I
Break in a bone , caused by stress.
It causes pain, tenderness, and inability to use the part with the fracture. The site appears deformed, swollen, and discoloured, and the bone moves in abnormal ways. It must be protected from weight bearing and movement between the broken ends while it heals, producing puttylike new tissue that hardens to join the broken pieces together. Complications include failure to heal, healing in the wrong position, and loss of function despite good healing. Fractures in joints present a particularly serious problem, often requiring surgery. See also osteoporosis .
II
In engineering, rupture of a material too weak to sustain the forces on it.
A fracture of the workpiece during forming can result from flaws in the metal; these often consist of nonmetallic inclusions such as oxides or sulfides trapped in the metal during refining. Laps are another type of flaw, in which part of a metal piece is inadvertently folded over on itself but the two sides of the fold are not completely welded together. Structural and machine parts subject to vibrations and other cyclic loading must be designed to avoid fatigue fracture. See also ductility , metallurgy , strength of materials , testing machine .
III
In mineralogy, the appearance of a surface broken in directions other than along cleavage planes.
There are several kinds of fractures: conchoidal (curved concavities resembling shells, as in glass); even (rough, approximately plane surfaces); uneven (rough and completely irregular surfaces, the commonest type); hackly (sharp edges and jagged points and depressions); and splintery (partially separated splinters or fibres).