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

625

2

hole with the same flaw. Mikheevskiy et al. (2012) examined the same safety-relevant configuration taking into account the failure concept developed by Noroozi et al. (2007) and the weight function method, whereas Boljanović et al. (2017) employed the crack growth concept discussed by Zhan et al. (2014) and the J -integral method. Furthermore, Boljanović et al. (2019) suggested that the two-parameter driving concept proposed by Huang and Moan (2007) associated with the finite element method can be applied for assessing the behavior of elliptical flaws. The present research work proposes a computational framework for exploring elliptical corner damage that directly affects the performances of large moving systems from a sustainability point of view. In this context, by generating novel damage tolerance-based solutions and monitoring the evaluation of residual life over time, it is revealed that emergence of failure modes is driven by the interaction between the stress raiser effect and the cyclic loading effect. Through the use of computational tools, the ability to gain a better understanding of the fatigue induced surface flaw mechanism is discussed.

Nomenclature a

crack length

material constant of fatigue crack growth law

C

da / dN crack growth rate in depth direction db / dN crack growth rate in surface direction K stress intensity factor N number of loading cycles P applied force Q ellipse shape factor R stress ratio S applied stress t thickness w width  K stress intensity factor range  P applied force range  S applied stress range  Poisson’s ratio

Subscripts f

failure

maximum value

max

initial

0

2. Failure evaluation for surface elliptical flaw The driving mode progression due to an elliptical crack-like stress raiser (Fig. 1) was evaluated through relevant crack growth rates discussed by Broek (1989) in depth and surface crack direction, respectively, given by

dN da

dN db

A A A C K K  2 max

B B B C K K  2 max





,

(1)

where a , b and da/dN, db/dN are crack length and corresponding crack growth rate in both depth and surface direction, respectively, K maxA , K maxB and  K A ,  K B represent maximum stress intensity factors and stress intensity factor ranges for two critical crack growth directions,, and C A , C B are material parameters experimentally obtained.