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Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

Journal of Iron and Steel Research International 2010年第5期17卷 6-10页

作者： YUE Qiang ZOU Zong-shu HOU Qin-fu School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a nonmetallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydropbobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettability can be changed by changing solid-liquid interface tension. The nonmetallic inclusion removal in swirling flow tundish is studied. The result shows that under certain turbulent conditions, *** concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.

关键词： collision aggregation wettability inclusion swirling chamber continuous casting tundish

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Earing Prediction in Cup Drawing using the BBC2008 Yield Criterion

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AIP Conference Proceedings 2011年第1期1383卷

作者： Marko Vrh Miroslav Halilovič Bojan Starman Boris Štok Dan‐Sorin Comsa Dorel Banabic Laboratory for Numerical Modelling & Simulation Faculty of Mechanical Engineering University of Ljubljana Ljubljana ‐ Slovenia Technical University of Cluj Napoca CERTETA Research Centre 103‐105 B‐dul Muncii 400641 Cluj Napoca Romania

The paper deals with constitutive modelling of highly anisotropic sheet metals. It presents FEM based earing predictions in cup drawing simulation of highly anisotropic aluminium alloys where more than four ears occur. For that purpose the BBC2008 yield criterion, which is a plane‐stress yield criterion formulated in the form of a finite series, is used. Thus defined criterion can be expanded to retain more or less terms, depending on the amount of given experimental data. In order to use the model in sheet metal forming simulations we have implemented it in a general purpose finite element code ABAQUS/Explicit via VUMAT subroutine, considering alternatively eight or sixteen parameters (8p and 16p version). For the integration of the constitutive model the explicit NICE (Next Increment Corrects Error) integration scheme has been used. Due to the scheme effectiveness the CPU time consumption for a simulation is comparable to the time consumption of built‐in constitutive models. Two aluminium alloys, namely AA5042‐H2 and AA2090‐T3, have been used for a validation of the model. For both alloys the parameters of the BBC2008 model have been identified with a developed numerical procedure, based on a minimization of the developed cost function. For both materials, the predictions of the BBC2008 model prove to be in very good agreement with the experimental results. The flexibility and the accuracy of the model together with the identification and integration procedure guarantee the applicability of the BBC2008 yield criterion in industrial applications.

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Object-oriented modelling and control in buildings

Object-oriented modelling and control in buildings

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作者： Zupančič, B. Sodja, A. University of Ljubljana Faculty of Electrical Engineering Laboratory for Modelling Simulation and Control Slovenia

ISBN: (纸本)9780975840078

This paper deals with some of the important aspects of the harmonisation of thermal and radiation flows in buildings using an object-oriented multi-domain modelling approach. The traditional modelling approach is based on block-oriented schemes in which causal relations play an important role. However, this causality is artificially generated in order to fulfil the appropriate conditions for a simulation on conventional sequential computers. Fortunately, new concepts based on object-oriented approaches, use physically oriented connections and algebraic manipulations to enable the so-called acausal modelling. Here, all these basic concepts are described and the advantages of the new concepts in comparison with traditional approaches are briefly discussed. We have developed a mathematical model that gives the dependence of the external temperature, the solar radiation, the artificial heating and the roller-blind positioning on the internal room temperature. The approach was a combination of theoretical and experimental modelling. The heat dynamics is caused by the heat conduction, the convection and the solar radiation. In the latter case the transfer of the sun's rays through a glass window was studied, and in many cases simplifications were introduced. Some of the model's constants were determined experimentally, comparing the experimental and simulation results. However, only some basic equations are presented (one can find them in the appropriate references) as the emphasis here is on the object-oriented simulator paradigm. The simulator was originally developed in the Matlab-Simulink environment. However, the main drawback of such a conventional modelling approach soon became apparent - the simulator could only be used for the developed configuration. Almost every structural change demanded a new development from scratch. We were not able to establish a library of reusable sub-models for the walls, windows, etc. For this reason we decided to implement the model i

关键词： Heat conduction

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Discrete PDC control design with observer for trajectory tracking of non-holonomic mobile robot

Discrete PDC control design with observer for trajectory tra...

