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The rate of solidification and the effects of local composition on the subsequent nucleation of Al20Cu2Mn3 dispersoid phase in Al-4Cu-0.3Fe-0.4Mn-0.2Si alloys

The rate of solidification and the effects of local composit...

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ictpmcs: 2nd international conference on thermal process modelling and computer simulation

作者： Zoeller, T.L. Sanders Jr., T.H. Mechanical Engineering Grad Box 230 Georgia Institute of Technology 801 Ferst Drive Atlanta GA 30332-0405 United States Materials Science and Engineering Georgia Institute of Technology 771 Ferst Drive Atlanta GA 30332-0245 United States

Following solidification, an aluminum alloy microstructure is highly segregated. The microstructure consists of cored dendrites with various soluble and insoluble phases present in the inter-dendritic regions. The solidification rate has a marked effect on the amount of coring as well as grain dimensions and second phase particle size and spacing. Post-solidification cooling rates as well as subsequent heat treatments also affect the evolution of the microstructure. Understanding the effects of these thermal treatments is important in explaining differences in microstructures that are observed in alloys of identical compositions. The focus of this study is to determine the interaction between the coring of copper across dendrites during solidification and the precipitation of dispersoids during the homogenization treatments of an alloy. An aluminum alloy whose composition is in the range of Al-4Cu-0.3Fe-0.4Mn-0.2Si is ideally suited for this study for several reasons. First it is similar to a host of commercial aluminum copper alloys, and the presence of Mn, Fe, and Si affect the distribution of particles that control grain morphology in these alloys. Preliminary experimental results are discussed. Current numerical analysis techniques will be examined and possible methods to treat the problem will be presented. © EDP Science.

关键词： Aluminum compounds

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An experimental mock-up for the study of steel behaviour at high temperature during phase transformation

An experimental mock-up for the study of steel behaviour at ...

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2nd international conference on thermal process modelling and computer simulation

作者： Vincent, Y Bergheau, JM Leblond, JB Jullien, JF Inst Natl Sci Appl URGC F-69621 Villeurbanne France ENISE ECL LTDS CNRS UMR 5513 F-42023 St Etienne 2 France Univ Paris 06 CNRS LMM UMR 7607 F-75015 Paris France

In most numerical simulations of welding, due to the very short times involved, viscoplastic effects are neglected. However an experimental mock-up developed at INSA has evidenced the possible importance of such effects, which must therefore be incorporated in a more refined description of the material behaviour. This paper presents such a description;an extension of Leblond's model for transformation plasticity, accounting for the dependence of mechanical properties upon strain rate, is proposed. Finite element analyses using elastic-plastic or elastic-viscoplastic constitutive laws are compared with experiments, and it is found that incorporation of viscoplastic effects significantly improves the quality of the agreement between numerical and experimental results.

关键词： Steel heat treatment

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modelling the Marangoni convection in laser heat treatment

Modelling the Marangoni convection in laser heat treatment

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2nd international conference on thermal process modelling and computer simulation

作者： Drezet, JM Pellerin, S Bezençon, C Mokadem, S Calcom ESI SA CH-1015 Lausanne Switzerland Ecole Polytech Fed Lausanne Met Phys Lab CH-1015 Lausanne Switzerland

Epitaxial Laser Metal Forming (E-LMF) consists in impinging a jet of metallic powder onto-a molten pool formed by controlled laser heating and thereby, generating epitaxially a single crystal deposit onto the damaged component. This new technique aims to be used for the repair and reshape single crystal gas turbine components. Because of the very localised melting pool, the high temperature gradients produced during the process must be carefully controlled in order to avoid both the columnar-to-equiaxed transition (CET) and the appearance of hot tears. To this end, heat flow modelling is required to establish the relationship between process parameters such as laser power, beam diameter and scanning speed, and the local solidification conditions. When modelling the heat transfer within the sample, it is necessary to include the liquid flow pattern generated by the surface tension driven convection known as the Marangoni effect. Indeed, the fluid flow in the liquid pool dictates the shape of the traces as shown by the measurements carried Out at EPF-Lausanne in re-melting experiments. A three dimensional (3D) model is implemented in the finite element software calcosoft(R) in order to model the development of the fluid convection within the liquid pool. It is shown that the velocities due to natural convection are of the order of 1 min/sec whereas Marangoni convection produces velocities of the order of 1 m/sec. Moreover, at low scanning speeds, the liquid pool becomes larger than the beam diameter and the development of Marangoni eddies leads to a widening and deepening of the pool. The local solidification conditions such as the thermal gradient and the solidification speed can be extracted at both the solidus and liquidus temperatures to assess the risk of CET and hot cracking.

