1 / 32

100 th . Anniversary of the TITANIC DISASTER

100 th . Anniversary of the TITANIC DISASTER. 14 th . April 1912. Unsinkable: 16 watertight compartments. Sank in less than three hours. Lifeboat space had been provided for only about half of the passengers and crew

yagil
Télécharger la présentation

100 th . Anniversary of the TITANIC DISASTER

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 100th. Anniversary of the TITANIC DISASTER 14th. April 1912

  2. Unsinkable: 16 watertight compartments.

  3. Sank in less than three hours. Lifeboat space had been provided for only about half of the passengers and crew Californian, close to the scene, had not come to the rescue because its radio operator was off duty and asleep. Reforms: lifeboat space for every person on a ship lifeboat drills full-time radio watch while at sea an international ice patrol.

  4. Why did the Titanic sink so easily?

  5. Robert D. Ballard Professor of OceanographyDirector, Institute for Archaeological Oceanography University of Rhode Island Discovered the wreck of the Titanic in 1985 "All kids dream a marvelous image of what they want to do. But then society tells them they can't do it. I didn't listen. I wanted to live my dream."

  6. Liberty Ships : the first all-welded pre-fabricated cargo ships Mass produced in the United States. 2,751 Liberty Ships were built between 1941 and 1945 Only two now remain afloat Many of the remainder were destroyed by cracking of the type shown.

  7. What was the cause of the failure of the Liberty ships?

  8. ? Silent puncture Two ways for the tire/tube to fail Noisy burst

  9. Surprise !!! A balloon bursts when all we are trying to do is to make a small hole ???

  10. A.A. Griffith (1893-1963) Phenomena of rupture and flow in solids, Philosophical Transactions of the Royal Society of London, A221, 163-198 (1921)

  11. Experiment on paper tearing Compressive stress Tensile stress Cracks propagate when there is tensile stress perpendicular to the crack surface. They do not propagate when there is compressive stress perpendicular to the surface.

  12. A critical tensile stress is required to propagate the crack. What is the driving force for crack propagation? Reduction in strain energy But what prevents the propagation of crack even in the presence of a tensile stress less than a critical value? Surface energy

  13. ΔE c c* Griffith’s relation continued: c*= critical crack size Crack is stable Crack will grow

  14. c Unsafe Unstable cracks Safe Stable cracks

  15. 2c Griffith’s equation Competition between strain energy and surface energy • f= fracture stress • E = Young’s modulus • = surface energy c = crack size

  16. Griffith’s equation c = half crack size for internal crack c = full crack size for surface crack 2c c Surface crack of depth c as effective as an internal crack of length 2c

  17. For c = 1 m ;  =1 Å; max=201 app =crack tip radius Distance from the crack tip

  18. Two types of fracture: Ductile fracture Brittle fracture Q: Which of the two absorb more energy? stress stress Brittle ductile strain

  19. Charpy Impact Test ductile brittle

  20. Ductile-to-brittle transition y (bcc) f f y (fcc) y < f y > f brittle ductile T TDBTT T

  21. Ductile-to-brittle transition • FCC materials do not show DBT • Good for cryogenic applications • Stainless steel (austenite: fcc)containers • for Liq O2 rocket fuel • mild steel not good (: bcc) • Fine grain size give lower transition temperature • High strain rate increase the transition temperature • 4. Notches increase the transition temperature

  22. Protection against fracture Reduction in cross-section: glass fiber Introduce compressive stresses in the surface Tempering of glass Ion- exchange of glass Carburization of steel (chapter 8) Fine-grains in ceramic: glass-ceramics discussed in chapter 9 Reduction of sulphur in steel

  23. First Passanger jet aircraft

  24. COMET 2 May 1952 A new era in civil aviation BOAC- the envy of world airlines Smooth and Silent Travel time reduced by half Pressurised cabins

  25. Comet Tragedy 2nd May 1952 First flight 2nd May 1953 First crash near Kolkata 10th Jan 1954 Second crash near Elba Islands 8th April 1954 Third crash between Rome to Cairo WITHDRAWN FROM SERVICE

  26. The 11 January 1954 edition of The New York Times reported: Thirty-five persons were almost certainly killed when a British Comet jet airliner crashed into the sea this morning about halfway between the islands of Elba and Montecristo, off the Italian western coast. Fifteen bodies had been recovered at a late hour tonight and there was slight hope that there were any survivors among the 29 passengers and six crewmen on the British Overseas Airways Corporation plane.

  27. ? What were the causes of these failures ? ? ?

  28. Cyclic Loading Fatigue

  29. Can a metal get tired? Ans: Yes, Indeed they do!! y Fracture max Subcritical crack growth

  30. Fatigue testing of comet aircraft

More Related