Sequential optimization and reliability assessment based on dimension reduction method for accurate and efficient reliability-based design optimization

임종민,이병채,이익진 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

This study develops an efficient and accurate methodology for reliability-based design optimization (RBDO) by combining the mostprobable point (MPP)-based dimension reduction method (DRM) to enhance accuracy and the sequential optimization and reliabilityassessment (SORA) to enhance efficiency. In many researches, first-order reliability method (FORM) has been utilized for RBDO methodsdue to its efficiency and simplicity. However, it might not be accurate enough for highly nonlinear performance functions. Therefore,the MPP-based DRM is introduced for the accurate reliability assessment in this study. Even though the MPP-based DRM significantlyimproves the accuracy, additional computations for the moment-based integration are required. It is desirable to reduce the number ofreliability analyses in the RBDO process. Since decoupled approaches such as SORA reduce necessary reliability analyses considerably,DRM-based SORA is proposed in this study for accurate and efficient RBDO. Furthermore, convex linearization is introduced to approximateinactive probabilistic constraints to additionally improve the efficiency. The efficiency and accuracy of the proposed methodare verified through numerical examples.

Reliability-based Topology Optimization of Electro-Thermal-Compliant Mechanisms with a New Material Mixing Method

조강희,한석영,박재용,임민규 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

Electro-thermal-compliant mechanisms are mechanisms onto which electric voltage is applied as input. This mechanism is based on the thermal expansion properties of the materials. This study considered all of the convection effects according to layouts produced after each topology optimization process. A new material mixing method based on bi-directional evolutionary structural optimization (BESO) was suggested to obtain optimal topologies for compliant mechanisms composed of two materials. Reliability-based topology optimization (RBTO) based on BESO was also applied to the topology optimizations of the mechanisms. Performance measurement approach (PMA), which estimates has probabilistic constraints that are formulated in terms of the reliability index, was adopted to evaluate the probabilistic constraints. The procedure has been tested in numerical applications, and the results were compared with those obtained by the level set and solid isotropic material with penalization (SIMP) methods for validation of the proposed approaches.

RELIABILITY-BASED TOPOLOGY OPTIMIZATION BASED ON BIDIRECTIONAL EVOLUTIONARY STRUCTURAL OPTIMIZATION USING MULTI-OBJECTIVE SENSITIVITY NUMBERS

K.-H. CHO,박재용,S.-P. RYU,한석영 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.6

Reliability-based topology optimization (RBTO) is used to obtain an optimal topology satisfying given constraints, as well as to consider uncertainties in design variables. In this study, RBTO was applied to obtain an optimal topology for the inner reinforcement of a vehicle's hood based on bidirectional evolutionary structural optimization (BESO). A multi-objective topology optimization technique was implemented to obtain the optimal topology for two models with different curvatures while simultaneously considering the static stiffness of bending, torsion, and natural frequency. A performance measure approach (PMA) with probabilistic constraints formulated in terms of the reliability index was employed to evaluate the probabilistic constraints. The optimal topology obtained by RBTO was evaluated and compared to that obtained by deterministic topology optimization (DTO). A more suitable topology was obtained through RBTO than DTO even though the final volume obtained by RBTO was generally slightly greater than that obtained by DTO. The multiobjective optimization technique based on BESO can be applied very effectively with topology optimization for a vehicle's hood reinforcement.

Reliability-Based Topology Optimization Based on Bidirectional Evolutionary Structural Optimization

Jin-Shik Yu(유진식),Sang-Rak Kim(김상락),Jae-Yong Park(박재용),Seog-Young Han(한석영) 한국생산제조학회 2010 한국생산제조학회지 Vol.19 No.4

