Issue 8

K. G. Kodancha et alii, Frattura ed Integrità Strutturale, 8 (2009) 45-51; DOI: 10.3221/IGF-ESIS.08.04 48 Figure 3 : A typical Finite element mesh used in the analysis. Figure 4 : A schematic diagrams of elements used in the definition of the interaction integral: (a) crack front and contour, (b) line load applied along the crack front and (c) volume V ( s ) encloses the crack front segment. R ESULTS AND DISCUSSION nitially, two dimensional elastic plane stress FE analysis is conducted on the SENT specimen with a/W=0.4, 0.5 and 0.6 and applied load 50 MPa for validation of 2D T-stress results obtained in the present study with results available in the literature [9,10]. The T-stress values are converted to bi-axial stress ( B ) form the relation:   I T a B K (5) The magnitudes of B vs . a/W is plotted in Fig.5 along with the results of Levers and Randon [9] and Paulino and Kim [10]. This figure indicates that the present results on biaxial stress obtained in the FE analysis are in excellent agreement with the similar results available in literature [9, 10]. This analysis provides the validation of the present FE computation in 2D. A series of 3D FE stress analyses have been carried out on SENT specimens with varied thickness and a/W ratio, to study the variation of T-stress along the crack-front (Effect of thickness).The obtained T-stress results are normalized with respect to applied stress ( σ ). A typical variation of normalized T-stress (T/ σ ) along the crack-front is shown in Fig.6. Figure 6 demonstrates that T-stress strongly varies with distance along the crack-front and depends on the thickness of the specimen. It is interesting to find that the magnitude of normalized T-stress is higher at the centre of the specimen than on the surface. It is observed in Fig.6 that for specimen with higher thickness, the magnitude of normalized T-stress decreases for a short distance from the specimen surface and again increases at the centre of the specimen thickness. This nature of variation of normalized T-stress could not be explained clearly at this stage, but it can be attributed to the effect I