N. Eswara Prasad et al. Engineering Fracture Mechanics 71(2004)2589-2605 (Kin)Local /r Fracture process 主主 Ja or Jc Fig. 6 Schematic diagram showing the crack tip stress singularity for(a) homogeneous material, (b) heterogeneous material, such CFCCs. (c)J-contour for the heterogeneous material. Note the large wake zone of the heterogeneous material (in b)as compared to The total fracture energy release rate, J or Je, encompasses different stages of fracture events (listed in Section 1)in the"fracture zone""(see Figs. I and 6c). In case of homogeneous materials, fracture processes ahead of or at the crack tip predominantly contribute to the overall fracture resistance. Hence, the energy release rate at the crack tip(termed as Jtip ) predominates the values of J2. On the other hand, the dis- continuous materials such as CFCCs, the wake zone effects predominate in comparison with the tip. Hence, in these cases the overall energy release rate Jx essentially includes fracture energy corresponding to wake zone effects and the contributions from the crack tip processes or crack tip fracture zone (tip) are only marginal. Further, the total fracture energy release rate c or a, or some times referred to as Ge)is the most commonly used parameter when a fracture process involves two or more different components of fractureThe total fracture energy release rate, Ja or Jc, encompasses different stages of fracture events (listed in Section 1) in the ‘‘fracture zone’’ (see Figs.1 and 6c).In case of homogeneous materials, fracture processes ahead of or at the crack tip predominantly contribute to the overall fracture resistance.Hence, the energy release rate at the crack tip (termed as ‘Jtip’) predominates the values of Ja.On the other hand, the dis￾continuous materials such as CFCCs, the wake zone effects predominate in comparison with the Jtip.Hence, in these cases the overall energy release rate Ja essentially includes fracture energy corresponding to wake zone effects and the contributions from the crack tip processes or crack tip fracture zone (Jtip) are only marginal.Further, the total fracture energy release rate (Jc or Ja, or some times referred to as Gc) is the most commonly used parameter when a fracture process involves two or more different components of fracture. Fig.6.Schematic diagram showing the crack tip stress singularity for (a) homogeneous material, (b) heterogeneous material, such as CFCCs.(c) J-contour for the heterogeneous material.Note the large wake zone of the heterogeneous material (in b) as compared to the homogeneous material (in a). N. Eswara Prasad et al. / Engineering Fracture Mechanics 71 (2004) 2589–2605 2597