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作者： Guechi, El-H. Lauber, J. Dambrine, M. Klančar, G. Blažič, S. LAMIH Valenciennes University and Hainaut Cambresis Mont-Houy France Laboratory of Modelling Simulation and Control Faculty of Electrical Engineering Ljubljana Slovenia

ISBN: (纸本)9783902661661

This paper presents a new technique for tracking-error model-based discrete PDC control for non-holonomic mobile robot. This technique consists in rewriting the discrete kinematic error-model of the tracking problem for mobile robot into a discrete TS fuzzy representation and finding a stabilizing controller by solving LMI conditions for tracking-error model in the discrete case. The state variables are filtered using discrete TS fuzzy observer in order to reject perturbations. The reference trajectory is composed by two C3 Bezier curves in order to obtain an ellipse like shape with respect to acceleration limits of the mobile robot. The experimental results are presented here to show the efficiency of the proposed approach.

关键词： Mobile robots

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Discrete PDC control design with observer for trajectory tracking of non-holonomic mobile robot

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IFAC Proceedings Volumes 2009年第19期42卷 170-175页

作者： El-H. Guechi J. Lauber M. Dambrine G. Klančar S. Blažič LAMIH Valenciennes University and Hainaut Cambresis Mont-Houy France Laboratory of Modelling Simulation and Control Faculty of Electrical Engineering Ljubljana Slovenia

Abstract This paper presents a new technique for tracking-error model-based discrete PDC control for non-holonomic mobile robot. This technique consists in rewriting the discrete kinematic error-model of the tracking problem for mobile robot into a discrete TS fuzzy representation and finding a stabilizing controller by solving LMI conditions for tracking-error model in the discrete case. The state variables are filtered using discrete TS fuzzy observer in order to reject perturbations. The reference trajectory is composed by two C 3 Bezier curves in order to obtain an ellipse like shape with respect to acceleration limits of the mobile robot. The experimental results are presented here to show the efficiency of the proposed approach.

关键词： PDC control Discrete TS fuzzy model Trajectory tracking Non-holonomic mobile robot

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Space mapping with adaptive response correction for microwave design optimization

Space mapping with adaptive response correction for microwav...

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作者： Koziel, Slawomir Bandler, John W. Madsen, Kaj School of Science and Engineering Reykjavík University Reykjavík IS-103 Iceland Simulation Optimization Systems Research Laboratory Department of Electrical and Computer Engineering McMaster University Hamilton ON L8S 4K1 Canada Bandler Corporation Dundas ON L9H 5E7 Canada Informatics and Mathematical Modelling Technical University of Denmark DK-2800 Lyngby Denmark

Output space mapping is a technique introduced to enhance the robustness of the space-mapping optimization process in case the space-mapped coarse model cannot provide sufficient matching with the fine model. The technique often works very well;however, in some cases it fails. Especially in the microwave area where the typical model response (e.g., |S21|) is a highly nonlinear function of the free parameter (e.g., frequency), the output spacemapping correction term may actually increase the mismatch between the surrogate and fine models for points other than the one at which the term was calculated, as in the surrogate model optimization process. In this paper, an adaptive response correction scheme is presented to work in conjunction with space-mapping optimization algorithms. This technique is designed to alleviate the difficulties of the standard output space mapping by adaptive adjustment of the response correction term according to the changes of the space-mapped coarse model response. Examples indicate the robustness of our approach. © 2009 IEEE.

关键词： Mapping

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A new efficient explicit numerical integration of constitutive equations: Application to sheet metal forming simulations

A new efficient explicit numerical integration of constituti...

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9th International Conference on Computational Structures Technology, CST 2008

作者： Halilovič, M. Vrh, M. Štok, B. Laboratory for Numerical Modelling and Simulation Faculty of Mechanical Engineering University of Ljubljana Slovenia Kovinoplastika Lož Slovenia

ISBN: (纸本)9781905088232

The paper presents a simple and efficient new numerical scheme for the integration of nonlinear constitutive equations, in which the principle reason for inaccuracy of the classical forward-Euler scheme is effectively eliminated. Properties of the proposed NICE scheme, which was also implemented into ABAQUS/Explicit via User Material Subroutine (VUMAT) interface platform, are compared with the properties of the classical forward-Euler scheme and backward-Euler scheme. The implementation for shell applications needs a particular care, what is respectively treated in the paper. The accuracy of the NICE scheme is demonstrated to be of the same level as experienced by the backward-Euler scheme, if we compare them under condition of the same CPU time consumption. © Civil-Comp Press, 2008.

