Modeling Strain Hardening the Hard Way

摘要

Suppose you want to describe the bending of a metal paperclip. Most materials engineers can provide a simple approximate description of the deformation and hardening behavior of the clip. Madec et al. have now gone an important step further. They are systematically investigating the physics behind strain hardening by individually following the fate of all crystal defects involved. On page 1879 of this issue, they report an important contribution to hardening that has hitherto been overlooked. Anyone who has ever tried to straighten a crooked nail or bend a metal paperclip back into a straight wire has experienced strain hardening: The more plastic deformation accumulates in one location of a metallic component, the larger the stress needed to further deform it there (see the figure). Strain hardening is, however, not just a nuisance of everyday life. It is the basis for the formability of metals, which is probably the main reason underlying the prominent role of metals in the development of technology.