Issue 45

G. Gomes et alii, Frattura ed Integrità Strutturale, 45 (2018) 67-85; DOI: 10.3221/IGF-ESIS.45.06

where  min

and  max

correspond to the minimum and maximum applied stresses, and K Ieqmin

and K Ieqmax

are the stress

intensity factors.

Figure 2: Schematic of incremental crack-extension direction [12].

Formulating an analysis at a maximum stress level, we can define an intensity factor range,  K Ieq

, which is given by,





1

 







Ieq K K

K

K

R

(12)

Ieq max

Ieq min

Ieq max

Applying the Paris Law [15], we can calculate the crack growth rate as

 da C K dN  

 m

(13)

Ieq

where a is the crack length, N is the number of load cycles, C and m are empirical constants of the material. Eqn. (13) expresses the fatigue life and stands for the variation of the number of load cycles required to propagate the crack, or the length advanced at each increment.

M ATERIAL AND METHODS

ere, the automation of the modelling process and calculations by the BemCracker2D code, together with BEMLAB2D GUI, as well as the experimental methodology and the FEM models due Miranda [8] compose the materials and methods applied in this work. Automatic Crack Growth Automating a crack propagation analysis means describing the whole geometry of the two-dimensional model of the cracked structure and assigning a boundary element discretization for it, physical attributes such as loads, support conditions and material properties. This description consists of a set of geometric continuous and discontinuous quadratic boundary elements that defines the contour of the regions and the cracks, respectively, as well as boundary conditions associated to the elements and domain parameters associated to the regions. H

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