Machine Design Elements Board Practice Exam

The characteristic that describes permanent deformation without fracture is plasticity. Plasticity refers to the ability of a material to undergo non-elastic deformation when a force is applied, meaning it can change shape and maintain that new shape even after the load is removed. This property is crucial in manufacturing processes where materials need to be shaped or molded.

Malleability, while related, specifically refers to the ability of a material, usually metals, to be deformed under compressive stress, like hammering or rolling, and is commonly associated with thickness changes. Ductility, on the other hand, is a measure of a material's ability to deform under tensile stress, resulting in elongation or stretching before breaking. Elasticity, in contrast, describes a material's ability to return to its original shape after deformation, which does not involve any permanent change to the material's structure.

Understanding plasticity is essential for applications where materials must hold a new shape without fracturing, such as in the shaping of metals during fabrication.