material data for welding simulation - ingenieurbüro für …€¦ · · 2012-12-03material data...
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Dr.-Ing. Tobias Loose30.11.2012
Material Data for Welding Simulation
Herdweg 13, D-75045 Wössingen Lkr. KarlsruheCourriel: [email protected] Web: www.tl-ing.de, www.loose.at
Mobil: +49 - 176 6126 8671 Tel: +49 - 7203 329 023 Fax: +49 - 7203 329 025
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About Ingeneering Office Tobias Loose
Numerical Simulation forWelding and Heat Treatment
Consulting - Training - SupportSales of software for
Welding and Heat Treatment Simulation
Welding Simulation since 2004Analysis of distortion and residual stressesof large stuctures
Vicechairman of FA I2 of DVSAdvisory Group for research in welding simulation
Vicepresident of FördervereinWärmebehandlung und Schweißen e.V.(Associacion for Promotion of Welding and Heat Treatment Simulation)
unsere Partner
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Radaj -Triangle on Welding Simulation
MaterialSimulation
ProcessSimulation
StructureSimulation
WeldingSimulation
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Welding Advisory System
WeldWare®
WeldWare®: Research across decades combined in one software:Heat management during welding of steel - structure transformations and properties in the heat affected zone
Software for Welding SimulationWeldWare® - Materialdata and facil calculations
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SimWeld
SimWeld comprises long term research and developement for user friendly welding process simulation performed by
Welding and Joining Institute
of RWTH Aachen.
Software for Welding SimulationSimWeld - welding process simulation
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technical features of Simufact.welding:• easy and quick use• take into account welding specific boundary conditions• quick definition of clamps• suitable for all established welding processes• covers all weld praparations• most important material data available• unfailing calculation
Software for Welding Simulationsimufact.welding - welding structure analysis
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What is the motivation for welding simulation?
After welding is not befor welding
Material properties, the shape and the state of stresses are modified.
Weldability test Rheinbridge Breisach (Germany-France) St 37 von 1962Weld-point-bending test according to Steidl
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What is special in welding simulation
• Temperature• Microstructure with phase transformation• Strain hardening• Reset of material history at melting point
• Thus all material properties needs to be defined– temperature dependend– phase dependendend
• Phase transformation requirese– Phase transformation kinetic– Phase transformation effects
• transformation strain• transformation plasticity
– Mixing law
WeldWare® serves…
• the calculation of the heat management befor welding• the calculation of microstructure and mechanical properties in the HAZ• the determination of necessary preheating temperatures at real components• the supply of data for Finite Element Analysis
WeldWare® uses…
• heat comprehensive regression equations
• welding-CCT-diagrams measured by SLV Mecklenburg-Vorpommern GmbH
• corresponding material data
• cooling time equations
choose material data and adjust chemical composition
default chemical composition of database.Values can be modified
Charge Managementuser charges can be saved in database.
Data check. Values needs to be in the range of the regression limits.
Data Export for FEM
continue Weld Ware
Chargemanagement
Add further charges with own number or name.
Any charges can be saved and later on reloaded.
Estimate K30 Value
K30-Value describes the cooling rate to get less than 30 % martensit. Necessary minimum cooling rate to avoid cracks as a result of martensit and hard spot.
Mechanical properties in HAZ ...
