PSI - Issue 28

Levke Wiehler et al. / Procedia Structural Integrity 28 (2020) 925–932 Author name / Structural Integrity Procedia 00 (2019) 000–000

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3. Results 3.1. Determination of time and location of crack initiation

To determine the time and location of crack initiation, the quotient Q i is formed by dividing the individual potentials P front and P back by the relative potential of the narrow side P narrow , i.e. the potential in the center of the specimen’s width (equation 2). The run of the quotients is visualized in a graph to determine the point in time and the location of the crack initiation. ����� � � ����� � ������ and ���� � � ���� � ������ (2) At the beginning of the experiment, both quotients have the value Q front = Q back = 1. A crack is expected as soon as an imbalance between the quotient Q front and the quotient Q back occurs or a significant decrease or increase in both quotients becomes apparent. Using the potential quotients, a tendency of the initial crack to the front- or backside of the specimen is quickly apparent, without neglecting the potential difference of the narrow side. There are three possible cases for crack initiation, with each case also applying to the opposite quotient (figure 2):

Fig. 2. (a) One-sided crack; (b) centered crack; (c) two-sided crack with associated run of the quotients.