Transcript Liberty Ships[1].ppt

Brittle Failure of the Liberty Ships
4A6(1) - Structures
Amy O’Connell
Benjamin Toomey
Niall Minihan
Rónán Dillon Murphy
Contents:
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History
The Design Failure
Preventing Brittle Failure
Conclusions
Questions
History
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Built During WW2 by US
2700 produced (1942-1945)
1st All Welded Construction
significant failure by catastrophic fracture
– 30% of early ships
– Failure occurred mostly during winter months
– Both at sea and in port
The Design Failure
Three
basic factors
contribute
to a
Normally
ductile
steels
brittle-cleavage
typebrittle
of fracture
can become
under
• a triaxial
state of stress
certain
conditions.
• a low temperature
• a high strain rate or rapid rate of
loading
• Effect of stress concentrations
due to notched and cracks
Temperature Effects
Preventing Brittle Failure
• Hull plate and weld metal impact
toughness control
• Eliminate sharp changes in cross section
• Material used : adequate toughness for
anticipated loading and low temperature
Conclusions
• New understanding of this brittle
phenomenon
• New test techniques were found
• Previsions were put in place to prevent
failure again
Any
Thank
Questions?
You
4A6(1) - Structures
Amy O’Connell
Benjamin Toomey
Niall Minihann
Rónán Dillon Murphy