Explain what is meant by the "ductile-brittle transition" of steel and how this relates to the cracking problems with the Liberty ships during World War II.

A material can convert from ductile into brittle material by following reasons

1. At low temperature

2. Due to notches present in materials

When temperature is very low then a ductile material starts to behave like brittle material and it leads to failure of the material.

When material consists large number of notches then it losses it ductility and behave like brittle materials.

During the world war second ships are failed because temperature of sea became to low and due to this steel (ductile material) converted into brittle material and failed without giving any warning.