Structural Integrity (SI) as a single distinct subject has now come of age. It has grown, sometimes painfully, through the activities of many different engineering and scientific disciplines, numerous professional institutions, separate industrial organizations, several university engineering departments and national and international societies. An accelerated impetus has been derived from severe engineering problems and accidents, some of which are briefly reviewed. In the UK and elsewhere the numerous but separate disciplines initially involved in SI have each made valuable contributions. Engineers and scientists attempted to solve practical problems, but without accurate knowledge of the applied stress levels. They were followed by metallurgists, who focused attention on a materials microstructure. Design engineers and manufacturers were unable to incorporate defects of the order of grain size, or less, into their calculations. All were eventually assisted by two important developments. First came the rapid advances in two-and three-dimensional finite element analyses of stress distributions in complex-shaped geometries, and second, the study of cracks by elastic and then elastic-plastic fracture mechanics. When combined, these computer-assisted developments focused attention on the all-important synergistic parameter sigmaroota. En-route to this improved state of affairs several alternative approaches were investigated to quantify the SI of structures, components and materials, many of these alternatives effectively delaying progress for many years, at great cost. Although the UK has made numerous positive contributions to SI investigations, sometimes due to unfortunate although avoidable accidents, of which many recent incidents are well-documented, future pitfalls and false trails have to be avoided wherever and whenever possible. To achieve this, individual discipline approaches now need to be better integrated at national and international levels. The increasing complexity of engineering components and structures intended to work at higher temperatures, in more aggressive environments, and with greater efficiency, will demand a higher degree of synthesis of effort. Society will demand nothing less Failures due to inappropriate and/or incorrect SI assessments leading to increasing costs to the nation in terms of human, animal and plant life, environmental damage to land sea and air, disruption to societal activities, not to mention the associated Government-sourced budget losses, need to be dramatically reduced. By looking at some industry-university collaborations in SI studies, it is hoped that the issues raised in this lecture will help in plotting the way forward and answering the question: 'Structural Integrity-whose responsibility?'
