ssc-367 - Ship Structure Committee

A second pass with polishingdisc is considered advisable. A
complete chapter on weld toe grinding by Woodley (Reference
9.9) provides a detailed discussion on grinding techniques.
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Using a high-pressure abrasive water jet (AWJ) process for
controllederosion of the weld toe area can be as effectiveas
grinding. Its simplicity, speed and non-utilization of heat
make controlled erosion very promising. Work carried out by
King (Reference9.5) indicatethat AWJ process is suitable for
a range of material removal applications, includingweld toe
dressing, gouging and weld edge preparation.
●
A wider weld pool makes plasma dressing less sensitive to the
positioning of the electrode relative to the weld toe,
compared with TIG dressing. Therefore, the fatigue strength
improvementobtained from plasma dressing is generally better
than that obtained from TIG dressing.
Both methods are suitable for automation and cost-effective
application.
●
Review of grinding, remeltingand peening techniques indicate
substantial scatter of fatigue strength improvements.
Typically the best fatigue strength improvementsare achieved
byTIG dressing and hannnerpeening. Toe disc grinding is the
least effective technique. Figure 9-4, obtained from
Reference 9.7, provides a good comparison of various fatigue
strength improvementtechniques.
9.4 FATIGUE ANALYSIS STRATEGIES
9.4.1 Review of Uncertainties.Gaps and Research Needs
There are many uncertainties in a fatigue analysis, carried out to
determine the fatigue lives of marine structure components. To
ensure validity of analysis the first objective is to accurately
predict the stress-historyfor the lifetime of the structure. The
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