A craze-initiation model

The applied global set of stresses is concentrated at surface grooves, where the pair of stresses and produce different but complementary effects. To initiate crazing nascent nano-cavities need to be produced by local plastic flow under 

In the craze-initiation model, the above mechanistic considerations are combined in an approximate manner (Argon 2011). Thus, at craze initiation at the local plastic enclaves of the surface grooves, the local mean normal stress must reach such a level as to satisfy 

The porosity p that enters into the craze-initiation condition is, in turn, governed by the increasing shear strain y in the plastic enclaves and increases at a rate paralleling i.e., 

15) the concentrated local mean normal stress ai and deviatoric shear stress Si are in the plastic enclaves that result in craze initiation (the time taken for the formation of 10 crazes per cm in 10 s in the tension torsion experiments is taken as the mean period r of craze initiation), which needs to be stated in terms of global stresses a and s through the use of the average stress eoneentrations and of surface grooves. How this is done is discussed below in Section 11.6 comparing the model predictions with the results of the tension torsion experiments. 

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