• 한국안전학회지
• /
• 제27권6호
• /
• pp.115-121
• /
• 2012

This paper, being the second in a two-part series, presents the robust performance of the proposed design method which can enhance a reliability-based design optimization(RBDO) under the uncertainties of probabilistic models. The robust performances of the solutions obtained by the proposed method, described in the Part 1, are investigated through the parametric studies. A 10-bar truss example is considered, and the uncertain parameters include the number of data observed, and the variations of applied loadings and allowable stresses. The numerical results show that the proposed method can produce a consistent result despite of the large variations in the parameters. Especially, even with the relatively small data set, the analysis results show that the exact probabilistic model can be successfully predicted with optimized design sections. This consistency of estimating appropriate probability model is also observed in the case of the variations of other parameters, which verifies the robustness of the proposed method.

• EDISON SW 활용 경진대회 논문집
• /
• 제4회(2015년)
• /
• pp.223-228
• /
• 2015

In this paper, the study of the optimum design for a geometry of the handle bar to obtain a high stiffness and light weight is investigated, using EDISON simulation program. High stiffness and weight lightening are considered as the major performance indicators of the component of the bicycle. Four design factors and three levels of the design factors are selected for the structural optimization and experiments are designed using the orthogonal array of L9 by Taguchi method. We calculated SN ratio of larger-the-better and smaller-the-better characteristics from FEA results and analysed the effects of design factors on characteristics. We choosed the optimum level of design factors based on deflection and safety factor. Comparing the results of FE analysis with converted value of predicted SN ration, we made sure for reliability of Taguchi method and FE method for structural optimization.

• 한국항공우주학회지
• /
• 제36권5호
• /
• pp.438-447
• /
• 2008

본 논문에서는 이동최소자승법을 이용한 근사모델을 사용하여 신뢰성 최적설계를 수행하였다. 신뢰성 최적설계의 수행을 위한 반응표면 생성에는 RSM 과 Kriging이 사용될 수 있다. RSM은 계산시간은 빠르나 비선형성이 강한 문제에 약하며 Kriging은 비선형성이 강한 문제에 적용할 수 있으나 계산시간이 오래 걸리는 단점이 있다. 이 두 방법을 보완한 방법인 이동최소자승법(MLSM)을 이용하여 신뢰성 최적설계를 위한 반응표면을 생성하였다. 이동최소자승법을 이용한 신뢰성 최적설계기법은 Rosenbrock function 과 six-hump carmel back function으로 검증하였고 다른 기법과 비교하였다. 이동최소자승법을 이용하여 무인항공기 배기 덕트의 신뢰성 최적설계를 수행하였고 이는 항공우주구조물의 최적설계에 유용할 것으로 보여 진다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2013년도 추계학술대회 논문집
• /
• pp.236-240
• /
• 2013

Due to difficulty of considering dynamic load in side of a computer resource and computing time, it is common that external load is assumed as ideal static load. However, structural analysis under static load cannot guarantee the safety of structural design. Recently, the systematic method to construct equivalent static load from the given dynamic load has been proposed. Previous study has calculated equivalent static load through the optimization procedure under displacement constraints. And previously reported works to distribute equivalent static load were based on ad hoc methods. However, it is appropriate to take into account the stress constraint for the safety design. Moreover, the improper selection of loading position may results in unreliable structural design. The present study proposes the methodology to optimize an equivalent static which distributed on the primary DOFs, DOFs of the constraint elements, DOF of an external load as positions. In conclusion, the reliability of proposed method is demonstrated through a global optimization.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1029-1034
• /
• 2004

Recent engineering process requires fast development and manufacturing of the products. This paper mainly discusses the process of rapid product development (RPD) from the reverse engineering to the optimal design. A laser scanning system scans a product and the efficient data processing method reduces the scanned point data. The reduced (scanned) points model is transformed to a finite element model without the construction of a CAD model. Since CAD modeling is a time-consuming work, skipping this step can save much time. This FE model is updated from the result based on the structural characteristics from modal test of the real model. For FE model updating, Response Surface Method is adopted. Finally, the updated FE model is optimized using the reliability-based topology optimization, which is developed recently. All these processes are applied to the design of an upper part model of a cellular phone.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
• /
• pp.154-161
• /
• 2001

A procedure of the design optimization for steel box girder bridges using micro genetic algorithms(μGA) is developed. The effect of population size is investigated and the efficiency and reliability of μGA is demonstrated in the optimum design of steel box girder bridges. Optimum design problems of steel box girder bridges are formulated, where tile design of concrete slab is based on the USD specifications and steel box girder based on LRFD respectively. Design of optimizations of single-span and 2-span steel box girder bridges are performed with the population size of 5, 40, 80, and 120, respectively The μGA-based optimum design of the 3-span steel box girder bridge is compared with SQP results.

