Electrochemical Hydrodynamic Impedance EHI

Chung and Macdonald [1981] defined a transfer function for the propagation of a crack through an elastic-plastic material under transient loading conditions. Designating the stress intensity as K/if) and the instantaneous crack velocity as da f)ldt (both time-dependent quantities), the fracture transfer function may be defined as 

It is clear, therefore, that the system is nonlinear, so that Hf(s) is not expected to obey the Kramers-Kronig transforms. 

The parameter R provides a measure of the resistance to crack propagation, such that 1/R is proportional to the steady state crack velocity. The R values obtained from the intercept at. y = 0 indicate that the steady state crack velocity is independent of stress intensity. 

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