Corrosion, Fatigue and Creep

Abstract

Three problems, singly or in combination, may confront the designer as he endeavours to produce components which will function reliably under rigorous conditions. These are: corrosion, fatigue and creep, of which corrosion is the most widespread, tending to occur in almost every kind of engineering structure and machine and frequently doing so with lamentable results. In certain instances corrosion is linked closely with fatigue and creep, but often it occurs alone so that many of its depredations can be and are discussed without reference to the other two phenomena. Fatigue is associated only with fluctuating stress and therefore appears mainly in parts in rapid vibratory, rotational or reciprocatory motion. The avoidance of fatigue failure is, however, dependent to a great extent upon good surface finish, and so the possibility of corrosion must enter into any consideration of components likely to be subjected to fatigue. Creep—the third of these problems, is associated mainly with high temperatures and normally, although it is of great importance, the designer need only consider it in the design of parts such as those in high pressure steam or gas turbine plant. Obviously fatigue and corrosion may have to be considered also in such designs.