Issue 71

S. Eleonsky et alii, Fracture and Structural Integrity, 71 (2025) 246-262; DOI: 10.3221/IGF-ESIS.71.18

Values of hole diameter increment u Δ and v Δ in principal stress directions, which are essential for residual stress determination by Formulae (1), follow from the relations inherent in speckle-pattern interferometry method [25]:





 u u N

 v v N

Δ Δ

Δ Δ

,

(2)

sin 2 Ψ

sin 2 Ψ

where  = 532 nm is the wavelength of laser illumination;

  Ψ /4 is the angle between inclined illumination and

normal observation directions; v N Δ represent differences in absolute fringe orders counted over the solitary fringe pattern between two basic points corresponding to the directions of principal stresses 1 σ and 2 σ , respectively. Two basic points corresponding to each fringe pattern are defined as the intersection points of the hole diameter coinciding with a specific principal stress direction and the edge of the probe hole. The horizontal and vertical diameters are related to the u N Δ ( 1 σ - direction) and v N Δ ( 2 σ - direction) absolute fringe order difference, respectively. Illustrations of fringe count way and identification procedure of physical sign of in-plane displacement components are presented in works [23– 25]. Initial experimental data extracted from the fringe patterns and the calculated values of the principal residual stress, which are obtained through the use of formulae (1) and relations (2), are listed in Tab. 2 and Tab. 3 for static indentation and impact influence, respectively. u N Δ and

Distance from dimple edge to probe hole centre x y Δ / Δ , mm

Specimen/ Point

u N Δ , fringes –29.0 –19.0 +24.0 –17.5

v N Δ , fringes +24.0 +14.0 –20.0 +13.0 –11.5

1 σ , MPa

2 σ , MPa

u Δ , μ m

v Δ , μ m

1.0 ( x 1 Δ ) Fig. 1b 2.30 ( x 2 Δ ) Fig. 1b 0.63 ( y 1 Δ ) Fig. 1c 4.20 ( x 2 Δ ) Fig. 1c 3.87 ( y 3 Δ ) Fig. 1c 6.00 ( y 4 Δ ) Fig. 1c

S_1/P1 S_1/P2 S_2 /P1 S_2 /P2 S_2 /P3 S_2 /P4

–11.02 –7.22 +9.12 –6.65 +3.23 +2.85

+9.12 +5.32 –7.60 +4.94 –4.37 –2.85

– 162.0 – 111.0 +135.1 – 106.3 +33.9

+106.0 +57.9 –88.3 +52.1 –63.2 –37.9

+8.5 +7.5

–7.5

+37.9

3.05 ( x 1 Δ ),( y 1 Δ ) Fig. 1f (centers of the dimple and probe hole coincide)

–30.0

–30.0

–11.4

–11.4

S_3/P1

–336.6

–336.6

Table 2: The results of fringe patterns interpretation and values of principal residual stress components near static dimple.

Distance from dimple edge to probe hole centre x y Δ / Δ , mm

Specimen/ Point

u N Δ , fringes

v N Δ , fringes +11.5 +10.0

1 σ , MPa

2 σ , MPa

u Δ , μ m

v Δ , μ m

1.0 ( x 1 Δ ) Fig. 1d 7.98 ( x 2 Δ ) Fig. 1d 1.0 ( y 1 Δ ) Fig. 1e 2.80 ( y 2 Δ ) Fig. 1e 3.52 ( x 3 Δ ) Fig. 1e 9.05 ( y 4 Δ ) Fig. 1e

D_1/P1 D_1/P2 D_2/P1 D_2/P2 D_2/P3 D_2/P4

–14.5

–5.51 –3.42 +9.31 +3.42 –3.39

+4.37 +3.80 –0.76

–82.4 –42.5

+49.0 +53.6 –58.1 +25.7 +93.5 +68.3

–9.0

+24.5 +9.0 –10.5 +2.5

–2.0

+192.1 +68.4 +38.7 +43.0

0.0

0.0

+15.5

+5.89

+7.5

0.95

2.85

3.05 ( x 1 Δ ),( y 1 Δ ) Fig. 1f (centers of the dimple and probe hole coincide)

–14.0

0.0

–5.32

0.0

D_3/P1

–113.2

–40.0

Table 3: The results of fringe patterns interpretation and values of principal residual stress components near impact dimple.

256