Theoretical and Practical Implications Derived From the Formulation of the Theory of Critical Distances

The Theory of Critical Distances comprises several methodologies that allow fracture, fatigue, and stress corrosion cracking phenomena to be analyzed. Such methodologies are usually referred to as the Point Method (PM), the Line Method (LM), the Area Method (AM), and the Volume Method (VM). All of them provide analyses where the corresponding material resistance (e.g., fracture toughness, fatigue threshold, and stress corrosion cracking threshold) is used together with an additional material parameter with length units (the critical distance, L). Moreover, the accuracy of these four approaches is very similar, but the PM and the LM have a much simpler application. When dealing with fracture processes, the TCD allows fracture conditions for structural materials in the presence of notch‐type defects to be established, and simple formulas for estimating the apparent fracture toughness (i.e., the fracture resistance in the presence of notches) to be obtained. This paper provides a number basic reasonings related to both the PM and/or the LM formulations that allow different straightforward conclusions to be derived, with significant theoretical and practical implications. Real cases with experimental results are also included, exemplifying what is discussed in the theoretical analysis.