Material Failure : Case Study of Titanic

There are two main causes of Titanic sinking:

Brittle fracture
Weak rivet

Facts of the failure in the Titanic steel:

From the sample steel that be taken from the hull of the ship, metallurgical analysis was done. There were found that the steel contain the phosphorus which is slightly higher than normal, while the sulphur content is quite high, accompanied by a low manganese content. The presence of relatively high amounts of phosphorous, oxygen, and sulphur is tends to make the steel more brittle at low temperatures.
Brittle fracture is a rapid of cracks through a stressed material. The crack is usually travel so fast and almost no plastic deformation before failure occur.
To determine the steel’s mechanical property, Charpy impact test were used to measure the brittleness of a material in the hull of the Titanic. Below are the Charpy impact test comparison between modern steel and Titanic steel in the hull plate.

With a large force, the sample of modern steel bent without breaking into pieces; it was ductile. Under the same impact loading, the Titanic steel, on the right, was extremely brittle; it broke in two pieces with little deformation. The comparison of modern steel and Titanic steel is shown by the graph below:


Brittle fracture is a failure of a metal by crack propagation and with the absence of ductility

When the titanic samples were examined with a scanning electron microscope, the grain structure of the steel was found to be very large, this coarse structure made it easier for cracks to propagate.

Weak Rivets factor.
On impact, the rivets were either sheared off or the heads popped off because of excessive loading, which opened up riveted seams. Also, the rivets around the perimeter of the plates elongated due to the stresses applied by the water, which broke the caulking and provided another inlet for the water. When the iceberg hit along sections of the Titanic's hull, the rivets were sheared off,...