NOMENCLATURE
CHAPTER 5 Results and discussions
A. Numerical thermo-mechanical analysis
5.3 Prediction of thermal history and angular deformation of double sided fillet joint
The resulting distortions matched fairly well with those of the numerically predicted ones. This was achieved by considering the restraining effect of the top and bottom reinforcements. The effect was modeled through the use of element birth technique as described in previous section.
As was expected the extent of distortion decreased with increase in plate thickness for a given set of input of welding parameters.
Figure 5.18 Schematic diagram of the fillet weld joint
To weld the double sided fillet weld, welding was performed in two successive passes therefore the transient thermal history was plotted for both the sides. Figures 5.19 and 5.20 shows the transient thermal history for first pass and second pass respectively. Temperature distribution from the center of the weld to away from the weld line was plotted. Second welding was performed after 3 min cooling of the first welding, therefore there is a pre heating effect on the second pass which can be seen from the Figure 5.21. The preheat temperature on the second weld shoot up nearly 420 °C from the first weld. Both heating and cooling of the welds can be observed from the time scale. Due to preheating effect the peak temperature of the second pass (2100 °C ) is more than the first pass (1736 °C ).
0 60 120 180 240 300 360 420
0 200 400 600 800 1000 1200 1400 1600 1800
2000 Along fillet weld line
5mm away 10mm away 15mm awa 20mm away 25 mm away 30 mm away
Temperature (°C)
Time (s) Temperature measured along this line Weld zone
Figure 5.19 Temperature distribution for the first side of double sided fillet welding
0 60 120 180 240 300 360 420 0
300 600 900 1200 1500 1800 2100
2400 Along fillet weld line
5mm away 10mm away 15mm away 20mm away 25 mm away 30 mm away
Temperature (0 C)
Time (s) Temperature measured along this line Weld zone
Figure 5.20 Temperature distribution for the second side of double sided fillet welding
Angular deformation was predicted for different welding conditions of double sided fillet welds. The welding parameters are shown in Table 5.6. In the finite element modelling the numerical angular distortions were plotted based on the nodal deflections from the non-linear elasto-plastic analysis at the edges of the plate. Figure 5.21 shows the finite element angular distortion comparison (nodal deflections) at the edges of the joint models for the welding parameters as given in Table 5.6.
Table 5.6 Numerical welding parameters for double sided fillet welding
Sl. no. Thickness (mm)
Current (A)
Voltage (V)
Welding speed (mm/s)
1 10 425 25 5.0
2 10 460 27 5.0
0 100 200 300 400 450 0.2
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Distortion (mm)
Distance along Y-axis (mm) 10 mm thick plate with inputs of 425A, 25V and 5mm/s welding speed
10 mm thick plate with inputs of 460A, 27V and 5mm/s welding speed
Figure 5.21 Comparison of angular distortion near the end of welded plate and parallel to the weld line (Table 5.6)
5.3.1 Verification of experimental and numerical thermal profile
Figure 5.22 shows the experimental and numerical thermal profiles of 10 mm thick plate for double sided fillet welding. The experimental points (thermocouple position) for the thermal history were located 15 mm away from the (for the first side fillet weld) weld line 2-4 (Figure 5.18) on the top surface of the horizontal plate at a distance of 200 mm from the edge 9-10-11- 12-13-14 (Figure 5.18). Figure 5.22 shows the comparison of experimental and numerical thermal profile for the input welding parameters as given in Table 5.7. It can be observed form Figure 5.22 that there is a close agreement between the experimental and numerical thermal profile.
Table 5.7 Experimental welding parameters for double sided fillet welding
Thickness (mm)
Current (A)
Voltage (V)
Welding speed (mm/s)
10 470 27 5.0
0 100 200 300 400 500 0
100 200 300 400 500 600 700 800
Temperature (°C)
Time (s)
Experimental thermal profile Numerical thermal profile
Figure 5.22 Comparison of numerical and experimental thermal profile (Table 5.7)
5.3.2 Verification of experimental and numerical distortion
The methodology developed in the present investigations based on moving distributed SAW heat flux was adequate enough for predicting the temperature distributions and angular distortions. The input experimental parameter of SAW process for two jobs are given in Table 5.8. Figure 5.23 shows the control points of the double sided fillet welding for measurement of distortion.
Figure 5.23 Plate dimensions and control points for measurement of distortion
Table 5.8 Experimental welding parameters for double sided fillet welding
Sl. no. Thickness (mm)
Current (A)
Voltage (V)
Welding speed (mm/s)
1 10 425 25 5.64
2 10 470 27 5.0
Figure 24 shows the experimental and numerical welding distortions patterns for 10 mm thick plate for job 1 as indicated in Table 5.8. Figure 5.25 shows the experimental and numerical welding distortions pattern for 10 mm thick plate of job 2 as indicated in Table 5.8. From Figures 5.24 & 5.25 it can be observed that there is close agreement between the experimental and numerical distortion shape profiles.
0 75 150 225 300 375 450
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Y-axis (welding direction)
Distortion (mm)
Distance along Y-axis (mm)
Experimetal distortion for 10 mm thick plate with inputs of 425A, 25V and 5.64mm/s welding speed
Numerical distortion for 10 mm thick plate with inputs of 425A, 25V and 5.64mm/s welding speed
X-axis
Points for measuring distortion
Figure 5.24 Experimental and numerical comparison of angular distortion for welding parameters of job 1 as given in Table 5.8
0 75 150 225 300 375 450 0.25
0.50 0.75 1.00 1.25 1.50
Points for measuring distortion Experimetal distortion for 10 mm thick plate with inputs of 470A, 27V and 5 mm/s welding speed
Numerical distortion for 10 mm thick plate with inputs of 470A, 27V and 5 mm/s welding speed
Distortion (mm)
Distance along Y-axis (mm) Y-axis (welding direction)
X-axis
Figure 5.25 Experimental and numerical comparison of angular distortion for welding parameters of job 2 as given in Table 5.8
5.3.3 Summary
From the above investigation of double sided fillet SAW process, it can be summarized as below:
Temperature distribution for 3-D finite element model for double sided fillet SAW process was developed and compared with the experimental results. It was found from thermo-mechanical modelling that as in the case of experiments the distortion patterns in case of 10 mm plate varied for varying input parameters.
The temperature distributions obtained through analysis and those obtained from experimental measurements compared fairly well with a variation of 8% only in case of peak temperatures.
The angular distortions obtained through the finite element analyses and those obtained from experimental measurements compared fairly well with a variation of 5 to 10%
only, for maximum value of distortions.
5.4 Comparative study of residual stress and angular deformation of single and double