关键词： Constitutive equations

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Distributed damping of large structures 19

Distributed damping of large structures

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19th International Conference on Adaptive Structures and Technologies 2008, ICAST 2008

作者： Bergamini, Andrea Christen, Rouven Motavalli, Masoud Ermanni, Paolo Empa Laboratory for Mechanics for Modelling and Simulation Überlandstrasse 129 DübendorfCH-8600 Switzerland Empa Laboratory for Structural Engineering Switzerland Centre of Structure Technologies Switzerland

ISBN: (纸本)9781617389870

Adaptive systems are typically viewed as a suitable combination of a base structure (plant) that is enhanced with actuators that act on it based on the input from a controller that compares the actual trajectory of the system with the desired one. While very intensive research is carried out on the latter two elements (actuators and controllers), the effect of variable mechanical impedance of the former (plant) on the global behavior of an adaptive system is generally less exhaustively investigated. The present work deals with the modification of the mechanical properties of simple beams. The application of an electrostatic field between two adjacent layers of a multi-layer beam is expected to be an effective method to modulate the amount of shear stress that can be transferred at the interfaces. This modification of the shear stress transfer within a multi-layer structure and consequently of its stiffness was originally thought as an elegant approach to the suppression of resonant vibrations. While the viability of this approach could be demonstrated in certain cases, the limited shear strength of the electrostatically coupled interfaces currently represents a constraint to its usability for stiffness switching purposes. When the shear strength of the interfaces is exceeded, slipping occurs at the interfaces. A closer look at this situation (that was initially considered as undesirable) has lead to the investigation of the damping properties of electrostatically coupled multi-layer beams. These structures have shown good damping behaviour. First measurements show that a friction damping component is superimposed on the viscous damping of the base (not activated) structure. A more detailed investigation and the consideration of possible applications are planned for the near future.

关键词： Shear stress

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Some Aspects of Thermal and Radiation Flows modelling in Buildings Using Modelica

Some Aspects of Thermal and Radiation Flows Modelling in Bui...

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International Conference on Computer Modeling and simulation, UKSIM

作者： Anton Sodja Borut Zupancic Electrical Engineering Laboratory of Modelling Simulation and Control University of Ljubljana Ljubljana Slovenia

Efficient use of energy in buildings is very important. Special attention is given to the use of passive energy resources as the costs for heating and cooling can be significantly reduced and living conditions at the same time improved. modelling of thermal and radiant flows and illumination is very important in this area and so many models with different aims and complexity were developed in the past. Traditional models have a significant lack of object orientation which represents an important disadvantage, because it is difficult or sometimes even impossible to reuse model components. This paper deals with some activities about a simulator which models thermal and radiation flows in buildings. It was originally developed in Matlab/Simulink environment. With the reimplementation in object-oriented Dymola Modelica environment the quality of simulator was significantly improved in different aspects. However, since distribution of radiation flows is mostly geometrical problem, the reusability is not gained implicitly by using Modelica as it is when using models described by DAE. Additional efforts were needed to make components fully reusable. The proposed solutions significantly increased the possibilities for more complicated building structures modelling.

关键词： Object oriented modeling Mathematical model Buildings Computational modeling Libraries Computer simulation Solid modeling Topology Thermal engineering Laboratories

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Pole placement approaches for linear and fuzzy systems

Pole placement approaches for linear and fuzzy systems

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6th International Symposium on Intelligent Systems and Informatics, SISY 2008

作者： Preitl, S. Precup, R.-E. Clep, P.A. Ursache, I.-B. Fodor, J. Škrjanc, I. Dept. of Automation and Applied Informatics Politehnica University of Timisoara Timisoara Romania Institute of Intelligent Engineering Systems Budapest Tech. Polytechnical Institution Budapest Hungary Laboratory of Modelling Simulation and Control University of Ljubljana Ljubljana Slovenia

The paper investigates several pole placement methods in the linear case and suggests a new pole placement method by means of fuzzy linear equations. The linear methods concern the constant real part poles, the poles places on a circle, Butterworth configurations without and with the correction of the imaginary part, the pole-zero cancellation, and the poles placed on an ellipse. Low order systems are considered. The pole placement methods are compared by the digital simulation of control systems' behaviors with respect to the modification of the reference input. The conclusions are useful for continuous control systems, and they can be extended easily to digital control systems including quasi-continuous ones. ©2008 IEEE.

关键词： Poles

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