• 대한기계학회논문집A
• /
• 제30권9호
• /
• pp.1070-1077
• /
• 2006

In the present study, sizing and shape optimizations are performed based on the reduced system of large-scaled problem. In the analysis part to achieve efficiency and reliability of computation, two-level condensation scheme is applied. In the construction of reduced system of large scaled problems, it is much more efficient to use sub-domain method. Thus, in the present paper, two-level reduction method combined with sub-domain method is employed. Once the reduced system is constructed, it is straightforward to obtain design sensitivities from the analysis results of the reduced system We use semi-analytic method to obtain design sensitivities. Performance of the efficiency and reliability of the present reduction method in the structural optimization problem is demonstrated through the numerical examples. The present framework of reduction method should serve as a fast and reliable design tool in analysis and design of large-scaled dynamic problems.

• Smart Structures and Systems
• /
• 제16권2호
• /
• pp.243-262
• /
• 2015

Optimal sensor placement (OSP) is a critical issue in construction and implementation of a sophisticated structural health monitoring (SHM) system. The uncertainties in the identified structural parameters based on the measured data may dramatically reduce the reliability of the condition evaluation results. In this paper, the information entropy, which provides an uncertainty metric for the identified structural parameters, is adopted as the performance measure for a sensor configuration, and the OSP problem is formulated as the multi-objective optimization problem of extracting the Pareto optimal sensor configurations that simultaneously minimize the appropriately defined information entropy indices. The nondirective movement glowworm swarm optimization (NMGSO) algorithm (based on the basic glowworm swarm optimization (GSO) algorithm) is proposed for identifying the effective Pareto optimal sensor configurations. The one-dimensional binary coding system is introduced to code the glowworms instead of the real vector coding method. The Hamming distance is employed to describe the divergence of different glowworms. The luciferin level of the glowworm is defined as a function of the rank value (RV) and the crowding distance (CD), which are deduced by non-dominated sorting. In addition, nondirective movement is developed to relocate the glowworms. A numerical simulation of a long-span suspension bridge is performed to demonstrate the effectiveness of the NMGSO algorithm. The results indicate that the NMGSO algorithm is capable of capturing the Pareto optimal sensor configurations with high accuracy and efficiency.

• 한국해양공학회지
• /
• 제2권1호
• /
• pp.95-105
• /
• 1988

This paper describes the development of a reliability-based optimum design technique for such three dimensional tubular frames as off shore structures. The objective function is formulated for the structural weight. Constraints that probability of failure for the critical sections does not exceed the allowable probability of failure are set up. In the evaluation of the probability of failure, fatigue as well as buckling and plasticity failure are taken into account and the mean-value first-order second-moment method(MVFOSM) is applied for its calculation. In order to reduce the computing time required for the repeated structural analysis in the optimization process, reanalysis method is also applied. Application to two and three dimensional simple frame structures is performed. The influence of material properties, external forces, allowable failure probabilities and interaction between external forces on the optimum design is investigated.

• Steel and Composite Structures
• /
• 제47권5호
• /
• pp.569-585
• /
• 2023

This paper proposes an efficient approach for the structural topology optimization of bi-directional functionally graded structures by incorporating popular radial basis functions (RBFs) into an implicit level set (ILS) method. Compared to traditional element density-based methods, a level set (LS) description of material boundaries produces a smoother boundary description of the design. The paper develops RBF implicit modeling with multiquadric (MQ) splines, thin-plate spline (TPS), exponential spline (ES), and Gaussians (GS) to define the ILS function with high accuracy and smoothness. The optimization problem is formulated by considering RBF-based nodal densities as design variables and minimizing the compliance objective function. A LS-RBF optimization method is proposed to transform a Hamilton-Jacobi partial differential equation (PDE) into a system of coupled non-linear ordinary differential equations (ODEs) over the entire design domain using a collocation formulation of the method of lines design variables. The paper presents detailed mathematical expressions for BiDFG beams topology optimization with two different material models: continuum functionally graded (CFG) and mechanical functionally graded (MFG). Several numerical examples are presented to verify the method's efficiency, reliability, and success in accuracy, convergence speed, and insensitivity to initial designs in the topology optimization of two-dimensional (2D) structures. Overall, the paper presents a novel and efficient approach to topology optimization that can handle bi-directional functionally graded structures with complex geometries.