Issue 29

S.K. Kudari et alii, Frattura ed Integrità Strutturale, 29 (2014) 419-425; DOI: 10.3221/IGF-ESIS.29.37 424 Using Eq. (5) for various ( a/W ) and applied stress ratio (  /  y ), the value of K I can be easily computed. To validate the formulation, Eq. (5), the computed values of K I using Eq. (5) for typically, a/W =0.50 for B =10mm is compared with present 3D FE results and results of Kwon and Sun [5] in Fig.12. The figure shows that the results computed by Eq. (5) are in excellent agreement with the results of Kwon and Sun [5]. The maximum percentage of error estimated in use of Eq. (5) for B =2 to 20mm, a/W =0.45 to 0.70 and  /  y =0.08 and 0.80 is 2.17%. Hence, the above proposed analytical formulation (Eq. (5)) is much capable and easy to use to compute maximum K I in a specimen by knowing only specimen a/W and applied stress ratio (  /  y ). This formulation is much improved and simple to the one given by Kwon and Sun [5], which demands 2D K I results. Using the proposed new approximate analytical Eq. (5) one can estimate the magnitudes of maximum K I at mid plane of the SENB specimen without complex numerical solutions. The proposed Eq. (5) can encourage the practicing engineers to estimate the realistic value of K I as compared to Eq. (2). Figure 10 : Variation of K I /   / y   against normalized thickness ( B/W ) for various a/W Figure 11 : Variation of average slope value of K I /   / y   vs. a/W Figure 12 : Comparison of K I estimated using Eq.(5) for typically, a/W =0.50 and B =10mm is with present 3D FE results and results of Kwon and Sun [5]. C ONCLUDING REMARKS (i) The magnitude of K I varies along the crack-front and is found to be maximum at the centre of the specimen (ii) The magnitude of K I is observed to be independent of B at the center of the specimen