Which characteristic is associated with viscoplastic materials?

Viscoplastic materials are defined by their ability to exhibit both time-dependent behavior and plastic deformation under applied stress. This characteristic means that when a viscoplastic material is subjected to stress, its response is influenced not only by the amount of stress applied but also by the duration of that stress. Such materials can flow and deform permanently over time when subjected to constant stress, and they may also exhibit time-dependent recovery or creep behavior.

This differentiates them from purely elastic materials, which only store energy and return to their original shape immediately after the stress is removed. Additionally, viscoplastic materials are capable of undergoing large deformations without breaking, which is not true for materials that cannot deform under stress. Immediate recovery after stress removal is a hallmark of elastic behavior; in viscoplastic materials, recovery may occur, but it is not guaranteed to be immediate and is accompanied by permanent deformation. Thus, the defining characteristic of viscoplastic materials is indeed their combination of time-dependent and plastic behavior.