ABSTRACT
Chapter 1 describes the main concepts and terms of creep and stress relaxation. It also describes the basic models used for determining the creep of materials at constant and alternating stresses. In the majority of cases, when the levels of temperatures and stresses in the experiments are relatively high, the deformation process with time ends with fracture of the specimen. This moment is characterised by some time t * which is determined by the given values of stress σ and temperature T. If a sufficiently large series of the experiments is carried out, then we can construct a series of the t *(σ) curves for a number of values of temperature T which are referred to as the long-term strength curves. It should be noted that the actual experimental data for the majority of metals and alloys are greatly scattered. For example, for the same stresses and temperature the time to fracture t * in different tests can differ by a factor of 2–3. Because of the considerable material and time losses (the actual experiment may last 15–20 years), the problem of evaluating the long-term strength is very important.
