Final answer:
The ability of a metal to resist fracture under a sudden load is called its impact strength, not to be confused with tensile strength which is the stress a material can withstand before permanent deformation or fracture.
Step-by-step explanation:
The ability of a metal to resist fracture under a sudden load is its impact strength. Tensile strength, on the other hand, refers to the breaking stress that will cause permanent deformation or fracture of a material. It's the maximum stress that the material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract. Impact strength is a measure of how well a material can absorb energy during plastic deformation and is often assessed with a sudden application of force, as in a Charpy or Izod test.
Tensile strength is related to the maximum stress that a material can handle before it fails, either by plastic deformation or through breaking. Deformation is proportional to the applied force up to a certain point known as the elastic limit. Beyond this point, the material may undergo plastic deformation, where it will not return to its original shape after the force is removed. When a material is stressed beyond its tensile strength, it will eventually reach a fracture point.