Figure 1.
Assembly of the 1/32 vacuum vessel (VV) mock-up, including PS1 (inboard segment), PS2 (upper segment), PS3 (equatorial segment), and PS4 (lower segment).
Figure 2.
Diagram of the dimension and clamp conditions of the testing coupon.
Figure 3.
(a) Geometry of the U-groove; (b) all weld beads were divided into four layers: bottom layer, second layer, third layer, and cover layer.
Figure 4.
(a) The apparatus of measuring the actual stress; (b) 6 positions (marked as red points) for stress measurements.
Figure 5.
(a) The apparatus of measuring the actual distortion; (b) 11 positions (marked as red points) for distortions measurement; (c) the detailed measurement method of vertical distortions.
Figure 6.
Flow diagram of the direct coupled thermo-elasto-plastic approach.
Figure 7.
The finite element model and restriction points (a, b, c, and d) of the coupon (a point was constrained in X, Y, and Z directions, b point was constrained in X and Y directions, c and d points were constrained in Y direction).
Figure 8.
(a) Mesh refinement for the weld region of the coupon (the red circle); (b) four weld layers of the welding joint represented by four colors; (c) the mesh sizes used in the finite element model.
Figure 9.
3D-double ellipsoidal heat source used in the simulation.
Figure 10.
Colored map of the von Mises stress in simulation. The values on the left represent von Mises effective stress, where different colors indicate different stress values, and route 1 (black line) was chosen to compare the principal stress between simulation and experiment.
Figure 11.
Comparison of the principal stresses between simulation and experiment. (a) The stresses in the Y direction (perpendicular to the welding direction); (b) the stresses in the X direction (parallel to the welding direction).
Figure 12.
Colored map of the angular distortion in simulation. The values on the left represent the displacement, of which positive values indicate distortion in the positive direction of the Z axis and negative values indicate distortion in the negative direction of Z axis. Different colors indicate different distortion values, and route 2 (black line) was chosen to compare the displacement between simulation and experiment.
Figure 13.
Comparison of the angular distortion in Z direction between simulation and experiment.
Figure 14.
The full-size finite element model of the 1/32 VV mock-up, and the red circles represent the mesh refinement zones.
Figure 15.
Constraint conditions in the practical production process of the 1/32 VV mock-up.
Figure 16.
Constraints of the 1/32 VV mock-up in simulation. The blue points represent constrained points corresponding to the practical process, and every point was constrained in X, Y, and Z directions.
Figure 17.
Three welding sequences of the 1/32 VV mock-up: welding anticlockwise in sequence 1, welding clockwise in sequence 2, and welding counterpoint in sequence 3.
Figure 18.
Colored maps of welding stresses in the three different sequences. The values on the left represent von Mises effective stress, different colors represent different stress values, and specific routes (black lines) were chosen at the same position in three sequences to analyze the effect of welding sequences on the welding stress concretely.
Figure 19.
Comparison of the von Mises stresses according to the black routes (as shown in
Figure 18) in three different sequences (the red histograms represent the maximum stresses, and the black ones represent the average stresses).
Figure 20.
Colored maps of welding distortions in the three different sequence. The values on the left represent displacements, of which the positive values represent the outward distortion at outer shell and inward distortion at inner shell, and the negative values represent outward distortion at inner shell and inward distortion at outer shell. Specific routes (black lines) were chosen at the same position to analyze the effect of welding sequences on the welding stresses concretely.
Figure 21.
Overall distortion trends of the 1/32 VV mock-up in three difference sequences. Red line represents the initial shape before welding, and the green line represents the distorted shape after welding. PS1, PS2, and PS4 distort to inside perpendicular to the shells and PS3 distorts to outside perpendicular to the shells.
Figure 22.
Comparison of the welding distortions according to the black route (as shown in
Figure 20) in the three different sequences (the red histograms represent the maximum distortions, and the black ones represent the average distortions).
Table 1.
Chemical compositions of the austenitic steel 316LN (wt %).
C | Si | Mn | P | S | Cr | Mo | Ni | N | Cu |
---|
0.021 | 0.77 | 1.109 | 0.039 | 0.001 | 16.92 | 2.03 | 12.16 | 0.033 | 0.20 |
Table 2.
Welding parameters of the four layers.
Layers | Current (A) | Voltage (V) | Speed (mm/min) |
---|
Bottom layer | 70 | 10 | 100 |
Second layer | 160 | 12 | 80 |
Third layer | 200 | 12 | 80 |
Cover layer | 170 | 12 | 45 |
Table 3.
The thermal and mechanical properties of the austenitic steel 316LN.
