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SYSWELDSYSWELDComplete Finite Element Solution for Simulation of

Welding Processes

Josef TejcMECAS ESI s.r.o. , CZ

ESI Group

Company introductionCompany introduction

Uslavska 10 , Pilsen

Czech Republic

e-mail: info@mecasesi.cz

web-page: http://www.mecasesi.cz

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ESI Group’s Virtual Try-Out Space®ESI Group’s Virtual Try-Out Space®

SYSWELD 2003

SYSWELD 2003

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SYSWELD backgroundSYSWELD background

SYSWELD is a part of the SYSWORLD Finite Element program family:

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SYSWELD backgroundSYSWELD background

SYSTUS is a general purpose Finite Element product that provides most of the computation capabilities that can be handled with implicit Finite Element technology. Developed through the last 4 decades and born in the Nuclear Industry, it provides excellent non-linear computation capabilities.Most of the features developed for SYSTUS are shared through the SYSWORLD product family, i.e. it is possible to use them in SYSWELD too.

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General capabilitiesGeneral capabilities

SYSWELD 2003 simulates all physical effects that are related to:

Welding and Heat treatmentCourtesy GM

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Architecture of the codeArchitecture of the code

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Coupled thermo-metallurgical analysisCoupled thermo-metallurgical analysis

Modified heat convection equation:

( ) QATLTPtTCP

jiijij

iii

iii =⋅+

∇

∇−∂∂

∑∑∑<

λρ )(

indexes phase ... time ...

etemperatur ... proportion phase ...

jitTP

,

density mass ... ρ

sources heat ... tyconductivi thermal ...

heat specific ...

Q

Cλ

unit time in to dtransforme phase of proportion ... tiontransforma of heat latent ...

jiA

jiTL

ij

ij →)(

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Non-linear computationsNon-linear computations

SYSWELD covers 50 men years of solver developmentSYSWELD performs non-linear computations with all material properties depending on

TemperaturePhases / material transformationsProportion of chemical elementsAuxiliary variables

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Non-linear computationsNon-linear computations

SYSWELD covers all needed non-linear phenomena

Non-linear heat transfer to any extentNon-linear geometry including large strainsIsotropic and kinematic strain hardening including phase transformationsTransformation plasticityNon-linear mixture rules for the yield stress of phases

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Typical applicationsTypical applications

MIG (metal inert gas) weldingWIG / TIG weldingLaser weldingElectron beam weldingSpot weldingFriction welding

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Main results of a welding simulationMain results of a welding simulation

Temperature field and gradientPhase proportionsHardnessDistortionsResidual stressesPlastic strainsYield stress depending on the mixture of metallurgical phases

Simple Example of Welding SimulationSimple Example of Welding Simulation

Arc Welding of Steel Plate

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Part and process dataPart and process data

Plate thickness: 9mmPlate length: 120mmArc weldingWelding Speed: 5 mm/sButt weld with filler materialMade of S355_J2G3 construction steel

Formulation of the Problem and Related Input Data

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Mesh of the structureMesh of the structure

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Material propertiesMaterial properties

Thermal properties:Thermal conductivitySpecific heat / EnthalpyMass density

Usually, the properties are defined as a function of temperature and metallurgical phases

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DensityDensity

ρ [kg·mm-3]

T [°C]

Austenite

Ferrite, Bainite, Martensite

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Material propertiesMaterial properties

Metallurgical properties = phase transformation kinetics for:

Austenitic transformation during heating (TTA diagram)Transformation to Ferrite, Bainite and Martensiteduring cooling => CCT diagram

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Real CCT diagramReal CCT diagram

T [°C]

t [s]

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Models for phase transformationsModels for phase transformations

Leblond’s model

for diffusion controlled transformation

Koistinen-Marburger law

for Martensitic transformation

( )( )T

PTPTf

dtdP eq

τ−

= ..

rate olingheating/co ... etemperatur ...

time ... mequilibriu phase at proportion ...

proportion phase ...

TTt

PP

eq

&

( )T)b(MsP(T) −−−= exp1

etemperatur start-Martensite ... tcoefficienlaw ...

proportion phase ...

MsbP

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Model of the CCT diagramModel of the CCT diagram

T [°C]

t [s]

Ferrite

Bainite

Martensite

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Material propertiesMaterial properties

Mechanical properties:Young’s modulusPoisson’s ratioThermal strainYield stressStrain hardening

Usually, mechanical properties are defined as a function of temperature and phase proportions

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Yield stressYield stress

Austenite

Martensite

Ferrite

Bainite

T [°C]

σY [MPa]

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Model of heat sourceModel of heat source

Double-ellipsoid heat source

Heat transfer into the structure (t=20 s)

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Clamping conditionsClamping conditions

Symmetry conditions

Computed Thermo-metallurgical Results

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Temperature field at t=20sTemperature field at t=20s

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Temperature evolution (movie)Temperature evolution (movie)

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Austenite evolution (movie)Austenite evolution (movie)

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Bainite evolution (movie)Bainite evolution (movie)

Computed MechanicalResults

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Evolution of displacements (movie)Evolution of displacements (movie)

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Displacements UZ (with phase transf.)Displacements UZ (with phase transf.)

-0.5mm

-1.1mm

Angular distortion

z

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Displacements UZ (without phase transf.)Displacements UZ (without phase transf.)

