• 전산구조공학
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• 제7권3호
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• pp.105-113
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• 1994

프리캐스트 콘크리트(P.C) 대형판 구조물은 일체식 현장타설 철근콘크리트 구조물에 비하여 보통 접합부에서 약한 강성을 가지고 있다. 그러나 일반적으로 실무에서 이러한 P.C대형판 구조물의 특성이 고려되지 않고 있으며 일체식 구조물에서와 동일한 해석모델을 사용하고 있는 실정이다. 따라서 이러한 모델을 사용하요 얻은 해석결과는 실제 P.C구조물에서의 발생하는 것들과 매우 상이할 수 있다. 본 연구에서는 이P.C구조물의 해석에 적합한 몇가지 유한요소모델을 시도해 봄으로써 수직접합부에 실제의 낮은 전단강성을 적용함으로 인해 발생하는 구조물에서의 힘과 응력분포 및 처짐의 변화를 관찰하여 보았다. 마지막으로 실부자들을 위해 수직접합부 전단강성의 영향을 감안한 단순화된 모델이 오차범위에 대한 이해를 전제로 하여 제안되고 있다.

• Steel and Composite Structures
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• 제44권4호
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• pp.519-529
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• 2022

Sandwich structures with the superior mechanical properties such as high stiffness and strength-to-weight ratio, good thermal insulation, and high energy absorption capacity are used today in aerospace, automotive, marine, and civil engineering industries. These structures are composed of moderately stiff, thin face sheets that withstand the majority of transverse and in-plane loads, separated by a thick, lightweight core that resists shear forces. In this research, the finite element technique is used to simulate a sandwich panel with a truss core under axial compressive stress using ABAQUS software. A review of past experimental studies shows that the bondline between the core and face sheets plays a vital role in the critical failure load. Therefore, this modeling analyzes the damage initiation modes and debonding between face sheet and core by cohesive surface contact with traction-separation model. According to the results obtained from the modeling, it can be observed that the adhesive stiffness has a significant influence on the critical failure load of the specimens. To achieve the full strength of the structure as a continuum, a lower limit is obtained for the adhesive stiffness. By providing this limit stiffness between the core and the panel face sheets, sudden failure of the structure can be prevented.

• Tribology and Lubricants
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• 제40권1호
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• pp.8-16
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• 2024

This study conducts numerical modeling and eigen-analysis of a rod-fastened rotor, which is mainly used in aircraft gas turbine engines in which multiple disks are in contact through curvic coupling. Nayak's theory is adopted to calculate surface parameters measured from the tooth profile of the curvic coupling gear. Surface parameters are important design parameters for predicting the stiffness between contact surfaces. Based on the calculated surface parameters, elastoplastic contact analysis is performed according to the interference between two surfaces based on the Greenwood-Williamson model. The equivalent bending stiffness is predicted based on the shape and elastoplastic contact stiffness of the curvic coupling. An equation of motion of the rod-fastened rotor, including the bending stiffness of the curvic coupling, is developed. Methods for applying the bending stiffness of a curvic coupling to the equation of motion and for modeling the equation of motion of a rotor that includes both inner and outer rotors are introduced. Rotordynamic analysis is performed through one-dimensional finite element analysis, and each element is modeled based on Timoshenko beam theory. Changes in bending stiffness and the resultant critical speed change in accordance with the rod fastening force are predicted, and the corresponding mode shapes are analyzed.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.805-815
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• 2003

In order to execute efficiently the free vibration analysis of 2-dimensional structures like plate structures, the author developed the finite element-transfer stiffness coefficient method. This method is based on the combination of the modeling techniques in the FEM and the transfer technique of the stiffness coefficient in the transfer stiffness coefficient method. Numerical results of the simply supported and the elastic supported rectangular plates showed that the present method can be successfully applied to the free vibration analysis of plate structures on a personal computer. We confirmed that, in the case of analyzing the free vibration of rectangular plate structures, the present method is superior to the FEM from the viewpoint of computation time and storage.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권2호
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• pp.153-158
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• 2016

The elastic material constants, stiffness constants ($c_{11}$, $c_{12}$, and $c_{44}$), are three unique coefficients that establish the relation between stress and strain. Accurate knowledge of mechanical properties and the stiffness coefficients for silicon is required for design of Micro-Electro-Mechanical Systems (MEMS) devices for proper modeling of stress and strain in electronic packaging. In this work, the stiffness coefficients for silicon as a function of temperature from $-150^{\circ}C$ to $+25^{\circ}C$ have been extracted by using the experimental measurements of Poisson's ratio (${\nu}$) of silicon in several directions.

