ABSTRACT
There are two main sets of materials properties involved in any problem of mechanical reliability.
Yielding properties. Yielding or plastic deformation can be considered as the boundary between the domain of reversible and permanent deformation. In normal conditions, the material must be used below the yield point, often called by metallurgists the elastic limit.
Fracture properties. If, accidentally, the material goes beyond its yield point, a new boundary becomes important: the ultimate fracture stress (or strain) where the integrity of the structure (or the part) is lost. Then the problem of stress concentration at defects becomes crucial and we need specific theoretical and experimental tools, e.g., fracture mechanics, to study these phenomena.
