What type of deformation occurs when yielding takes place?

When yielding occurs, the material undergoes plastic deformation. This type of deformation is characterized by a permanent change in shape or size when the applied stress exceeds a certain threshold, known as the yield strength of the material. Unlike elastic deformation, where materials return to their original shape upon the removal of the load, plastic deformation leads to a new, permanent configuration.

In the context of engineering and materials science, understanding plastic deformation is crucial because it indicates how materials behave under load beyond their elastic limit. It provides insights into how structures will perform under stress, whether they will permanently deform or return to their original state. Since yielding marks the transition from elastic behavior to plastic behavior, it is a key concept in the analysis and design of materials in construction and manufacturing.

The other types of deformation mentioned, such as creep deformation, occur over time under constant stress, and viscoelastic deformation involves both viscous and elastic characteristics, which are not typically associated with yielding in the same way as plastic deformation. Therefore, considering the definitions and behaviors of materials under stress, the choice of plastic deformation is accurate when discussing yielding.