This paper presents a reliability-based topology optimization (RBTO) based on bidirectional evolutionary structural optimization (BESO). In design of a structure, uncertain conditions such as material property, operational load and dimensional variation should be considered. Deterministic topology optimization (DTO) is performed without considering the uncertainties related to the design variables. However, the RBTO can consider the uncertainty variables because it can deal with the probabilistic constraints. The reliability index approach (RIA) and the performance measure approach (PMA) are adopted to evaluate the probabilistic constraints in this study. In order to apply the BESO to the RBTO, sensitivity number for each element is defined as the change in the reliability index of the structure due to removal of each element. Smoothing scheme is also used to eliminate checkerboard patterns in topology optimization. The limit state indicates the margin of safety between the resistance (constraints) and the load of structures. The limit State function expresses to evaluate reliability index from finite element analysis. Numerical examples are presented to compare each optimal topology obtained from RBTO and DTO each other. It is verified that the RBTO based on BESO can be effectively performed from the results.

An efficient approach to reliability-based design optimization within the enhanced sequential optimization and reliability assessment framework

Hong-Zhong Huang,Xudong Zhang,Debiao Meng,Zhonglai Wang,Yu Liu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6

Reliability based design optimization (RBDO) has been widely implemented in engineering practices for high safety and reliability. It is an important challenge to improve computational efficiency. Sequential optimization and reliability assessment (SORA) has made great efforts to improve computational efficiency by decoupling a RBDO problem into sequential deterministic optimization and reliability analysis as a single-loop method. In this paper, in order to further improve computational efficiency and extend the application of the current SORA method, an enhanced SORA (ESORA) is proposed by considering constant and varying variances of random design variables while keeping the sequential framework. Some mathematical examples and an engineering case are given to illustrate the proposed method and validate the efficiency.

Reliability-based design optimization of structural systems using a hybrid genetic algorithm

Reza Abbasnia,Mohsenali Shayanfar,Ali Khodam 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6

In this paper, reliability-based design optimization (RBDO) of structures is addressed. For this purpose, the global search and optimization capabilities of genetic algorithm (GA) are combined with the efficiency and reasonable accuracy of an advanced moment-based finite element reliability method. For performing RBDO, three variants of GA including a real-coded, a binary-coded and an improved binarycoded GA are developed. In these methods, GA performs (finite element) reliability analyses to evaluate reliability constraints. For truss structures which include finite element modeling, reliability constraints are evaluated using finite element reliability analysis. Response sensitivity required for finite element reliability analysis is obtained by direct differentiation method (DDM) rather than finite difference method (FDM). The proposed methods are examined within four standard test examples and real-world design problems. The results illustrate the superiority and efficiency of the improved binary-coded GA. Results also illustrate that DDM significantly reduces the computational cost and improves the efficiency of the optimization procedure.

Reliability-based design optimization using convex approximations and sequential optimization and reliability assessment method

조태민,이병채 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1

In this study, an effective method for reliability-based design optimization (RBDO) is proposed enhancing sequential optimization and reliability assessment (SORA) method by convex approximations. In SORA, reliability estimation and deterministic optimization are performed sequentially. The sensitivity and function value of probabilistic constraint at the most probable point (MPP) are obtained in the reliability analysis loop. In this study, the convex approximations for probabilistic constraint are constructed by utilizing the sensitivity and function value of the probabilistic constraint at the MPP. Hence, the proposed method requires much less function evaluations of probabilistic constraints in the deterministic optimization than the original SORA method. The efficiency and accuracy of the proposed method were verified through numerical examples.

Reliability-Based Design for Market Systems (RBDMS) : Case Study on Electric Vehicle Design

Ungki Lee(이웅기),Namwoo Kang(강남우),Ikjin Lee(이익진) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

