The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Wei Chen - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic analytical target cascading a moment matching formulation for multilevel optimization under uncertainty
Journal of Mechanical Design, 2006Co-Authors: Huibin Liu, Wei Chen, Michael Kokkolaras, Panos Y Papalambros, Harrison M KimAbstract:Analytical target cascading (ATC) is a methodology for hierarchical multilevel system Design optimization. In previous work, the deterministic ATC formulation was extended to account for random variables represented by expected values to be matched among subproblems and thus ensure Design consistency. In this work, the Probabilistic formulation is augmented to allow the introduction and matching of additional Probabilistic characteristics. A particular Probabilistic analytical target cascading (PATC) formulation is proposed that matches the first two moments of interrelated responses and linking variables. Several implementation issues are addressed, including representation of Probabilistic Design targets, matching responses and linking variables under uncertainty, and coordination strategies. Analytical and simulation-based optimal Design examples are used to illustrate the new formulation. The accuracy of the proposed PATC formulation is demonstrated by comparing PATC results to those obtained using a Probabilistic all-in-one formulation.
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Probabilistic Design in a sheet metal stamping process under failure analysis
NUMISHEET 2005: Proceedings of the 6th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Process, 2005Co-Authors: Thaweepat Buranathiti, Jian Cao, Cedric Z Xia, Wei ChenAbstract:Sheet metal stamping processes have been widely implemented in many industries due to its repeatability and productivity. In general, the simulations for a sheet metal forming process involve nonlinearity, complex material behavior and tool‐material interaction. Instabilities in terms of tearing and wrinkling are major concerns in many sheet metal stamping processes. In this work, a sheet metal stamping process of a mild steel for a wheelhouse used in automobile industry is studied by using an explicit nonlinear finite element code and incorporating failure analysis (tearing and wrinkling) and Design under uncertainty. Margins of tearing and wrinkling are quantitatively defined via stress‐based criteria for system‐level Design. The forming process utilizes drawbeads instead of using the blank holder force to restrain the blank. The main parameters of interest in this work are friction conditions, drawbead configurations, sheet metal properties, and numerical errors. A robust Design model is created to conduct a Probabilistic Design, which is made possible for this complex engineering process via an efficient uncertainty propagation technique. The method called the weighted three‐point‐based method estimates the statistical characteristics (mean and variance) of the responses of interest (margins of failures), and provide a systematic approach in Designing a sheet metal forming process under the framework of Design under uncertainty.
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Probabilistic analytical target cascading a moment matching formulation for multilevel optimization under uncertainty
Design Automation Conference, 2005Co-Authors: Huibin Liu, Wei Chen, Michael Kokkolaras, Panos Y Papalambros, Harrison M KimAbstract:Analytical target cascading (ATC) is a methodology for hierarchical multilevel system Design optimization. In previous work, the deterministic ATC formulation was extended to account for uncertainties using a Probabilistic approach. Random quantities were represented by their expected values, which were required to match among subproblems to ensure Design consistency. In this work, the Probabilistic formulation is augmented to allow introduction and matching of additional Probabilistic characteristics. Applying robust Design principles, a particular Probabilistic analytic target cascading (PATC) formulation is proposed by matching the first two moments of random quantities. Several implementation issues are addressed, including representation of Probabilistic Design targets, matching interrelated responses and linking variables under uncertainty, and coordination strategies for multilevel optimization. Analytical and simulation-based optimal Design examples are used to illustrate the new PATC formulation. Design consistency is achieved by matching the first two moments of interrelated responses and linking variables. The effectiveness of the approach is demonstrated by comparing PATC results to those obtained using a Probabilistic all-in-one (PAIO) formulation.© 2005 ASME
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sequential optimization and reliability assessment method for efficient Probabilistic Design
Journal of Mechanical Design, 2004Co-Authors: Xiaoping Du, Wei ChenAbstract:Probabilistic optimization Design offers tools for making reliable decisions with the consideration of uncertainty associated with Design variables/parameters and simulation models. In a Probabilistic Design, such as reliability-based Design and robust Design, the Design feasibility is formulated Probabilistically such that the probability of the constraint satisfaction (reliability) exceeds the desired limit. The reliability assessment for Probabilistic constraints often involves an iterative procedure; therefore, two loops are involved in a Probabilistic optimization. Due to the double-loop procedure, the computational demand is extremely high. To improve the efficiency of a Probabilistic Design, a novel method – sequential optimization and reliability assessment (SORA) is developed in this paper. The SORA method employs a single-loop strategy where a serial of cycles of optimization and reliability assessment is employed. In each cycle optimization and reliability assessment are decoupled from each other; no reliability assessment is required within optimization and the reliability assessment is only conducted after the optimization. The key concept of the proposed method is to shift the boundaries of violated deterministic constraints (with low reliability) to the feasible direction based on the reliability information obtained in the previous cycle. Hence the Design is quickly improved from cycle to cycle and the computational efficiency is improved significantly. Two engineering applications, the reliability-based Design for vehicle crashworthiness of side impact and the integrated reliability and robust Design of a speed reducer, are presented to demonstrate the effectiveness of the SORA method.
