• Title, Summary, Keyword: System Reliability Optimization

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Barrier Function Method in Reliability Based Design Optimization (장애함수법에 의한 신뢰성기반 최적설계)

  • Lee, Tae-Hee;Choi, Woon-Yong;Kim, Hong-Sun
    • Proceedings of the KSME Conference
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    • pp.1130-1135
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    • 2003
  • The need to increase the reliability of a structural system has been significantly brought in the procedure of real designs to consider, for instance, the material properties or geometric dimensions that reveal a random or incompletely known nature. Reliability based design optimization of a real system now becomes an emerging technique to achieve reliability, robustness and safety of these problems. Finite element analysis program and the reliability analysis program are necessary to evaluate the responses and the probabilities of failure of the system, respectively. Moreover, integration of these programs is required during the procedure of reliability based design optimization. It is well known that reliability based design optimization can often have so many local minima that it cannot converge to the specified probability of failure. To overcome this problem, barrier function method in reliability based design optimization is suggested. To illustrate the proposed formulation, reliability based design optimization of a bracket is performed. AMV and FORM are employed for reliability analysis and their optimization results are compared based on the accuracy and efficiency.

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A Heuristic Algorithm for the Reliability Optimization of a Distributed Communication Network

  • Hung, Chih-Young;Yang, Jia-Ren;Park, Dong-Ho;Liu, Yi-Hsin
    • International Journal of Reliability and Applications
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    • v.9 no.1
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    • pp.1-5
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    • 2008
  • A heuristic algorithm for reliability optimization of a distributed network system is developed so that the reliability of a large system can be determined efficiently. This heuristic bases on the determination of maximal reliability set of maximum node capacity, maximal link reliability and maximal node degree.

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RELIABILITY-BASED DESIGN OPTIMIZATION OF AN AUTOMOTIVE SUSPENSION SYSTEM FOR ENHANCING KINEMATIC AND COMPLIANCE CHARACTERISTICS

  • CHOI B.-L.;CHOI J.-H.;CHOI D.-H.
    • International Journal of Automotive Technology
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    • v.6 no.3
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    • pp.235-242
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    • 2005
  • This study introduces the Reliability-Based Design Optimization (RBDO) to enhance the kinematic and compliance (K & C) characteristics of automotive suspension system. In previous studies, the deterministic optimization has been performed to enhance the K & C characteristics. Unfortunately, uncertainties in the real world have not been considered in the deterministic optimization. In the design of suspension system, design variables with the uncertainties, such as the bushing stiffness, have a great influence on the variation of the suspension performances. There is a need to quantify these uncertainties and to apply the RBDO to obtain the design, satisfying the target reliability level. In this research, design variables including uncertainties are dealt as random variables and reliability of the suspension performances, which are related the K & C characteristics, are quantified and the RBDO is performed. The RBD-optimum is compared with the deterministic optimum to verify the enhancement in reliability. Thus, the reliability of the suspension performances is estimated and the RBD-optimum, satisfying the target reliability level, is determined.

A Reliability Optimization Problem of System with Mixed Redundancy Strategies (혼합 중복전략을 고려한 시스템 신뢰도 최적화 문제)

  • Kim, Heung-Seob;Jeon, Geon-Wook
    • IE interfaces
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    • v.25 no.2
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    • pp.153-162
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    • 2012
  • The reliability is defined as a probability that a system will operate properly for a specified period of time under the design operating conditions without failure and it has been considered as one of the major design parameters in the field of industries. Reliability-Redundancy Optimization Problem(RROP) involves selec tion of components with multiple choices and redundancy levels for maximizing system reliability with constraints such as cost, weight, etc. However, in practice both active and cold standby redundancies may be used within a particular system design. Therefore, a redundancy strategy(active, cold standby) for each subsystem in order to maximize system reliability is considered in this study. Due to the nature of RROP, i.e. NP-hard problem, A Parallel Particle Swarm Optimization(PPSO) algorithm is proposed to solve the mathematical programming model and it gives consistently better quality solutions than existing studies for benchmark problems.

Reliability Based Design Optimization of the Softwater Pressure Tank Considering Temperature Effect (온도영향을 고려한 연수기 압력탱크의 신뢰성 최적설계)

  • Bae Chul-Ho;Kim Mun-Seong;Suh Myung-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.10
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    • pp.1458-1466
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    • 2004
  • Deterministic optimum designs that are obtained without consideration of uncertainties could lead to unrealiable designs. Such deterministic engineering optimization tends to promote the structural system with less reliability redundancy than obtained with conventional design procedures using the factor of safety. Consequently, deterministic optimized structures will usually have higher failure probabilities than unoptimized structures. This paper proposes the reliability based design optimization technique fur apressure tank considering temperature effect. This paper presents an efficient and stable reliability based design optimization method by using the advanced first order second moment method, which evaluates a probabilistic constraint for more accuracy. In addition, the response surface method is utilized to approximate the performance functions describing the system characteristics in the reliability based design optimization procedure.

