• International Journal of Aeronautical and Space Sciences
• /
• 제17권1호
• /
• pp.29-36
• /
• 2016

Tensairity girder is a light weight inflatable fabric structural concept which can be used in road emergency transportation. It uses low pressure air to stabilize compression elements against buckling. With the purpose of obtaining the comprehensive target of minimum deflection and weight under ultimate load, the cross-section and the inner pressure of tensairity girder was optimized in this paper. The Variable Complexity Modeling (VCM) method was used in this paper combining the Kriging approximate method with the Finite Element Analysis (FEA) method, which was implemented by ABAQUS. In the Kriging method, the sample points of the surrogate model were outlined by Design of Experiment (DOE) technique based on Optimal Latin Hypercube. The optimization framework was constructed in iSIGHT with a global optimization method, Multi-Island Genetic Algorithm (MIGA), followed by a local optimization method, Sequential Quadratic Program (SQP). The result of the optimization gives a prominent conceptual design of the tensairity girder, which approves the solution architecture of VCM is feasible and efficient. Furthermore, a useful trend of sensitivity between optimization variables and responses was performed to guide future design. It was proved that the inner pressure is the key parameter to balance the maximum Von Mises stress and deflection on tensairity girder, and the parameters of cross section impact the mass of tensairity girder obviously.

• 한국생산제조학회지
• /
• 제18권3호
• /
• pp.294-299
• /
• 2009

Micro end-milling has been becoming an important machining process to manufacture a number of small products such as micro-devices, bio-chips, micro-patterns and so on. Many related researches have given grand effects to micro end-milling phenomenon, for example, micro end-milling mechanism, cutting force modeling and machinability. This paper strongly concerned actual problem, micro tool deflection, which causes excessive machining errors on the workpiece. Machining error were predicted and measured through a series of test micro cutting and analysis of their SEM images and FEM analysis. Experiments are carried out to validate the approaches.

• Structural Engineering and Mechanics
• /
• 제38권4호
• /
• pp.503-516
• /
• 2011

Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

• 한국CDE학회논문집
• /
• 제4권3호
• /
• pp.247-258
• /
• 1999

With the contemporary CAD/CAM system, where the tool path is generated and verified purely based on the geometric operation, geometric accuracy of the machined surface cannot be guaranteed dut to the cutting mechanics, meaning that the cutting mechanics should be incorporated in some fashion. In this paper, we incorporate the instantaneous cutting force and the tool deflection phenomena in predicting the machined surface for the finish-cut and milling operation. For the given NC dat including cutting conditions, the developed algorithm computes cutting force and deflection amount along the tool trajectory, and outputs the 3D graphic model of the machined surface together with error analysis. The validity and accuracy of the presented method has been tested by the actual cutting experiments. Experimental results and accuracy enhancement method together with implementing architecture of the VMCS (Virtual Machining CAM System) are discussed in the paper.

• Steel and Composite Structures
• /
• 제37권1호
• /
• pp.91-98
• /
• 2020

Steel plate shear walls are recently used as efficient seismic lateral resisting systems. These lateral resistant structures are implemented to provide more strength, stiffness and ductility in limited space areas. In this study, the seismic behavior of the multi-story steel frames with steel plate shear walls are investigated for buildings with 4, 8, 12 and 16 stories using verified computational modeling platforms. Different number of steel moment bays with distinctive lengths are investigated to effectively determine the deflection amplification factor for low-rise and high-rise structures. Results showed that the dissipated energy in moment frames with steel plates are significantly related to the inside panel. It is shown that more than 50% of the dissipated energy under various ground motions is dissipated by the panel itself, and increasing the steel plate length leads to higher energy dissipation capability. The deflection amplification factor is studied in details for various verified parametric cases, and it is concluded that for a typical multi-story moment frame with steel plate shear walls, the amplification factor is 4.93 which is less than the recommended conservative values in the design codes. It is shown that the deflection amplification factor decreases if the height of the building increases, for which the frames with more than six stories would have less recommended deflection amplification factor. In addition, increasing the number of bays or decreasing the steel plate shear wall length leads to a reduction of the deflection amplification factor.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
• /
• pp.115-130
• /
• 1992

