Issue 50

M.F. Borges et al., Frattura ed Integrità Strutturale, 50 (2019) 9-19; DOI: 10.3221/IGF-ESIS.50.02 9 Focused on Crack Tip Fields Effect of yield stress on fatigue crack growth M.F. Borges, F.V. Antunes, P. Prates, R. Branco, M.C. Oliveira University of Coimbra, Portugal micaelfriasborges@outlook.pt fernando.ventura@dem.uc.pt, http://orcid.org/0000-0002-0336-4729 pedro.prates@dem.uc.pt , ricardo.branco@dem.uc.pt, marta.oliveira@dem.uc.pt A BSTRACT . Fatigue crack growth (FCG) depends on loading, geometry and also material properties. Since FCG is supposedly linked to crack tip plastic deformation, material’s yield stress, Y 0 , is an important parameter. The main objective here is to develop a parametric study focused on the effect of Y 0 on FCG. The study is based on the plastic CTOD,  p , determined numerically using the finite element method. The increase of Y 0 was found to decrease  p , and therefore FCG rate. The variation is non-linear, being more important for lower values of Y 0 . The effect of Y 0 was found to be much more relevant for the 7050 aluminium alloy than for the 304L stainless steel, which indicated a major influence of isotropic saturation stress. With the inclusion of crack closure, the reduction of  p is kept, but there is a substantial reduction of  p and therefore of FCG rate. K EYWORDS . Fatigue Crack Growth; Plastic CTOD; Yield stress; Crack closure. Citation: Borges, M.F., Antunes, F.V., Prates, P., Branco, R., Oliveira, M.C., Effect of yield stress on fatigue crack growth, Frattura ed Integrità Strutturale, 50 (2019) 9- 19. Received: 24.05.2019 Accepted: 01.07.2019 Published: 01.10.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION atigue Crack Growth (FCG) greatly depends on material parameters, however most of the studies are related to loading and geometrical parameters. Studies based on material parameters are less common in literature due to the difficulty of implementing parametric experimental tests because the parameters cannot be changed one by one. Also, the numerical tools available are typically devoted to studying the effect of loading parameters. This article is centered on the study of the effect of yield stress on FCG, using a numerical approach. Since FCG is related to non-linear and irreversible phenomena acting at the crack tip, it makes sense that the yield stress is an important parameter. The methodology proposed by Antunes et al. , based on plastic CTOD, was used to develop this parametric study  1  . This approach is based on the assumption that FCG is linked to crack tip plastic deformation, and that the plastic CTOD quantifies this deformation. The plastic CTOD includes crack closure in a natural way and excludes the elastic deformation, which is not expected to contribute to FCG. F