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Comparison of two hot cracking tests JWRI and CRW Y. Gao, O. Asserin, D. Ayrault, O. Fandeur, M. Ronfard-Haret, D. Solas, P.
Pilvin
To cite this version:
Y. Gao, O. Asserin, D. Ayrault, O. Fandeur, M. Ronfard-Haret, et al.. Comparison of two hot cracking tests JWRI and CRW. FEMS Junior Euromat 2016, Jul 2016, Lausanne, Switzerland. �hal-02442274�
Numerical Simulation JWRI & CRW
Conclusions and further works
Comparison of two hot cracking tests JWRI and CRW
NUCLEAR ENERGY DIRECTORATE
NUCLEAR ACTIVITIES DIRECTORATE OF SACLAY
SYSTEMS AND STRUCTURES MODELING DEPARTMENT
www.cea.fr
• Compare hot cracking tests for different welding processes, TIG and Laser, using 316L(N) stainless steel alloy
• Develop simulation of type CAFE (Cellular Automaton Finite Element) in order to predict granular structures in welds with the help of metallographic observations + EBSD
• Identify the high temperature behavior law with the help of Gleeble simulator tests
• Develop numerical simulations of hot cracking tests to identify a hot cracking thermomechanical criterion
Context
Contact: yuan.gao@cea.fr
Objectives
Solidification hot cracking
may be encountered when
welding 316L(N) using its
filler metals. This material
is used for the reactor
vessel.
Hot cracking is not allowed in
welds according to the rules of
construction and design of
nuclear components
It requires :
• to prevent this risk
• to ensure that the material
exhibits a satisfactory
weldability
• Propose a hot cracking test which realizes the tradeoff between sensitivity and robustness :
sensitivity to differentiate the nuances of the material and to propose a thermomechanical
hot cracking criterion ;
robustness to avoid the operatives uncertainties and get in repeatability conditions.
• Improve the understanding of hot cracking mechanisms and to identify a
thermomechanical hot cracking criterion by means of the numerical simulation of hot
cracking tests.
• Characterize granular structures around the crack areas to couple multiscale approaches
such as CAFE (Cellular Automata Finite Element) for the prediction of the grain structures
with the thermomechanical behavior of the mushy zone.
JWRI test
Restraint test - CRW
Free restraint test - JWRI
JWRI (Joining and Welding Research Institute) test Maintaining of specimen Trapezoidal specimen Gas backside
protection Welding torch
2D simulated temperature field with the hot crack
JWRI test allows :
• to observe a crack arrest • to analyze hot cracking
mechanisms
• to identify a crack arrest criterion
Comparing the simulation results to the experimental data from the literature [1]
[1] N. CONIGLIO, M. PATRY. Science and Technology of Welding and Joining, vol. 18, No 7, p. 573-580, 2013.
Yuan GAO
a,c, Olivier ASSERIN
a, Danièle AYRAULT
a, Olivier FANDEUR
b, Marc RONFARD-HARET
a, Denis SOLAS
d, Philippe PILVIN
ca
CEA, DEN, DANS, DM2S, SEMT, LTA, 91191 Gif-sur-Yvette, France
bCEA, DEN, DANS, DM2S, SEMT, LM2S, 91191 Gif-sur-Yvette, France
c
Université de Bretagne-Sud, LIMATB>IRDL, Rue Saint-Maudé, 56321 Lorient, France
