• Title/Summary/Keyword: Reliability-Based Design

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Reliability Optimum Design of Slab System based on Lagrange Multipliers (Lagrange Multipliers에 의한 슬래브시스템의 신뢰성 최적설계)

  • Kim, Hyeon-Seak;Lee, Jeung-Bin;Jung, Chul-Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.1 no.1
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    • pp.113-124
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    • 1997
  • Based on the recent developments of the reliability-based structural analysis and design as well as the extending knowledge on the probabilistic characteristics of load and resistances, the probability based design criteria have been successfully developed for many standards. Since the probabilistic characteristics depend highly on the local load and resistances, it is recognized to develop the design criterion compatible with domestic requirements. The existing optimum design methods, which are generally based on the structural theory and certain engineering exprience, do not realistically consider the uncertainties of load and resistances and the basic reliability concepts. This study is directed to propose a optimum design based Expected Total Cost Minimization on two-way slab system which could possibly replace optimum design based traditional provisions of the current code, based on the AFOSM reliablity theory.

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Reliability-Based Design Optimization of Slider Air Bearings

  • Yoon, Sang-Joon;Choi, Dong-Hoon
    • Journal of Mechanical Science and Technology
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    • v.18 no.10
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    • pp.1722-1729
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    • 2004
  • This paper presents a design methodology for determining configurations of slider air bearings considering the randomness of the air-bearing surface (ABS) geometry by using the iSIGHT. A reliability-based design optimization (RBDO) problem is formulated to minimize the variations in the mean values of the flying heights from a target value while satisfying the desired probabilistic constraints keeping the pitch and roll angles within a suitable range. The reliability analysis is employed to estimate how the fabrication tolerances of individual slider parameters affect the final flying attitude tolerances. The proposed approach first solves the deterministic optimization problem. Then, beginning with this solution, the RBDO is continued with the reliability constraints affected by the random variables. Reliability constraints overriding the constraints of the deterministic optimization attempt to drive the design to a reliability solution with minimum increase in the objective. The simulation results of the RBDO are listed in comparison with the values of the initial design and the results of the deterministic optimization, respectively. To show the effectiveness of the proposed approach, the reliability analyses are simply carried out by using the mean value first-order second-moment (MVFO) method. The Monte Carlo simulation of the RBDO's results is also performed to estimate the efficiency of the proposed approach. Those results are demonstrated to satisfy all the desired probabilistic constraints, where the target reliability level for constraints is defined as 0.8.

Reliability-Based Structural Optimization of Transmission Tower (신뢰성에 기초한 철탑구조물의 최적화에 관한 연구)

  • 김성호;김상효;황학주
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1993.04a
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    • pp.135-140
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    • 1993
  • The optimum weight design of structure is to determine the combination of structural members which minimize the weight of structures and satisfy design conditions as well. Since most of loads and design variables considered in structural design have uncertain natures, the reliability-based optimization techniques need to be developed. The aim of this study is to estabilish the general algorithm for the minimum weight design of transmission tower structure system with reliability constraints. The sequential linear programming method is used to solve non-linear minimization problems, which converts original non-linear programming problems to sequential linear programming problems. The optimal solutions are produced for various reliability levels such as reliability levels inherent in current standard transmission tower cross-section and optimal transmission tower cross-section obtained with constraints of current design criteria as well as selected target reliability index. The optimal transmission towers satisfying reliability constraints sustain consistent reliability levels on all members. Consequently, more balanced optimum designs are accomplished with less structural weight than traditional designs dealing with deterministic design criteria.

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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.

Reliability Design Analysis for Underwater Buriend PBA Based on PoF (고장물리 기반 수중 매설형 PBA에 대한 신뢰성 설계 연구)

  • Kim, Ji-Young;Lee, Ki-Won;Yoon, Hong-Woo;Lee, Seung-Jin;Heo, Jun-Ki;Kwon, Hyeong-Ahn
    • Journal of Applied Reliability
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    • v.17 no.4
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    • pp.280-288
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    • 2017
  • Purpose: PBA buried in underwater requires high reliability because of its mission critical characteristic and harsh operational environment during its life cycle. Therefore, various reliability improvement activities are necessary. The defect on PBA manufacturing process have been studied, as a result, many activities and standards have been presented. However, there are less studies regarding failure pattern on physical features based on design. In this paper, we studied a possible failure patten based on physical features that is related with manufacturing process of PBA. And reliability improvement design based on PoF (Physical of Failure) were intruduced in this paper. Methods: A reliability prediction simulation were performed on the components A and B of the H system using Sherlock Software which is a PoF commercial tool from DFR solution. Solder fatigue and PTH fatigue analysis based on thermal cycling profiles and random vibration was analyzed on three earthquake response spectrum. Result: It was validated that life time and reliability improvement design through solder fatigue and PTH fatigue analysis in case of component. For compoenet B, random vibration fatigue was additionally analyzed and validated reliability for earthquakes profile. Conclusion: In design stage prior to manufacturing, PoF can be analyzed, and it is possible to make a reliability improvement/validated design using design data. This study can be applied in every design step and contribute to make more stable development product.

