Mechanics of Creep Brittle Materials

Failure of components which operate in the creep range can result either from the growth of a dominant crack or through the accumulation of 'damage' in the material. Conventional and nuclear power generating plant are generally designed on the basis of continuum failure, with assessment routes providing an indication of the effects of flaws on component performance. Another example where an understanding of creep failure is important is in the design of offshore structures which operate in arctic waters. These structures can be subjected to quite considerable forces by wind-driven ice sheets, which are limited by failure of the ice sheet. Design codes are currently being developed which identify the different mechanisms of failure, ranging from continuum crushing to radial cracking and buckling of the ice sheet. Our final example concerns engineering ceramics, which are currently being considered for use in a wide range of high-temperature applications. A major problem preventing an early adoption of these materials is their brittle response at high stresses, although they can behave in a ductile manner at lower stresses. In each of the above situations an understanding of the processes of fast fracture, creep crack growth and continuum failure is required, and in particular an understanding of the material and structural features that influence the transition from brittle to ductile behaviour. The translation of this information to component design is most advanced for metallic components.