paper has been already discussed by Prof. P. S. Theocaris in the same journal. Professor Theocaris has chosen to discuss the paper indirectly by presenting in an exhausting manner the philosophical, physical and scientific statements supporting the T-criterion and, hence, proving unnecessary, for the time being, serious modifications.
However, the present discusser believes that technical remarks are also worthy, because sometimes a seemingly minor error or misunderstanding causes considerable disasters.
Anyhow there are a few points in the above paper which need clarification. It is hoped that it will be proved helpful for both the author and the interested reader. To begin with:
(1) In the "Introduction and Background" of the paper there are two (and perhaps more) remarks, asking for an answer: (la) The author seems not to be aware of the inherent irrationality of the equality S,, = S,, when describing the Scriterion. Because S is a positive quantity starting from zero and increasing with the external load, obviously at a certain load level the equality S,,, = S,, will be first fulfilled instead of Smin = S,,. The question is why the crack does not propagate to the direction where S,,,,, reaches the critical value S,,. In our opinion[l, 21 it happens because the crack does not "care" about total S but only about S,.