ABSTRACT
Typically, the creep response of a solid is found by measuring the strain rate as a function of applied load. This, most simply, can be done by attaching a load to a sample, heating it, and measuring its deformation as a function of time. The resulting strain is plotted versus time, as shown in Fig. 12.la, where three regions are typically observed: (1) there is an initial, almost instantaneous response, followed by a decreasing rate of increase in strain with time. This region is known as the primary creep region. (2) There is a region where the strain increases linearly with time. This is known as the steady-state or secondary creep stage which, from a practical point of view, is the most important stage and is of major concern here. (3) There is a region known as the tertiary creep stage which occurs just before the specimen fails, where the strain rate increases rapidly with time.