-0.5mm

-1.1mm

Angular distortion

-1.4mm

Attention: Different scaling!z

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Stress σyy (with phase transf.)Stress σyy (with phase transf.)

Reduced tensile stress level due to phase transformations

y

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Stress σyy (without phase transf.)Stress σyy (without phase transf.)

y

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Stress σxx (with phase transf.)Stress σxx (with phase transf.)

x

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Stress σxx (without phase transf.)Stress σxx (without phase transf.)

x

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SummarySummary

The difference in computed distortions with and without phase transformations is about 30%The difference in computed stresses with and without material transformations is remarkable

Example of an Industrial Application

Example of an Industrial Application

Simulation of Welding of a T-joint Made from AlMgSi

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Courtesy ofCourtesy of

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Process movie (accelerated display)Process movie (accelerated display)

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Description of the taskDescription of the task

A rectangular hollow profile is welded with 4 joints on a thin-walled plateThe computation of distortions during and after welding is extremely sensitive due to general instability of the arrangement

The edges of the plate are freeThe plate is thin-walled and has a low resistance against bending

The welding joints influence each otherTo a certain extent, this is the worst case for simulation engineering

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Evolution of the temperature field (accelerated, scaling from 200°C to 650°C)

Evolution of the temperature field (accelerated, scaling from 200°C to 650°C)

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Displacement UZ after weld 1 (t=5.2s)Displacement UZ after weld 1 (t=5.2s)

Positive buckle at the edge parallel to WELD 1

Z

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Displacement UZ after weld 2 (t=11.3s)Displacement UZ after weld 2 (t=11.3s)

Positive buckles at the edges parallel to WELD1 and WELD2

Z

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Displacement UZ after weld 3 (t=17.4s)Displacement UZ after weld 3 (t=17.4s)

Positive buckles at the edges parallel to WELD1, WELD2 and WELD3

Z

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Displacements UZ after weld 4 (t= 22.10s)Displacements UZ after weld 4 (t= 22.10s)

Still a positive buckle at the edge parallel to WELD1.

However, the contraction of WELD4 decreases the positive buckle of WELD1 and WELD2.

Z

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Cooling from 22 to 1000 s (movie)Cooling from 22 to 1000 s (movie)

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Cooling from 22 to 1000 s (movie)Different scaling!

Cooling from 22 to 1000 s (movie)Different scaling!

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Process movie - evolution of distortions at the edge parallel to WELD 2

Process movie - evolution of distortions at the edge parallel to WELD 2

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Interpretation of resultsInterpretation of results

The computed evolution of the distortions of the edge parallel to WELD2 is nearly coincident with the displacements shown in the process movie The final displacements have been measured to around 6mmThe final displacements computed are around 6mmThe computed displacements correlate well with the experiment

Some of the New Features of

SYSWELD 2003

Some of the New Features of

SYSWELD 2003

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Interfaces PAM-STAMP/SYSWELDInterfaces PAM-STAMP/SYSWELD

In SYSWELD 2003, it is possible to read and write PAM-STAMP mapping files, in order to:

Import results from a stamping simulation in a welding simulationImport results from a welding simulation in a stamping simulation

A typical application is the stamping of welded tailored blanks

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Door panel - real imagesDoor panel - real images

fehlerfrei umgeformtes Bauteil

Courtesy of AUDI

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Interfaces PAM-STAMP/SYSWELDInterfaces PAM-STAMP/SYSWELD

Plastic strains:

Min/Max : 0/0.587

Courtesy of AUDI

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Welding Assembly simulationWelding Assembly simulation

During the last 4 years, ESI software has validated with Industrial partners a new methodology to simulate welding assembly - the local/global approach

The Welding joints are computed outside the global structure in different local models for which all physical phenomena are simulatedThen, the assembly effects in term of global distortions are computed after projection of local models results on the global structure

This methodology presents the advantage to allow the simulation of large parts supported by shell-solid models A simplified method is also available to analyse the influence of the sequence effects and the clamping tools on the distortions of assembly

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Welding Assembly simulationWelding Assembly simulation

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Material databaseMaterial databaseV2003 contains an intensively tested standard material database for Welding and Heat Treatment

heat_treatment.matwelding.mat

The standard databases will be updated continuouslyAn enhanced material database is also available

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Material databaseMaterial database

For Welding, the following materials are availableAlMgSi

Typical automotive aluminium alloyS355J2G3 (1.0570, St 52-3, Fe 510 D1, Fe 510 D1 FF,

CSN 11 523)Typical ship building steel

X20CrNi13 (1.4201, Z20C13, AISI 420, CSN 17 022)Stainless steel

X5CrNi 18 10 (1.4301, Z7CN18-09, AISI 304, CSN 17 240)

Stainless steelDC04 (St 14, St 4, AISI 1008, CSN 11 325)

Typical car body / stamping steel, deep drawing quality

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ESI Group’s solution of present daysESI Group’s solution of present days

SYSWELD:

Complete solution for realistic simulation of welding processes

Process

Product

COMPARISON WITH EXPERIMENTS:

In cooperation with industrial partners a number of experimental projects was done to proof tight agreement between results of simulation and reality.

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ESI Group’s solution of near futureESI Group’s solution of near future

Complete manufacturing chain simulation perfectly reflecting the reality

Welding / Joining

Stamping

CrashStructuralbehavior

Casting

Fatiguestrength