The analysis of thermoplastic automotive bumpers needs not only characterizations of the thermomechanical properties of thermoplastic materials but also the finite element method which can solve the problems with a large deflection, an elastic-inelastic deformation, and a change of a contact state. This paper describes the modeling techniques in the finite element analysis in order to get a good prediction of thermoplastic bumper behaviors. Simplification effects of a complex geometry of thermoplastic bumpers are studied by comparing the results from static loading tests and the finite element analysis.

• Structural Engineering and Mechanics
• /
• 제67권4호
• /
• pp.385-390
• /
• 2018

An incongruity is underlined about the analysis of Timoshenko beams subjected to concentrated loads modelled through the use of generalized functions. While for Euler-Bernoulli beams this modeling always leads to effective results, on the contrary, the contemporary assumptions of concentrated external moment, interpreted as a generalized function (doublet), and of shear deformation determine inconsistent discontinuities in the deflection laws. A physical/theoretical explanation of this not-neglecting incongruity is given in the text.

• 대한토목학회논문집
• /
• 제33권5호
• /
• pp.1915-1933
• /
• 2013

본 연구에서는 단일 현장타설말뚝의 가상고정점을 고려한 해석과 기둥-말뚝을 3차원 전체 모델링한 해석을 비교 분석하여 가상고정점 해석법의 적정성을 평가하였다. 또한, 말뚝 길이, 기둥 및 말뚝 직경, 철근비, 지반조건 등 주요 영향인자에 따라 단일 현장타설말뚝의 거동 평가를 수행하였으며, 이를 통해 가상고정점 해석을 보완한 최적 기둥-말뚝 길이비를 분석하였다. 본 연구결과, 가상고정점을 고려한 해석은 전체 모델링한 해석과 비교하여 침하량과 수평변위를 작게 예측하였으나, 반대로 축력과 휨모멘트는 가상고정점을 고려한 해석에서 크게 나타났다. 따라서 가상고정점을 통한 해석법은 실제 구조물 거동과 다른 단부조건으로 단일 현장타설말뚝의 정확한 거동을 파악하기엔 무리가 있음을 알 수 있었으며, 이에 단일 현장타설말뚝의 정확한 설계를 위해서는 3차원 전체 모델링한 해석이 필요한 것으로 판단되었다. 또한 본 연구에서는 하부 말뚝 길이와 말뚝의 허용 수평변위 관계를 통해 최적 기둥-말뚝 길이비를 분석하였으며, 이를 통해 가상고정점을 고려한 설계를 다소 보완한 경제적이고 개선된 단일 현장타설말뚝 설계를 수행할 수 있을 것으로 기대되었다.

• 한국정밀공학회지
• /
• 제20권12호
• /
• pp.135-141
• /
• 2003

For the analysis of machined surface topography and machine-tool chatter, the cutting system is considered to be a single degree of freedom system. This paper presents a modeling method of equivalent vibratory system for precision cutting in end-milling using an impact test, an Autoregressive Moving Average (ARMA) mode] and a bisection method It has been shown that the proposed modeling method provides a good identification of the cutting system. The advantages of the proposed method in comparison to the existing method are that it is very easy and accurate.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2003년도 춘계학술대회 논문집
• /
• pp.382-387
• /
• 2003

This research has investigated structural characteristics of curved two girder bridges proposed for AGT system and analyzed the results of the structural analysis of three different modelings for 3 span continuous bridge, each modeled in grillage modeling, simplified 3D modeling, and detailed 3D modeling respectively. The grillage modeling appeared to be somewhat underestimated in deflection and overestimated in rotation with respect to 3D modelings. Also, it is impossible to make a detailed examination of local buckling and details of cross beams, etc. The point that warping effect cannot be considered may cause the structural analysis unsafe, accordingly the structural analysis of curved two girder bridges should be done with 3D modelings.