When designing a product, both engineering uncertainty and market heterogeneity should be considered to reduce the risk of failure in the market. Reliability-based design optimization (RBDO) approach allows decision makers to achieve target confidence in product performance under engineering uncertainty. On the other hand, design for market systems (DMS) approach helps decision makers to find profit-maximized product design under market heterogeneity. This paper proposes a reliability-based design for market systems (RBDMS) framework for electric vehicle (EV) design by integrating RBDO and DMS approaches. In RBDO, the product quality is controlled based on arbitrarily defined reliability. However, from the viewpoint of the company, it is necessary to set the appropriate reliability since the increased reliability increases both consumer satisfaction and manufacturing cost. Therefore, by modeling how reliability affects the customer choice, the optimum reliability which maximizes the profit can be derived. The “reliability” in the framework is used as follows: (1) a decision variable; (2) an attribute that directly influences the customer preference; (3) standards to determine advertised performance; and (4) reliability constraints in engineering model. We optimized and compared four scenarios depending on whether engineering systems are deterministic or probabilistic, and whether a market is homogeneous or heterogeneous. The results show that designing an entry EV model with low reliability is recommended under engineering uncertainty and market heterogeneity, while designing a premium EV model with high reliability is recommended to ensure the robustness of the profit.

신뢰성 기반 강건 최적화를 이용한 자동채염기의 확률론적 구조설계

송창용 한국산업융합학회 2020 한국산업융합학회 논문집 Vol.23 No.5

This paper deals with identification of probabilistic design using reliability based robust optimization in structure design of automatic salt collector. The thickness sizing variables of main structure member in the automatic salt collector were considered the random design variables including the uncertainty of corrosion that would be an inevitable hazardousness in the saltern work environment. The probabilistic constraint functions were selected from the strength performances of the automatic salt collector. The reliability based robust optimum design problem was formulated such that the random design variables were determined by minimizing the weight of the automatic salt collector subject to the probabilistic strength performance constraints evaluating from reliability analysis. Mean value reliability method and adaptive importance sampling method were applied to the reliability evaluation in the reliability based robust optimization. The three sigma level quality was considered robustness in side constraints. The probabilistic optimum design results according to the reliability analysis methods were compared to deterministic optimum design results. The reliability based robust optimization using the mean value reliability method showed the most rational results for the probabilistic optimum structure design of the automatic salt collector.

Uncertainty-based MDO for aircraft conceptual design

Park, Hyeong-Uk,Lee, Jae-Woo,Chung, Joon,Behdinan, Kamran Emerald Group Publishing Limited 2015 Aircraft engineering and aerospace technology Vol.87 No.4

<P><B>Purpose</B></P> <P> – The purpose of this paper is to study the consideration of uncertainty from analysis modules for aircraft conceptual design by implementing uncertainty-based design optimization methods. Reliability-Based Design Optimization (RBDO), Possibility-Based Design Optimization (PBDO) and Robust Design Optimization (RDO) methods were developed to handle uncertainties of design optimization. The RBDO method is found suitable for uncertain parameters when sufficient information is available. On the other hand, the PBDO method is proposed when uncertain parameters have insufficient information. The RDO method can apply to both cases. The RBDO, PBDO and RDO methods were considered with the Multidisciplinary Design Optimization (MDO) method to generate conservative design results when low fidelity analysis tools are used. </P> <P><B>Design/methodology/approach</B></P> <P> – Methods combining MDO with RBDO, PBDO and RDO were developed and have been applied to a numerical analysis and an aircraft conceptual design. This research evaluates and compares the characteristics of each method in both cases. </P> <P><B>Findings</B></P> <P> – The RBDO result can be improved when the amount of data concerning uncertain parameters is increased. Conversely, increasing information regarding uncertain parameters does not improve the PBDO result. The PBDO provides a conservative result when less information about uncertain parameters is available. </P> <P><B>Research limitations/implications</B></P> <P> – The formulation of RDO is more complex than other methods. If the uncertainty information is increased in aircraft conceptual design case, the accuracy of RBDO will be enhanced. </P> <P><B>Practical implications</B></P> <P> – This research increases the probability of a feasible design when it considers the uncertainty. This result gives more practical optimization results on a conceptual design level for fabrication. </P> <P><B>Originality/value</B></P> <P> – It is RBDO, PBDO and RDO methods combined with MDO that satisfy the target probability when the uncertainties of low fidelity analysis models are considered.</P>