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Table 6.2 - Welding trials carried out with the adjusted set-up welding voltage
Input Parameters Measured Response
Run WFS SO V V1 Vm, Imp TSI TI DCI PR
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C21 4 12 16.3 18 16.84 122.9 1.94 0.35 0.75 0.19
C22 6 12 17.6 19.4 17.7 172.6 1.68 0.37 0.7 0.24
C23 8 12 19.2 21.1 19 215.7 1.71 0.36 0.65 0.28
C24 10 12 20.7 22.8 20.42 246.3 1.67 0.31 0.61 0.34
C25 12 12 22.3 24.5 21.77 270.7 1.72 0.31 0.54 0.38
C27 4 15 17.5 19.3 18.15 121.26 2.2 0.34 0.68 0.25
C28 6 15 18.2 20.1 18.49 164.93 1.79 0.35 0.69 0.24
C29 8 15 20.3 22.3 20.31 203.34 1.71 0.34 0.61 0.32
C30 10 15 21.8 23.9 21.63 231.31 1.77 0.27 0.54 0.39
C31 12 15 23.3 25.6 23.06 258.39 1.63 0.24 0.49 0.45
C34 4 20 19.6 21.6 20.52 113.75 2.91 0.25 0.25 0.63
C35 6 20 21 23.1 21.56 155.28 2.31 0.26 0.5 0.41
C36 8 20 27.4 29.9 27.98 199.13 1.05 0.05 0.01 0.97
C37 10 20 28.4 31 28.71 236.43 1.04 0.04 0.01 0.98
C38 12 20 29.3 32 29.46 261.14 1.04 0.05 0.01 0.98
V, q: voltage predicted from the welding parameter generator [volts]
V,, : corrected set-up voltage required for the BDH550 to produce V,,, q [volts]
Note that the actual welding current produced by the BDH320 is generally
lower than the corresponding predicted value, while the currents produced by the
BDH550 are very close to the same predicted values (see Figure 6.2). Since the
generation of welding parameters using the algorithm shown in section 3.3.2.1 is
based on the prediction of current and voltage levels which are expected to give a
stable process when the BDH320 is used, it is clear that new models would be
necessary to correctly map the adequate voltage and current combinations in the case
of the BDH550. This led the present author to develop new models to describe the
performance characteristics of the BDH550. Appendix I shows the bead-on-plate
welding trials data used to develop the BDH550 models. The model structures
developed by Ogunbiyi [ref. 51 ] (see section 3.3.2.1) fitted the available data well and
were adopted. The new model coefficients are shown in Table 6.3.
Considering that differences in the welding parameters would affect the
predicted bead geometry, a calibration of the bead geometry models proposed by
Ogunbiyi [ref 51] was necessary. Such calibration was carried out by measuring the
geometry of the weld beads produced with the welding parameters shown in Table 6.1
and Table 6.2, and by correlating the measured values with the geometry predicted by
the models shown in equations 3.6 and 3.7. Only the weld beads produced from stable
processes were considered for calibration purposes. The measurement of the bead
geometry was performed by cutting a bead specimen from the middle of each welded
joint, polishing one of the transversal cuts, etching with a Nital' 2% solution and
tracing the joint profile from an enlarged projected image.
1 2% Nitric Acid + 95% Methanol + 3% pure water, in volume.
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