PSI - Issue 39

Slobodanka Boljanović et al. / Procedia Structural Integrity 39 (2022) 624 – 631 Slobodanka Boljanović et al. / Structural Integrity Procedia 39 (2022) 624 – 631

627

4

 0.3 0.44 1.06

M

  

(7)

2

b a

15

b a

b a

  

   

   

  

0.5 0.25

14.8 1

M

  

(8)

3

1 0.08 0.4       t a       t a        1 0.08 0.15

     

2

 3

1 sin

g



(9)

1

   

     

2

  

 3

1 cos

g



(10)

2

where F qec is corrective function for the elliptical corner flaw, b and t are crack length in surface direction and plate thickness, respectively. It is worth mentioning that f   is a corrective function related to the location angle  on the crack front, as is discussed by Newman and Raju (1984). Furthermore, the influence of plate width associated with thickness and crack shape effect is theoretically investigated employing the following corrective factor:

4 3 2 1 0.2 9.4 19.4 27.1          w f

(11)

 w b 

t a

    w b

  

0.5

(12)

where w is the width of the plate.

4. Fatigue assessment through developed computational framework 4.1. Residual life-time evaluation

Firstly, the failure of doge bone plate (Fig. 1a) made of 2024T3 aluninium alloy is explored under cyclic loading. The initial crack-like elliptical damage is characterized by the following crack lengths a 0 = b 0 =20  m in depth and surface direction, respectively, whereas width and plate thickness are equal w = 25.4 mm and t = 2.3 mm. In the case of two values of stress ratio R = 0 and -1, the residual life was assessed for relevant maximum stresses listed in Table 1, adopting the material parameters C A = C B =1.2×10 -10 for the two critical crack growth directions. Through the damage tolerance-based analysis, the fatigue endurance was evaluated in terms of the stress intensity factor and plate life, using Eq. (3)-(12) coupled with Eq. (1) and Eq. (2), respectively. Relevant theoretical outcomes generated (number of loading cycles versus crack length in depth and surface direction) are shown in Fig. 2a, 3a and 2b, 3b, respectively. Furthermore, since the plate failure due to the same micro-notch flaw was assessed within a previous work of the present authors, such theoretical outcomes and experiments reported by Grover et al. (1953) are compared with those generated through this research, as is listed in Table 1. Such a safety-relevant analysis shows that different outcomes are in a quite good agreement. It can be also inferred that, with respect to appropriate experiments reported by Grover et al. (1953), the computational strategy herein presented provides less conservative estimates for R = 0 while in the case R = -1 those whose trend is more conservative than outcomes obtained through the strategy previously discussed by Boljanović and Carpinteri (2020).