What characterizes a 'bend' in structural components?

A 'bend' in structural components is characterized by a smooth and continuous change in shape that can be straightened. This definition highlights that, unlike permanent deformations, a bend indicates that the material has not undergone a complete loss of its elastic properties. Essentially, bends can result from the application of a load that causes the material to deviate slightly from its original straight form but retains the ability to return to that shape once the load is removed.

This contrasts with other options where sharp, uneven changes or cracks indicate more severe structural issues. For instance, a sharp and uneven change in shape suggests a more abrupt transition that may not maintain structural integrity, while a permanent deformation implies a change that cannot be reverted, indicating potential failure of the material. Similarly, a crack denotes a critical flaw or break in the structure, representing a much more serious concern than a simple bend. Therefore, the defining characteristic of a bend is its recoverability and the smooth nature of the change in shape, aligning with option B.