Griffith Medal & Prize
The Griffith Medal, an IOM3 Premier Award, is presented for distinguished work that has made or is making a notable contribution to any branch of materials science.
The winner will receive a medal and £300.00
2021 Prof Maria-Magdalena Titirici ProfGradIMMM, 2020 M Chhowalla, 2019 D Jones, 2018 R Cameron, 2017 Nicola M Pugno, 2016 Y W Mai, 2015 I Parkin, 2014 N Fleck, 2013 Dr Robert Broomfield, 2012 M Stevens, 2011 D Hayhurst, 2010 Prof R W Grimes, 2009 Prof A L Greer, 2008 N Alford, 2008 Prof A R West, 2007 Prof Robert O Ritchie, 2006 Peter S Bate, 2005 D J Bacon, 2004 Prof T W Clyne, 2003 Roger W Whatmore, 2002 Prof R J Young, 2001 J Humphreys, 2000 Prof R C Pond, 1999 Prof J F Knott, 1998 Dr J W Johnson, 1997 Prof G C Wood, 1996 A J Kinloch, 1995 Prof G W Greenwood, 1994 Prof A G Evans, 1993 Prof C Gurney, 1992 D V Wilson, 1991 W Bonfield, 1990 P L Pratt, 1989 K H Jack, 1988 M J Bevis, 1987 E D Hondros, 1986 N Phillips, 1985 D Hull, 1984 W C Wake
Griffith was the father of fracture mechanics, the originator of the multi-stage axial aero engine, the bypass engine, the use of jet-lift for vertical take-off and landing, and much else. Owing to the secret nature of his wartime work at Rolls-Royce, and later commercial confidentiality, his innovations in aeronautics are not widely known internationally. It also took others (notably Irwin) to apply Griffith's theory of fracture after the Second World War to the explanation of engineering failures and to establish the principles of design against fracture. But Griffith's 1920 and 1924 papers on fracture laid the foundations of fracture mechanics and that is what we are about to celebrate.
Griffith was a Tate scholar in Mechanical Engineering Liverpool University from 1911-1014 and, following a year of research in the department, he joined the Royal Aircraft Factory at Farnborough in 1915. Stress analysis of aerofoil sections of airscrew blading and other problems led to work with G I Taylor at Farnborough in 1917 on the use of soap films in solving the elastic torsion of hollow bars of irregular cross-section. It was for this work that they won the Thomas Hawksley Gold Medal of the Institution of Mechanical Engineers
In 1920, Griffith produced his seminal paper entitled 'Theory of rupture in which he laid the foundations of what is now known as fracture mechanics. Griffith's great contribution to ideas about strength of materials was that he realised that the weakening of a material by a crack could be treated as an equilibrium problem in which the reduction in potential energy of a body containing a crack, when the crack extends, could be equated to the increase in surface energy due to the increase in surface area. Griffith mechanics is the Castigliano energy method extended to bodies containing propagating cracks. Griffith worked on glass for experimental convenience, but his analysis (what we would call linear elastic fracture mechanics (LEFM today) holds true whenever the irreversible work of fracture is constrained into thin boundary layers contiguous with the crack faces. Globally elastic behaviours of this sort (brittle fracture) can occur, perhaps surprisingly, in large components and structures made of materials which behave in a ductile fashion in laboratory-sized testpieces. It comes about because there is a side effect inherent in the physics of fracture and hence in the Griffith theory: the energy available for fracture scales with the volume, but the energy required scales with crack area. This is why Liberty ships in the Second War and other large steel structures showed brittle behaviour at low fracture stresses, even though laboratory-sized tensile testpieces taken from adjacent to the fractures displayed plastic flow with large reductions in area to fracture. These failures are often explained in terms of reduced Charpy energies (which will make fracture more likely) but even at constant toughness. Griffith's mechanics predict the scale effect. Despite the present common currency of the alternative crack tip singularity approach (stress intensity factors) for the solution of LEFM problems, Griffith-like energy-based mechanics is the common line of attack running through modern solutions of elastic, elastoplastic and plastic fracture problems (cf the work version of the J-integral and so no).
Griffith's working on glass caused, in a sense, his loss to applied mechanicis, for the authorities at Farnborough transferred him to the engine work after the glass-blower's torch set fire to his laboratory. His work on airscrews led Griffith to the study of the gas turbine and to one of his greatest contributions to the science of aircraft propulsion, namely that blades of existing turbines were working in a stalled condition and hence his pioneering suggestion that they ought to be designed as aerofoils in cascade. Linked to this was his staunch advocacy of multi-stage axial design. Griffith may be said to be the true originator of the multi-stage axial engine, and the contraflow turbo-compressor. At Farnborough, he also made important contributions to the piston engine, including the speed/density system of fuel metering (RAE carburetter).
In 1939, Griffith was invited to join Rolls-Royce and his early work there led to the Avon engine which displayed high performance combined with low weight and small diameter. At the same time, he conceived the idea of engine installation at the rear of the fuselage instead of at the wings. Several of his wartime contraflow engines incorporated bypass flow, and in 1946 he started to apply bypass to preliminary designs of the simple jet engine and this gave rise to the Rolls-Royce Conway engines. The cube-square scaling principles latent in his fracture mechanics reappeared in his work on vertical take-off and landing. He argued that minimum weight could be attained by using several small engines in place of one or two high thrust, since an engine's weight decreases as the cube of its linear dimensions whereas the thrust decreases only as the square. This gave rise to the 'Flying Bedstead' the RB10 engine and the Short SC1 VTOL aircraft.
Owing to the international situation prevailing during much of Griffith's creative and original thinking in connection with aeroengine research, aircraft design and so on, his papers were restrictively communicated mainly within Rolls-Royce and the Aeronautical Research Council in the UK. He is therefore not as well known as he should be.
Materials World March 1993, p.177