关键词： Heat treatment

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simulation of gas quenching

Simulation of gas quenching

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2nd international conference on thermal process modelling and computer simulation

作者： Frerichs, F Lübben, T Fritsching, U Lohner, H Rocha, A Löwisch, G Hoffmann, F Mayr, P Stiftung Inst Werkstofftech D-28359 Bremen Germany

The prediction of mechanical behaviour of specimen during heat treatment by means of numerical simulation requires numerous modules e.g. for heat transfer and mechanical behaviour. The quality of predictions depend oil the quality of the applied models within the modules. In this paper the strain hardening model used in the mechanical module will be investigated. For simulation of mechanical behaviour during gas quenching it is first of all necessary to calculate the interaction between gas and specimen. Using simulated flow field and temperature distribution within the gas, the heat transfer coefficient is calculated from computational fluid dynamics. The cooling and further the mechanical behaviour e.g. residual stresses and distortion of the specimen are simulated by a commercial Finite Element program. To investigate strain hardening it is helpful to choose in a first step a material that will not show phase transformations due to heat treatment. Therefore simulation of mechanical behaviour of austenitic cylinders (SAE30300) is investigated. The required thermophysical properties Such as thermal conductivity, density, and specific heat are taken from literature. With the exception of Poisson's ratio the mechanical properties are measured and calculated by own investigations. For description of the temperature dependent stress strain Curves the Ramberg-Osgood model is Used. The simulated results are compared with experimental data in order to decide which model better describes the mechanical response, whether the kinematic or isotropic strain hardening.

关键词： Gas dynamics

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FEM-simulation of the electrode temperature distribution and crater formation.: Part 1:: Breakdown of an electrical discharge

FEM-Simulation of the electrode temperature distribution and...

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2nd international conference on thermal process modelling and computer simulation

作者： Soldera, F Lasagni, A Mücklich, F Univ Saarland Dept Mat Sci D-66041 Saarbrucken Germany

An electrical discharge causes an energy input into the electrode, which melts and evaporates the metal forming a crater on the cathode surface. The larger part of material loss is produced by the ejection of molten particles from the molten pool. From calorimetric results, the amount of energy delivered to the cathode was estimated. Based on FEM, a model was developed to simulate the local temperature increase in the vicinity of the plasma impact zone. Considering phase transitions, it was possible to define a molten and an evaporated region, whose dimensions were compared with the dimensions of experimental craters. Single sparks were produced on cylindrical samples (Pt, Ir, Ru, Al, Au, Ag, Cu, W, Ni, Sn and Pb) in air and nitrogen with pressures ranging from 1 to 9 bar and electrode gaps of 1 and 2 mm. The volumes of experimental craters lay between the volumes of the simulated regions for 5 and 7 bar. For 1 and 3 bar, the volumes of the evaporated regions were overestimated. The shape of the simulated regions showed a very good agreement with the real craters. The relative Volumes of the molten regions showed a very good agreement with the relative volumes of eroded material in the different metals.

关键词： Electrodes

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Studies of the thermo-mechanical material response of a Boron steel by inverse modelling

Studies of the thermo-mechanical material response of a Boro...

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2nd international conference on thermal process modelling and computer simulation

作者： Åkerström, P Oldenburg, M Lulea Univ Technol Dept Appl Phys & Mech Engn S-97187 Lulea Sweden

In numerical forming simulations of the hot stamping process, the lack of reliable material data, especially at higher temperatures gives quite rough estimations of the stamping forces, strains, residual stresses and achieved final product shape. Traditionally, the material is characterised by several isothermal compression or tension tests at elevated temperatures and strain rates. The present work have pointed out an alternative/complementary approach to reduce the number of experiments and to obtain good results by using Gleeble compression tests at continuous cooling with different compression start temperatures. The isothermal mechanical response was established by means of inverse modeling, with start values obtained from isothermal test results. Three different functions describing the flow stress as function of temperature and plastic strain have been tested and compared in usefulness for the steel grade used. The main object function consists of three parts, one from each compression start temperature. The object function in the inverse problem is based on the deviation in compression force-displacement data and radial displacement at the raid point of the specimen. Minimisation of the objective function with respect to the material parameters were performed using ail in-house optimization software which is based on the subplex method. The established material response has been evaluated by comparison with data from a separate forming test. For the boron steel in the austenitic phase, the Nemat-Nasser model was found to describe the material response with acceptable agreement within the temperature and strain interval studied in the experimental validation.

关键词： Boron

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Methodology for modeling the EB-PVD coating process

Methodology for modeling the EB-PVD coating process

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2nd international conference on thermal process modelling and computer simulation

作者： Nastac, L Dax, FR Hanusiak, W Concurrent Technol Corp Pittsburgh PA 15219 USA FMW Composite Syst Bridgeport WV 26330 USA

