Issue 35

L. C. H. Ricardo et alii, Frattura ed Integrità Strutturale, 35 (2016) 456-471; DOI: 10.3221/IGF-ESIS.35.52 466 More recently Wei and James [109] reported that after growing a virtual plane strain fatigue crack for a few cycles, there is no contact in the region immediately behind the crack tip and the contact pressure along the crack faces is discontinuous. Zao et al. [110] modelled a CT specimen under plane stress and plane strain. They did not observe plasticity-induced crack closure under plane strain during steady state crack growth under cyclic tension, although they found significant levels of closure under plane stress. Solanki et al. [75] present a review of crack propagation in plane stress and plane strain conditions. A M(T) specimen was modeled with an externally induced T -stress to observe the subsequent change in closure levels under plane-strain. A T- stress was induced by applying tractions parallel to the crack in addition to the conventional tractions perpendicular to the crack. Fig. 7 shows the variation in the crack tip plastic zone size accordingly with mesh. Fig. 8 shows the difference of result in node release at minimum and maximum load compared by Solanki et al. [76]. Figure 7 : Variation in Crack Tip Plastic Zone Size with Mesh [75]. Figure 8 : Comparison of Crack opening values based on crack advance scheme [75]. Figure 9 : Middle-Crack Tension Specimen Subjected to uniform stress [112]. Figure 10 : Crack Propagation Model Quarter of Middle Tension [113]. Chermahini [111] present some crack propagation analyses using 3D model and plane strain model to determine the crack opening level. On the specimen surface and in the mid-plane the crack-opening stress levels tend to be two-dimensional solutions for plane stress and plane strain conditions, respectively. Fig. 9 shows the geometry used by Chermahini et al. [112].