**3. Materials and Methods**

#### *3.1. Description of Specimens*

The tests were carried out on four steel plates with dimensions of 50 cm × 50 cm and 3 mm thickness. A reference model was the first element without damage (plate #1). The other three plates contained a circular hole of variable diameter: 2 cm (plate #2), 5 cm (plate #3) and 10 cm (plate #4), which represented damage of a surface type. Holes were made through the entire thickness of the plate. The centres of all holes were placed symmetrically in the *y*-axis direction and at a distance of 18 cm from the outer edge of the plate in the *x*-axis direction. The geometry of the test models is shown in Figure 2. Photographs of the plates used for the experimental tests are presented in Figure 3.

**Figure 2.** The geometry of the tested plates: (**a**) plate without damage (#1); (**b**–**d**) plates with surface damage (#2–#4).

**Figure 3.** Photographs of tested plates (models #1–#4).