• 한국소음진동공학회논문집
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• 제18권4호
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• pp.465-472
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• 2008

An automotive windshield wiper system is modeled mainly for vibration analysis purpose. The model is composed of solid links, ideal joints, imperfect joints to simulate unavoidable manufacturing defects and bushings having stiffness, contact between a wiper blade and a wind screen glass, friction, a spring and an actuator. Main stream of wiper dynamics analysis has been obtaining a closed form of system of equations using Newton's or Lagrange's formula and doing a numerical simulation study to understand and predict the behavior of it. However, the modeling process is complex since a wiper system is of multibody and a contact problem occurs. When imperfection, such as dead zone of a joint and stiffness of a rubber bushing, should be included, the added complexity makes the modeling difficult. Since the imperfection is understood as main cause of problematic vibration, the dynamics model of a wiper system aiming vibration analysis should include such unavoidable manufacturing defects in the model. An open form of dynamic model of a automotive windshield wiper system with imperfect joints using a commercial software is obtained and a simulation analyssis is conducted for vibration reduction study.

• Smart Structures and Systems
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• 제19권5호
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• pp.553-565
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• 2017

Structural modeling of unencapsulated ionic polymer metal composite (u-IPMC) actuators that are used for flapping the insect scale-flapping wing of micro air vehicles (FMAV) in dry environmental conditions is carried out. Structural modeling for optimization of design parameters for retention of water, maximize actuation performance and to study the influence of water activity on the actuation characteristics of u-IPMC is explored for use in FMAV. The influence of equivalent weight of Nafion polymer, cations, concentration of cations, pre-treatment procedures on retention of water of u-IPMCs and on actuation parameters, flapping angle, flexural stiffness and actuation displacement are investigated. IPMC designed with Nafion having equivalent weight 900-1100, pre-heated at $30^{\circ}C$ and with sodium as the cations is promising for optimum retention of water and actuation performance. The actuation parameters while in operation in dry and humid environment with varying water activity can be tuned to desirable frequency, deflection, flap angle and flexural stiffness by changing the water activity and operational temperature of the environment.

• Computers and Concrete
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• 제32권3호
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• pp.339-349
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• 2023

Fast-built construction is a key feature for successful applications of precast concrete (PC) moment frame system in recent construction practices. To this end, by introducing some unique splicing details in precast connections, especially between PC columns including panel zones, use of temporary supports and bracings can be minimized based on their self-sustaining nature. In addition, precast wide beams are commonly adopted for better economic feasibility. In this study, three self-sustaining precast concrete (PC) wide beam-column connection specimens were fabricated and tested under reversed cyclic loadings, and their seismic performances were quantitatively evaluated in terms of strength, ductility, failure modes, energy dissipation and stiffness degradation. Test results were compared with ASCE 41-17 nonlinear modeling curves and its corresponding acceptance criteria. On this basis, an improved macro modeling method was explored for a more accurate simulation. It appeared that all the test specimens fully satisfy the acceptance criteria, but the implicit joint model recommended in ASCE 41-17 tends to underestimate the joint shear stiffness of PC wide beam-column connection. While, the explicit joint model along with concentrated plastic hinge modeling technique is able to present better accuracy in simulating the cyclic responses of PC wide beam-column connections.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.645-654
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• 2011

복층거더 번들형 사장교의 대블럭 가설 중 내풍안정성 확보를 위해 잭업바지 위에 임시벤트를 설치하여 가설 구조계를 지지하는 방안이 검토되었다. 일반적으로 거스트 계수를 곱한 정적 항력으로 임시벤트를 설계하는 경우 거더의 버페팅력에 의해 발생되는 임시벤트의 축력 변동성분을 고려할 수 없으며, 이는 일부 설계기준에 제시된 정적 상향 풍력으로도 평가할 수 없다. 유용한 해결 방안으로 주파수영역 버페팅해석을 수행하고 임시벤트에 작용하는 거더의 반력을 산정하였다. 우선 임시벤트를 해석 모델에 포함하고 거더와의 동적 상호작용을 엄밀히 반영하는 해석을 수행하였으며, 그 결과를 임시벤트가 거더를 받치는 고정 지지점으로 간주하여 해석한 경우의 결과와 비교 검토하였다. 임시벤트의 강성을 고려하는 경우 산정된 임시벤트와 거더 간 작용력은 임시벤트를 고정 지지점으로 간주하여 얻은 반력에 비하여 작은 값을 보였다. 따라서 대상교량의 가설 구조물 내풍설계를 수행하는 경우 임시벤트가 포함된 해석 모델링의 필요성과 버페팅해석을 통한 동적내풍 설계의 유용성을 제시하였다.

• 대한기계학회논문집
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• 제19권7호
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• pp.1657-1664
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• 1995

For dynamic analysis of flexible structures, classical linear modeling has been widely used due to its several good aspects. However, it was found that the modeling often lost its accuracy. So, it is important to know the valid range of the modeling before it is used. more complicated modelings are needed to obtain reliable results only outside the valid range of the classical linear modeling. In this study, some rigid body motions of flexible structures which lead to the failure of the classical linear modeling are investigated. Hybrid deformation variable modeling, which is proved to be accurate in previous studies, is used to figure out the valid range of the classical linear modeling through numerical examples.