The techniques used for this purpose are summarised in Table 1. Of the properties listed, no single measurement is comprehensive enough to describe the steel with all requisite completeness. However, the present survey is confined to just two topics, damage parameters and hardness changes. It is recognised that the implementation of a life-extension procedure must be based on much wider considerations backed by more frequent inspections. Methods used in the estimation of remaining life.
Failure occurs when the sum achieves a value of unity.
This clearly cannot be the case even for the creep strain. This is because the extent of damage is expected to depend on the path by which a given value of strain is achieved, for example, whether the strain is localised at grain boundaries or uniformly distributed. The network nodes then do not coincide with carbide particles, thus changing the mechanism of deformation. This is not the case with variations in temperature because the dislocation network then scales with the particle spacing. The failure of the life fraction rule is sometimes accommodated by empirically setting the limiting value of C to some positive value which is not unity.