A New Reliability-Based Optimal Design Algorithm of Electromagnetic Problems with Uncertain Variables: Multi-objective Approach

  • Ren, Ziyan;Peng, Baoyang;Liu, Yang;Zhao, Guoxin;Koh, Chang-Seop
    • Journal of Electrical Engineering and Technology
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    • v.13 no.2
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    • pp.704-710
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    • 2018
  • For the optimal design of electromagnetic device involving uncertainties in design variables, this paper proposes a new reliability-based optimal design algorithm for multiple constraints problems. Through optimizing the nominal objective function and maximizing the minimum reliability, a set of global optimal reliable solutions representing different reliability levels are obtained by the multi-objective particle swarm optimization algorithm. Applying the sensitivity-assisted Monte Carlo simulation method, the numerical efficiency of optimization procedure is guaranteed. The proposed reliability-based algorithm supplying multi-reliable solutions is investigated through applications to analytic examples and the optimal design of two electromagnetic problems.

Design of Reliability Qualification Test Based on Performance Distribution at the Earlier Stage (초기 단계의 성능분포를 활용한 신뢰성 인증시험의 설계)

  • Jeong, Hai-Sung
    • Journal of Applied Reliability
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    • v.12 no.3
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    • pp.131-138
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    • 2012
  • A design of reliability qualification test based on performance distribution is developed. In general, the performance of an item degrades as the time goes by and the failure of an item occurs when the performance degradation reaches the pre-determined critical level. This article considers the reliability qualification test based on a more tightened critical value at the earlier stage to reduce the evaluation testing time and cost. A numerical example is provided to illustrate how to use the developed reliability qualification test.

The Reliability-Based Design Optimization for the Military Communication Equipment considering the Design Uncertainty (설계 불확실성이 고려된 군용 통신 장비의 신뢰성 기반 최적설계)

  • Park, Dae-Woong;Moon, Woo-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.504-509
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    • 2011
  • The military communication equipment is required the high reliability for operating adequate functions under severe conditions. This reliability is the essential element for the quality of the product, for the uncontrolled factors, such as the clearance, damage of the material, the reduction of stiffness, which are the designer is unable to handle. In this paper, the uncertainty for the design was supposed to the probability model for the military communication equipment, and the average of the objective function was minimized for reducing design uncertainty. The reliability-based design optimization which was implemented the limit state function was formulated into the mathematical model, so the reliable optimized structure was implemented than the base-line design.

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A new hybrid method for reliability-based optimal structural design with discrete and continuous variables

  • Ali, Khodam;Mohammad Saeid, Farajzadeh;Mohsenali, Shayanfar
    • Structural Engineering and Mechanics
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    • v.85 no.3
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    • pp.369-379
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    • 2023
  • Reliability-Based Design Optimization (RBDO) is an appropriate framework for obtaining optimal designs by taking uncertainties into account. Large-scale problems with implicit limit state functions and problems with discrete design variables are two significant challenges to traditional RBDO methods. To overcome these challenges, this paper proposes a hybrid method to perform RBDO of structures that links Firefly Algorithm (FA) as an optimization tool to advanced (finite element) reliability methods. Furthermore, the Genetic Algorithm (GA) and the FA are compared based on the design cost (objective function) they achieve. In the proposed method, Weighted Simulation Method (WSM) is utilized to assess reliability constraints in the RBDO problems with explicit limit state functions. WSM is selected to reduce computational costs. To performing RBDO of structures with finite element modeling and implicit limit state functions, a First-Order Reliability Method (FORM) based on the Direct Differentiation Method (DDM) is utilized. Four numerical examples are considered to assess the effectiveness of the proposed method. The findings illustrate that the proposed RBDO method is applicable and efficient for RBDO problems with discrete and continuous design variables and finite element modeling.

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.