PSI - Issue 81

Leonid Voytovych et al. / Procedia Structural Integrity 81 (2026) 287–291

288

Nomenclature σ R і σ θ

radial stresses

circumferential stresses

σ φ σ R σ Z

θ М membrane stresses

М і σ

stresses along the hole generators stress concentration factor

К P

axial force

2. Methods of research The investigations were carried out using the photoelastic method with the application of the stress-freezing technique (Kryzhanivskyi et al. (2019)). The “freezing” mode involves gradually increasing the temperature of the loaded plate in a heating cabinet to a highly elastic state (temperature 120 °C), keeping the sample at this temperature for one hour, and then gradual ly cooling it to room temperature. The plates were manufactured from an optically sensitive epoxy resin material (ED-16M) and contained two diametrically opposite circular holes with a diameter of 12 mm. The sketches and dimensions are shown in Fig. 1 and Table 1 . The axes of the holes passed through points located on a circle with a radius of 55 mm. The plates were freely supported along a circular contour with a radius of 95 mm and subjected to an axial load distributed over the area of a central pin with a radius of 20 mm (P=19 N – for a thin plate, P=60 N – for a plate of medium thickness).

a

b

Fig. 1. Loading scheme: (a) loading configuration; (b) plate dimensions.

Table 1. Plate sizes

ℎ⁄

Plate radius R , mm

Plate thickness h , mm

№ Plate

1 2

100 100

4 12

0.04 0.12

After stress freezing, the plates were cut into slices (Fig. 2): (a) meridional slices (in the ROZ plane, perpendicular to the diameter along which the holes are located); (b) a set of slices perpendicular to the meridional ones; (c) slices perpendicular to the hole axis. The thickness of all slices ranged from 1 mm to 2 mm. The optical path difference was measured using a KSR-5 instrument. Photoelastic measurements in sections were obtained on a coordinate-synchronous polarimeter. The stress separation was carried out only on the free contour, where one of the principal stresses is always zero. With normal illumination of meridional sections and sections perpendicular to them, the stress distribution along the radius and on the surfaces of the plate was obtained.