Final answer:
An impact test specimen is required to determine a material's ability to resist failure by brittle fracture. It measures a material's resistance to fracture under sudden force, providing insights into its toughness and behavior under stress.
Step-by-step explanation:
The mechanical test used to determine the ability of a material to resist failure by brittle fracture requires the use of an impact test specimen. The purpose of the impact test is to measure a material's resistance to fracture when a sudden force or impact is applied. Characteristics such as tensile strength, the breaking stress that can lead to permanent deformation or fracture of a material, as well as the behavior of a material when it undergoes plastic deformation, are crucial to understanding how the material will behave under stress. In an impact test, the material is subjected to a fast and forceful strike to study its fracture characteristics. This will highlight a material's toughness or brittleness and is particularly important in assessing materials that might be exposed to harsh or sudden impacts in their intended applications.