Single fracture processes

The stress-intensity factors are quite different from stress concentration factors. For the same circular hole, the stress concentration factor is 3 under uniaxial tension, 2 under biaxiai tension, and 4 under pure shear. Thus, the stress concentration factor, which is a single scalar parameter, cannot characterize the stress state, a second-order tensor. However, the stress-intensity factor exists in all stress components, so is a useful concept in stress-type fracture processes. For example. 

Compare and contrast ductile with brittle fracture processes/pattems in single crystals and polycrystals. 

In the next chapter we see that either a single craze or a bunch of crazes forms at a crack tip. The ease of crack growth depends on which of this occurs. Therefore, it is important to observe the number and geometry of the crazes involved in a fracture process. 

FIGURE 7.4 Stress, P strain, e curves for a pure zinc single crystal and a zinc single crystal covered with mercury film. (From Rehbinder, P.A. and Shchukin, E.D., Surface phenomena in solids during deformation and fracture processes, in Progress in Surface Science, S.G. Davison (Ed.), Pergamon Press, Oxford, U.K., 1972, pp. 97-188 Shchukin, E.D. and Lichtman, V.I., Doklady AN SSSR., 124, 307, 1959.)... 

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