ssc-367 - Ship Structure Committee

and in-plane/out-of-planeangles,and stub-to-chorddiameter ratios
(for tubular members).
The arrangement of structural details is very important from a
standpoint of their configuration (affecting SCFS) and access
(affectingqualityof work). Shiphullstiffenersare often arranged
with these considerationsinmind. Similarly,tubular interfacesof
less than 30 degrees are not desirable in order to ensure reasonable
access for assembly and inspection.
Material Selection
Steel material is selected not only for strength but also for its
other characteristics,includingweldabilityand durability. Thus,
the material selected should have both the chemical composition and
the mechanical properties to optimize its performance. The use of
higher strength steel requires specification of higher material
toughness requirements to meet the limits on fabrication flaws.
Since the material with higher toughness can tolerate larger loads
for a given flaw without brittle fracture during its service life,
such a material is preferred.
Impuritiesinsteel (includingCarbon,Nitrogen,Phosphorus,Sulphur
and Silicon) can cause temper embrittlement, thereby decreasing
notch toughness during the cooling of quenched and tempered steel.
Desirable notch toughness (Charpy) and Crack Tip Opening
Displacement (CTOD) test results are not always achieved at the
fabrication yard. Inspection of the welded joint root, weld
material and the heat-affected zone (HAZ) may show degradation of
root toughness, sometimesextending into the parent material beyond
the HAZ.
Studies carried out by Soyak et al (Reference 3.1) to assess
fracture behavior in alowtoughness HAZ indicatedthat a small lowtoughness
area in the HAZcan be masked by the higher-toughnessarea
surrounding it. Thus, Soyak et al recommend requiring testing of
3-3
..— .——.