Effect and Optimal Design of the Material Constraint in the DMWJ of Nuclear Power Plants
YANG Jie(), WANG Lei
Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering, School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Cite this article:
YANG Jie, WANG Lei. Effect and Optimal Design of the Material Constraint in the DMWJ of Nuclear Power Plants. Acta Metall Sin, 2020, 56(6): 840-848.
The material constraint is an important factor affecting the fracture behavior of dissimilar metal welded joint (DMWJ). For accurately design, manufacture and structure integrity assessment, is necessary to clarify the influence of material constraint on the DMWJ. However, there is still a lack of a systematic research on the influence of material constraint on the fracture behavior of the DMWJ in the current nuclear power plants, and how to improve the fracture resistance of the DMWJ by the optimal design of the material constraint should be considered. In this work, a 52M nickel-based alloy DMWJ in nuclear power plants was selected, the initial crack which located in the heat affected zone (HAZ) was manufactured, and the fracture behaviors of the DMWJ under different material constraints of HAZ, fusion zone (FZ) and near interface zone (NIZ) were studied. In addition, the optimal design of the material constraint was investigated. The results show that for the HAZ crack, the J-resistance curves increase monotonously with increasing the strength of HAZ where the crack is located in. And the J-resistance curves increase firstly, then decrease and remain steady with increasing the strength of FZ and NIZ where the crack is nearby. The optimized DMWJs have higher J-resistance curves, and when Ms (HAZ): Ms (FZ):Ms (NIZ)=2:1.4:0.84, the optimized DMWJ has the highest J-resistance curve which is several times of the current J-resistance curve.
Fig.1 Connection diagram of the dissimilar metal welded joint (DMWJ) with nozzle and safety end of nuclear pressure vessel Color online
Fig.2 The DMWJ (a) and different subareas near the A508/52Mb interface (b) (HAZ—heat affected zone, FZ—fusion zone, NIZ—near interface zone; unit: mm)
Material
C
S
P
Si
Mn
Ni
Cr
Mo
Cu
Al
Ti
Co
Fe
Nb
A508
0.200
0.001
0.005
0.20
1.36
0.96
0.17
0.47
-
-
-
-
Bal.
-
316L
0.025
0.001
0.005
0.52
1.73
11.69
17.89
2.43
-
-
-
-
Bal.
-
52Mb
0.020
<0.001
0.003
0.14
0.25
60.39
28.91
0.01
0.01
0.67
0.56
0.01
9.03
<0.01
52Mw
0.025
0.001
0.004
0.18
0.24
58.00
29.18
0.01
0.02
0.75
0.53
0.02
10.23
<0.01
Table 1 Chemical compositions of the four materials used for fabrication of the DMWJ[35]
Fig.3 The true stress-strain curves of the four materials composed of the DMWJ and different subareas
Fig.4 The sampling (a) and geometry (b) of the single edge-notched bend (SENB) specimen (L—distance between the two support points, W—specimen width, B—specimen thickness, F—load) Color online
Material
q1
q2
q3
εΝ
SN
fN
f0
fC
fF
A508
1.5
1
2.25
0.3
0.1
0.002
0.00008
0.04
0.25
316L
1.5
Variable
2.25
0.3
0.1
0.002
0.000001
0.04
0.25
52Mb
1.5
Variable
2.25
0.3
0.1
0.002
0.000001
0.04
0.25
52Mw
1.5
1
2.25
0.3
0.1
0.002
0.00015
0.04
0.25
HAZ
1.5
1
2.25
0.3
0.1
0.002
0.00015
0.04
0.25
FZ
1.5
1
2.25
0.3
0.1
0.008
0.00080
0.01
0.15
NIZ
1.5
1
2.25
0.3
0.1
0.002
0.00004
0.04
0.25
Table 2 The Gurson-Tvergaard-Needleman (GTN) damage parameters of different materials[36]
Fig.5 The whole meshes of the SENB specimen (a) and the local meshes at the crack tip (b)
Fig.6 The effects of material constraint changing in HAZ on the J-resistance (J-R) curves (a) and crack growth paths (b) (Δa—crack extension, Ms—ratio of the strength after deformation to the strength before deformation under the same strain)
Fig.7 The effects of material constraint changing in FZ on the J-R curves (a) and crack growth paths (b)
Fig.8 The crack growth path at Ms=0.5 (VVF—void volume fraction) Color online
Fig.9 The effects of material constraint changing in NIZ on the J-R curves (a) and crack growth paths (b)
Fig.10 The crack growth path of un-deformed meshes (a) and deformed meshes (b) at Ms=0.6 Color online
Fig.11 The J-R curves under different optimized material constraints
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