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

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