Developmentofcomputa/onalmicrostructuremodel

AarnePohjonen,PhD,Computa/onalmaterialsscience,

Postdoctoralresearcher,UniversityofOulu,

Aarne.Pohjonen@oulu.fi

I have implemented input files reading and interaction with user interface for Juha Pyykkönen’s code, currently in use at SSAB

UserinterfacedevelopedatVTT(VesaKyllönen)

Priorwork:CoolingmodelbyJuhaPyykkönen

Computa/onalmodelformicrostructureevolu/oninhotrolling

andsubsequentcoolingdevelopedbyA.Pohjonen

Simulateplas%cdeforma%oninrollingprocessandsubsequentcooling,whichbothwillbecoupledwithmicrostructuremodel

Differen8alequa8onsolver(FEM):Plas8city,heatconduc8on.Solvetheequa8onsfor8met

MicrostructuremodelCalculate,forexample:-  Localgrainsizechange-  Localdisloca/ondensity-  Phasechangesincooling

Correc/on:Changeparametersofthedifferen/alequa/onsaccordingtomicrostructuremodelfornext/mestep

Outputlocalstress,strain,straingradient,temperature,etc.neededbymicrostructuremodel

Increase/me,t=t+Δt

Simula/onsandliteratureknowledgetoobtainparameterstomodel

Coupledplas9city/heatconcuc9on/microstructuremodel(Pohjonen)

Setupini/alvaluesforphysicalquan//esρ(x, t0 )cp(x, t0 )h(x, t0 )k(x, t0 )

T (x, t0 )

ρ(x, t)cp(x, t)∂T (x, t)∂t

−∇ k(x, t)∇T (x, t)[ ] = ρ(x, t)h(x, t)

Differen/alequa/onsolverSolvetemperaturedistribu/on,T(x,t),fromthenon-linearheatconduc/onequa/on

Phasetransforma/onmodel

Calculatephysicalquan//esforthenext/mestep

Calculatefrac/onsofphasestransformedduring/mestep(ferrite,pearlite,bainite,martensite)

ρ(x, t +Δt)cp(x, t +Δt)h(x, t +Δt)k(x, t +Δt)

t = t +ΔtIncrease/me

FiniteelementsolverimplementedinFORTRAN90language

ImplementedinFORTRAN90language

Coolingmodel(Pohjonen)

Modelcomparisontoanaly9calresultTime-dependentlinearheatequa9on:(Conduc/onofHeatinSolids,Carslaw,Jaeger,OxfordUniversityPress)

X:simula/onresult,Lines:analy/calsolu/ons

Ready:Heatequa9onsolver

Modelcomparisonstoanaly9calresultsSteadystatecase1.Dirichletboundarycondi8ons2.Heattransferboundarycondi8ons

1.Dirichletboundarycondi8ons:T(0)=0,T(2)=3.0

f(x)=1+x,k(x)=1+x/2

Solu/on:

2.Heattransferboundarycondi8ons:

X:simula/onresult,Lines:analy/calsolu/ons

a=0,b=2.0,Text1=0.0,Text2=3.0h1=10=h2

1.Dirichlet

2.Heattransfer

Ready:Heatequa9onsolver

•  Basedonregressionmodelling,source:Computerassistedmodellingofmetallurgicalaspectsofhotdeforma9onandtransforma9onofsteels

(J.Herman,B.Thomas,U.Loaer)

•  Givesanes/mate,whichcanbefurtheradjustedaccordingtofrac/onalCCTdiagram

•  Themodelcanbeadjustedexactlyforgivensteels,providedexperimentaldataisavailable(frac/onalCCT+Finalfrac/onsofphasestransformed)

Ready:Phasetransforma9onmodel

Phasetransforma9onsimula9on:TH25 simula/onvs.experimental

ExperimentalvaluesfromEUreport:Computerassistedmodellingofmetallurgicalaspectsofhotdeforma9onandtransforma9onofsteels(Phase2)ISBN92-828-5295-4(J-C.Herman,B.Donnay,A.Schmitz,U.Loaer,R.Grossterlinden)

Phasetransforma9onsimula9on:CRM39 simula/onvs.experimental

ExperimentalvaluesfromEUreport:Computerassistedmodellingofmetallurgicalaspectsofhotdeforma9onandtransforma9onofsteels(Phase2)ISBN92-828-5295-4(J-C.Herman,B.Donnay,A.Schmitz,U.Loaer,R.Grossterlinden)

Phasetransforma9onsimula9on:TH25finalphasefrac/ons, simula/onvs.experimental

ExperimentalvaluesfromEUreport:Computerassistedmodellingofmetallurgicalaspectsofhotdeforma9onandtransforma9onofsteels(Phase2)ISBN92-828-5295-4(J-C.Herman,B.Donnay,A.Schmitz,U.Loaer,R.Grossterlinden)

