Which term refers to the stress at which an observable, significant change in strain occurs without an increase in applied stress?

The term that refers to the stress at which an observable, significant change in strain occurs without an increase in applied stress is the yield point. The yield point indicates the transition from elastic behavior, where materials return to their original shape upon load removal, to plastic behavior, where permanent deformation begins to occur. At this stage, even if the applied stress remains constant, the material undergoes a noticeable increase in strain.

This point is critical in material science and engineering, as it helps define the limits of safe loading conditions for structures and components. Understanding the yield point allows engineers to design structures that can withstand anticipated loads without undergoing irreversible deformation. In contrast, terms like tensile limit and ultimate point refer to different characteristics of material strength, focusing on failure and maximum strain capabilities, while plastic limit pertains to the transition from elastic to plastic deformation but does not specifically define the point of significant change in strain without increasing stress.