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It is the emission of light from the fracture (rather than rubbing) of a crystal, but fracturing often occurs with rubbing. Depending upon the atomic and molecular composition of the crystal, when the crystal fractures, a charge separation can occur, making one side of the fractured crystal positively charged and the other side negatively charged.
Full cortical fractures occur if the repetitive stress continues. Only timely detection and appropriate management can interrupt this sequence. [1] Fatigue fractures are more frequent in women which may be due to the relatively smaller bones of women. Moreover, pregnancy is a well-recognized risk factor for femoral neck fatigue fracture.
The driving mechanism responsible is an interplay between internal (e.g. composition, grain size and lattice-preferred orientation) and external (e.g. temperature and fluid pressure) factors. [ 1 ] [ 2 ] These mechanisms produce a range of micro-structures studied in rocks to constrain the conditions, rheology , dynamics , and motions of ...
The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displacement develops perpendicular to the surface, it is called a normal tensile crack or simply a crack ; if a displacement develops tangentially, it is called a shear crack , slip band , or dislocation .
In fracture mechanics, the energy release rate, , is the rate at which energy is transformed as a material undergoes fracture.Mathematically, the energy release rate is expressed as the decrease in total potential energy per increase in fracture surface area, [1] [2] and is thus expressed in terms of energy per unit area.
The fracture may be preventable by using wrist guards during certain activities. [1] In those in whom the fracture remains well aligned a cast is generally sufficient. [2] If the fracture is displaced then surgery is generally recommended. [2] Healing may take up to six months. [1] It is the most commonly fractured carpal bone. [3]
Linear elastic fracture mechanics predicts that a crack will extend when the stress intensity factor at the crack tip is greater than the fracture toughness of the material. Therefore, the critical applied stress can also be determined once the stress intensity factor at a crack tip is known.
In fracture mechanics, a crack growth resistance curve shows the energy required for crack extension as a function of crack length in a given material.For materials that can be modeled with linear elastic fracture mechanics (LEFM), crack extension occurs when the applied energy release rate exceeds the material's resistance to crack extension .