Residual stress is usually defined as the stress which remains in mechanical parts which are not subjected to any
outside stresses. Residual stress exists in practically all rigid parts, whether metallic or not (wood, polymer, glass,
ceramic, etc). It is the result of the metallurgical and mechanical history of each point in the part and the part as a
whole during its manufacture. It exists at different levels, generally divided into three, depending on the scale on
which the stress is observed [1]: