Failure Analysis-Q5

Describe the process of fracture of metals and differentiate between ductile and brittle fracture

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The process of fracture:

• The specimen elongates, forming a necked region in which cavities form.

• The cavities coalesce in the neck center, forming a crack which propagates toward the specimen surface in a direction perpendicular to the applied stress.

• As the crack approaches the surface, its growth direction shifts to 45º with respect to the tension axis. This redirection allows for the formation of the cup-and-cone configuration and facilitates fracture.

Ductile fracture	Brittle fracture
Plastic deformation	Small/ no plastic deformation
High energy absorption before fracture	Low energy absorption before fracture
Characterized by slow crack propagation	Characterized by rapid crack propagation
Detectable failure	Unexpected failure
Stable crack	Unstable crack
Eg: Metals, polymers	Eg: Ceramics, polymers