GEOMETRY
VALIDATION
MATERIAL
WELD PROCESS
FEA-plattform för realistisk modellering av WPS och dess
inverkan på den strukturella integriteten
Per Lindström, industridoktorand, IWE, teknologie licentiat
Huvudhandledare: professor Lars-Erik Svensson
Handledare: professor Lennart Josefson (Chalmers)
Stockholm, 8 juni 2015
Introduction
•
The project started around year 2000 (few years after the M/S Estonia, M/S MSC
Carla and M/S Erika disasters) in order to satisfy my demand of a tool to be used at
assessment of in-service repair welding projects
•
Computational Welding Mechanics – CWM
CWM Platform in current use by DNV GL Materials Laboratory
•
The CWM platform is used to predict realistic displacements, strains and stresses
•
Large strain theory
•
Strains at welding
γ
γ
o Thermal
o Plastic
o Elastic
Stockholm, 8 juni 2015
γ
γ ≥ 5 grains
≈ 250 – 500 µm
2
Improved platform - thermo-mechanical staggered coupled approach
Stockholm, 8 juni 2015
3
2D CWM versus IIW Round Robin macropicture
Stockholm, 8 juni 2015
4
3D- and 2D CWM versus neutron diffraction measurements
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5
3D- and 2D CWM versus yield strength profile
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6
Fracture mechanics study
•
The crack driving force (CTODCDF) for a ductility dip crack (DDC) hot crack in
ER316LSi weld metal is studied, DDC is created at 50 – 70 % of TS.
Stockholm, 8 juni 2015
7
Design crack vs. Room temp. crack and DDC
CTODmat
CTODmat @ PWHT
Stockholm, 8 juni 2015
8
LS-Dyna weld head model
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3D Weld heat source model
The 3D weld heat power is distributed by a double ellipsoidal “Goldak” weld heat source
𝑄𝛷3𝐷 = 𝑄𝛷3𝐷𝑓 + 𝑄𝛷3𝐷𝑟
𝑄𝛷3𝐷𝑓 =
𝑄𝛷3𝐷𝑟 =
6 3𝑓𝑓 𝑃𝑤
𝑎𝑏𝑐1 𝜋 𝜋
2
3𝑥 2
3𝑦 2 −3(𝑧+𝑣𝑡)
−
−
𝑐12
𝑒 𝑎2 𝑒 𝑏2 𝑒
2
2
3(𝑧+𝑣𝑡)2
3𝑥
3𝑦
−
6 3𝑓𝑎 𝑃𝑤 − 2 − 2
𝑐22
𝑒 𝑎 𝑒 𝑏 𝑒
𝑎𝑏𝑐2 𝜋 𝜋
𝑓𝑓 + 𝑓𝑟 = 2
Stockholm, 8 juni 2015
10
Improved 2D Weld heat source model
Weld heat flux distribution in the xy-plane
as a function of the time
Gaussian distribution of
the 2D weld heat flux
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11
Improved 2D Weld heat flux density load curve
1. The equivalent 2D weld heat
flux (PL-QΦ2D) facilitates a
more detailed and physical
correct modelling of the
thermal transients compared
to previous methods
2. The resultant weld heat flux
in the cross section plane is
analysed by 3D CWM
3. The PL-QΦ2D load curve is
created by scaling of the
resultant 3D weld heat flux in
relation to the 2D weld heat
energy
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12
Improved weld filler material’s initiation temperature
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13
Plastic hardening modulus (h) - Plastic strain based
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14
Acknowledgement
The financial support and the support in the form of material and services
from the following organisations is acknowledged:
•
DNV GL
•
KK-stiftelsen (SiCoMaP)
•
Dynamore Nordic AB and LSTC
•
Forsmark Kraftgrupp AB
•
Outokumpu Stainless AB
•
Sheffield Fracture Mechanics
•
Håkan Nilsson Consulting & Maskinteknik i Kil AB
•
Westinghouse Electric Sweden AB
•
SSAB Oxelösund
•
ESAB
•
Lincoln Electric
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EXTRA MATERIAL
TO BE USED IN CASE OF DISCUSSION
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Secant versus Tangent
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316LNSPH
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Improved CWM platform
• Novel 64 Core CWM HPC – Nonlinear implicit FE-solver - MPI
solver
• Quasi dynamic transient nonlinear thermo-mechanical staggered
coupled FEA approach
• Large strain theory (Conservative) - 1st Order element formulation
• Realistic 3D weld head manipulation of the ‘Goldak weld heat
source’
• Novel elastic-plastic CWM material model with residual stress
release function at the solution annealing temperature
• Improved 2D weld heat source
• Improved 2D weld heat flux model
• Novel fully 3D nonlinear fracture mechanics FEA
Stockholm, 8 juni 2015
19
γ
γ
γ
γ ≥ 5 grains
≈ 250 – 500 µm
Large strain theory
εtrue > 15 % (SSM 2009:16)
1st Order selective reduced
element formulation
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20
Material models
•
Strain hardening and WRS are released at a specified temperature
•
The base and weld material can only retain and build up WRS at temperatures
below the WRS release temperature
•
Weld material to be activated in a later sequence of a multi-pass weld
simulation, so called quiet material, is also described by the material models
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21
Residual stress release
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Plastic strain based h v.s. Elastic strain based h
“This small value of
tangent modulus
is used to avoid
convergence issues
during the numerical
analysis”
Bhatti, A.C., Barsoum, Z.A.B,
Murakawa, H.C., Barsoum,
I.,2015, “Influence of thermomechanical material properties
of different steel grades on
welding residual stresses and
angular distortion”, Materials and
Design 65 (2015), pp 878–889
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