generates relatively lower residual hoop stresses except at 180
where the hoop stress reaches a peak value of about 0.9 Sy. In
general, axial residual stresses at the pipe outer surface are very low
and do not represent any danger for crack growth. Hence these are
not considered in details here.
Along the pipe inner surface, Back-step scheme gives the lowest
average axial and hoop residual stresses (see Fig. 26a and b).
Welding Scheme # 2 gives the maximum average axial residual
stresses. Welding Scheme # 1 generates steady residual hoop
stresses along the pipe circumference except at the welding starting
point, where the residual axial stresses reach their peak value of
around 0.35 Sy. Welding Schemes # 1 and 3 generate the highest
hoop residual stresses, in particular at the welding start points
(single point at 0 for Scheme # 1 and two points at 0 and 180)
where the hoop stress reaches a peak value around 0.8 Sy.Welding
Scheme # 4 (Back-step) generates the lowest average residual hoop
stresses along the pipe circumference except at welding start point