Tewksbury Lecture: Putting fracture to work

It is emphasized that the science and crafts associated with the parting of solids are of considerable industrial, cultural and historical interest. Some principles of the modern theory of fracture which may be relevant to the controlled separation of a solid into pieces are reviewed. The use of path independent integrals in the analysis of indentation fracture is discussed, and some of the subtleties involved in treating the motion, deviation and forking of cracks and the energy balance in crushing and shattering are considered. The paper concludes with a brief account of some recent work on the theory of flint knapping and of the influence of the environment on the fracture process.