Final answer:
Subjected to a force couple that causes twisting, an object experiences torsion, a type of deformation distinct from compression, tension, and shear.
Step-by-step explanation:
When an object is subjected to a force couple that causes it to twist until permanent deformation occurs, the object experiences torsion. Torsion refers to the twisting action that results when torques are applied in a way that causes rotation without the necessity of a direct force. This is different from compression, which is a reduction of volume due to a compressive stress, tension, which is an elongation due to tensile stress, and shear, which occurs when forces are applied tangentially to the surface of an object, causing layers to slide past one another. Torsion is analogous to other types of deformations like tension, shear, and bulk deformation in how it affects the structure of materials. This results in a twist through the length of the object, leading to angled deformation relative to its original shape.