OPTIMAL RELIABILITY DESIGN FOR THIN-WALLED BEAM OF VEHICLE STRUCTURE CONSIDERING VIBRATION

  • Lee, S.B.;Baik, S.;Yim, H.J.
    • International Journal of Automotive Technology
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    • v.4 no.3
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    • pp.135-140
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    • 2003
  • In the deterministic optimization of a structural system, objective function, design constraints and design variables, are treated in a nonstatistical fashion. However, such deterministic engineering optimization tends to promote the structural system with lest reliability redundancy than obtained with conventional design procedures using the factor of safety. Consequently, deterministic optimized structures will usually have higher failure probabilities than unoptimized structures. Therefore, a balance must be developed between the satisfactions of the design requirements and the objectives of reducing manufacturing cost. This paper proposes the reliability-based design optimization (RBDO) technique, which enables the optimum design that considers confidence level for the vibration characteristics of structural system. Response surface method (RSM) is utilized to approximate the performance functions describing the system characteristics in the RBDO procedure. The proposed optimization technique is applied to the pillar section design considering natural frequencies of a vehicle structure.

System RBDO of truss structures considering interval distribution parameters

  • Zaeimi, Mohammad;Ghoddosian, Ali
    • Structural Engineering and Mechanics
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    • v.70 no.1
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    • pp.81-96
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    • 2019
  • In this paper, a hybrid uncertain model is applied to system reliability based design optimization (RBDO) of trusses. All random variables are described by random distributions but some key distribution parameters of them which lack information are defined by variation intervals. For system RBDO of trusses, the first order reliability method, as well as monotonicity analysis and the branch and bound method, are utilized to determine the system failure probability; and Improved (${\mu}+{\lambda}$) constrained differential evolution (ICDE) is employed for the optimization process. System reliability assessment of several numerical examples and system RBDO of different truss structures are proposed to verify our results. Moreover, the effect of different classes of interval distribution parameters on the optimum weight of the structure and the reliability index are also investigated. The results indicate that the weight of the structure is increased by increasing the uncertainty level. Moreover, it is shown that for a certain random variable, the optimum weight is more increased by the translation interval parameters than the rotation ones.

Reliability-Based Optimal Design of Pillar Sections Considering Fundamental Vibration Modes of Vehicle Body Structure (차체 기본 진동 모드를 고려한 필러 단면의 신뢰성 최적설계)

  • Lee Sang Beom;Yim Hong Jae
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.6
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    • pp.107-113
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    • 2004
  • This paper presents the pillar section optimization technique considering the reliability of the vehicle body structure consisted of complicated thin-walled panels. The response surface method is utilized to obtain the response surface models that describe the approximate performance functions representing the system characteristics on the section properties of the pillar and on the mass and the natural frequencies of the vehicle B.I.W. The reliability-based design optimization on the pillar sections Is performed and compared with the conventional deterministic optimization. The FORM is applied for the reliability analysis of the vehicle body structure. The developed optimization system is applied to the pillar section design considering the fundamental natural frequencies of passenger car body structure. By applying the proposed RBDO technique, it can be possible to optimize the pillar sections considering the reliability that engineers require.

A k-out-of-n System Reliability Optimization Problem with Mixed Redundancy (혼합 중복 k-out-of-n 시스템 신뢰도 최적화 문제)

  • Baek, Seungwon;Jeon, Geonwook
    • Journal of Korean Institute of Industrial Engineers
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    • v.39 no.2
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    • pp.90-98
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    • 2013
  • The k-out-of-n system with mixed redundancy is defined as k-out-of-n system which both includes warm-standby and cold-standby components. In case that operating components in the system fail and the system needs quick transition of standby components to operation state, the k-out-of-n system with mixed redundancy is useful for decreasing system failure rate and operational cost. Reliability-Redundancy Optimization Problem (RROP) involves selection of components with multiple choices and redundancy levels for maximizing system reliability with constraints such as cost, weight, etc. A solution methodology by using harmony search algorithm for RROP of the k-out-of-n system with mixed redundancy to maximize system reliability was suggested in this study.

Reliability Optimization of Urban Transit Brake System For Efficient Maintenance (효율적 유지보수를 위한 도시철도 전동차 브레이크의 시스템 신뢰도 최적화)

  • Bae, Chul-Ho;Kim, Hyun-Jun;Lee, Jung-Hwan;Kim, Se-Hoon;Lee, Ho-Yong;Suh, Myung-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.1
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    • pp.26-35
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    • 2007
  • The vehicle of urban transit is a complex system that consists of various electric, electronic, and mechanical equipments, and the maintenance cost of this complex and large-scale system generally occupies sixty percent of the LCC (Life Cycle Cost). For reasonable establishing of maintenance strategies, safety security and cost limitation must be considered at the same time. The concept of system reliability has been introduced and optimized as the key of reasonable maintenance strategies. For optimization, three preceding studies were accomplished; standardizing a maintenance classification, constructing RBD (Reliability Block Diagram) of VVVF (Variable Voltage Variable Frequency) urban transit, and developing a web based reliability evaluation system. Historical maintenance data in terms of reliability index can be derived from the web based reliability evaluation system. In this paper, we propose applying inverse problem analysis method and hybrid neuro-genetic algorithm to system reliability optimization for using historical maintenance data in database of web based system. Feed-forward multi-layer neural networks trained by back propagation are used to find out the relationship between several component reliability (input) and system reliability (output) of structural system. The inverse problem can be formulated by using neural network. One of the neural network training algorithms, the back propagation algorithm, can attain stable and quick convergence during training process. Genetic algorithm is used to find the minimum square error.