The term fracture of material may be defined as its fragmentation or separation, under action of an external force, into two or more parts.
Materials have some or the other weakness due to presence of submicroscopic defects (aka cracks). The cracks act as points of stress concentration. Surface roughness and surface scratches also serves as notches for stress concentration. When the stress exceeds the cohesive strength in region, cracks propagate to cause complete failure viz fracture
Based on types of external forces, deformations and crack propagation, Fractures may be classified into the following four types:
- Brittle Fracture
- Ductile Fracture
- Creep Fracture
- Fatigue Fracture
Fractures may also be classified as below based on metallographic examination as
- Trans-granular (aka trans-crystalline) fracture
- Inter-granular (aka inter-granular) fracture.
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