elsewhere, as shown in Fig. 15b. These deviations are primarily due
to both geometrical and materials non-linearity experienced during
the simulation process.
Figs.16 and 17 shows the distributions of axial and hoop residual
stresses (both total and net), along the pipe inner and outer
circumference, respectively. The residual stresses are almost constant
along the pipe circumference confirming the axisymmetric
nature of the problem, except at the weld start-end location [17]. At
the weld start-end location, residual stresses fluctuate and reverse
sign from tension to compression. Fig. 16a shows that under the
weld bead, the total axial stresses are around 1.1 Sy at the weld
start, and then decreases drastically to 0.5 Sy before they increase
again to a peak value of 1.2 Sy within 1/8th of the pipe circumference
measured from the weld start. The corresponding residual
axial stresses follow the same pattern of the total axial stresses, but
with a difference of 0.3 Sy at all angular positions. Both total and
net hoop stresses are tensile at all angles but fluctuate significantly
along the pipe circumference, as shown in Fig. 16b. Residual hoop
stresses fluctuate between a minimum value of 0.4 Sy at the weld
start and a maximum value of approximately 1.1 Sy near the weld
end, whereas they have a semi steady value of 0.8 Sy between the
weld start and end. These fluctuations in hoop stresses can be
attributed to the non-uniform deformations occurring along the
circumference as the welding process proceeds from start to end.
The angular distribution of total and residual hoop stresses at the
weld toe along the pipe outer surface is shown in Fig. 17 where the
total hoop stresses are uniform away from the weld start-end
junction. However, a significant fluctuation between a minimum
value 0.1 Sy and a maximum value 1.05 Sy is observed within the
weld zone. The angular distribution of axial residual stress along
the pipe outer circumference are not included as they are relatively
low, mainly compressive, and do not represent any danger for crack