What phenomenon in materials is defined as the tendency to deform under constant stress?

The phenomenon defined as the tendency of materials to deform under constant stress is known as creep. Creep is a time-dependent deformation that occurs when a material is subjected to a sustained load or stress over an extended period of time, especially at elevated temperatures. This behavior is particularly significant in materials that are subjected to high temperatures, such as metals in turbine engines or components in industrial machinery.

Creep can lead to detrimental changes in the dimensions of a material, potentially causing failure or a loss of mechanical integrity. Understanding creep is crucial in material selection and engineering design, as it helps predict how materials will behave under long-term loading conditions. The study of creep is essential in designing components that will maintain their structural integrity and performance over their intended lifespan.

In contrast, yield refers to the point at which a material begins to deform plastically and is usually associated with a specific stress level. Fatigue refers to the weakening of a material caused by cyclic loading, which leads to the development of cracks and eventual failure. Build-up is not a recognized phenomenon in the context of material deformation under stress.