(K)
| (MPa)
| (MPa)
| | (N/m2)
| (1/K) | (kg/m3)
| (W/mk)
| (J/kg K)
|
---|
293 | 525 | 271 | 0.3 | 1.920 × 1011 | 1.59 × 10−5 | 7966 | 13.94 | 470 |
373 | 509 | 220 | 0.3 | 1.860 × 1011 | 1.64 × 10−5 | 7932 | 15.08 | 486 |
473 | 473 | 184 | 0.3 | 1.780 × 1011 | 1.70 × 10−5 | 7889 | 16.52 | 508 |
573 | 456 | 164 | 0.3 | 1.700 × 1011 | 1.75 × 10−5 | 7846 | 17.95 | 529 |
673 | 449 | 148 | 0.3 | 1.610 × 1011 | 1.79 × 10−5 | 7803 | 19.39 | 550 |
773 | 443 | 140 | 0.3 | 1.530 × 1011 | 1.83 × 10−5 | 7760 | 20.82 | 571 |
873 | 391 | 134 | 0.3 | 1.450 × 1011 | 1.87 × 10−5 | 7717 | 22.25 | 592 |
973 | 274 | 131 | 0.3 | 1.370 × 1011 | 1.90 × 10−5 | 7674 | 23.69 | 613 |
1273 | 170 | 116 | 0.3 | 1.168 × 1011 | 1.98 × 10−5 | 7516 | 25.13 | 676 |
1473 | 86 | 62 | 0.3 | 4.000 × 1010 | 2.11 × 10−5 | 7412 | 26.55 | 722 |
1673 | 24 | 19 | 0.3 | 5.000 × 108 | 2.35 × 10−5 | 7297 | 27.99 | 761 |
1873 | 5 | 2 | 0.3 | 1.000 × 107 | 2.60 × 10−5 | 7180 | 29.44 | 810 |
Table 4.
The finalized parameters of the heat source model in the simulation.
Parameters | Bottom Weld Layer | Second Weld Layer | Third Weld Layer | Cover Weld Layer |
---|
Heat source | 3D-double ellipsoidal |
Velocity(mm/s) | 1.667 | 1.333 | 1.333 | 0.75 |
Length (mm) | 6 | 6.4 | 6.9 | 8 |
Width (mm) | 5 | 4.9 | 5.2 | 6 |
Penetration(mm) | 3 | 3.4 | 3.9 | 5 |
Energy (J/mm) | 420 | 1440 | 1836 | 2720 |
Power ratio | 1.2 | 1.2 | 1.2 | 1.2 |
Length ratio | 0.5 | 0.5 | 0.5 | 0.5 |
Efficiency | 0.9 | 0.9 | 0.9 | 0.9 |
Table 5.
Values of the principal stresses in Y direction obtained from simulation and experiment.
Distance from the Centerline of the Weld Zone (mm) | Experimental (MPa) | Simulation (MPa) | Error (%) |
---|
0 | −110.1 | −120.5 | 9.4 |
10 | 4.3 | 4.67 | 8.6 |
25 | 90.82 | 97.7 | 7.6 |
55 | 19.45 | 16.3 | 16.1 |
95 | 7.98 | 7.06 | 11.5 |
145 | 4.6 | 4.9 | 6.5 |
Table 6.
Values of the principal stresses in X direction obtained from simulation and experiment.
Distance from the Centerline of the Weld Zone (mm) | Experimental (MPa) | Simulation (MPa) | Error (%) |
---|
0 | 231.1 | 220 | 4.8 |
10 | 230.5 | 237.4 | 3 |
25 | 130.7 | 136.7 | 4.6 |
55 | −40.3 | −33 | 18.1 |
95 | −30.1 | −32.7 | 5.3 |
145 | −25.0 | −27.4 | 9.6 |
Table 7.
Values of the angular distortion obtained from simulation and experiment.
Distance from the Centerline of Weld (mm) | Experimental (mm) | FEM (mm) | Error (%) |
---|
−150 | −0.07 | −0.0831 | 18.7 |
−95 | −0.63 | −0.608 | 3.5 |
−55 | −0.92 | −1.07 | 16.3 |
−25 | −1.39 | −1.41 | 1.4 |
−10 | −1.50 | −1.54 | 2.7 |
0 | −0.92 | −0.936 | 1.7 |
10 | −1.50 | −1.54 | 2.7 |
25 | −1.38 | −1.41 | 2.2 |
55 | −0.93 | −1.07 | 15.1 |
95 | −0.62 | −0.608 | 2.0 |
150 | −0.07 | −0.831 | 18.7 |