Griffith crack propagation criterion

Starting from the energy balance of the process Griffith proposed the following so-called crack propagation criterion. This criterion corresponds to the value of stress causing further crack propagation ... 

Alternatively to the Griffith s energy criterion, In the 1950s Irwin calculated the stresses in the vicinity of a crack tip based on linear elasticity theory. He introduced a constant, K, the stress intensity factor, to characterize the magnitude of the stress field. If K (Kj in mode I) reaches a critical value Kc (Kjc), then the crack will propagate in the material Kjc is generally expressed in MPam. ... 

The energy criterion for fracture is simply an extension of Griffith s hypothesis which describes quasi-static crack propagation as the conversion of the work done, Wd, by the external force and the available elastic energy stored in the bulk of the specimen, U, into surface free energy, y. It may be written ... 

Griffith [4] has evolved a criterion for fracture based on the energy release rate. When a crack propagates, two new surfaces are created. The energy supplied by means of applied stress is utilized in creating these surfaces. The rate at which this energy is released exceeds the rate at which the energy is consumed that point, at which it exceeds, marks the critical condition for fracture. 

Despite the shortcomings of the measurement method it is important to understand the mechanism of ESC. If there is no environmental effect, the mechanism can be described in terms of classical slow crack growth in air. Based on Griffith criterion, when the crack propagation behavior sufficiently satisfies linear elastic fracture mechanics (LEFM) conditions, the slow crack growth resistance is... 

The energetic criterion, according to which the crack development into a mechanically solicited composite releases a certain amount of elastic energy that is stocked in material and can be evaluated. When its level attains a critical value, G, the cracks will propagate until the material s fracture. The critical energy of propagation represents an intricate characteristic of material, and in the case of brittle fracture, the Griffith criterion can be ex-... 

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