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

626

3

Furthermore, through the fatigue analysis herein described, the number N of loading cycles to failure was assessed, after integration of fracture mechanics-based solutions (Eq. (1a) and (1b)) from initial a 0 , b 0 to final a f , b f crack growth lengths in depth and surface direction, respectively, as follows:    f a a A A A C K K da N 0 2 max ,    f b b B B B C K K db N 0 2 max (2) Under the threat of serious strength degradation and sudden loss of bearing capacities of large moving systems, reliable damage tolerance-based strategies for exploring surface stress-raisers have become an important trend in safe-integrity assessments. In this regard, a software program is herein developed (using the Euler’s numerical integration method) to generate complex driving mode interactions in the micro-notch zones under cyclic loading.

Fig. 1. Cyclically loaded quarter-elliptical damage (a) the dog bone plate and (b) the finite plate.

3. Driving intensity analysis Owing to growing regulations over fatigue degradation of large moving systems, the demand for reliable stress intensity evaluations through analytical and/or numerical concepts (Kim et al., 2003, Boljanović et al., 2017, Boljanović and Carpinteri , 2020, Carpinteri, 1994) is rising. Thus, the behavior of elliptical corner damage (Fig. 1) is here examined employing the following fracture mechanics-based solutions (Newman and Raju, 1984):

Q K F S a qec    

(3)

where  K and  S are stress intensity factor range and applied stress range, respectively, and a is crack length in depth direction. Through safety-relevant analysis, the effect of a crack-like elliptical flaw coupled with cyclic loading effects was evaluated using the ellipse shape factor Q and corrective factors M 1 , M 2 , M 3 , g 1 , g 2 , in the case of a / b ≤ 1 (Newman and Raju, 1984), expressed as follows: 1.65 1 1.464   Q (4)

b a

  

  

   

   

2

4

 

  

qec t F M M a 2 1     

t M a 3

g g f f 1 2 

    

(5)

w

b a

M 1.08 0.03 1  

(6)