dUniversité de Paris-Sud, ICMMO, Rue du Doyen Georges Poitou, 91405 Orsay, France
IV generation nuclear reactor SFR (Sodium Fast Reactor)
2D simulated stress field
ZF
x y
Stress along Y at 8s
JUNIOR EUROMAT July 10-14 2016
Hot cracking in weldingCRW (Controlled Restraint Weldability) test [1]
Advantage of CRW test • both initiation and
arresting crack
Numerical simulation of this test
• Understand local mechanisms of hot
cracking and to identify a hot crack initiation
criterion
The preferential growth direction is the
<100> direction that is aligned with the
temperature gradient
Metallographic observations and experimental results
Structure of the welding seam for elliptical bath
(a): epitaxial grains growing near the fusion line
(b): competitive growth between grains in the melting zone
Micrograph of the epitaxial area Base metal Molten zone Undersides
Sample for the analysis of the cracked part
15mm
Sample for the analysis of the non cracked part
15mm
cracking Welding direction Observation direction
EBSD cartographic for test for (a)
Welding direction
Energy balance: ρ𝐶𝑝 𝜕𝑇
𝜕𝑡 = −𝑑𝑖𝑣 −𝑘𝑔𝑟𝑎𝑑𝑇 + 𝑤
ρ : material density
𝐶𝑝 : specific heat capacity 𝑇 : temperature
𝑘 : thermal conductivity 𝑤 : volumic heat sources Material : aluminum alloy 6061 Welding process : laser
Stress along Y with a restraint of 86 MPa at point P3 over time
-150 -100 -50 0 50 100 150 200 250 0 2 4 6 8 10 0 200 400 600 800 1000 C o nt ra int e Y Y T em pé ra tu re ( °C )
Contrainte YY avec un chargement 86MPa sur la point P3 de l'éprouvette en fonction du temps
'smy86pa3.csv' u 1:2 'T86pa3.csv' u 1:2
ZF
Blue curve : temperature at point P3 over time Violet curve: stress along Y at point P3 over time
St ress alo n g Y (MP a) Temp er at u re (° C)
The equivalent source :
𝑤 𝑚, 𝑡 = 𝐴𝑒𝑥𝑝 −3 𝑥𝑓
2 + 𝑦 𝑓2
𝑟2
𝐴 : power dissipated in the Gaussian 𝑟 : radius of flux distribution
1000.00µm
(a) (b)
Top view : (a) 𝑉𝑠 = 150 𝑚𝑚/𝑚𝑖𝑛; (b) 𝑉𝑠 = 80 𝑚𝑚/𝑚𝑖𝑛
𝜺
𝒃>
𝜺
𝒂, observation axial grain
Se ns d e s o ud ag e 𝜺𝒂 𝜺𝒃
Mechanical modeling (elastic -plastic constitutive law + thermal expansion) : Hooke’s law: σ𝑖𝑗 = μ ε𝑖𝑗𝑒 + 𝜐 1 − 2𝜐 𝑡𝑟(ε𝑒)δ𝑖𝑗 𝑎𝑛𝑑 μ = (1+υ)𝐸(𝑇) Strain decomposition : ε𝑖𝑗 = ε𝑖𝑗𝑒 + ε𝑖𝑗𝑝 + ε𝑖𝑗𝑡ℎ Plastic flow : ε𝑖𝑗𝑝 = λ 𝜕𝑓(σ𝜕σ 𝑖𝑗) 𝑖𝑗 Thermal expansion : ε𝑖𝑗𝑡ℎ=α(𝑇 − 𝑇0) δ𝑖𝑗
Evolution of the stress along Y between the liquidus temperature and the solidus temperature at different
points of the specimen
-20 -15 -10 -5 0 5 10 15 20 2 3 4 5 6 7 8 9 C o n tra in te YY en tre la T liq et T so l ( M Pa ) Temps (s)
Contrainte YY entre la Tliq et Tsol avec condition soudage A en 86MPa
'smyy1.csv' u 1:2 'smyy2.csv' u 1:2 'smyy3.csv' u 1:2 'smyy4.csv' u 1:2 'smyy5.csv' u 1:2 'smyy6.csv' u 1:2 'smyy7.csv' u 1:2 'smyy8.csv' u 1:2 'smyy9.csv' u 1:2 'smyy10.csv' u 1:2 'smyy11.csv' u 1:2 'smyy12.csv' u 1:2 'smyy13.csv' u 1:2 'smyy14.csv' u 1:2 'smyy15.csv' u 1:2 'smyy16.csv' u 1:2 'smyy17.csv' u 1:2 'smyy18.csv' u 1:2 P1 P2 P6 P8 P9 P10 P11 P12 P13 P174 P15 P16 P17 P18
Stress along Y with a restraint of 86 MPa between Tliq and Tsol
St ress alo n g Y b et w ee n Tliq an d T sol (MP a) Zone fissurée expérimentale [1] P3 P4 P5 P7
2D simulated temperature field
Temperature at 8s