This paper presents a methodology for modeling and analyzing the Electron Beam-Physical Vapor Deposition (EB-PVD) coating process. The Knudsen (K-n) number for the Current processing conditions is near but smaller than 0.1 so the continuum approach (based on Navier-Stokes equations) is still valid though the dilute gas regime is considered. The methodology developed in this work is applied to optimization of the evaporation and deposition rates and patterns of metal vapors oil ceramic Substrates. The methodology is based on the numerical Solution of evaporation, fluid flow, species transfer, heat transfer, and a deposition/condensation kinetics model. The models developed for the analysis of the coating process include an ingot EB-melting/evaporation model, a computational fluid dynamics (CFD)-vapor distribution/plume dynamics model (chamber model), and a coating-kinetics model. Numerical simulations at the macro-level were conducted using CFD software. The results from the ingot EB-melting/evaporation model are used as input data in the CFD-vapor distribution model. The coating-kinetics model uses as input, data pressure, temperature, and concentration of Ti-6Al-4V (Ti-6-4) vapors computed with the CFD model. To account for the rarefied gas regime (where Knudsen number [K-n] could be larger than 0.1), appropriate low-pressure "boundary slip conditions" with momentum and thermal accommodation coefficients as a function of K,, were used. Numerical results for temperature and Ti-6-4 vapor concentration profiles in the chamber are presented. Experiments conducted at FMW Composite Systems Inc. are also presented.

关键词： Physical vapor deposition

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Structural dynamics and ride comfort of a rail vehicle system

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ADVANCES IN ENGINEERING SOFTWARE 2002年第7-10期33卷 541-552页

作者： Stribersky, A Moser, F Rulka, W Siemens SGP Verkehrstech GmbH A-1110 Vienna Austria DLR Inst Aeroelast Vehicle Syst Dynam D-82230 Wessling Germany

The paper describes the development of a virtual vehicle system using virtual prototyping computer tools. The virtual vehicle is used for the prediction of the structural dynamics. Since the modelling process for complete rail vehicle systems becomes increasingly more complex, time and cost can be saved by the use of a database concept and an automated assembling process for the vehicle of interest. Supported by a modular design concept, vehicle components for a metro train have been modelled and stored as substructures in a specific vehicle component database. Using this database, train configurations up to a three-car train can be assembled very quickly to perform structural dynamics analyses and to predict the ride comfort. Experimental results have been compared with simulation results of the rail vehicle to improve the modelling technique and the accuracy of the developed virtual vehicle system. The mathematical modelling of the rail vehicle system featuring elastic components, the structure of the database as well as numerical and experimental results are presented in this paper. (C) 2002 Civil-Comp. Ltd and Elsevier Science Ltd. All rights reserved.

关键词： virtual prototyping structural dynamics analyses ride comfort rail vehicle system product development lightweight structure computer tool database concept

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Structural dynamics and ride comfort of a rail vehicle system

Structural dynamics and ride comfort of a rail vehicle syste...

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2nd international conference on Engineering Computational Technology/5th international conference on Computational Structures Technology

作者： Stribersky, A Moser, F Rulka, W Siemens SGP Verkehrstech GmbH A-1110 Vienna Austria DLR Inst Aeroelast Vehicle Syst Dynam D-82230 Wessling Germany

关键词： virtual prototyping structural dynamics analyses ride comfort rail vehicle system product development lightweight structure computer tool database concept

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20th international conference on Conceptual Modeling, ER 2001 associated with international Workshop on Conceptual Modeling of Human/Organizational/Social Aspects of Manufacturing Activities, HUMACS 2001, international Workshop on Data Semantics in Web Information Systems, DASWIS 2001, 2nd international Workshop on Conceptual Modeling Approaches for e-Business, ECOMO 2001 and international Workshop on Global Data Modeling in the New Millennium, DAMA 2001

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20th international conference on Conceptual Modeling, ER 2001 associated with international Workshop on Conceptual Modeling of Human/Organizational/SocialAspects of Manufacturing Activities, HUMACS 2001, international Workshop on Data Semantics in Web Information Systems, DASWIS 2001, 2nd international Workshop on Conceptual Modeling Approaches for e-Business, ECOMO 2001 and international Workshop on Global Data Modeling in the New Millennium, DAMA 2001

ISBN: (纸本)3540441220

The proceedings contain 37 papers. The special focus in this conference is on Modeling of Data Semantics for Facilitating Data Dissemination and Design of Next Generation Web Information Systems. The topics include: Challenges in dealing with human factors issues in manufacturing activities;living manufacturing systems with living organizations;construction of virtual working environment and evaluation of the workers;human models and data in the ubiquitous information infrastructure;motion simulation of the human workers for the integrated computer-aided manufacturing process simulation based on info-ergonomics concept;human-body motion simulation using bone-based human model and construction of motion database;dynamic management architecture for human oriented production system;a semantics-based approach for information integration of geospatial data;imposing modeling rules on industrial applications through meta modeling;structuring web sites using audience class hierarchies;on the automatic extraction of data from the hidden web;querying relational databases without explicit joins;a formal analysis of the lightweight directory access protocol;a framework for document centric workflow management system;a multi-perspective methodology for modelling inter-enterprise business processes;seamless personalization of E-commerce applications and using the quantum data model to develop shareable definitions.

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