PSI - Issue 42

Mike Nahbein et al. / Procedia Structural Integrity 42 (2022) 433–440 Author name / Structural Integrity Procedia 00 (2019) 000–000

437

5

a

b

Fig. 3. (a) Fracture surface and (b) calculated crack angle of a specimen with a crack initiation site at 0°. The colored lines correspond to the overload marks.

Unfortunately, the model used by Hartweg and Bär (2019) does not allow any quantifiable statement about the size of the crack and thus no possibility to specify a fixed value for the size of an initiated crack. To overcome this disadvantage the model was evolved by using the radius-coordinate of the normal vector n r as a criterion for the crack length. In figure 4 the radius-coordinate of the normal vector n r is plotted against the relative broken area a f /W f , calculated by diving the broken area a f by the total cross-sectional area W f of the specimen. The error-bars represent the standard deviation of the measured potential drop in an interval of 20 cycles before and after the overload. The plot shows a clear nonlinear relation between the radius-coordinate of the normal vector n r and the relative broken area a f /W f , and therefore allows an exact determination of the broken area.

MN-04 0°-10k-1

0.15

n r

0.10

n r

0.05

0.00

0

1

2

3

4

5

a f /W f [%]

Fig. 4. Diagram of the radius-coordinate of the normal vector n r against the relative broken area a f /W f for the specimen shown in figure 3.