ssc-452 aluminum structure design and fabrication guide ship

Aluminum Marine Structure Guide
If the analysis of Collette is correct, then the method proposed by Paik will over-predict
the tensile strength of a welded panel. More detailed analysis validated by experiment is needed
to determine an appropriate methodology. However, these analyses show that the effective yield
strength in tension is greater than that of the HAZ alone.
Collette also examined the ultimate strength considering that the limiting strain for 5083-
H116 HAZ as 12 percent and 8 percent in 6082 HAZ. The results are shown in Figure 2-8, with
the strain concentration in the 6082 HAZ limiting the strain to produce failure of the overall plate
significantly. This analysis may be overly conservative because the constraint imposed by the
base metal may permit higher strains with the HAZ. However, the analysis clearly indicates the
need for further analysis and experimentation to determine the tensile strength of welded
structures.
Figure 2-8 Strain in heat-affected zone of welds in a panel (Collette, 2005)
2.4 Corrosion
Compared to steel, aluminum has very good resistance to corrosion, and many vessels
that are unpainted have operated for 30 years or more in seawater. Nevertheless, there are
conditions in which corrosion can occur, and these conditions can sometimes lead to rapid
deterioration of the structure. In general, there are seven types of corrosion that can occur
(Czyryca and Vassilaros, 1972):
1. General corrosion and pitting
2. Exfoliation
3. Intergranular corrosion
4. Stress-corrosion cracking
5. Corrosion-erosion, impingement, and cavitation
6. Galvanic corrosion
7. Crevice corrosion
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