What is defined as the continuous slow deformation in materials under persistent stress?

Creep is defined as the continuous slow deformation of materials when they are subjected to persistent stress over time. This phenomenon typically occurs at high temperatures or under conditions of significant stress, where materials gradually elongate or deform, even if the applied stress is below the yield strength.

Understanding creep is vital in engineering applications, especially when designing components that operate under constant loads or high temperatures, such as turbines or structural materials in buildings. Creep can lead to failure if not accounted for, particularly in materials that are expected to maintain their dimensions and integrity under load.

The other concepts mentioned relate to different material behaviors. Ductility refers to a material's ability to deform plastically before breaking, which is not directly related to the slow, time-dependent deformation seen in creep. Brittleness characterizes materials that fracture with little to no plastic deformation, and fatigue refers to the progressive and localized structural damage that occurs when a material continues to be subjected to cyclic loading. Each of these terms highlights a distinct aspect of material behavior under stress, reinforcing why creep is specifically defined by its slow, continuous deformation under constant stress.