• Hardness• Yield strength• Ultimate strengt• Ultimate strain• Contraction at fracture
depending on cooling rate:
Estimation of welding parameterscalculation of minimum cooling rate
Welding prarmeter to get save the
K30-value
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Input and output parameter for process simulation
Inputparameter:• wire speed• shielding gas• welding velocity• currency / voltage• torch angel• weldposition• geometry of specimem
Output parameter:• weldpool geometry• penetration / undercut• weldability• temperature over time and droplet• controllparameter: weldcurrency, voltace between specimen and torch
Simulation time between 0,5 and 2 minutes
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Fillet weld - modified parameter Variante 2
increase welding speed from 25 cm/min to 50 cm/min
increase wire speedfrom 6 m/min to 10 m/min
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Comparison of fillet weldsVariante 1 - Variante 2
Welding speed: 25 cm/min 50 cm/minWire speed: 6 m/min 10 m/min
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Welding structure analysis workflow of model setup
Description of geometryof specimen - CAD
Method of Finite Elements
FEM
Devide in finte elementsMeshing
WeldingDefinition of equivalent heat source
Material Material properties
Process and setupAllocate material properties
define weld sequence, clamps, loads
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Structure mechanicStructure mechanicDiffusion - carbonatisation Diffusion - carbonatisation
Hydrogen diffusionHydrogen diffusionElektromagnetismElektromagnetism
Temperature
Grain size
Phase transformation
Temperature
Grain size
Phase transformation
Coupled analysisphysics taken into account
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Description of phase transformationCCT and IT
Thermodynamic propertiesThermal conductivityDensitySpecific heat
or Enthalpie
Mechanical propertiesYoungs modulusYield strenghtStrain hardeningThermal strainPoisson coefficient
Material properties for welding structure analysis
Johnson-Mehl-Avrami-KolmogorovKoinstinen-MarburgerLeblond modelNancy modelGrong models
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Phasetransformation - welding steels
Ferritic-perlitic phase (Basematerial)
Hea
tin
g
Austenitisc phase
Coo
ling
increasing cooling rate
Ferrit / Perlit MartensitBainit
krz
kfz
krztrz
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Temperature in °C
Th
erm
al s
trai
n in
%
kfz
transformation strainthermal strain
Transformation strain and transformation plasticity
krz
Transformation plasticity is an aditional strain that occurs when transformation takes place under load.
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Stress-strain curve
Models to describe stress-strain curves:
• ideal elastic (not suitable)• ideal elastic ideal plastic (not suitable)
• isotropic hardening• kinematic hardening• mixed isotropic-kinematic hardening• cycle plasticity:
– Armstrong-Frederick– Chaboche
• annealing, postweld heat treatment:– viscoplasticity (creep)
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Yield strength Re
Temperature in °C
Yie
ld s
tren
gth
Re i
n N
/mm
²
Stress-strain-curve yield
Yield strength as function depending on microstructure and temperature.
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Stress-strain-curve strain hardening
Strain hardening stress as a group of functions for every phase depending on temperature.
true plastic strain pl in m/m
tru
e h
ard
enin
g st
ress
v i
n N
/mm
²
Hardening Ferrit-Perlit S355
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Removal of plastic strain at melting point
At melting point the strain hardening disappears. Thus the material is reset to origin without hardening. This dishardening is taken into account by reset of platic strain.
without removal
with removal
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Removal of plastic strain at melting point
Comparison of longitudinal stress with removalwithout removalof plastic strain.
Simulation is performed without phase transformation.
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• Plate with dimension270 x 200 x 30 mm3 with V/U-shape groove
• austenitic steel (316LNSPH, kf = 275 MPa)
• 2 Layer weld with same filler material as base material: 316L
• TIG Welding with U = 9 V, I = 155 A, v = 0,67 mm/s
IIW Round Robin TestBenchmark for steel without phase transformation
Prof. Dr.-Ing Helmut WohlfahrtDr.-Ing. Marcus Brand
Dipl.-Ing. Jens SakkiettibutraDr.-Ing. Tobias Loose
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Welding direction
Welding direction
longitudinal stress
transversal stress
IIW Round Robin Test
• Isotropic hardening law was used.• Bauschinger effect disappears at temperature over 400 °C• Signficant influence of strain hardening for evaluation of residual stresses
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S355E = 5,83 kJ/cmv = 1,66 mm/s
Nitschke-Pagel TestBenchmark for steel with phase transformation
Measurement: Dr. Nitschke-Pagel, Simulation: Dr. Loose
Distortion measured: w = 0,34 mmDistorion calculated: w = 0,32 mm
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Conclusion and outlook
• The request for material data needed for welding simulation in general was shown
• most important:– temperature dependency
– microstructure dependency
– history dependency
• What is needed in investigation in material properties:– get correct material properties phase dependend
– get the right mixing law
– take into account the material history
– get damage criteria:• cold crack, damage after welding, service or ultimate load
• hot crack
• fatique