover, as a second way, a finite element solution is derived. The frequency parameters and mode shapes of some diverse cases are obtained using both methods. Comparison of obtained results by two methods shows the accuracy of both solutions. The influence of system parameters on the free vibration response of the studied mechanical system is examined.

• 한국산학기술학회논문지
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• 제12권12호
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• pp.5984-5989
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• 2011

양단 핀지지 기둥부재의 중간 위치에 수평재를 연결하고 설치된 수평재의 양끝단과 기둥의 상하끝단을 트러스로 연결된 트러스보강 단일기둥시스템은 보강되지 않은 경우에 비해 그 좌굴강도가 상당수준 향상될 수 있다. 수평재가 설치된 기둥중간지점에서의 수평 및 회전 자유도에 대한 제한하여 기둥의 유효좌굴길이를 줄이는 효과를 통해 강도향상이 구현된다. 본 연구에서는 해석적 해와 탄성 및 비탄성 유한요소해석을 통해 보강된 평면내 단일기둥 시스템의 좌굴강도를 정량적으로 산정하였고 그 결과를 비교하였다. 예제해석을 통해 보강된 단일기둥시스템은 보강되지 않은 단순기둥에 비해 최대 8배까지 좌굴강도가 향상될 수 있음이 확인되었다.