Issue 39

S. K. Kudari et alii, Frattura ed Integrità Strutturale, 39 (2017) 216-225; DOI: 10.3221/IGF-ESIS.39.21 225 that T 33 /  is negative indicating some loss of out-of-plane constraint. For the specimens with similar a/W and B/W the loss of out-of-plane constraint (T 33 ) is much significant than the in plane constraint (T 11 ) (Ref. Fig.10). This infers that the major constraint loss in a CT specimen is due to the out-of-plane effects. The out-of-plane constraint loss can be corrected to some extent by providing side grooves to a CT specimen. Using the present 3D FEA results, approximate analytical formulations are proposed to evaluate the K I-max, T 11-max and T 33-max by knowing only applied stress and specimen dimensions. These formulations can be helpful in the analysis of in-plane and out-of-plane constraint issues. R EFERENCES [1] Nakamura, T., Parks, D. M., Determination of elastic T-stress along three-dimensional crack fronts using an interaction integral, Int. J. Solids Struct., 29 (1992) 1597–1611. [2] Betegon, C., Hancock, J. W., Two-parameter characterization of elastic–plastic crack tip fields, J Appl Mech., 58 (1991) 104–110. [3] Kudari, S. K., Kodancha, K. G., A new formulation for estimating maximum stress intensity factor at the mid plane of a SENB specimen: Study based on 3D FEA, Frattura ed Integrità Strutturale, 29 (2014) 419-425. [4] Nakamura, T., Parks, D. M., Three-dimensional crack front fields in a thin ductile plate, J. Mech. Phys. Solids., 38 (1990) 787–812. [5] Nevalainen, M., Dodds, R. H., Numerical investigation of 3-D constraint effects on brittle fracture in SE(B) and C(T) specimens, Int. J. Fract., 74 (1995) 131–161. [6] Leung, A. Y. T., Su, R.K.L., A numerical study of singular stress field of 3D cracks, Finite Elem. Anal. Design., 18 (1995) 389–401. [7] Kwon, S. W., Sun, C.T., Characteristics of three-dimensional stress fields in plates with a through -the-thickness crack, Int. J. Fract., 104 (2000) 291-315. [8] Jie, Q., Xin, W., Solutions of T-stresses for quarter-elliptical corner cracks in finite thickness plates subject to tension and bending, Int. J. Pres. Ves. Pip., 83 (2006) 593–606. [9] Moreira, P. M. G. P., Pastrama, S. D., Castro, P. M.. S. T., Three-dimensional stress intensity factor calibration for a stiffened cracked plate, Engng. Fract. Mech., 76 (2009) 298–2308. [10] Kodancha, K. G., Kudari, S. K., Variation of stress intensity factor and elastic T-stress along the crack-front in finite thickness plates. Frattura ed Integrità Strutturale, 8 (2009) 45-51. [11] Toshiyuki, M., Tomohiro, T., Kai, L., T-stress solutions for a semi-elliptical axial surface crack in a cylinder subjected to mode-I non-uniform stress distributions, Engng. Fract. Mech., 77 (2010) 2467-2478. [12] Toshiyuki, M., Tomohiro, T., Experimental T 33 -stress formulation of test specimen thickness effect on fracture toughness in the transition temperature region, Engng. Fract. Mech., 77 (2010) 867-877. [13] Kai, L., Toshiyuki, M., Three-dimensional T-stresses for three-point-bend specimens with large thickness Variation, Engng. Fract. Mech., 116 (2014) 197-203 [14] ABAQUS V 6.5-1. (2004) Hibbitt, Karlsson & Sorensen, Inc. [15] American Society for Testing and Materials., Standard Test Method for Measurement of Fracture Toughness, (2015) ASTM E1820-15a. [16] Moran, B., Shih, C. F., Crack tip and associated domain integrals from momentum and energy balance. Engng. Fract. Mech., 27 (1987) 615-642. [17] Gosz, M., Dolbow, J., Moran, B., Domain integral formulation for stress intensity factor computation along curved three-dimensional interface cracks. Int. J Solids Struct., 35 (1998) 1763-1783. [18] Priest, A. H., Experimental methods for fracture toughness measurement, J. Strain Analysis, 10 (1975) 225-232. [19] Fernandez, Z. D., Kalthoff, J. F., Fernandez, C. A ,Canteli, A., Grasa, J., Doblare, M. Three dimensional finite element calculations of crack-tip plastic zones and K IC specimen size requirements, ECF-15, (2005) [20] Pavel, H., Martin, S., Lubos, N., Michal, Z., Stanislav, S., Zdenek, K., Alfonso, F. C., Fracture mechanics of the three- dimensional crack front: vertex singularity versus out of plain constraint descriptions, Procedia Engng., 2 (2010) 2095- 2102.