PSI - Issue 68

662 Jan Klusák et al. / Procedia Structural Integrity 68 (2025) 660–665 Jan Klusák, Kamila Kozáková / Structural Integrity Procedia 00 (2025) 000–000 3 stored per unit volume and can be defined by the Eq. 2, where ij denotes the components of the stress tensor and ε ij represents the components of the strain tensor (Glinka, 1985). = ∫ +, +, (2) When the plane problems are considered, the Eq. 2 simplifies and reduces to Eq. 3 (Klusák and Krepl, 2018), where k depends on Poisson’s ratio and G is the shear modulus of material. = [2 -- .. ( − 1) + ( -& - + . & . )( + 1) + 4 . & - ] ∙ / ! 0 (3) = #(1 − )/(1 + ) (1 − 2 ) for plane stress for plane strain Knowledge of SED is used here to determine the critical distance and to predict fatigue life of different notches. 2. Critical distance determination The presented method uses knowledge of SED to determine the critical distance. The critical distance results from fatigue life curves that are represented here by the curves of w-N (SED vs. number of cycles to failure). Knowledge of strain energy density distribution in front of a notch tip is also required to determine the critical distance. To determine the critical distance, the w - N f curves are obtained from tests of smooth specimens and specimens with a model (calibration) notch, see left part of Fig. 1.

Fig. 1. The method of critical distance l cr determination. For particular number of cycles to failure, we can read the amplitudes of the SED of smooth and notched specimens. In the right part of Fig. 1 we can see the distribution of the SED in front of the calibration notch. The value corresponds to the average SED over the whole cross section (distance D /2 from the notch root). The critical distance is ascertained as the distance where the average SED equals to the value . Thus the critical distance is