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Constance Tipper and Brittle Fracture

 
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Dr. N. Subramanian
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PostPosted: Tue Oct 18, 2011 6:17 pm    Post subject: Constance Tipper and Brittle Fracture Reply with quote

Constance  Tipper
Constance Fligg Elam Tipper (6 February 1894 – 14 December 1995) was a British metallurgist and crystallographer.

Constance Tipper was one of the first women to take the Natural Sciences Tripos, in 1915. Her major research contribution was to discover why during the Second World War the Liberty Ships were breaking in two.

Working from the Engineering Department in Cambridge, Tipper established that there is a critical temperature below which the fracture in steel changes from ductile to brittle. Constance Tipper specialized in the investigation of metal strength and its effect on engineering problems. During the Second World War, she investigated the causes of brittle fracture in Liberty Ships. These ships were built and mass produced in the United States between 1941 and 1945, and were the first all-welded pre-fabricated cargo ships. About 2,751 Liberty Ships were built between 1941 and 1945. Only two now remain afloat.

Professor John Baker, who was Head of Engineering at that time was asked to launch an investigation into the reasons why these ships were breaking up so he brought Constance Tipper in as the technical expert.

A fractured Liberty Ship
Tipper established that the fractures were not caused by the welding but were caused by the steel itself. She demonstrated that there is a critical temperature below which the fracture mode in steel changes from ductile to brittle. Because ships in the North Atlantic were subjected to low temperatures, they were susceptible to brittle failure. These fatigue cracks were able to spread across the fused metal of the ship's welded joint plates, instead of stopping at plate edges of a rivetted joint that would have previously been used.

Ships in the North Atlantic were subjected to such low temperatures that they would have been susceptible to brittle failure. She wrote a book called ‘The Brittle Fracture Story’ published in 1962 by CUP.

Liberty Ships

The full implications of her work were not realised until the 1950s but after that, the ‘Tipper test’ became the standard method for determining this form of brittleness in steel.

Early Years
Constance Tipper, (born Constance Fligg Elam) an undergraduate at Newnham, was one of the first women to take the Natural Sciences Tripos, in 1915. On graduating she joined the National Physical Laboratory and then went to the Royal School of Mines.

While employed by the Royal School of Mines, she worked at Cambridge with GI Taylor on the deformation of crystals under strain. She moved to Cambridge in 1929 and became a research fellow at Newnham.

She became involved in the Engineering Department during the Second World War when several of the lecturers were called to service, and she took on a considerable teaching load, in particular taking over the Heat Treatment laboratory.

In 1949 Tipper was appointed Reader and became the only woman to be a full time member of the Faculty of Engineering of Cambridge University.

She was the first person to use a scanning electron microscope (SEM) to examine metallic fracture faces. She used a scanning electron microscope built by Charles Oatley and his team, the second SEM ever built.

She retired in 1960 and her 100th birthday in 1994 was celebrated by Newnham College with the planting of the Tipper Tree, a sweet chestnut. She died in 1995, aged 101.

References
http://www-g.eng.cam.ac.uk/125/1925-1950/tipper.html
http://en.wikipedia.org/wiki/Constance_Tipper
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