Issue 48

F. V. Antunes et alii, Frattura ed Integrità Strutturale, 48 (2019) 676-692; DOI: 10.3221/IGF-ESIS.48.64 676 Focused on the “Portuguese contributions for Structural Integrity” Stress intensity factor solutions for CTS mixed mode specimen F.V. Antunes, R. Branco, J.A.M. Ferreira, L.P. Borrego University of Coimbra, Portugal fernando.ventura@dem.uc.pt, http://orcid.org/0000-0002-0336-4729 ricardo.branco@dem.uc.pt, http://orcid.org/0000-0001-2345-6789 martins.ferreira@dem.uc.pt , borrego@isec.pt A BSTRACT . The Compact Tension Shear (CTS) specimen is used to study fracture and fatigue under mixed mode I/II loading conditions. The K solution available in literature was developed for fracture studies and does not consider the effect of crack deflection. The aim of present work is to develop K I and K II empirical solutions for cracks with different crack lengths, loading angles and crack orientations. A total number of 1120 cracked geometries were studied numerically with the finite element method and analytical solutions were fitted to the numerical predictions. An average difference of 0.53 % was found between numerical predictions and the analytical solution proposed for K I. For K II the difference is higher, but the equivalent stress intensity factor showed a difference of only 1% because K II is lower than K I . Experimental work was developed to study fatigue crack growth in CTS specimens. The cracks always adopted a direction approximately normal to loading direction, i.e., tend to propagate under mode I. K EYWORDS . CTS specimen; Stress intensity factor solution; Mixed mode Citation: Antunes, F. V., Branco, R., Ferreira, J.A.M., Borrego, L.P., Stress Intensity Factor Solutions for CTS Mixed Mode Specimen, Frattura ed Integrità Strutturale, 48 (2019) 676-692. Received: 06.10.2018 Accepted: 28.11.2018 Published: 01.01.2019 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 he majority of studies on fracture toughness and fatigue crack propagation are performed for mode I loading. However, there are situations where the cracks are not normal to maximum principal stress direction. Furthermore, at microscale level, depending on microstructural details, deviations in crack direction may occur even under mode I loading. Macroscopic crack deflection occurs due to asymmetry in stresses near the crack tip, resulting from multi-axial far field loading or from non-uniformity in mechanical properties near the crack tip. Since mixed mode loading tests are not standardized, several specimens have been developed. A geometry widely used to study mixed mode I/II loading, named compact tension shear (CTS), was developed by Richard  1  . It is a rectangular specimen with through crack and three holes for fixing on each side. This geometry was used to study fracture toughness and fatigue crack growth of metallic materials  2,3  , laminated composites  4  , adhesive joints  5,6  , Ce-TZP/alumina composite  7  , etc. Banks-Sills et al.  8  modified the CTS specimen considering a lower width at the center of the T