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sequential optimization and reliability assessment method for efficient Probabilistic Design
Journal of Mechanical Design, 2004Co-Authors: Xiaoping Du, Wei ChenAbstract:Probabilistic Design, such as reliability-based Design and robust Design, offers tools for making reliable decisions with the consideration of uncertainty associated with Design variables/parameters and simulation models. Since a Probabilistic optimization often involves a double-loop procedure for the overall optimization and iterative Probabilistic assessment, the computational demand is extremely high. In this paper, the sequential optimization and reliability assessment (SORA) is developed to improve the efficiency of Probabilistic optimization. The SORA method employs a single-loop strategy with a serial of cycles of deterministic optimization and reliability assessment. In each cycle, optimization and reliability assessment are decoupled from each other; the reliability assessment is only conducted after the deterministic optimization to verify constraint feasibility under uncertainty. The key to the proposed method is to shift the boundaries of violated constraints (with low reliability) to the feasible direction based on the reliability information obtained in the previous cycle. The Design is quickly improved from cycle to cycle and the computational efficiency is improved significantly. Two engineering applications, the reliability-based Design for vehicle crashworthiness of side impact and the integrated reliability and robust Design of a speed reducer, are presented to demonstrate the effectiveness of the SORA method.
H Oumeraci - One of the best experts on this subject based on the ideXlab platform.
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review and analysis of vertical breakwater failures lessons learned
Coastal Engineering, 1994Co-Authors: H OumeraciAbstract:Abstract The failures experienced by vertical and composite breakwaters are briefly reviewed and the main reasons for failures are examined. The objective of this study is threefold: (a) identification of the weak components of the structure-foundation system, (b) illustration of the weak points of past and present Design procedures and (c) development of a research strategy for the improvement of the technical basis for the Design of vertical structures. First, three main categories of the reasons for failures are suggested: (a) reasons inherent to the structure itself, (b) reasons inherent to the prevailing hydraulic and loads conditions, and (c) reasons inherent to the foundation and seabed morphology. These reasons are then sytematically discussed and lessons are drawn which are related to each of the aspects considered. The results suggest that the present Design approaches cannot explain most of the failure modes reported, and that the stability of vertical breakwaters is an integrated and complex problem which can satisfactorily be solved only by dynamic analysis and Probabilistic Design approaches.
J K Vrijling - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic Design of water defense systems in the netherlands
Reliability Engineering & System Safety, 2001Co-Authors: J K VrijlingAbstract:Abstract After the disaster in 1953, a statistical approach to the storm surge levels was chosen and an extrapolated storm surge level would be the basis for dike Design. In recent decades, the development of reliability theory made it possible to assess the flooding risks taking into account the multiple failure mechanisms of a dike section and the length effect. It is pointed out that economic activity in the protected areas has grown considerably since the 1950s and that even more ambitious private and public investments, particularly in infrastructure, are planned. Moreover, the safety of a growing population is at stake. These considerations justify a fundamental reassessment of the acceptability of the flood risks.
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acceptable risk as a basis for Design
Reliability Engineering & System Safety, 1998Co-Authors: J K Vrijling, W Van Hengel, R J HoubenAbstract:Abstract Historically, human civilisations have striven to protect themselves against natural and man-made hazards. The degree of protection is a matter of political choice. Today this choice should be expressed in terms of risk and acceptable probability of failure to form the basis of the Probabilistic Design of the protection. It is additionally argued that the choice for a certain technology and the connected risk is made in a cost-benefit framework. The benefits and the costs including risk are weighed in the decision process. A set of rules for the evaluation of risk is proposed and tested in cases. The set of rules leads to technical advice in a question that has to be decided politically.
