Thouless and Q.D. Yang

Beyond the boundary of any process zone that may exist is the far-field zone. 

It should be appreciated that the division of a material or system into the three regions of a cohesive, process and far-field zone is done for the convenience of analysis. There is a certain degree of flexibility in how these zones, that all 

An example for which the division into cohesive and process zones is not obvious is the problem of crack advance by void nucleation and coalescence in a ductile material [51]. Here, the cohesive zone might be taken to encompass all the cavities that contribute to crack growth. However, whether any cavitation off the fracture plane is associated with a process zone or with an extended cohesive zone is a matter of choice. Alternatively, the cohesive zone might be limited 

As discussed earlier, the area under the traction-separation curve Fi and Fiio) and the peak stress (a and f) are the important parameters that describe the cohesive tractions. The precise shape of the traction-separation law does not strongly influence the behavior of the system. For example, one generally useful form of a mode-I traction-separation law is shown schematically in Fig. 4. It should be appreciated that while the area and peak stress are the two important parameters from a mechanics point-of-view, they may not necessarily represent the fundamental parameters from a materials perspective. In some ways, the peak 

Some caution needs to be taken to ensure that the compliance of the elements is not so extreme that it influences the overall defonnation of the system. 

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Kafkahdis, M.S., Thouless, M.D., Yang, Q.D., and Ward, S.M. (2000) Deformation and fracture of adhesive layers constrained by plasticahy-deforming adherends. Journal of Adhesion Science and Technology, 14, 1593-1607. 

Yang Q D, Thouless M D, Ward S M (1999), Numerical Simulations of Adhesively-Bonded Beams Failing with Extensive Plastic Deformation, Journal of Mechanics and Physics of Solids, 47, 1337-1353. 

Yang, Q.D. and Thouless, M.D., Reply to comments on determining the toughness of plastically-deforming Joints, y. Mater Sci. Lett., 18, 2051-2053 (1999). 

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