(45d) On Brittle Fractures That Appeared in New York Times and Material Design
AIChE Annual Meeting
Monday, November 8, 2010 - 8:30am to 11:00am
Undergraduate students learn ductile and brittle fracture mechanisms during their introductory Materials Science course. The DBTT, ductile to brittle transition temperature phenomena can explain some of the disasters that made the evening news. Some examples are;
i) 2003 Columbia Disaster ii) 1986 Challenger Disaster iii) Collapse of the Silver Bridge at Point Pleasant, WV in Dec' 1967 iv) Great Boston Molasses Disaster in 1919 v) Sinking of Titanic in 1912
The 1986 challenger disaster can be attributed to the failure of the O rings made of fluorelastomers. The lower outdoor temperature during the luanch date of Jan-28-2010 compared with the design use temperature of the otherwise material lead to brittle fracture. The DBTT and the closely related Tg the glass transition temperature lies between the launch day weather temperature and design use temperature. The sinking of the ship Titanic in 1912 can be explained due to a change in the lattice solid structure of steel from FCC to BCC. The water temperature got colder than the steel was designed for leading to a brittle fracture. A huge tank 190 feet in diameter, 50 feet high fractured catostropically flooding the streets of Boston with 2 million gallons of molasses in 1919. The court appointed auditor handed down a decision that the disaster was the result of structural failure rather than explosion. The weather temperature rose that day. Was the brittle facture due to DBT phenomena or due to creep phenomena ? Stress corrosion cracking and long exposure to hydrogen sulfide is the attributed cause of failure of the silver bridge in West Virginia in 1967. Carbon-carbon composite failure has been sugested as a cause of the recent Columbia disaster in 2003. The students are motivated to the subject when these disasters are discussed in class. The course asessment reveals this clearly.