Tuesday, April 27, 2010

Materials Engineering and Marine Construction

Many of us had watched the movie Titanic , enjoyed the music and romantic scene. But how many of us do look beyond that. The sinking of Titanic on 15 April 1912 had led to investigation to identify the causes of accident and search remedy to prevent recurrences. Some causes and remedies had been identified through investigation shortly after the incidents. Other causes and remedies were not identified until recent years due to the limitation of Technology.
The excavation of Titanic was only done in 1985 using a sophisticated Sonar Vehicle called SAR(Sonar Acoustique Remorque) and undersea camera system called Argo http://library.thinkquest.org/27423/glossaey.htm
The forensic and Materials investigation of Titanic sinking was only carried by the investigation team of the University of Missouri-Rolla in 1996.
Among the Metallurgical factors that contributed to the fast sinking of Titanic Ship were identified as follows .
1) The individual hull plates were joined together by riveting instead of weld, the arc welding technology was in infantry stage at time of construction of titanic. The joining of hull plate using rivet is not a reliable because it give rises to stress concentration. It was reported that million of joint were employed in the construction of Titanic.
2) The steel used for the construction of hull was of inferior quality having a high sulphur and phosphorous content as evidenced by the microstructure of the steel. The reason is that the steel was made by Bessemer process.
3) The Charpy impart test were done on two type of steel , namely the modern SAE steel , and the steel used for making Titanic .And The result shown that the SAE 1020steel has a brittle transition of sub zero , while the one used for making Titanic has a brittle transition temperature well above room temperature.
4) The tensile strength and yield strength for both types of steel do not differ very much.
5) The steel used for making Titanic exhibits great grain size
The advancement in Technology Decades after the sinking of Titanic
1) Today hull plates are joined together by sophisticated welding techniques such as GTAW process or GMAW process ,and the weld need to be subjected stricter Non destructive Testing

2) The steel used for the construction of hull are of superior quality having a very low sulphur and phosphorous content .This is possible because of advancement in electric arc melting furnace
3) The absence of harmful impurities lead to a lower Brittle transition Temperature,
4) The quality control system employed in steel making and marine construction industry is more reliable than those of yester year



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