Fracture

Separation of a solid into more than 1 parts under load or stress.

Based on the type of load:

• Tensile fracture
• Compressive fracture
• Shear fracture
• Fatigue fracture
• Creep fracture

Characterized into 2:

• Ductile fracture
• Brittle fracture

Ductile fracture

Materials show significant amount of plastic deformation prior to fracture. Fracture surface gives cup & cone appearance. Aka. cup-and-cone fracture.

Steps:

1. Specimen forms a neck
2. Cavities start to form within the neck
3. Cavities join with each other and form a crack
4. Crack propagates towards surface perpendicular to stress
5. Direction of crack changes to $45^\circ$

Brittle fracture

Little or no plastic deformation prior to fracture. Fracture surface is smooth.

More dangerous than ductile fracture.

• No warning sign
• Crack propagates at very high speeds
• No need for extra stress during crack propagation