Discussion: “A Displacement Equivalent-Based Damage Model for Brittle Materials” (Soh, C. K., Liu, Y., Yang, Y., and Dang, Y., 2003, ASME J. Appl. Mech., 70, pp. 681–695)

In the article, the damage discussed is the microcracks existing in any brittle material. It is a time-independent theory. However, the authors seem not to know that I published two books: Rock Rheology by N. Cristescu, 1988, Kluwer Academic, 336 pp. and Time Effects in Rock Mechanics by N. D. Cristescu and U. Hunsche, 1998, Wiley, 342 pp. In these books are chapters on damage: in the first, “Damage and Failure of Rocks” and in the second, “Damage and Creep Failure.” The damage I have considered is based on the same idea: increase or decrease of microcracks, with the distinction that I have considered also the hydrostatic tests, which the authors disregard. For instance, in Fig. 1 (Fig. 4.25) (all figures are from the second book) one can see the initial contribution of the hydrostatic contribution on the alumina powder obtained in a three-axial test apparatus. I have considered the...