Phasetransforma9onsimula9on:CRM39finalphasefrac/ons, simula/onvsexperimental

ExperimentalvaluesfromEUreport:Computerassistedmodellingofmetallurgicalaspectsofhotdeforma9onandtransforma9onofsteels(Phase2)ISBN92-828-5295-4(J-C.Herman,B.Donnay,A.Schmitz,U.Loaer,R.Grossterlinden)

Pulsedwaterflows

Heatconduc9onandphasetransforma9onsimula9on:-Simula/onseing

W = 10−10sin 2π t1.5s⎛

⎝⎜

⎞

⎠⎟

⎛

⎝⎜

⎞

⎠⎟

⎡

⎣⎢

⎤

⎦⎥lm2s

Calculate:1.Timedependenttemperaturedistribu/on2.Phasestransformedasfunc/onof/me -onsurface -on¼thickness

Heatconduc9onandphasetransforma9onsimula9on:-Timedependenttemperaturedistribu/on

Pulsedwaterflows

Heatconduc9onandphasetransforma9onsimula9on:

-Temperatureatsurface-Temperatureat¼thickness

-Frac/onsofferriteandbainiteformedonsurfaceandon¼thickness

AExperimentaldatarequiredtorunthemodelasfiQedtotheoriginaldata:

1.  Steelcomposi/onandaustenitegrainsize2.  Finalrollingtemperature

1.  Frac/onalCCTdiagramforlinearcooling

rates2.  Transforma/onkine/cs(transformed

austeniteasfunc/onoftemperature//me)3.  Finalphasefrac/onsalercoolingtoroom

temperature

BExperimentaldatarequiredtofitthemodel:

Experimentaldatarequiredforthemodel

Effec/veac/va/onenergyoftransforma/onstart

Nuclea/onandgrowthdescribedbyavramieq.

Effectofalteringcomposi/ontotheeffec/veac/va/onenergyoftransforma/onstart

Ferrite

Bainite

Effectofalteringcomposi/ontotheeffec/veac/va/onenergyoftransforma/onstart

Effectofaustenitedeforma/onTothetransforma/onstart

Gleeblephysicalsimula/on(J.Uusitalo)

FEMnumericalsimula/onwithAbaqusCAE

(A.Pohjonen,J.Ilmola,O.Leinonen)

Plas9citysimula9ons

Microstructureevolu/onduringandalerplas/cdeforma/on

-Anisotropicplas/city-Recrystalliza/on-Disloca/onsubstructures

Effectonphasetransforma/onduringcooling

Effectofhotformingtophasetransforma9on

•  Graphicaluserinterfacefordefiningcoolingpathandcalcula/ngphasesformed

•  Graphicaluserinterfacefores/ma/ngrequiredwatertocoolsteelstriptodesiredtemperaturesincoolingsystem(JoniPaananenBachelorThesis,supervisedbyA.Pohjonen)

Addi9onaltoolsdeveloped

Graphicaluserinterfacefordefiningcoolingpathandcalcula/ngphasesformed

Addi9onaltoolsdeveloped:

TemperatureC

Time(s)

Graphicaluserinterfacefores/ma/ngrequiredwatertocoolsteelstriptodesiredtemperaturesincoolingsystem(JoniPaananenBachelorThesis,supervisesdbyA.Pohjonen)

Addi9onaltoolsdeveloped:

TemperatureC

Distance(m)

Phasetransforma/onmodelTransforma9onstart

Scheil’saddi/vityrule

Kine9csAvramitypefunc/on

Frac/ontransformed

n,a,b,careparametersdeterminedfromExperimentalCCT(inversionofCCTtoTTT)

tiτ (T )i

∑ =1

χ=1−exp(−K(T)tn) K(T ) = exp −a(T − b) 2− c⎡⎣ ⎤⎦

Umemoto1983

τ (T ) determinedfromexperimentalCCT(inversionofCCTtoTTT)

Modelfiaedto960QC/deformedat850°Csimula/onvs.experiment

2d/3dcoupledheatconduc/on/phasetransforma/onsimula/onsforanygeometry(preliminaryresults)

PTmodelcoupledwithElmerFEM

Simulateplas%cdeforma%oninrollingprocessandsubsequentcooling,whichbothwillbecoupledwithmicrostructuremodel

Differen8alequa8onsolver(FEM):Plas8city,heatconduc8on.Solvetheequa8onsfor8met

MicrostructuremodelCalculate,forexample:-  Localgrainsizechange-  Localdisloca/ondensity-  Phasechangesincooling

Correc/on:Changeparametersofthedifferen/alequa/onsaccordingtomicrostructuremodelfornext/mestep

Outputlocalstress,strain,straingradient,temperature,etc.neededbymicrostructuremodel

Increase/me,t=t+Δt

Simula/onsandliteratureknowledgetoobtainparameterstomodel

Coupledplas9city/heatconcuc9on/microstructuremodel(Pohjonen)