Issue 73

V. Pisarev et alii, Fracture and Structural Integrity, 73 (2025) 108-130; DOI: 10.3221/IGF-ESIS.73.08

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

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

observation directions; v N  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  ( 1 σ -direction) and v N  ( 2 σ -direction) absolute fringe order difference, respectively. Illustrations of fringe count way to determine u N  and v N  parameters as well as identification procedure of physical sign of in-plane displacement components are thoroughly presented in works [20, 23]. Initial experimental data extracted from the fringe patterns and the calculated values of the principal residual stress components, which are obtained using formulae (1) and relations (2), are listed in Tab. 2, Tab. 3 and Tab.4 for specimen CP_S, CP_D-20 and CP_D-25, respectively. u N  and

Point/ Dimple

Distance from dimple center to probe hole center x / y , mm

u N  , fringes –17.5 –13.5 +10.0 +27.0 –23.0 –18.5 +10.0 +10.0

v N  , fringes –22.0 +7.5 –13.0 –20.5 +15.0

1 σ , MPa

2 σ , MPa

Δ u , μ m

Δ v , μ m

1 x = 0, 1 y = 0 2 x = 7.0, 2 y = 0 3 x = 0, 3 y = 7.0 4 x = 0, 4 y = 3.7 5 x = 3.9, 5 y = 0 6 x = 6.8, 6 y = 0 7 x = 0, 7 y = 10.3 8 x = 0, 8 y = 15.8

1/A 2/A 3/A 4/B 5/B 6/B 7/B 8/B

–6.65 –5.13 +3.80 –7.03 –2.85 +3.80 +3.80 +10.26

–8.36 +2.85 –4.94 –7.79 +3.04 +2.85 –4.56 –1.52

–208.2 –86.4 +41.4 +146.8 –140.4 –125.3 +44.4 +68.7

–230.9 +18.5 –70.3 –77.9 +51.6

+8.0 –12.0

+5.9

–65.6

–4.0

–2.0 Table 2: The results of fringe patterns interpretation and values of principal residual stress components near contact dimple in CP_S coupon.

Point/ Dimple

Distance from dimple center to probe hole center x / y , mm

u N  , fringes

v N  , fringes –14.0 +12.5

1 σ , MPa

2 σ , MPa

Δ u , μ m

Δ v , μ m

1 x = 1 y = 0

1 6 2 8 5 7 3 4 9

–9.0 –8.0 –9.0

–3.42 –3.04 –3.42 –3.80 +7.60 +5.13 +6.46 +4.75 +5.32

–5.32 +4.75 +3.61 +3.23 –4.75 –4.75 –3.61 –3.99 –2.26

–115.5 –26.8 –43.9 –55.1 +123.8 +108.6 +69.2 +92.9 +71.3

–140.6 +76.8 +49.5 +38.4 –40.5 –60.1 –25.2 –47.2

6 x =4.2, 6 y = 0 2 x =7.2, 2 y = 0 8 x =9.6, 8 y = 0 5 x =0, 5 y = 3.8 7 x =0, 7 y = 6.8 3 x =0, 3 y = 7.2 4 x =0, 4 y = 11.1 9 x =0, 9 y = 10.0

+9.5 +8.5 –12.5 –12.5

–10.0 +20.0 +13.5 +17.0 +12.5 +14.0

–9.5

–10.5

–6.0

–6.8

(3 7)/2 x  = 0, (3 7)/2 y  = 7.0 (4 9)/2 x  = 0, (4 9)/2 y  = 10.5

(3+7)/2









+90.0

–42.7

(4+9)/2









+81.1

–27.0

Table 3: The results of fringe patterns interpretation and values of principal residual stress components near contact dimple in CP_D 20 coupon.

122