Harrison M Kim - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic analytical target cascading a moment matching formulation for multilevel optimization under uncertainty
Journal of Mechanical Design, 2006Co-Authors: Huibin Liu, Wei Chen, Michael Kokkolaras, Panos Y Papalambros, Harrison M KimAbstract:Analytical target cascading (ATC) is a methodology for hierarchical multilevel system Design optimization. In previous work, the deterministic ATC formulation was extended to account for random variables represented by expected values to be matched among subproblems and thus ensure Design consistency. In this work, the Probabilistic formulation is augmented to allow the introduction and matching of additional Probabilistic characteristics. A particular Probabilistic analytical target cascading (PATC) formulation is proposed that matches the first two moments of interrelated responses and linking variables. Several implementation issues are addressed, including representation of Probabilistic Design targets, matching responses and linking variables under uncertainty, and coordination strategies. Analytical and simulation-based optimal Design examples are used to illustrate the new formulation. The accuracy of the proposed PATC formulation is demonstrated by comparing PATC results to those obtained using a Probabilistic all-in-one formulation.
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Probabilistic analytical target cascading a moment matching formulation for multilevel optimization under uncertainty
Design Automation Conference, 2005Co-Authors: Huibin Liu, Wei Chen, Michael Kokkolaras, Panos Y Papalambros, Harrison M KimAbstract:Analytical target cascading (ATC) is a methodology for hierarchical multilevel system Design optimization. In previous work, the deterministic ATC formulation was extended to account for uncertainties using a Probabilistic approach. Random quantities were represented by their expected values, which were required to match among subproblems to ensure Design consistency. In this work, the Probabilistic formulation is augmented to allow introduction and matching of additional Probabilistic characteristics. Applying robust Design principles, a particular Probabilistic analytic target cascading (PATC) formulation is proposed by matching the first two moments of random quantities. Several implementation issues are addressed, including representation of Probabilistic Design targets, matching interrelated responses and linking variables under uncertainty, and coordination strategies for multilevel optimization. Analytical and simulation-based optimal Design examples are used to illustrate the new PATC formulation. Design consistency is achieved by matching the first two moments of interrelated responses and linking variables. The effectiveness of the approach is demonstrated by comparing PATC results to those obtained using a Probabilistic all-in-one (PAIO) formulation.© 2005 ASME
Michael Drass - One of the best experts on this subject based on the ideXlab platform.
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semi Probabilistic calibration of a partial material safety factor for structural silicone adhesives part i derivation
International Journal of Structural Glass and Advanced Materials Research, 2020Co-Authors: Michael Drass, Michael A KrausAbstract:This paper deals with the application of the semi-Probabilistic Design concept (level I) of Eurocode 0 in order to calibrate partial safety factors for structural silicone sealants. In the first part of this article the current legal situation for the application of structural sealants in facades is described, where a new Eurocode-conform Design concept is introduced and compared to existing Design codes (ETAG 002) or national Design protocols (DIBt concept). Basic background on semi-Probabilistic modelling and the general framework for deriving partial material safety factors at a level I stage for structural sealants is given then. The main part of this publication is concerned with determining the specific partial material safety factors for DOWSIL 993 silicone using existing experimental data, which were obtained under the ETAG 002 testing protocol. It is found, that the correct level I calibration of that partial material safety factors are significantly lower compared to currently existing estimates and thus allow for a great optimization of structural sealant Design situation with potentially high economical as well as sustainability benefits.
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semi Probabilistic calibration of a partial material safety factor for structural silicone adhesives part ii verification concept
International Journal of Structural Glass and Advanced Materials Research, 2020Co-Authors: Michael A Kraus, Michael DrassAbstract:This paper deals with the application of the semi-Probabilistic Design concept (level I) to structural silicone sealants where a generally valid verification concept is proposed. The verification concept deals with the classification of silicone adhesive joints into cavitation-insensitive and cavitation-sensitive adhesive joints and at the same time advises which class of material models is necessary for the categorized adhesive joint systems. Furthermore, the static verification of a finite element based limit state analysis is shown within the Design verification concept. The concept is elaborated and documented within this paper and illustrated by the help of an example. In the first part of this paper it was found, that the correct level I calibration of that partial material safety factors are significantly lower compared to currently existing estimates and thus allow for a great optimization of structural sealant Design situations with potentially high economical as well as sustainability benefits.