Results and discussion
The strain controlled cyclic test results showed that the load carrying
capacity of the cross-weld specimen was comparable to that of the base
metal. Static test results in the literature [20] presented in Table
1, showed that the strength of weld section and heat affected zone were
both slightly higher than the base metal but such behaviour was not
noticed in the cyclic test performed in this study. This can be
explained by the cyclic softening behaviour (Fig. 7) observed within the
first 20 cycles in this study. Strain controlled test leads to
application of plastic strains to the material, i.e. the material is
deformed well beyond the yield strength. Since a stress plateau region
is characteristic of metals due to work hardening, the difference in the
behaviour of the cross-weld specimen and base metal specimen becomes
negligible. Moreover, the application of cyclic loads causes the stress
to relax in consecutive cycles owing to the Bauschinger effect.
Therefore, the experimental results obtained from this study indicate
that the cyclic deformation behaviour of circumferential welds employed
in OWT structures can be predicted using the base metal material
properties.