In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing (ECAP), a new approach to characterize the equivalent strain was proposed. The results show that there exists better accordance between mechanical property (such as hardness or strength) and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as: ε=k0exp[-(k1M-k2)2], where M is the strength or hardness of the material, k1 is the modified coefficient (k1 ∈ (0, 1)), k0 and k2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material, respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter relating to material property rather than the classical geometry equation.
