Fracture in materials describes the process of a material breakage under stress. When a fracture occurs, characteristic behaviors can be observed and analyzed. Listed below are some characteristics of fracture:
- Cleavage planes are smooth, flat, and often reflective surfaces along which the material cleaves or splits. These occur along crystal boundaries, which are planes of weakness in the material.
- Dimples are round depressions or irregularities on the fracture surface. They are characteristic of ductile materials and suggestive of plastic deformation and energy absorption, immediately prior to fracture.
- Shear lips are indicative of fracture resulting from micro-void coalescence. The surface of the fracture often looks fibrous or powdery.
- Hackles are chevron patterns seen on the fracture surface. They indicate (point towards) the direction of crack propagation and can help determine the mode of fracture.